use super::take_until_parser_matches::take_until_parser_matches;
use nom::branch::alt;
use nom::bytes::complete::escaped_transform;
use nom::bytes::complete::is_a;
use nom::bytes::complete::is_not;
use nom::bytes::complete::{tag, take_until};
use nom::character::complete::line_ending;
use nom::character::complete::multispace0;
use nom::character::complete::one_of;
use nom::character::complete::{digit1, space0, space1};
use nom::combinator::all_consuming;
use nom::combinator::map;
use nom::combinator::opt;
use nom::combinator::recognize;
use nom::combinator::value;
use nom::combinator::verify;
use nom::multi::many0;
use nom::multi::many1;
use nom::multi::separated_list1;
use nom::sequence::delimited;
use nom::sequence::preceded;
use nom::sequence::separated_pair;
use nom::sequence::terminated;
use nom::sequence::tuple;
use nom::IResult;

#[derive(Debug, PartialEq)]
pub enum DustTag<'a> {
    DTSpecial(Special),
    DTComment(Comment<'a>),
    DTLiteralStringBlock(&'a str),
    DTReference(Reference<'a>),
    DTSection(ParameterizedBlock<'a>),
    DTExists(ParameterizedBlock<'a>),
    DTNotExists(ParameterizedBlock<'a>),
    DTBlock(ParameterizedBlock<'a>),
    DTInlinePartial(ParameterizedBlock<'a>),
    DTPartial(Partial<'a>),
    DTHelperEquals(ParameterizedBlock<'a>),
    DTHelperNotEquals(ParameterizedBlock<'a>),
    DTHelperGreaterThan(ParameterizedBlock<'a>),
    DTHelperLessThan(ParameterizedBlock<'a>),
    DTHelperGreaterThanOrEquals(ParameterizedBlock<'a>),
    DTHelperLessThanOrEquals(ParameterizedBlock<'a>),
    DTHelperSep(ParameterizedBlock<'a>),
    DTHelperFirst(ParameterizedBlock<'a>),
    DTHelperLast(ParameterizedBlock<'a>),
    DTHelperSelect(ParameterizedBlock<'a>),
    DTHelperAny(ParameterizedBlock<'a>),
    DTHelperNone(ParameterizedBlock<'a>),
    DTHelperMath(ParameterizedBlock<'a>),
    DTHelperSize(ParameterizedBlock<'a>),
    DTHelperContextDump(ParameterizedBlock<'a>),
}

#[derive(Clone, Debug, PartialEq)]
pub enum Special {
    Space,
    NewLine,
    CarriageReturn,
    LeftCurlyBrace,
    RightCurlyBrace,
}

#[derive(Debug, PartialEq)]
pub enum IgnoredWhitespace<'a> {
    StartOfLine(&'a str),
}

#[derive(Debug, PartialEq)]
pub struct Comment<'a> {
    value: &'a str,
}

/// A series of keys separated by '.' to reference a variable in the context
///
/// Special case: If the path is just "." then keys will be an empty vec
#[derive(Debug, PartialEq)]
pub struct Path<'a> {
    pub keys: Vec<&'a str>,
}

#[derive(Debug, PartialEq)]
pub struct Reference<'a> {
    pub path: Path<'a>,
    pub filters: Vec<Filter>,
}

#[derive(Clone, Debug, PartialEq)]
pub enum Filter {
    HtmlEncode,
    DisableHtmlEncode,
    JavascriptStringEncode,
    EncodeUri,
    EncodeUriComponent,
    JsonStringify,
    JsonParse,
}

#[derive(Debug, PartialEq)]
pub struct Span<'a> {
    pub contents: &'a str,
}

#[derive(Debug, PartialEq)]
pub struct ParameterizedBlock<'a> {
    pub path: Path<'a>,
    pub explicit_context: Option<Path<'a>>,
    pub params: Vec<KVPair<'a>>,
    pub contents: Option<Body<'a>>,
    pub else_contents: Option<Body<'a>>,
}

#[derive(Debug, PartialEq)]
pub struct Partial<'a> {
    pub name: Vec<PartialNameElement>,
    pub explicit_context: Option<Path<'a>>,
    pub params: Vec<KVPair<'a>>,
}

#[derive(Debug, PartialEq)]
pub enum OwnedLiteral {
    LString(String),
    LPositiveInteger(u64),
    LNegativeInteger(i64),
    LFloat(f64),
    // Unlike the other OwnedLiterals, booleans cannot occur in DustJS
    // templates because true/false are not reserved
    // names. Regardless, they are needed here for type casting in the
    // renderer.
    LBoolean(bool),
}

#[derive(Debug, PartialEq)]
pub enum RValue<'a> {
    RVPath(Path<'a>),
    RVTemplate(Vec<PartialNameElement>),
    RVLiteral(OwnedLiteral),
}

#[derive(Debug, PartialEq)]
pub struct KVPair<'a> {
    pub key: &'a str,
    pub value: RValue<'a>,
}

#[derive(Debug, PartialEq)]
pub enum PartialNameElement {
    PNSpan {
        contents: String,
    },
    PNReference {
        path: Vec<String>,
        filters: Vec<Filter>,
    },
}

#[derive(Debug, PartialEq)]
pub struct Body<'a> {
    pub elements: Vec<TemplateElement<'a>>,
}

#[derive(Debug, PartialEq)]
pub struct Template<'a> {
    pub contents: Body<'a>,
}

#[derive(Debug, PartialEq)]
pub enum TemplateElement<'a> {
    TESpan(Span<'a>),
    TETag(DustTag<'a>),
    TEIgnoredWhitespace(IgnoredWhitespace<'a>),
}

impl From<TemplateElement<'_>> for PartialNameElement {
    fn from(original: TemplateElement) -> Self {
        match original {
            TemplateElement::TESpan(span) => PartialNameElement::PNSpan {
                contents: span.contents.to_owned(),
            },
            TemplateElement::TETag(DustTag::DTReference(reference)) => {
                PartialNameElement::PNReference {
                    path: reference
                        .path
                        .keys
                        .into_iter()
                        .map(|s| s.to_owned())
                        .collect(),
                    filters: reference.filters,
                }
            }
            _ => panic!("Only spans and references can be used in partial names."),
        }
    }
}

impl<'a> From<&'a PartialNameElement> for TemplateElement<'a> {
    fn from(original: &'a PartialNameElement) -> Self {
        match original {
            PartialNameElement::PNSpan { contents } => {
                TemplateElement::TESpan(Span { contents: contents })
            }
            PartialNameElement::PNReference { path, filters } => {
                TemplateElement::TETag(DustTag::DTReference(Reference {
                    path: Path {
                        keys: path.into_iter().map(|s| s.as_str()).collect(),
                    },
                    filters: filters.into_iter().map(|f| f.clone()).collect(),
                }))
            }
        }
    }
}

/// Any element significant to dust that isn't plain text
///
/// These elements are always wrapped in curly braces
fn dust_tag(i: &str) -> IResult<&str, DustTag> {
    alt((
        map(special, DustTag::DTSpecial),
        map(comment, DustTag::DTComment),
        map(literal_string_block, DustTag::DTLiteralStringBlock),
        map(reference, DustTag::DTReference),
        map(parameterized_block("{#", path), DustTag::DTSection),
        map(parameterized_block("{?", path), DustTag::DTExists),
        map(parameterized_block("{^", path), DustTag::DTNotExists),
        map(
            parameterized_block_without_else("{+", key_to_path),
            DustTag::DTBlock,
        ),
        map(
            parameterized_block_without_else("{<", key_to_path),
            DustTag::DTInlinePartial,
        ),
        partial("{>", DustTag::DTPartial),
        dust_tag_helper,
    ))(i)
}

/// Nom's alt() is limited to 21 possibilities, so I pushed this out
/// into its own parser. Otherwise there is no reason for this not to
/// be part of the dust_tag parser.
fn dust_tag_helper(i: &str) -> IResult<&str, DustTag> {
    alt((
        map(
            parameterized_block("{@", &tag_to_path("gte")),
            DustTag::DTHelperGreaterThanOrEquals,
        ),
        map(
            parameterized_block("{@", &tag_to_path("lte")),
            DustTag::DTHelperLessThanOrEquals,
        ),
        map(
            parameterized_block("{@", &tag_to_path("eq")),
            DustTag::DTHelperEquals,
        ),
        map(
            parameterized_block("{@", &tag_to_path("ne")),
            DustTag::DTHelperNotEquals,
        ),
        map(
            parameterized_block("{@", &tag_to_path("gt")),
            DustTag::DTHelperGreaterThan,
        ),
        map(
            parameterized_block("{@", &tag_to_path("lt")),
            DustTag::DTHelperLessThan,
        ),
        map(
            parameterized_block("{@", &tag_to_path("sep")),
            DustTag::DTHelperSep,
        ),
        map(
            parameterized_block("{@", &tag_to_path("first")),
            DustTag::DTHelperFirst,
        ),
        map(
            parameterized_block("{@", &tag_to_path("last")),
            DustTag::DTHelperLast,
        ),
        map(
            parameterized_block("{@", &tag_to_path("select")),
            DustTag::DTHelperSelect,
        ),
        map(
            parameterized_block("{@", &tag_to_path("any")),
            DustTag::DTHelperAny,
        ),
        map(
            parameterized_block("{@", &tag_to_path("none")),
            DustTag::DTHelperNone,
        ),
        map(
            parameterized_block("{@", &tag_to_path("math")),
            DustTag::DTHelperMath,
        ),
        map(
            parameterized_block("{@", &tag_to_path("size")),
            DustTag::DTHelperSize,
        ),
        map(
            parameterized_block("{@", &tag_to_path("contextDump")),
            DustTag::DTHelperContextDump,
        ),
    ))(i)
}

/// Special characters
fn special(i: &str) -> IResult<&str, Special> {
    delimited(
        tag("{~"),
        alt((
            value(Special::LeftCurlyBrace, tag("lb")),
            value(Special::RightCurlyBrace, tag("rb")),
            value(Special::Space, tag("s")),
            value(Special::NewLine, tag("n")),
            value(Special::CarriageReturn, tag("r")),
        )),
        tag("}"),
    )(i)
}

/// Part of a dust template that does not get rendered
fn comment(i: &str) -> IResult<&str, Comment> {
    map(delimited(tag("{!"), take_until("!}"), tag("!}")), |body| {
        Comment { value: body }
    })(i)
}

/// A single element of a path
fn key(i: &str) -> IResult<&str, &str> {
    recognize(tuple((
        one_of("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$"),
        opt(is_a(
            "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$0123456789-",
        )),
    )))(i)
}

/// A series of keys separated by '.' to reference a variable in the context
fn path(i: &str) -> IResult<&str, Path> {
    alt((
        map(separated_list1(tag("."), key), |body| Path { keys: body }),
        map(
            tuple((tag("."), separated_list1(tag("."), key))),
            |(dot, mut body)| {
                body.insert(0, dot);
                Path { keys: body }
            },
        ),
        map(tag("."), |dot| Path { keys: vec![dot] }),
    ))(i)
}

fn tag_to_path<'a>(text: &'static str) -> impl Fn(&'a str) -> IResult<&str, Path<'a>> {
    move |i: &'a str| map(tag(text), |t| Path { keys: vec![t] })(i)
}

fn key_to_path<'a>(i: &'a str) -> IResult<&str, Path<'a>> {
    map(key, |k| Path { keys: vec![k] })(i)
}

/// Just digits, no signs or decimals
fn postitive_integer_literal(i: &str) -> IResult<&str, u64> {
    map(
        verify(
            map(
                recognize(tuple((opt(tag("+")), digit1))),
                |number_string: &str| number_string.parse::<u64>(),
            ),
            |parse_result| parse_result.is_ok(),
        ),
        |parsed_number| parsed_number.unwrap(),
    )(i)
}

/// No decimals, just the sign and digits
fn negative_integer_literal(i: &str) -> IResult<&str, i64> {
    map(
        verify(
            map(
                recognize(tuple((tag("-"), digit1))),
                |number_string: &str| number_string.parse::<i64>(),
            ),
            |parse_result| parse_result.is_ok(),
        ),
        |parsed_number| parsed_number.unwrap(),
    )(i)
}

/// A non-scientific notation float (sign, digits, decimal, and more digits)
fn float_literal(i: &str) -> IResult<&str, f64> {
    map(
        verify(
            map(
                recognize(tuple((opt(one_of("+-")), digit1, tag("."), digit1))),
                |number_string: &str| number_string.parse::<f64>(),
            ),
            |parse_result| parse_result.is_ok(),
        ),
        |parsed_number| parsed_number.unwrap(),
    )(i)
}

fn template_string_rvalue(i: &str) -> IResult<&str, Vec<PartialNameElement>> {
    let (i, template_string) = verify(quoted_string, |s: &String| {
        partial_quoted_tag(s.as_str()).is_ok()
    })(i)?;

    let (_remaining, parsed_template_elements) = partial_quoted_tag(template_string.as_str())
        .expect("A successful parse was verified earlier with a call to verify()");
    let converted_template_elements = parsed_template_elements
        .into_iter()
        .map(|e| e.into())
        .collect();
    Ok((i, converted_template_elements))
}

/// Either a literal or a path to a value
fn rvalue(i: &str) -> IResult<&str, RValue> {
    alt((
        map(path, RValue::RVPath),
        map(template_string_rvalue, RValue::RVTemplate),
        map(float_literal, |num| {
            RValue::RVLiteral(OwnedLiteral::LFloat(num))
        }),
        map(negative_integer_literal, |num| {
            RValue::RVLiteral(OwnedLiteral::LNegativeInteger(num))
        }),
        map(postitive_integer_literal, |num| {
            RValue::RVLiteral(OwnedLiteral::LPositiveInteger(num))
        }),
    ))(i)
}

/// Parameters for a partial
fn key_value_pair(i: &str) -> IResult<&str, KVPair> {
    map(separated_pair(key, tag("="), rvalue), |(k, v)| KVPair {
        key: k,
        value: v,
    })(i)
}

/// Display a value from the context
fn reference(i: &str) -> IResult<&str, Reference> {
    let (remaining, (p, filters)) = delimited(
        tag("{"),
        tuple((path, many0(filter))),
        preceded(space0, tag("}")),
    )(i)?;
    Ok((
        remaining,
        Reference {
            path: p,
            filters: filters,
        },
    ))
}

fn parameterized_block<'a, F>(
    open_matcher: &'static str,
    name_matcher: F,
) -> impl FnMut(&'a str) -> IResult<&'a str, ParameterizedBlock<'a>>
where
    F: Copy + Fn(&'a str) -> IResult<&'a str, Path<'a>>,
{
    alt((
        parameterized_block_with_body(open_matcher, name_matcher),
        parameterized_self_closing_block(open_matcher, name_matcher),
    ))
}

fn parameterized_block_without_else<'a, F>(
    open_matcher: &'static str,
    name_matcher: F,
) -> impl FnMut(&'a str) -> IResult<&'a str, ParameterizedBlock<'a>>
where
    F: Copy + Fn(&'a str) -> IResult<&'a str, Path<'a>>,
{
    alt((
        parameterized_block_with_body_without_else(open_matcher, name_matcher),
        parameterized_self_closing_block(open_matcher, name_matcher),
    ))
}

fn parameterized_block_with_body<'a, F>(
    open_matcher: &'static str,
    name_matcher: F,
) -> impl Fn(&'a str) -> IResult<&'a str, ParameterizedBlock<'a>>
where
    F: Copy + Fn(&'a str) -> IResult<&'a str, Path<'a>>,
{
    move |i: &'a str| {
        let (i, (opening_name, maybe_explicit_context, params, inner, maybe_else, _closing_name)) =
            verify(
                tuple((
                    preceded(tag(open_matcher), name_matcher),
                    opt(preceded(tag(":"), path)),
                    terminated(
                        opt(preceded(space1, separated_list1(space1, key_value_pair))),
                        preceded(space0, tag("}")),
                    ),
                    opt(body),
                    opt(preceded(tag("{:else}"), opt(body))),
                    delimited(tag("{/"), name_matcher, tag("}")),
                )),
                |(open, _maybe_explicit, _params, _inn, _maybe_else, close)| open == close,
            )(i)?;

        Ok((
            i,
            ParameterizedBlock {
                path: opening_name,
                explicit_context: maybe_explicit_context,
                params: params.unwrap_or(Vec::new()),
                contents: inner,
                else_contents: maybe_else.flatten(),
            },
        ))
    }
}

fn parameterized_block_with_body_without_else<'a, F>(
    open_matcher: &'static str,
    name_matcher: F,
) -> impl Fn(&'a str) -> IResult<&'a str, ParameterizedBlock<'a>>
where
    F: Copy + Fn(&'a str) -> IResult<&'a str, Path<'a>>,
{
    move |i: &'a str| {
        let (i, (opening_name, maybe_explicit_context, params, inner, _closing_name)) =
            verify(
                tuple((
                    preceded(tag(open_matcher), name_matcher),
                    opt(preceded(tag(":"), path)),
                    terminated(
                        opt(preceded(space1, separated_list1(space1, key_value_pair))),
                        preceded(space0, tag("}")),
                    ),
                    opt(body),
                    delimited(tag("{/"), name_matcher, tag("}")),
                )),
                |(open, _maybe_explicit, _params, _inn, close)| open == close,
            )(i)?;

        Ok((
            i,
            ParameterizedBlock {
                path: opening_name,
                explicit_context: maybe_explicit_context,
                params: params.unwrap_or(Vec::new()),
                contents: inner,
                else_contents: None,
            },
        ))
    }
}

fn parameterized_self_closing_block<'a, F>(
    open_matcher: &'static str,
    name_matcher: F,
) -> impl Fn(&'a str) -> IResult<&'a str, ParameterizedBlock<'a>>
where
    F: Copy + Fn(&'a str) -> IResult<&'a str, Path<'a>>,
{
    move |i: &'a str| {
        let (i, (opening_name, maybe_explicit_context, params)) = delimited(
            tag(open_matcher),
            tuple((
                name_matcher,
                opt(preceded(tag(":"), path)),
                opt(preceded(space1, separated_list1(space1, key_value_pair))),
            )),
            preceded(space0, tag("/}")),
        )(i)?;

        Ok((
            i,
            ParameterizedBlock {
                path: opening_name,
                explicit_context: maybe_explicit_context,
                params: params.unwrap_or(Vec::new()),
                contents: None,
                else_contents: None,
            },
        ))
    }
}

fn partial_with_plain_tag<'a>(
    open_matcher: &'static str,
) -> impl Fn(&'a str) -> IResult<&'a str, Partial<'a>> {
    move |i: &'a str| {
        let (i, (name, maybe_explicit_context, params)) = delimited(
            tag(open_matcher),
            tuple((
                key,
                opt(preceded(tag(":"), path)),
                opt(preceded(space1, separated_list1(space1, key_value_pair))),
            )),
            preceded(space0, tag("/}")),
        )(i)?;

        Ok((
            i,
            Partial {
                name: vec![PartialNameElement::PNSpan {
                    contents: name.to_owned(),
                }],
                explicit_context: maybe_explicit_context,
                params: params.unwrap_or(Vec::new()),
            },
        ))
    }
}

fn partial_quoted_tag(i: &str) -> IResult<&str, Vec<TemplateElement>> {
    all_consuming(many1(alt((
        map(span, TemplateElement::TESpan),
        map(map(reference, DustTag::DTReference), TemplateElement::TETag),
    ))))(i)
}

fn partial_with_quoted_tag<'a>(
    open_matcher: &'static str,
) -> impl Fn(&'a str) -> IResult<&'a str, Partial<'a>> {
    move |i: &'a str| {
        let (i, (name, maybe_explicit_context, params)) = delimited(
            tag(open_matcher),
            tuple((
                template_string_rvalue,
                opt(preceded(tag(":"), path)),
                opt(preceded(space1, separated_list1(space1, key_value_pair))),
            )),
            preceded(space0, tag("/}")),
        )(i)?;

        Ok((
            i,
            Partial {
                name: name,
                explicit_context: maybe_explicit_context,
                params: params.unwrap_or(Vec::new()),
            },
        ))
    }
}

fn partial<'a, F>(
    open_matcher: &'static str,
    constructor: F,
) -> impl Fn(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Fn(Partial<'a>) -> DustTag<'a>,
{
    let plain = partial_with_plain_tag(open_matcher);
    let quoted = partial_with_quoted_tag(open_matcher);
    move |i: &'a str| map(alt((&plain, &quoted)), &constructor)(i)
}

fn filter(i: &str) -> IResult<&str, Filter> {
    preceded(
        tag("|"),
        alt((
            value(Filter::JsonStringify, tag("js")),
            value(Filter::JsonParse, tag("jp")),
            value(Filter::EncodeUriComponent, tag("uc")),
            value(Filter::HtmlEncode, tag("h")),
            value(Filter::DisableHtmlEncode, tag("s")),
            value(Filter::JavascriptStringEncode, tag("j")),
            value(Filter::EncodeUri, tag("u")),
        )),
    )(i)
}

/// Whitespace at the beginning of lines is ignored so we are matching
/// a newline character followed by as much contiguous whitespace as
/// possible, all of which will be thrown away by other parsers.
fn ignore_new_line_leading_whitespace(i: &str) -> IResult<&str, IgnoredWhitespace> {
    map(
        recognize(tuple((line_ending, multispace0))),
        IgnoredWhitespace::StartOfLine,
    )(i)
}

fn literal_string_block(i: &str) -> IResult<&str, &str> {
    delimited(tag("{`"), take_until("`}"), tag("`}"))(i)
}

/// Any text that is not a Dust element or ignored whitespace
fn span(i: &str) -> IResult<&str, Span> {
    let (remaining, line) = verify(
        take_until_parser_matches(alt((
            tag("{"),
            line_ending,
            recognize(all_consuming(eof_whitespace)),
        ))),
        |s: &str| s.len() > 0,
    )(i)?;
    Ok((remaining, Span { contents: line }))
}

fn body(i: &str) -> IResult<&str, Body> {
    let (remaining, template_elements) = many1(alt((
        map(
            ignore_new_line_leading_whitespace,
            TemplateElement::TEIgnoredWhitespace,
        ),
        map(span, TemplateElement::TESpan),
        map(dust_tag, TemplateElement::TETag),
    )))(i)?;
    Ok((
        remaining,
        Body {
            elements: template_elements,
        },
    ))
}

pub fn template(i: &str) -> IResult<&str, Template> {
    // DustJS ignores all preceding whitespace (tabs, newlines, spaces) but only ignores trailing newlines
    let (remaining, contents) = all_consuming(delimited(multispace0, body, eof_whitespace))(i)?;
    Ok((remaining, Template { contents: contents }))
}

fn quoted_string(i: &str) -> IResult<&str, String> {
    delimited(
        tag(r#"""#),
        escaped_transform(is_not(r#"\""#), '\\', one_of(r#"\""#)),
        tag(r#"""#),
    )(i)
}

fn eof_whitespace(i: &str) -> IResult<&str, Vec<&str>> {
    many0(line_ending)(i)
}

#[cfg(test)]
mod tests {
    use super::*;
    use nom::bytes::complete::is_a;
    use nom::error::ErrorKind;
    use nom::Err::Error;

    #[test]
    fn test_direct_literal() {
        assert_eq!(super::float_literal("-17.4"), Ok(("", -17.4)));
        assert_eq!(super::float_literal("17.1"), Ok(("", 17.1)));
        assert_eq!(super::negative_integer_literal("-12"), Ok(("", -12)));
    }

    #[test]
    fn test_reference() {
        assert_eq!(
            super::reference("{foo.bar.baz|js|s}"),
            Ok((
                "",
                Reference {
                    path: Path {
                        keys: vec!["foo", "bar", "baz"]
                    },
                    filters: vec![Filter::JsonStringify, Filter::DisableHtmlEncode],
                }
            ))
        );
    }

    #[test]
    fn test_reference_to_variable() {
        assert_eq!(
            super::reference("{$idx}"),
            Ok((
                "",
                Reference {
                    path: Path { keys: vec!["$idx"] },
                    filters: Vec::new(),
                }
            ))
        );
    }

    #[test]
    fn test_path() {
        assert_eq!(
            is_a::<_, _, (_, ErrorKind)>("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ_$")(
                "foo"
            ),
            Ok(("", "foo"))
        );

        assert_eq!(
            super::path("foo.bar.baz"),
            Ok((
                "",
                Path {
                    keys: vec!["foo", "bar", "baz"]
                }
            ))
        );
    }

    #[test]
    fn test_special() {
        assert_eq!(super::special("{~s}"), Ok(("", Special::Space)));
        assert_eq!(super::special("{~n}"), Ok(("", Special::NewLine)));
        assert_eq!(super::special("{~r}"), Ok(("", Special::CarriageReturn)));
        assert_eq!(super::special("{~lb}"), Ok(("", Special::LeftCurlyBrace)));
        assert_eq!(super::special("{~rb}"), Ok(("", Special::RightCurlyBrace)));
        assert_eq!(
            super::special("{~zzz}"),
            Err(Error(nom::error::Error {
                input: "zzz}",
                code: ErrorKind::Tag
            }))
        );
    }

    #[test]
    fn test_comment() {
        assert_eq!(
            super::comment("{! yo dawg} this is a comment !}"),
            Ok((
                "",
                Comment {
                    value: " yo dawg} this is a comment "
                }
            ))
        );
        assert_eq!(
            super::special("{! this is a comment without a close"),
            Err(Error(nom::error::Error {
                input: "{! this is a comment without a close",
                code: ErrorKind::Tag
            }))
        );
    }

    #[test]
    fn test_span_end_of_line() {
        assert_eq!(
            super::ignore_new_line_leading_whitespace("\n  \t  \n\nfoo"),
            Ok(("foo", IgnoredWhitespace::StartOfLine("\n  \t  \n\n")))
        );
    }

    #[test]
    fn test_span() {
        assert_eq!(
            super::span("this is just some text"),
            Ok((
                "",
                Span {
                    contents: "this is just some text"
                }
            ))
        );
        assert_eq!(
            super::span("this is just some text {~lb}"),
            Ok((
                "{~lb}",
                Span {
                    contents: "this is just some text "
                }
            ))
        );
        assert_eq!(
            super::span("{~lb}"),
            Err(Error(nom::error::Error {
                input: "{~lb}",
                code: ErrorKind::Verify
            }))
        );
        assert_eq!(
            super::body("this is       \t   \n\n    \t \n   \t  multiline text\n     {foo}"),
            Ok((
                "",
                Body {
                    elements: vec![
                        TemplateElement::TESpan(Span {
                            contents: "this is       \t   "
                        }),
                        TemplateElement::TEIgnoredWhitespace(IgnoredWhitespace::StartOfLine(
                            "\n\n    \t \n   \t  "
                        )),
                        TemplateElement::TESpan(Span {
                            contents: "multiline text"
                        }),
                        TemplateElement::TEIgnoredWhitespace(IgnoredWhitespace::StartOfLine(
                            "\n     "
                        )),
                        TemplateElement::TETag(DustTag::DTReference(Reference {
                            path: Path { keys: vec!["foo"] },
                            filters: vec![]
                        }))
                    ]
                }
            ))
        );
        assert_eq!(
            super::body("\n    leading whitespace"),
            Ok((
                "",
                Body {
                    elements: vec![
                        TemplateElement::TEIgnoredWhitespace(IgnoredWhitespace::StartOfLine(
                            "\n    "
                        )),
                        TemplateElement::TESpan(Span {
                            contents: "leading whitespace"
                        }),
                    ]
                }
            ))
        );
    }

    #[test]
    fn test_section_mismatched_paths() {
        assert_eq!(
            super::dust_tag("{#foo.bar}{/baz}"),
            Err(Error(nom::error::Error {
                input: "{#foo.bar}{/baz}",
                code: ErrorKind::Tag
            }))
        );
    }

    #[test]
    fn test_empty_section() {
        assert_eq!(
            super::dust_tag("{#foo.bar}{/foo.bar}"),
            Ok((
                "",
                DustTag::DTSection(ParameterizedBlock {
                    path: Path {
                        keys: vec!["foo", "bar"]
                    },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: None,
                    else_contents: None,
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_section() {
        assert_eq!(
            super::dust_tag("{#foo.bar/}"),
            Ok((
                "",
                DustTag::DTSection(ParameterizedBlock {
                    path: Path {
                        keys: vec!["foo", "bar"]
                    },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: None,
                    else_contents: None,
                })
            ))
        );
    }

    #[test]
    fn test_section_with_body() {
        assert_eq!(
            super::dust_tag("{#foo.bar}hello {name}{/foo.bar}"),
            Ok((
                "",
                DustTag::DTSection(ParameterizedBlock {
                    path: Path {
                        keys: vec!["foo", "bar"]
                    },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span { contents: "hello " }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                    else_contents: None,
                })
            ))
        );
    }

    #[test]
    fn test_section_with_else_body() {
        assert_eq!(
            super::dust_tag("{#greeting}hello {name}{:else}goodbye {name}{/greeting}"),
            Ok((
                "",
                DustTag::DTSection(ParameterizedBlock {
                    path: Path {
                        keys: vec!["greeting"]
                    },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span { contents: "hello " }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                    else_contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: "goodbye "
                            }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                })
            ))
        );
    }

    #[test]
    fn test_empty_section_with_explicit_context() {
        assert_eq!(
            super::dust_tag("{#foo.bar:baz.ipsum}{/foo.bar}"),
            Ok((
                "",
                DustTag::DTSection(ParameterizedBlock {
                    path: Path {
                        keys: vec!["foo", "bar"]
                    },
                    explicit_context: Some(Path {
                        keys: vec!["baz", "ipsum"]
                    }),
                    params: Vec::new(),
                    contents: None,
                    else_contents: None,
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_section_with_explicit_context() {
        assert_eq!(
            super::dust_tag("{#foo.bar:$idx/}"),
            Ok((
                "",
                DustTag::DTSection(ParameterizedBlock {
                    path: Path {
                        keys: vec!["foo", "bar"]
                    },
                    explicit_context: Some(Path { keys: vec!["$idx"] }),
                    params: Vec::new(),
                    contents: None,
                    else_contents: None,
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_block() {
        assert_eq!(
            super::dust_tag("{+foo/}"),
            Ok((
                "",
                DustTag::DTBlock(ParameterizedBlock {
                    path: Path { keys: vec!["foo"] },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: None,
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_block() {
        assert_eq!(
            super::dust_tag("{+foo}hello {name}{/foo}"),
            Ok((
                "",
                DustTag::DTBlock(ParameterizedBlock {
                    path: Path { keys: vec!["foo"] },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span { contents: "hello " }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_block_with_explicit_context() {
        assert_eq!(
            super::dust_tag("{+foo:bar.baz/}"),
            Ok((
                "",
                DustTag::DTBlock(ParameterizedBlock {
                    path: Path { keys: vec!["foo"] },
                    explicit_context: Some(Path {
                        keys: vec!["bar", "baz"]
                    }),
                    params: Vec::new(),
                    contents: None,
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_block_with_explicit_context() {
        assert_eq!(
            super::dust_tag("{+foo:bar.baz}hello {name}{/foo}"),
            Ok((
                "",
                DustTag::DTBlock(ParameterizedBlock {
                    path: Path { keys: vec!["foo"] },
                    explicit_context: Some(Path {
                        keys: vec!["bar", "baz"]
                    }),
                    params: Vec::new(),
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span { contents: "hello " }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_inline_partial() {
        assert_eq!(
            super::dust_tag("{<foo/}"),
            Ok((
                "",
                DustTag::DTInlinePartial(ParameterizedBlock {
                    path: Path { keys: vec!["foo"] },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: None,
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_inline_partial() {
        assert_eq!(
            super::dust_tag("{<foo}hello {name}{/foo}"),
            Ok((
                "",
                DustTag::DTInlinePartial(ParameterizedBlock {
                    path: Path { keys: vec!["foo"] },
                    explicit_context: None,
                    params: Vec::new(),
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span { contents: "hello " }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_quoted_string() {
        assert_eq!(
            quoted_string(r#""foo\"bar\\baz""#),
            Ok(("", r#"foo"bar\baz"#.to_owned()))
        );
    }

    #[test]
    fn test_unquoted_partial() {
        assert_eq!(
            dust_tag(r#"{>foo bar=baz animal="cat"/}"#),
            Ok((
                "",
                DustTag::DTPartial(Partial {
                    name: vec![PartialNameElement::PNSpan {
                        contents: "foo".to_owned()
                    },],
                    explicit_context: None,
                    params: vec![
                        KVPair {
                            key: "bar",
                            value: RValue::RVPath(Path { keys: vec!["baz"] })
                        },
                        KVPair {
                            key: "animal",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ]
                })
            ))
        );
    }

    #[test]
    fn test_quoted_partial() {
        assert_eq!(
            dust_tag(r#"{>"template name * with * special \" characters" bar=baz animal="cat"/}"#),
            Ok((
                "",
                DustTag::DTPartial(Partial {
                    name: vec![PartialNameElement::PNSpan {
                        contents: r#"template name * with * special " characters"#.to_owned()
                    },],
                    explicit_context: None,
                    params: vec![
                        KVPair {
                            key: "bar",
                            value: RValue::RVPath(Path { keys: vec!["baz"] })
                        },
                        KVPair {
                            key: "animal",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ]
                })
            ))
        );
    }

    #[test]
    fn test_dynamic_partial() {
        assert_eq!(
            dust_tag(r#"{>"dynamic{ref}template" bar=baz animal="cat"/}"#),
            Ok((
                "",
                DustTag::DTPartial(Partial {
                    name: vec![
                        PartialNameElement::PNSpan {
                            contents: "dynamic".to_owned()
                        },
                        PartialNameElement::PNReference {
                            path: vec!["ref".to_owned()],
                            filters: Vec::new()
                        },
                        PartialNameElement::PNSpan {
                            contents: "template".to_owned()
                        }
                    ],
                    explicit_context: None,
                    params: vec![
                        KVPair {
                            key: "bar",
                            value: RValue::RVPath(Path { keys: vec!["baz"] })
                        },
                        KVPair {
                            key: "animal",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ]
                })
            ))
        );
    }

    #[test]
    fn test_unquoted_partial_with_explicit_context() {
        assert_eq!(
            dust_tag(r#"{>foo:foo.bar bar=baz animal="cat"/}"#),
            Ok((
                "",
                DustTag::DTPartial(Partial {
                    name: vec![PartialNameElement::PNSpan {
                        contents: "foo".to_owned()
                    },],
                    explicit_context: Some(Path {
                        keys: vec!["foo", "bar"]
                    }),
                    params: vec![
                        KVPair {
                            key: "bar",
                            value: RValue::RVPath(Path { keys: vec!["baz"] })
                        },
                        KVPair {
                            key: "animal",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ]
                })
            ))
        );
    }

    #[test]
    fn test_quoted_partial_with_explicit_context() {
        assert_eq!(
            dust_tag(
                r#"{>"template name * with * special \" characters":foo.bar bar=baz animal="cat"/}"#
            ),
            Ok((
                "",
                DustTag::DTPartial(Partial {
                    name: vec![PartialNameElement::PNSpan {
                        contents: r#"template name * with * special " characters"#.to_owned()
                    },],
                    explicit_context: Some(Path {
                        keys: vec!["foo", "bar"]
                    }),
                    params: vec![
                        KVPair {
                            key: "bar",
                            value: RValue::RVPath(Path { keys: vec!["baz"] })
                        },
                        KVPair {
                            key: "animal",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ]
                })
            ))
        );
    }

    #[test]
    fn test_literals() {
        assert_eq!(
            dust_tag(r#"{>foo a="foo" b=179 c=17.1 d=-12 e=-17.4/}"#),
            Ok((
                "",
                DustTag::DTPartial(Partial {
                    name: vec![PartialNameElement::PNSpan {
                        contents: "foo".to_owned()
                    },],
                    explicit_context: None,
                    params: vec![
                        KVPair {
                            key: "a",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "foo".to_owned()
                            }])
                        },
                        KVPair {
                            key: "b",
                            value: RValue::RVLiteral(OwnedLiteral::LPositiveInteger(179))
                        },
                        KVPair {
                            key: "c",
                            value: RValue::RVLiteral(OwnedLiteral::LFloat(17.1))
                        },
                        KVPair {
                            key: "d",
                            value: RValue::RVLiteral(OwnedLiteral::LNegativeInteger(-12))
                        },
                        KVPair {
                            key: "e",
                            value: RValue::RVLiteral(OwnedLiteral::LFloat(-17.4))
                        }
                    ]
                })
            ))
        );
    }

    #[test]
    fn test_helper() {
        assert_eq!(
            dust_tag(r#"{@eq key=name value="cat"}Pet the {name}!{/eq}"#),
            Ok((
                "",
                DustTag::DTHelperEquals(ParameterizedBlock {
                    path: Path { keys: vec!["eq"] },
                    explicit_context: None,
                    params: vec![
                        KVPair {
                            key: "key",
                            value: RValue::RVPath(Path { keys: vec!["name"] })
                        },
                        KVPair {
                            key: "value",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ],
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: "Pet the "
                            }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            })),
                            TemplateElement::TESpan(Span { contents: "!" })
                        ]
                    }),
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_helper() {
        assert_eq!(
            dust_tag(r#"{@eq key=name value="cat"/}"#),
            Ok((
                "",
                DustTag::DTHelperEquals(ParameterizedBlock {
                    path: Path { keys: vec!["eq"] },
                    explicit_context: None,
                    params: vec![
                        KVPair {
                            key: "key",
                            value: RValue::RVPath(Path { keys: vec!["name"] })
                        },
                        KVPair {
                            key: "value",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ],
                    contents: None,
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_helper_with_explicit_context() {
        assert_eq!(
            dust_tag(r#"{@eq:foo.bar key=name value="cat"}Pet the {name}!{/eq}"#),
            Ok((
                "",
                DustTag::DTHelperEquals(ParameterizedBlock {
                    path: Path { keys: vec!["eq"] },
                    explicit_context: Some(Path {
                        keys: vec!["foo", "bar"]
                    }),
                    params: vec![
                        KVPair {
                            key: "key",
                            value: RValue::RVPath(Path { keys: vec!["name"] })
                        },
                        KVPair {
                            key: "value",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ],
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: "Pet the "
                            }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            })),
                            TemplateElement::TESpan(Span { contents: "!" })
                        ]
                    }),
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_helper_with_explicit_context() {
        assert_eq!(
            dust_tag(r#"{@eq:foo.bar key=name value="cat"/}"#),
            Ok((
                "",
                DustTag::DTHelperEquals(ParameterizedBlock {
                    path: Path { keys: vec!["eq"] },
                    explicit_context: Some(Path {
                        keys: vec!["foo", "bar"]
                    }),
                    params: vec![
                        KVPair {
                            key: "key",
                            value: RValue::RVPath(Path { keys: vec!["name"] })
                        },
                        KVPair {
                            key: "value",
                            value: RValue::RVTemplate(vec![PartialNameElement::PNSpan {
                                contents: "cat".to_owned()
                            }])
                        }
                    ],
                    contents: None,
                    else_contents: None
                })
            ))
        );
    }

    #[test]
    fn test_full_document_new_line_equality() {
        assert_eq!(
            super::template(
                "- simple -{~n}
{#names}{.}{/names}
{~n}- new lines -{~n}
{#names}
{.}
{/names}"
            ),
            Ok::<_, nom::Err<nom::error::Error<&str>>>((
                "",
                Template {
                    contents: Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: "- simple -"
                            }),
                            TemplateElement::TETag(DustTag::DTSpecial(Special::NewLine)),
                            TemplateElement::TEIgnoredWhitespace(IgnoredWhitespace::StartOfLine(
                                "\n"
                            )),
                            TemplateElement::TETag(DustTag::DTSection(ParameterizedBlock {
                                path: Path {
                                    keys: vec!["names"]
                                },
                                explicit_context: None,
                                params: Vec::new(),
                                contents: Some(Body {
                                    elements: vec![TemplateElement::TETag(DustTag::DTReference(
                                        Reference {
                                            path: Path { keys: vec!["."] },
                                            filters: vec![]
                                        }
                                    ))]
                                }),
                                else_contents: None,
                            })),
                            TemplateElement::TEIgnoredWhitespace(IgnoredWhitespace::StartOfLine(
                                "\n"
                            )),
                            TemplateElement::TETag(DustTag::DTSpecial(Special::NewLine)),
                            TemplateElement::TESpan(Span {
                                contents: "- new lines -"
                            }),
                            TemplateElement::TETag(DustTag::DTSpecial(Special::NewLine)),
                            TemplateElement::TEIgnoredWhitespace(IgnoredWhitespace::StartOfLine(
                                "\n"
                            )),
                            TemplateElement::TETag(DustTag::DTSection(ParameterizedBlock {
                                path: Path {
                                    keys: vec!["names"]
                                },
                                explicit_context: None,
                                params: Vec::new(),
                                contents: Some(Body {
                                    elements: vec![
                                        TemplateElement::TEIgnoredWhitespace(
                                            IgnoredWhitespace::StartOfLine("\n")
                                        ),
                                        TemplateElement::TETag(DustTag::DTReference(Reference {
                                            path: Path { keys: vec!["."] },
                                            filters: vec![]
                                        })),
                                        TemplateElement::TEIgnoredWhitespace(
                                            IgnoredWhitespace::StartOfLine("\n")
                                        )
                                    ]
                                }),
                                else_contents: None,
                            })),
                        ]
                    }
                }
            ))
        );
    }

    #[test]
    fn test_full_document_parameterized_partial() {
        assert_eq!(
            super::template(
                r#"{#level3.level4}{>partialtwo v1="b" v2="b" v3="b" v4="b" v5="b" /}{/level3.level4}"#
            ),
            Ok::<_, nom::Err<nom::error::Error<&str>>>((
                "",
                Template {
                    contents: Body {
                        elements: vec![TemplateElement::TETag(DustTag::DTSection(
                            ParameterizedBlock {
                                path: Path {
                                    keys: vec!["level3", "level4"]
                                },
                                explicit_context: None,
                                params: Vec::new(),
                                contents: Some(Body {
                                    elements: vec![TemplateElement::TETag(DustTag::DTPartial(
                                        Partial {
                                            name: vec![PartialNameElement::PNSpan {
                                                contents: "partialtwo".to_owned()
                                            },],
                                            explicit_context: None,
                                            params: vec![
                                                KVPair {
                                                    key: "v1",
                                                    value: RValue::RVTemplate(vec![
                                                        PartialNameElement::PNSpan {
                                                            contents: "b".to_owned()
                                                        }
                                                    ])
                                                },
                                                KVPair {
                                                    key: "v2",
                                                    value: RValue::RVTemplate(vec![
                                                        PartialNameElement::PNSpan {
                                                            contents: "b".to_owned()
                                                        }
                                                    ])
                                                },
                                                KVPair {
                                                    key: "v3",
                                                    value: RValue::RVTemplate(vec![
                                                        PartialNameElement::PNSpan {
                                                            contents: "b".to_owned()
                                                        }
                                                    ])
                                                },
                                                KVPair {
                                                    key: "v4",
                                                    value: RValue::RVTemplate(vec![
                                                        PartialNameElement::PNSpan {
                                                            contents: "b".to_owned()
                                                        }
                                                    ])
                                                },
                                                KVPair {
                                                    key: "v5",
                                                    value: RValue::RVTemplate(vec![
                                                        PartialNameElement::PNSpan {
                                                            contents: "b".to_owned()
                                                        }
                                                    ])
                                                }
                                            ]
                                        }
                                    ))]
                                }),
                                else_contents: None
                            }
                        ))]
                    }
                }
            ))
        );
    }
}