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;
use nom::bytes::complete::take_until;
use nom::bytes::complete::take_until_parser_matches;
use nom::character::complete::line_ending;
use nom::character::complete::multispace0;
use nom::character::complete::one_of;
use nom::character::complete::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(Clone, Debug, PartialEq)]
pub enum DustTag<'a> {
    DTSpecial(Special),
    DTComment(Comment<'a>),
    DTReference(Reference<'a>),
    DTSection(Container<'a>),
    DTExists(Container<'a>),
    DTNotExists(Container<'a>),
    DTBlock(NamedBlock<'a>),
    DTInlinePartial(NamedBlock<'a>),
    DTPartial(Partial<'a>),
    DTHelperEquals(ParameterizedBlock<'a>),
    DTHelperNotEquals(ParameterizedBlock<'a>),
    DTHelperGreaterThan(ParameterizedBlock<'a>),
    DTHelperLessThan(ParameterizedBlock<'a>),
    DTHelperGreaterThenOrEquals(ParameterizedBlock<'a>),
    DTHelperLessThenOrEquals(ParameterizedBlock<'a>),
}

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

#[derive(Clone, 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(Clone, Debug, PartialEq)]
pub struct Path<'a> {
    pub keys: Vec<&'a str>,
}

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

#[derive(Clone, Debug, PartialEq)]
pub struct Container<'a> {
    pub path: Path<'a>,
    pub contents: Option<Body<'a>>,
    pub else_contents: Option<Body<'a>>,
}

#[derive(Clone, Debug, PartialEq)]
pub struct NamedBlock<'a> {
    name: &'a str,
    contents: Option<Body<'a>>,
}

#[derive(Clone, Debug, PartialEq)]
pub struct ParameterizedBlock<'a> {
    name: &'a str,
    params: Vec<KVPair<'a>>,
    contents: Option<Body<'a>>,
    else_contents: Option<Body<'a>>,
}

#[derive(Clone, Debug, PartialEq)]
pub struct Partial<'a> {
    name: String,
    params: Vec<KVPair<'a>>,
}

#[derive(Clone, Debug, PartialEq)]
enum RValue<'a> {
    RVPath(Path<'a>),
    RVString(String),
}

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

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

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

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

/// 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(reference, DustTag::DTReference),
        conditional("{#", DustTag::DTSection),
        conditional("{?", DustTag::DTExists),
        conditional("{^", DustTag::DTNotExists),
        named_block("{+", DustTag::DTBlock),
        named_block("{<", DustTag::DTInlinePartial),
        partial("{>", DustTag::DTPartial),
        parameterized_block("{@", "gte", DustTag::DTHelperGreaterThenOrEquals),
        parameterized_block("{@", "lte", DustTag::DTHelperLessThenOrEquals),
        parameterized_block("{@", "eq", DustTag::DTHelperEquals),
        parameterized_block("{@", "ne", DustTag::DTHelperNotEquals),
        parameterized_block("{@", "gt", DustTag::DTHelperGreaterThan),
        parameterized_block("{@", "lt", DustTag::DTHelperLessThan),
    ))(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 }),
        value(Path { keys: Vec::new() }, tag(".")),
    ))(i)
}

/// Either a literal or a path to a value
fn rvalue(i: &str) -> IResult<&str, RValue> {
    alt((
        map(path, RValue::RVPath),
        map(quoted_string, RValue::RVString),
    ))(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))), tag("}"))(i)?;
    Ok((
        remaining,
        Reference {
            path: p,
            filters: filters,
        },
    ))
}

fn conditional<'a, F>(
    open_matcher: &'static str,
    constructor: F,
) -> impl FnMut(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Copy + Fn(Container<'a>) -> DustTag<'a>,
{
    alt((
        conditional_with_body(open_matcher, constructor),
        self_closing_conditional(open_matcher, constructor),
    ))
}

fn conditional_with_body<'a, F>(
    open_matcher: &'static str,
    constructor: F,
) -> impl Fn(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Fn(Container<'a>) -> DustTag<'a>,
{
    move |i: &'a str| {
        let (i, (opening_name, inner, maybe_else, _closing_name)) = verify(
            tuple((
                delimited(tag(open_matcher), path, tag("}")),
                opt(body),
                opt(preceded(tag("{:else}"), opt(body))),
                delimited(tag("{/"), path, tag("}")),
            )),
            |(open, _inn, _maybe_else, close)| open == close,
        )(i)?;

        Ok((
            i,
            constructor(Container {
                path: opening_name,
                contents: inner,
                else_contents: maybe_else.flatten(),
            }),
        ))
    }
}

fn self_closing_conditional<'a, F>(
    open_matcher: &'static str,
    constructor: F,
) -> impl Fn(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Fn(Container<'a>) -> DustTag<'a>,
{
    move |i: &'a str| {
        let (i, path) = delimited(tag(open_matcher), path, tag("/}"))(i)?;

        Ok((
            i,
            constructor(Container {
                path: path,
                contents: None,
                else_contents: None,
            }),
        ))
    }
}

fn named_block<'a, F>(
    open_matcher: &'static str,
    constructor: F,
) -> impl FnMut(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Copy + Fn(NamedBlock<'a>) -> DustTag<'a>,
{
    alt((
        named_block_with_body(open_matcher, constructor),
        self_closing_named_block(open_matcher, constructor),
    ))
}

fn named_block_with_body<'a, F>(
    open_matcher: &'static str,
    constructor: F,
) -> impl Fn(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Fn(NamedBlock<'a>) -> DustTag<'a>,
{
    move |i: &'a str| {
        let (i, (opening_name, inner, _closing_name)) = verify(
            tuple((
                delimited(tag(open_matcher), key, tag("}")),
                opt(body),
                delimited(tag("{/"), key, tag("}")),
            )),
            |(open, _inn, close)| open == close,
        )(i)?;

        Ok((
            i,
            constructor(NamedBlock {
                name: opening_name,
                contents: inner,
            }),
        ))
    }
}

fn self_closing_named_block<'a, F>(
    open_matcher: &'static str,
    constructor: F,
) -> impl Fn(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Fn(NamedBlock<'a>) -> DustTag<'a>,
{
    move |i: &'a str| {
        let (i, name) = delimited(tag(open_matcher), key, tag("/}"))(i)?;

        Ok((
            i,
            constructor(NamedBlock {
                name: name,
                contents: None,
            }),
        ))
    }
}

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

fn parameterized_block_with_body<'a, F>(
    open_matcher: &'static str,
    tag_name: &'static str,
    constructor: F,
) -> impl Fn(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Fn(ParameterizedBlock<'a>) -> DustTag<'a>,
{
    move |i: &'a str| {
        let (i, (name, params, inner, maybe_else, _closing_name)) = tuple((
            preceded(tag(open_matcher), tag(tag_name)),
            terminated(
                opt(preceded(space1, separated_list1(space1, key_value_pair))),
                tag("}"),
            ),
            opt(body),
            opt(preceded(tag("{:else}"), opt(body))),
            delimited(tag("{/"), tag(tag_name), tag("}")),
        ))(i)?;

        Ok((
            i,
            constructor(ParameterizedBlock {
                name: name,
                params: params.unwrap_or(Vec::new()),
                contents: inner,
                else_contents: maybe_else.flatten(),
            }),
        ))
    }
}

fn parameterized_self_closing_block<'a, F>(
    open_matcher: &'static str,
    tag_name: &'static str,
    constructor: F,
) -> impl Fn(&'a str) -> IResult<&'a str, DustTag<'a>>
where
    F: Fn(ParameterizedBlock<'a>) -> DustTag<'a>,
{
    move |i: &'a str| {
        let (i, (name, params)) = delimited(
            tag(open_matcher),
            tuple((
                tag(tag_name),
                opt(preceded(space1, separated_list1(space1, key_value_pair))),
            )),
            tag("/}"),
        )(i)?;

        Ok((
            i,
            constructor(ParameterizedBlock {
                name: name,
                params: params.unwrap_or(Vec::new()),
                contents: None,
                else_contents: None,
            }),
        ))
    }
}

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>,
{
    move |i: &'a str| {
        let (i, (name, params)) = delimited(
            tag(open_matcher),
            tuple((
                alt((map(key, String::from), quoted_string)),
                opt(preceded(space1, separated_list1(space1, key_value_pair))),
            )),
            tag("/}"),
        )(i)?;

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

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 inside a span
/// 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 span_end_of_line(i: &str) -> IResult<&str, (&str, &str)> {
    tuple((line_ending, multispace0))(i)
}

fn span_line(i: &str) -> IResult<&str, &str> {
    verify(
        take_until_parser_matches(alt((
            tag("{"),
            line_ending,
            recognize(all_consuming(eof_whitespace)),
        ))),
        |s: &str| s.len() > 0,
    )(i)
}

/// Any text that is not a Dust element
fn span(i: &str) -> IResult<&str, Span> {
    let (remaining, lines) = preceded(
        opt(span_end_of_line),
        many1(terminated(span_line, opt(span_end_of_line))),
    )(i)?;
    Ok((remaining, Span { contents: lines }))
}

fn body(i: &str) -> IResult<&str, Body> {
    let (remaining, template_elements) = many1(alt((
        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) = 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_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_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(("zzz}", 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((
                "{! this is a comment without a close",
                ErrorKind::Tag
            )))
        );
    }

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

    #[test]
    fn test_span_line() {
        assert_eq!(
            super::span_line("this is just some text"),
            Ok(("", "this is just some text"))
        );
        assert_eq!(
            super::span_line("this is just some text {~lb}"),
            Ok(("{~lb}", "this is just some text "))
        );
        assert_eq!(
            super::span_line("{~lb}"),
            Err(Error(("{~lb}", ErrorKind::Verify)))
        );
    }

    #[test]
    fn test_span() {
        assert_eq!(
            super::span("this is just some text"),
            Ok((
                "",
                Span {
                    contents: vec!["this is just some text"]
                }
            ))
        );
        assert_eq!(
            super::span("this is just some text {~lb}"),
            Ok((
                "{~lb}",
                Span {
                    contents: vec!["this is just some text "]
                }
            ))
        );
        assert_eq!(
            super::span("{~lb}"),
            Err(Error(("{~lb}", ErrorKind::Verify)))
        );
        assert_eq!(
            super::span("this is       \t   \n\n    \t \n   \t  multiline text\n     {foo}"),
            Ok((
                "{foo}",
                Span {
                    contents: vec!["this is       \t   ", "multiline text"]
                }
            ))
        );
        assert_eq!(
            super::span("\n    leading whitespace"),
            Ok((
                "",
                Span {
                    contents: vec!["leading whitespace"]
                }
            ))
        );
    }

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

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

    #[test]
    fn test_self_closing_section() {
        assert_eq!(
            super::dust_tag("{#foo.bar/}"),
            Ok((
                "",
                DustTag::DTSection(Container {
                    path: Path {
                        keys: vec!["foo", "bar"]
                    },
                    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(Container {
                    path: Path {
                        keys: vec!["foo", "bar"]
                    },
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: vec!["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(Container {
                    path: Path {
                        keys: vec!["greeting"]
                    },
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: vec!["hello "]
                            }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                    else_contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: vec!["goodbye "]
                            }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    }),
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_block() {
        assert_eq!(
            super::dust_tag("{+foo/}"),
            Ok((
                "",
                DustTag::DTBlock(NamedBlock {
                    name: "foo",
                    contents: None
                })
            ))
        );
    }

    #[test]
    fn test_block() {
        assert_eq!(
            super::dust_tag("{+foo}hello {name}{/foo}"),
            Ok((
                "",
                DustTag::DTBlock(NamedBlock {
                    name: "foo",
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: vec!["hello "]
                            }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    })
                })
            ))
        );
    }

    #[test]
    fn test_self_closing_inline_partial() {
        assert_eq!(
            super::dust_tag("{<foo/}"),
            Ok((
                "",
                DustTag::DTInlinePartial(NamedBlock {
                    name: "foo",
                    contents: None
                })
            ))
        );
    }

    #[test]
    fn test_inline_partial() {
        assert_eq!(
            super::dust_tag("{<foo}hello {name}{/foo}"),
            Ok((
                "",
                DustTag::DTInlinePartial(NamedBlock {
                    name: "foo",
                    contents: Some(Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: vec!["hello "]
                            }),
                            TemplateElement::TETag(DustTag::DTReference(Reference {
                                path: Path { keys: vec!["name"] },
                                filters: Vec::new()
                            }))
                        ]
                    })
                })
            ))
        );
    }

    #[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: "foo".to_owned(),
                    params: vec![
                        KVPair {
                            key: "bar",
                            value: RValue::RVPath(Path { keys: vec!["baz"] })
                        },
                        KVPair {
                            key: "animal",
                            value: RValue::RVString("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: r#"template name * with * special " characters"#.to_owned(),
                    params: vec![
                        KVPair {
                            key: "bar",
                            value: RValue::RVPath(Path { keys: vec!["baz"] })
                        },
                        KVPair {
                            key: "animal",
                            value: RValue::RVString("cat".to_owned())
                        }
                    ]
                })
            ))
        );
    }

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

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

    #[test]
    fn test_temp_full_document() {
        assert_eq!(
            super::template(
                "- simple -{~n}
{#names}{.}{/names}
{~n}- new lines -{~n}
{#names}
{.}
{/names}"
            ),
            Ok::<_, nom::Err<(&str, ErrorKind)>>((
                "",
                Template {
                    contents: Body {
                        elements: vec![
                            TemplateElement::TESpan(Span {
                                contents: vec!["- simple -"]
                            }),
                            TemplateElement::TETag(DustTag::DTSpecial(Special::NewLine))
                        ]
                    }
                }
            ))
        );
    }
}