duster/src/parser/parser.rs

use nom::branch::alt;
use nom::bytes::complete::escaped;
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::character::complete::one_of;
use nom::character::complete::space1;
use nom::combinator::map;
use nom::combinator::not;
use nom::combinator::opt;
use nom::combinator::recognize;
use nom::combinator::rest;
use nom::combinator::value;
use nom::combinator::verify;
use nom::multi::many0;
use nom::multi::many1;
use nom::multi::separated_list;
use nom::sequence::delimited;
use nom::sequence::preceded;
use nom::sequence::separated_pair;
use nom::sequence::tuple;
use nom::IResult;

#[derive(Clone, Debug, PartialEq)]
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(ParameterizedBlock<'a>),
}

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

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

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

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

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

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

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

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

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

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

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

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

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

/// 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),
        parameterized_self_closing_block("{>", DustTag::DTPartial),
    ))(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> {
    map(separated_list(tag("."), key), |body| Path { keys: body })(i)
}

/// Either a literal or a path to a value
fn rvalue(i: &str) -> IResult<&str, RValue> {
    map(path, RValue::RVPath)(i)
}

/// Parameters for a partial
fn key_value_pair(i: &str) -> IResult<&str, (&str, RValue)> {
    separated_pair(key, tag("="), rvalue)(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 Fn(&'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 Fn(&'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_self_closing_block<'a, F>(
    open_matcher: &'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((
                key,
                opt(preceded(space1, separated_list(space1, is_not(" ")))),
            )),
            tag("/}"),
        )(i)?;

        Ok((
            i,
            constructor(ParameterizedBlock {
                name: name.to_owned(),
                contents: None,
                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)
}

/// Any text that is not a Dust element
fn span(i: &str) -> IResult<&str, Span> {
    let (remaining, body) = verify(alt((take_until("{"), rest)), |s: &str| s.len() > 0)(i)?;
    Ok((remaining, Span { contents: body }))
}

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> {
    let (remaining, contents) = body(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)
}

#[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() {
        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(("{~lb}", ErrorKind::Verify)))
        );
    }

    #[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: "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: "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_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: "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: "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_self_closing_unquoted_partial() {
        assert_eq!(
            delimited(
                tag("{>"),
                tuple((
                    key,
                    opt(preceded(space1, separated_list(space1, key_value_pair))),
                )),
                tag("/}"),
            )("{>foo bar=baz/}"),
            Ok((
                "",
                (
                    "foo",
                    Some(vec![("bar", RValue::RVPath(Path { keys: vec!["baz"] }))])
                )
            ))
        );
    }
}