use std::{
    borrow::Cow,
    fmt::{self, Display},
};

#[cfg(test)]
use proptest::prelude::*;

use proptest_derive::Arbitrary;
use winnow::{Parser, error::ParserError};

#[derive(Copy, Clone, Debug, PartialEq)]
pub enum Separator {
    Eq,
    Colon,
}

impl Separator {
    fn parser<'a, E: ParserError<&'a str>>(input: &mut &'a str) -> Result<Self, E> {
        use winnow::{combinator::*, prelude::*, token::*};

        alt((
            literal('=').value(Self::Eq),
            literal(':').value(Self::Colon),
        ))
        .parse_next(input)
    }
}

impl Display for Separator {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Separator::Eq => write!(f, "="),
            Separator::Colon => write!(f, ":"),
        }
    }
}

#[derive(Copy, Clone, Debug, Arbitrary, PartialEq)]
pub enum QuoteType {
    Single,
    Double,
    Backtick,
}

impl QuoteType {
    fn parse<'a, E: ParserError<&'a str>>(input: &mut &'a str) -> Result<Self, E> {
        use winnow::{combinator::*, prelude::*, token::*};

        alt((
            literal('\'').value(Self::Single),
            literal('\"').value(Self::Double),
            literal('`').value(Self::Backtick),
        ))
        .parse_next(input)
    }
}

impl Display for QuoteType {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            QuoteType::Single => write!(f, "\""),
            QuoteType::Double => write!(f, "\'"),
            QuoteType::Backtick => write!(f, "`"),
        }
    }
}

#[derive(Clone, Debug, Arbitrary, PartialEq)]
pub enum Delimiter {
    Paren,
    Bracket,
    Brace,
    Angle,
}

impl Delimiter {
    fn fmt_start(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Delimiter::Paren => write!(f, "("),
            Delimiter::Bracket => write!(f, "["),
            Delimiter::Brace => write!(f, "{{"),
            Delimiter::Angle => write!(f, "<"),
        }
    }

    fn fmt_end(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Delimiter::Paren => write!(f, ")"),
            Delimiter::Bracket => write!(f, "]"),
            Delimiter::Brace => write!(f, "}}"),
            Delimiter::Angle => write!(f, ">"),
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct AnyString<'a> {
    prefix: Cow<'a, str>,
    ty: QuoteType,
    contents: Cow<'a, str>,
    num_hashtags: usize,
    suffix: Cow<'a, str>,
}

impl AnyString<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        let prefix = "\\w*";
        let ty = any::<QuoteType>();
        let contents = "\\w*";
        let num_hashtags = 0usize..3;
        let suffix = "\\w*";

        (prefix, ty, contents, num_hashtags, suffix).prop_map(
            |(prefix, ty, contents, num_hashtags, suffix)| Self {
                prefix: prefix.into(),
                ty,
                contents: contents.into(),
                num_hashtags,
                suffix: suffix.into(),
            },
        )
    }
}

impl<'a> AnyString<'a> {
    fn parse<E: ParserError<&'a str>>() -> impl Parser<&'a str, Self, E> {
        use winnow::{combinator::*, prelude::*, token::*};

        // let (prefix, num_hashtags, quote) =
        let preamble = (
            take_while(0.., |b: char| !b.is_whitespace()),
            take_while(0.., |c| c == '#').map(|i: &'a str| i.len()),
            alt((
                '`'.value(QuoteType::Backtick),
                '\''.value(QuoteType::Single),
                '\"'.value(QuoteType::Double),
            )),
        );

        preamble.flat_map(
            |(prefix, num_hashtags, quote): (&'a str, usize, QuoteType)| {
                let end = (
                    match quote {
                        QuoteType::Single => '\'',
                        QuoteType::Double => '\"',
                        QuoteType::Backtick => '`',
                    },
                    repeat::<_, _, Cow<'a, str>, _, _>(num_hashtags..=num_hashtags, literal("#")),
                );

                let contents = repeat_till(0.., any, end).map(|(contents, _)| contents);
                let suffix = take_while(0.., |b: char| !b.is_whitespace());

                (contents, suffix).map(move |(contents, suffix): (Cow<'a, str>, &'a str)| Self {
                    prefix: prefix.into(),
                    ty: quote,
                    contents,
                    num_hashtags,
                    suffix: suffix.into(),
                })
            },
        )
    }
}

impl<'a> Display for AnyString<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.prefix)?;
        for _ in 0..self.num_hashtags {
            write!(f, "#")?;
        }
        write!(f, "{}", self.ty)?;
        write!(f, "{}", self.contents)?;

        for _ in 0..self.num_hashtags {
            write!(f, "#")?;
        }
        write!(f, "{}", self.suffix)
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct Space<'a>(Cow<'a, str>);

impl Space<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        " *".prop_map(|spaces| Self(spaces.into()))
    }
}

impl<'a> Space<'a> {
    fn parse<E: ParserError<&'a str>>() -> impl Parser<&'a str, Self, E> {
        use winnow::{prelude::*, token::*};

        take_while(0.., |b: char| b.is_whitespace()).map(|i: &'a str| Self(i.into()))
    }
}

impl<'a> Display for Space<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.0)
    }
}

#[derive(Copy, Clone, Debug, PartialEq, Arbitrary)]
pub enum PathSep {
    Slash,
    Backslash,
}

impl PathSep {
    fn parse<'a, E: ParserError<&'a str>>() -> impl Parser<&'a str, Self, E> {
        use winnow::{combinator::*, prelude::*};

        alt(('/'.value(Self::Slash), '\\'.value(Self::Backslash)))
    }
}

impl Display for PathSep {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            PathSep::Slash => write!(f, "/"),
            PathSep::Backslash => write!(f, "\\"),
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct PathSegment<'a> {
    leading_separator: PathSep,
    segment: Cow<'a, str>,
}

impl PathSegment<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        (any::<PathSep>(), "\\w*").prop_map(|(leading_separator, segment)| Self {
            leading_separator,
            segment: segment.into(),
        })
    }
}

impl<'a> Display for PathSegment<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.leading_separator)?;
        write!(f, "{}", self.segment)
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct FileLocation<'a> {
    line: Cow<'a, str>,
    offset: Option<Cow<'a, str>>,
}

impl FileLocation<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        use proptest::option::*;
        ("[0-9]{0,4}", of("[0-9]{0,4}")).prop_map(|(line, offset)| Self {
            line: line.into(),
            offset: offset.map(Into::into),
        })
    }
}

impl<'a> Display for FileLocation<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.line)?;
        if let Some(offset) = &self.offset {
            write!(f, "{offset}")?;
        }
        Ok(())
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct FileName<'a> {
    leading_separator: PathSep,
    segment: Cow<'a, str>,
    ext_excluding_dot: Option<Cow<'a, str>>,
    location: Option<FileLocation<'a>>,
}

impl FileName<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        use proptest::option::*;
        (
            any::<PathSep>(),
            "\\w*",
            of(".{0,3}"),
            of(FileLocation::arb()),
        )
            .prop_map(
                |(leading_separator, segment, ext_excluding_dot, location)| Self {
                    leading_separator,
                    segment: segment.into(),
                    ext_excluding_dot: ext_excluding_dot.map(Into::into),
                    location,
                },
            )
    }
}

impl<'a> FileName<'a> {
    fn parse(segment: PathSegment<'a>) -> Self {
        fn rsplit<'a>(
            input: Cow<'a, str>,
            delimiter: char,
        ) -> Option<(Cow<'a, str>, Cow<'a, str>)> {
            match input {
                Cow::Borrowed(s) => s
                    .rsplit_once(delimiter)
                    .map(|(a, b)| (Cow::Borrowed(a), Cow::Borrowed(b))),
                Cow::Owned(s) => s
                    .rsplit_once(delimiter)
                    .map(|(a, b)| (Cow::Owned(a.to_string()), Cow::Owned(b.to_string()))),
            }
        }

        let (rest, location) = if let Some((before, offset)) = rsplit(segment.segment.clone(), ':')
        {
            if let Some((before, line)) = rsplit(before.clone(), ':') {
                (
                    before,
                    Some(FileLocation {
                        line,
                        offset: Some(offset),
                    }),
                )
            } else {
                (
                    before,
                    Some(FileLocation {
                        line: offset,
                        offset: None,
                    }),
                )
            }
        } else {
            (segment.segment, None)
        };

        let (new_segment, ext_excluding_dot) =
            if let Some((segment, ext_excluding_dot)) = rsplit(rest.clone(), '.') {
                (segment, Some(ext_excluding_dot))
            } else {
                (rest, None)
            };

        Self {
            leading_separator: segment.leading_separator,
            segment: new_segment,
            ext_excluding_dot,
            location,
        }
    }
}

impl<'a> Display for FileName<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.leading_separator)?;
        write!(f, "{}", self.segment)?;
        if let Some(ext) = &self.ext_excluding_dot {
            write!(f, ".{ext}")?;
        }
        if let Some(loc) = &self.location {
            write!(f, "{loc}")?;
        }
        Ok(())
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct Path<'a> {
    drive_excluding_colon: Option<char>,
    segments: Vec<PathSegment<'a>>,
    filename: FileName<'a>,
}

impl Path<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        use proptest::{char::*, collection::*, option::*};
        (
            of(range('A', 'Z')),
            vec(PathSegment::arb(), 0..3),
            FileName::arb(),
        )
            .prop_map(|(drive_excluding_colon, segments, filename)| Self {
                drive_excluding_colon,
                segments,
                filename,
            })
    }
}

impl<'a> Path<'a> {
    fn parse<E: ParserError<&'a str>>() -> impl Parser<&'a str, Self, E> {
        use winnow::{combinator::*, prelude::*, token::*};

        let till_next_sep = repeat_till(
            0..,
            any::<&'a str, E>.verify(|i: &char| !(*i).is_whitespace()),
            PathSep::parse(),
        )
        .map(|(segment, _)| segment);

        let sep_and_next =
            (PathSep::parse(), till_next_sep).map(|(leading_separator, segment)| PathSegment {
                leading_separator,
                segment,
            });
        let drive = opt((
            any::<&'a str, E>.verify(|x: &char| matches!(*x, 'A'..='Z')),
            ':',
        ))
        .map(|i| i.map(|(letter, _): (char, char)| letter));
        let drive_and_segments = (
            drive,
            repeat_till(
                1..,
                sep_and_next,
                any.verify(|i: &char| (*i).is_whitespace()),
            )
            .map(|(segments, _): (Vec<PathSegment>, _)| {
                let (rest, last) = {
                    let mut segments = segments;
                    let last = segments.pop().unwrap();
                    (segments, last)
                };

                (rest, FileName::parse(last))
            }),
        );

        drive_and_segments.map(|(drive, (segments, filename))| Self {
            drive_excluding_colon: drive,
            segments,
            filename,
        })
    }
}

impl<'a> Display for Path<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        if let Some(drive) = &self.drive_excluding_colon {
            write!(f, "{drive}:")?;
        }
        for segment in &self.segments {
            write!(f, "{segment}:")?;
        }
        write!(f, "{}", self.filename)
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct Number<'a>(Cow<'a, str>);

impl Number<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        prop_oneof![
            any::<i64>().prop_map(|number| Self(number.to_string().into())),
            any::<f64>().prop_map(|number| Self(number.to_string().into()))
        ]
    }
}

impl<'a> Number<'a> {
    fn parse<E: ParserError<&'a str>>() -> impl Parser<&'a str, Self, E> {
        use winnow::{ascii::*, combinator::*, prelude::*};

        alt((float::<_, f64, _>.take(), dec_int::<_, i64, _>.take())).map(|i: &str| Self(i.into()))
    }
}

impl<'a> Display for Number<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.0)
    }
}

/// Anything that doesn't contain spaces, and that can be a prefix of `Delimited`.
/// i.e. an english word, or rust `::`-separated Path
#[derive(Clone, Debug, PartialEq)]
pub enum Atom<'a> {
    Text(Cow<'a, str>),
}

impl<'a> Display for Atom<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Atom::Text(text) => write!(f, "{text}"),
        }
    }
}

impl Atom<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        "\\w*".prop_map(|i| Self::Text(i.into()))
    }
}

impl<'a> Atom<'a> {
    fn parse<E: ParserError<&'a str>>() -> impl Parser<&'a str, Self, E> {
        use winnow::{combinator::*, prelude::*, token::*};

        alt((repeat(0.., any.verify(|i: &char| !(*i).is_whitespace())).map(Self::Text),))
    }
}

#[derive(Clone, Debug, PartialEq)]
pub enum Token<'a> {
    True,
    False,
    None,

    Path(Path<'a>),
    String(AnyString<'a>),
    Number(Number<'a>),

    // TODO: RustPath
    Separated {
        before: Box<Token<'a>>,
        space_before: Space<'a>,
        separator: Separator,
        after: Box<Segment<'a>>,
    },
    Delimited(Delimited<'a>),

    Atom(Atom<'a>),
}

impl Token<'static> {
    #[cfg(test)]
    fn arb() -> impl Strategy<Value = Self> {
        let leaf = prop_oneof![
            Just(Self::True),
            Just(Self::False),
            Just(Self::None),
            Path::arb().prop_map(Self::Path),
            AnyString::arb().prop_map(Self::String),
            Number::arb().prop_map(Self::Number),
            Atom::arb().prop_map(Self::Atom),
        ];

        leaf.prop_recursive(4, 64, 16, |token| {
            Delimited::arb(token).prop_map(Self::Delimited).boxed()
        })
    }
}

impl<'a> Token<'a> {
    fn parse<E: ParserError<&'a str> + 'a>() -> impl Parser<&'a str, Self, E> {
        use winnow::{combinator::*, prelude::*};

        let delimited: Box<dyn Parser<&'a str, Self, E>> =
            Box::new(Delimited::parse().map(Self::Delimited));

        alt((
            "true".value(Self::True),
            "false".value(Self::False),
            "None".value(Self::None),
            Path::parse().map(Self::Path),
            AnyString::parse().map(Self::String),
            Number::parse().map(Self::Number),
            delimited,
            Atom::parse().map(Self::Atom),
        ))
    }
}

impl<'a> Display for Token<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Token::Number(number) => write!(f, "{number}"),
            Token::True => write!(f, "true"),
            Token::False => write!(f, "false"),
            Token::None => write!(f, "None"),
            Token::Atom(atom) => write!(f, "{atom}"),
            Token::Path(path) => write!(f, "{path}"),
            Token::Separated {
                before,
                space_before,
                separator,
                after,
            } => write!(f, "{before}{space_before}{separator}{after}"),
            Token::Delimited(delimited) => write!(f, "{delimited}"),
            Token::String(s) => write!(f, "{s}"),
        }
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct Delimited<'a> {
    prefix: Atom<'a>,
    delimiter: Delimiter,
    contents: Segments<'a>,
}

impl Delimited<'static> {
    #[cfg(test)]
    fn arb(token: impl Strategy<Value = Token<'static>>) -> impl Strategy<Value = Self> {
        (Atom::arb(), any::<Delimiter>(), Segments::arb(token)).prop_map(
            |(prefix, delimiter, contents)| Self {
                prefix,
                delimiter,
                contents,
            },
        )
    }
}

impl<'a> Delimited<'a> {
    fn parse<E: ParserError<&'a str> + 'a>() -> impl Parser<&'a str, Self, E> {
        use winnow::{combinator::*, prelude::*, token::*};

        (
            Atom::parse(),
            alt((
                literal('(').map(|_| literal(')').value(Delimiter::Paren)),
                literal('[').map(|_| literal(']').value(Delimiter::Bracket)),
                literal('{').map(|_| literal('}').value(Delimiter::Brace)),
            ))
            .flat_map(|end| Segments::parse(end)),
        )
            .map(|(prefix, (contents, delimiter))| Self {
                prefix,
                delimiter,
                contents,
            })
    }
}

impl<'a> Display for Delimited<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.prefix)?;
        self.delimiter.fmt_start(f)?;
        write!(f, "{}", self.contents)?;
        self.delimiter.fmt_end(f)
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct Segment<'a> {
    leading_space: Space<'a>,
    token: Token<'a>,
}

impl Segment<'static> {
    #[cfg(test)]
    fn arb(token: impl Strategy<Value = Token<'static>>) -> impl Strategy<Value = Self> {
        (Space::arb(), token).prop_map(|(leading_space, token)| Self {
            leading_space,
            token,
        })
    }
}

impl<'a> Segment<'a> {
    fn parse<E: ParserError<&'a str> + 'a>() -> impl Parser<&'a str, Self, E> {
        use winnow::prelude::*;

        (Space::parse(), Token::parse()).map(|(leading_space, token)| Self {
            leading_space,
            token,
        })
    }
}

impl<'a> Display for Segment<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "{}", self.leading_space)?;
        write!(f, "{}", self.token)
    }
}

#[derive(Clone, Debug, PartialEq)]
pub struct Segments<'a> {
    segments: Vec<Segment<'a>>,
    trailing_space: Space<'a>,
}

impl Segments<'static> {
    #[cfg(test)]
    fn arb(token: impl Strategy<Value = Token<'static>>) -> impl Strategy<Value = Self> {
        use proptest::collection::*;

        (vec(Segment::arb(token), 1..10), Space::arb()).prop_map(|(segments, trailing_space)| {
            Self {
                segments,
                trailing_space,
            }
        })
    }
}

impl<'a> Segments<'a> {
    fn parse<E: ParserError<&'a str> + 'a, End: 'a>(
        end: impl Parser<&'a str, End, E>,
    ) -> impl Parser<&'a str, (Self, End), E> {
        use winnow::{combinator::*, prelude::*};

        repeat_till(0.., Segment::parse(), (Space::parse(), end)).map(
            |(segments, (trailing_space, end)): (Vec<_>, _)| {
                (
                    Self {
                        segments,
                        trailing_space,
                    },
                    end,
                )
            },
        )
    }
}

impl<'a> Display for Segments<'a> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        for segment in &self.segments {
            write!(f, "{segment}")?;
        }
        write!(f, "{}", self.trailing_space)
    }
}

fn parse_input<'a>(i: &'a str) -> Result<Segments<'a>, String> {
    use winnow::combinator::eof;
    Segments::parse(eof::<&str, winnow::error::EmptyError>)
        .map(|(segments, _)| segments)
        .parse(i)
        .map_err(|e| e.to_string())
}

#[cfg(test)]
mod tests {
    use proptest::proptest;

    use crate::format_debug_output::{Segments, Token, parse_input};

    proptest! {
        #[test]
        fn test_some_function(original in Segments::arb(Token::arb())) {
            let stringified = original.to_string();
            let parsed = parse_input(&stringified).unwrap();
            assert_eq!(parsed, original, "left:\n  `{parsed}`\nright:  `{stringified}`");
        }
    }
}