extern crate nom;

use std::collections::HashMap;
use std::io::Write;

#[derive(Debug, PartialEq, Eq, Clone)]
pub enum T {
    // Unit
    Unit,
    // Naturals
    N3(u8),
    N6(u64),
    N7(u128),
    // Integers
    I3(i8),
    I6(i64),
    I7(i128),
    // Text
    // TODO: make into &str
    Text(String),
    // Tags
    Sum(Tag),
    // TODO: make into &str
    Record(HashMap<String, Box<T>>),
    List(Box<Vec<T>>),
}

#[derive(Debug, PartialEq, Eq, Clone)]
pub struct Tag {
    // TODO: make into &str
    pub tag: String,
    pub val: Box<T>
}

fn encode_tag<W: Write>(w: &mut W, tag: String, val: T) -> std::io::Result<()> {
    write!(w, "<{}:{}|", tag.len(), tag)?;
    encode(w, val)?;
    Ok(())
}

pub fn encode<W: Write>(w: &mut W, t: T) -> std::io::Result<()> {
  match t {
      T::Unit => write!(w, "u,"),
      T::N3(n) => write!(w, "n3:{},", n),
      T::N6(n) => write!(w, "n6:{},", n),
      T::N7(n) => write!(w, "n7:{},", n),
      T::I3(i) => write!(w, "i3:{},", i),
      T::I6(i) => write!(w, "i6:{},", i),
      T::I7(i) => write!(w, "i7:{},", i),
      T::Text(s) => write!(w, "t{}:{},", s.len(), s),
      T::Sum(Tag{tag, val}) => encode_tag(w, tag, *val),
      T::Record(m) => {
          let mut c = std::io::Cursor::new(vec![]);
          for (k, v) in m {
              encode_tag(&mut c, k, *v)?;
          }
          write!(w, "{{{}:", c.get_ref().len())?;
          w.write(c.get_ref())?;
          write!(w, "}}")
      },
      T::List(l) => {
          let mut c = std::io::Cursor::new(vec![]);
          for v in *l {
              encode(&mut c, v)?;
          };
          write!(w, "[{}:", c.get_ref().len())?;
          w.write(c.get_ref())?;
          write!(w, "]")
      }
  }
}

pub fn dict(d: Vec<(String, T)>) -> T {
    T::Record(
        d.into_iter()
            .map(|(k,v)| (k, Box::new(v)))
            // to ignore duplicate entries after the first
            .rev()
            .collect::<HashMap<_,_>>())
}

pub fn text(s: String) -> T {
    T::Text(s)
}

mod parse {
    use super::{T, Tag};

    use std::str::FromStr;
    use std::ops::Neg;
    use std::collections::HashMap;

    use nom::{IResult};
    use nom::bytes::complete::{tag, take};
    use nom::branch::{alt};
    use nom::character::complete::{digit1, char};
    use nom::sequence::{tuple};
    use nom::combinator::{map, map_res, flat_map, opt};
    use nom::error::{context, ErrorKind, ParseError};

    fn unit_t(s: &[u8]) -> IResult<&[u8], ()> {
        let (s, _) = context("unit", tag("u,"))(s)?;
        Ok((s, ()))
    }

    fn usize_t(s: &[u8]) -> IResult<&[u8], usize> {
        context(
            "usize",
            map_res(
                map_res(digit1, |n| std::str::from_utf8(n)),
                |s| s.parse::<usize>())
        )(s)
    }


    fn uint_t<'a, I: FromStr + 'a>(t: &'static str) -> impl Fn(&'a [u8]) -> IResult<&'a [u8], I> {
        move |s: &'a [u8]| {
            let (s, (_, _, int, _)) = tuple((
                tag(t.as_bytes()),
                char(':'),
                map_res(
                    map_res(digit1, |n: &[u8]| std::str::from_utf8(n)),
                    |s| s.parse::<I>()
                ),
                char(',')
            ))(s)?;
            Ok((s, int))
        }
    }

    fn int_t<'a, I: FromStr + Neg<Output=I>>(t: &'static str) -> impl Fn(&'a [u8]) -> IResult<&[u8], I> {
        context(
            t,
            move |s: &'a [u8]| {
                let (s, (_, _, neg, int, _)) = tuple((
                    tag(t.as_bytes()),
                    char(':'),
                    opt(char('-')),
                    map_res(
                        map_res(digit1, |n: &[u8]| std::str::from_utf8(n)),
                        |s| s.parse::<I>()
                    ),
                    char(',')
                ))(s)?;
                let res = match neg {
                    Some(_) => -int,
                    None => int,
                };
                Ok((s, res))
            }
        )
    }

    fn tag_t(s: &[u8]) -> IResult<&[u8], Tag> {
        let (s, (_, len, _)) = tuple((
            char('<'),
            usize_t,
            char(':'),
        ))(s)?;
        let (s, (tag, _, recurse)) = tuple((
            take(len),
            char('|'),
            // recurses into the main parser
            t_t
        ))(s)?;
        Ok((s, Tag {
            tag: std::str::from_utf8(tag)
                .map_err(|_| nom::Err::Failure((s, ErrorKind::Char)))
                .map(|s| s.to_string())?,
            val: Box::new(recurse)
        }))
    }

    /// parse text scalar (`t5:hello,`)
    fn text(s: &[u8]) -> IResult<&[u8], T> {
        let (s, (_, len, _)) = tuple((
            char('t'),
            usize_t,
            char(':')
        ))(s)?;
        let (s, (res, _)) = tuple((
            take(len),
            char(',')
        ))(s)?;
        Ok((s, T::Text(
            std::str::from_utf8(res)
                .map_err(|_| nom::Err::Failure((s, ErrorKind::Char)))
                .map(|s| s.to_string())?,
        )))
    }

    fn list_t(s: &[u8]) -> IResult<&[u8], Vec<T>> {
        let (s, (_, _, _, vec, _)) = tuple((
            char('['),
            usize_t,
            char(':'),
            nom::multi::many0(t_t),
            char(']')
        ))(s)?;
        Ok((s, vec))
    }

    fn record_t(s: &[u8]) -> IResult<&[u8], HashMap<String, Box<T>>> {
        let (s, (_, _, _, map, _)) = tuple((
            char('{'),
            usize_t,
            char(':'),
            nom::multi::fold_many1(
                tag_t,
                HashMap::new(),
                |mut acc: HashMap<_, _>, Tag { tag, val }| {
                    // ignore duplicated tag names that appear later
                    if !acc.contains_key(&tag) {
                        acc.insert(tag, val);
                    }
                    acc
                }
            ),
            char('}')
        ))(s)?;
        Ok((s, map))
    }

    fn t_t(s: &[u8]) -> IResult<&[u8], T>  {
        alt((
            text,
            map(unit_t, |_| T::Unit),
            map(tag_t, |t| T::Sum(t)),
            map(list_t, |l| T::List(Box::new(l))),
            map(record_t, |p| T::Record(p)),

            // 8, 64 and 128 bit
            map(uint_t("n3"), |u| T::N3(u)),
            map(uint_t("n6"), |u| T::N6(u)),
            map(uint_t("n7"), |u| T::N7(u)),
            map(int_t("i3"), |u| T::I3(u)),
            map(int_t("i6"), |u| T::I6(u)),
            map(int_t("i7"), |u| T::I7(u)),

            // less common
            map(uint_t("n1"), |u| T::N3(u)),
            map(uint_t("n2"), |u| T::N3(u)),
            map(uint_t("n4"), |u| T::N6(u)),
            map(uint_t("n5"), |u| T::N6(u)),
            map(int_t("i1"), |u| T::I3(u)),
            map(int_t("i2"), |u| T::I3(u)),
            map(int_t("i4"), |u| T::I6(u)),
            map(int_t("i5"), |u| T::I6(u)),
            // TODO: 8, 9 not supported
        ))(s)
    }

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

        #[test]
        fn test_parse_unit_t() {
            assert_eq!(
                unit_t("u,".as_bytes()),
                Ok(("".as_bytes(), ()))
            );
        }

        #[test]
        fn test_parse_usize_t() {
            assert_eq!(
                usize_t("32foo".as_bytes()),
                Ok(("foo".as_bytes(), 32))
            );
        }

        #[test]
        fn test_parse_int_t() {
            assert_eq!(
                uint_t::<u8>("n3")("n3:42,abc".as_bytes()),
                Ok(("abc".as_bytes(), 42))
            );
            assert_eq!(
                uint_t::<u8>("n3")("n3:1024,abc".as_bytes()),
                Err(nom::Err::Error(("1024,abc".as_bytes(), nom::error::ErrorKind::MapRes)))
            );
            assert_eq!(
                int_t::<i64>("i6")("i6:-23,abc".as_bytes()),
                Ok(("abc".as_bytes(), -23))
            );
            assert_eq!(
                int_t::<i128>("i3")("i3:0,:abc".as_bytes()),
                Ok((":abc".as_bytes(), 0))
            );
            assert_eq!(
                uint_t::<u8>("n7")("n7:09,".as_bytes()),
                Ok(("".as_bytes(), 9))
            );
            // assert_eq!(
            //     length("c"),
            //     Err(nom::Err::Error(("c", nom::error::ErrorKind::Digit)))
            // );
            // assert_eq!(
            //     length(":"),
            //     Err(nom::Err::Error((":", nom::error::ErrorKind::Digit)))
            // );
        }

        #[test]
        fn test_parse_text() {
            assert_eq!(
                text("t5:hello,".as_bytes()),
                Ok(("".as_bytes(), T::Text("hello".to_owned())))
            );
            assert_eq!(
                text("t4:fo,".as_bytes()),
                // TODO: way better parse error messages
                Err(nom::Err::Error(("fo,".as_bytes(), nom::error::ErrorKind::Eof)))
            );
            assert_eq!(
                text("t9:今日は,".as_bytes()),
                Ok(("".as_bytes(), T::Text("今日は".to_owned())))
            );
        }

        #[test]
        fn test_list() {
            assert_eq!(
                list_t("[0:]".as_bytes()),
                Ok(("".as_bytes(), vec![]))
            );
            assert_eq!(
                list_t("[6:u,u,u,]".as_bytes()),
                Ok(("".as_bytes(), vec![
                    T::Unit,
                    T::Unit,
                    T::Unit,
                ]))
            );
            assert_eq!(
                list_t("[15:u,[7:t3:foo,]u,]".as_bytes()),
                Ok(("".as_bytes(), vec![
                    T::Unit,
                    T::List(Box::new(vec![T::Text("foo".to_owned())])),
                    T::Unit,
                ]))
            );
        }

        #[test]
        fn test_record() {
            assert_eq!(
                record_t("{21:<1:a|u,<1:b|u,<1:c|u,}".as_bytes()),
                Ok(("".as_bytes(), vec![
                    ("a".to_owned(), Box::new(T::Unit)),
                    ("b".to_owned(), Box::new(T::Unit)),
                    ("c".to_owned(), Box::new(T::Unit)),
                ].into_iter().collect::<HashMap<String, Box<T>>>()))
            );
            // duplicated keys are ignored (first is taken)
            assert_eq!(
                record_t("{25:<1:a|u,<1:b|u,<1:a|i1:-1,}".as_bytes()),
                Ok(("".as_bytes(), vec![
                    ("a".to_owned(), Box::new(T::Unit)),
                    ("b".to_owned(), Box::new(T::Unit)),
                ].into_iter().collect::<HashMap<_,_>>()))
            );
        }

        #[test]
        fn test_parse() {
            assert_eq!(
                t_t("n3:255,".as_bytes()),
                Ok(("".as_bytes(), T::N3(255)))
            );
            assert_eq!(
                t_t("t6:halloo,".as_bytes()),
                Ok(("".as_bytes(), T::Text("halloo".to_owned())))
            );
            assert_eq!(
                t_t("<3:foo|t6:halloo,".as_bytes()),
                Ok(("".as_bytes(), T::Sum (Tag {
                    tag: "foo".to_owned(),
                    val: Box::new(T::Text("halloo".to_owned()))
                })))
            );
            // { a: Unit
            // , foo: List <A: Unit | B: List i3> }
            assert_eq!(
                t_t("{49:<1:a|u,<3:foo|[30:<1:A|u,<1:A|u,<1:B|[7:i3:127,]]}".as_bytes()),
                Ok(("".as_bytes(), T::Record(vec![
                    ("a".to_owned(), Box::new(T::Unit)),
                    ("foo".to_owned(), Box::new(T::List(Box::new(vec![
                        T::Sum(Tag { tag: "A".to_owned(), val: Box::new(T::Unit) }),
                        T::Sum(Tag { tag: "A".to_owned(), val: Box::new(T::Unit) }),
                        T::Sum(Tag { tag: "B".to_owned(), val: Box::new(T::List(Box::new(vec![T::I3(127)]))) }),
                    ]))))
                ].into_iter().collect::<HashMap<String, Box<T>>>())))
            );
        }

    }
}