use std::fmt::{self, Display};
use std::ops::Range;
use std::rc::Rc;

use chumsky::prelude::*;
use chumsky::text::keyword;
use chumsky::Parser;
use itertools::Itertools;
use ordered_float::NotNan;

use super::context::Context;
use super::decls::SimpleParser;
use super::number::print_nat16;
use super::{comment, name, number, placeholder, string};
use crate::ast::{PHClass, Placeholder};
use crate::interner::Tok;
use crate::parse::operators::operators_parser;
use crate::representations::Literal;
use crate::{Interner, Location, VName};

#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub struct Entry {
  pub lexeme: Lexeme,
  pub location: Location,
}
impl Entry {
  /// Checks if the lexeme is a comment or line break
  #[must_use]
  pub fn is_filler(&self) -> bool {
    matches!(self.lexeme, Lexeme::Comment(_) | Lexeme::BR)
  }

  #[must_use]
  pub fn is_keyword(&self) -> bool {
    matches!(
      self.lexeme,
      Lexeme::Const
        | Lexeme::Export
        | Lexeme::Import
        | Lexeme::Macro
        | Lexeme::Module
    )
  }

  #[must_use]
  pub fn location(&self) -> Location { self.location.clone() }

  #[must_use]
  pub fn range(&self) -> Range<usize> {
    self.location.range().expect("An Entry can only have a known location")
  }

  #[must_use]
  pub fn file(&self) -> Rc<VName> {
    self.location.file().expect("An Entry can only have a range location")
  }
}

impl Display for Entry {
  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    self.lexeme.fmt(f)
  }
}

impl AsRef<Location> for Entry {
  fn as_ref(&self) -> &Location { &self.location }
}

#[derive(Clone, Debug, PartialEq, Eq, Hash)]
pub enum Lexeme {
  Literal(Literal),
  Name(Tok<String>),
  Arrow(NotNan<f64>),
  /// Walrus operator (formerly shorthand macro)
  Walrus,
  /// Line break
  BR,
  /// Namespace separator
  NS,
  /// Left paren
  LP(char),
  /// Right paren
  RP(char),
  /// Backslash
  BS,
  At,
  // Dot,
  Type, // type operator
  Comment(Rc<String>),
  Export,
  Import,
  Module,
  Macro,
  Const,
  Operators(Rc<VName>),
  Placeh(Placeholder),
}

impl Display for Lexeme {
  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
    match self {
      Self::Literal(l) => write!(f, "{:?}", l),
      Self::Name(token) => write!(f, "{}", **token),
      Self::Walrus => write!(f, ":="),
      Self::Arrow(prio) => write!(f, "={}=>", print_nat16(*prio)),
      Self::NS => write!(f, "::"),
      Self::LP(l) => write!(f, "{}", l),
      Self::RP(l) => match l {
        '(' => write!(f, ")"),
        '[' => write!(f, "]"),
        '{' => write!(f, "}}"),
        _ => f.debug_tuple("RP").field(l).finish(),
      },
      Self::BR => writeln!(f),
      Self::BS => write!(f, "\\"),
      Self::At => write!(f, "@"),
      Self::Type => write!(f, ":"),
      Self::Comment(text) => write!(f, "--[{}]--", text),
      Self::Export => write!(f, "export"),
      Self::Import => write!(f, "import"),
      Self::Module => write!(f, "module"),
      Self::Const => write!(f, "const"),
      Self::Macro => write!(f, "macro"),
      Self::Operators(ops) => {
        write!(f, "operators[{}]", Interner::extern_all(ops).join(" "))
      },
      Self::Placeh(Placeholder { name, class }) => match *class {
        PHClass::Scalar => write!(f, "${}", **name),
        PHClass::Vec { nonzero, prio } => {
          if nonzero { write!(f, "...") } else { write!(f, "..") }?;
          write!(f, "${}", **name)?;
          if prio != 0 {
            write!(f, ":{}", prio)?;
          };
          Ok(())
        },
      },
    }
  }
}

impl Lexeme {
  #[must_use]
  pub fn rule(prio: impl Into<f64>) -> Self {
    Lexeme::Arrow(
      NotNan::new(prio.into()).expect("Rule priority cannot be NaN"),
    )
  }

  #[must_use]
  pub fn parser<E: chumsky::Error<Entry>>(
    self,
  ) -> impl Parser<Entry, Entry, Error = E> + Clone {
    filter(move |ent: &Entry| ent.lexeme == self)
  }
}

#[derive(Clone, PartialEq, Eq, Hash)]
pub struct LexedText(pub Vec<Entry>);

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

#[must_use]
fn paren_parser(lp: char, rp: char) -> impl SimpleParser<char, Lexeme> {
  just(lp).to(Lexeme::LP(lp)).or(just(rp).to(Lexeme::RP(lp)))
}

#[must_use]
pub fn literal_parser<'a>(
  ctx: impl Context + 'a,
) -> impl SimpleParser<char, Literal> + 'a {
  choice((
    // all ints are valid floats so it takes precedence
    number::int_parser().map(Literal::Uint),
    number::float_parser().map(Literal::Num),
    string::str_parser()
      .map(move |s| Literal::Str(ctx.interner().i(&s).into())),
  ))
}

pub static BASE_OPS: &[&str] = &[",", ".", "..", "...", "*"];

#[must_use]
pub fn lexer<'a>(
  ctx: impl Context + 'a,
  source: Rc<String>,
) -> impl SimpleParser<char, Vec<Entry>> + 'a {
  let all_ops = ctx
    .ops()
    .iter()
    .map(|op| op.as_ref())
    .chain(BASE_OPS.iter().cloned())
    .map(str::to_string)
    .collect::<Vec<_>>();
  choice((
    keyword("export").to(Lexeme::Export),
    keyword("module").to(Lexeme::Module),
    keyword("import").to(Lexeme::Import),
    keyword("macro").to(Lexeme::Macro),
    keyword("const").to(Lexeme::Const),
    operators_parser({
      let ctx = ctx.clone();
      move |s| ctx.interner().i(&s)
    })
    .map(|v| Lexeme::Operators(Rc::new(v))),
    paren_parser('(', ')'),
    paren_parser('[', ']'),
    paren_parser('{', '}'),
    just(":=").to(Lexeme::Walrus),
    just("=")
      .ignore_then(number::float_parser())
      .then_ignore(just("=>"))
      .map(Lexeme::rule),
    comment::comment_parser().map(|s| Lexeme::Comment(Rc::new(s))),
    placeholder::placeholder_parser(ctx.clone()).map(Lexeme::Placeh),
    just("::").to(Lexeme::NS),
    just('\\').to(Lexeme::BS),
    just('@').to(Lexeme::At),
    just(':').to(Lexeme::Type),
    just('\n').to(Lexeme::BR),
    // just('.').to(Lexeme::Dot),
    literal_parser(ctx.clone()).map(Lexeme::Literal),
    name::name_parser(&all_ops).map({
      let ctx = ctx.clone();
      move |n| Lexeme::Name(ctx.interner().i(&n))
    }),
  ))
  .map_with_span(move |lexeme, range| Entry {
    lexeme,
    location: Location::Range {
      range,
      file: ctx.file(),
      source: source.clone(),
    },
  })
  .padded_by(one_of(" \t").repeated())
  .repeated()
  .then_ignore(end())
}