use std::{borrow::Cow, rc::Rc, cell::RefCell};
use rustyline::{validate::{Validator, ValidationResult, ValidationContext}, highlight::Highlighter, Helper, Hinter, completion::Completer};
use matrix_lang::prelude::*;

#[derive(Helper, Hinter)]
pub struct MatrixHelper {
     vm: Rc<RefCell<Vm>>
}

impl MatrixHelper {
    pub fn new(vm: Rc<RefCell<Vm>>) -> Self {
        Self { vm }
    }
}

macro_rules! unmatched {
    ($token:expr, $matched:expr) => {
        Ok(::rustyline::validate::ValidationResult::Invalid(Some(format!("Token '{:?}' at {}:{} does not have a matching '{:?}'", $token.data, $token.pos.row, $token.pos.col, $matched))))
    };
}

impl Validator for MatrixHelper {

    fn validate(&self, ctx: &mut ValidationContext) -> rustyline::Result<ValidationResult> {
        let mut lexer = Lexer::new(ctx.input());
        let mut stack = Vec::new();

        loop {
            use TokenData as T;
            let token = match lexer.next_token() {
                Ok(t) if t.data == T::Eof => break,
                Ok(t) => t,
                Err(err) => return Ok(ValidationResult::Invalid(Some(format!("{err}"))))
            };

            match token.data {
                T::LeftParen |
                    T::LeftBrack |
                    T::LeftBrace |
                    T::For |
                    T::Try => { stack.push(token.data); },
                T::RightParen =>
                    match stack.pop() {
                        Some(T::LeftParen) => {},
                        _ => return unmatched!(token, T::LeftParen)
                    },
                T::RightBrack =>
                    match stack.pop() {
                        Some(T::LeftBrack) => {},
                        _ => return unmatched!(token, T::LeftBrack)
                    },
                T::RightBrace =>
                    match stack.pop() {
                        Some(T::LeftBrace) => {},
                        _ => return unmatched!(token, T::LeftBrace)
                    },
                T::In =>
                    match stack.pop() {
                        Some(T::For) => {},
                        _ => return unmatched!(token, T::For)
                    },
                T::Catch =>
                    match stack.pop() {
                        Some(T::Try) => {},
                        _ => return unmatched!(token, T::Try)
                    },
                _ => {}
            };
        }

        if stack.is_empty() {
            return Ok(ValidationResult::Valid(None))
        } else {
            return Ok(ValidationResult::Incomplete)
        }
    }

    fn validate_while_typing(&self) -> bool {
        true
    }
}

fn find_matching_bracket(line: &str, pos: usize) -> Option<usize> {
    if pos >= line.len() {
        return None
    }
    let c = line.as_bytes()[pos];
    let (target, fwd) = match c {
        b'(' => (b')', true),
        b')' => (b'(', false),
        b'[' => (b']', true),
        b']' => (b'[', false),
        b'{' => (b'}', true),
        b'}' => (b'{', false),
        _ => return None,
    };
    let mut depth = 0;
    let mut idx = 0;
    if fwd {
        let bytes = &line.as_bytes()[pos+1..];
        for &b in bytes {
            if b == c {
                depth += 1;
            } else if b == target {
                if depth == 0 {
                    return Some(pos + idx + 1)
                } else {
                    depth -= 1;
                }
            }
            idx += 1;
        }
    } else {
        let bytes = &line.as_bytes()[..pos];
        for &b in bytes.iter().rev() {
            if b == c {
                depth += 1;
            } else if b == target {
                if depth == 0 {
                    return Some(pos - idx - 1)
                } else {
                    depth -= 1;
                }
            }
            idx += 1;
        }
    }
    None
}

fn get_token_at(line: &str, pos: usize) -> Option<Token> {
    use TokenData as T;
    let mut lexer = Lexer::new(line);
    loop {
        match lexer.next_token() {
            Ok(Token { data: T::Eof, ..}) => return None,
            Ok(t) if t.bidx <= pos && (t.bidx + t.blen) > pos => return Some(t),
            Err(_) => return None,
            _ => continue
        }
    }
}

fn find_matching_ident(line: &str, pos: usize) -> Option<Rc<str>> {
    use TokenData as T;
    match get_token_at(line, pos) {
        Some(Token { data: T::Ident(ident), ..}) => Some(ident),
        _ => return None
    }
}

impl Highlighter for MatrixHelper {
    fn highlight<'l>(&self, line: &'l str, pos: usize) -> Cow<'l, str> {

        let matching = find_matching_bracket(line, pos);
        let ident = find_matching_ident(line, pos);

        use TokenData as T;
        let mut lexer = Lexer::new(line);
        let mut buf = String::new();
        let mut last = 0;
        loop {
            let token = match lexer.next_token() {
                Ok(t) if t.data == T::Eof => break,
                Ok(t) => t,
                Err(_) => break
            };
            let bl = token.bidx;
            let br = token.bidx + token.blen;
            buf += &line[last..bl];
            last = br;

            let color = match token.data {
                T::LeftParen |
                    T::RightParen |
                    T::LeftBrack |
                    T::RightBrack |
                    T::LeftBrace |
                    T::RightBrace
                    => {
                        match matching {
                            Some(idx) if bl == idx || bl == pos => "\x1b[33;40m",
                            _ => ""
                        }
                    }
                T::Int(_) |
                    T::True |
                    T::False |
                    T::Nil |
                    T::Float(_) |
                    T::Complex(_)
                    => "\x1b[33m",
                T::Ident(tok) => {
                    match (ident.as_ref(), lexer.peek_token()) {
                        (Some(ident), Ok(t)) if t.data == T::LeftParen && ident.as_ref() == tok.as_ref() => "\x1b[34;40m",
                        (Some(ident), _) if ident.as_ref() == tok.as_ref() => "\x1b[40m",
                        (_, Ok(t)) if t.data == T::LeftParen => "\x1b[34m",
                        _ => ""
                    }
                }
                T::Regex(_) => "\x1b[31m",
                T::String(_) => "\x1b[32m",
                T::If |
                    T::Else |
                    T::While |
                    T::Let |
                    T::Const |
                    T::Function |
                    T::Continue |
                    T::Break |
                    T::Do |
                    T::Loop |
                    T::Return |
                    T::For |
                    T::In |
                    T::Try |
                    T::Catch
                    => "\x1b[38;2;203;166;247m",
                _ => {
                    buf += &token.str;
                    continue;
                }
            };

            let clear = "\x1b[0m";

            buf += &format!("{color}{}{clear}", token.str);
        }

        buf += &line[last..];

        Cow::Owned(buf)
    }

    fn highlight_prompt<'b, 's: 'b, 'p: 'b>(
        &'s self,
        prompt: &'p str,
        default: bool,
    ) -> std::borrow::Cow<'b, str> {
        let _ = default;
        Cow::Owned(format!("\x1b[35m{prompt}\x1b[0m"))
    }

    fn highlight_hint<'h>(&self, hint: &'h str) -> Cow<'h, str> {
        Cow::Owned(format!("    \x1b[31;40m Error: \x1b[0;40m{hint} \x1b[0m"))
    }

    fn highlight_candidate<'c>(
        &self,
        candidate: &'c str,
        completion: rustyline::CompletionType,
    ) -> std::borrow::Cow<'c, str> {
        let _ = completion;
        Cow::Borrowed(candidate)
    }

    fn highlight_char(&self, line: &str, _pos: usize, forced: bool) -> bool {
        forced || !line.is_empty()
    }
}

impl Completer for MatrixHelper {
    type Candidate = Rc<str>;

    fn complete(
        &self,
        line: &str,
        pos: usize,
        ctx: &rustyline::Context<'_>,
    ) -> rustyline::Result<(usize, Vec<Self::Candidate>)> {

        let mut idx = 0;
        let mut buf = String::new();
        let mut start = 0;

        for char in line.chars() {
            if buf.is_empty() && (char.is_alphabetic() || char == '_') {
                start = idx;
                buf.push(char);
            } else if !buf.is_empty() && (char.is_alphanumeric() || char == '_') {
                buf.push(char);
            } else {
                if idx >= pos {
                    break;
                } else {
                    buf.clear();
                }
            }
            idx += char.len_utf8();
        }

        let _ = (line, pos, ctx);
        let globals = self.vm.borrow().globals();
        let names: Vec<Rc<str>> = globals
            .borrow()
            .clone()
            .into_iter()
            .filter_map(|n| if n.name.starts_with(&buf) { Some(n.name.clone()) } else { None })
            .collect();

        if buf.is_empty() {
            start = pos;
        }

        Ok((start, names))
    }

    fn update(&self, line: &mut rustyline::line_buffer::LineBuffer, start: usize, elected: &str, cl: &mut rustyline::Changeset) {
        let end = line.pos();
        line.replace(start..end, elected, cl);
    }
}