use crate::{
    error::{ErrorKind, KabelError},
    lexer::{Token, TokenType},
};

pub struct Parser {
    input: Vec<Token>,
    text: String,
    //start: usize,
    current: usize,
    token: Token,
    pub errors: Vec<KabelError>,
}

impl Parser {
    pub fn new(text: String, input: Vec<Token>) -> Self {
        Self {
            input: input.clone(),
            text,
            //start: 0,
            current: 0,
            token: input[0].clone(),
            errors: Vec::new(),
        }
    }

    pub fn program(&mut self) -> AST {
        let mut program = Vec::new();
        loop {
            if self.current >= self.input.len() {
                break;
            }
            match self.expression() {
                Ok(ast) => program.push(ast),
                Err(e) => self.errors.push(e),
            }
        }
        AST {
            ast_type: ASTType::Program(program),
            start: 0,
            end: 0,
            line: 0,
            column: 0,
        }
    }

    pub fn expression(&mut self) -> Result<AST, KabelError> {
        let equality = self.equality()?;
        Ok(equality)
    }

    pub fn equality(&mut self) -> Result<AST, KabelError> {
        let mut left = self.comparison()?;

        while self.current < self.input.len()
            && (self.peek()?.token_type == TokenType::EqualEqual
                || self.peek()?.token_type == TokenType::BangEqual)
        {
            let binop = self.read_token()?;
            let right = self.comparison()?;
            if binop.token_type == TokenType::EqualEqual {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Eq,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            } else {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Ne,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            }
        }

        Ok(left)
    }

    pub fn comparison(&mut self) -> Result<AST, KabelError> {
        let mut left = self.term()?;

        while self.current < self.input.len()
            && (self.peek()?.token_type == TokenType::Less
                || self.peek()?.token_type == TokenType::LessEqual
                || self.peek()?.token_type == TokenType::Greater
                || self.peek()?.token_type == TokenType::GreaterEqual)
        {
            let binop = self.read_token()?;
            let right = self.term()?;
            if binop.token_type == TokenType::Less {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Ls,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            } else if binop.token_type == TokenType::LessEqual {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Le,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            } else if binop.token_type == TokenType::Greater {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Gr,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            } else {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Ge,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            }
        }

        Ok(left)
    }

    pub fn term(&mut self) -> Result<AST, KabelError> {
        let mut left = self.factor()?;

        while self.current < self.input.len()
            && (self.peek()?.token_type == TokenType::Plus
                || self.peek()?.token_type == TokenType::Minus)
        {
            let binop = self.read_token()?;
            let right = self.factor()?;

            if binop.token_type == TokenType::Plus {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Add,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            } else {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Sub,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            }
        }
        Ok(left)
    }
    pub fn factor(&mut self) -> Result<AST, KabelError> {
        let mut left = self.unary()?;

        while self.current < self.input.len()
            && (self.peek()?.token_type == TokenType::Star
                || self.peek()?.token_type == TokenType::Slash)
        {
            let binop = self.read_token()?;
            let right = self.unary()?;

            if binop.token_type == TokenType::Star {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Mul,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            } else {
                left = AST {
                    ast_type: ASTType::Binary(
                        Box::new(left.clone()),
                        BinOp::Div,
                        Box::new(right.clone()),
                    ),
                    start: left.start,
                    end: right.end,
                    line: left.line,
                    column: left.column,
                };
            }
        }
        Ok(left)
    }
    pub fn unary(&mut self) -> Result<AST, KabelError> {
        if let TokenType::Bang | TokenType::Minus = self.peek()?.token_type {
            let token = self.read_token()?;
            let unary = self.unary()?;
            if token.token_type == TokenType::Bang {
                return Ok(AST {
                    ast_type: ASTType::Unary(UnOp::Not, Box::new(unary.clone())),
                    start: token.start,
                    end: unary.end,
                    line: token.line,
                    column: token.column,
                });
            } else {
                return Ok(AST {
                    ast_type: ASTType::Unary(UnOp::Neg, Box::new(unary.clone())),
                    start: token.start,
                    end: unary.end,
                    line: token.line,
                    column: token.column,
                });
            }
        }

        Ok(self.primary()?)
    }
    pub fn primary(&mut self) -> Result<AST, KabelError> {
        let token = self.read_token()?;

        match token.token_type {
            TokenType::Ident(ident) => {
                return Ok(AST {
                    ast_type: ASTType::Ident(ident),
                    start: token.start,
                    end: token.end,
                    line: token.line,
                    column: token.column,
                });
            }
            TokenType::Num(num) => {
                return Ok(AST {
                    ast_type: ASTType::Num(num),
                    start: token.start,
                    end: token.end,
                    line: token.line,
                    column: token.column,
                });
            }
            TokenType::Str(string) => {
                return Ok(AST {
                    ast_type: ASTType::Str(string),
                    start: token.start,
                    end: token.end,
                    line: token.line,
                    column: token.column,
                });
            }
            TokenType::LeftParen => {
                return Ok(self.group(token)?);
            }
            _ => {
                return Err(KabelError::new(
                    ErrorKind::UnexpectedToken,
                    format!(
                        "Unexpected token {}",
                        self.text[token.start..token.end].to_string()
                    ),
                    token.line,
                    token.column,
                    self.text[token.line_start..token.end].to_string(),
                ));
            }
        }
    }
    pub fn group(&mut self, left_paren: Token) -> Result<AST, KabelError> {
        let expr = self.expression()?;
        let right_paren = self.peek();
        if let Ok(right_paren) = right_paren {
            if right_paren.token_type != TokenType::RightParen {
                return Err(KabelError::new(
                    ErrorKind::MissingDelimiter,
                    "Missing right parenthesis".to_string(),
                    right_paren.line,
                    right_paren.column,
                    self.text[left_paren.start..right_paren.end].to_string(),
                ));
            }
            self.read_token()?;
            return Ok(AST {
                ast_type: ASTType::Group(Box::new(expr.clone())),
                start: left_paren.start,
                end: right_paren.end,
                line: left_paren.line,
                column: left_paren.column,
            });
        }
        if let Err(e) = right_paren {
            return Err(KabelError::new(
                ErrorKind::MissingDelimiter,
                "Missing right parenthesis".to_string(),
                e.line,
                e.column,
                self.text[left_paren.line_start..expr.end].to_string(),
            ));
        }
        unreachable!();
    }

    pub fn read_token(&mut self) -> Result<Token, KabelError> {
        if self.current >= self.input.len() {
            let last_token = self.input[self.input.len() - 1].clone();
            return Err(KabelError::new(
                ErrorKind::UnexpectedEof,
                "Unexpected end of file".to_string(),
                last_token.line,
                last_token.column,
                self.text[last_token.line_start..last_token.end].to_string(),
            ));
        }
        self.token = self.input[self.current].clone();
        self.current += 1;
        return Ok(self.token.clone());
    }
    pub fn peek(&mut self) -> Result<Token, KabelError> {
        if self.current >= self.input.len() {
            let last_token = self.input[self.input.len() - 1].clone();
            return Err(KabelError::new(
                ErrorKind::UnexpectedEof,
                "Unexpected end of file".to_string(),
                last_token.line,
                last_token.column,
                self.text[last_token.line_start..last_token.end].to_string(),
            ));
        }
        return Ok(self.input[self.current].clone());
    }
}

#[derive(Debug, Clone)]
pub struct AST {
    pub ast_type: ASTType,
    pub start: usize,
    pub end: usize,
    pub line: usize,
    pub column: usize,
}

#[derive(Debug, Clone)]
pub enum ASTType {
    Program(Vec<AST>),

    Binary(Box<AST>, BinOp, Box<AST>),
    Unary(UnOp, Box<AST>),

    Group(Box<AST>),
    Ident(String),
    Num(f32),
    Str(String),
}

#[derive(Debug, Clone, Copy)]
pub enum BinOp {
    Add,
    Sub,
    Mul,
    Div,
    Eq,
    Ne,
    Gr,
    Ge,
    Ls,
    Le,
}

#[derive(Debug, Clone, Copy)]
pub enum UnOp {
    Not,
    Neg,
}