use super::{Expectable, Parser, Position, SyntaxError};

type Ident = String;

#[derive(Debug, Clone)]
pub struct ParsedReid(pub Expression);

#[derive(Debug, Clone)]
pub enum Statement {
    LetStatement(Position, Ident, Box<Expression>),
    ExprStatement(Position, Expression),
}

impl Statement {
    pub fn parse(parser: &mut Parser) -> Result<Statement, SyntaxError> {
        let pos = parser.pos();

        if parser.expect_static("let").get().is_some() {
            let ident = parser
                .expect_ident()
                .get_or(SyntaxError::ExpectedIdent(pos))?;
            parser
                .expect_static("=")
                .get_or(SyntaxError::ExpectedToken(pos, '='))?;
            match Expression::parse(parser) {
                Ok(expr) => {
                    parser
                        .expect_static(";")
                        .get_or(SyntaxError::ExpectedToken(pos, ';'))?;
                    Ok(Statement::LetStatement(pos, ident, Box::new(expr)))
                }
                Err(err) => Err(SyntaxError::ExpectedExpression(pos, Some(Box::new(err)))),
            }
        } else {
            match Expression::parse(parser) {
                Ok(expr) => {
                    let statement = Statement::ExprStatement(pos, expr);
                    parser
                        .expect_static(";")
                        .get_or(SyntaxError::ExpectedToken(pos, ';'))?;
                    Ok(statement)
                }
                Err(err) => Err(SyntaxError::ExpectedStatement(pos, Some(Box::new(err)))),
            }
        }
    }
}

#[derive(Debug, Clone)]
pub enum Expression {
    BlockExpr(Position, Vec<Statement>),
    FunctionCall(Position, Ident, Vec<Expression>),
    ValueRef(Position, Pattern),
}

impl Expression {
    pub fn parse(parser: &mut Parser) -> Result<Expression, SyntaxError> {
        let begin_pos = parser.pos();

        if parser.expect_static("{").get().is_some() {
            let mut statement_list = Vec::new();
            while {
                match Statement::parse(parser) {
                    Ok(exp) => {
                        statement_list.push(exp);
                        true
                    }
                    Err(_) => false,
                }
            } {}
            if parser.expect_static("}").get().is_some() {
                Ok(Expression::BlockExpr(begin_pos, statement_list))
            } else {
                Err(SyntaxError::ExpectedToken(parser.pos(), '}'))
            }
        } else if let Some(texts) = parser.expect_ident().and(Expectable::Static("(")).get() {
            let pos = parser.pos();
            let name = texts.get(0).unwrap();
            let mut arg_list = Vec::new();
            while {
                match Expression::parse(parser) {
                    Ok(exp) => {
                        arg_list.push(exp);
                        parser.expect_static(",").get().is_some()
                    }
                    Err(err) => {
                        if arg_list.is_empty() {
                            false
                        } else {
                            return Err(err);
                        }
                    }
                }
            } {}
            parser
                .expect_static(")")
                .get_or(SyntaxError::ExpectedToken(pos, ')'))?;
            Ok(Expression::FunctionCall(pos, name.clone(), arg_list))
        } else if let Ok(pattern) = Pattern::parse(parser) {
            Ok(Expression::ValueRef(begin_pos, pattern))
        } else {
            Err(SyntaxError::ExpectedExpression(begin_pos, None))
        }
    }
}

#[derive(Debug, Clone)]
pub enum Pattern {
    IdentPattern(Position, Ident),
    LiteralPattern(Position, LiteralPattern),
}

impl Pattern {
    fn parse(parser: &mut Parser) -> Result<Pattern, SyntaxError> {
        let pos = parser.pos();
        if let Some(string) = parser.expect_string_lit().get() {
            Ok(Pattern::LiteralPattern(
                pos,
                LiteralPattern::StringLit(string),
            ))
        } else if let Some(int) = parser.expect_numeral_lit().get() {
            Ok(Pattern::LiteralPattern(
                pos,
                LiteralPattern::Integer32Lit(int),
            ))
        } else if let Some(ident) = parser.expect_ident().get() {
            Ok(Pattern::IdentPattern(pos, ident))
        } else {
            Err(SyntaxError::ExpectedPattern(pos))
        }
    }
}

#[derive(Debug, Clone)]
pub enum LiteralPattern {
    StringLit(String),
    Integer32Lit(String),
}