use std::collections::{HashMap, HashSet};

use crate::ast::*;
use crate::tokeniser::Keyword;
use crate::tokeniser::Token;

fn parse_math(tokens: &Vec<Token>) -> ValueNode {
    let mut prioritizing_order: HashMap<i64, HashSet<Token>> = HashMap::new();
    prioritizing_order.insert(0, HashSet::from([Token::Plus, Token::Minus]));

    let mut ordered_binops: Vec<Token> = Vec::new();
    let mut ordered_binops_indexes: Vec<usize> = Vec::new();

    if tokens.len() == 1 {
        return match &tokens[0] {
            Token::Number(n) => ValueNode::Literal(Literal::Int(n.parse::<i64>().unwrap())),
            Token::Identifier(identifier) => ValueNode::Variable(identifier.to_owned()),
            _ => todo!(),
        };
    }

    for j in prioritizing_order.keys() {
        let mut i = 0;
        let current_order_binops = prioritizing_order.get(j).unwrap();

        while i < tokens.len() {
            for binop in current_order_binops {
                if &tokens[i] == binop {
                    ordered_binops.push(binop.to_owned());
                    ordered_binops_indexes.push(i);
                }
            }

            i += 1;
        }
    }

    let binop = ordered_binops.pop().unwrap();
    let binop_index = ordered_binops_indexes.pop().unwrap();

    let mut a: Vec<Token> = Vec::new();
    let mut b: Vec<Token> = Vec::new();

    let mut i = 0;
    while i < tokens.len() {
        if i < binop_index {
            a.push(tokens[i].clone());
        }
        if i > binop_index {
            b.push(tokens[i].clone());
        }

        i += 1;
    }

    return match binop {
        Token::Plus => ValueNode::Operator(Operator::Add(
            Box::new(parse_math(&a)),
            Box::new(parse_math(&b)),
        )),
        Token::Minus => ValueNode::Operator(Operator::Sub(
            Box::new(parse_math(&a)),
            Box::new(parse_math(&b)),
        )),
        _ => todo!(),
    };
}

fn parse_basic(tokens: &Vec<Token>, i: &mut usize) -> Expression {
    let literal = match &tokens[*i] {
        Token::Identifier(identifier) => Expression::Variable(identifier.to_owned()),
        Token::Number(number) => Expression::Literal(Literal::Int(number.parse::<i64>().unwrap())),
        _ => todo!(),
    };
    *i += 1;
    literal
}

fn parse_grouping(tokens: &Vec<Token>, i: &mut usize) -> Expression {
    match &tokens[*i] {
        Token::OpenParanthesis => {
            *i += 1;
        }
        _ => todo!(),
    };

    let inner_expression = parse_expression(tokens, i);

    match &tokens[*i] {
        Token::CloseParanthesis => {}
        _ => todo!(),
    };

    inner_expression
}

// TODO: replace parse_math with this recursive function
pub fn parse_expression(tokens: &Vec<Token>, i: &mut usize) -> Expression {
    #[derive(Debug)]
    enum OpExpr {
        Expression(Expression),
        BinOp(BinOp),
        Unary(Unary),
    }

    let mut in_expressions_and_operators: Vec<OpExpr> = Vec::new();

    loop {
        in_expressions_and_operators.push(match &tokens[*i] {
            Token::OpenParanthesis => OpExpr::Expression(parse_grouping(tokens, i)),
            Token::Plus => {
                *i += 1;
                OpExpr::BinOp(BinOp::Plus)
            }
            Token::Minus => {
                *i += 1;
                OpExpr::BinOp(BinOp::Minus)
            }
            Token::Ampersand => {
                *i += 1;
                OpExpr::Unary(Unary::ValueFrom)
            }
            Token::Star => {
                *i += 1;
                OpExpr::Unary(Unary::PointerTo)
            }
            Token::Number(_) => OpExpr::Expression(parse_basic(tokens, i)),
            _other => break,
        });
    }
    dbg!(in_expressions_and_operators);
    Expression::Variable("a".to_string())
}

fn parse_statements(tokens: &Vec<Token>, i: &mut usize) -> Vec<Statement> {
    dbg!(&i);
    let mut statements = Vec::new();
    while *i < tokens.len() {
        statements.push(match &tokens[*i] {
            Token::OpenSquiglyBracket => {
                *i += 1;
                let statements = parse_statements(tokens, i);
                Statement::Scope(statements)
            }
            Token::Keyword(Keyword::Let) => {
                *i += 1;
                let name = match tokens[*i].clone() {
                    Token::Identifier(identifier) => identifier,
                    _ => todo!(),
                };

                *i += 1;
                match tokens[*i].clone() {
                    Token::Equals => {}
                    _ => todo!(),
                };

                *i += 1;

                let mut declaration_tokens: Vec<Token> = Vec::new();
                while tokens[*i] != Token::Semi {
                    declaration_tokens.push(tokens[*i].clone());
                    *i += 1;
                }
                Statement::VariableDeclaration(name, parse_math(&declaration_tokens))
            }
            Token::Keyword(Keyword::Assign) => {
                *i += 1;
                let name = match tokens[*i].clone() {
                    Token::Identifier(identifier) => identifier,
                    _ => todo!(),
                };

                *i += 1;
                match tokens[*i].clone() {
                    Token::Equals => {}
                    _ => todo!(),
                };

                *i += 1;

                let mut declaration_tokens: Vec<Token> = Vec::new();
                while tokens[*i] != Token::Semi {
                    declaration_tokens.push(tokens[*i].clone());
                    *i += 1;
                }
                Statement::VariableAssignment(name, parse_math(&declaration_tokens))
            }
            Token::Identifier(identifier) => {
                *i += 1;

                let mut declaration_tokens: Vec<Vec<Token>> = Vec::new();

                *i += 1;
                while tokens[*i] != Token::CloseParanthesis {
                    let mut argument_tokens: Vec<Token> = Vec::new();
                    while tokens[*i] != Token::Comma {
                        argument_tokens.push(tokens[*i].clone());
                        *i += 1;
                    }
                    declaration_tokens.push(argument_tokens);
                    *i += 1;
                }

                *i += 1;

                let mut arguments: Vec<ValueNode> = Vec::new();

                for token_vec in &declaration_tokens {
                    if token_vec == &Vec::new() {
                        continue;
                    }
                    arguments.push(parse_math(token_vec));
                }

                Statement::FunctionCall(identifier.to_owned(), arguments)
            }
            Token::CloseSquiglyBracket => {
                *i += 1;
                return statements;
            }
            Token::Semi => {
                *i += 1;
                continue;
            }
            _other => {
                dbg!(_other);
                dbg!(i);
                todo!()
            }
        });
    }
    *i += 1;
    statements
}

pub fn parse_arguments(tokens: &Vec<Token>, i: &mut usize) -> Vec<String> {
    let mut argument_variables = Vec::new();
    while tokens[*i] != Token::OpenSquiglyBracket {
        match &tokens[*i] {
            Token::Identifier(identifier) => argument_variables.push(identifier.to_owned()),
            Token::OpenSquiglyBracket => {}
            _other => todo!(),
        }
        *i += 1;
    }
    argument_variables
}

pub fn ast(tokens: Vec<Token>) -> Vec<Function> {
    let mut functions: Vec<Function> = Vec::new();

    let mut i = 0;
    while i < tokens.len() {
        match &tokens[i] {
            Token::Keyword(Keyword::Function) => {
                i += 1;

                let name = match &tokens[i] {
                    Token::Identifier(identifier) => identifier,
                    _ => todo!(),
                }
                .to_owned();
                i += 1;

                let arguments = parse_arguments(&tokens, &mut i);

                i += 1;
                let statements = parse_statements(&tokens, &mut i);

                let statement = Statement::Scope(statements);

                functions.push(Function::new(name, arguments, statement));
            }
            _other => {
                dbg!(&functions);
                dbg!(i);
                dbg!(_other);
                todo!();
            }
        };

        i += 1;
    }

    functions
}