use nom::{
    branch::alt,
    combinator::map,
    error::context,
    multi::{many1, separated_list1},
    sequence::{delimited, separated_pair, tuple},
};

use crate::parser::{
    assign_statement, expression,
    expression::{expression, Expression},
    tokens::{token, TokenKind as tk, TokenSpan},
    Assign, IResult, Span,
};

#[derive(Debug)]
pub struct ProcBlock<'a> {
    pub net: Span<'a>,
    pub items: Vec<ProcStatement<'a>>,
}

#[derive(Debug)]
pub enum ProcStatement<'a> {
    IfElse(IfElseBlock),
    Assign(Assign<'a>),
    Match(MatchBlock<'a>),
    Block(Vec<ProcStatement<'a>>),
}

// TODO: postponed because annoying to implement
#[derive(Debug)]
pub struct IfElseBlock {}

#[derive(Debug)]
pub struct MatchBlock<'a> {
    pub expr: Expression<'a>,
    pub arms: Vec<(Expression<'a>, ProcStatement<'a>)>,
}

fn match_arm(input: TokenSpan) -> IResult<TokenSpan, (Expression, ProcStatement)> {
    separated_pair(expression, token(tk::FatArrow), proc_statement)(input)
}

fn match_block(input: TokenSpan) -> IResult<TokenSpan, MatchBlock> {
    context(
        "match block",
        map(
            tuple((
                token(tk::Match),
                delimited(token(tk::LParen), expression, token(tk::RParen)),
                delimited(
                    token(tk::LBrace),
                    separated_list1(token(tk::Comma), match_arm),
                    token(tk::RBrace),
                ),
            )),
            |(_, expr, arms)| MatchBlock { expr, arms },
        ),
    )(input)
}

fn statement_block(input: TokenSpan) -> IResult<TokenSpan, Vec<ProcStatement>> {
    delimited(
        token(tk::LBrace),
        separated_list1(token(tk::Semicolon), proc_statement),
        token(tk::RBrace),
    )(input)
}

/// parse a statement that is valid inside a proc block
fn proc_statement(input: TokenSpan) -> IResult<TokenSpan, ProcStatement> {
    alt((
        map(match_block, ProcStatement::Match),
        map(statement_block, ProcStatement::Block),
        map(assign_statement, ProcStatement::Assign),
    ))(input)
}

pub fn proc_block(input: TokenSpan) -> IResult<TokenSpan, ProcBlock> {
    context(
        "proc block",
        map(
            tuple((
                token(tk::Proc),
                delimited(token(tk::LParen), token(tk::Ident), token(tk::RParen)),
                delimited(token(tk::LBrace), many1(proc_statement), token(tk::RBrace)),
            )),
            |(_, net, items)| ProcBlock {
                net: net.span(),
                items,
            },
        ),
    )(input)
}