use crate::ast::*;
use crate::parser::*;
use nom::branch::*;
use nom::combinator::*;
use nom::multi::*;
use nom::sequence::*;
use nom::IResult;

// -----------------------------------------------------------------------------

#[derive(Debug)]
pub struct ConditionalStatement<'a> {
    pub nodes: (
        Option<UniquePriority<'a>>,
        Symbol<'a>,
        Paren<'a, CondPredicate<'a>>,
        StatementOrNull<'a>,
        Vec<(
            Symbol<'a>,
            Symbol<'a>,
            Paren<'a, CondPredicate<'a>>,
            StatementOrNull<'a>,
        )>,
        Option<(Symbol<'a>, StatementOrNull<'a>)>,
    ),
}

#[derive(Debug, Node)]
pub enum UniquePriority<'a> {
    Unique(Symbol<'a>),
    Unique0(Symbol<'a>),
    Priority(Symbol<'a>),
}

#[derive(Debug)]
pub struct CondPredicate<'a> {
    pub nodes: (List<Symbol<'a>, ExpressionOrCondPattern<'a>>,),
}

#[derive(Debug)]
pub enum ExpressionOrCondPattern<'a> {
    Expression(Expression<'a>),
    CondPattern(CondPattern<'a>),
}

#[derive(Debug)]
pub struct CondPattern<'a> {
    pub nodes: (Expression<'a>, Symbol<'a>, Pattern<'a>),
}

// -----------------------------------------------------------------------------

pub fn conditional_statement(s: Span) -> IResult<Span, ConditionalStatement> {
    let (s, a) = opt(unique_priority)(s)?;
    let (s, b) = symbol("if")(s)?;
    let (s, c) = paren(cond_predicate)(s)?;
    let (s, d) = statement_or_null(s)?;
    let (s, e) = many0(tuple((
        symbol("else"),
        symbol("if"),
        paren(cond_predicate),
        statement_or_null,
    )))(s)?;
    let (s, f) = opt(pair(symbol("else"), statement_or_null))(s)?;

    Ok((
        s,
        ConditionalStatement {
            nodes: (a, b, c, d, e, f),
        },
    ))
}

pub fn unique_priority(s: Span) -> IResult<Span, UniquePriority> {
    alt((
        map(symbol("unique0"), |x| UniquePriority::Unique0(x)),
        map(symbol("unique"), |x| UniquePriority::Unique(x)),
        map(symbol("priority"), |x| UniquePriority::Priority(x)),
    ))(s)
}

pub fn cond_predicate(s: Span) -> IResult<Span, CondPredicate> {
    let (s, a) = list(symbol("&&&"), expression_or_cond_pattern)(s)?;
    Ok((s, CondPredicate { nodes: (a,) }))
}

pub fn expression_or_cond_pattern(s: Span) -> IResult<Span, ExpressionOrCondPattern> {
    alt((
        map(expression, |x| ExpressionOrCondPattern::Expression(x)),
        map(cond_pattern, |x| ExpressionOrCondPattern::CondPattern(x)),
    ))(s)
}

pub fn cond_pattern(s: Span) -> IResult<Span, CondPattern> {
    let (s, a) = expression(s)?;
    let (s, b) = symbol("matches")(s)?;
    let (s, c) = pattern(s)?;
    Ok((s, CondPattern { nodes: (a, b, c) }))
}