use combine::error::ParseError;
use combine::stream::state::State;
use combine::stream::Stream;
use combine::{eof, Parser};
use roc::collections::MutMap;
use roc::expr::{Expr, Pattern};
use roc::parse;
use roc::parse_state::IndentablePosition;
use roc::region::{Located, Region};
use std::hash::Hash;

pub fn loc_box<T>(val: T) -> Box<Located<T>> {
    Box::new(loc(val))
}

pub fn loc<T>(val: T) -> Located<T> {
    Located::new(val, empty_region())
}

pub fn located<T>(
    start_line: u32,
    start_col: u32,
    end_line: u32,
    end_col: u32,
    val: T,
) -> Located<T> {
    Located::new(
        val,
        Region {
            start_line,
            start_col,
            end_line,
            end_col,
        },
    )
}

pub fn empty_region() -> Region {
    Region {
        start_line: 0,
        start_col: 0,

        end_line: 0,
        end_col: 0,
    }
}

pub fn zero_loc<T>(located_val: Located<T>) -> Located<T> {
    loc(located_val.value)
}

/// Zero out the parse locations on everything in this Expr, so we can compare expected/actual without
/// having to account for that.
pub fn zero_loc_expr(expr: Expr) -> Expr {
    use roc::expr::Expr::*;

    match expr {
        Int(_) | Float(_) | EmptyStr | Str(_) | Char(_) | Var(_) | EmptyRecord | EmptyList => expr,
        InterpolatedStr(pairs, string) => InterpolatedStr(
            pairs
                .into_iter()
                .map(|(prefix, ident)| (prefix, zero_loc(ident)))
                .collect(),
            string,
        ),
        List(elems) => {
            let zeroed_elems = elems
                .into_iter()
                .map(|loc_expr| loc(zero_loc_expr(loc_expr.value)))
                .collect();

            List(zeroed_elems)
        }
        Assign(assignments, loc_ret) => {
            let zeroed_assignments = assignments
                .into_iter()
                .map(|(pattern, loc_expr)| {
                    (
                        zero_loc_pattern(pattern),
                        loc(zero_loc_expr(loc_expr.value)),
                    )
                })
                .collect();

            Assign(zeroed_assignments, loc_box(zero_loc_expr((*loc_ret).value)))
        }
        Apply(fn_expr, args) => Apply(
            loc_box(zero_loc_expr((*fn_expr).value)),
            args.into_iter()
                .map(|arg| loc(zero_loc_expr(arg.value)))
                .collect(),
        ),
        Operator(left, op, right) => Operator(
            loc_box(zero_loc_expr((*left).value)),
            zero_loc(op),
            loc_box(zero_loc_expr((*right).value)),
        ),
        Closure(patterns, body) => Closure(
            patterns.into_iter().map(zero_loc).collect(),
            loc_box(zero_loc_expr((*body).value)),
        ),
        ApplyVariant(_, None) => expr,
        ApplyVariant(name, Some(args)) => ApplyVariant(
            name,
            Some(
                args.into_iter()
                    .map(|arg| loc(zero_loc_expr(arg.value)))
                    .collect(),
            ),
        ),
        If(condition, if_true, if_false) => If(
            loc_box(zero_loc_expr((*condition).value)),
            loc_box(zero_loc_expr((*if_true).value)),
            loc_box(zero_loc_expr((*if_false).value)),
        ),
        Case(condition, branches) => Case(
            loc_box(zero_loc_expr((*condition).value)),
            branches
                .into_iter()
                .map(|(pattern, loc_expr)| {
                    (
                        zero_loc_pattern(pattern),
                        loc(zero_loc_expr(loc_expr.value)),
                    )
                })
                .collect(),
        ),
    }
}

/// Zero out the parse locations on everything in this Pattern, so we can compare expected/actual without
/// having to account for that.
pub fn zero_loc_pattern(loc_pattern: Located<Pattern>) -> Located<Pattern> {
    use roc::expr::Pattern::*;

    let pattern = loc_pattern.value;

    match pattern {
        Identifier(_) | IntLiteral(_) | FloatLiteral(_) | ExactString(_) | EmptyRecordLiteral
        | Underscore => loc(pattern),
        Variant(loc_name, None) => loc(Variant(loc(loc_name.value), None)),
        Variant(loc_name, Some(opt_located_patterns)) => loc(Variant(
            loc(loc_name.value),
            Some(
                opt_located_patterns
                    .into_iter()
                    .map(|loc_pat| zero_loc_pattern(loc_pat))
                    .collect(),
            ),
        )),
    }
}

#[allow(dead_code)] // For some reason rustc thinks this isn't used. It is, though, in test_canonicalize.rs
pub fn mut_map_from_pairs<K, V, I>(pairs: I) -> MutMap<K, V>
where
    I: IntoIterator<Item = (K, V)>,
    K: Hash + Eq,
{
    let mut answer = MutMap::default();

    for (key, value) in pairs {
        answer.insert(key, value);
    }

    answer
}

// PARSE HELPERS

#[allow(dead_code)] // For some reason rustc thinks this isn't used. It is, though, in test_parse.rs
pub fn standalone_expr<I>() -> impl Parser<Input = I, Output = Expr>
where
    I: Stream<Item = char, Position = IndentablePosition>,
    I::Error: ParseError<I::Item, I::Range, I::Position>,
{
    parse::expr().skip(eof())
}

#[allow(dead_code)] // For some reason rustc thinks this isn't used. It is, though, in test_parse.rs
pub fn parse_without_loc(actual_str: &str) -> Result<(Expr, String), String> {
    parse_standalone(actual_str).map(|(expr, leftover)| (zero_loc_expr(expr), leftover))
}

#[allow(dead_code)] // For some reason rustc thinks this isn't used. It is, though, in test_parse.rs
pub fn parse_standalone(actual_str: &str) -> Result<(Expr, String), String> {
    let parse_state: State<&str, IndentablePosition> =
        State::with_positioner(actual_str, IndentablePosition::default());

    match standalone_expr().easy_parse(parse_state) {
        Ok((expr, state)) => Ok((expr, state.input.to_string())),
        Err(errors) => Err(errors.to_string()),
    }
}