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use crate::filter::{args, filter, Filter};
use crate::{Spanned, Token};
use alloc::{string::String, vec::Vec};
use chumsky::prelude::*;
#[cfg(feature = "serde")]
use serde::{Deserialize, Serialize};

/// A definition, such as `def map(f): [.[] | f];`.
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Debug)]
pub struct Def {
    /// Name of the filter, e.g. `map`
    pub name: String,
    /// Arguments of the filter, e.g. `["f"]`
    pub args: Vec<String>,
    /// Body of the filter, e.g. `[.[] | f`.
    pub body: Spanned<Filter>,
}

/// (Potentially empty) sequence of definitions, followed by a filter.
pub type Main = (Vec<Def>, Spanned<Filter>);

fn def() -> impl Parser<Token, Def, Error = Simple<Token>> + Clone {
    let ident = filter_map(|span, tok| match tok {
        Token::Ident(ident) => Ok(ident),
        _ => Err(Simple::expected_input_found(span, Vec::new(), Some(tok))),
    });

    just(Token::Def)
        .ignore_then(ident.labelled("filter name"))
        .then(args(ident).labelled("filter args"))
        .then_ignore(just(Token::Ctrl(':')))
        .then(filter())
        .then_ignore(just(Token::Ctrl(';')))
        .map(|((name, args), body)| Def { name, args, body })
        .labelled("definition")
}

/// Parser for a sequence of definitions.
pub fn defs() -> impl Parser<Token, Vec<Def>, Error = Simple<Token>> + Clone {
    def().repeated().collect()
}

/// Parser for a (potentially empty) sequence of definitions, followed by a filter.
pub fn main() -> impl Parser<Token, Main, Error = Simple<Token>> + Clone {
    defs().then(filter())
}