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

/// Call to a filter identified by a name type `N` with arguments of type `A`.
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Clone, Debug)]
pub struct Call<A, N = String> {
    /// Name of the filter, e.g. `map`
    pub name: N,
    /// Arguments of the filter, e.g. `["f"]`
    pub args: Vec<A>,
}

impl<A, N> Call<A, N> {
    /// Apply a function to the call arguments.
    pub fn map_args<B>(self, f: impl FnMut(A) -> B) -> Call<B, N> {
        Call {
            name: self.name,
            args: self.args.into_iter().map(f).collect(),
        }
    }
}

/// A definition, such as `def map(f): [.[] | f];`.
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Debug)]
pub struct Def {
    /// left-hand side, i.e. what shall be defined, e.g. `map(f)`
    pub lhs: Call<Arg>,
    /// right-hand side, i.e. what the LHS should be defined as, e.g. `[.[] | f]`
    pub rhs: Main,
}

/// Argument of a definition, such as `$v` or `f` in `def foo($v; f): ...`.
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Debug)]
pub struct Arg {
    name: String,
    var: bool,
}

impl Arg {
    /// Create a variable argument with given name (without leading "$").
    pub fn new_var(name: String) -> Self {
        Self { name, var: true }
    }

    /// Create a filter argument with given name.
    pub fn new_filter(name: String) -> Self {
        Self { name, var: false }
    }

    /// True if the argument is a variable.
    pub fn is_var(&self) -> bool {
        self.var
    }

    /// If the argument is a variable, return its name without leading "$", otherwise `None`.
    pub fn get_var(&self) -> Option<&str> {
        self.var.then_some(&*self.name)
    }

    /// If the argument is a filter, return its name, otherwise `None`.
    pub fn get_filter(&self) -> Option<&str> {
        (!self.var).then_some(&*self.name)
    }
}

/// (Potentially empty) sequence of definitions, followed by a filter.
#[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
#[derive(Debug)]
pub struct Main {
    /// Definitions at the top of the filter
    pub defs: Vec<Def>,
    /// Body of the filter, e.g. `[.[] | f`.
    pub body: Spanned<Filter>,
}