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use crate::meta_type::MetaType;
use crate::{de::Deserialize, ser::Serialize};
use crate::{AlgebraicType, WithTypespace};

/// A factor / element of a product type.
///
/// An element consist of an optional name and a type.
///
/// NOTE: Each element has an implicit element tag based on its order.
/// Uniquely identifies an element similarly to protobuf tags.
#[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Serialize, Deserialize)]
#[sats(crate = crate)]
pub struct ProductTypeElement {
    /// The name of the field / element.
    ///
    /// As our type system is structural,
    /// a type like `{ foo: U8 }`, where `foo: U8` is the `ProductTypeElement`,
    /// is inequal to `{ bar: U8 }`, although their `algebraic_type`s (`U8`) match.
    pub name: Option<String>,
    /// The type of the element.
    ///
    /// Only values of this type can be stored in the element.
    pub algebraic_type: AlgebraicType,
}

impl ProductTypeElement {
    /// Returns an element with the given `name` and `algebraic_type`.
    pub const fn new(algebraic_type: AlgebraicType, name: Option<String>) -> Self {
        Self { algebraic_type, name }
    }

    /// Returns a named element with `name` and `algebraic_type`.
    pub fn new_named(algebraic_type: AlgebraicType, name: impl Into<String>) -> Self {
        Self::new(algebraic_type, Some(name.into()))
    }

    /// Returns the name of the field.
    pub fn name(&self) -> Option<&str> {
        self.name.as_deref()
    }

    /// Returns whether the field has the given name.
    pub fn has_name(&self, name: &str) -> bool {
        self.name() == Some(name)
    }
}

impl MetaType for ProductTypeElement {
    fn meta_type() -> AlgebraicType {
        AlgebraicType::product([
            ("name", AlgebraicType::option(AlgebraicType::String)),
            ("algebraic_type", AlgebraicType::ZERO_REF),
        ])
    }
}

impl From<AlgebraicType> for ProductTypeElement {
    fn from(value: AlgebraicType) -> Self {
        ProductTypeElement::new(value, None)
    }
}

impl<'a> WithTypespace<'a, ProductTypeElement> {
    #[inline]
    pub fn algebraic_type(&self) -> WithTypespace<'a, AlgebraicType> {
        self.with(&self.ty().algebraic_type)
    }
}