icydb-model-macros 0.291.0

//! Module: imp::field_walk
//! Responsibility: generated implementation tokens.
//! Does not own: runtime trait semantics.
//! Boundary: parsed nodes to impl tokens.

use crate::prelude::*;

///
/// FieldWalkBinding
///
/// Shared derive-side lowering for one entity or record field walk step.
/// This keeps field-name, path-segment, and member-access expansion under one
/// owner so visit/normalize/validate generation do not each rebuild that shape
/// independently.
///

pub(crate) struct FieldWalkBinding {
    ident: Ident,
    name: String,
}

impl FieldWalkBinding {
    /// Build one field-walk binding from one schema field.
    #[must_use]
    pub fn from_field(field: &Field) -> Self {
        Self {
            ident: field.name.clone(),
            name: field.name.to_string(),
        }
    }

    /// Borrow this field by immutable reference from the provided receiver.
    #[must_use]
    pub fn member_ref_from(&self, receiver: TokenStream) -> TokenStream {
        let ident = &self.ident;

        quote!(&#receiver.#ident)
    }

    /// Borrow this field by mutable reference from the provided receiver.
    #[must_use]
    pub fn member_mut_from(&self, receiver: TokenStream) -> TokenStream {
        let ident = &self.ident;

        quote!(&mut #receiver.#ident)
    }

    /// Emit one field path-segment token for visitor issue reporting.
    #[must_use]
    pub fn path_segment(&self, paths: &CratePaths) -> TokenStream {
        let model = &paths.model;
        let name = &self.name;

        quote!(#model::visitor::PathSegment::Field(#name))
    }

    /// Return the stable field name string used by visitor traversal.
    #[must_use]
    pub fn field_name(&self) -> &str {
        &self.name
    }

    /// Return one stable generated helper name for immutable traversal.
    #[must_use]
    pub fn visit_fn_ident(&self) -> Ident {
        format_ident!("__visit_field_{}", self.ident)
    }

    /// Return one stable generated helper name for mutable traversal.
    #[must_use]
    pub fn visit_mut_fn_ident(&self) -> Ident {
        format_ident!("__visit_field_{}_mut", self.ident)
    }

    /// Return one stable generated helper name for normalization dispatch.
    #[must_use]
    pub fn normalize_fn_ident(&self) -> Ident {
        format_ident!("__normalize_field_{}", self.ident)
    }

    /// Return one stable generated helper name for validation dispatch.
    #[must_use]
    pub fn validate_fn_ident(&self) -> Ident {
        format_ident!("__validate_field_{}", self.ident)
    }
}

/// Lower one entity or record field list into reusable field-walk bindings.
#[must_use]
pub(crate) fn field_walk_bindings(fields: &FieldList) -> Vec<FieldWalkBinding> {
    fields.iter().map(FieldWalkBinding::from_field).collect()
}

/// Applies cardinality (One / Opt / Many)
pub(crate) fn cardinality_wrapper(
    card: Cardinality,
    rules: Vec<TokenStream>,
    var_expr: TokenStream,
) -> Option<TokenStream> {
    if rules.is_empty() {
        return None;
    }

    let body = quote! { #(#rules)* };

    let tokens = match card {
        Cardinality::One => quote! {
            let v = #var_expr;
            #body
        },
        Cardinality::Opt => quote! {
            if let ::core::option::Option::Some(v) = #var_expr {
                #body
            }
        },
        Cardinality::Many => {
            let item = format_ident!("__item");
            quote! {
                for #item in #var_expr {
                    let v = #item;
                    #body
                }
            }
        }
    };

    Some(tokens)
}