oas3-gen 0.24.0

A rust type generator for OpenAPI v3.1.x specification.
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use proc_macro2::TokenStream;
use quote::quote;

use crate::generator::ast::{FieldDef, StructDef, StructKind, TypeRef, tokens::ConstToken};

pub(crate) struct HeaderMapGenerator<'a> {
  def: &'a StructDef,
}

impl<'a> HeaderMapGenerator<'a> {
  pub(crate) fn new(def: &'a StructDef) -> Self {
    Self { def }
  }

  pub(crate) fn should_generate(&self) -> bool {
    matches!(self.def.kind, StructKind::HeaderParams) && !self.def.fields.is_empty()
  }

  pub(crate) fn emit(&self) -> TokenStream {
    if !self.should_generate() {
      return quote! {};
    }

    let struct_name = &self.def.name;
    let field_count = self.def.fields.len();
    let insertions = self.generate_field_insertions();

    quote! {
      impl core::convert::TryFrom<&#struct_name> for http::HeaderMap {
        type Error = http::header::InvalidHeaderValue;

        fn try_from(headers: &#struct_name) -> core::result::Result<Self, Self::Error> {
          let mut map = http::HeaderMap::with_capacity(#field_count);
          #insertions
          Ok(map)
        }
      }

      impl core::convert::TryFrom<#struct_name> for http::HeaderMap {
        type Error = http::header::InvalidHeaderValue;

        fn try_from(headers: #struct_name) -> core::result::Result<Self, Self::Error> {
          http::HeaderMap::try_from(&headers)
        }
      }
    }
  }

  fn generate_field_insertions(&self) -> TokenStream {
    let insertions: Vec<TokenStream> = self.def.fields.iter().map(Self::generate_field_insertion).collect();

    quote! { #(#insertions)* }
  }

  fn generate_field_insertion(field: &FieldDef) -> TokenStream {
    let field_name = &field.name;
    let Some(original_name) = &field.original_name else {
      return quote! {};
    };

    let header_const = ConstToken::from_raw(original_name);
    let ty = &field.rust_type;

    if field.is_required() {
      let header_value = Self::header_value_expr(ty, quote! { &headers.#field_name });
      quote! {
        let header_value = http::HeaderValue::try_from(#header_value)?;
        map.insert(#header_const, header_value);
      }
    } else {
      let header_value = Self::header_value_expr(ty, quote! { value });
      quote! {
        if let Some(value) = &headers.#field_name {
          let header_value = http::HeaderValue::try_from(#header_value)?;
          map.insert(#header_const, header_value);
        }
      }
    }
  }

  fn header_value_expr(ty: &TypeRef, accessor: TokenStream) -> TokenStream {
    if ty.is_string_like() {
      accessor
    } else if ty.is_array {
      quote! { #accessor.iter().map(|v| v.to_string()).collect::<Vec<_>>().join(",") }
    } else {
      quote! { #accessor.to_string() }
    }
  }
}