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use crate::compiler::message::{Field, FieldType, Message, Referenced};

use crate::compiler::util::types::TypePathMap;

use crate::gen::base::map::{DefaultTypeMapper, TypePathMapper};

use crate::gen::base::message::Templates;

use crate::gen::base::message_from_bytes::generate_from_bytes_impl;

use crate::gen::base::Error;

use crate::gen::codec::CodecMap;

use crate::gen::rust::util::{gen_where_clause, RustUtils};

use crate::gen::template::Template;

use itertools::Itertools;

const TEMPLATE: &[u8] = include_bytes!("offsets.template");

fn gen_message_offset_field(

    field: &Field,

    template: &Template,

    type_path_map: &TypePathMapper<DefaultTypeMapper>,

) -> String {

    let mut scope = template.scope();

    scope.var("name", &field.name);

    match &field.ty {

        FieldType::Ref(Referenced::Message(v)) => {

            scope.var("type_name", type_path_map.get(v));

            match field.optional {

                true => scope.render("decl", &["field", "msg_optional"]).unwrap(),

                false => scope.render("decl", &["field", "msg"]).unwrap(),

            }

        }

        _ => scope.render("decl", &["field"]).unwrap(),

    }

}

pub fn gen_message_offsets_decl(

    msg: &Message,

    codec_map: &CodecMap,

    type_path_map: &TypePathMap,

) -> Result<String, Error> {

    let type_path_map = TypePathMapper::new(type_path_map, DefaultTypeMapper);

    let mut templates = Templates {

        template: Template::compile(TEMPLATE).unwrap(),

        codec_map,

    };

    let where_clauses = msg

        .fields

        .iter()

        .map(|field| gen_where_clause(&templates.template, field, &type_path_map, "impl"))

        .join("");

    templates

        .template

        .var("msg_name", &msg.name)

        .var("generics", RustUtils::get_generics(msg, &type_path_map).to_string())

        .var("where_clauses", where_clauses);

    let fields = msg

        .fields

        .iter()

        .map(|field| gen_message_offset_field(field, &templates.template, &type_path_map))

        .join("");

    let mut code = templates.template.var("fields", fields).render("", &["decl"]).unwrap();

    code += "\n";

    code += &generate_from_bytes_impl::<RustUtils, _>(msg, &templates, &type_path_map, "impl")
?0
;

    Ok(code)

}