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// Copyright 2021 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

mod data;
mod gen;
mod util;

use self::data::{Package, PackageOrMessage};
use self::gen::PackageOrMessageExt as _;

use crate::Result;
use ::itertools::Itertools;
use ::proc_macro2::TokenStream;
use ::quote::quote;
use ::stable_puroro::protobuf::google::protobuf::compiler::code_generator_response::File;
use ::stable_puroro::protobuf::google::protobuf::compiler::CodeGeneratorResponse;
use ::stable_puroro::protobuf::google::protobuf::FileDescriptorProtoView;
use ::std::iter;
use ::std::rc::Rc;

#[derive(Default)]
/// Configurates the generated code.
pub struct CodegenOptions {
    /// If this value is not specified, the code generator generates `lib.rs`
    /// as a root file. If it is specified, the root file name will become
    /// this `<root_module_name>.rs`, and the other files are generated under
    /// `<root_module_name>/` directory.
    pub root_module_name: Option<String>,

    /// Note: `root_module_name` will overwrite this flag.
    /// Renames the default `"lib.rs"` root file name.
    pub root_file_name: Option<String>,

    /// If specified, overwrites the puroro library path referenced by the
    /// generated code. Defaults by `"::puroro"`.
    pub puroro_library_path: Option<String>,
}

pub fn generate_file_names_and_tokens<'a>(
    files: impl Iterator<Item = &'a FileDescriptorProtoView>,
    options: &CodegenOptions,
) -> Result<impl IntoIterator<Item = (String, TokenStream)>> {
    let root_package = Package::new_root(files);

    let file_generating_items =
        iter::once(Ok(Rc::clone(&root_package) as Rc<dyn PackageOrMessage>))
            .chain(
                // Packages except root
                root_package
                    .all_child_packages()?
                    .into_iter()
                    .map(|p| Ok(p as Rc<dyn PackageOrMessage>)),
            )
            .chain(
                root_package
                    .all_child_messages()?
                    .into_iter()
                    .filter_map(|m| {
                        // messages which contains subitems
                        match m.should_generate_module_file() {
                            Ok(true) => Some(Ok(m as Rc<dyn PackageOrMessage>)),
                            Ok(false) => None,
                            Err(e) => Some(Err(e)),
                        }
                    }),
            );
    file_generating_items
        .map_ok(|item| {
            let file_name = item
                .module_file_path(
                    options.root_module_name.as_deref(),
                    options.root_file_name.as_deref(),
                )?
                .to_string();
            let file_content = item.gen_module_file(options.puroro_library_path.as_deref())?;
            Ok((file_name, quote! { #file_content }))
        })
        .map(|rr| rr.flatten())
        .collect::<Result<Vec<_>>>()
}

pub fn generate_output_file_protos<'a>(
    files: impl Iterator<Item = &'a FileDescriptorProtoView>,
    options: &CodegenOptions,
) -> Result<CodeGeneratorResponse> {
    let mut cgr = CodeGeneratorResponse::default();
    *cgr.file_mut() = generate_file_names_and_tokens(files, options)?
        .into_iter()
        .map(|(file_name, ts)| {
            let formatted = if let Ok(syn_file) = syn::parse2::<syn::File>(ts.clone()) {
                prettyplease::unparse(&syn_file)
            } else {
                // Parse failed route. Print the output file for debugging.
                eprintln!("Generated code error!");
                format!("{}", ts)
            };
            let mut output_file = File::default();
            *output_file.name_mut() = file_name;
            *output_file.content_mut() = formatted;
            Ok(output_file)
        })
        .collect::<Result<Vec<_>>>()?;

    Ok(cgr)
}

pub fn generate_tokens_for_inline<'a>(
    files: impl Iterator<Item = &'a FileDescriptorProtoView>,
    options: &CodegenOptions,
) -> Result<TokenStream> {
    let root_package = Package::new_root(files);
    root_package.gen_inline_code(options.puroro_library_path.as_deref())
}