// Copyright 2022 The Pigweed Authors
//
// 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
//
//     https://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.

import * as fs from 'fs';
import { FileDescriptorSet } from 'google-protobuf/google/protobuf/descriptor_pb';

// Keeping template here is not elegant but let's us avoid issues when bundling via rollup:
// Previously, we had to keep a copy of this template file alongside this CLI script.
const template = `
import { ProtoCollection as Base } from 'pigweedjs/pw_protobuf_compiler';
import { FileDescriptorSet } from 'google-protobuf/google/protobuf/descriptor_pb';
import * as base64 from 'base64-js';

// Generated proto imports added during build
// TEMPLATE_proto_imports

const MODULE_MAP = {
  // TEMPLATE_module_map
};

const DESCRIPTOR_BASE64_BINARY = '{TEMPLATE_descriptor_binary}';

/**
 * A wrapper class of protocol buffer modules to provide convenience methods.
 */
export class ProtoCollection extends Base {
  constructor() {
    const fileDescriptorSet = FileDescriptorSet.deserializeBinary(
      base64.toByteArray(DESCRIPTOR_BASE64_BINARY),
    );
    super(fileDescriptorSet, MODULE_MAP);
  }
}
`;

function buildModulePath(rootDir: string, fileName: string): string {
  const name = `${rootDir}/${fileName}`;
  return name.replace(/\.proto$/, '_pb');
}

export default function generateTemplate(
  outputPath: string,
  descriptorDataPath: string,
) {
  const descriptorSetBinary = fs.readFileSync(descriptorDataPath);
  const base64DescriptorSet = descriptorSetBinary.toString('base64');
  const fileDescriptorSet = FileDescriptorSet.deserializeBinary(
    Buffer.from(descriptorSetBinary),
  );

  const imports = [];
  const moduleDictionary = [];
  const fileList = fileDescriptorSet.getFileList();
  for (let i = 0; i < fileList.length; i++) {
    const file = fileList[i];
    const modulePath = buildModulePath('.', file.getName()!);
    const moduleName = 'proto_' + i;
    imports.push(`import * as ${moduleName} from '${modulePath}';`);
    const key = file.getName()!;
    moduleDictionary.push(`'${key}': ${moduleName},`);
  }

  let filledTemplate = template.replace(
    '{TEMPLATE_descriptor_binary}',
    base64DescriptorSet,
  );
  filledTemplate = filledTemplate.replace(
    '// TEMPLATE_proto_imports',
    imports.join('\n'),
  );
  filledTemplate = filledTemplate.replace(
    '// TEMPLATE_module_map',
    moduleDictionary.join('\n'),
  );

  fs.writeFileSync(outputPath, filledTemplate);
}