/**
 * Copyright (c) Microsoft Corporation.
 *
 * 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.
 */

import type { BrowserContext } from '../server/browserContext';
import type { PageSnapshot, SanpshotterResource, SnapshotterBlob, SnapshotterDelegate } from '../server/snapshotter';
import { ContextCreatedTraceEvent, ContextDestroyedTraceEvent, NetworkResourceTraceEvent, SnapshotTraceEvent } from './traceTypes';
import * as path from 'path';
import * as util from 'util';
import * as fs from 'fs';
import { calculateSha1, createGuid, mkdirIfNeeded, monotonicTime } from '../utils/utils';

const fsWriteFileAsync = util.promisify(fs.writeFile.bind(fs));
const fsAppendFileAsync = util.promisify(fs.appendFile.bind(fs));
const fsAccessAsync = util.promisify(fs.access.bind(fs));

export class Tracer implements SnapshotterDelegate {
  private _contextIds = new Map<BrowserContext, string>();
  private _traceStoragePromise: Promise<string>;
  private _appendEventChain: Promise<string>;
  private _writeArtifactChain: Promise<void>;

  constructor(traceStorageDir: string, traceFile: string) {
    this._traceStoragePromise = mkdirIfNeeded(path.join(traceStorageDir, 'sha1')).then(() => traceStorageDir);
    this._appendEventChain = mkdirIfNeeded(traceFile).then(() => traceFile);
    this._writeArtifactChain = Promise.resolve();
  }

  onContextCreated(context: BrowserContext): void {
    const contextId = 'context@' + createGuid();
    this._contextIds.set(context, contextId);
    const event: ContextCreatedTraceEvent = {
      type: 'context-created',
      browserName: context._browser._options.name,
      contextId,
      isMobile: !!context._options.isMobile,
      deviceScaleFactor: context._options.deviceScaleFactor || 1,
      viewportSize: context._options.viewport || undefined,
    };
    this._appendTraceEvent(event);
  }

  onContextDestroyed(context: BrowserContext): void {
    const event: ContextDestroyedTraceEvent = {
      type: 'context-destroyed',
      contextId: this._contextIds.get(context)!,
    };
    this._appendTraceEvent(event);
  }

  onBlob(context: BrowserContext, blob: SnapshotterBlob): void {
    this._writeArtifact(blob.sha1, blob.buffer);
  }

  onResource(context: BrowserContext, resource: SanpshotterResource): void {
    const event: NetworkResourceTraceEvent = {
      type: 'resource',
      contextId: this._contextIds.get(context)!,
      frameId: resource.frameId,
      url: resource.url,
      contentType: resource.contentType,
      responseHeaders: resource.responseHeaders,
      sha1: resource.sha1,
    };
    this._appendTraceEvent(event);
  }

  onSnapshot(context: BrowserContext, snapshot: PageSnapshot): void {
    const buffer = Buffer.from(JSON.stringify(snapshot));
    const sha1 = calculateSha1(buffer);
    const event: SnapshotTraceEvent = {
      type: 'snapshot',
      contextId: this._contextIds.get(context)!,
      label: snapshot.label,
      sha1,
    };
    this._appendTraceEvent(event);
    this._writeArtifact(sha1, buffer);
  }

  async dispose() {
    // Ensure all writes are finished.
    await this._appendEventChain;
    await this._writeArtifactChain;
  }

  private _writeArtifact(sha1: string, buffer: Buffer) {
    // Save all write promises to wait for them in dispose.
    const promise = this._innerWriteArtifact(sha1, buffer);
    this._writeArtifactChain = this._writeArtifactChain.then(() => promise);
  }

  private async _innerWriteArtifact(sha1: string, buffer: Buffer): Promise<void> {
    const traceDirectory = await this._traceStoragePromise;
    const filePath = path.join(traceDirectory, sha1);
    try {
      await fsAccessAsync(filePath);
    } catch (e) {
      // File does not exist - write it.
      await fsWriteFileAsync(filePath, buffer);
    }
  }

  private _appendTraceEvent(event: any) {
    // Serialize all writes to the trace file.
    const timestamp = monotonicTime();
    this._appendEventChain = this._appendEventChain.then(async traceFile => {
      await fsAppendFileAsync(traceFile, JSON.stringify({...event, timestamp}) + '\n');
      return traceFile;
    });
  }
}