/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */
import { Compiler, loader } from 'webpack';
import { CachedSource, ConcatSource, OriginalSource, RawSource, Source } from 'webpack-sources';
import { interpolateName } from 'loader-utils';
import * as path from 'path';

const Chunk = require('webpack/lib/Chunk');

export interface ScriptsWebpackPluginOptions {
  name: string;
  sourceMap: boolean;
  scripts: string[];
  filename: string;
  basePath: string;
}

interface ScriptOutput {
  filename: string;
  source: CachedSource;
}

function addDependencies(compilation: any, scripts: string[]): void {
  if (compilation.fileDependencies.add) {
    // Webpack 4+ uses a Set
    for (const script of scripts) {
      compilation.fileDependencies.add(script);
    }
  } else {
    // Webpack 3
    compilation.fileDependencies.push(...scripts);
  }
}

export class ScriptsWebpackPlugin {
  private _lastBuildTime?: number;
  private _cachedOutput?: ScriptOutput;

  constructor(private options: Partial<ScriptsWebpackPluginOptions> = {}) {}

  shouldSkip(compilation: any, scripts: string[]): boolean {
    if (this._lastBuildTime == undefined) {
      this._lastBuildTime = Date.now();
      return false;
    }

    for (let i = 0; i < scripts.length; i++) {
      let scriptTime;
      if (compilation.fileTimestamps.get) {
        // Webpack 4+ uses a Map
        scriptTime = compilation.fileTimestamps.get(scripts[i]);
      } else {
        // Webpack 3
        scriptTime = compilation.fileTimestamps[scripts[i]];
      }
      if (!scriptTime || scriptTime > this._lastBuildTime) {
        this._lastBuildTime = Date.now();
        return false;
      }
    }

    return true;
  }

  private _insertOutput(compilation: any, { filename, source }: ScriptOutput, cached = false) {
    const chunk = new Chunk();
    chunk.rendered = !cached;
    chunk.id = this.options.name;
    chunk.ids = [chunk.id];
    chunk.name = this.options.name;
    chunk.isInitial = () => true;
    chunk.files.push(filename);

    compilation.chunks.push(chunk);
    compilation.assets[filename] = source;
  }

  apply(compiler: Compiler): void {
    if (!this.options.scripts || this.options.scripts.length === 0) {
      return;
    }

    const scripts = this.options.scripts
      .filter(script => !!script)
      .map(script => path.resolve(this.options.basePath || '', script));

    compiler.plugin('this-compilation', (compilation: any) => {
      compilation.plugin('additional-assets', (callback: (err?: Error) => void) => {
        if (this.shouldSkip(compilation, scripts)) {
          if (this._cachedOutput) {
            this._insertOutput(compilation, this._cachedOutput, true);
          }

          addDependencies(compilation, scripts);
          callback();

          return;
        }

        const sourceGetters = scripts.map(fullPath => {
          return new Promise<Source>((resolve, reject) => {
            compilation.inputFileSystem.readFile(fullPath, (err: Error, data: Buffer) => {
              if (err) {
                reject(err);
                return;
              }

              const content = data.toString();

              let source;
              if (this.options.sourceMap) {
                // TODO: Look for source map file (for '.min' scripts, etc.)

                let adjustedPath = fullPath;
                if (this.options.basePath) {
                  adjustedPath = path.relative(this.options.basePath, fullPath);
                }
                source = new OriginalSource(content, adjustedPath);
              } else {
                source = new RawSource(content);
              }

              resolve(source);
            });
          });
        });

        Promise.all(sourceGetters)
          .then(sources => {
            const concatSource = new ConcatSource();
            sources.forEach(source => {
              concatSource.add(source);
              concatSource.add('\n;');
            });

            const combinedSource = new CachedSource(concatSource);
            const filename = interpolateName(
              { resourcePath: 'scripts.js' } as loader.LoaderContext,
              this.options.filename,
              { content: combinedSource.source() },
            );

            const output = { filename, source: combinedSource };
            this._insertOutput(compilation, output);
            this._cachedOutput = output;
            addDependencies(compilation, scripts);

            callback();
          })
          .catch((err: Error) => callback(err));
      });
    });
  }
}