/**
 * @license
 * Copyright 2017 The Bazel Authors. All rights reserved.
 *
 * 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 'jasmine';

import * as ts from 'typescript';

import {CachedFileLoader, FileCache} from './file_cache';
import {invalidateFileCache, writeTempFile} from './test_support';

function fauxDebug(...args: any[]) {
  console.error.apply(console, args);
}

describe('FileCache', () => {
  let fileCache: FileCache;
  let fileLoader: CachedFileLoader;

  beforeEach(() => {
    fileCache = new FileCache(fauxDebug);
    fileLoader = new CachedFileLoader(fileCache);
  });

  function load(name: string, fn: string) {
    return fileLoader.loadFile(name, fn, ts.ScriptTarget.ES5);
  }

  function setCurrentFiles(...fileName: string[]) {
    // Give all files the same digest, so that the file cache allows reading
    // them, but does not evict them.
    const digests =
        new Map(fileName.map((fn): [string, string] => [fn, 'digest']));
    fileCache.updateCache(digests);
  }

  function expectCacheKeys() {
    // Strip the long /tmp paths created by writeTempFile.
    return expect(
        fileCache.getCacheKeysForTest().map(fn => fn.replace(/.*\./, '')));
  }

  it('caches files', () => {
    const fn = writeTempFile('file_cache_test', 'let x: number = 12;\n');
    invalidateFileCache(fileCache, fn);

    // Caches.
    const sourceFile = fileLoader.loadFile('fileName', fn, ts.ScriptTarget.ES5);
    let sourceFile2 = fileLoader.loadFile('fileName', fn, ts.ScriptTarget.ES5);
    expect(sourceFile).toBe(sourceFile2);  // i.e., identical w/ ===

    // Invalidate the file.
    invalidateFileCache(fileCache, fn);
    sourceFile2 = fileLoader.loadFile('fileName', fn, ts.ScriptTarget.ES5);
    // New file after write/mtime change.
    expect(sourceFile).not.toBe(sourceFile2);
  });

  it('caches in LRU order', () => {
    let free = false;
    fileCache.shouldFreeMemory = () => free;

    const fn1 = writeTempFile('file_cache_test1', 'let x: number = 1;\n');
    const fn2 = writeTempFile('file_cache_test2', 'let x: number = 2;\n');
    const fn3 = writeTempFile('file_cache_test3', 'let x: number = 3;\n');
    const fn4 = writeTempFile('file_cache_test4', 'let x: number = 4;\n');
    const fn5 = writeTempFile('file_cache_test5', 'let x: number = 5;\n');
    setCurrentFiles(fn1, fn2, fn3, fn4, fn5);

    // Populate the cache.
    const f1 = load('f1', fn1);
    const f2 = load('f2', fn2);
    const f3 = load('f3', fn3);
    const f4 = load('f4', fn4);

    expectCacheKeys().toEqual([
      'file_cache_test1',
      'file_cache_test2',
      'file_cache_test3',
      'file_cache_test4',
    ]);

    // Load f1 from cache again. Now f1 is the most recently used file.
    expect(load('f1', fn1)).toBe(f1, 'f1 should be cached');
    expectCacheKeys().toEqual([
      'file_cache_test2',
      'file_cache_test3',
      'file_cache_test4',
      'file_cache_test1',
    ]);

    // Now load f5 and pretend memory must be freed.
    // length / 2 == 2 files must be cleared.
    // f2 + f5 are pinned because they are part of the compilation unit.
    // f1, f3, f4 are eligible for eviction, and f1 is more recently used than
    // the others, so f1 shoud be retained, f3 + f4 dropped.

    setCurrentFiles(fn2, fn5);
    free = true;
    const f5 = load('f5', fn5);
    expectCacheKeys().toEqual([
      'file_cache_test2',
      'file_cache_test1',
      'file_cache_test5',
    ]);
    setCurrentFiles(fn1, fn2, fn3, fn4, fn5);
    expect(load('f1', fn1))
        .toBe(f1, 'f1 should not be dropped, it was recently used');
    expect(load('f2', fn2)).toBe(f2, 'f2 should be pinned');
    expect(load('f3', fn3)).not.toBe(f3, 'f3 should have been dropped');
    expect(load('f4', fn4)).not.toBe(f4, 'f4 should have been dropped');
    expect(load('f5', fn5)).toBe(f5, 'f5 should be pinned');
  });

  it('degenerates to cannotEvict mode', () => {
    // Pretend to always be out of memory.
    fileCache.shouldFreeMemory = () => true;

    const fn1 = writeTempFile('file_cache_test1', 'let x: number = 1;\n');
    const fn2 = writeTempFile('file_cache_test2', 'let x: number = 2;\n');
    const fn3 = writeTempFile('file_cache_test3', 'let x: number = 3;\n');
    const fn4 = writeTempFile('file_cache_test4', 'let x: number = 4;\n');
    setCurrentFiles(fn1, fn2, fn3);

    load('fn1', fn1),
    load('fn2', fn2);
    load('fn3', fn3);

    expect(fileCache['cannotEvict']).toBe(true, 'all files are pinned');
    expectCacheKeys().toEqual([
      'file_cache_test1',
      'file_cache_test2',
      'file_cache_test3',
    ]);
    setCurrentFiles(fn1, fn4);
    expect(fileCache['cannotEvict']).toBe(false, 'pinned files reset');
    load('fn4', fn4);
    expectCacheKeys().toEqual([
      'file_cache_test1',
      'file_cache_test4',
    ]);
  });
});