import * as fs from 'fs';
import * as path from 'path';
import * as tsickle from 'tsickle';
import * as ts from 'typescript';

import {PLUGIN as bazelConformancePlugin} from '../tsetse/runner';

import {CachedFileLoader, FileLoader, ProgramAndFileCache, UncachedFileLoader} from './cache';
import {CompilerHost} from './compiler_host';
import * as bazelDiagnostics from './diagnostics';
import {constructManifest} from './manifest';
import * as perfTrace from './perf_trace';
import {PLUGIN as strictDepsPlugin} from './strict_deps';
import {BazelOptions, parseTsconfig, resolveNormalizedPath} from './tsconfig';
import {debug, log, runAsWorker, runWorkerLoop} from './worker';

/**
 * Top-level entry point for tsc_wrapped.
 */
export function main(args: string[]) {
  if (runAsWorker(args)) {
    log('Starting TypeScript compiler persistent worker...');
    runWorkerLoop(runOneBuild);
    // Note: intentionally don't process.exit() here, because runWorkerLoop
    // is waiting for async callbacks from node.
  } else {
    debug('Running a single build...');
    if (args.length === 0) throw new Error('Not enough arguments');
    if (!runOneBuild(args)) {
      return 1;
    }
  }
  return 0;
}

/** The one ProgramAndFileCache instance used in this process. */
const cache = new ProgramAndFileCache(debug);

function isCompilationTarget(
    bazelOpts: BazelOptions, sf: ts.SourceFile): boolean {
  return (bazelOpts.compilationTargetSrc.indexOf(sf.fileName) !== -1);
}

/**
 * Gather diagnostics from TypeScript's type-checker as well as other plugins we
 * install such as strict dependency checking.
 */
export function gatherDiagnostics(
    options: ts.CompilerOptions, bazelOpts: BazelOptions, program: ts.Program,
    disabledTsetseRules: string[]): ts.Diagnostic[] {
  // Install extra diagnostic plugins
  if (!bazelOpts.disableStrictDeps) {
    const ignoredFilesPrefixes: string[] = [];
    if (bazelOpts.nodeModulesPrefix) {
      // Under Bazel, we exempt external files fetched from npm from strict
      // deps. This is because we allow users to implicitly depend on all the
      // node_modules.
      // TODO(alexeagle): if users opt-in to fine-grained npm dependencies, we
      // should be able to enforce strict deps for them.
      ignoredFilesPrefixes.push(bazelOpts.nodeModulesPrefix);
      if (options.rootDir) {
        ignoredFilesPrefixes.push(
            path.resolve(options.rootDir!, 'node_modules'));
      }
    }
    program = strictDepsPlugin.wrap(program, {
      ...bazelOpts,
      rootDir: options.rootDir,
      ignoredFilesPrefixes,
    });
  }
  if (!bazelOpts.isJsTranspilation) {
    let selectedTsetsePlugin = bazelConformancePlugin;
    program = selectedTsetsePlugin.wrap(program, disabledTsetseRules);
  }

  // TODO(alexeagle): support plugins registered by config

  const diagnostics: ts.Diagnostic[] = [];
  perfTrace.wrap('type checking', () => {
    // These checks mirror ts.getPreEmitDiagnostics, with the important
    // exception of avoiding b/30708240, which is that if you call
    // program.getDeclarationDiagnostics() it somehow corrupts the emit.
    perfTrace.wrap(`global diagnostics`, () => {
      diagnostics.push(...program.getOptionsDiagnostics());
      diagnostics.push(...program.getGlobalDiagnostics());
    });
    let sourceFilesToCheck: ReadonlyArray<ts.SourceFile>;
    if (bazelOpts.typeCheckDependencies) {
      sourceFilesToCheck = program.getSourceFiles();
    } else {
      sourceFilesToCheck = program.getSourceFiles().filter(
          f => isCompilationTarget(bazelOpts, f));
    }
    for (const sf of sourceFilesToCheck) {
      perfTrace.wrap(`check ${sf.fileName}`, () => {
        diagnostics.push(...program.getSyntacticDiagnostics(sf));
        diagnostics.push(...program.getSemanticDiagnostics(sf));
      });
      perfTrace.snapshotMemoryUsage();
    }
  });

  return diagnostics;
}

/**
 * Runs a single build, returning false on failure.  This is potentially called
 * multiple times (once per bazel request) when running as a bazel worker.
 * Any encountered errors are written to stderr.
 */
function runOneBuild(
    args: string[], inputs?: {[path: string]: string}): boolean {
  if (args.length !== 1) {
    console.error('Expected one argument: path to tsconfig.json');
    return false;
  }

  perfTrace.snapshotMemoryUsage();

  // Strip leading at-signs, used in build_defs.bzl to indicate a params file
  const tsconfigFile = args[0].replace(/^@+/, '');
  const [parsed, errors, {target}] = parseTsconfig(tsconfigFile);
  if (errors) {
    console.error(bazelDiagnostics.format(target, errors));
    return false;
  }
  if (!parsed) {
    throw new Error(
        'Impossible state: if parseTsconfig returns no errors, then parsed should be non-null');
  }
  const {options, bazelOpts, files, disabledTsetseRules} = parsed;

  if (bazelOpts.maxCacheSizeMb !== undefined) {
    const maxCacheSizeBytes = bazelOpts.maxCacheSizeMb * (1 << 20);
    cache.setMaxCacheSize(maxCacheSizeBytes);
  } else {
    cache.resetMaxCacheSize();
  }

  let fileLoader: FileLoader;
  if (inputs) {
    fileLoader = new CachedFileLoader(cache);
    // Resolve the inputs to absolute paths to match TypeScript internals
    const resolvedInputs = new Map<string, string>();
    for (const key of Object.keys(inputs)) {
      resolvedInputs.set(resolveNormalizedPath(key), inputs[key]);
    }
    cache.updateCache(resolvedInputs);
  } else {
    fileLoader = new UncachedFileLoader();
  }

  const perfTracePath = bazelOpts.perfTracePath;
  if (!perfTracePath) {
    return runFromOptions(
        fileLoader, options, bazelOpts, files, disabledTsetseRules);
  }

  log('Writing trace to', perfTracePath);
  const success = perfTrace.wrap(
      'runOneBuild',
      () => runFromOptions(
          fileLoader, options, bazelOpts, files, disabledTsetseRules));
  if (!success) return false;
  // Force a garbage collection pass.  This keeps our memory usage
  // consistent across multiple compilations, and allows the file
  // cache to use the current memory usage as a guideline for expiring
  // data.  Note: this is intentionally not within runFromOptions(), as
  // we want to gc only after all its locals have gone out of scope.
  global.gc();

  perfTrace.snapshotMemoryUsage();
  perfTrace.write(perfTracePath);

  return true;
}

// We only allow our own code to use the expected_diagnostics attribute
const expectDiagnosticsWhitelist: string[] = [
];

function runFromOptions(
    fileLoader: FileLoader, options: ts.CompilerOptions,
    bazelOpts: BazelOptions, files: string[],
    disabledTsetseRules: string[]): boolean {
  perfTrace.snapshotMemoryUsage();
  cache.resetStats();
  cache.traceStats();
  const compilerHostDelegate =
      ts.createCompilerHost({target: ts.ScriptTarget.ES5});

  const moduleResolver = bazelOpts.isJsTranspilation ?
      makeJsModuleResolver(bazelOpts.workspaceName) :
      ts.resolveModuleName;
  const compilerHost = new CompilerHost(
      files, options, bazelOpts, compilerHostDelegate, fileLoader,
      moduleResolver);


  const oldProgram = cache.getProgram(bazelOpts.target);
  const program = perfTrace.wrap(
      'createProgram',
      () => ts.createProgram(
          compilerHost.inputFiles, options, compilerHost, oldProgram));
  cache.putProgram(bazelOpts.target, program);


  const compilationTargets = program.getSourceFiles().filter(
      fileName => isCompilationTarget(bazelOpts, fileName));

  let diagnostics: ts.Diagnostic[] = [];
  let useTsickleEmit = bazelOpts.tsickle;
  if (useTsickleEmit) {
    diagnostics = emitWithTsickle(
        program, compilerHost, compilationTargets, options, bazelOpts);
  } else {
    diagnostics = emitWithTypescript(program, compilationTargets);
  }

  if (diagnostics.length > 0) {
    console.error(bazelDiagnostics.format(bazelOpts.target, diagnostics));
    debug('compilation failed at', new Error().stack!);
    return false;
  }

  cache.printStats();
  return true;
}

function emitWithTypescript(
    program: ts.Program, compilationTargets: ts.SourceFile[]): ts.Diagnostic[] {
  const diagnostics: ts.Diagnostic[] = [];
  for (const sf of compilationTargets) {
    const result = program.emit(sf);
    diagnostics.push(...result.diagnostics);
  }
  return diagnostics;
}

function emitWithTsickle(
    program: ts.Program, compilerHost: CompilerHost,
    compilationTargets: ts.SourceFile[], options: ts.CompilerOptions,
    bazelOpts: BazelOptions): ts.Diagnostic[] {
  const emitResults: tsickle.EmitResult[] = [];
  const diagnostics: ts.Diagnostic[] = [];
  // The 'tsickle' import above is only used in type positions, so it won't
  // result in a runtime dependency on tsickle.
  // If the user requests the tsickle emit, then we dynamically require it
  // here for use at runtime.
  let optTsickle: typeof tsickle;
  try {
    // tslint:disable-next-line:no-require-imports
    optTsickle = require('tsickle');
  } catch (e) {
    if (e.code !== 'MODULE_NOT_FOUND') {
      throw e;
    }
    throw new Error(
        'When setting bazelOpts { tsickle: true }, ' +
        'you must also add a devDependency on the tsickle npm package');
  }
  perfTrace.wrap('emit', () => {
    for (const sf of compilationTargets) {
      perfTrace.wrap(`emit ${sf.fileName}`, () => {
        emitResults.push(optTsickle.emitWithTsickle(
            program, compilerHost, compilerHost, options, sf));
      });
    }
  });
  const emitResult = optTsickle.mergeEmitResults(emitResults);
  diagnostics.push(...emitResult.diagnostics);

  // If tsickle reported diagnostics, don't produce externs or manifest outputs.
  if (diagnostics.length > 0) {
    return diagnostics;
  }

  let externs = '/** @externs */\n' +
      '// generating externs was disabled using generate_externs=False\n';
  if (bazelOpts.tsickleGenerateExterns) {
    externs =
        optTsickle.getGeneratedExterns(emitResult.externs, options.rootDir!);
  }

  if (bazelOpts.tsickleExternsPath) {
    // Note: when tsickleExternsPath is provided, we always write a file as a
    // marker that compilation succeeded, even if it's empty (just containing an
    // @externs).
    fs.writeFileSync(bazelOpts.tsickleExternsPath, externs);

    // When generating externs, generate an externs file for each of the input
    // .d.ts files.
    if (bazelOpts.tsickleGenerateExterns &&
        compilerHost.provideExternalModuleDtsNamespace) {
      for (const extern of compilationTargets) {
        if (!extern.isDeclarationFile) continue;
        const outputBaseDir = options.outDir!;
        const relativeOutputPath =
            compilerHost.relativeOutputPath(extern.fileName);
        mkdirp(outputBaseDir, path.dirname(relativeOutputPath));
        const outputPath = path.join(outputBaseDir, relativeOutputPath);
        const moduleName = compilerHost.pathToModuleName('', extern.fileName);
        fs.writeFileSync(
            outputPath,
            `goog.module('${moduleName}');\n` +
                `// Export an empty object of unknown type to allow imports.\n` +
                `// TODO: use typeof once available\n` +
                `exports = /** @type {?} */ ({});\n`);
      }
    }
  }

  if (bazelOpts.manifest) {
    perfTrace.wrap('manifest', () => {
      const manifest =
          constructManifest(emitResult.modulesManifest, compilerHost);
      fs.writeFileSync(bazelOpts.manifest, manifest);
    });
  }

  return diagnostics;
}

/**
 * Creates directories subdir (a slash separated relative path) starting from
 * base.
 */
function mkdirp(base: string, subdir: string) {
  const steps = subdir.split(path.sep);
  let current = base;
  for (let i = 0; i < steps.length; i++) {
    current = path.join(current, steps[i]);
    if (!fs.existsSync(current)) fs.mkdirSync(current);
  }
}


/**
 * Resolve module filenames for JS modules.
 *
 * JS module resolution needs to be different because when transpiling JS we
 * do not pass in any dependencies, so the TS module resolver will not resolve
 * any files.
 *
 * Fortunately, JS module resolution is very simple. The imported module name
 * must either a relative path, or the workspace root (i.e. 'google3'),
 * so we can perform module resolution entirely based on file names, without
 * looking at the filesystem.
 */
function makeJsModuleResolver(workspaceName: string) {
  // The literal '/' here is cross-platform safe because it's matching on
  // import specifiers, not file names.
  const workspaceModuleSpecifierPrefix = `${workspaceName}/`;
  const workspaceDir = `${path.sep}${workspaceName}${path.sep}`;
  function jsModuleResolver(
      moduleName: string, containingFile: string,
      compilerOptions: ts.CompilerOptions, host: ts.ModuleResolutionHost):
      ts.ResolvedModuleWithFailedLookupLocations {
    let resolvedFileName;
    if (containingFile === '') {
      // In tsickle we resolve the filename against '' to get the goog module
      // name of a sourcefile.
      resolvedFileName = moduleName;
    } else if (moduleName.startsWith(workspaceModuleSpecifierPrefix)) {
      // Given a workspace name of 'foo', we want to resolve import specifiers
      // like: 'foo/project/file.js' to the absolute filesystem path of
      // project/file.js within the workspace.
      const workspaceDirLocation = containingFile.indexOf(workspaceDir);
      if (workspaceDirLocation < 0) {
        return {resolvedModule: undefined};
      }
      const absolutePathToWorkspaceDir =
          containingFile.slice(0, workspaceDirLocation);
      resolvedFileName = path.join(absolutePathToWorkspaceDir, moduleName);
    } else {
      if (!moduleName.startsWith('./') && !moduleName.startsWith('../')) {
        throw new Error(
            `Unsupported module import specifier: ${
                JSON.stringify(moduleName)}.\n` +
            `JS module imports must either be relative paths ` +
            `(beginning with '.' or '..'), ` +
            `or they must begin with '${workspaceName}/'.`);
      }
      resolvedFileName = path.join(path.dirname(containingFile), moduleName);
    }
    return {
      resolvedModule: {
        resolvedFileName,
        extension: ts.Extension.Js,  // js can only import js
        // These two fields are cargo culted from what ts.resolveModuleName
        // seems to return.
        packageId: undefined,
        isExternalLibraryImport: false,
      }
    };
  }

  return jsModuleResolver;
}


if (require.main === module) {
  // Do not call process.exit(), as that terminates the binary before
  // completing pending operations, such as writing to stdout or emitting the
  // v8 performance log. Rather, set the exit code and fall off the main
  // thread, which will cause node to terminate cleanly.
  process.exitCode = main(process.argv.slice(2));
}