/**
 * This task instruments our source code with istanbul, runs the test suite
 * on the instrumented source and collects the coverage data. It then creates
 * test coverage reports.
 *
 * TODO This can be improved in style. We should possibly rewrite it and use
 *      async.waterfall.
 */

var fs = require('fs');
var istanbul = require('istanbul');
var wrench = require('wrench');
var path = require('path');
var glob = require('glob');

var runTestsuite = require('./test').runTests;

// setup some pathes
var dir = path.join(__dirname, '../src');
var backupDir = path.join(__dirname, '../src-backup');
var instrumentedDir = path.join(__dirname, '../src-instrumented');
var coverageDir = path.join(__dirname, '../coverage');

// The main players in the coverage generation via istanbul
var instrumenter = new istanbul.Instrumenter();
var reporter = new istanbul.Reporter(false, coverageDir);
var collector = new istanbul.Collector();

// General options used for the resource shuffling / directory copying
var copyOpts = {
  // Whether to overwrite existing directory or not
  forceDelete: true,
  // Whether to copy hidden Unix files or not (preceding .)
  excludeHiddenUnix: false,
  // If we're overwriting something and the file already exists, keep the
  // existing
  preserveFiles: false,
  // Preserve the mtime and atime when copying files
  preserveTimestamps: true,
  // Whether to follow symlinks or not when copying files
  inflateSymlinks: false
};

/**
 * A small utility method printing out log messages.
 */
var log = function(msg){
  process.stdout.write(msg + '\n');
};


/**
 * A utility method to recursively delete a non-empty folder.
 *
 * See http://www.geedew.com/remove-a-directory-that-is-not-empty-in-nodejs/
 * adjusted to use path.join
 */
var deleteFolderRecursive = function(p) {
  if( fs.existsSync(p) ) {
    fs.readdirSync(p).forEach(function(file,index){
      var curPath = path.join(p, file);
      if(fs.lstatSync(curPath).isDirectory()) { // recurse
        deleteFolderRecursive(curPath);
      } else { // delete file
        fs.unlinkSync(curPath);
      }
    });
    fs.rmdirSync(p);
  }
};

/**
 * Creates folders for backup and instrumentation and copies the contents of the
 * current src folder into them.
 */
var setupBackupAndInstrumentationDir = function(){
  if (!fs.existsSync(backupDir)) {
    log('• create directory for backup of src: ' + backupDir);
    fs.mkdirSync(backupDir);
  }

  if (!fs.existsSync(instrumentedDir)) {
    log('• create directory for instrumented src: ' + instrumentedDir);
    fs.mkdirSync(instrumentedDir);
  }

  log('• copy src files to backup folder');
  wrench.copyDirSyncRecursive(dir, backupDir, copyOpts);
  log('• copy src files to instrumentation folder');
  wrench.copyDirSyncRecursive(dir, instrumentedDir, copyOpts);
};

/**
 * Reverts the changes done in setupBackupAndInstrumentationDir, copies the
 * backup over the src directory and removes the instrumentation and backup
 * directory.
 */
var revertBackupAndInstrumentationDir = function(){
  log('• copy original src back to src folder');
  wrench.copyDirSyncRecursive(backupDir, dir, copyOpts);
  log('• delete backup directory');
  deleteFolderRecursive(backupDir);
  log('• delete instrumentation directory');
  deleteFolderRecursive(instrumentedDir);
};


/**
 * Callback for when runTestsuite() has finished.
 */
var collectAndWriteCoverageData = function(code) {
  log('• collect data from coverage.json');

  var coverageFile = path.join(__dirname,'../coverage/coverage.json');
  var coverageJson = JSON.parse(fs.readFileSync(coverageFile, 'utf8'));
  collector.add(coverageJson);

  reporter.addAll(['lcovonly','html']);

  revertBackupAndInstrumentationDir();

  log('• write report from collected data');
  reporter.write(collector, true, function () {
    process.exit(0);
  });
};

/**
 * Will instrument all JavaScript files that are passed as second parameter.
 * This is the callback to the glob call.
 */
var foundAllJavaScriptSourceFiles = function(err, files) {
  if (err) {
    process.stderr.write(err.message + '\n');
    process.exit(1);
  }
  log('• instrumenting every src file');
  var cnt = 0;
  files.forEach(function(file) {
    cnt++;
    var content = fs.readFileSync(file, 'utf-8');
    // derive output file name from input file name, by replacing the *last*
    // occurence of /src/ by /src-instrumented/
    var re = new RegExp('/src/', 'g');
    var m, match;
    while ((m = re.exec(file)) !== null) {
      match = m;
    }
    var outfile = file.substr(0, match.index) + '/src-instrumented/' +
        file.substr(match.index + '/src/'.length);
    var instrumented = instrumenter.instrumentSync(content, file);
    fs.writeFileSync(outfile, instrumented);
    if (cnt % 10 === 0) {
      log('  • instrumented ' + cnt + ' files');
    }
  });
  log('  • done. ' + cnt + ' files instrumented');
  log('• copy instrumented src back to src folder');

  wrench.copyDirSyncRecursive(instrumentedDir, dir, copyOpts);

  log('• run test suite on instrumented code');
  runTestsuite(true, collectAndWriteCoverageData);
};

/**
 * Our main method, first it sets up certain directory, and then it starts the
 * coverage process by gathering all JavaScript files and then instrumenting
 * them.
 */
var main = function(){
  setupBackupAndInstrumentationDir();
  glob(dir + '/**/*.js', {}, foundAllJavaScriptSourceFiles);
};



if (require.main === module) {
  main();
}

module.exports = main;