module.exports = function(grunt) {

  // Project configuration.
  grunt.initConfig({
    pkg: grunt.file.readJSON( 'package.json' ),

    // default task
    // use 'grunt copy' to copy the entire <galaxy>/client/galaxy/scripts dir into <galaxy>/static/scripts
    copy: {
      main: {
        files: [
          {
            expand : true,
            cwd : 'galaxy/scripts/',
            src : '**',
            dest : '../static/scripts'
          }
        ]
      }
    },

    // use 'grunt pack' to call pack_scripts.py to pack all or selected files in static/scripts
    exec: {
      packScripts: {
        cwd: '../static/scripts',
        target: [],
        cmd: function(){
          var targets = grunt.config( 'exec.packScripts.target' );
          // if nothing was passed in pack all scripts
          if( !targets.length ){
            return './pack_scripts.py';
          }

          grunt.log.write( 'packing: ' + targets + '\n' );
          return targets.map( function( target ){
            return './pack_scripts.py ' + target;
          }).join( '; ' );
        }
      }
    },

    // use 'grunt watch' (from a new tab in your terminal) to have grunt re-copy changed files automatically
    watch: {
        // watch for changes in the src dir
        files: [ 'galaxy/scripts/**' ],
        tasks: [ 'copy', 'pack' ],
        options: {
          spawn: false
        }
    },

    // call bower to install libraries and other external resources
    "bower-install-simple" : {
      options: {
          color: true
      },
      "prod": {
          options: {
              production: true
          }
      },
      "dev": {
          options: {
              production: false
          }
      }
    },
    // where to move fetched bower components into the build structure (libName: [ bower-location, libs-location ])
    libraryLocations : {
      "jquery": [ "dist/jquery.js", "jquery/jquery.js" ],
      "jquery-migrate": [ "jquery-migrate.js", "jquery/jquery.migrate.js" ],
      "traceKit": [ "tracekit.js", "tracekit.js" ],
      "ravenjs": [ "dist/raven.js", "raven.js" ],
      "underscore": [ "underscore.js", "underscore.js" ],
      "handlebars": [ "handlebars.runtime.js", "handlebars.runtime.js" ],
      "lunr.js": [ "lunr.js", "lunr.js" ]
      //"backbone": [ "backbone.js", "backbone/backbone.js" ],

      // these need to be updated and tested
      //"require": [ "build/require.js", "require.js" ],
      //"d3": [ "d3.js", "d3.js" ],
      //"farbtastic": [ "src/farbtastic.js", "farbtastic.js" ],
      //"jQTouch": [ "src/reference/jqtouch.js", "jquery/jqtouch.js" ],
      //"bib2json": [ "Parser.js", "bibtex.js" ],
      //"jquery-form": [ "jquery.form.js", "jquery/jquery.form.js" ],
      //"jquery-autocomplete": [ "src/jquery.autocomplete.js", "jquery/jquery.autocomplete.js" ],
      //"select2": [ "select2.js", "jquery/select2.js" ],
      //"jStorage": [ "jstorage.js", "jquery/jstorage.js" ],
      //"jquery.cookie": [ "", "jquery/jquery.cookie.js" ],
      //"dynatree": [ "dist/jquery.dynatree.js", "jquery/jquery.dynatree.js" ],
      //"jquery-mousewheel": [ "jquery.mousewheel.js", "jquery/jquery.mousewheel.js" ],
      //"jquery.event.drag-drop": [
      //  [ "event.drag/jquery.event.drag.js", "jquery/jquery.event.drag.js" ],
      //  [ "event.drag/jquery.event.drop.js", "jquery/jquery.event.drop.js" ]
      //],

      // these are complicated by additional css/less
      //"toastr": [ "toastr.js", "toastr.js" ],
      //"wymeditor": [ "dist/wymeditor/jquery.wymeditor.js", "jquery/jquery.wymeditor.js" ],
      //"jstree": [ "jstree.js", "jquery/jstree.js" ],

      // these have been customized by Galaxy
      //"bootstrap": [ "dist/js/bootstrap.js", "bootstrap.js" ],
      //"jquery-ui": [
      //  // multiple components now
      //  [ "", "jquery/jquery-ui.js" ]
      //],

    }

  });

  grunt.loadNpmTasks( 'grunt-contrib-watch' );
  grunt.loadNpmTasks( 'grunt-contrib-copy');
  grunt.loadNpmTasks( 'grunt-bower-install-simple');
  grunt.loadNpmTasks( 'grunt-exec' );

  grunt.registerTask( 'pack', [ 'exec' ] );
  grunt.registerTask( 'default', [ 'copy:main', 'pack' ] );


  // -------------------------------------------------------------------------- copy,pack only those changed
  // adapted from grunt-contrib-watch jslint example
  //TODO: a bit hacky and there's prob. a better way
  //NOTE: copy will fail silently if a file isn't found

  // outer scope variable for the event handler and onChange fn - begin with empty hash
  var changedFiles = Object.create(null);

  // when files are changed, set the copy src and packScripts target to the filenames of the updated files
  var onChange = grunt.util._.debounce(function() {
    grunt.config( 'copy.main.files', [{
      expand: true,
      cwd: 'galaxy/scripts',
      src: Object.keys( changedFiles ),
      dest: '../static/scripts/'
    }]);
    grunt.config( 'exec.packScripts.target', Object.keys( changedFiles ) );
    changedFiles = Object.create(null);
  }, 200);

  grunt.event.on('watch', function(action, filepath) {
    // store each filepath in a Files obj, the debounced fn above will use it as an aggregate list for copying
    // we need to take galaxy/scripts out of the filepath or it will be copied to the wrong loc
    filepath = filepath.replace( /galaxy\/scripts\//, '' );
    changedFiles[filepath] = action;
    onChange();
  });

  // -------------------------------------------------------------------------- fetch/update external libraries
  /** copy external libraries from bower components to scripts/libs */
  function copyLibs(){
    var libraryLocations = grunt.config( 'libraryLocations' );
    for( var libName in libraryLocations ){
      if( libraryLocations.hasOwnProperty( libName ) ){

        var BOWER_DIR = 'bower_components',
            location = libraryLocations[ libName ],
            source = [ BOWER_DIR, libName, location[0] ].join( '/' ),
            destination = 'galaxy/scripts/libs/' + location[1];
        grunt.log.writeln( source + ' -> ' + destination );
        grunt.file.copy( source, destination );
      }
    }
  }

  grunt.registerTask( 'copy-libs', 'copy external libraries to src', copyLibs );
  grunt.registerTask( 'install-libs', 'fetch external libraries and copy to src',
                      [ 'bower-install-simple:prod', 'copy-libs' ] );

};