'use strict';
var fs = require('fs');
var path = require('path');
var _ = require('lodash');
var tmpl = require('blueimp-tmpl').tmpl;

function HtmlWebpackPlugin(options) {
  this.options = options || {};
}

HtmlWebpackPlugin.prototype.apply = function(compiler) {
  var self = this;
  compiler.plugin('emit', function(compilation, callback) {
    var webpackStatsJson = compilation.getStats().toJson();
    var templateParams = {};
    templateParams.webpack = webpackStatsJson;
    templateParams.htmlWebpackPlugin = {};
    templateParams.htmlWebpackPlugin.assets = self.htmlWebpackPluginLegacyAssets(compilation, webpackStatsJson);
    templateParams.htmlWebpackPlugin.files = self.htmlWebpackPluginAssets(compilation, webpackStatsJson, self.options.hash);
    templateParams.htmlWebpackPlugin.options = self.options;
    templateParams.webpackConfig = compilation.options;

    var outputFilename = self.options.filename || 'index.html';

    if (self.options.templateContent && self.options.template) {
      compilation.errors.push(new Error('HtmlWebpackPlugin: cannot specify both template and templateContent options'));
      callback();
    } else if (self.options.templateContent) {
      var templateContent = typeof self.options.templateContent === 'function' ? self.options.templateContent(templateParams, compiler) : self.options.templateContent;
      self.emitHtml(compilation, templateContent, templateParams, outputFilename);
      callback();
    } else {
      var templateFile = self.options.template;
      if (!templateFile) {
        templateFile = path.join(__dirname, 'default_index.html');
      }
      compilation.fileDependencies.push(templateFile);

      fs.readFile(templateFile, 'utf8', function(err, htmlTemplateContent) {
        if (err) {
          compilation.errors.push(new Error('HtmlWebpackPlugin: Unable to read HTML template "' + templateFile + '"'));
        } else {
          self.emitHtml(compilation, htmlTemplateContent, templateParams, outputFilename);
        }
        callback();
      });
    }
  });
};

HtmlWebpackPlugin.prototype.emitHtml = function(compilation, htmlTemplateContent, templateParams, outputFilename) {
  var html;
  try {
   html = tmpl(htmlTemplateContent, templateParams);
  } catch(e) {
    compilation.errors.push(new Error('HtmlWebpackPlugin: template error ' + e));
  }
  // Append/Inject link and script elements into an existing html file
  if (this.options.append) {
    html = this.appendAssetsToHtml(html, templateParams, this.options.append);
  }
  compilation.assets[outputFilename] = {
    source: function() {
      return html;
    },
    size: function() {
      return html.length;
    }
  };
};


HtmlWebpackPlugin.prototype.htmlWebpackPluginAssets = function(compilation, webpackStatsJson, appendHash) {
  var publicPath = compilation.options.output.publicPath || '';
  var queryString = appendHash ? '?' + webpackStatsJson.hash : '';

  var assets = {
    // Will contain all js & css files by chunk
    chunks: {},
    // Will contain all js files
    js: [],
    // Will contain all css files
    css: [],
    // Will contain the html5 appcache manifest files if it exists
    manifest: Object.keys(compilation.assets).filter(function(assetFile){
      return path.extname(assetFile) === '.appcache';
    }).map(function(assetFile) {
      return assetFile + queryString;
    })[0]
  };

  var chunks = webpackStatsJson.chunks.sort(function orderEntryLast(a, b) {
    if (a.entry !== b.entry) {
      return b.entry ? 1 : -1;
    } else {
      return b.id - a.id;
    }
  });

  for (var i = 0; i < chunks.length; i++) {
    var chunk = chunks[i];
    var chunkName = chunk.names[0];
    assets.chunks[chunkName] = {};

    // Prepend the public path to all chunk files
    var chunkFiles = [].concat(chunk.files).map(function(chunkFile) {
      return publicPath + chunkFile + queryString;
    });

    // Webpack outputs an array for each chunk when using sourcemaps
    // But we need only the entry file
    var entry = chunkFiles[0];
    assets.chunks[chunkName].entry = entry;
    assets.js.push(entry);

    // Gather all css files
    var css = chunkFiles.filter(function(chunkFile){
      // Some chunks may contain content hash in their names, for ex. 'main.css?1e7cac4e4d8b52fd5ccd2541146ef03f'.
      // We must proper handle such cases, so we use regexp testing here
      return /^.css/.test(path.extname(chunkFile));
    });
    assets.chunks[chunkName].css = css;
    assets.css = assets.css.concat(css);
  }

  // Duplicate css assets can occur on occasion if more than one chunk
  // requires the same css.
  assets.css = _.uniq(assets.css);

  return assets;
};

/**
 * Inject the assets into the given html string
 */
HtmlWebpackPlugin.prototype.appendAssetsToHtml = function(html, templateParams, chunks) {
  var assets = templateParams.htmlWebpackPlugin.files;
  // If chunks is set to true append all chunks
  if (chunks === true) {
    chunks = Object.keys(assets.chunks);
  }
  // Gather all css and script files
  var styles = [];
  var scripts = [];
  chunks.forEach(function(chunkName) {
    styles = styles.concat(assets.chunks[chunkName].css);
    scripts.push(assets.chunks[chunkName].entry);
  });
  // Turn script files into script tags
  scripts = scripts.map(function(scriptPath) {
    return '<script src="' + scriptPath + '?' + templateParams.hash + '"></script>';
  });
  // Turn css files into link tags
  styles = styles.map(function(stylePath) {
    return '<link href="' + stylePath + '?' + templateParams.hash + '" rel="stylesheet">';
  });
  // Append scripts
  html = html.replace(/(<\/body>)/i, function (match, start) {
    return scripts.join('') + match;
  });
  // Append styles
  html = html.replace(/(<\/head>)/i, function (match, start) {
    return styles.join('') + match;
  });
  // Append manifest
  if (assets.manifest) {
    html = html.replace(/(<html.*)(>)/i, function (match, start, end) {
      // Don't append a manifest if a manifest was already specified
      if (match.test(/\smanifest\s*=/)) {
        return match;
      }
      return start + ' manifest="' + assets.manifest + '?' + templateParams.hash + '"' + end;
    });
  }
  return html;
};

/**
 * A helper to support the templates written for html-webpack-plugin <= 1.1.0
 */
HtmlWebpackPlugin.prototype.htmlWebpackPluginLegacyAssets = function(compilation, webpackStatsJson) {
  var assets = this.htmlWebpackPluginAssets(compilation, webpackStatsJson);
  var legacyAssets = {};
  Object.keys(assets.chunks).forEach(function(chunkName){
    legacyAssets[chunkName] = assets.chunks[chunkName].entry;
  });
  return legacyAssets;
};



module.exports = HtmlWebpackPlugin;