// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import 'chrome://resources/cr_elements/hidden_style_css.m.js';
import 'chrome://resources/cr_elements/shared_vars_css.m.js';
import 'chrome://resources/polymer/v3_0/paper-styles/color.js';
import './strings.m.js';

import {I18nBehavior} from 'chrome://resources/js/i18n_behavior.m.js';
import {loadTimeData} from 'chrome://resources/js/load_time_data.m.js';
import {html, Polymer} from 'chrome://resources/polymer/v3_0/polymer/polymer_bundled.min.js';


/**
 * @param {number} totalCount
 * @param {number} oppositeCount
 * @return {number}
 */
function visibleLineCount(totalCount, oppositeCount) {
  // We limit the number of lines shown for DOM performance.
  const MAX_VISIBLE_LINES = 1000;
  const max =
      Math.max(MAX_VISIBLE_LINES / 2, MAX_VISIBLE_LINES - oppositeCount);
  return Math.min(max, totalCount);
}

Polymer({
  is: 'extensions-code-section',

  _template: html`{__html_template__}`,

  behaviors: [I18nBehavior],

  properties: {
    /**
     * The code this object is displaying.
     * @type {?chrome.developerPrivate.RequestFileSourceResponse}
     */
    code: {
      type: Object,
      value: null,
    },

    isActive: Boolean,

    /** @private Highlighted code. */
    highlighted_: String,

    /** @private Code before the highlighted section. */
    before_: String,

    /** @private Code after the highlighted section. */
    after_: String,

    /** @private */
    showNoCode_: {
      type: Boolean,
      computed: 'computeShowNoCode_(isActive, highlighted_)',
    },

    /** @private Description for the highlighted section. */
    highlightDescription_: String,

    /** @private */
    lineNumbers_: String,

    /** @private */
    truncatedBefore_: Number,

    /** @private */
    truncatedAfter_: Number,

    /**
     * The string to display if no |code| is set (e.g. because we couldn't
     * load the relevant source file).
     * @type {string}
     */
    couldNotDisplayCode: String,
  },

  observers: [
    'onCodeChanged_(code.*)',
  ],

  /**
   * @private
   */
  onCodeChanged_() {
    if (!this.code ||
        (!this.code.beforeHighlight && !this.code.highlight &&
         !this.code.afterHighlight)) {
      this.highlighted_ = '';
      this.highlightDescription_ = '';
      this.before_ = '';
      this.after_ = '';
      this.lineNumbers_ = '';
      return;
    }

    const before = this.code.beforeHighlight;
    const highlight = this.code.highlight;
    const after = this.code.afterHighlight;

    const linesBefore = before ? before.split('\n') : [];
    const linesAfter = after ? after.split('\n') : [];
    const visibleLineCountBefore =
        visibleLineCount(linesBefore.length, linesAfter.length);
    const visibleLineCountAfter =
        visibleLineCount(linesAfter.length, linesBefore.length);

    const visibleBefore =
        linesBefore.slice(linesBefore.length - visibleLineCountBefore)
            .join('\n');
    let visibleAfter = linesAfter.slice(0, visibleLineCountAfter).join('\n');
    // If the last character is a \n, force it to be rendered.
    if (visibleAfter.charAt(visibleAfter.length - 1) === '\n') {
      visibleAfter += ' ';
    }

    this.highlighted_ = highlight;
    this.highlightDescription_ = this.getAccessibilityHighlightDescription_(
        linesBefore.length, highlight.split('\n').length);
    this.before_ = visibleBefore;
    this.after_ = visibleAfter;
    this.truncatedBefore_ = linesBefore.length - visibleLineCountBefore;
    this.truncatedAfter_ = linesAfter.length - visibleLineCountAfter;

    const visibleCode = visibleBefore + highlight + visibleAfter;

    this.setLineNumbers_(
        this.truncatedBefore_ + 1,
        this.truncatedBefore_ + visibleCode.split('\n').length);
    this.scrollToHighlight_(visibleLineCountBefore);
  },

  /**
   * @param {number} lineCount
   * @param {string} stringSingular
   * @param {string} stringPluralTemplate
   * @return {string}
   * @private
   */
  getLinesNotShownLabel_(lineCount, stringSingular, stringPluralTemplate) {
    return lineCount === 1 ?
        stringSingular :
        loadTimeData.substituteString(stringPluralTemplate, lineCount);
  },

  /**
   * @param {number} start
   * @param {number} end
   * @private
   */
  setLineNumbers_(start, end) {
    let lineNumbers = '';
    for (let i = start; i <= end; ++i) {
      lineNumbers += i + '\n';
    }

    this.lineNumbers_ = lineNumbers;
  },

  /**
   * @param {number} linesBeforeHighlight
   * @private
   */
  scrollToHighlight_(linesBeforeHighlight) {
    const CSS_LINE_HEIGHT = 20;

    // Count how many pixels is above the highlighted code.
    const highlightTop = linesBeforeHighlight * CSS_LINE_HEIGHT;

    // Find the position to show the highlight roughly in the middle.
    const targetTop = highlightTop - this.clientHeight * 0.5;

    this.$['scroll-container'].scrollTo({top: targetTop});
  },

  /**
   * @param {number} lineStart
   * @param {number} numLines
   * @return {string}
   * @private
   */
  getAccessibilityHighlightDescription_(lineStart, numLines) {
    if (numLines > 1) {
      return this.i18n(
          'accessibilityErrorMultiLine', lineStart.toString(),
          (lineStart + numLines - 1).toString());
    } else {
      return this.i18n('accessibilityErrorLine', lineStart.toString());
    }
  },

  /**
   * @private
   * @return {boolean}
   */
  computeShowNoCode_() {
    return this.isActive && !this.highlighted_;
  },
});