// Copyright (C) 2020 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
(function() {
  'use strict';

  const DiffViewMode = {
    SIDE_BY_SIDE: 'SIDE_BY_SIDE',
    UNIFIED: 'UNIFIED_DIFF',
  };

  const TRAILING_WHITESPACE_PATTERN = /\s+$/;

  /**
   * @appliesMixin Gerrit.FireMixin
   */
  class GrDiffBuilderElement extends Polymer.mixinBehaviors( [
    Gerrit.FireBehavior,
  ], Polymer.GestureEventListeners(
      Polymer.LegacyElementMixin(
          Polymer.Element))) {
    static get is() { return 'gr-diff-builder'; }
    /**
     * Fired when the diff begins rendering.
     *
     * @event render-start
     */

    /**
     * Fired when the diff finishes rendering text content.
     *
     * @event render-content
     */

    static get properties() {
      return {
        diff: Object,
        changeNum: String,
        patchNum: String,
        viewMode: String,
        isImageDiff: Boolean,
        baseImage: Object,
        revisionImage: Object,
        parentIndex: Number,
        path: String,
        projectName: String,

        _builder: Object,
        _groups: Array,
        _layers: Array,
        _showTabs: Boolean,
        /** @type {!Array<!Gerrit.HoveredRange>} */
        commentRanges: {
          type: Array,
          value: () => [],
        },
        /** @type {!Array<!Gerrit.CoverageRange>} */
        coverageRanges: {
          type: Array,
          value: () => [],
        },
        _leftCoverageRanges: {
          type: Array,
          computed: '_computeLeftCoverageRanges(coverageRanges)',
        },
        _rightCoverageRanges: {
          type: Array,
          computed: '_computeRightCoverageRanges(coverageRanges)',
        },
        /**
         * The promise last returned from `render()` while the asynchronous
         * rendering is running - `null` otherwise. Provides a `cancel()`
         * method that rejects it with `{isCancelled: true}`.
         *
         * @type {?Object}
         */
        _cancelableRenderPromise: Object,
        layers: {
          type: Array,
          value: [],
        },
      };
    }

    get diffElement() {
      return this.queryEffectiveChildren('#diffTable');
    }

    static get observers() {
      return [
        '_groupsChanged(_groups.splices)',
      ];
    }

    _computeLeftCoverageRanges(coverageRanges) {
      return coverageRanges.filter(range => range && range.side === 'left');
    }

    _computeRightCoverageRanges(coverageRanges) {
      return coverageRanges.filter(range => range && range.side === 'right');
    }

    render(keyLocations, prefs) {
      // Setting up annotation layers must happen after plugins are
      // installed, and |render| satisfies the requirement, however,
      // |attached| doesn't because in the diff view page, the element is
      // attached before plugins are installed.
      this._setupAnnotationLayers();

      this._showTabs = !!prefs.show_tabs;
      this._showTrailingWhitespace = !!prefs.show_whitespace_errors;

      // Stop the processor if it's running.
      this.cancel();

      this._builder = this._getDiffBuilder(this.diff, prefs);

      this.$.processor.context = prefs.context;
      this.$.processor.keyLocations = keyLocations;

      this._clearDiffContent();
      this._builder.addColumns(this.diffElement, prefs.font_size);

      const isBinary = !!(this.isImageDiff || this.diff.binary);

      this.dispatchEvent(new CustomEvent(
          'render-start', {bubbles: true, composed: true}));
      this._cancelableRenderPromise = util.makeCancelable(
          this.$.processor.process(this.diff.content, isBinary)
              .then(() => {
                if (this.isImageDiff) {
                  this._builder.renderDiff();
                }
                this.dispatchEvent(new CustomEvent('render-content',
                    {bubbles: true, composed: true}));
              }));
      return this._cancelableRenderPromise
          .finally(() => { this._cancelableRenderPromise = null; })
      // Mocca testing does not like uncaught rejections, so we catch
      // the cancels which are expected and should not throw errors in
      // tests.
          .catch(e => { if (!e.isCanceled) return Promise.reject(e); });
    }

    _setupAnnotationLayers() {
      const layers = [
        this._createTrailingWhitespaceLayer(),
        this._createIntralineLayer(),
        this._createTabIndicatorLayer(),
        this.$.rangeLayer,
        this.$.coverageLayerLeft,
        this.$.coverageLayerRight,
      ];

      if (this.layers) {
        layers.push(...this.layers);
      }
      this._layers = layers;
    }

    getLineElByChild(node) {
      while (node) {
        if (node instanceof Element) {
          if (node.classList.contains('lineNum')) {
            return node;
          }
          if (node.classList.contains('section')) {
            return null;
          }
        }
        node = node.previousSibling || node.parentElement;
      }
      return null;
    }

    getLineNumberByChild(node) {
      const lineEl = this.getLineElByChild(node);
      return lineEl ?
        parseInt(lineEl.getAttribute('data-value'), 10) :
        null;
    }

    getContentByLine(lineNumber, opt_side, opt_root) {
      return this._builder.getContentByLine(lineNumber, opt_side, opt_root);
    }

    getContentByLineEl(lineEl) {
      const root = Polymer.dom(lineEl.parentElement);
      const side = this.getSideByLineEl(lineEl);
      const line = lineEl.getAttribute('data-value');
      return this.getContentByLine(line, side, root);
    }

    getLineElByNumber(lineNumber, opt_side) {
      const sideSelector = opt_side ? ('.' + opt_side) : '';
      return this.diffElement.querySelector(
          '.lineNum[data-value="' + lineNumber + '"]' + sideSelector);
    }

    getContentsByLineRange(startLine, endLine, opt_side) {
      const result = [];
      this._builder.findLinesByRange(startLine, endLine, opt_side, null,
          result);
      return result;
    }

    getSideByLineEl(lineEl) {
      return lineEl.classList.contains(GrDiffBuilder.Side.RIGHT) ?
        GrDiffBuilder.Side.RIGHT : GrDiffBuilder.Side.LEFT;
    }

    emitGroup(group, sectionEl) {
      this._builder.emitGroup(group, sectionEl);
    }

    showContext(newGroups, sectionEl) {
      const groups = this._builder.groups;

      const contextIndex = groups.findIndex(group =>
        group.element === sectionEl
      );
      groups.splice(contextIndex, 1, ...newGroups);

      for (const newGroup of newGroups) {
        this._builder.emitGroup(newGroup, sectionEl);
      }
      sectionEl.parentNode.removeChild(sectionEl);

      this.async(() => this.fire('render-content'), 1);
    }

    cancel() {
      this.$.processor.cancel();
      if (this._cancelableRenderPromise) {
        this._cancelableRenderPromise.cancel();
        this._cancelableRenderPromise = null;
      }
    }

    _handlePreferenceError(pref) {
      const message = `The value of the '${pref}' user preference is ` +
          `invalid. Fix in diff preferences`;
      this.dispatchEvent(new CustomEvent('show-alert', {
        detail: {
          message,
        }, bubbles: true, composed: true}));
      throw Error(`Invalid preference value: ${pref}`);
    }

    _getDiffBuilder(diff, prefs) {
      if (isNaN(prefs.tab_size) || prefs.tab_size <= 0) {
        this._handlePreferenceError('tab size');
        return;
      }

      if (isNaN(prefs.line_length) || prefs.line_length <= 0) {
        this._handlePreferenceError('diff width');
        return;
      }

      let builder = null;
      if (this.isImageDiff) {
        builder = new GrDiffBuilderImage(diff, prefs, this.diffElement,
            this.baseImage, this.revisionImage);
      } else if (diff.binary) {
        // If the diff is binary, but not an image.
        return new GrDiffBuilderBinary(diff, prefs, this.diffElement);
      } else if (this.viewMode === DiffViewMode.SIDE_BY_SIDE) {
        builder = new GrDiffBuilderSideBySide(diff, prefs, this.diffElement,
            this._layers);
      } else if (this.viewMode === DiffViewMode.UNIFIED) {
        builder = new GrDiffBuilderUnified(diff, prefs, this.diffElement,
            this._layers);
      }
      if (!builder) {
        throw Error('Unsupported diff view mode: ' + this.viewMode);
      }
      return builder;
    }

    _clearDiffContent() {
      this.diffElement.innerHTML = null;
    }

    _groupsChanged(changeRecord) {
      if (!changeRecord) { return; }
      for (const splice of changeRecord.indexSplices) {
        let group;
        for (let i = 0; i < splice.addedCount; i++) {
          group = splice.object[splice.index + i];
          this._builder.groups.push(group);
          this._builder.emitGroup(group);
        }
      }
    }

    _createIntralineLayer() {
      return {
        // Take a DIV.contentText element and a line object with intraline
        // differences to highlight and apply them to the element as
        // annotations.
        annotate(contentEl, lineNumberEl, line) {
          const HL_CLASS = 'style-scope gr-diff intraline';
          for (const highlight of line.highlights) {
            // The start and end indices could be the same if a highlight is
            // meant to start at the end of a line and continue onto the
            // next one. Ignore it.
            if (highlight.startIndex === highlight.endIndex) { continue; }

            // If endIndex isn't present, continue to the end of the line.
            const endIndex = highlight.endIndex === undefined ?
              line.text.length :
              highlight.endIndex;

            GrAnnotation.annotateElement(
                contentEl,
                highlight.startIndex,
                endIndex - highlight.startIndex,
                HL_CLASS);
          }
        },
      };
    }

    _createTabIndicatorLayer() {
      const show = () => this._showTabs;
      return {
        annotate(contentEl, lineNumberEl, line) {
          // If visible tabs are disabled, do nothing.
          if (!show()) { return; }

          // Find and annotate the locations of tabs.
          const split = line.text.split('\t');
          if (!split) { return; }
          for (let i = 0, pos = 0; i < split.length - 1; i++) {
            // Skip forward by the length of the content
            pos += split[i].length;

            GrAnnotation.annotateElement(contentEl, pos, 1,
                'style-scope gr-diff tab-indicator');

            // Skip forward by one tab character.
            pos++;
          }
        },
      };
    }

    _createTrailingWhitespaceLayer() {
      const show = function() {
        return this._showTrailingWhitespace;
      }.bind(this);

      return {
        annotate(contentEl, lineNumberEl, line) {
          if (!show()) { return; }

          const match = line.text.match(TRAILING_WHITESPACE_PATTERN);
          if (match) {
            // Normalize string positions in case there is unicode before or
            // within the match.
            const index = GrAnnotation.getStringLength(
                line.text.substr(0, match.index));
            const length = GrAnnotation.getStringLength(match[0]);
            GrAnnotation.annotateElement(contentEl, index, length,
                'style-scope gr-diff trailing-whitespace');
          }
        },
      };
    }

    setBlame(blame) {
      if (!this._builder || !blame) { return; }
      this._builder.setBlame(blame);
    }
  }

  customElements.define(GrDiffBuilderElement.is, GrDiffBuilderElement);
})();