/**
 * @license
 * Copyright (C) 2016 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.
 */
import '../../../styles/shared-styles.js';
import '../gr-selection-action-box/gr-selection-action-box.js';
import {dom} from '@polymer/polymer/lib/legacy/polymer.dom.js';
import {GestureEventListeners} from '@polymer/polymer/lib/mixins/gesture-event-listeners.js';
import {LegacyElementMixin} from '@polymer/polymer/lib/legacy/legacy-element-mixin.js';
import {PolymerElement} from '@polymer/polymer/polymer-element.js';
import {htmlTemplate} from './gr-diff-highlight_html.js';
import {GrAnnotation} from './gr-annotation.js';
import {GrRangeNormalizer} from './gr-range-normalizer.js';

/**
 * @extends PolymerElement
 */
class GrDiffHighlight extends GestureEventListeners(
    LegacyElementMixin(PolymerElement)) {
  static get template() { return htmlTemplate; }

  static get is() { return 'gr-diff-highlight'; }

  static get properties() {
    return {
    /** @type {!Array<!Gerrit.HoveredRange>} */
      commentRanges: {
        type: Array,
        notify: true,
      },
      loggedIn: Boolean,
      /**
       * querySelector can return null, so needs to be nullable.
       *
       * @type {?HTMLElement}
       * */
      _cachedDiffBuilder: Object,

      /**
       * Which range is currently selected by the user.
       * Stored in order to add a range-based comment
       * later.
       * undefined if no range is selected.
       *
       * @type {{side: string, range: Gerrit.Range}|undefined}
       */
      selectedRange: {
        type: Object,
        notify: true,
      },
    };
  }

  /** @override */
  created() {
    super.created();
    this.addEventListener('comment-thread-mouseleave',
        e => this._handleCommentThreadMouseleave(e));
    this.addEventListener('comment-thread-mouseenter',
        e => this._handleCommentThreadMouseenter(e));
    this.addEventListener('create-comment-requested',
        e => this._handleRangeCommentRequest(e));
  }

  get diffBuilder() {
    if (!this._cachedDiffBuilder) {
      this._cachedDiffBuilder =
          dom(this).querySelector('gr-diff-builder');
    }
    return this._cachedDiffBuilder;
  }

  /**
   * Determines side/line/range for a DOM selection and shows a tooltip.
   *
   * With native shadow DOM, gr-diff-highlight cannot access a selection that
   * references the DOM elements making up the diff because they are in the
   * shadow DOM the gr-diff element. For this reason, we listen to the
   * selectionchange event and retrieve the selection in gr-diff, and then
   * call this method to process the Selection.
   *
   * @param {Selection} selection A DOM Selection living in the shadow DOM of
   *     the diff element.
   * @param {boolean} isMouseUp If true, this is called due to a mouseup
   *     event, in which case we might want to immediately create a comment,
   *     because isMouseUp === true combined with an existing selection must
   *     mean that this is the end of a double-click.
   */
  handleSelectionChange(selection, isMouseUp) {
    // Debounce is not just nice for waiting until the selection has settled,
    // it is also vital for being able to click on the action box before it is
    // removed.
    // If you wait longer than 50 ms, then you don't properly catch a very
    // quick 'c' press after the selection change. If you wait less than 10
    // ms, then you will have about 50 _handleSelection calls when doing a
    // simple drag for select.
    this.debounce(
        'selectionChange', () => this._handleSelection(selection, isMouseUp),
        10);
  }

  _getThreadEl(e) {
    const path = dom(e).path || [];
    for (const pathEl of path) {
      if (pathEl.classList.contains('comment-thread')) return pathEl;
    }
    return null;
  }

  _handleCommentThreadMouseenter(e) {
    const threadEl = this._getThreadEl(e);
    const index = this._indexForThreadEl(threadEl);

    if (index !== undefined) {
      this.set(['commentRanges', index, 'hovering'], true);
    }
  }

  _handleCommentThreadMouseleave(e) {
    const threadEl = this._getThreadEl(e);
    const index = this._indexForThreadEl(threadEl);

    if (index !== undefined) {
      this.set(['commentRanges', index, 'hovering'], false);
    }
  }

  _indexForThreadEl(threadEl) {
    const side = threadEl.getAttribute('comment-side');
    const range = JSON.parse(threadEl.getAttribute('range'));

    if (!range) return undefined;

    return this._indexOfCommentRange(side, range);
  }

  _indexOfCommentRange(side, range) {
    function rangesEqual(a, b) {
      if (!a && !b) {
        return true;
      }
      if (!a || !b) {
        return false;
      }
      return a.start_line === b.start_line &&
          a.start_character === b.start_character &&
          a.end_line === b.end_line &&
          a.end_character === b.end_character;
    }

    return this.commentRanges.findIndex(commentRange =>
      commentRange.side === side && rangesEqual(commentRange.range, range));
  }

  /**
   * Get current normalized selection.
   * Merges multiple ranges, accounts for triple click, accounts for
   * syntax highligh, convert native DOM Range objects to Gerrit concepts
   * (line, side, etc).
   *
   * @param {Selection} selection
   * @return {({
   *   start: {
   *     node: Node,
   *     side: string,
   *     line: Number,
   *     column: Number
   *   },
   *   end: {
   *     node: Node,
   *     side: string,
   *     line: Number,
   *     column: Number
   *   }
   * })|null|!Object}
   */
  _getNormalizedRange(selection) {
    const rangeCount = selection.rangeCount;
    if (rangeCount === 0) {
      return null;
    } else if (rangeCount === 1) {
      return this._normalizeRange(selection.getRangeAt(0));
    } else {
      const startRange = this._normalizeRange(selection.getRangeAt(0));
      const endRange = this._normalizeRange(
          selection.getRangeAt(rangeCount - 1));
      return {
        start: startRange.start,
        end: endRange.end,
      };
    }
  }

  /**
   * Normalize a specific DOM Range.
   *
   * @return {!Object} fixed normalized range
   */
  _normalizeRange(domRange) {
    const range = GrRangeNormalizer.normalize(domRange);
    return this._fixTripleClickSelection({
      start: this._normalizeSelectionSide(
          range.startContainer, range.startOffset),
      end: this._normalizeSelectionSide(
          range.endContainer, range.endOffset),
    }, domRange);
  }

  /**
   * Adjust triple click selection for the whole line.
   * A triple click always results in:
   * - start.column == end.column == 0
   * - end.line == start.line + 1
   *
   * @param {!Object} range Normalized range, ie column/line numbers
   * @param {!Range} domRange DOM Range object
   * @return {!Object} fixed normalized range
   */
  _fixTripleClickSelection(range, domRange) {
    if (!range.start) {
      // Selection outside of current diff.
      return range;
    }
    const start = range.start;
    const end = range.end;
    // Happens when triple click in side-by-side mode with other side empty.
    const endsAtOtherEmptySide = !end &&
        domRange.endOffset === 0 &&
        domRange.endContainer.nodeName === 'TD' &&
        (domRange.endContainer.classList.contains('left') ||
         domRange.endContainer.classList.contains('right'));
    const endsAtBeginningOfNextLine = end &&
        start.column === 0 &&
        end.column === 0 &&
        end.line === start.line + 1;
    const content = domRange.cloneContents().querySelector('.contentText');
    const lineLength = content && this._getLength(content) || 0;
    if (lineLength && (endsAtBeginningOfNextLine || endsAtOtherEmptySide)) {
      // Move the selection to the end of the previous line.
      range.end = {
        node: start.node,
        column: lineLength,
        side: start.side,
        line: start.line,
      };
    }
    return range;
  }

  /**
   * Convert DOM Range selection to concrete numbers (line, column, side).
   * Moves range end if it's not inside td.content.
   * Returns null if selection end is not valid (outside of diff).
   *
   * @param {Node} node td.content child
   * @param {number} offset offset within node
   * @return {({
   *   node: Node,
   *   side: string,
   *   line: Number,
   *   column: Number
   * }|undefined)}
   */
  _normalizeSelectionSide(node, offset) {
    let column;
    if (!this.contains(node)) {
      return;
    }
    const lineEl = this.diffBuilder.getLineElByChild(node);
    if (!lineEl) {
      return;
    }
    const side = this.diffBuilder.getSideByLineEl(lineEl);
    if (!side) {
      return;
    }
    const line = this.diffBuilder.getLineNumberByChild(lineEl);
    if (!line) {
      return;
    }
    const contentTd = this.diffBuilder.getContentTdByLineEl(lineEl);
    const contentText = contentTd.querySelector('.contentText');
    if (!contentTd.contains(node)) {
      node = contentText;
      column = 0;
    } else {
      const thread = contentTd.querySelector('.comment-thread');
      if (thread && thread.contains(node)) {
        column = this._getLength(contentText);
        node = contentText;
      } else {
        column = this._convertOffsetToColumn(node, offset);
      }
    }

    return {
      node,
      side,
      line,
      column,
    };
  }

  /**
   * The only line in which add a comment tooltip is cut off is the first
   * line. Even if there is a collapsed section, The first visible line is
   * in the position where the second line would have been, if not for the
   * collapsed section, so don't need to worry about this case for
   * positioning the tooltip.
   */
  _positionActionBox(actionBox, startLine, range) {
    if (startLine > 1) {
      actionBox.placeAbove(range);
      return;
    }
    actionBox.positionBelow = true;
    actionBox.placeBelow(range);
  }

  _isRangeValid(range) {
    if (!range || !range.start || !range.end) {
      return false;
    }
    const start = range.start;
    const end = range.end;
    return !(start.side !== end.side ||
        end.line < start.line ||
        (start.line === end.line && start.column === end.column));
  }

  _handleSelection(selection, isMouseUp) {
    const normalizedRange = this._getNormalizedRange(selection);
    if (!this._isRangeValid(normalizedRange)) {
      this._removeActionBox();
      return;
    }
    const domRange = selection.getRangeAt(0);
    const start = normalizedRange.start;
    const end = normalizedRange.end;

    // TODO (viktard): Drop empty first and last lines from selection.

    // If the selection is from the end of one line to the start of the next
    // line, then this must have been a double-click, or you have started
    // dragging. Showing the action box is bad in the former case and not very
    // useful in the latter, so never do that.
    // If this was a mouse-up event, we create a comment immediately if
    // the selection is from the end of a line to the start of the next line.
    // In a perfect world we would only do this for double-click, but it is
    // extremely rare that a user would drag from the end of one line to the
    // start of the next and release the mouse, so we don't bother.
    // TODO(brohlfs): This does not work, if the double-click is before a new
    // diff chunk (start will be equal to end), and neither before an "expand
    // the diff context" block (end line will match the first line of the new
    // section and thus be greater than start line + 1).
    if (start.line === end.line - 1 && end.column === 0) {
      // Rather than trying to find the line contents (for comparing
      // start.column with the content length), we just check if the selection
      // is empty to see that it's at the end of a line.
      const content = domRange.cloneContents().querySelector('.contentText');
      if (isMouseUp && this._getLength(content) === 0) {
        this._fireCreateRangeComment(start.side, {
          start_line: start.line,
          start_character: 0,
          end_line: start.line,
          end_character: start.column,
        });
      }
      return;
    }

    let actionBox = this.shadowRoot.querySelector('gr-selection-action-box');
    if (!actionBox) {
      actionBox = document.createElement('gr-selection-action-box');
      const root = dom(this.root);
      root.insertBefore(actionBox, root.firstElementChild);
    }
    this.selectedRange = {
      range: {
        start_line: start.line,
        start_character: start.column,
        end_line: end.line,
        end_character: end.column,
      },
      side: start.side,
    };
    if (start.line === end.line) {
      this._positionActionBox(actionBox, start.line, domRange);
    } else if (start.node instanceof Text) {
      if (start.column) {
        this._positionActionBox(actionBox, start.line,
            start.node.splitText(start.column));
      }
      start.node.parentElement.normalize(); // Undo splitText from above.
    } else if (start.node.classList.contains('content') &&
        start.node.firstChild) {
      this._positionActionBox(actionBox, start.line, start.node.firstChild);
    } else {
      this._positionActionBox(actionBox, start.line, start.node);
    }
  }

  _fireCreateRangeComment(side, range) {
    this.dispatchEvent(new CustomEvent('create-range-comment', {
      detail: {side, range},
      composed: true, bubbles: true,
    }));
    this._removeActionBox();
  }

  _handleRangeCommentRequest(e) {
    e.stopPropagation();
    if (!this.selectedRange) {
      throw Error('Selected Range is needed for new range comment!');
    }
    const {side, range} = this.selectedRange;
    this._fireCreateRangeComment(side, range);
  }

  _removeActionBox() {
    this.selectedRange = undefined;
    const actionBox = this.shadowRoot
        .querySelector('gr-selection-action-box');
    if (actionBox) {
      dom(this.root).removeChild(actionBox);
    }
  }

  _convertOffsetToColumn(el, offset) {
    if (el instanceof Element && el.classList.contains('content')) {
      return offset;
    }
    while (el.previousSibling ||
        !el.parentElement.classList.contains('content')) {
      if (el.previousSibling) {
        el = el.previousSibling;
        offset += this._getLength(el);
      } else {
        el = el.parentElement;
      }
    }
    return offset;
  }

  /**
   * Traverse Element from right to left, call callback for each node.
   * Stops if callback returns true.
   *
   * @param {!Element} startNode
   * @param {function(Node):boolean} callback
   * @param {Object=} opt_flags If flags.left is true, traverse left.
   */
  _traverseContentSiblings(startNode, callback, opt_flags) {
    const travelLeft = opt_flags && opt_flags.left;
    let node = startNode;
    while (node) {
      if (node instanceof Element &&
          node.tagName !== 'HL' &&
          node.tagName !== 'SPAN') {
        break;
      }
      const nextNode = travelLeft ? node.previousSibling : node.nextSibling;
      if (callback(node)) {
        break;
      }
      node = nextNode;
    }
  }

  /**
   * Get length of a node. If the node is a content node, then only give the
   * length of its .contentText child.
   *
   * @param {?Element} node this is sometimes passed as null.
   * @return {number}
   */
  _getLength(node) {
    if (node instanceof Element && node.classList.contains('content')) {
      return this._getLength(node.querySelector('.contentText'));
    } else {
      return GrAnnotation.getLength(node);
    }
  }
}

customElements.define(GrDiffHighlight.is, GrDiffHighlight);