/**
 * @license
 * 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.
 */

import {CommentRange} from '../../../types/common';
import {FILE, LineNumber} from './gr-diff-line';
import {Side} from '../../../constants/constants';

/**
 * Compare two ranges. Either argument may be falsy, but will only return
 * true if both are falsy or if neither are falsy and have the same position
 * values.
 */
export function rangesEqual(a?: CommentRange, b?: CommentRange): boolean {
  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
  );
}

export function getLineNumber(lineEl?: Element | null): LineNumber | null {
  if (!lineEl) return null;
  const lineNumberStr = lineEl.getAttribute('data-value');
  if (!lineNumberStr) return null;
  if (lineNumberStr === FILE) return FILE;
  const lineNumber = Number(lineNumberStr);
  return Number.isInteger(lineNumber) ? lineNumber : null;
}

export function getLine(threadEl: HTMLElement): LineNumber {
  const lineAtt = threadEl.getAttribute('line-num');
  if (!lineAtt || lineAtt === 'FILE') return FILE;
  const line = Number(lineAtt);
  if (isNaN(line)) throw new Error(`cannot parse line number: ${lineAtt}`);
  if (line < 1) throw new Error(`line number smaller than 1: ${line}`);
  return line;
}

export function getSide(threadEl: HTMLElement): Side | undefined {
  const sideAtt = threadEl.getAttribute('comment-side');
  if (!sideAtt) {
    console.warn('comment thread without side');
    return undefined;
  }
  if (sideAtt !== Side.LEFT && sideAtt !== Side.RIGHT)
    throw Error(`unexpected value for side: ${sideAtt}`);
  return sideAtt as Side;
}

export function getRange(threadEl: HTMLElement): CommentRange | undefined {
  const rangeAtt = threadEl.getAttribute('range');
  if (!rangeAtt) return undefined;
  const range = JSON.parse(rangeAtt) as CommentRange;
  if (!range.start_line) throw new Error(`invalid range: ${rangeAtt}`);
  return range;
}

// TODO: This type should be exposed to gr-diff clients in a separate type file.
// For Gerrit these are instances of GrCommentThread, but other gr-diff users
// have different HTML elements in use for comment threads.
// TODO: Also document the required HTML attritbutes that thread elements must
// have, e.g. 'comment-side', 'range', 'line-num', 'data-value'.
export interface GrDiffThreadElement extends HTMLElement {
  rootId: string;
}

export function isThreadEl(node: Node): node is GrDiffThreadElement {
  return (
    node.nodeType === Node.ELEMENT_NODE &&
    (node as Element).classList.contains('comment-thread')
  );
}