const CommentModel = require('../models/comment');

const debug = require('debug')('talk:services:comments');
const ActionsService = require('./actions');
const SettingsService = require('./settings');

const cloneDeep = require('lodash/cloneDeep');
const errors = require('../errors');
const events = require('./events');
const merge = require('lodash/merge');
const { COMMENTS_NEW, COMMENTS_EDIT } = require('./events/constants');

module.exports = class CommentsService {
  /**
   * Creates a new Comment that came from a public source.
   * @param  {Object} input either a single comment or an array of comments.
   * @return {Promise}
   */
  static async publicCreate(input) {
    // Extract the parent_id from the comment, if there is one.
    const { status = 'NONE', parent_id = null } = input;
    const created_at = new Date();

    // Check to see if we are replying to a comment, and if that comment is
    // visible.
    if (parent_id !== null) {
      const parent = await CommentModel.findOne({ id: parent_id });
      if (parent === null || !parent.visible) {
        throw errors.ErrParentDoesNotVisible;
      }
    }

    // Create the comment in the database.
    const comment = await CommentModel.create(
      merge(
        {
          status_history: status
            ? [
                {
                  type: status,
                  created_at,
                },
              ]
            : [],
          body_history: [
            {
              body: input.body,
              created_at,
            },
          ],
        },
        input
      )
    );

    // Emit that the comment was created!
    await events.emitAsync(COMMENTS_NEW, comment);

    return comment;
  }

  /**
   * lastUnmoderatedStatus will retrieve the last status before this one.
   *
   * @param {Object} comment the comment to get the last status of
   */
  static lastUnmoderatedStatus(comment) {
    const UNMODERATED_STATUSES = ['NONE', 'PREMOD'];

    for (let i = comment.status_history.length - 1; i >= 0; i--) {
      const { type } = comment.status_history[i];

      if (UNMODERATED_STATUSES.includes(type)) {
        return type;
      }
    }
  }

  /**
   * Edit a Comment.
   *
   * @param {String} id         comment.id you want to edit (or its ID)
   * @param {String} author_id  user.id of the user trying to edit the comment (will err if not comment author)
   * @param {String} body       the new Comment body
   * @param {String} status     the new Comment status
   */
  static async edit({ id, author_id, body, status }) {
    const EDITABLE_STATUSES = ['NONE', 'PREMOD', 'ACCEPTED'];
    const created_at = new Date();

    const query = {
      id,
      author_id,
      status: {
        $in: EDITABLE_STATUSES,
      },
    };

    // Establish the edit window (if it exists) and add the condition to the
    // original query.
    const {
      editCommentWindowLength: editWindowMs,
    } = await SettingsService.retrieve();
    const lastEditableCommentCreatedAt = new Date(Date.now() - editWindowMs);
    query.created_at = {
      $gt: lastEditableCommentCreatedAt,
    };

    const originalComment = await CommentModel.findOneAndUpdate(query, {
      $set: {
        body,
        status,
      },
      $push: {
        body_history: {
          body,
          created_at,
        },
        status_history: {
          type: status,
          created_at,
        },
      },
    });

    if (originalComment == null) {
      // Try to get the comment.
      const comment = await CommentsService.findById(id);
      if (comment == null) {
        debug('rejecting comment edit because comment was not found');
        throw errors.ErrNotFound;
      }

      // Check to see if the user was't allowed to edit it.
      if (comment.author_id !== author_id) {
        debug(
          'rejecting comment edit because author id does not match editing user'
        );
        throw errors.ErrNotAuthorized;
      }

      // Check to see if the comment had a status that was editable.
      if (!EDITABLE_STATUSES.includes(comment.status)) {
        debug(
          'rejecting comment edit because original comment has a non-editable status'
        );
        throw errors.ErrNotAuthorized;
      }

      // Check to see if the edit window expired.
      if (comment.created_at <= lastEditableCommentCreatedAt) {
        debug('rejecting comment edit because outside edit time window');
        throw errors.ErrEditWindowHasEnded;
      }

      throw new Error('comment edit failed for an unexpected reason');
    }

    // Mutate the comment like Mongo would have.
    const editedComment = cloneDeep(originalComment);
    editedComment.status = status;
    editedComment.body = body;
    editedComment.body_history.push({
      body,
      created_at,
    });
    editedComment.status_history.push({
      type: status,
      created_at,
    });

    await events.emitAsync(COMMENTS_EDIT, originalComment, editedComment);

    return editedComment;
  }

  /**
   * Finds a comment by the id.
   * @param {String} id  identifier of comment (uuid)
   * @return {Promise}
   */
  static findById(id) {
    return CommentModel.findOne({ id });
  }

  /**
   * Finds ALL the comments by the asset_id.
   * @param {String} asset_id  identifier of the asset which owns this comment (uuid)
   * @return {Promise}
   */
  static findByAssetId(asset_id) {
    return CommentModel.find({
      asset_id,
    });
  }

  /**
   * findByAssetIdWithStatuses finds all the comments where the asset id matches
   * what's provided and the status is one of the ones listed in the statuses
   * array.
   * @param {String} asset_id      the asset id to search by
   * @param {Array}  [statuses=[]] the array of statuses to search by
   * @return {Promise}             resolves to an array of comments
   */
  static findByAssetIdWithStatuses(asset_id, statuses = []) {
    return CommentModel.find({
      asset_id,
      status: {
        $in: statuses,
      },
    });
  }

  /**
   * Find comments by an action that was performed on them.
   * @param {String} action_type the type of action that was performed on the comment
   * @return {Promise}
   */
  static findByActionType(action_type) {
    return ActionsService.findCommentsIdByActionType(
      action_type,
      'COMMENTS'
    ).then(actions =>
      CommentModel.find({
        id: {
          $in: actions.map(a => a.item_id),
        },
      })
    );
  }

  /**
   * Find comment id's where the action type matches the argument.
   * @param {String} action_type the type of action that was performed on the comment
   * @return {Promise}
   */
  static findIdsByActionType(action_type) {
    return ActionsService.findCommentsIdByActionType(
      action_type,
      'COMMENTS'
    ).then(actions => actions.map(a => a.item_id));
  }

  /**
   * Find comments by current status
   * @param {String} status status of the comment to search for
   * @return {Promise} resovles to comment array
   */
  static findByStatus(status = 'NONE') {
    return CommentModel.find({ status });
  }

  /**
   * Pushes a new status in for the user.
   * @param {String} id          identifier of the comment  (uuid)
   * @param {String} status      the new status of the comment
   * @param {String} assigned_by the user id for the user who performed the
   *                             moderation action
   * @return {Promise}
   */
  static async pushStatus(id, status, assigned_by = null) {
    const created_at = new Date();
    const originalComment = await CommentModel.findOneAndUpdate(
      { id },
      {
        $push: {
          status_history: {
            type: status,
            created_at,
            assigned_by,
          },
        },
        $set: { status },
      }
    );

    if (originalComment == null) {
      throw errors.ErrNotFound;
    }

    const editedComment = new CommentModel(originalComment.toObject());
    editedComment.status_history.push({
      type: status,
      created_at,
      assigned_by,
    });
    editedComment.status = status;

    // Emit that the comment was edited, and pass the original comment and the
    // edited comment.
    await events.emitAsync(COMMENTS_EDIT, originalComment, editedComment);

    return editedComment;
  }

  /**
   * Add an action to the comment.
   * @param {String} item_id  identifier of the comment  (uuid)
   * @param {String} user_id  user id of the action (uuid)
   * @param {String} action the new action to the comment
   * @return {Promise}
   */
  static addAction(item_id, user_id, action_type, metadata = {}) {
    return ActionsService.create({
      item_id,
      item_type: 'COMMENTS',
      user_id,
      action_type,
      metadata,
    });
  }
};

//==============================================================================
// Event Hooks
//==============================================================================

const incrReplyCount = async (comment, value) => {
  try {
    await CommentModel.update(
      {
        id: comment.parent_id,
      },
      {
        $inc: {
          reply_count: value,
        },
      }
    );
  } catch (err) {
    console.error("Can't mutate the reply count:", err);
  }
};

// When a comment is created, if it is a reply, increment the reply count on the
// parent's document.
events.on(COMMENTS_NEW, async comment => {
  if (
    !comment || // Check that the comment is defined.
    (!comment.parent_id || comment.parent_id.length === 0) || // Check that the comment has a parent (is a reply).
    !(comment.status === 'NONE' || comment.status === 'ACCEPTED') // Check that the comment is visible.
  ) {
    return;
  }

  return incrReplyCount(comment, 1);
});

// When a comment is edited, if the visability changed publicly, then modify the
// comment.
events.on(COMMENTS_EDIT, async (originalComment, editedComment) => {
  if (
    !editedComment || // Check that the comment is defined.
    (!editedComment.parent_id || editedComment.parent_id.length === 0) // Check that the comment has a parent (is a reply).
  ) {
    return;
  }

  // If the comment was visible before, and now it isn't, decrement the count;
  if (originalComment.visible && !editedComment.visible) {
    return incrReplyCount(editedComment, -1);
  }

  // If the comment was not visible before, and now it is, increment the count.
  if (!originalComment.visible && editedComment.visible) {
    return incrReplyCount(editedComment, 1);
  }
});