const UserModel = require('../../../models/user');
const CommentModel = require('../../../models/comment');
const ActionsService = require('../../../services/actions');
const {arrayJoinBy} = require('../../../graph/loaders/util');
const sc = require('snake-case');
const debug = require('debug')('talk:cli:verify');

const MODELS = [
  UserModel,
  CommentModel,
];

async function processBatch(Model, documents) {

  // Get an array of all the document id's.
  const documentIDs = documents.map(({id}) => id);

  // Store all the operations on this batch in this array that we'll return
  // later.
  const operations = [];

  // Get the action summaries for this batch.
  const totalActionSummaries = await ActionsService
    .getActionSummaries(documentIDs)
    .then(arrayJoinBy(documentIDs, 'item_id'));

  // Iterate over the documents.
  for (let i = 0; i < documents.length; i++) {
    const document = documents[i];
    const actionSummaries = totalActionSummaries[i];

    let ops = [];

    for (const actionSummary of actionSummaries) {
      if (actionSummary.group_id === null) {
        continue;
      }

      // And we generate the group id.
      const ACTION_TYPE = sc(actionSummary.action_type.toLowerCase());
      const GROUP_ID = sc(actionSummary.group_id.toLowerCase());

      if (GROUP_ID.length <= 0) {
        continue;
      }

      // And we add a new batch operation if the action summary is associated
      // with a group.
      const ACTION_COUNT_FIELD = `${ACTION_TYPE}_${GROUP_ID}`;

      // Check that the action summaries match the cached counts.
      if (
        !document.action_counts ||
        !(ACTION_COUNT_FIELD in document.action_counts) ||
        document.action_counts[ACTION_COUNT_FIELD] !== actionSummary.count
      ) {

        // Batch updates for those changes.
        ops.push({
          [`action_counts.${ACTION_COUNT_FIELD}`]: actionSummary.count,
        });
      }
    }

    // Group all the action summaries together from all the different group
    // ids.
    let groupedActionSummaries = actionSummaries.reduce((acc, actionSummary) => {
      const ACTION_TYPE = sc(actionSummary.action_type.toLowerCase());

      if (!(ACTION_TYPE in acc)) {
        acc[ACTION_TYPE] = 0;
      }

      acc[ACTION_TYPE] += actionSummary.count;

      return acc;
    }, {});

    for (const ACTION_COUNT_FIELD of Object.keys(groupedActionSummaries)) {
      const count = groupedActionSummaries[ACTION_COUNT_FIELD];

      // Check that the action summaries match the cached counts.
      if (
        !document.action_counts ||
        !(ACTION_COUNT_FIELD in document.action_counts) ||
        document.action_counts[ACTION_COUNT_FIELD] !== count
      ) {

        // Batch updates for those changes.
        ops.push({
          [`action_counts.${ACTION_COUNT_FIELD}`]: count,
        });
      }
    }

    // If this comment has action summaries that should be updated, then
    // perform an update!
    if (ops.length > 0) {
      operations.push({
        updateOne: {
          filter: {
            id: document.id
          },
          update: {
            $set: Object.assign({}, ...ops),
          },
        },
      });
    }
  }

  return operations;
}

module.exports = async ({fix, batch}) => {
  for (const Model of MODELS) {
    const cursor = Model
      .collection
      .find({})
      .project({
        id: 1,
        action_counts: 1
      })
      .sort({created_at: 1});

    let operations = [];
    let documents = [];

    // While there are documents to process.
    while (await cursor.hasNext()) {

      // Load the document.
      const document = await cursor.next();

      // Push the document into the documents array.
      documents.push(document);

      // Check to see if the length of the documents array requires us to
      // process it.
      if (documents.length > batch) {

        // Process this batch.
        let batchOperations = await processBatch(Model, documents);

        // Push the batch operations into the model operations.
        operations.push(...batchOperations);

        // Clear this batch contents.
        documents = [];
      }
    }

    // Check to see if there are any documents left over.
    if (documents.length > 0) {

      // Process this batch.
      let batchOperations = await processBatch(Model, documents);

      // Push the batch operations into the model operations.
      operations.push(...batchOperations);
    }

    const OPERATIONS_LENGTH = operations.length;

    console.log(`action_counts.js: ${OPERATIONS_LENGTH} ${Model.collection.name} need their action counts fixed.`);

    // If fix was enabled, execute the batch writes.
    if (OPERATIONS_LENGTH > 0) {
      if (fix) {
        debug(`action_counts.js: fixing ${OPERATIONS_LENGTH} ${Model.collection.name}...`);

        while (operations.length) {
          let result = await Model.collection.bulkWrite(operations.splice(0, batch));

          debug(`action_counts.js: fixed batch of ${result.modifiedCount} ${Model.collection.name}.`);
        }

        console.log(`action_counts.js: applied all ${OPERATIONS_LENGTH} fixes to ${Model.collection.name}.`);
      } else {
        console.warn('Skipping fixing, --fix was not enabled, pass --fix to fix these errors');
      }
    }
  }
};