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| const fs = require('fs');
const { PocketDB } = require('./pocketdb');
const _queryItems = Symbol('queryItems');
const _findWithOptions = Symbol('findWithOptions');
const _sortByKey = Symbol('sortByKey');
const _syncCollection = Symbol('syncCollection');
class Collection {
/**
* @param {Class} db A PocketDB instance.
* @param {String} collectionName The name of the collection.
*/
constructor(db, collectionName) {
// If the `db` arg is not a PocketDB instance, then throw an error
if (!(db instanceof PocketDB)) {
throw new TypeError('DB isn\'t a valid PocketDB instance.');
}
// If the db already has a collection with the same name, then throw an error
if (db.db[collectionName]) {
throw new Error('A collection with that name already exists.');
}
this.path = db.getCollectionPath(collectionName);
this.name = collectionName;
this.events = ['beforeSave', 'afterSave', 'beforeRemove', 'afterRemove'];
this.listeners = [];
// Set the collection to the data from disk if it exists, or default collection data
this._collection = db.getCollectionData(collectionName);
// And add the collection instance to the DB
db.loadCollection(this);
this[_syncCollection]();
}
/**
* Finds all items in a collection given a query.
*
* @param {Object|Function} query A query object or .filter() function.
* @param {Object} options A options object e.g. `{ sort: 'name' }`.
* @return {Promise} A list of found objects.
*/
find(query, options) {
return Promise.resolve(this[_findWithOptions](query, options));
}
/**
* Finds the first item in a collection given a query.
*
* @param {Object|Function} query A query object or .filter() function.
* @param {Object} options A options object e.g. `{ sort: 'name' }`.
* @return {Promise} The found object.
*/
findOne(query, options) {
return Promise.resolve(this[_findWithOptions](query, options)[0]);
}
/**
* Counts the number of items in a collection given a query.
*
* @param {Object|Function} query A query object or .filter() function.
* @param {Object} options A options object e.g. `{ sort: 'name' }`.
* @return {Promise} The total count of items in a collection.
*/
count(query, options) {
return Promise.resolve(this[_findWithOptions](query, options).length);
}
/**
* Method called before all insert operations.
* It allows you to change some data before it's inserted.
*
* @param {Object|Array} data The data to do things with.
* @return {Object|Array} The data that's been changed.
*/
preInsert(data) {
return data;
}
/**
* Method called after all insert operations.
* It gives you access to the object after it was saved to the collection.
*
* @param {Object|Array} data The data to do things with.
* @return {Object|Array}
*/
postSave(data) {
return data;
}
/**
* Insert multiple items into the DB.
*
* @param {Array} items A list of items to insert.
* @return {Array} The items that were inserted.
*/
insert(items) {
if (!Array.isArray(items)) {
return Promise.reject(new Error('You must pass a valid array to `.insert()`.'));
}
const id = this._collection.nextID;
const data = items.map((item, index) => Object.assign({}, { id: id + index }, item));
// Create a list of new items by calling the preInsert hook
// with the list of items to be inserted
const newItems = this.preInsert(data);
this.emit('beforeSave', { original: items, modified: newItems });
this._collection.items = this._collection.items.concat(newItems);
this._collection.nextID = id + items.length;
this.postSave(newItems);
this.emit('afterSave', { original: items, modified: newItems });
this[_syncCollection]();
return Promise.resolve(newItems);
}
/**
* Insert a single item into the DB.
*
* @param {Object} item An item to insert.
* @return {Object} The item that was inserted.
*/
insertOne(item) {
const id = this._collection.nextID;
const data = Object.assign({}, { id }, item);
// Create a new item by calling the preInsert hook with the new data
const newItem = this.preInsert(data);
this.emit('beforeSave', { original: item, modified: newItem });
this._collection.items = this._collection.items.concat(newItem);
this._collection.nextID++;
this.postSave(newItem);
this.emit('afterSave', { original: item, modified: newItem });
this[_syncCollection]();
return Promise.resolve(newItem);
}
/**
* Method called before all update operations.
* It allows you to change some data before it's inserted.
*
* @param {Object|Array} data The data to do things with.
* @return {Object|Array} The data that's been changed.
*/
preUpdate(data) {
return data;
}
/**
* Method called after all update operations.
* It gives you access to the object after it was saved to the collection.
*
* @param {Object|Array} data The data to do things with.
* @return {Object|Array}
*/
postUpdate(data) {
return data;
}
/**
* Updates a single item into the DB.
* The update isn't merged with the existing item, meaning the
* existing item will be overwritten with exception to the `id` key.
*
* @param {Object|Function} query A query object or .filter() function.
* @param {Object} data The new data to update with.
* @return {Object} The item that was updated.
*/
updateOne(query, data) {
if (!query) {
return Promise.reject(new Error('You must specify a query to update an item.'));
}
const items = this._collection.items;
const queryResult = this[_queryItems](query, items)[0];
// If it didn't find any items to update, then reject
if (!queryResult || !queryResult.id) {
return Promise.reject(new Error('Didn\'t find any items to update.'));
}
// Construct the new item to be saved
const withPreUpdate = this.preUpdate(data);
const updatedItem = Object.assign({}, withPreUpdate, { id: queryResult.id });
this.emit('beforeSave', { original: queryResult, modified: updatedItem });
// And save it to the collection by removing the existing item and appending the update
this._collection.items = items.filter(i => i.id !== queryResult.id).concat(updatedItem);
this.postUpdate(updatedItem);
this.emit('afterSave', { original: queryResult, modified: updatedItem });
this[_syncCollection]();
return Promise.resolve(updatedItem);
}
/**
* Method called before all remove operations.
* It gives you access to the object before it gets removed from the collection.
*
* @param {Object|Array} data The data to do things with.
* @return {Object|Array}
*/
preRemove(data) {
return data;
}
/**
* Method called after all remove operations.
* It gives you access to the object after it was removed from the collection.
*
* @param {Object|Array} data The data to do things with.
* @return {Object|Array}
*/
postRemove(data) {
return data;
}
/**
* Removes a list of items that match a given query from the DB.
* If no query is provided, then all items are removed and the counter is reset.
*
* @param {Object|Function} query A query object or .filter() function.
* @return {Promise} The items that were removed.
*/
remove(query) {
const items = this._collection.items;
if (!query) {
this._collection.items = [];
this._collection.nextID = 1;
this[_syncCollection]();
return Promise.resolve(items);
}
const queryResult = this[_queryItems](query, items);
if (!queryResult || !queryResult.length) {
return Promise.reject(new Error('Didn\'t find any items to remove.'));
}
this._collection.items = items.filter(i => !queryResult.includes(i));
this[_syncCollection]();
return Promise.resolve(queryResult);
}
/**
* Removes a single item from the DB.
*
* @param {Object|Function} query A query object or .filter() function.
* @return {Object} The item that was updated.
*/
removeOne(query) {
if (!query) {
return Promise.reject(new Error('You must specify a query to remove an item.'));
}
const items = this._collection.items;
const queryResult = this[_queryItems](query, items)[0];
if (!queryResult || !queryResult.id) {
return Promise.reject(new Error('Didn\'t find any items to remove.'));
}
this.preRemove(queryResult);
this.emit('beforeRemove', { original: queryResult, modified: queryResult });
this._collection.items = items.filter(i => i.id !== queryResult.id);
this.postRemove(queryResult);
this.emit('afterRemove', { original: queryResult, modified: queryResult });
this[_syncCollection]();
return Promise.resolve(queryResult);
}
/**
* Adds a listener to the collection so other things can observe certain events.
*
* @param {String} eventName The naem of the event to listen for.
* @param {Function} listener A listener function to be called when events are emitted.
* @param {String} id A unique identifier for a listener. Used by `removeListener(id)`.
*/
addListener(eventName, listener, id) {
if (!this.events.includes(eventName)) {
throw new Error(
`${eventName} is not a valid event name. Event names are: ${this.events.join(', ')}`
);
}
if (this.listeners.find(l => (l.id === id && l.eventName === eventName))) {
throw new Error(`A listener for "${eventName}" with id "${id}" already exists.`);
}
this.listeners.push({
eventName,
listener,
id
});
}
/**
* Removes a listener from the collection.
*
* @param {String} id The ID of the listener to remove.
*/
removeListener(id) {
this.listeners = this.listeners.filter(l => l.id !== id);
}
/**
* Calls each listener function for a given event with some data.
*
* @param {String} eventName The event to listen for.
* @param {Array} args Any args that should be passed to the listener.
*/
emit(eventName, data) {
const listeners = this.listeners.filter(l => l.eventName === eventName);
for (const listener of listeners) {
listener.listener(data);
}
}
/**
* Searches a list of items for a given query and returns a copy of the result.
*
* @param {Object|Function} query A query object or .filter() function.
* @param {Array} items The list of items to search within.
* @return {Array} The results of the query.
*/
[_queryItems](query, items) {
// If the query arg is a filter function, then apply it and return the result
if (query.constructor && query.call && query.apply) {
return items.filter(query);
}
const queryKeys = Object.keys(query);
// If the query is an empty object, just return a copy of the un filtered items
if (queryKeys.length === 0) {
return [...items];
}
// Search for and return the items that match the query object
return items.filter(item => {
let matches = 0;
// Check if any of the key/values in the query match any the items key/values
for (const key of queryKeys) {
if (item[key] && item[key] === query[key]) matches++;
}
// If the item matched on all the query key/values the return it
if (queryKeys.length === matches) {
return true;
}
return false;
});
}
/**
* .sort() function that sorts items by a given key.
*
* @param {String} key The key to sort by.
* @return {Function} A function that .sort() will accept.
*/
[_sortByKey](key) {
const reverse = key.startsWith('-');
const k = reverse ? key.replace('-', '') : key;
if (reverse) {
return (a, b) => {
if (a[k] < b[k]) return 1;
if (a[k] > b[k]) return -1;
return 0;
};
}
return (a, b) => {
if (a[k] < b[k]) return -1;
if (a[k] > b[k]) return 1;
return 0;
};
}
/**
* Finds items in the collection that match a query and optionally sorts them.
*
* @param {Object|Function} query A query object or .filter() function.
* @param {Object} options A options object e.g. `{ sort: 'name' }`.
* @return {Array} The list of found items, optionally sorted.
*/
[_findWithOptions](query = {}, options = {}) {
const sortKey = options.sort ? options.sort : null;
const newItems = this[_queryItems](query, this._collection.items);
return sortKey ? newItems.sort(this[_sortByKey](sortKey)) : newItems;
}
/**
* Saves the current collection state to disk.
*/
[_syncCollection]() {
fs.writeFile(this.path, JSON.stringify(this._collection));
}
}
module.exports = {
Collection
};
|