Source: IndexHashMap.js

"use strict";

var Shared = require('./Shared'),
	Path = require('./Path');

/**
 * The index class used to instantiate hash map indexes that the database can
 * use to speed up queries on collections and views.
 * @constructor
 */
var IndexHashMap = function () {
	this.init.apply(this, arguments);
};

IndexHashMap.prototype.init = function (keys, options, collection) {
	this._crossRef = {};
	this._size = 0;
	this._id = this._itemKeyHash(keys, keys);

	this.data({});
	this.unique(options && options.unique ? options.unique : false);

	if (keys !== undefined) {
		this.keys(keys);
	}

	if (collection !== undefined) {
		this.collection(collection);
	}

	this.name(options && options.name ? options.name : this._id);
};

Shared.addModule('IndexHashMap', IndexHashMap);
Shared.mixin(IndexHashMap.prototype, 'Mixin.ChainReactor');

IndexHashMap.prototype.id = function () {
	return this._id;
};

IndexHashMap.prototype.state = function () {
	return this._state;
};

IndexHashMap.prototype.size = function () {
	return this._size;
};

Shared.synthesize(IndexHashMap.prototype, 'data');
Shared.synthesize(IndexHashMap.prototype, 'name');
Shared.synthesize(IndexHashMap.prototype, 'collection');
Shared.synthesize(IndexHashMap.prototype, 'type');
Shared.synthesize(IndexHashMap.prototype, 'unique');

IndexHashMap.prototype.keys = function (val) {
	if (val !== undefined) {
		this._keys = val;

		// Count the keys
		this._keyCount = (new Path()).parse(this._keys).length;
		return this;
	}

	return this._keys;
};

IndexHashMap.prototype.rebuild = function () {
	// Do we have a collection?
	if (this._collection) {
		// Get sorted data
		var collection = this._collection.subset({}, {
				$decouple: false,
				$orderBy: this._keys
			}),
			collectionData = collection.find(),
			dataIndex,
			dataCount = collectionData.length;

		// Clear the index data for the index
		this._data = {};

		if (this._unique) {
			this._uniqueLookup = {};
		}

		// Loop the collection data
		for (dataIndex = 0; dataIndex < dataCount; dataIndex++) {
			this.insert(collectionData[dataIndex]);
		}
	}

	this._state = {
		name: this._name,
		keys: this._keys,
		indexSize: this._size,
		built: new Date(),
		updated: new Date(),
		ok: true
	};
};

IndexHashMap.prototype.insert = function (dataItem, options) {
	var uniqueFlag = this._unique,
		uniqueHash,
		itemHashArr,
		hashIndex;

	if (uniqueFlag) {
		uniqueHash = this._itemHash(dataItem, this._keys);
		this._uniqueLookup[uniqueHash] = dataItem;
	}

	// Generate item hash
	itemHashArr = this._itemHashArr(dataItem, this._keys);

	// Get the path search results and store them
	for (hashIndex = 0; hashIndex < itemHashArr.length; hashIndex++) {
		this.pushToPathValue(itemHashArr[hashIndex], dataItem);
	}
};

IndexHashMap.prototype.update = function (dataItem, options) {
	// TODO: Write updates to work
	// 1: Get uniqueHash for the dataItem primary key value (may need to generate a store for this)
	// 2: Remove the uniqueHash as it currently stands
	// 3: Generate a new uniqueHash for dataItem
	// 4: Insert the new uniqueHash
};

IndexHashMap.prototype.remove = function (dataItem, options) {
	var uniqueFlag = this._unique,
		uniqueHash,
		itemHashArr,
		hashIndex;

	if (uniqueFlag) {
		uniqueHash = this._itemHash(dataItem, this._keys);
		delete this._uniqueLookup[uniqueHash];
	}

	// Generate item hash
	itemHashArr = this._itemHashArr(dataItem, this._keys);

	// Get the path search results and store them
	for (hashIndex = 0; hashIndex < itemHashArr.length; hashIndex++) {
		this.pullFromPathValue(itemHashArr[hashIndex], dataItem);
	}
};

IndexHashMap.prototype.violation = function (dataItem) {
	// Generate item hash
	var uniqueHash = this._itemHash(dataItem, this._keys);

	// Check if the item breaks the unique constraint
	return Boolean(this._uniqueLookup[uniqueHash]);
};

IndexHashMap.prototype.hashViolation = function (uniqueHash) {
	// Check if the item breaks the unique constraint
	return Boolean(this._uniqueLookup[uniqueHash]);
};

IndexHashMap.prototype.pushToPathValue = function (hash, obj) {
	var pathValArr = this._data[hash] = this._data[hash] || [];

	// Make sure we have not already indexed this object at this path/value
	if (pathValArr.indexOf(obj) === -1) {
		// Index the object
		pathValArr.push(obj);

		// Record the reference to this object in our index size
		this._size++;

		// Cross-reference this association for later lookup
		this.pushToCrossRef(obj, pathValArr);
	}
};

IndexHashMap.prototype.pullFromPathValue = function (hash, obj) {
	var pathValArr = this._data[hash],
		indexOfObject;

	// Make sure we have already indexed this object at this path/value
	indexOfObject = pathValArr.indexOf(obj);

	if (indexOfObject > -1) {
		// Un-index the object
		pathValArr.splice(indexOfObject, 1);

		// Record the reference to this object in our index size
		this._size--;

		// Remove object cross-reference
		this.pullFromCrossRef(obj, pathValArr);
	}

	// Check if we should remove the path value array
	if (!pathValArr.length) {
		// Remove the array
		delete this._data[hash];
	}
};

IndexHashMap.prototype.pull = function (obj) {
	// Get all places the object has been used and remove them
	var id = obj[this._collection.primaryKey()],
		crossRefArr = this._crossRef[id],
		arrIndex,
		arrCount = crossRefArr.length,
		arrItem;

	for (arrIndex = 0; arrIndex < arrCount; arrIndex++) {
		arrItem = crossRefArr[arrIndex];

		// Remove item from this index lookup array
		this._pullFromArray(arrItem, obj);
	}

	// Record the reference to this object in our index size
	this._size--;

	// Now remove the cross-reference entry for this object
	delete this._crossRef[id];
};

IndexHashMap.prototype._pullFromArray = function (arr, obj) {
	var arrCount = arr.length;

	while (arrCount--) {
		if (arr[arrCount] === obj) {
			arr.splice(arrCount, 1);
		}
	}
};

IndexHashMap.prototype.pushToCrossRef = function (obj, pathValArr) {
	var id = obj[this._collection.primaryKey()],
		crObj;

	this._crossRef[id] = this._crossRef[id] || [];

	// Check if the cross-reference to the pathVal array already exists
	crObj = this._crossRef[id];

	if (crObj.indexOf(pathValArr) === -1) {
		// Add the cross-reference
		crObj.push(pathValArr);
	}
};

IndexHashMap.prototype.pullFromCrossRef = function (obj, pathValArr) {
	var id = obj[this._collection.primaryKey()];

	delete this._crossRef[id];
};

IndexHashMap.prototype.lookup = function (query) {
	return this._data[this._itemHash(query, this._keys)] || [];
};

IndexHashMap.prototype.match = function (query, options) {
	// Check if the passed query has data in the keys our index
	// operates on and if so, is the query sort matching our order
	var pathSolver = new Path();
	var indexKeyArr = pathSolver.parseArr(this._keys),
		queryArr = pathSolver.parseArr(query),
		matchedKeys = [],
		matchedKeyCount = 0,
		i;

	// Loop the query array and check the order of keys against the
	// index key array to see if this index can be used
	for (i = 0; i < indexKeyArr.length; i++) {
		if (queryArr[i] === indexKeyArr[i]) {
			matchedKeyCount++;
			matchedKeys.push(queryArr[i]);
		} else {
			// Query match failed - this is a hash map index so partial key match won't work
			return {
				matchedKeys: [],
				totalKeyCount: queryArr.length,
				score: 0
			};
		}
	}

	return {
		matchedKeys: matchedKeys,
		totalKeyCount: queryArr.length,
		score: matchedKeyCount
	};

	//return pathSolver.countObjectPaths(this._keys, query);
};

IndexHashMap.prototype._itemHash = function (item, keys) {
	var path = new Path(),
		pathData,
		hash = '',
		k;

	pathData = path.parse(keys);

	for (k = 0; k < pathData.length; k++) {
		if (hash) { hash += '_'; }
		hash += path.value(item, pathData[k].path).join(':');
	}

	return hash;
};

IndexHashMap.prototype._itemKeyHash = function (item, keys) {
	var path = new Path(),
		pathData,
		hash = '',
		k;

	pathData = path.parse(keys);

	for (k = 0; k < pathData.length; k++) {
		if (hash) { hash += '_'; }
		hash += path.keyValue(item, pathData[k].path);
	}

	return hash;
};

IndexHashMap.prototype._itemHashArr = function (item, keys) {
	var path = new Path(),
		pathData,
		//hash = '',
		hashArr = [],
		valArr,
		i, k, j;

	pathData = path.parse(keys);

	for (k = 0; k < pathData.length; k++) {
		valArr = path.value(item, pathData[k].path);

		for (i = 0; i < valArr.length; i++) {
			if (k === 0) {
				// Setup the initial hash array
				hashArr.push(valArr[i]);
			} else {
				// Loop the hash array and concat the value to it
				for (j = 0; j < hashArr.length; j++) {
					hashArr[j] = hashArr[j] + '_' + valArr[i];
				}
			}
		}
	}

	return hashArr;
};

Shared.finishModule('IndexHashMap');
module.exports = IndexHashMap;