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query.js
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query.js
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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* Represents a queriable index. Call methods on the returned object
* to create queries.
*
* Example:
*
* let query = Index("make").eq("BMW");
*
*/
function Index(name) {
function queryMaker(op) {
return function () {
return IndexQuery(name, op, arguments);
};
}
return {
eq: queryMaker("eq"),
neq: queryMaker("neq"),
gt: queryMaker("gt"),
gteq: queryMaker("gteq"),
lt: queryMaker("lt"),
lteq: queryMaker("lteq"),
between: queryMaker("between"),
betweeq: queryMaker("betweeq"),
oneof: function oneof() {
let values = Array.slice(arguments);
let query = IndexQuery(name, "eq", [values.shift()]);
while (values.length) {
query = query.or(IndexQuery(name, "eq", [values.shift()]));
}
return query;
}
};
}
/**
* Helper that notifies a 'success' event on a request, with a given
* result object. This is typically either a cursor or a result array.
*/
function notifySuccess(request, result) {
let event = {type: "success",
target: request}; //TODO complete event interface
request.readyState = IDBRequest.DONE;
request.result = result;
if (typeof request.onsuccess == "function") {
request.onsuccess(event);
}
};
/**
* Create a cursor object.
*/
function Cursor(store, request, keys, keyOnly) {
let cursor = {
continue: function continue_() {
if (!keys.length) {
notifySuccess(request, undefined);
return;
}
let key = keys.shift();
if (keyOnly) {
cursor.key = key;
notifySuccess(request, cursor);
return;
}
let r = store.get(key);
r.onsuccess = function onsuccess() {
cursor.key = key;
cursor.value = r.result;
notifySuccess(request, cursor);
};
}
//TODO complete cursor interface
};
return cursor;
}
/**
* Create a request object.
*/
function Request() {
return {
result: undefined,
onsuccess: null,
onerror: null,
readyState: IDBRequest.LOADING
// TODO complete request interface
};
}
/**
* Create a request that will receive a cursor.
*
* This will also kick off the query, instantiate the Cursor when the
* results are available, and notify the first 'success' event.
*/
function CursorRequest(store, queryFunc, keyOnly) {
let request = Request();
queryFunc(store, function (keys) {
let cursor = Cursor(store, request, keys, keyOnly);
cursor.continue();
});
return request;
}
/**
* Create a request that will receive a result array.
*
* This will also kick off the query, build up the result array, and
* notify the 'success' event.
*/
function ResultRequest(store, queryFunc, keyOnly) {
let request = Request();
queryFunc(store, function (keys) {
if (keyOnly || !keys.length) {
notifySuccess(request, keys);
return;
}
let results = [];
function getNext() {
let r = store.get(keys.shift());
r.onsuccess = function onsuccess() {
results.push(r.result);
if (!keys.length) {
notifySuccess(request, results);
return;
}
getNext();
};
}
getNext();
});
return request;
}
/**
* Provide a generic way to create a query object from a query function.
* Depending on the implementation of that query function, the query could
* produce results from an index, combine results from other queries, etc.
*/
function Query(queryFunc, toString) {
let query = {
// Sadly we need to expose this to make Intersection and Union work :(
_queryFunc: queryFunc,
and: function and(query2) {
return Intersection(query, query2);
},
or: function or(query2) {
return Union(query, query2);
},
openCursor: function openCursor(store) {
return CursorRequest(store, queryFunc, false);
},
openKeyCursor: function openKeyCursor(store) {
return CursorRequest(store, queryFunc, true);
},
getAll: function getAll(store) {
return ResultRequest(store, queryFunc, false);
},
getAllKeys: function getAllKeys(store) {
return ResultRequest(store, queryFunc, true);
},
toString: toString
};
return query;
};
/**
* Create a query object that queries an index.
*/
function IndexQuery(indexName, operation, values) {
let negate = false;
let op = operation;
if (op == "neq") {
op = "eq";
negate = true;
}
function makeRange() {
let range;
switch (op) {
case "eq":
range = IDBKeyRange.only(values[0]);
break;
case "lt":
range = IDBKeyRange.upperBound(values[0], true);
break;
case "lteq":
range = IDBKeyRange.upperBound(values[0]);
break;
case "gt":
range = IDBKeyRange.lowerBound(values[0], true);
break;
case "gteq":
range = IDBKeyRange.lowerBound(values[0]);
range.upperOpen = true;
break;
case "between":
range = IDBKeyRange.bound(values[0], values[1], true, true);
break;
case "betweeq":
range = IDBKeyRange.bound(values[0], values[1]);
break;
}
return range;
}
function queryKeys(store, callback) {
let index = store.index(indexName);
let range = makeRange();
let request = index.getAllKeys(range);
request.onsuccess = function onsuccess(event) {
let result = request.result;
if (!negate) {
callback(result);
return;
}
// Deal with the negation case. This means we fetch all keys and then
// subtract the original result from it.
request = index.getAllKeys();
request.onsuccess = function onsuccess(event) {
let all = request.result;
callback(arraySub(all, result));
};
};
}
let args = arguments;
function toString() {
return "IndexQuery(" + Array.slice(args).toSource().slice(1, -1) + ")";
}
return Query(queryKeys, toString);
}
/**
* Create a query object that performs the intersection of two given queries.
*/
function Intersection(query1, query2) {
function queryKeys(store, callback) {
query1._queryFunc(store, function (keys1) {
query2._queryFunc(store, function (keys2) {
callback(arrayIntersect(keys1, keys2));
});
});
}
function toString() {
return "Intersection(" + query1.toString() + ", " + query2.toString() + ")";
}
return Query(queryKeys, toString);
}
/**
* Create a query object that performs the union of two given queries.
*/
function Union(query1, query2) {
function queryKeys(store, callback) {
query1._queryFunc(store, function (keys1) {
query2._queryFunc(store, function (keys2) {
callback(arrayUnion(keys1, keys2));
});
});
}
function toString() {
return "Union(" + query1.toString() + ", " + query2.toString() + ")";
}
return Query(queryKeys, toString);
}
function arraySub(minuend, subtrahend) {
if (!minuend.length || !subtrahend.length) {
return minuend;
}
return minuend.filter(function(item) {
return subtrahend.indexOf(item) == -1;
});
}
function arrayUnion(foo, bar) {
if (!foo.length) {
return bar;
}
if (!bar.length) {
return foo;
}
return foo.concat(arraySub(bar, foo));
}
function arrayIntersect(foo, bar) {
if (!foo.length) {
return foo;
}
if (!bar.length) {
return bar;
}
return foo.filter(function(item) {
return bar.indexOf(item) != -1;
});
}