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authorFlorian Dold <florian.dold@gmail.com>2017-03-24 16:20:31 +0100
committerFlorian Dold <florian.dold@gmail.com>2017-03-24 16:20:31 +0100
commit970230da068570385a03483dec0559049f3ac458 (patch)
treeafb204951b3edb6c80facc975600e42d6a25a58e /src
parentf721c1ee827ed61136922e5ccf112d9007c5bfac (diff)
Add support for conditionals in DB queries
Diffstat (limited to 'src')
-rw-r--r--src/query.ts82
1 files changed, 82 insertions, 0 deletions
diff --git a/src/query.ts b/src/query.ts
index 30633b0af..89d4133b3 100644
--- a/src/query.ts
+++ b/src/query.ts
@@ -76,10 +76,87 @@ export interface QueryStream<T> {
map<S>(f: (x:T) => S): QueryStream<S>;
flatMap<S>(f: (x: T) => S[]): QueryStream<S>;
toArray(): Promise<T[]>;
+ first(): QueryValue<T>;
then(onfulfill: any, onreject: any): any;
}
+
+/**
+ * Query result that consists of at most one value.
+ */
+export interface QueryValue<T> {
+ map<S>(f: (x: T) => S): QueryValue<S>;
+ cond<R>(f: (x: T) => boolean, onTrue: (r: QueryRoot) => R, onFalse: (r: QueryRoot) => R): Promise<void>;
+}
+
+
+abstract class BaseQueryValue<T> implements QueryValue<T> {
+ root: QueryRoot;
+
+ constructor(root: QueryRoot) {
+ this.root = root;
+ }
+
+ map<S>(f: (x: T) => S): QueryValue<S> {
+ return new MapQueryValue<T,S>(this, f);
+ }
+
+ cond<R>(f: (x: T) => boolean, onTrue: (r: QueryRoot) => R, onFalse: (r: QueryRoot) => R): Promise<void> {
+ return new Promise((resolve, reject) => {
+ this.subscribeOne((v, tx) => {
+ if (f(v)) {
+ onTrue(this.root);
+ } else {
+ onFalse(this.root);
+ }
+ });
+ resolve();
+ });
+ }
+
+ abstract subscribeOne(f: SubscribeOneFn): void;
+}
+
+class FirstQueryValue<T> extends BaseQueryValue<T> {
+ gotValue = false;
+ s: QueryStreamBase<T>;
+ constructor(stream: QueryStreamBase<T>) {
+ super(stream.root);
+ this.s = stream;
+ }
+
+ subscribeOne(f: SubscribeOneFn): void {
+ this.s.subscribe((isDone, value, tx) => {
+ if (this.gotValue) {
+ return;
+ }
+ if (isDone) {
+ f(undefined, tx);
+ } else {
+ f(value, tx);
+ }
+ this.gotValue = true;
+ });
+ }
+}
+
+class MapQueryValue<T,S> extends BaseQueryValue<S> {
+ mapFn: (x: T) => S;
+ v: BaseQueryValue<T>;
+
+ constructor(v: BaseQueryValue<T>, mapFn: (x: T) => S) {
+ super(v.root);
+ this.v = v;
+ this.mapFn = mapFn;
+ }
+
+ subscribeOne(f: SubscribeOneFn): void {
+ this.v.subscribeOne((v, tx) => this.mapFn(v));
+ }
+}
+
+
export let AbortTransaction = Symbol("abort_transaction");
/**
@@ -112,6 +189,10 @@ abstract class QueryStreamBase<T> implements QueryStream<T>, PromiseLike<void> {
this.root = root;
}
+ first(): QueryValue<T> {
+ return new FirstQueryValue(this);
+ }
+
then<R>(onfulfilled: (value: void) => R | PromiseLike<R>, onrejected: (reason: any) => R | PromiseLike<R>): PromiseLike<R> {
return this.root.then(onfulfilled, onrejected);
}
@@ -183,6 +264,7 @@ abstract class QueryStreamBase<T> implements QueryStream<T>, PromiseLike<void> {
type FilterFn = (e: any) => boolean;
type SubscribeFn = (done: boolean, value: any, tx: IDBTransaction) => void;
+type SubscribeOneFn = (value: any, tx: IDBTransaction) => void;
interface FlatMapFn<T> {
(v: T): T[];