feat(tasks): create pipes passed functions and checks for cancellation

src/definitions/tasks.ts

@@ -1,4 +1,4 @@
-import { Empty, Members, UnaryFn } from 'type-core';
+import { Members } from 'type-core';
 import { Writable, Readable } from 'stream';
 
 /**
@@ -13,7 +13,6 @@ export declare namespace Task {
   export interface Record {
     [key: string]: Task | Record;
   }
-  export type Create = UnaryFn<Context, Task | Empty | Promise<Task | Empty>>;
 }
 
 /**

src/tasks/creation/create.ts

@@ -1,15 +1,177 @@
-import { Task, Context } from '../../definitions';
+import { Empty, MaybePromise, UnaryFn } from 'type-core';
+import { Context, Task } from '../../definitions';
+import { isCancelled } from '../../utils/is-cancelled';
 import { run } from '../../utils/run';
 
 /**
- * Takes an optionally *Task* returning function
- * and turns the function itself and the returned
- * *Task* into a single sequential *Task*.
+ * A task creation pipe of unary functions.
+ * All functions will compose the task itself,
+ * with a check for cancellation before running each.
+ * The first function takes `Context` as an argument.
+ * The last function can optionally return a `Task`,
+ * which will also be run.
  * @returns Task
  */
-export function create(fn: Task.Create): Task.Async {
+export const create = pipe as Create;
+
+function pipe(...fns: Array<UnaryFn<any, MaybePromise<any>>>): Task.Async {
   return async (ctx: Context): Promise<void> => {
-    const task = await fn(ctx);
-    if (task) await run(task, ctx);
+    let value: any = ctx;
+    for (const fn of fns) {
+      if (await isCancelled(ctx)) break;
+      value = await fn(value);
+    }
+    if (value) await run(value, ctx);
   };
 }
+
+export interface Create {
+  (f1: UnaryFn<Context, MaybePromise<Task | Empty>>): Task.Async;
+  <T1>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7, T8>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<T8>>,
+    f9: UnaryFn<T8, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7, T8, T9>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<T8>>,
+    f9: UnaryFn<T8, MaybePromise<T9>>,
+    f10: UnaryFn<T9, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<T8>>,
+    f9: UnaryFn<T8, MaybePromise<T9>>,
+    f10: UnaryFn<T9, MaybePromise<T10>>,
+    f11: UnaryFn<T10, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<T8>>,
+    f9: UnaryFn<T8, MaybePromise<T9>>,
+    f10: UnaryFn<T9, MaybePromise<T10>>,
+    f11: UnaryFn<T10, MaybePromise<T11>>,
+    f12: UnaryFn<T11, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<T8>>,
+    f9: UnaryFn<T8, MaybePromise<T9>>,
+    f10: UnaryFn<T9, MaybePromise<T10>>,
+    f11: UnaryFn<T10, MaybePromise<T11>>,
+    f12: UnaryFn<T11, MaybePromise<T12>>,
+    f13: UnaryFn<T12, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<T8>>,
+    f9: UnaryFn<T8, MaybePromise<T9>>,
+    f10: UnaryFn<T9, MaybePromise<T10>>,
+    f11: UnaryFn<T10, MaybePromise<T11>>,
+    f12: UnaryFn<T11, MaybePromise<T12>>,
+    f13: UnaryFn<T12, MaybePromise<T13>>,
+    f14: UnaryFn<T13, MaybePromise<Task | Empty>>
+  ): Task.Async;
+  <T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(
+    f1: UnaryFn<Context, MaybePromise<T1>>,
+    f2: UnaryFn<T1, MaybePromise<T2>>,
+    f3: UnaryFn<T2, MaybePromise<T3>>,
+    f4: UnaryFn<T3, MaybePromise<T4>>,
+    f5: UnaryFn<T4, MaybePromise<T5>>,
+    f6: UnaryFn<T5, MaybePromise<T6>>,
+    f7: UnaryFn<T6, MaybePromise<T7>>,
+    f8: UnaryFn<T7, MaybePromise<T8>>,
+    f9: UnaryFn<T8, MaybePromise<T9>>,
+    f10: UnaryFn<T9, MaybePromise<T10>>,
+    f11: UnaryFn<T10, MaybePromise<T11>>,
+    f12: UnaryFn<T11, MaybePromise<T12>>,
+    f13: UnaryFn<T12, MaybePromise<T13>>,
+    f14: UnaryFn<T13, MaybePromise<T14>>,
+    f15: UnaryFn<T14, MaybePromise<Task | Empty>>
+  ): Task.Async;
+}