mirror of
https://github.com/badlogic/pi-mono.git
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src/next is src (the main export), src/next-node is src/node with short subpaths (/http, /workers, /plugins, /plugins/runtime, /app, /surfaces, /web, /react, /tui, /tui/launcher); the foundations get /json and /watch; Chord v1 moves to src/old (/old, /old/node) until p2 runs on v2; tests and docs move likewise (test/, docs/, test/old, docs/old). Durable and env import the foundations from their subpaths.
66 lines
2.7 KiB
TypeScript
66 lines
2.7 KiB
TypeScript
// Derives: values computed from documents and from other objects' members, recomputed only when needed.
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// Run from packages/chord:
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// node --conditions=source --experimental-strip-types test/examples/03-derives.ts
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import { BACKGROUND_CONTEXT } from "../../src/context/index.ts";
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import { arr, int, local, method, obj, str } from "../../src/contracts/index.ts";
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import { defineState } from "../../src/documents/index.ts";
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import { createHost, defineFacet } from "../../src/host/index.ts";
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import { mapShared } from "../../src/state/index.ts";
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const context = BACKGROUND_CONTEXT;
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const NotesDoc = defineState("notes", {
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schema: obj({ list: arr(obj({ text: str() })) }),
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version: 1,
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initial: () => ({ list: [] }),
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});
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const Notes = local("example.notes", {
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version: 1,
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params: {},
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members: { titles: arr(str()), count: int(), add: method(obj({ text: str() })) },
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});
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const Badge = local("example.badge", { version: 1, params: { user: str() }, members: { label: str() } });
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const facet = defineFacet((host) => {
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host.serve(Notes, (_, self) => {
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const notes = self.state(NotesDoc);
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// mapShared calls its function once per note object: unchanged notes keep the same title, so the derive's
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// diff after an append is one insert, not a comparison of every title.
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const title = mapShared((note: { text: string }) => {
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console.log(" title computed for:", note.text);
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return note.text.slice(0, 12);
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});
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return {
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// A derive declares its sources; its compute is synchronous and pure.
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titles: self.derive([notes], ([n]) => title(n.list)),
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count: self.derive([notes], ([n]) => n.list.length),
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add: async ({ text }, ctx) => {
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await notes.change((draft) => {
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draft.list.push({ text });
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}, ctx);
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return null;
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},
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};
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});
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// A derive over another object's member, through a reference declared with self.get.
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host.serve(Badge, ({ user }, self) => {
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const notes = self.get(Notes, {});
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return { label: self.derive([notes.count], ([count]) => `${user}: ${count} notes`) };
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});
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});
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const host = createHost({ onError: (error) => console.error("background error:", error) });
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await host.load([{ name: "@example/notes", facet }], context);
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const notes = await host.get(Notes, {}, context);
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const badge = await host.get(Badge, { user: "mario" }, context);
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await notes.add({ text: "buy milk and bread" }, context);
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await notes.add({ text: "call Anna" }, context);
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// Nobody watches `titles`, so the commits only marked it; reading computes it, each title once.
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console.log("titles:", notes.titles.value);
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await notes.add({ text: "water plants" }, context);
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console.log("titles:", notes.titles.value);
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console.log("badge:", badge.label.value);
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await host.close(context);
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