import { defineTask, MemoryStorage, type TaskId, type TaskInspection } from "@earendil-works/pi-durable";
import { describe, expect, it } from "vitest";
import { chatSetup, openChat, unanswered, waitFor } from "./chat-support.ts";
import { context } from "./session-support.ts";
import { completed, deferred, eventually, openTasks } from "./task-support.ts";

type Step = { phase: "run" };

/** A one-phase task that completes once `gate` resolves; `migrate` runs when an older stored version migrates. */
function task(name: string, version: number, options: { gate?: Promise<void>; migrate?: () => void } = {}) {
	const migrate = options.migrate;
	return defineTask<null, Step, null>({
		name,
		version,
		initial: () => ({ phase: "run" }),
		phases: {
			run: async (_task, runtime, ctx) => {
				await options.gate;
				await runtime.commit(() => completed(null), ctx);
			},
		},
		abort: async () => {},
		...(migrate === undefined
			? {}
			: {
					migrate: () => {
						migrate();
						return { input: null, checkpoint: { phase: "run" as const } };
					},
				}),
	});
}

function stateOf(tasks: readonly TaskInspection[], id: TaskId): TaskInspection["state"] | undefined {
	return tasks.find((entry) => entry.record.id === id)?.state;
}

describe("Harness.inspect()", () => {
	it("derives every live task's state without running task code", async () => {
		const gate = deferred();
		const Gate = task("test.gate", 1, { gate: gate.promise });
		let gateId: TaskId | undefined;
		const Dependent = defineTask<null, { phase: "wait" } | { phase: "done" }, null>({
			name: "test.dependent",
			version: 1,
			initial: () => ({ phase: "wait" }),
			phases: {
				wait: async (_task, runtime, ctx) => {
					const checkpoint = { phase: "done" } as const;
					await runtime.commit(
						() => ({ status: "waiting", checkpoint, on: [gateId!], policy: "allSettled" }),
						ctx,
					);
				},
				done: async (_task, runtime, ctx) => runtime.commit(() => completed(null), ctx),
			},
			abort: async () => {},
		});
		let migrations = 0;
		const registered = [
			Gate,
			Dependent,
			task("test.migrating", 2, {
				migrate: () => {
					migrations++;
				},
			}),
			task("test.no-migration", 2),
			task("test.failing", 2, {
				migrate: () => {
					throw new Error("cannot migrate");
				},
			}),
			task("test.too-old", 1),
		];
		const { harness } = await openTasks(new MemoryStorage(), registered);
		const root = await harness.root(context);
		const ids = await root.commit(async (tx) => {
			gateId = await tx.createTask(Gate, null, { ownership: { kind: "conversation" } });
			return {
				gate: gateId,
				dependent: await tx.createTask(Dependent, null, { ownership: { kind: "conversation" } }),
				// Stored by definitions other than the registered ones.
				migrating: await tx.createTask(task("test.migrating", 1), null, { ownership: { kind: "conversation" } }),
				noMigration: await tx.createTask(task("test.no-migration", 1), null, {
					ownership: { kind: "conversation" },
				}),
				failing: await tx.createTask(task("test.failing", 1), null, { ownership: { kind: "conversation" } }),
				tooOld: await tx.createTask(task("test.too-old", 2), null, { ownership: { kind: "conversation" } }),
				missing: await tx.createTask(task("test.missing", 1), null, { ownership: { kind: "conversation" } }),
			};
		}, context);

		const paused = await harness.inspect(context);
		expect(paused.scheduling).toBe("paused");
		expect(paused.tasks.map((entry) => entry.record.id)).toEqual(Object.values(ids));
		expect(stateOf(paused.tasks, ids.gate)).toEqual({ kind: "ready", migrates: false });
		expect(stateOf(paused.tasks, ids.dependent)).toEqual({ kind: "ready", migrates: false });
		expect(stateOf(paused.tasks, ids.migrating)).toEqual({ kind: "ready", migrates: true });
		// A migration that was never tried is not run to find out.
		expect(stateOf(paused.tasks, ids.failing)).toEqual({ kind: "ready", migrates: true });
		expect(stateOf(paused.tasks, ids.noMigration)).toMatchObject({
			kind: "blocked",
			reason: "migration_failed",
			error: new Error("Task test.no-migration version 2 has no migration from 1"),
		});
		expect(stateOf(paused.tasks, ids.tooOld)).toEqual({ kind: "blocked", reason: "task_too_old" });
		expect(stateOf(paused.tasks, ids.missing)).toEqual({ kind: "blocked", reason: "missing_task" });
		expect(migrations).toBe(0);
		expect((await harness.inspect(context)).scheduling).toBe("paused");

		harness.resume();
		await eventually(() => migrations === 1);
		await harness.waitForTask(ids.migrating, context);
		let running = await harness.inspect(context);
		await waitFor(async () => {
			running = await harness.inspect(context);
			return (
				stateOf(running.tasks, ids.gate)?.kind === "running" &&
				stateOf(running.tasks, ids.dependent)?.kind === "waiting"
			);
		});
		expect(stateOf(running.tasks, ids.dependent)).toEqual({ kind: "waiting", on: [ids.gate] });
		expect(running.scheduling).toBe("running");
		expect(stateOf(running.tasks, ids.gate)).toEqual({ kind: "running" });
		expect(stateOf(running.tasks, ids.migrating)).toBeUndefined();
		expect(stateOf(running.tasks, ids.failing)).toEqual({
			kind: "blocked",
			reason: "migration_failed",
			error: new Error("cannot migrate"),
		});

		gate.resolve();
		await harness.waitForTask(ids.dependent, context);
		const settled = await harness.inspect(context);
		expect(settled.tasks.map((entry) => entry.record.id)).toEqual([
			ids.noMigration,
			ids.failing,
			ids.tooOld,
			ids.missing,
		]);
		await harness.close(context);
	});

	it("lists unsettled submissions", async () => {
		const setup = chatSetup();
		const busy = unanswered();
		setup.faux.setResponses([busy.step]);
		const { harness, root } = await openChat(new MemoryStorage(), setup);
		const other = await harness.createConversation({ ownership: { kind: "ownerless" } }, context);
		await other.submit({ type: "write", entry: { kind: "note" } }, context);
		const input = await root.submit({ type: "input", content: "hi" }, context);
		await busy.reached;

		const inspection = await harness.inspect(context);
		expect(inspection.submissions).toEqual([await input.status(context)]);
		expect(inspection.tasks.map((entry) => [entry.record.kind, entry.state.kind])).toEqual([
			["pi.generation", "running"],
		]);
		await harness.close(context);
	});
});