/**
 * keeper.test.ts
 * --------------
 * Loop-level tests for `runKeeper` driven by a fake `Device`. The loop runs
 * forever in production, so the fake stops it by throwing a sentinel from
 * `sleep` once a call budget is exhausted; the test then inspects the
 * commands that were issued.
 *
 * These assert the two behaviors that matter: an idle cursor triggers a
 * synthetic sweep, and a moving cursor never does.
 */

import { describe, expect, test } from "bun:test";

import { DEFAULT_CONFIG } from "../src/config.ts";
import type { Config } from "../src/config.ts";
import type { Device, Point } from "../src/device.ts";
import { runKeeper } from "../src/keeper.ts";
import { diagonal, figureEight, type MovementStrategy } from "../src/strategies.ts";

class StopError extends Error {}

/**
 * Fake device that echoes the last commanded point (so a synthetic sweep
 * completes cleanly) and aborts the loop after `budget` sleeps.
 *
 * `positions`, when provided, is consumed one entry per `getPosition` call
 * to simulate real user movement; otherwise the cursor is reported as
 * stationary at `initial`/the last commanded point (idle).
 */
class LoopDevice implements Device {
    commanded: Point[] = [];
    sleepCount = 0;
    constructor(
        public budget: number,
        public initial: Point = { x: 100, y: 100 },
        private positions: Point[] | null = null,
    ) {}

    async getPosition(): Promise<Point> {
        if (this.positions) return this.positions.shift() ?? this.initial;
        return this.commanded.at(-1) ?? this.initial;
    }
    async setPosition(p: Point): Promise<void> {
        this.commanded.push(p);
    }
    async width(): Promise<number> {
        return 1920;
    }
    async height(): Promise<number> {
        return 1080;
    }
    async sleep(): Promise<void> {
        if (++this.sleepCount > this.budget) throw new StopError();
    }
}

const quietConfig = (overrides: Partial<Config>): Config => ({
    ...DEFAULT_CONFIG,
    verbose: false,
    ...overrides,
});

async function runUntilStop(
    config: Config,
    device: Device,
    pickRandom?: () => MovementStrategy,
): Promise<void> {
    try {
        await runKeeper(config, device, pickRandom);
    } catch (err) {
        if (!(err instanceof StopError)) throw err;
    }
}

describe("runKeeper", () => {
    test("fires a synthetic sweep once the cursor has been idle long enough", async () => {
        // moveInterval 0 => any elapsed time counts as "idle long enough",
        // so the first idle check triggers a sweep deterministically.
        const dev = new LoopDevice(50);
        await runUntilStop(quietConfig({ moveInterval: 0, pattern: "line" }), dev);
        // A sweep issued setPosition commands (the sweep is interrupted by the
        // sleep budget before it finishes, but many steps land); an idle loop
        // with no sweep would have issued none.
        expect(dev.commanded.length).toBeGreaterThanOrEqual(3);
    });

    test("does not fire while the cursor keeps moving", async () => {
        // Every poll reports a new position => always "real activity", so the
        // idleness clock keeps resetting and no sweep ever fires.
        const moving: Point[] = Array.from({ length: 40 }, (_, i) => ({ x: i, y: i }));
        const dev = new LoopDevice(20, { x: 0, y: 0 }, moving);
        await runUntilStop(quietConfig({ moveInterval: 0, pattern: "line" }), dev);
        expect(dev.commanded.length).toBe(0);
    });
});

/** Furthest x any commanded point reached — the signal that a path ramped. */
const maxX = (pts: Point[]): number => pts.reduce((m, p) => Math.max(m, p.x), -Infinity);

describe("runKeeper — loop mode", () => {
    test("loop mode ramps far from the start via the infinite loopPath", async () => {
        // `line`'s loopPath ramps x by 4px/step from the start and never
        // restores, reflecting off the screen edge. From x=100 it climbs well
        // past a single finite sweep's reach before the budget stops it.
        const dev = new LoopDevice(400, { x: 100, y: 100 });
        await runUntilStop(quietConfig({ moveInterval: 0, pattern: "line", loop: true }), dev);
        expect(maxX(dev.commanded)).toBeGreaterThan(1000);
    });

    test("single-sweep mode restores each sweep, so x never ramps away", async () => {
        // Same setup without loop: `line` runs 250 one-pixel steps then snaps
        // back to the start, so x is bounded by start + 250 no matter how many
        // sweeps fire within the budget.
        const dev = new LoopDevice(400, { x: 100, y: 100 });
        await runUntilStop(quietConfig({ moveInterval: 0, pattern: "line", loop: false }), dev);
        expect(maxX(dev.commanded)).toBeLessThanOrEqual(350);
    });

    test("loop mode chains a finite pattern across multiple cycles per trigger", async () => {
        // `figureEight` has no loopPath, so loop mode chains its 90-step path.
        // A single trigger keeps chaining cycles until the budget stops it,
        // yielding far more than the 90 commands one cycle would.
        const dev = new LoopDevice(400, { x: 800, y: 500 });
        await runUntilStop(
            quietConfig({ moveInterval: 0, pattern: "figureEight", loop: true }),
            dev,
        );
        expect(dev.commanded.length).toBeGreaterThan(180);
    });
});

describe("runKeeper — random pattern", () => {
    /**
     * A picker that always hands back `strategy` and counts how many times the
     * keeper asked. The count is the observable that pins down *when* the pick
     * happens, which is the whole contract for `random`.
     */
    function recordingPicker(strategy: MovementStrategy): {
        pick: () => MovementStrategy;
        calls: () => number;
    } {
        let calls = 0;
        return {
            pick: (): MovementStrategy => {
                calls++;
                return strategy;
            },
            calls: (): number => calls,
        };
    }

    test("asks the picker again on every trigger", async () => {
        // moveInterval 0 means each pass of the watch loop fires a sweep, so
        // the budget covers several triggers. A pattern chosen once for the
        // whole process would show exactly one call.
        const picker = recordingPicker(figureEight);
        const dev = new LoopDevice(400, { x: 800, y: 500 });
        await runUntilStop(
            quietConfig({ moveInterval: 0, pattern: "random", loop: false }),
            dev,
            picker.pick,
        );
        expect(picker.calls()).toBeGreaterThanOrEqual(2);
    });

    test("never consults the picker for a concrete pattern", async () => {
        const picker = recordingPicker(figureEight);
        const dev = new LoopDevice(400, { x: 800, y: 500 });
        await runUntilStop(
            quietConfig({ moveInterval: 0, pattern: "line", loop: false }),
            dev,
            picker.pick,
        );
        expect(picker.calls()).toBe(0);
        expect(dev.commanded.length).toBeGreaterThan(0);
    });

    test("loop mode holds a single pick for the whole loop run", async () => {
        // One trigger, many chained cycles: the pattern must not change under
        // the user mid-run, so the picker is asked exactly once.
        const picker = recordingPicker(figureEight);
        const dev = new LoopDevice(400, { x: 800, y: 500 });
        await runUntilStop(
            quietConfig({ moveInterval: 0, pattern: "random", loop: true }),
            dev,
            picker.pick,
        );
        expect(picker.calls()).toBe(1);
        // ...and those cycles really did run, so the single call isn't just
        // the loop never getting started.
        expect(dev.commanded.length).toBeGreaterThan(180);
    });

    test("a picked strategy keeps its own loopPath behavior", async () => {
        // The picker returns real registry entries, so a pick with an infinite
        // loopPath (`diagonal`) drives that path rather than a chained finite
        // one — the same as selecting it explicitly. Mirrors the `line` loop
        // test above: x ramps far past a single finite sweep's 250px reach.
        const picker = recordingPicker(diagonal);
        const dev = new LoopDevice(400, { x: 100, y: 100 });
        await runUntilStop(
            quietConfig({ moveInterval: 0, pattern: "random", loop: true }),
            dev,
            picker.pick,
        );
        expect(maxX(dev.commanded)).toBeGreaterThan(1000);
    });
});