import { describe, it, expect } from 'vitest';
import { advancePlaybackIndex } from '../lib/telemetry-track';
import type { TelemetryPoint } from '../lib/telemetry-export';

const BASE = Date.parse('2026-09-28T14:30:00.000Z');

// Minimal TelemetryPoint builder — advancePlaybackIndex only reads timestamp + segmentId.
function mk(offsetMs: number, segmentId = 0): TelemetryPoint {
  return {
    timestamp: new Date(BASE + offsetMs).toISOString(),
    latitude: 40,
    longitude: -74,
    altitude: 0,
    speed: 0,
    heading: 0,
    gpsAccuracy: 0,
    leanAngle: 0,
    pitchAngle: 0,
    accelX: 0,
    accelY: 0,
    accelZ: 0,
    longitudinalG: 0,
    lateralG: 0,
    segmentId,
  };
}

describe('advancePlaybackIndex (replay playback synchronization)', () => {
  const uniform = Array.from({ length: 10 }, (_, i) => mk(i * 50)); // 20 Hz, 50 ms apart

  it('advances in step with real recorded time (1x)', () => {
    // 200 ms of budget over 50 ms samples = 4 steps.
    const r = advancePlaybackIndex(uniform, 0, 200);
    expect(r.index).toBe(4);
    expect(r.remainingMs).toBe(0);
  });

  it('carries leftover budget when it does not cover a full step', () => {
    // 120 ms consumes two 50 ms steps (100 ms), leaving 20 ms.
    const r = advancePlaybackIndex(uniform, 0, 120);
    expect(r.index).toBe(2);
    expect(r.remainingMs).toBe(20);
  });

  it('does not advance when the budget is below one step', () => {
    const r = advancePlaybackIndex(uniform, 3, 10);
    expect(r.index).toBe(3);
    expect(r.remainingMs).toBe(10);
  });

  it('compresses a multi-second gap to a single 50 ms step so playback never stalls', () => {
    // Samples 0..2 uniform; sample 3 is 10 s later (disconnected). A 60 ms budget from
    // index 2 must still cross the gap (treated as a 50 ms step), not wait 10 s.
    const gapped = [mk(0), mk(50), mk(100), mk(10_100)];
    const r = advancePlaybackIndex(gapped, 2, 60);
    expect(r.index).toBe(3);
    expect(r.remainingMs).toBe(0); // reached the end
  });

  it('clamps at the final index with no remaining budget', () => {
    const r = advancePlaybackIndex(uniform, 8, 100_000);
    expect(r.index).toBe(9);
    expect(r.remainingMs).toBe(0);
  });

  it('is a no-op on empty input', () => {
    expect(advancePlaybackIndex([], 0, 1000)).toEqual({ index: 0, remainingMs: 0 });
  });
});