import { setupTest, startEngine, startClientInTmux, openCmdFifo, writeFifoCommand, wait, tmuxSendKeys, waitForPaneText, teardownTest } from './test_utils';

export async function testKeyPressLatency(): Promise<void> {
  console.log("\nTest: KEY PRESS LATENCY (50 toggles, check for exponential slowdown)");
  setupTest();
  const engine = await startEngine();
  await startClientInTmux();
  openCmdFifo();
  await wait(500);

  const ITERATIONS = 50;
  const LATENCY_WARN = 500;   // warn if >500ms
  const LATENCY_FAIL = 5000;  // fail if >5s

  let latencies: number[] = [];
  let prevState = "IDLE";

  for (let i = 0; i < ITERATIONS; i++) {
    // Determine which state we expect after toggle
    const expectNext = (prevState === "IDLE") ? "R" : "L";
    const startTime = Date.now();
    tmuxSendKeys("looper", "0", "t");
    const pane = await waitForPaneText(expectNext, 10000);
    const elapsed = Date.now() - startTime;
    latencies.push(elapsed);

    // Log periodic summary
    if (i % 10 === 9) {
      const avg = latencies.slice(i-9, i+1).reduce((a,b)=>a+b,0) / 10;
      console.log(`  Iteration ${i+1}: avg last 10 = ${avg.toFixed(0)} ms, last = ${elapsed} ms`);
    }

    if (elapsed > LATENCY_FAIL) {
      console.log(`  FAIL: Iteration ${i+1} latency ${elapsed} ms exceeds ${LATENCY_FAIL} ms`);
      engine.kill(); teardownTest();
      throw new Error(`Latency exceeded fail threshold at iteration ${i+1}`);
    }

    if (elapsed > LATENCY_WARN) {
      console.log(`  WARN: Iteration ${i+1} latency ${elapsed} ms > ${LATENCY_WARN} ms (possible slowdown)`);
    }

    // Toggle state for next expectation
    prevState = (prevState === "IDLE") ? "LOOPING" : "IDLE";
    await wait(200);  // brief cooldown
  }

  // Check for trend: if last 10 avg > 3x first 10 avg → exponential
  const first10Avg = latencies.slice(0,10).reduce((a,b)=>a+b,0) / 10;
  const last10Avg  = latencies.slice(-10).reduce((a,b)=>a+b,0) / 10;
  console.log(`  First 10 avg: ${first10Avg.toFixed(0)} ms, Last 10 avg: ${last10Avg.toFixed(0)} ms`);

  if (last10Avg > 3 * first10Avg && last10Avg > 500) {
    console.log(`  FAIL: Latency grew from ${first10Avg.toFixed(0)} ms to ${last10Avg.toFixed(0)} ms (exponential pattern)`);
    engine.kill(); teardownTest();
    throw new Error("Exponential latency increase");
  }

  console.log("  PASS: No exponential latency growth");
  engine.kill();
  teardownTest();
}