package app

import (
	"encoding/json"
	"os"
	"path/filepath"
	"testing"
	"time"
)

func TestMetricsTrackerDisabledByEmptyDir(t *testing.T) {
	m, err := newMetricsTracker("")
	if err != nil {
		t.Fatalf("newMetricsTracker(\"\") err: %v", err)
	}
	if m != nil {
		t.Fatalf("expected nil tracker for empty dir, got %v", m)
	}
}

func TestMetricsTrackerRecordsAndWrites(t *testing.T) {
	dir := t.TempDir()
	m, err := newMetricsTracker(dir)
	if err != nil {
		t.Fatalf("newMetricsTracker: %v", err)
	}
	if m == nil {
		t.Fatal("expected non-nil tracker")
	}

	m.recordPTYOut(2*time.Millisecond, 1024)
	m.recordPTYOut(5*time.Millisecond, 4096)
	m.recordRender(800 * time.Microsecond)
	m.recordStdout(300*time.Microsecond, 1100)
	m.recordEmuWrite(150 * time.Microsecond)
	m.recordEmuTitle(0, true)
	m.recordEmuTitle(20*time.Microsecond, false)
	m.recordSidebar(100*time.Microsecond, true)
	m.recordSidebar(900*time.Microsecond, false)
	m.recordTabbar(50*time.Microsecond, true)
	m.recordStatus(40*time.Microsecond, true)
	m.recordSnapshot(2 * time.Millisecond)
	m.recordTickerFire(false)
	m.recordTickerFire(true)
	m.recordPTYOutDrop()

	m.close()

	// metrics.json should exist and parse, and reflect what we recorded.
	raw, err := os.ReadFile(filepath.Join(dir, "metrics.json"))
	if err != nil {
		t.Fatalf("read metrics.json: %v", err)
	}
	var snap metricsSnapshot
	if err := json.Unmarshal(raw, &snap); err != nil {
		t.Fatalf("parse metrics.json: %v", err)
	}
	if snap.PTYChunks != 2 {
		t.Errorf("PTYChunks = %d, want 2", snap.PTYChunks)
	}
	if snap.PTYBytes != 5120 {
		t.Errorf("PTYBytes = %d, want 5120", snap.PTYBytes)
	}
	if snap.OnPTYOutMaxNs != (5 * time.Millisecond).Nanoseconds() {
		t.Errorf("OnPTYOutMaxNs = %d, want %d",
			snap.OnPTYOutMaxNs, (5 * time.Millisecond).Nanoseconds())
	}
	if snap.SidebarDraws != 2 {
		t.Errorf("SidebarDraws = %d, want 2", snap.SidebarDraws)
	}
	if snap.SidebarCacheHits != 1 {
		t.Errorf("SidebarCacheHits = %d, want 1", snap.SidebarCacheHits)
	}
	if snap.SidebarCacheHitRate != 0.5 {
		t.Errorf("SidebarCacheHitRate = %v, want 0.5", snap.SidebarCacheHitRate)
	}
	if snap.EmuTitleCalls != 1 || snap.EmuTitleSkips != 1 {
		t.Errorf("emu title accounting: calls=%d skips=%d, want 1/1",
			snap.EmuTitleCalls, snap.EmuTitleSkips)
	}
	if snap.TickerFires != 2 || snap.TickerIdleFires != 1 {
		t.Errorf("ticker accounting: fires=%d idle=%d, want 2/1",
			snap.TickerFires, snap.TickerIdleFires)
	}
	if snap.OnPTYOutDrops != 1 {
		t.Errorf("OnPTYOutDrops = %d, want 1", snap.OnPTYOutDrops)
	}

	// summary.txt should also be present and non-empty.
	info, err := os.Stat(filepath.Join(dir, "summary.txt"))
	if err != nil {
		t.Fatalf("stat summary.txt: %v", err)
	}
	if info.Size() == 0 {
		t.Fatal("summary.txt is empty")
	}
}

func TestMetricsTrackerNilSafe(t *testing.T) {
	// Every record* method must be safe to call on a nil receiver
	// because the hot paths use that to avoid an enabled-check.
	var m *metricsTracker
	m.recordPTYOut(time.Millisecond, 100)
	m.recordPTYOutDrop()
	m.recordRender(time.Microsecond)
	m.recordStdout(time.Microsecond, 50)
	m.recordEmuWrite(time.Microsecond)
	m.recordEmuTitle(time.Microsecond, false)
	m.recordEmuTitle(0, true)
	m.recordSidebar(time.Microsecond, true)
	m.recordTabbar(time.Microsecond, false)
	m.recordStatus(time.Microsecond, true)
	m.recordSnapshot(time.Microsecond)
	m.recordTickerFire(true)
	m.close()
}