package e2e_test

import (
	"strings"
	"testing"
	"time"

	"pad/internal/editor"
	"pad/internal/test/e2e"
	"pad/internal/ui"
)

// TestNoFramesWhileIdle is the pre-release frame-regression guard. Frame
// emission is event-driven (architecture.md §2): once the logic goroutine
// has settled — every async result applied, every wrap-settle pass done —
// it must emit ZERO further frames while no input arrives. A non-zero
// delta means something is spinning (a ticker, a re-emission loop, a
// feedback ping-pong between layout and state) and would burn CPU and
// battery on a real device for the app's entire idle lifetime.
//
// The main-loop side (Gio presents) is measured by the same contract's
// on-device instrument: PERF-PRESENT logcat lines (cmd/pad, enabled by
// touching <sd>/PadPerf/enable; see scripts/profile_emulator.sh).

// waitFrameSettle returns the frame count once it has been unchanged for
// quietFor (the logic is quiescent). Fatals if it never settles.
func waitFrameSettle(t *testing.T, h *e2e.Harness, quietFor time.Duration) int {
	t.Helper()
	deadline := time.Now().Add(10 * time.Second)
	last := h.FrameCount()
	lastChanged := time.Now()
	for time.Now().Before(deadline) {
		time.Sleep(50 * time.Millisecond)
		if n := h.FrameCount(); n != last {
			last, lastChanged = n, time.Now()
			continue
		}
		if time.Since(lastChanged) >= quietFor {
			return last
		}
	}
	t.Fatal("frame count never settled within 10s")
	return 0
}

// assertIdleFrames requires the frame count to be unchanged across an
// idleFor window that follows a settled (quietFor-stable) state.
func assertIdleFrames(t *testing.T, h *e2e.Harness, quietFor, idleFor time.Duration, phase string) {
	t.Helper()
	before := waitFrameSettle(t, h, quietFor)
	time.Sleep(idleFor)
	if after := h.FrameCount(); after != before {
		t.Fatalf("%s: logic emitted %d frame(s) while idle (before=%d after=%d); emission must be event-driven",
			phase, after-before, before, after)
	}
}

// TestNoFramesWhileIdle_Browser: the file-browser page, fully loaded, must
// go completely quiet.
func TestNoFramesWhileIdle_Browser(t *testing.T) {
	h := e2e.NewHarness()
	h.Run()
	defer h.Cleanup()
	h.SendConfig(1080, 2400)
	if _, err := h.WaitForFrameCount(1, 5*time.Second); err != nil {
		t.Fatalf("no frames: %v", err)
	}
	assertIdleFrames(t, h, 300*time.Millisecond, time.Second, "browser")
}

// TestNoFramesWhileIdle_Editor: an open file after a load, a scroll, and a
// full find cycle (scan + navigate + close) must go completely quiet —
// the find settle machinery in particular must terminate, not re-trigger.
func TestNoFramesWhileIdle_Editor(t *testing.T) {
	// 300 long lines: enough to scroll and to match a query at several
	// positions.
	var sb strings.Builder
	for i := 0; i < 300; i++ {
		sb.WriteString("line number 000: the quick brown fox jumps over the lazy dog by the river\n")
	}
	h, _ := realFileHarness(t, "idle.txt", sb.String())
	defer h.Cleanup()
	h.SendConfig(1080, 2400)

	// Scroll (HandleScroll swallows input for 300ms after open).
	time.Sleep(400 * time.Millisecond)
	h.SendInput([]ui.InputEvent{{Handler: editor.HandleScroll, Data: 2000}})

	// A full find cycle: open the bar, query, navigate, close.
	h.SendInput([]ui.InputEvent{{Handler: editor.ToggleFind, Data: nil}})
	h.Logic().FindQueryChan() <- "quick"
	deadline := time.Now().Add(5 * time.Second)
	for {
		v, err := h.Inspect(func(st *editor.State) any { return len(st.Editor.Find.Matches) })
		if err != nil {
			t.Fatalf("Inspect: %v", err)
		}
		if v.(int) > 0 {
			break
		}
		if time.Now().After(deadline) {
			t.Fatal("find never matched")
		}
		time.Sleep(20 * time.Millisecond)
	}
	h.SendInput([]ui.InputEvent{{Handler: editor.FindNext, Data: nil}})
	time.Sleep(100 * time.Millisecond)
	h.SendInput([]ui.InputEvent{{Handler: editor.ToggleFind, Data: nil}})

	assertIdleFrames(t, h, 300*time.Millisecond, time.Second, "editor")
}