package display

import (
	"testing"

	"git.piksar.eu/piotr/groundstation/internal/osd"
)

// stubSource serves one fixed snapshot, or none.
type stubSource struct {
	snapshot osd.Snapshot
	ok       bool
}

func (s stubSource) Latest() (osd.Snapshot, bool) { return s.snapshot, s.ok }

func armedSource(sequence uint16) stubSource {
	return stubSource{snapshot: osd.Snapshot{Sequence: sequence, Armed: true, Power: true}, ok: true}
}

func TestOSDTemplateStaysTransparentWhileVideoAbsent(t *testing.T) {
	canvas := &fakeCanvas{width: 800, height: 600}

	NewOSDTemplate(NewVideoPresence(), armedSource(1)).Draw(canvas)

	clears, flushes := canvas.drawCounts()
	if clears != 1 || flushes != 1 {
		t.Fatalf("clears=%d flushes=%d want 1 and 1", clears, flushes)
	}
	if lines := canvas.lines(); len(lines) != 0 {
		t.Fatalf("OSD lines=%q want none: without video the fallback canvas owns the screen", lines)
	}
}

func TestOSDTemplateDrawsMinimalTelemetryWhileVideoPresent(t *testing.T) {
	canvas := &fakeCanvas{width: 800, height: 600}
	presence := NewVideoPresence()
	presence.SetActive(true)

	NewOSDTemplate(presence, armedSource(7)).Draw(canvas)

	clears, flushes := canvas.drawCounts()
	if clears != 1 || flushes != 1 {
		t.Fatalf("clears=%d flushes=%d want 1 and 1", clears, flushes)
	}
	lines := canvas.lines()
	want := []string{"ARM ARMED", "PWR ON"}
	if len(lines) != len(want) {
		t.Fatalf("lines=%q want %q", lines, want)
	}
	for i := range want {
		if lines[i] != want[i] {
			t.Fatalf("line %d=%q want %q", i, lines[i], want[i])
		}
	}
}

func TestOSDTemplateDrawsDisarmedAndPoweredOffState(t *testing.T) {
	canvas := &fakeCanvas{width: 800, height: 600}
	presence := NewVideoPresence()
	presence.SetActive(true)

	NewOSDTemplate(presence, stubSource{ok: true}).Draw(canvas)

	lines := canvas.lines()
	want := []string{"ARM OFF", "PWR OFF"}
	if len(lines) != len(want) {
		t.Fatalf("lines=%q want %q", lines, want)
	}
	for i := range want {
		if lines[i] != want[i] {
			t.Fatalf("line %d=%q want %q", i, lines[i], want[i])
		}
	}
}

func TestOSDTemplateStaysTransparentWithoutASnapshotWhileVideoPresent(t *testing.T) {
	canvas := &fakeCanvas{width: 800, height: 600}
	presence := NewVideoPresence()
	presence.SetActive(true)

	NewOSDTemplate(presence, stubSource{}).Draw(canvas)

	if lines := canvas.lines(); len(lines) != 0 {
		t.Fatalf("OSD lines=%q want none without a published snapshot", lines)
	}
}

func TestOSDTemplateGatesOnObservedVideoPresenceNotSnapshotVideo(t *testing.T) {
	// The rendering gate is the video lifecycle the display observes on the
	// display server, never the snapshot's Video field: the supervisor's
	// field is its launcher knowledge, while the display trusts only the
	// presented video output itself.
	canvas := &fakeCanvas{width: 800, height: 600}
	presence := NewVideoPresence()

	claimingVideo := stubSource{snapshot: osd.Snapshot{Armed: true, Video: true}, ok: true}
	NewOSDTemplate(presence, claimingVideo).Draw(canvas)
	if lines := canvas.lines(); len(lines) != 0 {
		t.Fatalf("lines=%q want none: snapshot presence must never replace the observed lifecycle", lines)
	}

	denyingVideo := stubSource{snapshot: osd.Snapshot{Armed: true}, ok: true}
	presence.SetActive(true)
	NewOSDTemplate(presence, denyingVideo).Draw(canvas)
	if lines := canvas.lines(); len(lines) == 0 {
		t.Fatal("the observed video lifecycle must gate rendering even when the snapshot denies video")
	}
}

func TestOSDTemplateNeverDrawsTheFallbackText(t *testing.T) {
	canvas := &fakeCanvas{width: 800, height: 600}
	presence := NewVideoPresence()
	template := NewOSDTemplate(presence, armedSource(3))

	for _, active := range []bool{false, true, false} {
		presence.SetActive(active)
		template.Draw(canvas)
		for _, line := range canvas.lines() {
			if line == wantFallbackText {
				t.Fatalf("the OSD is a telemetry surface, not a fallback: drew %q", line)
			}
		}
	}
}