package backend

import (
	"bytes"
	"context"
	"image/png"
	"io"
	"testing"
)

func TestMockGeneratesValidPNG(t *testing.T) {
	be, err := NewMock("mock", nil)
	if err != nil {
		t.Fatalf("NewMock: %v", err)
	}
	if be.Name() != "mock" {
		t.Errorf("Name() = %q", be.Name())
	}
	res, err := be.Generate(context.Background(), Request{
		Prompt: "test prompt",
		Width:  64,
		Height: 64,
		Seed:   1234,
	})
	if err != nil {
		t.Fatalf("Generate: %v", err)
	}
	defer res.ImageReader.Close()
	if res.MimeType != "image/png" {
		t.Errorf("mime = %q", res.MimeType)
	}
	body, err := io.ReadAll(res.ImageReader)
	if err != nil {
		t.Fatalf("read body: %v", err)
	}
	img, err := png.Decode(bytes.NewReader(body))
	if err != nil {
		t.Fatalf("decode png: %v", err)
	}
	if img.Bounds().Dx() != 64 || img.Bounds().Dy() != 64 {
		t.Errorf("dims = %v", img.Bounds())
	}
	if seed, ok := res.Metadata["seed"].(int64); !ok || seed != 1234 {
		t.Errorf("metadata seed = %v", res.Metadata["seed"])
	}
}

func TestMockDeterministicBySeed(t *testing.T) {
	be, _ := NewMock("mock", nil)
	gen := func() []byte {
		res, err := be.Generate(context.Background(), Request{Prompt: "p", Width: 32, Height: 32, Seed: 99})
		if err != nil {
			t.Fatalf("Generate: %v", err)
		}
		defer res.ImageReader.Close()
		b, _ := io.ReadAll(res.ImageReader)
		return b
	}
	a := gen()
	b := gen()
	if !bytes.Equal(a, b) {
		t.Errorf("same seed produced different images: %d vs %d bytes", len(a), len(b))
	}
}

func TestRegistryBuildAndUnknown(t *testing.T) {
	r := NewRegistry()
	r.Register("mock", NewMock)
	if !r.Has("mock") {
		t.Errorf("Has(mock) = false")
	}
	be, err := r.Build("mock", "instance-1", nil)
	if err != nil {
		t.Fatalf("Build: %v", err)
	}
	if be.Name() != "instance-1" {
		t.Errorf("Name() = %q", be.Name())
	}
	if _, err := r.Build("nope", "x", nil); err == nil {
		t.Errorf("expected error for unknown type")
	}
}

func TestRegistryDuplicatePanic(t *testing.T) {
	r := NewRegistry()
	r.Register("dup", NewMock)
	defer func() {
		if recover() == nil {
			t.Errorf("expected panic on duplicate Register")
		}
	}()
	r.Register("dup", NewMock)
}