CPU patterns fallback

internal/video/generator.go

@@ -0,0 +1,61 @@
+package video
+
+import (
+	"errors"
+	"fmt"
+	"log"
+
+	"mxl-pattern-generator/internal/generator"
+)
+
+type generatorFactory func() (generator.FrameGenerator, error)
+
+func newFrameGenerator(cfg Config, pattern pattern) (generator.FrameGenerator, Backend, error) {
+	newGPU := func() (generator.FrameGenerator, error) {
+		return generator.NewWGPUGenerator(cfg.Width(), cfg.Height(), pattern.kernelSource)
+	}
+	newCPU := func() (generator.FrameGenerator, error) {
+		return generator.NewCPUPatternGenerator(cfg.Width(), cfg.Height(), cfg.Pattern)
+	}
+	return selectFrameGenerator(cfg.Backend, newGPU, newCPU)
+}
+
+func selectFrameGenerator(
+	backend Backend,
+	newGPU, newCPU generatorFactory,
+) (generator.FrameGenerator, Backend, error) {
+	switch backend {
+	case BackendGPU:
+		gen, err := newGPU()
+		if err != nil {
+			return nil, "", fmt.Errorf("initialize GPU video generator: %w", err)
+		}
+		return gen, BackendGPU, nil
+
+	case BackendCPU:
+		gen, err := newCPU()
+		if err != nil {
+			return nil, "", fmt.Errorf("initialize CPU video generator: %w", err)
+		}
+		return gen, BackendCPU, nil
+
+	case "", BackendAuto:
+		gpuGen, gpuErr := newGPU()
+		if gpuErr == nil {
+			return gpuGen, BackendGPU, nil
+		}
+		log.Printf("GPU video generator unavailable, falling back to CPU: %v", gpuErr)
+
+		cpuGen, cpuErr := newCPU()
+		if cpuErr == nil {
+			return cpuGen, BackendCPU, nil
+		}
+		return nil, "", errors.Join(
+			fmt.Errorf("initialize GPU video generator: %w", gpuErr),
+			fmt.Errorf("initialize CPU video generator: %w", cpuErr),
+		)
+
+	default:
+		return nil, "", fmt.Errorf("unsupported video backend %q", backend)
+	}
+}