// Package blender: GPU backend detection for HIP vs NVIDIA.
package blender

import (
	"bufio"
	"fmt"
	"os"
	"os/exec"
	"path/filepath"
	"strings"

	"jiggablend/pkg/scripts"
)

// DetectGPUBackends runs a minimal Blender script to detect whether HIP (AMD) and/or
// NVIDIA (CUDA/OptiX) devices are available. Use this to decide whether to force CPU
// for Blender < 4.x (only force when HIP is present, since HIP has no official support pre-4).
func DetectGPUBackends(blenderBinary, scriptDir string) (hasHIP, hasNVIDIA bool, err error) {
	scriptPath := filepath.Join(scriptDir, "detect_gpu_backends.py")
	if err := os.WriteFile(scriptPath, []byte(scripts.DetectGPUBackends), 0644); err != nil {
		return false, false, fmt.Errorf("write detection script: %w", err)
	}
	defer os.Remove(scriptPath)

	env := TarballEnv(blenderBinary, os.Environ())
	cmd := exec.Command(blenderBinary, "-b", "--python", scriptPath)
	cmd.Env = env
	cmd.Dir = scriptDir
	out, err := cmd.CombinedOutput()
	if err != nil {
		return false, false, fmt.Errorf("run blender detection: %w (output: %s)", err, string(out))
	}

	scanner := bufio.NewScanner(strings.NewReader(string(out)))
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		switch line {
		case "HAS_HIP":
			hasHIP = true
		case "HAS_NVIDIA":
			hasNVIDIA = true
		}
	}
	return hasHIP, hasNVIDIA, scanner.Err()
}