package worker

import (
	"os"
	"path/filepath"
	"strings"
)

// GPUType represents different GPU types
type GPUType string

const (
	GPUTypeNVIDIA GPUType = "nvidia"
	GPUTypeApple  GPUType = "apple"
	GPUTypeNone   GPUType = "none"
)

// GPUDetector interface for detecting GPU availability
type GPUDetector interface {
	DetectGPUCount() int
	GetGPUType() GPUType
	GetDevicePaths() []string
}

// NVIDIA GPUDetector implementation
type NVIDIADetector struct{}

func (d *NVIDIADetector) DetectGPUCount() int {
	if n, ok := envInt("FETCH_ML_GPU_COUNT"); ok && n >= 0 {
		return n
	}
	// Could use nvidia-sml or other detection methods here
	return 0
}

func (d *NVIDIADetector) GetGPUType() GPUType {
	return GPUTypeNVIDIA
}

func (d *NVIDIADetector) GetDevicePaths() []string {
	// Prefer standard NVIDIA device nodes when present.
	patterns := []string{
		"/dev/nvidiactl",
		"/dev/nvidia-modeset",
		"/dev/nvidia-uvm",
		"/dev/nvidia-uvm-tools",
		"/dev/nvidia*",
	}
	seen := make(map[string]struct{})
	out := make([]string, 0, 8)
	for _, pat := range patterns {
		if filepath.Base(pat) == pat {
			continue
		}
		if strings.Contains(pat, "*") {
			matches, _ := filepath.Glob(pat)
			for _, m := range matches {
				if _, ok := seen[m]; ok {
					continue
				}
				if _, err := os.Stat(m); err != nil {
					continue
				}
				seen[m] = struct{}{}
				out = append(out, m)
			}
			continue
		}
		if _, ok := seen[pat]; ok {
			continue
		}
		if _, err := os.Stat(pat); err != nil {
			continue
		}
		seen[pat] = struct{}{}
		out = append(out, pat)
	}
	// Fallback for non-NVIDIA setups where only generic DRM device exists.
	if len(out) == 0 {
		if _, err := os.Stat("/dev/dri"); err == nil {
			out = append(out, "/dev/dri")
		}
	}
	return out
}

// Apple M-series GPUDetector implementation
type AppleDetector struct {
	enabled bool
}

func (d *AppleDetector) DetectGPUCount() int {
	if n, ok := envInt("FETCH_ML_GPU_COUNT"); ok && n >= 0 {
		return n
	}
	if d.enabled {
		return 1
	}
	return 0
}

func (d *AppleDetector) GetGPUType() GPUType {
	return GPUTypeApple
}

func (d *AppleDetector) GetDevicePaths() []string {
	return []string{"/dev/metal", "/dev/mps"}
}

// None GPUDetector implementation
type NoneDetector struct{}

func (d *NoneDetector) DetectGPUCount() int {
	return 0
}

func (d *NoneDetector) GetGPUType() GPUType {
	return GPUTypeNone
}

func (d *NoneDetector) GetDevicePaths() []string {
	return nil
}

// GPUDetectorFactory creates appropriate GPU detector based on config
type GPUDetectorFactory struct{}

func (f *GPUDetectorFactory) CreateDetector(cfg *Config) GPUDetector {
	// Check for explicit environment override
	if gpuType := os.Getenv("FETCH_ML_GPU_TYPE"); gpuType != "" {
		switch gpuType {
		case string(GPUTypeNVIDIA):
			return &NVIDIADetector{}
		case string(GPUTypeApple):
			return &AppleDetector{enabled: true}
		case string(GPUTypeNone):
			return &NoneDetector{}
		}
	}

	// Respect configured vendor when explicitly set.
	if cfg != nil {
		switch GPUType(cfg.GPUVendor) {
		case GPUTypeApple:
			return &AppleDetector{enabled: cfg.AppleGPU.Enabled}
		case GPUTypeNone:
			return &NoneDetector{}
		case GPUTypeNVIDIA:
			return &NVIDIADetector{}
		case "amd":
			// AMD uses similar device exposure patterns in this codebase.
			return &NVIDIADetector{}
		}
	}

	// Auto-detect based on config
	if cfg != nil {
		if cfg.AppleGPU.Enabled {
			return &AppleDetector{enabled: true}
		}
		if len(cfg.GPUDevices) > 0 {
			return &NVIDIADetector{}
		}
	}

	// Default to no GPU
	return &NoneDetector{}
}