// Package platform detects the runtime OS and environment,
// providing platform-specific paths and configuration defaults.
package platform

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

// Platform holds information about the current runtime environment.
type Platform struct {
	OS   string // "linux", "windows", "darwin"
	Arch string // "amd64", "arm64"

	IsTermux  bool // Running inside Termux (ANDROID_ROOT set)
	IsWSL     bool // Running inside WSL
	IsDocker  bool // Running inside a Docker container
	IsWindows bool // runtime.GOOS == "windows"
	IsLinux   bool // runtime.GOOS == "linux"
	IsDarwin  bool // runtime.GOOS == "darwin"
	IsARM64   bool // runtime.GOARCH == "arm64"
}

// Detect returns the current platform information.
func Detect() *Platform {
	p := &Platform{
		OS:        runtime.GOOS,
		Arch:      runtime.GOARCH,
		IsWindows: runtime.GOOS == "windows",
		IsLinux:   runtime.GOOS == "linux",
		IsDarwin:  runtime.GOOS == "darwin",
		IsARM64:   runtime.GOARCH == "arm64",
	}

	// Detect Termux
	if _, ok := os.LookupEnv("ANDROID_ROOT"); ok {
		p.IsTermux = true
	}

	// Detect WSL
	if _, err := os.Stat("/proc/sys/fs/binfmt_misc/WSL"); err == nil {
		p.IsWSL = true
	}

	// Detect Docker
	if _, err := os.Stat("/.dockerenv"); err == nil {
		p.IsDocker = true
	}

	return p
}

// DataDir returns the default application data directory.
func (p *Platform) DataDir() string {
	home, _ := os.UserHomeDir()
	switch {
	case p.IsWindows:
		return filepath.Join(os.Getenv("APPDATA"), "Cyrene")
	case p.IsDarwin:
		return filepath.Join(home, "Library", "Application Support", "Cyrene")
	case p.IsTermux:
		return filepath.Join(home, "storage", "shared", "Cyrene")
	default: // Linux
		return filepath.Join(home, ".local", "share", "cyrene")
	}
}

// ConfigDir returns the default configuration directory.
func (p *Platform) ConfigDir() string {
	home, _ := os.UserHomeDir()
	switch {
	case p.IsWindows:
		return filepath.Join(os.Getenv("APPDATA"), "Cyrene", "config")
	case p.IsDarwin:
		return filepath.Join(home, "Library", "Application Support", "Cyrene", "config")
	case p.IsTermux:
		return filepath.Join(home, ".config", "cyrene")
	default: // Linux
		return filepath.Join(home, ".config", "cyrene")
	}
}

// CacheDir returns the default cache directory.
func (p *Platform) CacheDir() string {
	home, _ := os.UserHomeDir()
	switch {
	case p.IsWindows:
		return filepath.Join(os.Getenv("LOCALAPPDATA"), "Cyrene", "cache")
	case p.IsDarwin:
		return filepath.Join(home, "Library", "Caches", "Cyrene")
	default: // Linux / Termux
		return filepath.Join(home, ".cache", "cyrene")
	}
}

// EnsureDirs creates the data, config, and cache directories if they don't exist.
func (p *Platform) EnsureDirs() error {
	for _, dir := range []string{p.DataDir(), p.ConfigDir(), p.CacheDir()} {
		if err := os.MkdirAll(dir, 0o755); err != nil {
			return err
		}
	}
	return nil
}

// DefaultNATSURL returns the default NATS connection URL.
func (p *Platform) DefaultNATSURL() string {
	return "nats://localhost:4222"
}

// DefaultPGHost returns the default PostgreSQL host.
func (p *Platform) DefaultPGHost() string {
	return "localhost"
}

// Summary returns a human-readable platform description.
func (p *Platform) Summary() string {
	s := p.OS + "/" + p.Arch
	var tags []string
	if p.IsDocker {
		tags = append(tags, "docker")
	}
	if p.IsWSL {
		tags = append(tags, "wsl")
	}
	if p.IsTermux {
		tags = append(tags, "termux")
	}
	if len(tags) > 0 {
		s += " ("
		for i, t := range tags {
			if i > 0 {
				s += ", "
			}
			s += t
		}
		s += ")"
	}
	return s
}