package cli

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

	"git.theodohertyfamily.com/tools/wg-wrap/internal/config"
	"git.theodohertyfamily.com/tools/wg-wrap/internal/namespace"
	"git.theodohertyfamily.com/tools/wg-wrap/internal/paths"
	"git.theodohertyfamily.com/tools/wg-wrap/internal/wireguard"
	"git.theodohertyfamily.com/tools/wg-wrap/pkg/wgconf"
)

type App struct {
	Args           []string
	ConfigDir      string // Optional override for profile storage location
	RuntimeBaseDir string // Optional override for namespace/PID tracking
}

func NewApp(args []string) *App {
	return &App{Args: args}
}

func (a *App) getPathManager() *paths.PathManager {
	return paths.NewPathManager(a.ConfigDir, a.RuntimeBaseDir)
}

func (a *App) Route() error {
	for i, arg := range a.Args {
		for j := 0; j < len(arg); j++ {
			if arg[j] == 0 {
				return fmt.Errorf("argument %d contains null byte at position %d", i, j)
			}
		}
	}

	if len(a.Args) > 1 {
		switch a.Args[1] {
		case "show-config":
			return a.showConfig()
		}
	}

	if len(a.Args) > 1 && a.Args[1] == "profile" {
		return a.handleProfileCmd()
	}

	return a.Run()
}

func (a *App) Run() error {
	if len(a.Args) > 1 {
		switch a.Args[1] {
		case "test-ns":
			if !namespace.IsIsolated() {
				if err := namespace.Bootstrap(); err != nil {
					return fmt.Errorf("bootstrap failed: %w", err)
				}
			}
			ok, msg := namespace.VerifyIsolation()
			if !ok {
				return fmt.Errorf("isolation check failed: %s", msg)
			}
			fmt.Println("Isolation Verified: OK")
			return nil
		case "test-args":
			if !namespace.IsIsolated() {
				if err := namespace.Bootstrap(); err != nil {
					return fmt.Errorf("bootstrap failed: %w", err)
				}
			}
			return namespace.VerifyArguments(a.Args)
		}
	}

	cfg := &config.Config{}

	fs := flag.NewFlagSet("wg-wrap", flag.ExitOnError)
	fs.StringVar(&cfg.Profile, "profile", "", "WireGuard profile to use")
	fs.StringVar(&cfg.DNSServer, "dns-server", "", "Override DNS server to use")

	args := a.Args[1:]
	sepIdx := -1
	for i, arg := range args {
		if arg == "--" {
			sepIdx = i
			break
		}
	}

	var flagsToParse []string
	if sepIdx != -1 {
		flagsToParse = args[:sepIdx]
		cfg.Command = args[sepIdx+1:]
	} else {
		flagsToParse = args
	}

	err := fs.Parse(flagsToParse)
	if err != nil {
		return fmt.Errorf("error parsing flags: %w", err)
	}

	if sepIdx == -1 {
		cfg.Command = fs.Args()
	}

	if len(cfg.Command) == 0 {
		return fmt.Errorf("no command provided. use --help for usage")
	}

	if cfg.Profile == "" {
		cfg.Profile = "default"
	}

	if !IsValidProfileName(cfg.Profile) {
		return fmt.Errorf("invalid profile name: %q (only alphanumeric characters, underscores, and hyphens are allowed)", cfg.Profile)
	}

	if namespace.IsIsolated() {
		return a.ExecuteCommand(cfg)
	}

	pm := a.getPathManager()

	// Preserve the host runtime base dir in the environment before bootstrapping
	_ = os.Setenv("WG_WRAP_HOST_RUNTIME_BASE_DIR", pm.RuntimeBaseDir())

	// Acquire startup lock to prevent concurrent bootstrap/joining races
	lockFile, lockErr := namespace.AcquireProfileLock(pm, cfg.Profile)
	if lockErr == nil {
		defer namespace.ReleaseProfileLock(lockFile)
	}

	// Before bootstrapping, see if an active namespace/process for the profile exists.
	// If yes, we can join it!
	activePid, err := namespace.FindActiveProfilePid(pm, cfg.Profile)
	if err == nil && activePid > 0 {
		// Release the lock before executing the command to allow others to join
		namespace.ReleaseProfileLock(lockFile)
		if err := namespace.BootstrapJoin(activePid); err != nil {
			return fmt.Errorf("failed to join existing namespace: %w", err)
		}
		return nil
	}

	if err := namespace.Bootstrap(); err != nil {
		return fmt.Errorf("bootstrap failed: %w", err)
	}

	return nil
}

func (a *App) ExecuteCommand(cfg *config.Config) error {
	if !namespace.IsIsolated() {
		return fmt.Errorf("ExecuteCommand called without namespace isolation")
	}

	pm := a.getPathManager()

	// Acquire execution lock during configuration and startup inside the namespace
	lockFile, lockErr := namespace.AcquireProfileLock(pm, cfg.Profile)
	if lockErr == nil {
		defer namespace.ReleaseProfileLock(lockFile)
	}

	if err := namespace.PruneStalePids(pm, cfg.Profile); err != nil {
		fmt.Printf("failed to prune stale pids: %v\n", err)
	}
	if err := namespace.RegisterProcess(pm, cfg.Profile); err != nil {
		return fmt.Errorf("failed to register process: %w", err)
	}

	defer func() {
		// Re-acquire lock for the entire cleanup sequence to ensure atomic unregister and unpin
		cleanupLock, cleanupErr := namespace.AcquireProfileLock(pm, cfg.Profile)
		if cleanupErr == nil {
			// 1. Unregister the process first.
			if err := namespace.UnregisterProcess(pm, cfg.Profile); err != nil {
				fmt.Printf("failed to unregister process: %v\n", err)
			}

			// 2. Prune and check if we are the last process.
			if err := namespace.PruneStalePids(pm, cfg.Profile); err != nil {
				fmt.Printf("failed to prune stale pids during cleanup: %v\n", err)
			}

			last, lastErr := namespace.IsLastProcess(pm, cfg.Profile)

			if lastErr == nil && last {
				fmt.Printf("Last process exiting. Cleaning up profile %s...\n", cfg.Profile)
				if err := namespace.UnpinNamespace(pm, cfg.Profile); err != nil {
					fmt.Printf("failed to unpin namespace: %v\n", err)
				}
			}
			namespace.ReleaseProfileLock(cleanupLock)
		} else {
			// Fallback if lock fails to ensure we still unregister
			if err := namespace.UnregisterProcess(pm, cfg.Profile); err != nil {
				fmt.Printf("failed to unregister process: %v\n", err)
			}
		}
	}()

	if os.Getenv("WG_WRAP_JOINED") == "1" {
		fmt.Printf("Joining active WireGuard tunnel session for profile %s...\n", cfg.Profile)
	} else {
		fmt.Printf("Initializing WireGuard tunnel for profile %s...\n", cfg.Profile)

		// Parse the profile configuration
		profilesDir := pm.ConfigDir()
		profilePath := filepath.Join(profilesDir, cfg.Profile+".conf")

		// Create tunnel if the file exists
		if _, err := os.Stat(profilePath); err == nil {
			wgCfg, err := wgconf.Parse(profilePath)
			if err != nil {
				return fmt.Errorf("failed to parse profile %s: %w", cfg.Profile, err)
			}

			// Start the WireGuard userspace device & routing table setup
			dnsServer := cfg.DNSServer
			if dnsServer == "" {
				dnsServer = wgCfg.DNS
			}
			if dnsServer == "" {
				dnsServer = "1.1.1.1" // Fallback to safe public DNS to prevent leaks
				hasDefaultRoute := false
				for _, peer := range wgCfg.Peers {
					for _, ip := range peer.AllowedIPs {
						trimmed := strings.TrimSpace(ip)
						if trimmed == "0.0.0.0/0" || trimmed == "::/0" {
							hasDefaultRoute = true
							break
						}
					}
					if hasDefaultRoute {
						break
					}
				}
				if !hasDefaultRoute {
					fmt.Printf("warning: Falling back to 1.1.1.1, but your profile does not route all traffic (0.0.0.0/0). DNS resolution may fail.\n")
				}
			}

			tunnel, err := wireguard.StartTunnel(wgCfg, dnsServer)
			if err != nil {
				return fmt.Errorf("failed to start WireGuard tunnel: %w", err)
			}
			defer tunnel.Close()

			// Pin the namespace so others can join it
			if err := namespace.PinNamespace(pm, cfg.Profile); err != nil {
				fmt.Printf("warning: failed to pin namespace: %v\n", err)
			}
		} else {
			// If profile is not default or it was explicitly requested but doesn't exist, we error
			if cfg.Profile != "default" {
				return fmt.Errorf("profile %s not found: %w", cfg.Profile, err)
			}
			fmt.Printf("warning: default profile configuration not found. Executing command in bare isolation.\n")
		}
	}

	// We can now release the startup lock and execute the command
	namespace.ReleaseProfileLock(lockFile)

	cmd := exec.Command(cfg.Command[0], cfg.Command[1:]...)
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	cmd.Env = os.Environ()

	if err := cmd.Run(); err != nil {
		return fmt.Errorf("command execution failed: %w", err)
	}

	return nil
}

func (a *App) handleProfileCmd() error {
	if len(a.Args) < 3 {
		return fmt.Errorf("usage: wg-wrap profile <list|import|configure|delete|stop> [args]")
	}

	subCmd := a.Args[2]
	switch subCmd {
	case "list":
		return a.handleProfileList()
	case "import":
		if len(a.Args) < 4 {
			return fmt.Errorf("usage: wg-wrap profile import <path> [name]")
		}
		var name string
		if len(a.Args) > 4 {
			name = a.Args[4]
		}
		return a.handleProfileImport(a.Args[3], name)
	case "configure":
		if len(a.Args) < 4 {
			return fmt.Errorf("usage: wg-wrap profile configure <name>")
		}
		return a.handleProfileConfigure(a.Args[3])
	case "delete":
		if len(a.Args) < 4 {
			return fmt.Errorf("usage: wg-wrap profile delete <name>")
		}
		return a.handleProfileDelete(a.Args[3])
	case "stop":
		if len(a.Args) < 4 {
			return fmt.Errorf("usage: wg-wrap profile stop <name>")
		}
		if !IsValidProfileName(a.Args[3]) {
			return fmt.Errorf("invalid profile name: %q", a.Args[3])
		}
		fmt.Printf("Stopping profile %s and unpinning namespace...\n", a.Args[3])
		pm := a.getPathManager()
		if err := namespace.UnpinNamespace(pm, a.Args[3]); err != nil {
			return fmt.Errorf("failed to stop profile: %w", err)
		}
		fmt.Printf("Profile %s stopped and unpinned.\n", a.Args[3])
		return nil
	default:
		return fmt.Errorf("unknown profile subcommand: %s", subCmd)
	}
}

func (a *App) handleProfileConfigure(name string) error {
	if !IsValidProfileName(name) {
		return fmt.Errorf("invalid profile name: %q", name)
	}
	profilesDir := a.getPathManager().ConfigDir()
	profilePath := filepath.Join(profilesDir, name+".conf")
	if _, err := os.Stat(profilePath); os.IsNotExist(err) {
		return fmt.Errorf("profile '%s' not found", name)
	}

	editor := os.Getenv("EDITOR")
	if editor == "" {
		editor = "vi" // Sensible fallback
	}

	// Split editor string into command and arguments (e.g., "vim -R" -> ["vim", "-R"])
	editorArgs := strings.Fields(editor)
	if len(editorArgs) == 0 {
		editorArgs = []string{"vi"}
	}

	fmt.Printf("Opening profile %s in default editor (%s)...\n", name, editor)

	cmd := exec.Command(editorArgs[0], append(editorArgs[1:], profilePath)...)
	cmd.Stdin = os.Stdin
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr

	if err := cmd.Run(); err != nil {
		return fmt.Errorf("editor failed: %w", err)
	}

	return nil
}

func (a *App) handleProfileList() error {
	profilesDir := a.getPathManager().ConfigDir()
	entries, err := os.ReadDir(profilesDir)
	if err != nil {
		return fmt.Errorf("failed to read profiles directory %s: %w", profilesDir, err)
	}

	fmt.Println("Available profiles:")
	found := false
	for _, entry := range entries {
		if !entry.IsDir() && strings.HasSuffix(entry.Name(), ".conf") {
			name := strings.TrimSuffix(entry.Name(), ".conf")
			fmt.Printf("- %s\n", name)
			found = true
		}
	}

	if !found {
		fmt.Println("  (no profiles found)")
	}

	return nil
}

func (a *App) handleProfileImport(srcPath string, name string) error {
	profilesDir := a.getPathManager().ConfigDir()
	if err := os.MkdirAll(profilesDir, 0755); err != nil {
		return fmt.Errorf("failed to create profiles directory: %w", err)
	}

	if _, err := wgconf.Parse(srcPath); err != nil {
		return fmt.Errorf("invalid WireGuard configuration at %s: %w", srcPath, err)
	}

	if name == "" {
		baseName := filepath.Base(srcPath)
		name = strings.TrimSuffix(baseName, filepath.Ext(baseName))
		if name == "" {
			return fmt.Errorf("invalid source filename")
		}
	}

	if !IsValidProfileName(name) {
		return fmt.Errorf("invalid profile name: %q", name)
	}

	destPath := filepath.Join(profilesDir, name+".conf")
	if _, err := os.Stat(destPath); err == nil {
		return fmt.Errorf("profile '%s' already exists", name)
	}

	data, err := os.ReadFile(srcPath)
	if err != nil {
		return fmt.Errorf("failed to read source file: %w", err)
	}

	if err := os.WriteFile(destPath, data, 0644); err != nil {
		return fmt.Errorf("failed to write profile to %s: %w", destPath, err)
	}

	fmt.Printf("Profile '%s' imported successfully to %s\n", name, destPath)
	return nil
}

func (a *App) handleProfileDelete(name string) error {
	if !IsValidProfileName(name) {
		return fmt.Errorf("invalid profile name: %q", name)
	}
	profilesDir := a.getPathManager().ConfigDir()
	destPath := filepath.Join(profilesDir, name+".conf")

	if _, err := os.Stat(destPath); os.IsNotExist(err) {
		return fmt.Errorf("profile '%s' not found", name)
	}

	if err := os.Remove(destPath); err != nil {
		return fmt.Errorf("failed to delete profile %s: %w", name, err)
	}

	fmt.Printf("Profile '%s' deleted successfully\n", name)
	return nil
}

func (a *App) showConfig() error {
	cfg := &config.Config{}
	fs := flag.NewFlagSet("wg-wrap", flag.ExitOnError)
	fs.StringVar(&cfg.Profile, "profile", "default", "WireGuard profile to use")
	fs.StringVar(&cfg.DNSServer, "dns-server", "", "Override DNS server to use")

	if len(a.Args) > 2 {
		_ = fs.Parse(a.Args[2:])
	}

	if !IsValidProfileName(cfg.Profile) {
		return fmt.Errorf("invalid profile name: %q", cfg.Profile)
	}

	pm := paths.NewPathManager(a.ConfigDir, a.RuntimeBaseDir)
	profilePath := pm.ProfileNamespacePath(cfg.Profile)
	pidsPath := pm.ProfilePidsDir(cfg.Profile)

	fmt.Printf("Configuration:\n")
	fmt.Printf("  Profile:       %s\n", cfg.Profile)
	fmt.Printf("  DNS Server:    %s\n", cfg.DNSServer)
	fmt.Printf("  Config Dir:    %s\n", pm.ConfigDir())
	fmt.Printf("  Runtime Base:  %s\n", pm.RuntimeBaseDir())
	fmt.Printf("  Profile Path:  %s\n", profilePath)
	fmt.Printf("  PIDs Path:     %s\n", pidsPath)
	fmt.Printf("  Isolated:      %v\n", namespace.IsIsolated())
	fmt.Printf("  UID:           %d\n", os.Getuid())
	return nil
}

// IsValidProfileName checks if a WireGuard profile name is safe and valid.
// It allows only alphanumeric characters, underscores, and hyphens, and prevents
// directory traversal attacks and hidden files.
func IsValidProfileName(name string) bool {
	if name == "" {
		return false
	}
	for _, r := range name {
		if (r < 'a' || r > 'z') && (r < 'A' || r > 'Z') && (r < '0' || r > '9') && r != '_' && r != '-' {
			return false
		}
	}
	if name == "." || name == ".." || strings.HasPrefix(name, "-") {
		return false
	}
	return true
}