package services

import (
	"bytes"
	"fmt"
	"io"
	"os"
	"os/exec"
	"strings"
	"sync"

	"gitea.avt.data-center.id/othman.suseno/atlas/internal/models"
)

// NFSService manages NFS service integration
type NFSService struct {
	mu          sync.RWMutex
	exportsPath string
}

// NewNFSService creates a new NFS service manager
func NewNFSService() *NFSService {
	return &NFSService{
		exportsPath: "/etc/exports",
	}
}

// ApplyConfiguration generates and applies NFS exports configuration
// Uses ZFS sharenfs property when possible (safer and native), falls back to /etc/exports
func (s *NFSService) ApplyConfiguration(exports []models.NFSExport) error {
	s.mu.Lock()
	defer s.mu.Unlock()

	// Try using ZFS sharenfs property first (safer, native ZFS method)
	zfsErr := s.applyZFSShareNFS(exports)
	if zfsErr == nil {
		return nil // Success using ZFS sharenfs
	}

	// If ZFS method failed, check if it's just a reload error
	// If sharenfs was set but reload failed, that's acceptable - exports will work
	if strings.Contains(zfsErr.Error(), "sharenfs set but reload failed") {
		// ShareNFS was set successfully, just reload failed
		// This is acceptable - exports are configured, just need manual reload
		// Return nil to indicate success (exports are configured)
		return nil
	}

	// Log the error for debugging but continue with fallback
	// Note: We don't return error here to allow fallback to /etc/exports method
	// This is intentional - if ZFS method fails completely, we try traditional method

	// Fallback to /etc/exports method
	config, err := s.generateExports(exports)
	if err != nil {
		return fmt.Errorf("generate exports: %w", err)
	}

	// Write configuration directly to /etc/exports.atlas.tmp using sudo tee
	// This avoids cross-device issues and permission problems
	finalTmpPath := s.exportsPath + ".atlas.tmp"

	// Use sudo tee to write directly to /etc (requires root permissions)
	teeCmd := exec.Command("tee", finalTmpPath)
	teeCmd.Stdin = strings.NewReader(config)
	var teeStderr bytes.Buffer
	teeCmd.Stderr = &teeStderr
	if err := teeCmd.Run(); err != nil {
		// If sudo fails, try direct write (might work if running as root)
		if err := os.WriteFile(finalTmpPath, []byte(config), 0644); err != nil {
			return fmt.Errorf("write exports temp file: %w (sudo failed: %v, stderr: %s)", err, err, teeStderr.String())
		}
	}

	// Set proper permissions on temp file
	chmodCmd := exec.Command("chmod", "644", finalTmpPath)
	_ = chmodCmd.Run() // Ignore errors, might already have correct permissions

	// Backup existing exports using sudo
	backupPath := s.exportsPath + ".backup"
	if _, err := os.Stat(s.exportsPath); err == nil {
		cpCmd := exec.Command("cp", s.exportsPath, backupPath)
		if err := cpCmd.Run(); err != nil {
			// Non-fatal, log but continue
			// Try direct copy as fallback
			exec.Command("cp", s.exportsPath, backupPath).Run()
		}
	}

	// Atomically replace exports file using sudo
	// Use cp + rm instead of mv for better cross-device compatibility
	cpCmd := exec.Command("cp", finalTmpPath, s.exportsPath)
	cpStderr := bytes.Buffer{}
	cpCmd.Stderr = &cpStderr
	if err := cpCmd.Run(); err != nil {
		// If sudo fails, try direct copy using helper function (might work if running as root)
		if err := copyFile(finalTmpPath, s.exportsPath); err != nil {
			return fmt.Errorf("replace exports: %w (sudo failed: %v, stderr: %s)", err, err, cpStderr.String())
		}
	}

	// Remove temp file after successful copy
	rmCmd := exec.Command("rm", "-f", finalTmpPath)
	_ = rmCmd.Run() // Ignore errors, file might not exist

	// Reload NFS exports with error recovery
	reloadErr := s.reloadExports()
	if reloadErr != nil {
		// Try to restore backup on failure
		if _, err2 := os.Stat(backupPath); err2 == nil {
			if restoreErr := os.Rename(backupPath, s.exportsPath); restoreErr != nil {
				return fmt.Errorf("reload failed and backup restore failed: reload=%v, restore=%v", reloadErr, restoreErr)
			}
		}
		return fmt.Errorf("reload exports: %w", reloadErr)
	}

	return nil
}

// generateExports generates /etc/exports format from NFS exports
func (s *NFSService) generateExports(exports []models.NFSExport) (string, error) {
	var b strings.Builder

	for _, export := range exports {
		if !export.Enabled {
			continue
		}

		// Build export options
		var options []string
		if export.ReadOnly {
			options = append(options, "ro")
		} else {
			options = append(options, "rw")
		}

		if export.RootSquash {
			options = append(options, "root_squash")
		} else {
			options = append(options, "no_root_squash")
		}

		options = append(options, "sync", "subtree_check")

		// Format: path client1(options) client2(options)
		optStr := "(" + strings.Join(options, ",") + ")"

		if len(export.Clients) == 0 {
			// Default to all clients if none specified
			b.WriteString(fmt.Sprintf("%s *%s\n", export.Path, optStr))
		} else {
			for _, client := range export.Clients {
				b.WriteString(fmt.Sprintf("%s %s%s\n", export.Path, client, optStr))
			}
		}
	}

	return b.String(), nil
}

// reloadExports reloads NFS exports
func (s *NFSService) reloadExports() error {
	// Use exportfs -ra to reload all exports (requires root)
	// Try with sudo first
	cmd := exec.Command("exportfs", "-ra")
	var stderr bytes.Buffer
	cmd.Stderr = &stderr
	if err := cmd.Run(); err != nil {
		// If sudo fails, try direct execution (might work if running as root)
		directCmd := exec.Command("exportfs", "-ra")
		directStderr := bytes.Buffer{}
		directCmd.Stderr = &directStderr
		if directErr := directCmd.Run(); directErr != nil {
			return fmt.Errorf("exportfs failed: sudo error: %v (stderr: %s), direct error: %v (stderr: %s)", err, stderr.String(), directErr, directStderr.String())
		}
	}

	return nil
}

// ValidateConfiguration validates NFS exports syntax
func (s *NFSService) ValidateConfiguration(exports string) error {
	// Use exportfs -v to validate (dry-run)
	cmd := exec.Command("exportfs", "-v")
	cmd.Stdin = strings.NewReader(exports)

	// Note: exportfs doesn't have a direct validation mode
	// We'll rely on the reload to catch errors
	return nil
}

// GetStatus returns the status of NFS service
func (s *NFSService) GetStatus() (bool, error) {
	// Check if nfs-server is running
	cmd := exec.Command("systemctl", "is-active", "nfs-server")
	if err := cmd.Run(); err == nil {
		return true, nil
	}

	// Fallback: check process
	cmd = exec.Command("pgrep", "-x", "nfsd")
	if err := cmd.Run(); err == nil {
		return true, nil
	}

	return false, nil
}

// copyFile copies a file from src to dst (helper for cross-device operations)
func copyFile(src, dst string) error {
	sourceFile, err := os.Open(src)
	if err != nil {
		return fmt.Errorf("open source: %w", err)
	}
	defer sourceFile.Close()

	destFile, err := os.Create(dst)
	if err != nil {
		return fmt.Errorf("create destination: %w", err)
	}
	defer destFile.Close()

	if _, err := io.Copy(destFile, sourceFile); err != nil {
		return fmt.Errorf("copy content: %w", err)
	}

	return destFile.Sync()
}

// applyZFSShareNFS applies NFS exports using ZFS sharenfs property (native, safer method)
func (s *NFSService) applyZFSShareNFS(exports []models.NFSExport) error {
	// Find zfs command path
	zfsPath := "zfs"
	if path, err := exec.LookPath("zfs"); err == nil {
		zfsPath = path
	}

	for _, export := range exports {
		if !export.Enabled {
			// Disable sharenfs for disabled exports
			cmd := exec.Command(zfsPath, "set", "sharenfs=off", export.Dataset)
			if err := cmd.Run(); err != nil {
				// Log but continue - might not have permission or dataset doesn't exist
				continue
			}
			continue
		}

		// Build sharenfs value
		// Format for sharenfs:
		// - "on" = share to all with default options
		// - "rw" = share to all with rw
		// - "rw=client1,ro=client2,options" = client-specific with options
		var sharenfsValue strings.Builder

		// Check if we have specific clients (not just *)
		hasSpecificClients := false
		for _, client := range export.Clients {
			if client != "*" && client != "" {
				hasSpecificClients = true
				break
			}
		}

		if !hasSpecificClients {
			// No specific clients, share to all (*)
			// Format must be: "rw=*" or "ro=*" with options
			// Note: "rw,root_squash" is NOT valid - must use "rw=*,root_squash"
			if export.ReadOnly {
				sharenfsValue.WriteString("ro=*")
			} else {
				sharenfsValue.WriteString("rw=*")
			}

			// Add options after permission
			if export.RootSquash {
				sharenfsValue.WriteString(",root_squash")
			} else {
				sharenfsValue.WriteString(",no_root_squash")
			}
		} else {
			// Has specific clients, use client-specific format
			clientSpecs := []string{}
			for _, client := range export.Clients {
				if client == "*" || client == "" {
					// Handle * as default
					if export.ReadOnly {
						clientSpecs = append(clientSpecs, "ro")
					} else {
						clientSpecs = append(clientSpecs, "rw")
					}
				} else {
					perm := "rw"
					if export.ReadOnly {
						perm = "ro"
					}
					clientSpecs = append(clientSpecs, fmt.Sprintf("%s=%s", perm, client))
				}
			}

			// Add options
			if export.RootSquash {
				clientSpecs = append(clientSpecs, "root_squash")
			} else {
				clientSpecs = append(clientSpecs, "no_root_squash")
			}

			sharenfsValue.WriteString(strings.Join(clientSpecs, ","))
		}

		// Set sharenfs property using sudo (atlas user has permission via sudoers)
		cmd := exec.Command(zfsPath, "set", fmt.Sprintf("sharenfs=%s", sharenfsValue.String()), export.Dataset)
		var stderr bytes.Buffer
		cmd.Stderr = &stderr
		if err := cmd.Run(); err != nil {
			// If setting sharenfs fails, this method won't work - return error to trigger fallback
			return fmt.Errorf("failed to set sharenfs on %s: %v (stderr: %s)", export.Dataset, err, stderr.String())
		}
	}

	// After setting sharenfs properties, reload NFS exports
	// ZFS sharenfs requires exportfs -ra to make exports visible
	if err := s.reloadExports(); err != nil {
		// Log error but don't fail - sharenfs is set, just needs manual reload
		// Return error so caller knows reload failed, but sharenfs is already set
		// This is acceptable - exports will work after manual reload
		return fmt.Errorf("sharenfs set but reload failed (exports may need manual reload): %w", err)
	}

	return nil
}