package config

import (
	"bufio"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
	"time"

	"git.gostacks.org/iwasforcedtobehere/fastestmirror/internal/distro"
)

// ConfigManager handles backup and modification of distribution config files
type ConfigManager struct {
	DistroInfo *distro.DistroInfo
	BackupDir  string
}

// NewConfigManager creates a new configuration manager
func NewConfigManager(distroInfo *distro.DistroInfo) *ConfigManager {
	return &ConfigManager{
		DistroInfo: distroInfo,
		BackupDir:  "/etc/fastestmirror/backups",
	}
}

// BackupConfig creates a backup of the current configuration
func (cm *ConfigManager) BackupConfig() (string, error) {
	configFile := cm.DistroInfo.GetConfigFile()
	if configFile == "" {
		return "", fmt.Errorf("no configuration file defined for %s", cm.DistroInfo.Family)
	}

	// Create backup directory if it doesn't exist
	if err := os.MkdirAll(cm.BackupDir, 0755); err != nil {
		return "", fmt.Errorf("failed to create backup directory: %w", err)
	}

	// Generate backup filename with timestamp
	timestamp := time.Now().Format("20060102-150405")
	backupName := fmt.Sprintf("%s.backup.%s", filepath.Base(configFile), timestamp)
	backupPath := filepath.Join(cm.BackupDir, backupName)

	// Copy original file to backup location
	if err := cm.copyFile(configFile, backupPath); err != nil {
		return "", fmt.Errorf("failed to create backup: %w", err)
	}

	return backupPath, nil
}

// ApplyMirror applies the fastest mirror to the configuration
func (cm *ConfigManager) ApplyMirror(mirrorURL string) error {
	switch cm.DistroInfo.Family {
	case "debian":
		return cm.applyDebianMirror(mirrorURL)
	case "arch":
		return cm.applyArchMirror(mirrorURL)
	default:
		return fmt.Errorf("configuration management for %s family not implemented yet", cm.DistroInfo.Family)
	}
}

// applyDebianMirror updates /etc/apt/sources.list for Debian-based systems
func (cm *ConfigManager) applyDebianMirror(mirrorURL string) error {
	configFile := "/etc/apt/sources.list"

	// Read current configuration
	file, err := os.Open(configFile)
	if err != nil {
		return fmt.Errorf("failed to read %s: %w", configFile, err)
	}
	defer file.Close()

	var lines []string
	scanner := bufio.NewScanner(file)

	// Process each line and replace mirror URLs
	for scanner.Scan() {
		line := scanner.Text()
		if strings.TrimSpace(line) == "" || strings.HasPrefix(strings.TrimSpace(line), "#") {
			// Keep comments and empty lines as-is
			lines = append(lines, line)
			continue
		}

		// Parse and update deb/deb-src lines
		if strings.HasPrefix(strings.TrimSpace(line), "deb") {
			updatedLine := cm.updateDebianLine(line, mirrorURL)
			lines = append(lines, updatedLine)
		} else {
			lines = append(lines, line)
		}
	}

	if err := scanner.Err(); err != nil {
		return fmt.Errorf("error reading %s: %w", configFile, err)
	}

	// Write updated configuration
	return cm.writeLines(configFile, lines)
}

// updateDebianLine updates a single deb line with the new mirror URL
func (cm *ConfigManager) updateDebianLine(line, newMirrorURL string) string {
	parts := strings.Fields(line)
	if len(parts) < 3 {
		return line // Invalid line, keep as-is
	}

	// parts[0] = "deb" or "deb-src"
	// parts[1] = URL
	// parts[2] = suite/codename
	// parts[3+] = components

	parts[1] = strings.TrimSuffix(newMirrorURL, "/") + "/"
	return strings.Join(parts, " ")
}

// applyArchMirror updates /etc/pacman.d/mirrorlist for Arch-based systems
func (cm *ConfigManager) applyArchMirror(mirrorURL string) error {
	configFile := "/etc/pacman.d/mirrorlist"

	// Read current configuration
	file, err := os.Open(configFile)
	if err != nil {
		return fmt.Errorf("failed to read %s: %w", configFile, err)
	}
	defer file.Close()

	var lines []string
	firstMirrorAdded := false
	scanner := bufio.NewScanner(file)

	// Add the fastest mirror at the top (uncommented)
	lines = append(lines, fmt.Sprintf("# FastestMirror: Added %s", time.Now().Format("2006-01-02 15:04:05")))
	lines = append(lines, fmt.Sprintf("Server = %s/$repo/os/$arch", strings.TrimSuffix(mirrorURL, "/")))
	lines = append(lines, "")
	firstMirrorAdded = true

	// Process existing lines, commenting out other Server entries
	for scanner.Scan() {
		line := scanner.Text()
		trimmed := strings.TrimSpace(line)

		// Comment out existing Server lines (but keep them for reference)
		if strings.HasPrefix(trimmed, "Server = ") && firstMirrorAdded {
			lines = append(lines, "#"+line)
		} else {
			lines = append(lines, line)
		}
	}

	if err := scanner.Err(); err != nil {
		return fmt.Errorf("error reading %s: %w", configFile, err)
	}

	// Write updated configuration
	return cm.writeLines(configFile, lines)
}

// copyFile copies a file from src to dst
func (cm *ConfigManager) copyFile(src, dst string) error {
	sourceFile, err := os.Open(src)
	if err != nil {
		return err
	}
	defer sourceFile.Close()

	destFile, err := os.Create(dst)
	if err != nil {
		return err
	}
	defer destFile.Close()

	_, err = io.Copy(destFile, sourceFile)
	if err != nil {
		return err
	}

	// Copy file permissions
	srcInfo, err := os.Stat(src)
	if err != nil {
		return err
	}

	return os.Chmod(dst, srcInfo.Mode())
}

// writeLines writes lines to a file
func (cm *ConfigManager) writeLines(filename string, lines []string) error {
	file, err := os.Create(filename)
	if err != nil {
		return err
	}
	defer file.Close()

	writer := bufio.NewWriter(file)
	for _, line := range lines {
		if _, err := writer.WriteString(line + "\n"); err != nil {
			return err
		}
	}

	return writer.Flush()
}

// RestoreBackup restores a configuration from backup
func (cm *ConfigManager) RestoreBackup(backupPath string) error {
	configFile := cm.DistroInfo.GetConfigFile()
	if configFile == "" {
		return fmt.Errorf("no configuration file defined for %s", cm.DistroInfo.Family)
	}

	return cm.copyFile(backupPath, configFile)
}