package fastmirror

import (
	"bufio"
	_ "embed"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"regexp"
	"strings"

	cp "github.com/otiai10/copy"
)

func findSourcesFilePath() (string, error) {
	const sourcesListPath = "/etc/apt/sources.list"
	const sourcesListDPath = "/etc/apt/sources.list.d/"
	if isUbuntuSourcesFile(sourcesListPath) {
		log.Printf("Found Ubuntu sources file: %s", sourcesListPath)
		return sourcesListPath, nil
	}

	files, err := os.ReadDir(sourcesListDPath)
	if err != nil {
		return "", fmt.Errorf("failed to read directory %s: %v", sourcesListDPath, err)
	}

	for _, file := range files {
		if file.IsDir() {
			continue
		}

		filePath := filepath.Join(sourcesListDPath, file.Name())
		if isUbuntuSourcesFile(filePath) {
			log.Printf("Found Ubuntu sources file: %s", filePath)
			return filePath, nil
		}
	}
	return "", fmt.Errorf("no Ubuntu sources file found")
}

var ubuntuMirrorURLRegex = regexp.MustCompile(`http://((?P<countrycode>[a-z]{2})\.)?(archive|ports)\.ubuntu\.com/(?P<path>.*)`)

func findMirrorURLInFile(filePath string) (string, error) {
	fileContent, err := os.ReadFile(filePath)
	if err != nil {
		return "", fmt.Errorf("failed to read file %s: %v", filePath, err)
	}
	match := ubuntuMirrorURLRegex.FindString(string(fileContent))
	if match != "" {
		return match, nil
	}
	return "", fmt.Errorf("no URL found in file %s", filePath)
}

func isUbuntuSourcesFile(filePath string) bool {
	match, err := findMirrorURLInFile(filePath)
	if err != nil {
		log.Printf("Failed to find OEM mirror URL in file %s: %v", filePath, err)
		return false
	}
	log.Printf("Found OEM mirror URL in file %s: %s", filePath, match)
	return true
}

func createBackup(filePath string) error {
	backupPath := filePath + ".bak"
	if _, err := os.Stat(backupPath); err == nil {
		return fmt.Errorf("backup file %s already exists", backupPath)
	}
	// copy the file to the backup file
	if err := cp.Copy(filePath, backupPath); err != nil {
		return fmt.Errorf("failed to create backup file %s: %v", backupPath, err)
	}
	log.Printf("Created backup: %s", backupPath)
	return nil
}

func extractSuites(filePath string) ([]string, error) {
	content, err := os.ReadFile(filePath)
	if err != nil {
		return nil, fmt.Errorf("failed to read file %s: %v", filePath, err)
	}

	var suites []string
	scanner := bufio.NewScanner(strings.NewReader(string(content)))

	isModernFormat := false
	for scanner.Scan() {
		line := scanner.Text()
		if strings.HasPrefix(line, "Types:") {
			isModernFormat = true
			break
		}
	}

	scanner = bufio.NewScanner(strings.NewReader(string(content)))
	if isModernFormat {
		for scanner.Scan() {
			line := scanner.Text()
			if strings.HasPrefix(line, "Suites:") {
				parts := strings.Fields(line)
				suites = append(suites, parts[1:]...)
			}
		}
	} else {
		for scanner.Scan() {
			line := scanner.Text()
			if strings.HasPrefix(line, "deb ") || strings.HasPrefix(line, "deb-src ") {
				parts := strings.Fields(line)
				if len(parts) >= 4 {
					suites = append(suites, parts[3])
				}
			}
		}
	}

	if err := scanner.Err(); err != nil {
		return nil, fmt.Errorf("failed to scan file %s: %v", filePath, err)
	}
	return suites, nil
}

func updateSourcesFile(filePath, oldMirrorURL, newMirrorURL string) error {
	file, err := os.Open(filePath)
	if err != nil {
		return fmt.Errorf("failed to open sources file %s: %v", filePath, err)
	}
	file.Close()
	contentBytes, err := os.ReadFile(filePath)
	if err != nil {
		return fmt.Errorf("failed to read sources file %s: %v", filePath, err)
	}

	log.Printf("update: replacing %s with %s in %s", oldMirrorURL, newMirrorURL, filePath)
	// replace old mirror URL with new mirror URL
	content := string(contentBytes)
	content = strings.ReplaceAll(content, oldMirrorURL, newMirrorURL)

	if err := os.WriteFile(filePath, []byte(content), 0644); err != nil {
		return fmt.Errorf("failed to write sources file %s: %v", filePath, err)
	}
	log.Printf("Updated sources file: %s", filePath)
	return nil
}