package distros

import (
	"bufio"
	"bytes"
	"errors"
	"fmt"
	"net/http"
	"regexp"

	"github.com/rs/zerolog/log"
	"libguestfs.org/guestfs"

	"git.csclub.uwaterloo.ca/cloud/cloudbuild/pkg/config"
)

type DebianTemplateManager struct {
	TemplateManager
}

// NewDebianTemplateManager returns a DebianTemplateManager with the given
// config values.
func NewDebianTemplateManager(cfg *config.Config) *DebianTemplateManager {
	logger := log.With().Str("distro", "debian").Logger()
	debianTemplateManager := DebianTemplateManager{
		TemplateManager{
			cfg:    cfg,
			logger: &logger,
			impl:   nil,
		},
	}
	debianTemplateManager.TemplateManager.impl = &debianTemplateManager
	return &debianTemplateManager
}

func (mgr *DebianTemplateManager) GetLatestVersion() (version string, codename string, err error) {
	// We're only interested in the major version (integer part)
	versionPattern := regexp.MustCompile(`^Version: (\d+)(?:\.\d+)?$`)
	codenamePattern := regexp.MustCompile("^Codename: ([a-z-]+)$")
	resp, err := http.Get("https://mirror.csclub.uwaterloo.ca/debian/dists/stable/InRelease")
	if err != nil {
		return
	}
	defer resp.Body.Close()
	scanner := bufio.NewScanner(resp.Body)
	for scanner.Scan() {
		if version == "" {
			submatches := versionPattern.FindStringSubmatch(scanner.Text())
			if submatches != nil {
				version = submatches[1]
			}
		}
		if codename == "" {
			submatches := codenamePattern.FindStringSubmatch(scanner.Text())
			if submatches != nil {
				codename = submatches[1]
			}
		}
		if version != "" && codename != "" {
			break
		}
	}
	if version == "" {
		err = errors.New("Could not determine latest version of Debian")
	}
	return
}

func (mgr *DebianTemplateManager) DownloadTemplate(version, codename string) (path string, err error) {
	filename := fmt.Sprintf("debian-%s-genericcloud-amd64.qcow2", version)
	url := fmt.Sprintf("https://cloud.debian.org/images/cloud/%s/latest/%s", codename, filename)
	return mgr.DownloadTemplateGeneric(filename, url)
}

func (mgr *DebianTemplateManager) replaceFailsafeMirrorsInCloudCfg(handle *guestfs.Guestfs) error {
	// In Debian 12 (bookworm), /etc/cloud/cloud.cfg has the following snippet:
	//
	// system_info:
	//   package_mirrors:
	//     - arches: [default]
	//       failsafe:
	//         primary: https://deb.debian.org/debian
	//         security: https://deb.debian.org/debian-security
	//
	// Since we can't override the system_info settings, we need to overwrite this file.
	filePaths := []string{"/etc/cloud/cloud.cfg"}
	// To be safe, we check other config files under /etc/cloud/cloud.cfg.d as well.
	extraFilePaths, err := handle.Glob_expand("/etc/cloud/cloud.cfg.d/*.cfg", nil)
	if err != nil {
		return fmt.Errorf("Could not expand glob /etc/cloud/cloud.cfg.d/*.cfg: %w", err)
	}
	filePaths = append(filePaths, extraFilePaths...)
	debMirrorUrlRegex := regexp.MustCompile(`https?://deb\.debian\.org`)
	replacement := []byte("http://" + mgr.cfg.MirrorHost)
	for _, filePath := range filePaths {
		mgr.logger.Debug().Str("file", filePath).Msg("Checking for deb.debian.org URLs")
		content, err := handle.Read_file(filePath)
		if err != nil {
			return fmt.Errorf("Could not read %s: %w", filePath, err)
		}
		newContent := debMirrorUrlRegex.ReplaceAll(content, replacement)
		if bytes.Equal(content, newContent) {
			continue
		}
		mgr.logger.Debug().Str("file", filePath).Msg("Replacing deb.debian.org URLs")
		err = handle.Write(filePath, newContent)
		if err != nil {
			return fmt.Errorf("Could not write to %s: %w", filePath, err)
		}
	}
	return nil
}

func (mgr *DebianTemplateManager) CommandToUpdatePackageCache() []string {
	return debianCommandToUpdatePackageCache()
}

func (mgr *DebianTemplateManager) PerformDistroSpecificModifications(handle *guestfs.Guestfs) error {
	if err := mgr.replaceFailsafeMirrorsInCloudCfg(handle); err != nil {
		return err
	}
	if err := mgr.replaceDebianMirrorUrls(handle); err != nil {
		return err
	}
	return nil
}