package importer

import (
	"bufio"
	"context"
	"os"
	"sort"
	"strconv"
	"strings"

	"github.com/darroyo/nasctl/internal/db"
	"github.com/darroyo/nasctl/internal/system"
)

const (
	UserMinUID = 1000
	UserMaxUID = 60000
)

var excludedUsernames = map[string]bool{
	"nobody":   true,
	"nogroup":  true,
	"sshd":     true,
	"systemd":  true,
	"messagebus": true,
	"polkitd":  true,
}

func ImportSystemUsers(ctx context.Context, adminUsername string) ([]db.User, error) {
	passwdMap, err := readPasswd()
	if err != nil {
		return nil, err
	}

	groupMap, err := readGroups()
	if err != nil {
		return nil, err
	}

	smbUsers, err := listSMBUsers(ctx)
	if err != nil {
		smbUsers = map[string]bool{}
	}

	var users []db.User
	for username, uid := range passwdMap {
		if uid < UserMinUID || uid > UserMaxUID {
			continue
		}
		if excludedUsernames[username] {
			continue
		}
		if username == adminUsername {
			continue
		}
		users = append(users, db.User{
			Username:   username,
			Groups:     groupMap[username],
			SMBEnabled: smbUsers[username],
			Disabled:   false,
		})
	}

	sort.Slice(users, func(i, j int) bool {
		return users[i].Username < users[j].Username
	})

	return users, nil
}

func readPasswd() (map[string]int, error) {
	f, err := os.Open("/etc/passwd")
	if err != nil {
		return nil, err
	}
	defer f.Close()

	result := make(map[string]int)
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		parts := strings.Split(line, ":")
		if len(parts) < 3 {
			continue
		}
		username := parts[0]
		uid, err := strconv.Atoi(parts[2])
		if err != nil {
			continue
		}
		result[username] = uid
	}
	if err := scanner.Err(); err != nil {
		return nil, err
	}
	return result, nil
}

func readGroups() (map[string][]string, error) {
	f, err := os.Open("/etc/group")
	if err != nil {
		return nil, err
	}
	defer f.Close()

	result := make(map[string][]string)
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		parts := strings.Split(line, ":")
		if len(parts) < 4 {
			continue
		}
		membersStr := strings.TrimSpace(parts[3])
		if membersStr == "" {
			continue
		}
		for _, member := range strings.Split(membersStr, ",") {
			member = strings.TrimSpace(member)
			if member != "" {
				result[member] = append(result[member], parts[0])
			}
		}
	}
	if err := scanner.Err(); err != nil {
		return nil, err
	}
	return result, nil
}

func listSMBUsers(ctx context.Context) (map[string]bool, error) {
	stdout, _, err := system.Run(ctx, "pdbedit", "-L")
	if err != nil {
		return map[string]bool{}, nil
	}
	result := make(map[string]bool)
	for _, line := range strings.Split(stdout, "\n") {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		parts := strings.SplitN(line, ":", 2)
		if len(parts) < 1 {
			continue
		}
		result[parts[0]] = true
	}
	return result, nil
}