package users

import (
	"context"
	"fmt"
	"strings"

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

const ModuleName = "users"

type Config struct {
	// Execute controls whether system commands actually run. Disabled in dev.
	Execute bool
	// DefaultShell used when creating users.
	DefaultShell string
	// CreateHome creates a home directory for new users.
	CreateHome bool
}

type Module struct {
	cfg Config
}

func New(cfg Config) *Module {
	if cfg.DefaultShell == "" {
		cfg.DefaultShell = "/usr/sbin/nologin"
	}
	return &Module{cfg: cfg}
}

func (m *Module) Name() string {
	return ModuleName
}

func (m *Module) IsDirty(ctx context.Context, database *db.DB) (bool, error) {
	return database.IsDirty(ModuleName)
}

func (m *Module) Apply(ctx context.Context, database *db.DB) error {
	deleted, err := database.ListDeletedUsers()
	if err != nil {
		return err
	}
	for _, username := range deleted {
		if err := m.deleteUser(ctx, username); err != nil {
			return err
		}
		if err := database.ClearDeletedUser(username); err != nil {
			return err
		}
	}

	usersList, err := database.ListUsers()
	if err != nil {
		return err
	}
	for _, user := range usersList {
		if err := m.reconcileUser(ctx, database, user); err != nil {
			return err
		}
	}

	message := fmt.Sprintf("reconciled %d user(s), %d deletion(s)", len(usersList), len(deleted))
	if err := database.AppendApplyLog(ModuleName, message, true); err != nil {
		return err
	}
	return database.ClearDirty(ModuleName)
}

func (m *Module) reconcileUser(ctx context.Context, database *db.DB, user db.User) error {
	if err := system.ValidateUsername(user.Username); err != nil {
		return err
	}

	exists := m.cfg.Execute && system.UserExists(ctx, user.Username)

	if !m.cfg.Execute {
		// In dev mode we do not touch the system; just clear pending secrets
		// so they are not retained indefinitely.
		if user.PendingPassword != "" {
			return database.ClearUserPendingPassword(user.ID)
		}
		return nil
	}

	groups := sanitizeGroups(user.Groups)

	if !exists {
		args := []string{"-s", m.cfg.DefaultShell}
		if m.cfg.CreateHome {
			args = append(args, "-m")
		} else {
			args = append(args, "-M")
		}
		if len(groups) > 0 {
			args = append(args, "-G", strings.Join(groups, ","))
		}
		args = append(args, user.Username)
		if err := m.run(ctx, "useradd", args...); err != nil {
			return err
		}
	} else {
		args := []string{"-G", strings.Join(groups, ",")}
		args = append(args, user.Username)
		if err := m.run(ctx, "usermod", args...); err != nil {
			return err
		}
	}

	if user.Disabled {
		if err := m.run(ctx, "usermod", "-L", user.Username); err != nil {
			return err
		}
	} else {
		// Unlock; ignore error when there is nothing to unlock.
		_ = m.run(ctx, "usermod", "-U", user.Username)
	}

	if err := m.applySMB(ctx, database, user); err != nil {
		return err
	}

	return nil
}

func (m *Module) applySMB(ctx context.Context, database *db.DB, user db.User) error {
	if user.SMBEnabled {
		if user.PendingPassword != "" {
			// smbpasswd -a -s reads the new password twice from stdin.
			input := user.PendingPassword + "\n" + user.PendingPassword + "\n"
			stdout, stderr, err := system.RunWithInput(ctx, input, "smbpasswd", "-a", "-s", user.Username)
			if err != nil {
				return fmt.Errorf("smbpasswd -a for %s: %w (stdout=%q stderr=%q)", user.Username, err, stdout, stderr)
			}
			if err := database.ClearUserPendingPassword(user.ID); err != nil {
				return err
			}
		}
		// Ensure the smb account is enabled.
		_ = m.run(ctx, "smbpasswd", "-e", user.Username)
	} else {
		// Disable SMB access; ignore error when the account is not present.
		_ = m.run(ctx, "smbpasswd", "-x", user.Username)
	}
	return nil
}

func (m *Module) deleteUser(ctx context.Context, username string) error {
	if err := system.ValidateUsername(username); err != nil {
		return err
	}
	if !m.cfg.Execute {
		return nil
	}
	// Remove SMB entry first (ignore if absent), then the system user.
	_ = m.run(ctx, "smbpasswd", "-x", username)
	if system.UserExists(ctx, username) {
		if err := m.run(ctx, "userdel", username); err != nil {
			return err
		}
	}
	return nil
}

func (m *Module) run(ctx context.Context, name string, args ...string) error {
	stdout, stderr, err := system.Run(ctx, name, args...)
	if err != nil {
		return fmt.Errorf("%s %s: %w (stdout=%q stderr=%q)", name, strings.Join(args, " "), err, stdout, stderr)
	}
	return nil
}

func sanitizeGroups(groups []string) []string {
	out := make([]string, 0, len(groups))
	for _, g := range groups {
		g = strings.TrimSpace(g)
		if g != "" {
			out = append(out, g)
		}
	}
	return out
}