package cloudinit

import (
	"fmt"
	"log/slog"
	"os"
	"path/filepath"
	"strings"
)

// DefaultUpdateConfPath is where the update agent expects to find its config.
// Kept in sync with update/pkg/config.DefaultPath.
const DefaultUpdateConfPath = "/etc/kubesolo/update.conf"

// ApplyUpdates writes /etc/kubesolo/update.conf from the cloud-init
// updates: block. Called once per boot; idempotent (overwrites any existing
// file with the cloud-init values).
//
// If the updates: block is empty (all fields blank), the file is not
// written — preserves any hand-edited update.conf on systems that aren't
// managed via cloud-init.
func ApplyUpdates(cfg *Config, confPath string) error {
	if confPath == "" {
		confPath = DefaultUpdateConfPath
	}
	u := cfg.Updates
	if u.Server == "" && u.Channel == "" && u.MaintenanceWindow == "" && u.PubKey == "" {
		// Nothing to write — leave any existing file alone.
		return nil
	}

	if err := os.MkdirAll(filepath.Dir(confPath), 0o755); err != nil {
		return fmt.Errorf("creating dir for %s: %w", confPath, err)
	}

	var sb strings.Builder
	sb.WriteString("# Generated by KubeSolo OS cloud-init — edit this file or the\n")
	sb.WriteString("# cloud-init source YAML; subsequent first-boots will regenerate it.\n")
	if u.Server != "" {
		fmt.Fprintf(&sb, "server = %s\n", u.Server)
	}
	if u.Channel != "" {
		fmt.Fprintf(&sb, "channel = %s\n", u.Channel)
	}
	if u.MaintenanceWindow != "" {
		fmt.Fprintf(&sb, "maintenance_window = %s\n", u.MaintenanceWindow)
	}
	if u.PubKey != "" {
		fmt.Fprintf(&sb, "pubkey = %s\n", u.PubKey)
	}

	if err := os.WriteFile(confPath, []byte(sb.String()), 0o644); err != nil {
		return fmt.Errorf("writing %s: %w", confPath, err)
	}
	slog.Info("wrote update.conf", "path", confPath)
	return nil
}