// Package config parses /etc/kubesolo/update.conf — the persistent
// configuration for the update agent. Each line is "key = value"; blank
// lines and "#"-prefixed comments are ignored. Unknown keys are tolerated
// (forward compatibility).
//
// Example:
//
//	# Where to look for updates
//	server = https://updates.kubesolo.example.com
//	channel = stable
//
//	# Only apply between 03:00 and 05:00 local time
//	maintenance_window = 03:00-05:00
//
//	pubkey = /etc/kubesolo/update-pubkey.hex
//
// The file is populated on first boot by cloud-init (see the cloud-init
// updates: block) and can be hand-edited afterwards.
package config

import (
	"bufio"
	"fmt"
	"os"
	"strings"
)

// DefaultPath is where update.conf lives on a live system.
const DefaultPath = "/etc/kubesolo/update.conf"

// Config holds the parsed update.conf values. Empty fields mean "not set" —
// the caller's defaults apply.
type Config struct {
	Server            string
	Channel           string
	MaintenanceWindow string
	PubKey            string
}

// Load reads and parses update.conf. A missing file returns an empty Config
// (not an error) — fresh systems before cloud-init has run.
func Load(path string) (*Config, error) {
	f, err := os.Open(path)
	if err != nil {
		if os.IsNotExist(err) {
			return &Config{}, nil
		}
		return nil, fmt.Errorf("open %s: %w", path, err)
	}
	defer f.Close()

	c := &Config{}
	scanner := bufio.NewScanner(f)
	lineNo := 0
	for scanner.Scan() {
		lineNo++
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}
		eq := strings.IndexByte(line, '=')
		if eq < 0 {
			return nil, fmt.Errorf("%s:%d: missing '=' in line: %q", path, lineNo, line)
		}
		key := strings.TrimSpace(line[:eq])
		value := strings.TrimSpace(line[eq+1:])
		switch key {
		case "server":
			c.Server = value
		case "channel":
			c.Channel = value
		case "maintenance_window":
			c.MaintenanceWindow = value
		case "pubkey":
			c.PubKey = value
		}
		// Unknown keys are silently ignored for forward compatibility.
	}
	if err := scanner.Err(); err != nil {
		return nil, fmt.Errorf("read %s: %w", path, err)
	}
	return c, nil
}