// parse.go — Shared key=value payload parsing.
package protocol

import "strings"

// ParsePayload parses newline-separated key=value pairs into a map.
// Values are unescaped: \n → newline, \\ → backslash.
func ParsePayload(payload string) map[string]string {
	args := make(map[string]string)
	for _, line := range strings.Split(payload, "\n") {
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		idx := strings.Index(line, "=")
		if idx < 0 {
			continue
		}
		key := line[:idx]
		value := line[idx+1:]
		value = UnescapeValue(value)
		args[key] = value
	}
	return args
}

// UnescapeValue reverses wire-format escape sequences: \n → newline, \\ → backslash.
func UnescapeValue(s string) string {
	if !strings.ContainsRune(s, '\\') {
		return s
	}
	result := make([]byte, 0, len(s))
	for i := 0; i < len(s); i++ {
		if s[i] == '\\' && i+1 < len(s) {
			switch s[i+1] {
			case 'n':
				result = append(result, '\n')
				i++
				continue
			case '\\':
				result = append(result, '\\')
				i++
				continue
			}
		}
		result = append(result, s[i])
	}
	return string(result)
}