// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
// SPDX-License-Identifier: GPL-3.0-or-later

//go:build !cgo

package datetime

import (
	"strconv"
	"strings"
	"time"
)

// format is a C-locale strftime subset for builds without cgo, such as the
// statically linked Tentacle packages that only validate settings. The reader
// itself is built with cgo and uses the locale-aware implementation.
func format(now time.Time, spec string) string {
	var out strings.Builder
	for index := 0; index < len(spec); index++ {
		if spec[index] != '%' || index+1 == len(spec) {
			out.WriteByte(spec[index])
			continue
		}
		index++
		pad := true
		if spec[index] == '-' && index+1 < len(spec) {
			pad = false
			index++
		}
		two := func(value int) string {
			if pad && value < 10 {
				return "0" + strconv.Itoa(value)
			}
			return strconv.Itoa(value)
		}
		switch spec[index] {
		case 'H':
			out.WriteString(two(now.Hour()))
		case 'I':
			hour := now.Hour() % 12
			if hour == 0 {
				hour = 12
			}
			out.WriteString(two(hour))
		case 'M':
			out.WriteString(two(now.Minute()))
		case 'S':
			out.WriteString(two(now.Second()))
		case 'p':
			out.WriteString(now.Format("PM"))
		case 'X':
			out.WriteString(now.Format("15:04:05"))
		case 'x':
			out.WriteString(now.Format("01/02/06"))
		case 'd':
			out.WriteString(two(now.Day()))
		case 'm':
			out.WriteString(two(int(now.Month())))
		case 'Y':
			out.WriteString(strconv.Itoa(now.Year()))
		case 'y':
			out.WriteString(now.Format("06"))
		case 'A':
			out.WriteString(now.Weekday().String())
		case 'a':
			out.WriteString(now.Weekday().String()[:3])
		case 'B':
			out.WriteString(now.Month().String())
		case 'b':
			out.WriteString(now.Month().String()[:3])
		case '%':
			out.WriteByte('%')
		default:
			out.WriteByte('%')
			out.WriteByte(spec[index])
		}
	}
	return out.String()
}