package text

import (
	"strings"
	"unicode/utf8"
)

func CleanMOTD(s string) string {
	if s == "" {
		return ""
	}

	s = strings.ReplaceAll(s, "\r\n", "\n")
	s = strings.ReplaceAll(s, "\r", "\n")
	s = stripColorCodes(s)
	s = stripControl(s)
	s = normalizeSpacesKeepNewlines(s)
	return strings.TrimSpace(s)
}

func stripColorCodes(s string) string {
	var b strings.Builder
	b.Grow(len(s))

	for i := 0; i < len(s); {
		r, size := utf8.DecodeRuneInString(s[i:])
		if r == utf8.RuneError && size == 1 {
			i++
			continue
		}

		if r == '§' || r == '&' {
			if i+2 < len(s) && (s[i] == '§' || s[i] == '&') && (s[i+1] == 'x' || s[i+1] == 'X') {
				j := i + 2
				ok := true
				for k := 0; k < 6; k++ {
					if j+2 >= len(s) {
						ok = false
						break
					}
					if s[j] != s[i] {
						ok = false
						break
					}
					c := s[j+1]
					if !isHex(c) {
						ok = false
						break
					}
					j += 2
				}
				if ok {
					i = j
					continue
				}
			}

			i += size
			if i < len(s) {
				_, nextSize := utf8.DecodeRuneInString(s[i:])
				i += nextSize
			}
			continue
		}

		b.WriteRune(r)
		i += size
	}

	return b.String()
}

func isHex(c byte) bool {
	return (c >= '0' && c <= '9') ||
		(c >= 'a' && c <= 'f') ||
		(c >= 'A' && c <= 'F')
}

func stripControl(s string) string {
	var b strings.Builder
	b.Grow(len(s))

	for _, r := range s {
		if r == '\n' || r == '\t' {
			b.WriteRune(r)
			continue
		}
		if r < 32 || r == 127 {
			continue
		}
		b.WriteRune(r)
	}
	return b.String()
}

func normalizeSpacesKeepNewlines(s string) string {
	lines := strings.Split(s, "\n")
	for i := range lines {
		lines[i] = strings.Join(strings.Fields(lines[i]), " ")
	}

	out := strings.Join(lines, "\n")
	out = strings.Trim(out, "\n")

	for strings.Contains(out, "\n\n\n") {
		out = strings.ReplaceAll(out, "\n\n\n", "\n\n")
	}
	return out
}