package outreach

import (
	"strings"
)

func NormalizeDraftText(text string) string {
	text = strings.ReplaceAll(text, "\r\n", "\n")
	text = strings.ReplaceAll(text, "\r", "\n")
	text = strings.TrimSpace(text)
	text = humanizeDraftLineBreaks(text)
	return trimDraftText(text)
}

func humanizeDraftLineBreaks(text string) string {
	if text == "" || strings.Contains(text, "\n") {
		return text
	}
	if len([]rune(text)) < 40 {
		return text
	}

	sentences := splitSentences(text)
	if len(sentences) <= 1 {
		return text
	}

	paragraphs := make([]string, 0, (len(sentences)+1)/2)
	for i := 0; i < len(sentences); {
		end := i + 2
		if end > len(sentences) {
			end = len(sentences)
		}
		paragraphs = append(paragraphs, strings.Join(sentences[i:end], ""))
		i = end
	}
	return strings.Join(paragraphs, "\n\n")
}

func splitSentences(text string) []string {
	runes := []rune(text)
	if len(runes) == 0 {
		return nil
	}
	out := make([]string, 0, 4)
	var current strings.Builder
	for i := 0; i < len(runes); i++ {
		ch := runes[i]
		current.WriteRune(ch)
		if !isSentenceEnd(ch) {
			continue
		}
		// Keep ellipsis / repeated punctuation attached to the same sentence.
		for i+1 < len(runes) && isSentenceEnd(runes[i+1]) {
			i++
			current.WriteRune(runes[i])
		}
		if sentence := strings.TrimSpace(current.String()); sentence != "" {
			out = append(out, sentence)
		}
		current.Reset()
	}
	if tail := strings.TrimSpace(current.String()); tail != "" {
		out = append(out, tail)
	}
	return out
}

func isSentenceEnd(ch rune) bool {
	switch ch {
	case '。', '！', '？', '!', '?', '…':
		return true
	default:
		return false
	}
}