// 长文的自动摘要与自动封面：站主没填这两项时从正文派生——
// 摘要取正文开头的一段纯文本，封面取正文第一张图。
// 更新路径只在「新值与旧值都为空」时才生成，站主主动清空的要保得住。
package admin

import (
	"regexp"
	"strings"

	"oneblog/internal/model"
)

const autoSummaryLen = 110

var (
	mdImageRe   = regexp.MustCompile(`!\[[^\]]*\]\(([^)\s]+)[^)]*\)`)
	mdCodeFence = regexp.MustCompile("(?s)```.*?```")
	mdLinkRe    = regexp.MustCompile(`\[([^\]]*)\]\([^)]*\)`)
	mdHeadingRe = regexp.MustCompile(`(?m)^#{1,6}\s+.*$`) // 标题行整行不进摘要（与文章标题重复）
	mdNoiseRe   = regexp.MustCompile(`(?m)^([>\s*-]+|\d+\.\s)+`)
	mdEmphasis  = strings.NewReplacer("**", "", "__", "", "~~", "", "*", "", "_", "")
	wsRe        = regexp.MustCompile(`\s+`)
)

// autoMeta 按需填充 in.Summary / in.CoverURL。
// cur 为更新前的旧文章（新建时传 nil）。
func autoMeta(in *model.PostInput, cur *model.Post) {
	if in.Kind != model.KindLong || strings.TrimSpace(in.ContentMd) == "" {
		return
	}
	if strings.TrimSpace(in.Summary) == "" && (cur == nil || strings.TrimSpace(cur.Summary) == "") {
		in.Summary = summarizeMarkdown(in.ContentMd, autoSummaryLen)
	}
	if strings.TrimSpace(in.CoverURL) == "" && (cur == nil || strings.TrimSpace(cur.CoverURL) == "") {
		in.CoverURL = firstImage(in.ContentMd)
	}
}

// summarizeMarkdown 剥掉 markdown 语法后取正文开头一段纯文本
func summarizeMarkdown(md string, maxRunes int) string {
	s := mdCodeFence.ReplaceAllString(md, " ") // 代码块整段不进摘要
	s = mdHeadingRe.ReplaceAllString(s, " ")
	s = mdImageRe.ReplaceAllString(s, " ")
	s = mdLinkRe.ReplaceAllString(s, "$1")
	s = mdNoiseRe.ReplaceAllString(s, " ")
	s = mdEmphasis.Replace(s)
	s = strings.ReplaceAll(s, "`", "")
	s = wsRe.ReplaceAllString(s, " ")
	s = strings.TrimSpace(s)
	runes := []rune(s)
	if len(runes) > maxRunes {
		return string(runes[:maxRunes]) + "…"
	}
	return s
}

// firstImage 取正文第一张图片的地址（markdown 图；http/站内路径均可）
func firstImage(md string) string {
	m := mdImageRe.FindStringSubmatch(md)
	if m == nil {
		return ""
	}
	u := m[1]
	if strings.HasPrefix(u, "http://") || strings.HasPrefix(u, "https://") || strings.HasPrefix(u, "/uploads/") {
		return u
	}
	return ""
}