thread-master/backend/internal/library/viral/analyze_viral.go

package viral

import (
	"encoding/json"
	"fmt"
	"strings"
)

type ViralAnalysis struct {
	StoryHook        string   `json:"storyHook"`
	NarrativeBeat    string   `json:"narrativeBeat"`
	EmotionalCore    string   `json:"emotionalCore"`
	SceneSeed        string   `json:"sceneSeed"`
	AuthenticityCues []string `json:"authenticityCues"`
	WhatToAvoid      string   `json:"whatToAvoid"`

	// Legacy fields kept for backward-compatible parsing.
	HookPattern         string   `json:"hookPattern"`
	StructurePattern    string   `json:"structurePattern"`
	EmotionalTrigger    string   `json:"emotionalTrigger"`
	ReplicationStrategy string   `json:"replicationStrategy"`
	KeyTakeaways        []string `json:"keyTakeaways"`
}

type AnalyzeViralInput struct {
	PostText   string
	AuthorName string
	LikeCount  int
	ReplyCount int
	SearchTag  string
	TopicLabel string
	TopicBrief string
	Persona    string
}

func BuildAnalyzeViralSystemPrompt() string {
	return strings.TrimSpace(`你是 Threads 敘事分析師。拆解這篇貼文為什麼讓人想看完、怎麼寫出同樣的故事感（不是抄句型）。

只回傳 JSON（繁體中文）：
- storyHook：讓人停下滑動的開場力量（描述手法，不要給可照抄的句子）
- narrativeBeat：故事怎麼推進（經歷/轉折/感受，不是段落模板）
- emotionalCore：核心情緒是什麼
- sceneSeed：一個值得借鑑的「具體場景種子」（時間/地點/動作，供啟發勿照搬）
- authenticityCues：3～5 個讓它像真人的小細節（口語、坦白、不完美、具體細節等）
- whatToAvoid：若照搬哪些寫法會立刻變成 AI 複製文`)
}

func BuildAnalyzeViralUserPrompt(in AnalyzeViralInput) string {
	var b strings.Builder
	b.WriteString("主題：")
	b.WriteString(strings.TrimSpace(in.TopicLabel))
	b.WriteString("\n")
	if brief := strings.TrimSpace(in.TopicBrief); brief != "" {
		b.WriteString("Brief：")
		b.WriteString(brief)
		b.WriteString("\n")
	}
	if tag := strings.TrimSpace(in.SearchTag); tag != "" {
		b.WriteString("搜尋標籤：")
		b.WriteString(tag)
		b.WriteString("\n")
	}
	author := strings.TrimSpace(in.AuthorName)
	if author == "" {
		author = "匿名"
	}
	b.WriteString(fmt.Sprintf("\n作者 @%s · %d 讚 · %d 留言\n", author, in.LikeCount, in.ReplyCount))
	b.WriteString("\n貼文：\n")
	b.WriteString(strings.TrimSpace(in.PostText))
	return b.String()
}

func ParseAnalyzeViralOutput(raw string) (ViralAnalysis, error) {
	payload, err := extractCopyMapJSON(raw)
	if err != nil {
		return ViralAnalysis{}, err
	}
	var out ViralAnalysis
	if err := json.Unmarshal(payload, &out); err != nil {
		return ViralAnalysis{}, fmt.Errorf("parse viral analysis: %w", err)
	}
	if strings.TrimSpace(out.StoryHook) == "" &&
		strings.TrimSpace(out.NarrativeBeat) == "" &&
		strings.TrimSpace(out.HookPattern) == "" &&
		strings.TrimSpace(out.StructurePattern) == "" {
		return ViralAnalysis{}, fmt.Errorf("viral analysis missing content")
	}
	return out, nil
}

func FormatAnalysisForReplicate(analysis ViralAnalysis) string {
	var b strings.Builder
	if hook := firstNonEmpty(analysis.StoryHook, analysis.HookPattern); hook != "" {
		b.WriteString("故事開場力量：")
		b.WriteString(hook)
		b.WriteString("\n")
	}
	if beat := firstNonEmpty(analysis.NarrativeBeat, analysis.StructurePattern); beat != "" {
		b.WriteString("敘事推進：")
		b.WriteString(beat)
		b.WriteString("\n")
	}
	if emotion := firstNonEmpty(analysis.EmotionalCore, analysis.EmotionalTrigger); emotion != "" {
		b.WriteString("核心情緒：")
		b.WriteString(emotion)
		b.WriteString("\n")
	}
	if scene := strings.TrimSpace(analysis.SceneSeed); scene != "" {
		b.WriteString("場景種子（啟發用，勿照搬）：")
		b.WriteString(scene)
		b.WriteString("\n")
	}
	cues := analysis.AuthenticityCues
	if len(cues) == 0 {
		cues = analysis.KeyTakeaways
	}
	if len(cues) > 0 {
		b.WriteString("真人質感線索：")
		b.WriteString(strings.Join(cues, "；"))
		b.WriteString("\n")
	}
	if avoid := firstNonEmpty(analysis.WhatToAvoid, analysis.ReplicationStrategy); avoid != "" {
		b.WriteString("避免變成複製文：")
		b.WriteString(avoid)
	}
	return strings.TrimSpace(b.String())
}

func firstNonEmpty(values ...string) string {
	for _, value := range values {
		if trimmed := strings.TrimSpace(value); trimmed != "" {
			return trimmed
		}
	}
	return ""
}