package insightsapi

import (
	"context"
	"fmt"
	"sort"
	"time"

	"apps/backend/internal/middleware"
	"apps/backend/internal/module/growth/usecase"
	"apps/backend/internal/svc"
	"apps/backend/internal/types"

	"github.com/zeromicro/go-zero/core/logx"
)

type GetInsightsSummaryLogic struct {
	logx.Logger
	ctx    context.Context
	svcCtx *svc.ServiceContext
}

func NewGetInsightsSummaryLogic(ctx context.Context, svcCtx *svc.ServiceContext) *GetInsightsSummaryLogic {
	return &GetInsightsSummaryLogic{Logger: logx.WithContext(ctx), ctx: ctx, svcCtx: svcCtx}
}

func (l *GetInsightsSummaryLogic) GetInsightsSummary(req *types.InsightsSummaryReq) (*types.InsightsSummaryData, error) {
	uid, ok := middleware.UIDFrom(l.ctx)
	if !ok || uid <= 0 {
		return nil, fmt.Errorf("unauthorized")
	}
	if l.svcCtx.Studio == nil {
		return &types.InsightsSummaryData{Conclusion: "尚無創作資料", Suggestions: []string{"先同步已發貼文"}}, nil
	}
	posts, err := l.svcCtx.Studio.ListOwnPosts(l.ctx, uid, req.AccountId)
	if err != nil {
		return nil, err
	}
	months := req.Months
	if months <= 0 {
		months = 3
	}
	cutoff := time.Now().UTC().AddDate(0, -months, 0).UnixNano()
	type agg struct{ posts, views, likes, replies int }
	byMonth := map[string]*agg{}
	var totalV, totalL, totalR, n int
	var top []types.InsightsPostPublic
	for _, p := range posts {
		if p == nil {
			continue
		}
		ts := p.PublishedAt
		if ts > 0 && ts < cutoff {
			continue
		}
		n++
		totalV += p.ViewCount
		totalL += p.LikeCount
		totalR += p.ReplyCount
		mk := time.Unix(0, ts).UTC().Format("2006-01")
		if ts == 0 {
			mk = time.Now().UTC().Format("2006-01")
		}
		a := byMonth[mk]
		if a == nil {
			a = &agg{}
			byMonth[mk] = a
		}
		a.posts++
		a.views += p.ViewCount
		a.likes += p.LikeCount
		a.replies += p.ReplyCount
		eng := 0.0
		if p.ViewCount > 0 {
			eng = float64(p.LikeCount+p.ReplyCount) / float64(p.ViewCount)
		}
		prev := p.Text
		if len([]rune(prev)) > 80 {
			prev = string([]rune(prev)[:80]) + "…"
		}
		top = append(top, types.InsightsPostPublic{
			Id: p.ID, TextPreview: prev, PublishedAt: ts,
			ViewCount: p.ViewCount, LikeCount: p.LikeCount, ReplyCount: p.ReplyCount, EngRate: usecase.RoundRate(eng),
		})
	}
	sort.Slice(top, func(i, j int) bool { return top[i].EngRate > top[j].EngRate })
	if len(top) > 5 {
		top = top[:5]
	}
	avgEng := 0.0
	if totalV > 0 {
		avgEng = float64(totalL+totalR) / float64(totalV)
	}
	var buckets []types.InsightsMonthBucket
	for mk, a := range byMonth {
		e := 0.0
		if a.views > 0 {
			e = float64(a.likes+a.replies) / float64(a.views)
		}
		buckets = append(buckets, types.InsightsMonthBucket{
			MonthKey: mk, Posts: a.posts, Views: a.views, Likes: a.likes, Replies: a.replies, AvgEngRate: usecase.RoundRate(e),
		})
	}
	sort.Slice(buckets, func(i, j int) bool { return buckets[i].MonthKey < buckets[j].MonthKey })
	conclusion := fmt.Sprintf("近 %d 個月同步貼文 %d 則，平均互動率 %.2f%%。", months, n, avgEng*100)
	sugs := []string{"維持高互動題材節奏", "把表現佳貼文結構拿去仿寫"}
	if n == 0 {
		conclusion = "尚無足夠已同步貼文"
		sugs = []string{"到創作 → 我的貼文按同步", "連好 Threads 帳號後再看成效"}
	} else if avgEng < 0.02 {
		sugs = append([]string{"互動率偏低：可加強開頭鉤子與提問 CTA"}, sugs...)
	}
	// also feed benchmark
	if n > 0 {
		_ = l.svcCtx.Growth.ContributeBenchmark(l.ctx, uid, "general", avgEng, float64(totalV)/float64(n))
	}
	return &types.InsightsSummaryData{
		AccountId: req.AccountId, PostCount: n, TotalViews: totalV, TotalLikes: totalL, TotalReplies: totalR,
		AvgEngRate: usecase.RoundRate(avgEng), TopPosts: top, MonthBuckets: buckets,
		Conclusion: conclusion, Suggestions: sugs,
	}, nil
}