package scan_post

import (
	"context"
	"math"
	"sort"

	"haixun-backend/internal/library/authctx"
	app "haixun-backend/internal/library/errors"
	"haixun-backend/internal/library/errors/code"
	scanpostusecase "haixun-backend/internal/model/scan_post/domain/usecase"
	"haixun-backend/internal/svc"
	"haixun-backend/internal/types"

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

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

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

func (l *LookalikeLogic) Lookalike(req *types.LookalikeReq) (*types.LookalikeData, error) {
	actor, ok := authctx.ActorFromContext(l.ctx)
	if !ok {
		return nil, app.For(code.Auth).AuthUnauthorized("missing actor")
	}

	source, err := l.svcCtx.ScanPost.Get(l.ctx, actor.TenantID, actor.UID, req.BrandID, req.SourcePostID)
	if err != nil {
		return nil, err
	}
	if len(source.Embedding) == 0 {
		return &types.LookalikeData{List: nil}, nil
	}

	brandID := req.BrandID
	if brandID == "" {
		brandID = source.BrandID
	}

	limit := req.Limit
	if limit < 1 {
		limit = 10
	}
	if limit > 50 {
		limit = 50
	}

	candidates, err := l.svcCtx.ScanPost.List(l.ctx, scanpostusecase.ListRequest{
		TenantID: actor.TenantID,
		OwnerUID: actor.UID,
		BrandID:  brandID,
		Limit:    200,
	})
	if err != nil {
		return nil, err
	}

	type scored struct {
		post scanpostusecase.ScanPostSummary
		sim  float64
	}
	var scoredList []scored
	for _, c := range candidates {
		if c.ID == req.SourcePostID {
			continue
		}
		if len(c.Embedding) == 0 {
			continue
		}
		sim := cosineSimilarity(source.Embedding, c.Embedding)
		if sim < 0.3 {
			continue
		}
		scoredList = append(scoredList, scored{post: c, sim: sim})
	}

	sort.Slice(scoredList, func(i, j int) bool {
		return scoredList[i].sim > scoredList[j].sim
	})

	if len(scoredList) > limit {
		scoredList = scoredList[:limit]
	}

	out := make([]types.LookalikeItemData, 0, len(scoredList))
	for _, s := range scoredList {
		out = append(out, types.LookalikeItemData{
			PostID:              s.post.ID,
			AuthorID:            s.post.AuthorID,
			AuthorName:          s.post.Author,
			AuthorAvatar:        s.post.AuthorAvatar,
			Permalink:           s.post.Permalink,
			Text:                s.post.Text,
			PlacementScore:      s.post.PlacementScore,
			SemanticScore:       s.post.SemanticScore,
			EngagementPredicted: s.post.EngagementPredicted,
			AudienceQuality:     s.post.AudienceQualityScore,
			Similarity:          math.Round(s.sim*1000) / 1000,
		})
	}

	return &types.LookalikeData{List: out}, nil
}

func cosineSimilarity(a, b []float32) float64 {
	if len(a) == 0 || len(b) == 0 || len(a) != len(b) {
		return 0
	}
	var dot, na, nb float64
	for i := range a {
		dot += float64(a[i]) * float64(b[i])
		na += float64(a[i]) * float64(a[i])
		nb += float64(b[i]) * float64(b[i])
	}
	if na == 0 || nb == 0 {
		return 0
	}
	return dot / (math.Sqrt(na) * math.Sqrt(nb))
}