package usecase

import (
	"context"
	"errors"
	"fmt"

	"apps/backend/internal/module/radar/domain"
)

// TodayStats is the high/mid/low count block for the today page.
type TodayStats struct {
	Total int
	High  int
	Mid   int
	Low   int
}

// TodayOpportunity is one card on the today page (opp + optional default reply).
type TodayOpportunity struct {
	Opportunity  *domain.Opportunity
	DefaultReply *domain.ReplyVariant
}

// TodayResult powers GET /radar/today.
type TodayResult struct {
	Stats          TodayStats
	High           []TodayOpportunity
	Mid            []TodayOpportunity
	Low            []TodayOpportunity
	TruncatedCount int
	LastSweptAt    int64
	EmptyReason    string
	EmptyHint      string
}

// todayListStatuses：今日名單含可操作與已處理，排除 rejected／judging（T545）。
var todayListStatuses = []string{domain.OppQualified, domain.OppAccepted, domain.OppDismissed}

func (s *Service) GetToday(ctx context.Context, ownerUID int64) (*TodayResult, error) {
	if ownerUID <= 0 {
		return nil, fmt.Errorf("%w: owner_uid required", domain.ErrValidation)
	}
	start, end := domain.UTCDayBounds(domain.NowNano())

	// Empty-state diagnostics：只有「真的沒建檔」才算 no_profile，其他 DB 錯誤要往上丟。
	_, profileErr := s.Repo.GetServiceProfile(ctx, ownerUID)
	noProfile := errors.Is(profileErr, domain.ErrNotFound)
	if profileErr != nil && !noProfile {
		return nil, profileErr
	}
	watches, _, err := s.Repo.ListWatches(ctx, ownerUID, domain.WatchListFilter{Page: 1, PageSize: 50})
	if err != nil {
		return nil, err
	}
	active, err := s.Repo.ListActiveWatches(ctx, ownerUID)
	if err != nil {
		return nil, err
	}
	var lastSwept int64
	for _, w := range watches {
		if w.LastSweptAt > lastSwept {
			lastSwept = w.LastSweptAt
		}
	}

	list, _, err := s.Repo.ListOpportunities(ctx, ownerUID, domain.OpportunityListFilter{
		Statuses:    todayListStatuses,
		CreatedFrom: start,
		CreatedTo:   end,
		Page:        1,
		PageSize:    100,
	})
	if err != nil {
		return nil, err
	}

	high, mid, low := []TodayOpportunity{}, []TodayOpportunity{}, []TodayOpportunity{}
	for _, o := range list {
		card := TodayOpportunity{Opportunity: o}
		if replies, rerr := s.Repo.ListReplies(ctx, ownerUID, o.ID); rerr == nil {
			for _, r := range replies {
				if r.Variant == domain.ReplyPublicComment {
					card.DefaultReply = r
					break
				}
			}
		}
		switch o.IntentBand {
		case domain.BandHigh:
			high = append(high, card)
		case domain.BandMid:
			mid = append(mid, card)
		default:
			low = append(low, card)
		}
	}
	total := len(high) + len(mid) + len(low)

	// truncated from today's sweeps
	sweeps, _, _ := s.Repo.ListSweeps(ctx, ownerUID, domain.SweepListFilter{Page: 1, PageSize: 20})
	trunc := 0
	var latestFail string
	for _, sw := range sweeps {
		if sw.StartedAt >= start && sw.StartedAt < end {
			trunc += sw.TruncatedCount
			if sw.FailedReason != "" {
				latestFail = sw.FailedReason
			}
		}
	}

	out := &TodayResult{
		Stats:          TodayStats{Total: total, High: len(high), Mid: len(mid), Low: len(low)},
		High:           high,
		Mid:            mid,
		Low:            low,
		TruncatedCount: trunc,
		LastSweptAt:    lastSwept,
	}
	if total == 0 {
		out.EmptyReason, out.EmptyHint = emptyReason(noProfile, len(watches), len(active), lastSwept, latestFail, start)
	}
	return out, nil
}

func emptyReason(noProfile bool, watchCount, activeCount int, lastSwept int64, fail string, dayStart int64) (reason, hint string) {
	if noProfile {
		return "no_profile", "先完成服務檔案，雷達才能判定適不適合你的服務。"
	}
	if watchCount == 0 {
		return "no_watch", "建立至少一組關鍵字訂閱，明天早晨就會開始巡。"
	}
	if activeCount == 0 {
		return "all_watches_paused", "目前沒有啟用中的訂閱。恢復一組訂閱後才會繼續巡。"
	}
	if fail != "" {
		return "sweep_failed", fail
	}
	if lastSwept < dayStart {
		return "not_swept_yet", "今日巡檢還沒跑完（每日 UTC 22:00 開始）。也可在訂閱頁手動觸發。"
	}
	return "no_hit", "這輪有巡但沒有符合的商機。可放寬關鍵字或檢查排除詞是否太嚴。"
}