package tender

import (
	"context"
	"strings"

	"tm/internal/company"
)

const recommendationResolveBatchSize = 100

type recommendationPageResult struct {
	items []rankedRecommendedTender
	total int64
}

func (s *tenderService) buildRecommendationPage(
	ctx context.Context,
	recommendations []company.RecommendedTenderResponse,
	form *SearchForm,
	companyIDs []string,
	excluded map[string]struct{},
	excludedByCompany map[string]map[string]struct{},
	now int64,
	offset int,
	limit int,
) (recommendationPageResult, error) {
	seenTenderIDs := make(map[string]struct{}, len(recommendations))
	pageStart := offset
	pageEnd := offset + limit
	if pageStart < 0 {
		pageStart = 0
	}
	if pageEnd < pageStart {
		pageEnd = pageStart
	}

	result := recommendationPageResult{
		items: make([]rankedRecommendedTender, 0, limit),
	}

	for start := 0; start < len(recommendations); start += recommendationResolveBatchSize {
		end := start + recommendationResolveBatchSize
		if end > len(recommendations) {
			end = len(recommendations)
		}

		tenderByRef, err := s.resolveRecommendedTenders(ctx, recommendations[start:end])
		if err != nil {
			return recommendationPageResult{}, err
		}

		for _, rec := range recommendations[start:end] {
			tenderRef := strings.TrimSpace(rec.TenderID)
			tender, ok := tenderByRef[tenderRef]
			if !ok {
				continue
			}
			if len(companyIDs) > 0 {
				if isRecommendedTenderExcludedForAllCompanies(tender, tenderRef, excludedByCompany, companyIDs) {
					continue
				}
			} else if isRecommendedTenderExcluded(tender, tenderRef, excluded) {
				continue
			}
			if form.OnlyActiveDeadlines && !tender.IsRecommendable(now) {
				continue
			}
			if len(form.Status) > 0 && !statusAllowed(tender.Status, form.Status) {
				continue
			}
			if markResolvedRecommendedTenderSeen(seenTenderIDs, tender, tenderRef) {
				continue
			}

			result.total++
			if int(result.total) <= pageStart || len(result.items) >= limit {
				continue
			}
			if int(result.total) > pageEnd {
				continue
			}

			result.items = append(result.items, rankedRecommendedTender{
				tender:    tender,
				rank:      rec.Rank,
				analysis:  rec.Analysis,
				tenderRef: tenderRef,
			})
		}
	}

	return result, nil
}