package services

import (
	"errors"
	"fmt"
	"sort"
	"strings"
	"time"

	"git.mchus.pro/mchus/priceforge/internal/models"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

func upsertSuggestion(prev StockMappingSuggestion, candidate StockMappingSuggestion) StockMappingSuggestion {
	if strings.TrimSpace(prev.Partnumber) == "" {
		return candidate
	}
	if strings.TrimSpace(prev.Description) == "" && strings.TrimSpace(candidate.Description) != "" {
		prev.Description = candidate.Description
	}
	if prev.Reason != "conflict" && candidate.Reason == "conflict" {
		prev.Reason = "conflict"
	}
	return prev
}

func (s *StockImportService) ListMappings(page, perPage int, search string) ([]StockMappingRow, int64, error) {
	if s.db == nil {
		return nil, 0, fmt.Errorf("offline mode: mappings unavailable")
	}
	if page < 1 {
		page = 1
	}
	if perPage < 1 {
		perPage = 50
	}
	if perPage > 500 {
		perPage = 500
	}

	offset := (page - 1) * perPage
	query := s.db.Model(&models.PartnumberBookItem{})
	if search = strings.TrimSpace(search); search != "" {
		like := "%" + search + "%"
		query = query.Where("partnumber LIKE ? OR lots_json LIKE ? OR description LIKE ?", like, like, like)
	}

	var total int64
	if err := query.Count(&total).Error; err != nil {
		return nil, 0, err
	}

	var items []models.PartnumberBookItem
	if err := query.Order("partnumber ASC").Offset(offset).Limit(perPage).Find(&items).Error; err != nil {
		return nil, 0, err
	}
	rows := make([]StockMappingRow, 0, len(items))
	for _, item := range items {
		lotName := ""
		for _, lot := range parseSnapshotLots(item.LotsJSON) {
			lotName = lot.LotName
			break
		}
		rows = append(rows, StockMappingRow{
			Partnumber:  item.Partnumber,
			LotName:     lotName,
			Description: item.Description,
		})
	}
	return rows, total, nil
}

func (s *StockImportService) UpsertMapping(partnumber, lotName, description string) error {
	if s.db == nil {
		return fmt.Errorf("offline mode: mappings unavailable")
	}
	partnumber = strings.TrimSpace(partnumber)
	lotName = strings.TrimSpace(lotName)
	description = strings.TrimSpace(description)
	if partnumber == "" {
		return fmt.Errorf("partnumber is required")
	}

	if lotName != "" {
		var lotCount int64
		if err := s.db.Model(&models.Lot{}).Where("lot_name = ?", lotName).Count(&lotCount).Error; err != nil {
			return err
		}
		if lotCount == 0 {
			return fmt.Errorf("lot not found: %s", lotName)
		}
	}

	return s.db.Transaction(func(tx *gorm.DB) error {
		var existing models.PartnumberBookItem
		err := tx.Where("LOWER(TRIM(partnumber)) = LOWER(TRIM(?))", partnumber).First(&existing).Error
		if err != nil && !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}
		if description == "" {
			if existing.Description != nil && strings.TrimSpace(*existing.Description) != "" {
				description = strings.TrimSpace(*existing.Description)
			}
		}
		var descPtr *string
		if description != "" {
			descPtr = &description
		}
		return tx.Clauses(clause.OnConflict{
			Columns:   []clause.Column{{Name: "partnumber"}},
			DoUpdates: clause.AssignmentColumns([]string{"lots_json", "description"}),
		}).Create(&models.PartnumberBookItem{
			Partnumber:  partnumber,
			LotsJSON:    fmt.Sprintf(`[{"lot_name":%q,"qty":1}]`, lotName),
			Description: descPtr,
		}).Error
	})
}

func (s *StockImportService) DeleteMapping(partnumber string) (int64, error) {
	if s.db == nil {
		return 0, fmt.Errorf("offline mode: mappings unavailable")
	}
	partnumber = strings.TrimSpace(partnumber)
	if partnumber == "" {
		return 0, fmt.Errorf("partnumber is required")
	}
	res := s.db.Where("LOWER(TRIM(partnumber)) = LOWER(TRIM(?))", partnumber).Delete(&models.PartnumberBookItem{})
	return res.RowsAffected, res.Error
}

func (s *StockImportService) ListIgnoreRules(page, perPage int) ([]models.StockIgnoreRule, int64, error) {
	if s.db == nil {
		return nil, 0, fmt.Errorf("offline mode: ignore rules unavailable")
	}
	if page < 1 {
		page = 1
	}
	if perPage < 1 {
		perPage = 50
	}
	if perPage > 500 {
		perPage = 500
	}

	offset := (page - 1) * perPage
	query := s.db.Model(&models.VendorPartnumberSeen{}).Where("is_ignored = ?", true)
	var total int64
	if err := query.Count(&total).Error; err != nil {
		return nil, 0, err
	}
	var seenRows []models.VendorPartnumberSeen
	if err := query.Order("id DESC").Offset(offset).Limit(perPage).Find(&seenRows).Error; err != nil {
		return nil, 0, err
	}
	rows := make([]models.StockIgnoreRule, 0, len(seenRows))
	for _, row := range seenRows {
		pattern := strings.TrimSpace(row.Partnumber)
		if vendor := strings.TrimSpace(row.Vendor); vendor != "" {
			pattern = vendor + "|" + pattern
		}
		rows = append(rows, models.StockIgnoreRule{
			ID:        uint(row.ID),
			Target:    "partnumber",
			MatchType: "exact",
			Pattern:   pattern,
			CreatedAt: row.CreatedAt,
		})
	}
	return rows, total, nil
}

func (s *StockImportService) UpsertIgnoreRule(target, matchType, pattern string) error {
	if s.db == nil {
		return fmt.Errorf("offline mode: ignore rules unavailable")
	}
	if normalizeIgnoreTarget(target) != "partnumber" || normalizeIgnoreMatchType(matchType) != "exact" {
		return fmt.Errorf("only exact partnumber ignore is supported")
	}
	pattern = strings.TrimSpace(pattern)
	if pattern == "" {
		return fmt.Errorf("pattern is required")
	}
	vendor := ""
	partnumber := pattern
	if parts := strings.SplitN(pattern, "|", 2); len(parts) == 2 {
		vendor = strings.TrimSpace(parts[0])
		partnumber = strings.TrimSpace(parts[1])
	}
	if partnumber == "" {
		return fmt.Errorf("partnumber is required")
	}
	now := time.Now()
	return s.db.Transaction(func(tx *gorm.DB) error {
		var existing models.VendorPartnumberSeen
		err := tx.Where("LOWER(TRIM(partnumber)) = LOWER(TRIM(?))", partnumber).First(&existing).Error
		if err == nil {
			updates := map[string]any{
				"last_seen_at": now,
				"is_ignored":   true,
				"ignored_at":   now,
			}
			if strings.TrimSpace(existing.SourceType) != "stock" {
				updates["source_type"] = "manual"
			}
			if strings.TrimSpace(existing.Vendor) == "" && vendor != "" {
				updates["vendor"] = vendor
			}
			return tx.Model(&models.VendorPartnumberSeen{}).
				Where("id = ?", existing.ID).
				Updates(updates).Error
		}
		if !errors.Is(err, gorm.ErrRecordNotFound) {
			return err
		}
		return tx.Create(&models.VendorPartnumberSeen{
			SourceType: "manual",
			Vendor:     vendor,
			Partnumber: partnumber,
			LastSeenAt: now,
			IsIgnored:  true,
			IgnoredAt:  &now,
		}).Error
	})
}

func (s *StockImportService) DeleteIgnoreRule(id uint) (int64, error) {
	if s.db == nil {
		return 0, fmt.Errorf("offline mode: ignore rules unavailable")
	}
	res := s.db.Model(&models.VendorPartnumberSeen{}).
		Where("id = ?", id).
		Updates(map[string]any{"is_ignored": false, "ignored_at": nil, "ignored_by": nil})
	return res.RowsAffected, res.Error
}

func (s *StockImportService) loadIgnoreRules() ([]stockIgnoreRule, error) {
	var rows []models.StockIgnoreRule
	if err := s.db.Find(&rows).Error; err != nil {
		return nil, err
	}
	rules := make([]stockIgnoreRule, 0, len(rows))
	for _, row := range rows {
		target := normalizeIgnoreTarget(row.Target)
		matchType := normalizeIgnoreMatchType(row.MatchType)
		pattern := normalizeKey(row.Pattern)
		if target == "" || matchType == "" || pattern == "" {
			continue
		}
		rules = append(rules, stockIgnoreRule{
			Target:    target,
			MatchType: matchType,
			Pattern:   pattern,
		})
	}
	return rules, nil
}

func collectSortedSuggestions(src map[string]StockMappingSuggestion, limit int) []StockMappingSuggestion {
	if len(src) == 0 {
		return nil
	}
	items := make([]StockMappingSuggestion, 0, len(src))
	for _, item := range src {
		items = append(items, item)
	}
	sort.Slice(items, func(i, j int) bool {
		return strings.ToLower(items[i].Partnumber) < strings.ToLower(items[j].Partnumber)
	})
	if limit > 0 && len(items) > limit {
		return items[:limit]
	}
	return items
}

func (s *StockImportService) loadIgnoredSeenIndex() (*ignoreIndex, error) {
	var rows []struct {
		Partnumber string
		IsPattern  bool
	}
	if err := s.db.Model(&models.VendorPartnumberSeen{}).
		Select("partnumber, is_pattern").
		Where("is_ignored = ?", true).
		Scan(&rows).Error; err != nil {
		return nil, err
	}
	idx := &ignoreIndex{exact: make(map[string]struct{}, len(rows))}
	for _, row := range rows {
		k := normalizeKey(row.Partnumber)
		if k == "" {
			continue
		}
		if row.IsPattern {
			idx.patterns = append(idx.patterns, k)
		} else {
			idx.exact[k] = struct{}{}
		}
	}
	return idx, nil
}

func isIgnoredBySeenIndex(idx *ignoreIndex, _ string, partnumber string) bool {
	if idx == nil {
		return false
	}
	return idx.isIgnored(normalizeKey(partnumber))
}

func (s *StockImportService) upsertSeenRows(rows map[string]models.VendorPartnumberSeen) error {
	if len(rows) == 0 {
		return nil
	}
	now := time.Now()
	return s.db.Transaction(func(tx *gorm.DB) error {
		for _, row := range rows {
			vendor := strings.TrimSpace(row.Vendor)
			partnumber := strings.TrimSpace(row.Partnumber)
			if partnumber == "" {
				continue
			}
			trimmedDesc := func() *string {
				if row.Description == nil {
					return nil
				}
				v := strings.TrimSpace(*row.Description)
				if v == "" {
					return nil
				}
				return &v
			}()

			var existing models.VendorPartnumberSeen
			err := tx.Where("LOWER(TRIM(partnumber)) = LOWER(TRIM(?))", partnumber).First(&existing).Error
			if err == nil {
				updates := map[string]any{
					"last_seen_at": now,
					"updated_at":   now,
				}
				// Preserve stock provenance for unmapped analysis.
				if strings.TrimSpace(existing.SourceType) != "stock" && strings.TrimSpace(row.SourceType) != "" {
					updates["source_type"] = strings.TrimSpace(row.SourceType)
				}
				if strings.TrimSpace(existing.Vendor) == "" && vendor != "" {
					updates["vendor"] = vendor
				}
				if trimmedDesc != nil {
					updates["description"] = *trimmedDesc
				}
				if err := tx.Model(&models.VendorPartnumberSeen{}).
					Where("id = ?", existing.ID).
					Updates(updates).Error; err != nil {
					return err
				}
				continue
			}
			if !errors.Is(err, gorm.ErrRecordNotFound) {
				return err
			}
			if err := tx.Create(&models.VendorPartnumberSeen{
				SourceType: row.SourceType,
				Vendor:     vendor,
				Partnumber: partnumber,
				LastSeenAt: now,
				Description: func() *string {
					if trimmedDesc == nil {
						return nil
					}
					v := *trimmedDesc
					return &v
				}(),
			}).Error; err != nil {
				return err
			}
		}
		return nil
	})
}

func shouldIgnoreStockRow(row stockImportRow, rules []stockIgnoreRule) bool {
	if len(rules) == 0 {
		return false
	}
	partnumber := normalizeKey(row.Article)
	description := normalizeKey(row.Description)
	for _, rule := range rules {
		candidate := ""
		if rule.Target == "partnumber" {
			candidate = partnumber
		} else {
			candidate = description
		}
		if candidate == "" || rule.Pattern == "" {
			continue
		}
		switch rule.MatchType {
		case "exact":
			if candidate == rule.Pattern {
				return true
			}
		case "prefix":
			if strings.HasPrefix(candidate, rule.Pattern) {
				return true
			}
		case "suffix":
			if strings.HasSuffix(candidate, rule.Pattern) {
				return true
			}
		}
	}
	return false
}

func normalizeIgnoreTarget(v string) string {
	switch strings.ToLower(strings.TrimSpace(v)) {
	case "partnumber":
		return "partnumber"
	case "description":
		return "description"
	default:
		return ""
	}
}

func normalizeIgnoreMatchType(v string) string {
	switch strings.ToLower(strings.TrimSpace(v)) {
	case "exact":
		return "exact"
	case "prefix":
		return "prefix"
	case "suffix":
		return "suffix"
	default:
		return ""
	}
}