package lotmatch

import (
	"encoding/json"
	"errors"
	"regexp"
	"sort"
	"strings"

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

var (
	ErrResolveConflict = errors.New("multiple lot matches")
	ErrResolveNotFound = errors.New("lot not found")
)

// MappingMatcher handles partnumber to LOT matching
type MappingMatcher struct {
	exactMappings       map[string]string   // normalized partnumber -> first LOT (for Resolve)
	exactLots           map[string][]string // normalized partnumber -> all LOTs (for MatchLots)
	exactLotName        map[string]string   // normalized LOT -> LOT
	wildcards           []wildcardMapping
	allLots             []string                     // all LOT names sorted by length (longest first)
	vendorExactMappings map[string]map[string]string // normalized vendor -> normalized partnumber -> lot
	catalogLots         map[string][]models.PartnumberBookLot
}

// LotResolver preserves legacy resolve behavior used by older tests and flows.
type LotResolver struct {
	partnumberToLots map[string][]string
	exactLots        map[string]string
	allLots          []string
}

type wildcardMapping struct {
	lotName string
	re      *regexp.Regexp
}

// NewMappingMatcherFromDB loads mappings and lots from database
func NewMappingMatcherFromDB(db *gorm.DB) (*MappingMatcher, error) {
	var mappings []models.LotPartnumber
	if db != nil && db.Migrator().HasTable(models.LotPartnumber{}.TableName()) {
		if err := db.Find(&mappings).Error; err != nil && !isMissingTableError(err) {
			return nil, err
		}
	}

	var lots []models.Lot
	if err := db.Select("lot_name").Find(&lots).Error; err != nil {
		return nil, err
	}

	catalogLots, err := loadCatalogLots(db)
	if err != nil {
		return nil, err
	}

	return NewMappingMatcherWithCatalog(mappings, lots, catalogLots), nil
}

// NewMappingMatcher creates a new matcher from mappings and lots
func NewMappingMatcher(mappings []models.LotPartnumber, lots []models.Lot) *MappingMatcher {
	return NewMappingMatcherWithCatalog(mappings, lots, nil)
}

func NewMappingMatcherWithCatalog(mappings []models.LotPartnumber, lots []models.Lot, catalogLots map[string][]models.PartnumberBookLot) *MappingMatcher {
	// Build exact mappings map
	exactMappings := make(map[string]string, len(mappings))
	exactLots := make(map[string][]string, len(mappings))
	vendorExactMappings := make(map[string]map[string]string)
	wildcards := make([]wildcardMapping, 0, len(mappings))
	for _, m := range mappings {
		pn := NormalizeKey(m.Partnumber)
		lot := strings.TrimSpace(m.LotName)
		vendor := normalizeVendorKey(m.Vendor)
		if pn != "" && lot != "" {
			if _, ok := vendorExactMappings[vendor]; !ok {
				vendorExactMappings[vendor] = make(map[string]string)
			}
			vendorExactMappings[vendor][pn] = lot

			if strings.Contains(pn, "*") {
				pattern := "^" + regexp.QuoteMeta(pn) + "$"
				pattern = strings.ReplaceAll(pattern, "\\*", ".*")
				re, err := regexp.Compile(pattern)
				if err == nil {
					wildcards = append(wildcards, wildcardMapping{lotName: lot, re: re})
				}
				continue
			}

			exactLots[pn] = append(exactLots[pn], lot)
			// Store first mapping only (ignore duplicates)
			if _, exists := exactMappings[pn]; !exists {
				exactMappings[pn] = lot
			}
		}
	}
	for key := range exactLots {
		exactLots[key] = uniqueCaseInsensitive(exactLots[key])
	}

	// Build sorted LOT list (longest first for prefix matching)
	allLots := make([]string, 0, len(lots))
	exactLotName := make(map[string]string, len(lots))
	for _, l := range lots {
		name := strings.TrimSpace(l.LotName)
		if name != "" {
			allLots = append(allLots, name)
			exactLotName[NormalizeKey(name)] = name
		}
	}

	// Sort by length descending, then alphabetically
	for i := 0; i < len(allLots); i++ {
		for j := i + 1; j < len(allLots); j++ {
			li := len([]rune(allLots[i]))
			lj := len([]rune(allLots[j]))
			if lj > li || (lj == li && allLots[j] < allLots[i]) {
				allLots[i], allLots[j] = allLots[j], allLots[i]
			}
		}
	}

	return &MappingMatcher{
		exactMappings:       exactMappings,
		exactLots:           exactLots,
		exactLotName:        exactLotName,
		wildcards:           wildcards,
		allLots:             allLots,
		vendorExactMappings: vendorExactMappings,
		catalogLots:         catalogLots,
	}
}

func loadCatalogLots(db *gorm.DB) (map[string][]models.PartnumberBookLot, error) {
	var items []models.PartnumberBookItem
	if db != nil && db.Migrator().HasTable(models.PartnumberBookItem{}.TableName()) {
		if err := db.Order("partnumber ASC").Find(&items).Error; err != nil && !isMissingTableError(err) {
			return nil, err
		}
	}
	result := make(map[string][]models.PartnumberBookLot, len(items))
	for _, item := range items {
		pnKey := NormalizeKey(item.Partnumber)
		if pnKey == "" {
			continue
		}
		var lots []models.PartnumberBookLot
		if err := json.Unmarshal([]byte(strings.TrimSpace(item.LotsJSON)), &lots); err != nil {
			continue
		}
		clean := make([]models.PartnumberBookLot, 0, len(lots))
		for _, lot := range lots {
			name := strings.TrimSpace(lot.LotName)
			if name == "" || lot.Qty <= 0 {
				continue
			}
			clean = append(clean, models.PartnumberBookLot{LotName: name, Qty: lot.Qty})
		}
		if len(clean) == 0 {
			continue
		}
		sort.Slice(clean, func(i, j int) bool { return clean[i].LotName < clean[j].LotName })
		result[pnKey] = clean
	}
	return result, nil
}

// NewLotResolver creates a resolver with legacy conflict-aware behavior.
func NewLotResolver(mappings []models.LotPartnumber, lots []models.Lot) *LotResolver {
	partnumberToLots := make(map[string][]string, len(mappings))
	for _, m := range mappings {
		if normalizeVendorKey(m.Vendor) != "" {
			continue
		}
		pn := NormalizeKey(m.Partnumber)
		lot := strings.TrimSpace(m.LotName)
		if pn == "" || lot == "" {
			continue
		}
		partnumberToLots[pn] = append(partnumberToLots[pn], lot)
	}
	for key := range partnumberToLots {
		partnumberToLots[key] = uniqueCaseInsensitive(partnumberToLots[key])
	}

	exactLots := make(map[string]string, len(lots))
	allLots := make([]string, 0, len(lots))
	for _, l := range lots {
		name := strings.TrimSpace(l.LotName)
		if name == "" {
			continue
		}
		exactLots[NormalizeKey(name)] = name
		allLots = append(allLots, name)
	}
	sort.Slice(allLots, func(i, j int) bool {
		li := len([]rune(allLots[i]))
		lj := len([]rune(allLots[j]))
		if li == lj {
			return allLots[i] < allLots[j]
		}
		return li > lj
	})

	return &LotResolver{
		partnumberToLots: partnumberToLots,
		exactLots:        exactLots,
		allLots:          allLots,
	}
}

// MatchLots returns all matching LOTs for a partnumber
// Returns empty slice if no match, or multiple LOTs if there's a conflict
func (m *MappingMatcher) MatchLots(partnumber string) []string {
	return m.MatchLotsWithVendor(partnumber, "")
}

// MatchLotsWithVendor returns mapped lots using vendor+partnumber with fallback to vendor-agnostic partnumber.
func (m *MappingMatcher) MatchLotsWithVendor(partnumber, vendor string) []string {
	items := m.MatchLotItemsWithVendor(partnumber, vendor)
	lots := make([]string, 0, len(items))
	for _, item := range items {
		if strings.TrimSpace(item.LotName) != "" {
			lots = append(lots, item.LotName)
		}
	}
	return uniqueCaseInsensitive(lots)
}

func (m *MappingMatcher) MatchLotItemsWithVendor(partnumber, vendor string) []models.PartnumberBookLot {
	if m == nil {
		return nil
	}

	key := NormalizeKey(partnumber)
	if key == "" {
		return nil
	}

	lots := make([]models.PartnumberBookLot, 0, 4)
	vk := normalizeVendorKey(vendor)
	if m.vendorExactMappings != nil {
		if byVendor := m.vendorExactMappings[vk]; len(byVendor) > 0 {
			if lot := strings.TrimSpace(byVendor[key]); lot != "" {
				return []models.PartnumberBookLot{{LotName: lot, Qty: 1}}
			}
		}
		if vk != "" {
			if fallback := m.vendorExactMappings[""]; len(fallback) > 0 {
				if lot := strings.TrimSpace(fallback[key]); lot != "" {
					return []models.PartnumberBookLot{{LotName: lot, Qty: 1}}
				}
			}
		}
	}
	if exact := m.catalogLots[key]; len(exact) > 0 {
		return append([]models.PartnumberBookLot(nil), exact...)
	}
	if exact := m.exactLots[key]; len(exact) > 0 {
		for _, lot := range exact {
			lots = append(lots, models.PartnumberBookLot{LotName: lot, Qty: 1})
		}
	}
	for _, wc := range m.wildcards {
		if wc.re == nil || !wc.re.MatchString(key) {
			continue
		}
		lots = append(lots, models.PartnumberBookLot{LotName: wc.lotName, Qty: 1})
	}
	if lot, ok := m.exactLotName[key]; ok && strings.TrimSpace(lot) != "" {
		lots = append(lots, models.PartnumberBookLot{LotName: lot, Qty: 1})
	}
	if matchedLot := m.FindPrefixMatch(partnumber); matchedLot != "" {
		lots = append(lots, models.PartnumberBookLot{LotName: matchedLot, Qty: 1})
	}
	return uniqueLotItems(lots)
}

// FindPrefixMatch finds the longest LOT that partnumber starts with
// Returns empty string if no match found
func (m *MappingMatcher) FindPrefixMatch(partnumber string) string {
	if m == nil {
		return ""
	}

	key := NormalizeKey(partnumber)
	if key == "" {
		return ""
	}

	// Find longest matching prefix
	for _, lot := range m.allLots {
		lotKey := NormalizeKey(lot)
		if lotKey != "" && strings.HasPrefix(key, lotKey) {
			return lot
		}
	}

	return ""
}

// Resolve resolves a partnumber to a single LOT
// Returns LOT name, method ("mapping", "prefix", "exact"), and error
func (m *MappingMatcher) Resolve(partnumber string) (string, string, error) {
	return m.ResolveWithVendor(partnumber, "")
}

// ResolveWithVendor resolves partnumber using vendor-first strategy and fallback to vendor-agnostic rows.
func (m *MappingMatcher) ResolveWithVendor(partnumber, vendor string) (string, string, error) {
	if m == nil {
		return "", "", ErrResolveNotFound
	}

	key := NormalizeKey(partnumber)
	if key == "" {
		return "", "", ErrResolveNotFound
	}

	vk := normalizeVendorKey(vendor)
	if byVendor, ok := m.vendorExactMappings[vk]; ok {
		if lot := strings.TrimSpace(byVendor[key]); lot != "" {
			return lot, "mapping", nil
		}
	}
	if vk != "" {
		if fallback, ok := m.vendorExactMappings[""]; ok {
			if lot := strings.TrimSpace(fallback[key]); lot != "" {
				return lot, "mapping", nil
			}
		}
	}

	if items := m.catalogLots[key]; len(items) > 0 {
		if len(items) == 1 {
			return items[0].LotName, "mapping", nil
		}
		return "", "", ErrResolveConflict
	}

	// Check exact mapping fallback map
	if lot, ok := m.exactMappings[key]; ok && strings.TrimSpace(lot) != "" {
		return lot, "mapping", nil
	}

	// Check if partnumber exactly matches a LOT
	for _, lot := range m.allLots {
		if NormalizeKey(lot) == key {
			return lot, "exact", nil
		}
	}

	// Try prefix match
	if matchedLot := m.FindPrefixMatch(partnumber); matchedLot != "" {
		return matchedLot, "prefix", nil
	}

	return "", "", ErrResolveNotFound
}

func normalizeVendorKey(v string) string {
	return strings.ToLower(strings.TrimSpace(v))
}

// Resolve returns LOT and resolve type using legacy labels:
// mapping_table | article_exact | prefix
func (r *LotResolver) Resolve(partnumber string) (string, string, error) {
	key := NormalizeKey(partnumber)
	if key == "" {
		return "", "", ErrResolveNotFound
	}

	if mapped := r.partnumberToLots[key]; len(mapped) > 0 {
		if len(mapped) == 1 {
			return mapped[0], "mapping_table", nil
		}
		return "", "", ErrResolveConflict
	}
	if exact, ok := r.exactLots[key]; ok {
		return exact, "article_exact", nil
	}

	best := ""
	bestLen := -1
	tie := false
	for _, lot := range r.allLots {
		lotKey := NormalizeKey(lot)
		if lotKey == "" {
			continue
		}
		if strings.HasPrefix(key, lotKey) {
			l := len([]rune(lotKey))
			if l > bestLen {
				best = lot
				bestLen = l
				tie = false
			} else if l == bestLen && !strings.EqualFold(best, lot) {
				tie = true
			}
		}
	}
	if best == "" {
		return "", "", ErrResolveNotFound
	}
	if tie {
		return "", "", ErrResolveConflict
	}
	return best, "prefix", nil
}

// NewLotResolverFromDB is an alias for NewMappingMatcherFromDB for backward compatibility
func NewLotResolverFromDB(db *gorm.DB) (*MappingMatcher, error) {
	return NewMappingMatcherFromDB(db)
}

// NormalizeKey normalizes a string for matching (lowercase, no spaces/special chars)
func NormalizeKey(v string) string {
	s := strings.ToLower(strings.TrimSpace(v))
	replacer := strings.NewReplacer(
		" ", "",
		"-", "",
		"_", "",
		".", "",
		"/", "",
		"\\", "",
		"\"", "",
		"'", "",
		"(", "",
		")", "",
	)
	return replacer.Replace(s)
}

func uniqueCaseInsensitive(values []string) []string {
	seen := make(map[string]struct{}, len(values))
	out := make([]string, 0, len(values))
	for _, v := range values {
		trimmed := strings.TrimSpace(v)
		if trimmed == "" {
			continue
		}
		key := strings.ToLower(trimmed)
		if _, ok := seen[key]; ok {
			continue
		}
		seen[key] = struct{}{}
		out = append(out, trimmed)
	}
	sort.Slice(out, func(i, j int) bool {
		return strings.ToLower(out[i]) < strings.ToLower(out[j])
	})
	return out
}

func uniqueLotItems(values []models.PartnumberBookLot) []models.PartnumberBookLot {
	seen := make(map[string]struct{}, len(values))
	out := make([]models.PartnumberBookLot, 0, len(values))
	for _, v := range values {
		trimmed := strings.TrimSpace(v.LotName)
		if trimmed == "" || v.Qty <= 0 {
			continue
		}
		key := strings.ToLower(trimmed)
		if _, ok := seen[key]; ok {
			continue
		}
		seen[key] = struct{}{}
		out = append(out, models.PartnumberBookLot{LotName: trimmed, Qty: v.Qty})
	}
	return out
}

func isMissingTableError(err error) bool {
	if err == nil {
		return false
	}
	msg := strings.ToLower(err.Error())
	return strings.Contains(msg, "no such table") || strings.Contains(msg, "doesn't exist")
}