package appearances

import (
	"fmt"
	"maps"
	"strings"
	"sync"

	"eq2emu/internal/database"
)

// MasterList is a specialized appearance master list optimized for:
// - Fast ID-based lookups (O(1))
// - Fast name-based searching (indexed)
// - Fast client version filtering (O(1))
// - Efficient range queries and statistics
type MasterList struct {
	// Core storage
	appearances map[int32]*Appearance // ID -> Appearance
	mutex       sync.RWMutex

	// Specialized indices for O(1) lookups
	byMinClient map[int16][]*Appearance  // MinClient -> appearances
	byNamePart  map[string][]*Appearance // Name substring -> appearances (for common searches)

	// Cached metadata
	clientVersions []int16 // Unique client versions (cached)
	metaStale      bool    // Whether metadata cache needs refresh
}

// NewMasterList creates a new specialized appearance master list
func NewMasterList() *MasterList {
	return &MasterList{
		appearances: make(map[int32]*Appearance),
		byMinClient: make(map[int16][]*Appearance),
		byNamePart:  make(map[string][]*Appearance),
		metaStale:   true,
	}
}

// refreshMetaCache updates the client versions cache
func (ml *MasterList) refreshMetaCache() {
	if !ml.metaStale {
		return
	}

	clientVersionSet := make(map[int16]struct{})

	// Collect unique client versions
	for _, appearance := range ml.appearances {
		clientVersionSet[appearance.MinClient] = struct{}{}
	}

	// Clear existing cache and rebuild
	ml.clientVersions = ml.clientVersions[:0]
	for version := range clientVersionSet {
		ml.clientVersions = append(ml.clientVersions, version)
	}

	ml.metaStale = false
}

// updateNameIndices updates name-based indices for an appearance
func (ml *MasterList) updateNameIndices(appearance *Appearance, add bool) {
	// Index common name patterns for fast searching
	name := strings.ToLower(appearance.Name)
	partsSet := make(map[string]struct{}) // Use set to avoid duplicates

	// Add full name
	partsSet[name] = struct{}{}

	// Add word-based indices for multi-word names
	if strings.Contains(name, " ") {
		words := strings.FieldsSeq(name)
		for word := range words {
			partsSet[word] = struct{}{}
		}
	}

	// Add prefix indices for common prefixes
	if len(name) >= 3 {
		partsSet[name[:3]] = struct{}{}
	}
	if len(name) >= 5 {
		partsSet[name[:5]] = struct{}{}
	}

	// Convert set to slice
	for part := range partsSet {
		if add {
			ml.byNamePart[part] = append(ml.byNamePart[part], appearance)
		} else {
			// Remove from name part index
			if namePartApps := ml.byNamePart[part]; namePartApps != nil {
				for i, app := range namePartApps {
					if app.ID == appearance.ID {
						ml.byNamePart[part] = append(namePartApps[:i], namePartApps[i+1:]...)
						break
					}
				}
			}
		}
	}
}

// AddAppearance adds an appearance with full indexing
func (ml *MasterList) AddAppearance(appearance *Appearance) bool {
	if appearance == nil {
		return false
	}

	ml.mutex.Lock()
	defer ml.mutex.Unlock()

	// Check if exists
	if _, exists := ml.appearances[appearance.ID]; exists {
		return false
	}

	// Add to core storage
	ml.appearances[appearance.ID] = appearance

	// Update client version index
	ml.byMinClient[appearance.MinClient] = append(ml.byMinClient[appearance.MinClient], appearance)

	// Update name indices
	ml.updateNameIndices(appearance, true)

	// Invalidate metadata cache
	ml.metaStale = true

	return true
}

// GetAppearance retrieves by ID (O(1))
func (ml *MasterList) GetAppearance(id int32) *Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	return ml.appearances[id]
}

// GetAppearanceSafe retrieves an appearance by ID with existence check
func (ml *MasterList) GetAppearanceSafe(id int32) (*Appearance, bool) {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	appearance, exists := ml.appearances[id]
	return appearance, exists
}

// HasAppearance checks if an appearance exists by ID
func (ml *MasterList) HasAppearance(id int32) bool {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	_, exists := ml.appearances[id]
	return exists
}

// GetAppearanceClone retrieves a cloned copy of an appearance by ID
func (ml *MasterList) GetAppearanceClone(id int32) *Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	appearance := ml.appearances[id]
	if appearance == nil {
		return nil
	}
	return appearance.Clone()
}

// GetAllAppearances returns a copy of all appearances map
func (ml *MasterList) GetAllAppearances() map[int32]*Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	// Return a copy to prevent external modification
	result := make(map[int32]*Appearance, len(ml.appearances))
	maps.Copy(result, ml.appearances)
	return result
}

// GetAllAppearancesList returns all appearances as a slice
func (ml *MasterList) GetAllAppearancesList() []*Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	result := make([]*Appearance, 0, len(ml.appearances))
	for _, appearance := range ml.appearances {
		result = append(result, appearance)
	}
	return result
}

// FindAppearancesByMinClient finds appearances with specific minimum client version (O(1))
func (ml *MasterList) FindAppearancesByMinClient(minClient int16) []*Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	return ml.byMinClient[minClient]
}

// GetCompatibleAppearances returns appearances compatible with the given client version
func (ml *MasterList) GetCompatibleAppearances(clientVersion int16) []*Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	var result []*Appearance

	// Collect all appearances with MinClient <= clientVersion
	for minClient, appearances := range ml.byMinClient {
		if minClient <= clientVersion {
			result = append(result, appearances...)
		}
	}

	return result
}

// FindAppearancesByName finds appearances containing the given name substring (optimized)
func (ml *MasterList) FindAppearancesByName(nameSubstring string) []*Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	searchKey := strings.ToLower(nameSubstring)

	// Try indexed lookup first for exact matches
	if indexedApps := ml.byNamePart[searchKey]; indexedApps != nil {
		// Return a copy to prevent external modification
		result := make([]*Appearance, len(indexedApps))
		copy(result, indexedApps)
		return result
	}

	// Fallback to full scan for partial matches
	var result []*Appearance
	for _, appearance := range ml.appearances {
		if contains(strings.ToLower(appearance.Name), searchKey) {
			result = append(result, appearance)
		}
	}

	return result
}

// GetAppearancesByIDRange returns appearances within the given ID range (inclusive)
func (ml *MasterList) GetAppearancesByIDRange(minID, maxID int32) []*Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	var result []*Appearance
	for id, appearance := range ml.appearances {
		if id >= minID && id <= maxID {
			result = append(result, appearance)
		}
	}

	return result
}

// GetAppearancesByClientRange returns appearances compatible within client version range
func (ml *MasterList) GetAppearancesByClientRange(minClientVersion, maxClientVersion int16) []*Appearance {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	var result []*Appearance

	// Collect all appearances with MinClient in range
	for minClient, appearances := range ml.byMinClient {
		if minClient >= minClientVersion && minClient <= maxClientVersion {
			result = append(result, appearances...)
		}
	}

	return result
}

// GetClientVersions returns all unique client versions using cached results
func (ml *MasterList) GetClientVersions() []int16 {
	ml.mutex.Lock() // Need write lock to potentially update cache
	defer ml.mutex.Unlock()

	ml.refreshMetaCache()

	// Return a copy to prevent external modification
	result := make([]int16, len(ml.clientVersions))
	copy(result, ml.clientVersions)
	return result
}

// RemoveAppearance removes an appearance and updates all indices
func (ml *MasterList) RemoveAppearance(id int32) bool {
	ml.mutex.Lock()
	defer ml.mutex.Unlock()

	appearance, exists := ml.appearances[id]
	if !exists {
		return false
	}

	// Remove from core storage
	delete(ml.appearances, id)

	// Remove from client version index
	clientApps := ml.byMinClient[appearance.MinClient]
	for i, app := range clientApps {
		if app.ID == id {
			ml.byMinClient[appearance.MinClient] = append(clientApps[:i], clientApps[i+1:]...)
			break
		}
	}

	// Remove from name indices
	ml.updateNameIndices(appearance, false)

	// Invalidate metadata cache
	ml.metaStale = true

	return true
}

// UpdateAppearance updates an existing appearance
func (ml *MasterList) UpdateAppearance(appearance *Appearance) error {
	if appearance == nil {
		return fmt.Errorf("appearance cannot be nil")
	}

	ml.mutex.Lock()
	defer ml.mutex.Unlock()

	// Check if exists
	old, exists := ml.appearances[appearance.ID]
	if !exists {
		return fmt.Errorf("appearance %d not found", appearance.ID)
	}

	// Remove old appearance from indices (but not core storage yet)
	clientApps := ml.byMinClient[old.MinClient]
	for i, app := range clientApps {
		if app.ID == appearance.ID {
			ml.byMinClient[old.MinClient] = append(clientApps[:i], clientApps[i+1:]...)
			break
		}
	}

	// Remove from name indices
	ml.updateNameIndices(old, false)

	// Update core storage
	ml.appearances[appearance.ID] = appearance

	// Add new appearance to indices
	ml.byMinClient[appearance.MinClient] = append(ml.byMinClient[appearance.MinClient], appearance)
	ml.updateNameIndices(appearance, true)

	// Invalidate metadata cache
	ml.metaStale = true

	return nil
}

// GetAppearanceCount returns the number of appearances
func (ml *MasterList) GetAppearanceCount() int {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	return len(ml.appearances)
}

// Size returns the total number of appearances
func (ml *MasterList) Size() int {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	return len(ml.appearances)
}

// IsEmpty returns true if the master list is empty
func (ml *MasterList) IsEmpty() bool {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()
	return len(ml.appearances) == 0
}

// ClearAppearances removes all appearances from the list
func (ml *MasterList) ClearAppearances() {
	ml.mutex.Lock()
	defer ml.mutex.Unlock()

	// Clear all maps
	ml.appearances = make(map[int32]*Appearance)
	ml.byMinClient = make(map[int16][]*Appearance)
	ml.byNamePart = make(map[string][]*Appearance)

	// Clear cached metadata
	ml.clientVersions = ml.clientVersions[:0]
	ml.metaStale = true
}

// Clear removes all appearances from the master list
func (ml *MasterList) Clear() {
	ml.ClearAppearances()
}

// ForEach executes a function for each appearance
func (ml *MasterList) ForEach(fn func(int32, *Appearance)) {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	for id, appearance := range ml.appearances {
		fn(id, appearance)
	}
}

// ValidateAppearances checks all appearances for consistency
func (ml *MasterList) ValidateAppearances() []string {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	var issues []string

	for id, appearance := range ml.appearances {
		if appearance == nil {
			issues = append(issues, fmt.Sprintf("Appearance ID %d is nil", id))
			continue
		}

		if appearance.GetID() != id {
			issues = append(issues, fmt.Sprintf("Appearance ID mismatch: map key %d != appearance ID %d", id, appearance.GetID()))
		}

		if len(appearance.GetName()) == 0 {
			issues = append(issues, fmt.Sprintf("Appearance ID %d has empty name", id))
		}

		if appearance.GetMinClientVersion() < 0 {
			issues = append(issues, fmt.Sprintf("Appearance ID %d has negative min client version: %d", id, appearance.GetMinClientVersion()))
		}
	}

	return issues
}

// IsValid returns true if all appearances are valid
func (ml *MasterList) IsValid() bool {
	issues := ml.ValidateAppearances()
	return len(issues) == 0
}

// GetStatistics returns statistics about the appearance collection
func (ml *MasterList) GetStatistics() map[string]any {
	ml.mutex.RLock()
	defer ml.mutex.RUnlock()

	stats := make(map[string]any)
	stats["total_appearances"] = len(ml.appearances)

	if len(ml.appearances) == 0 {
		return stats
	}

	// Count by minimum client version
	versionCounts := make(map[int16]int)
	var minID, maxID int32
	first := true

	for id, appearance := range ml.appearances {
		versionCounts[appearance.GetMinClientVersion()]++

		if first {
			minID = id
			maxID = id
			first = false
		} else {
			if id < minID {
				minID = id
			}
			if id > maxID {
				maxID = id
			}
		}
	}

	stats["appearances_by_min_client"] = versionCounts
	stats["min_id"] = minID
	stats["max_id"] = maxID
	stats["id_range"] = maxID - minID

	return stats
}

// LoadAllAppearances loads all appearances from the database into the master list
func (ml *MasterList) LoadAllAppearances(db *database.Database) error {
	if db == nil {
		return fmt.Errorf("database connection is nil")
	}

	// Clear existing appearances
	ml.Clear()

	query := `SELECT appearance_id, name, min_client_version FROM appearances ORDER BY appearance_id`
	rows, err := db.Query(query)
	if err != nil {
		return fmt.Errorf("failed to query appearances: %w", err)
	}
	defer rows.Close()

	count := 0
	for rows.Next() {
		appearance := &Appearance{
			db:    db,
			isNew: false,
		}

		err := rows.Scan(&appearance.ID, &appearance.Name, &appearance.MinClient)
		if err != nil {
			return fmt.Errorf("failed to scan appearance: %w", err)
		}

		if !ml.AddAppearance(appearance) {
			return fmt.Errorf("failed to add appearance %d to master list", appearance.ID)
		}

		count++
	}

	if err := rows.Err(); err != nil {
		return fmt.Errorf("error iterating appearance rows: %w", err)
	}

	return nil
}

// LoadAllAppearancesFromDatabase is a convenience function that creates a master list and loads all appearances
func LoadAllAppearancesFromDatabase(db *database.Database) (*MasterList, error) {
	masterList := NewMasterList()
	err := masterList.LoadAllAppearances(db)
	if err != nil {
		return nil, err
	}
	return masterList, nil
}

// contains checks if a string contains a substring (case-sensitive)
func contains(str, substr string) bool {
	if len(substr) == 0 {
		return true
	}
	if len(str) < len(substr) {
		return false
	}

	for i := 0; i <= len(str)-len(substr); i++ {
		if str[i:i+len(substr)] == substr {
			return true
		}
	}

	return false
}