package towns

import (
	"dk/internal/store"
	"fmt"
	"math"
	"slices"
	"sort"
	"strconv"
	"strings"
	"sync"

	"dk/internal/helpers"
)

// Town represents a town in the game
type Town struct {
	ID       int    `json:"id"`
	Name     string `json:"name"`
	X        int    `json:"x"`
	Y        int    `json:"y"`
	InnCost  int    `json:"inn_cost"`
	MapCost  int    `json:"map_cost"`
	TPCost   int    `json:"tp_cost"`
	ShopList string `json:"shop_list"`
}

func (t *Town) Save() error {
	townStore := GetStore()
	townStore.UpdateTown(t)
	return nil
}

func (t *Town) Delete() error {
	townStore := GetStore()
	townStore.RemoveTown(t.ID)
	return nil
}

// Creates a new Town with sensible defaults
func New() *Town {
	return &Town{
		Name:     "",
		X:        0, // Default coordinates
		Y:        0,
		InnCost:  50,  // Default inn cost
		MapCost:  100, // Default map cost
		TPCost:   25,  // Default teleport cost
		ShopList: "",  // No items by default
	}
}

// Validate checks if town has valid values
func (t *Town) Validate() error {
	if t.Name == "" {
		return fmt.Errorf("town name cannot be empty")
	}
	if t.InnCost < 0 {
		return fmt.Errorf("town InnCost cannot be negative")
	}
	if t.MapCost < 0 {
		return fmt.Errorf("town MapCost cannot be negative")
	}
	if t.TPCost < 0 {
		return fmt.Errorf("town TPCost cannot be negative")
	}
	return nil
}

// TownStore provides in-memory storage with O(1) lookups and town-specific indices
type TownStore struct {
	*store.BaseStore[Town]                // Embedded generic store
	byName                 map[string]int // Name (lowercase) -> ID
	byCoords               map[string]int // "x,y" -> ID
	byInnCost              map[int][]int  // InnCost -> []ID
	byTPCost               map[int][]int  // TPCost -> []ID
	allByID                []int          // All IDs sorted by ID
	mu                     sync.RWMutex   // Protects indices
}

// Global in-memory store
var townStore *TownStore
var storeOnce sync.Once

// Initialize the in-memory store
func initStore() {
	townStore = &TownStore{
		BaseStore: store.NewBaseStore[Town](),
		byName:    make(map[string]int),
		byCoords:  make(map[string]int),
		byInnCost: make(map[int][]int),
		byTPCost:  make(map[int][]int),
		allByID:   make([]int, 0),
	}
}

// GetStore returns the global town store
func GetStore() *TownStore {
	storeOnce.Do(initStore)
	return townStore
}

// AddTown adds a town to the in-memory store and updates all indices
func (ts *TownStore) AddTown(town *Town) {
	ts.mu.Lock()
	defer ts.mu.Unlock()

	// Validate town
	if err := town.Validate(); err != nil {
		return
	}

	// Add to base store
	ts.Add(town.ID, town)

	// Rebuild indices
	ts.rebuildIndicesUnsafe()
}

// RemoveTown removes a town from the store and updates indices
func (ts *TownStore) RemoveTown(id int) {
	ts.mu.Lock()
	defer ts.mu.Unlock()

	// Remove from base store
	ts.Remove(id)

	// Rebuild indices
	ts.rebuildIndicesUnsafe()
}

// UpdateTown updates a town efficiently
func (ts *TownStore) UpdateTown(town *Town) {
	ts.mu.Lock()
	defer ts.mu.Unlock()

	// Validate town
	if err := town.Validate(); err != nil {
		return
	}

	// Update base store
	ts.Add(town.ID, town)

	// Rebuild indices
	ts.rebuildIndicesUnsafe()
}

// LoadData loads town data from JSON file, or starts with empty store
func LoadData(dataPath string) error {
	ts := GetStore()

	// Load from base store, which handles JSON loading
	if err := ts.BaseStore.LoadData(dataPath); err != nil {
		return err
	}

	// Rebuild indices from loaded data
	ts.rebuildIndices()
	return nil
}

// SaveData saves town data to JSON file
func SaveData(dataPath string) error {
	ts := GetStore()
	return ts.BaseStore.SaveData(dataPath)
}

// coordsKey creates a key for coordinate-based lookup
func coordsKey(x, y int) string {
	return strconv.Itoa(x) + "," + strconv.Itoa(y)
}

// rebuildIndicesUnsafe rebuilds all indices from base store data (caller must hold lock)
func (ts *TownStore) rebuildIndicesUnsafe() {
	// Clear indices
	ts.byName = make(map[string]int)
	ts.byCoords = make(map[string]int)
	ts.byInnCost = make(map[int][]int)
	ts.byTPCost = make(map[int][]int)
	ts.allByID = make([]int, 0)

	// Collect all towns and build indices
	allTowns := ts.GetAll()

	for id, town := range allTowns {
		// Name index (case-insensitive)
		ts.byName[strings.ToLower(town.Name)] = id

		// Coordinates index
		ts.byCoords[coordsKey(town.X, town.Y)] = id

		// Cost indices
		ts.byInnCost[town.InnCost] = append(ts.byInnCost[town.InnCost], id)
		ts.byTPCost[town.TPCost] = append(ts.byTPCost[town.TPCost], id)

		// All IDs
		ts.allByID = append(ts.allByID, id)
	}

	// Sort all by ID
	sort.Ints(ts.allByID)

	// Sort cost indices by ID
	for innCost := range ts.byInnCost {
		sort.Ints(ts.byInnCost[innCost])
	}

	for tpCost := range ts.byTPCost {
		sort.Ints(ts.byTPCost[tpCost])
	}
}

// rebuildIndices rebuilds all town-specific indices from base store data
func (ts *TownStore) rebuildIndices() {
	ts.mu.Lock()
	defer ts.mu.Unlock()
	ts.rebuildIndicesUnsafe()
}

// Retrieves a town by ID
func Find(id int) (*Town, error) {
	ts := GetStore()
	town, exists := ts.GetByID(id)
	if !exists {
		return nil, fmt.Errorf("town with ID %d not found", id)
	}
	return town, nil
}

// Retrieves all towns
func All() ([]*Town, error) {
	ts := GetStore()
	ts.mu.RLock()
	defer ts.mu.RUnlock()

	result := make([]*Town, 0, len(ts.allByID))
	for _, id := range ts.allByID {
		if town, exists := ts.GetByID(id); exists {
			result = append(result, town)
		}
	}
	return result, nil
}

// Retrieves a town by name (case-insensitive)
func ByName(name string) (*Town, error) {
	ts := GetStore()
	ts.mu.RLock()
	defer ts.mu.RUnlock()

	id, exists := ts.byName[strings.ToLower(name)]
	if !exists {
		return nil, fmt.Errorf("town with name '%s' not found", name)
	}

	town, exists := ts.GetByID(id)
	if !exists {
		return nil, fmt.Errorf("town with name '%s' not found", name)
	}

	return town, nil
}

// Retrieves towns with inn cost at most the specified amount
func ByMaxInnCost(maxCost int) ([]*Town, error) {
	ts := GetStore()
	ts.mu.RLock()
	defer ts.mu.RUnlock()

	var result []*Town
	for cost := 0; cost <= maxCost; cost++ {
		if ids, exists := ts.byInnCost[cost]; exists {
			for _, id := range ids {
				if town, exists := ts.GetByID(id); exists {
					result = append(result, town)
				}
			}
		}
	}
	return result, nil
}

// Retrieves towns with teleport cost at most the specified amount
func ByMaxTPCost(maxCost int) ([]*Town, error) {
	ts := GetStore()
	ts.mu.RLock()
	defer ts.mu.RUnlock()

	var result []*Town
	for cost := 0; cost <= maxCost; cost++ {
		if ids, exists := ts.byTPCost[cost]; exists {
			for _, id := range ids {
				if town, exists := ts.GetByID(id); exists {
					result = append(result, town)
				}
			}
		}
	}
	return result, nil
}

// Retrieves a town by its x, y coordinates
func ByCoords(x, y int) (*Town, error) {
	ts := GetStore()
	ts.mu.RLock()
	defer ts.mu.RUnlock()

	id, exists := ts.byCoords[coordsKey(x, y)]
	if !exists {
		return nil, nil // Return nil if not found (like original)
	}

	town, exists := ts.GetByID(id)
	if !exists {
		return nil, nil
	}

	return town, nil
}

// ExistsAt checks for a town at the given coordinates, returning true/false
func ExistsAt(x, y int) bool {
	ts := GetStore()
	ts.mu.RLock()
	defer ts.mu.RUnlock()

	_, exists := ts.byCoords[coordsKey(x, y)]
	return exists
}

// Retrieves towns within a certain distance from a point
func ByDistance(fromX, fromY, maxDistance int) ([]*Town, error) {
	ts := GetStore()
	ts.mu.RLock()
	defer ts.mu.RUnlock()

	var result []*Town
	maxDistance2 := float64(maxDistance * maxDistance)

	for _, id := range ts.allByID {
		if town, exists := ts.GetByID(id); exists {
			if town.DistanceFromSquared(fromX, fromY) <= maxDistance2 {
				result = append(result, town)
			}
		}
	}

	// Sort by distance, then by ID
	sort.Slice(result, func(i, j int) bool {
		distI := result[i].DistanceFromSquared(fromX, fromY)
		distJ := result[j].DistanceFromSquared(fromX, fromY)
		if distI == distJ {
			return result[i].ID < result[j].ID
		}
		return distI < distJ
	})

	return result, nil
}

// Saves a new town to the in-memory store and sets the ID
func (t *Town) Insert() error {
	ts := GetStore()

	// Validate before insertion
	if err := t.Validate(); err != nil {
		return fmt.Errorf("validation failed: %w", err)
	}

	// Assign new ID if not set
	if t.ID == 0 {
		t.ID = ts.GetNextID()
	}

	// Add to store
	ts.AddTown(t)
	return nil
}

// Returns the shop items as a slice of item IDs
func (t *Town) GetShopItems() []int {
	return helpers.StringToInts(t.ShopList)
}

// Sets the shop items from a slice of item IDs
func (t *Town) SetShopItems(items []int) {
	t.ShopList = helpers.IntsToString(items)
}

// Checks if the town's shop sells a specific item ID
func (t *Town) HasShopItem(itemID int) bool {
	return slices.Contains(t.GetShopItems(), itemID)
}

// Calculates the squared distance from this town to given coordinates
func (t *Town) DistanceFromSquared(x, y int) float64 {
	dx := float64(t.X - x)
	dy := float64(t.Y - y)
	return dx*dx + dy*dy // Return squared distance for performance
}

// Calculates the actual distance from this town to given coordinates
func (t *Town) DistanceFrom(x, y int) float64 {
	return math.Sqrt(t.DistanceFromSquared(x, y))
}

// Returns true if this is the starting town (Midworld)
func (t *Town) IsStartingTown() bool {
	return t.X == 0 && t.Y == 0
}

// Returns true if the player can afford the inn
func (t *Town) CanAffordInn(gold int) bool {
	return gold >= t.InnCost
}

// Returns true if the player can afford to buy the map
func (t *Town) CanAffordMap(gold int) bool {
	return gold >= t.MapCost
}

// Returns true if the player can afford to teleport here
func (t *Town) CanAffordTeleport(gold int) bool {
	return gold >= t.TPCost
}

// Returns true if the town has a shop with items
func (t *Town) HasShop() bool {
	return len(t.GetShopItems()) > 0
}

// Returns the town's coordinates
func (t *Town) GetPosition() (int, int) {
	return t.X, t.Y
}

// Sets the town's coordinates
func (t *Town) SetPosition(x, y int) {
	t.X = x
	t.Y = y
}