package nigiri

import (
	"fmt"
	"maps"
	"reflect"
	"sort"
	"strings"
	"sync"
)

// Validatable interface for entities that can validate themselves
type Validatable interface {
	Validate() error
}

// IndexBuilder function type for building custom indices
type IndexBuilder[T any] func(allItems map[int]*T) any

// BaseStore provides generic storage with index management and constraints
type BaseStore[T any] struct {
	items         map[int]*T
	maxID         int
	mu            sync.RWMutex
	itemType      reflect.Type
	indices       map[string]any
	indexBuilders map[string]IndexBuilder[T]
	schema        *SchemaInfo
	uniqueIndices map[string]map[any]int // field -> value -> id
}

// NewBaseStore creates a new base store for type T with schema parsing
func NewBaseStore[T any]() *BaseStore[T] {
	var zero T
	schema := ParseSchema[T]()

	store := &BaseStore[T]{
		items:         make(map[int]*T),
		maxID:         0,
		itemType:      reflect.TypeOf(zero),
		indices:       make(map[string]any),
		indexBuilders: make(map[string]IndexBuilder[T]),
		schema:        schema,
		uniqueIndices: make(map[string]map[any]int),
	}

	// Initialize unique indices
	for fieldName, constraints := range schema.Constraints {
		for _, constraint := range constraints {
			if constraint.Type == ConstraintUnique {
				store.uniqueIndices[fieldName] = make(map[any]int)
			}
		}
	}

	// Auto-register indices for indexed fields
	store.registerSchemaIndices()

	return store
}

func (bs *BaseStore[T]) registerSchemaIndices() {
	for fieldName, indexName := range bs.schema.Indices {
		bs.RegisterIndex(indexName, BuildFieldLookupIndex[T](fieldName))
	}
}

// ValidateConstraints checks all constraints for an item
func (bs *BaseStore[T]) ValidateConstraints(id int, item *T) error {
	itemValue := reflect.ValueOf(item).Elem()

	for fieldName, constraints := range bs.schema.Constraints {
		fieldValue := itemValue.FieldByName(fieldName)
		if !fieldValue.IsValid() {
			continue
		}

		for _, constraint := range constraints {
			switch constraint.Type {
			case ConstraintRequired:
				if isZeroValue(fieldValue) {
					return fmt.Errorf("field %s is required", fieldName)
				}
			case ConstraintUnique:
				value := fieldValue.Interface()
				if existingID, exists := bs.uniqueIndices[fieldName][value]; exists && existingID != id {
					return fmt.Errorf("field %s value %v already exists", fieldName, value)
				}
			}
		}
	}

	return nil
}

func isZeroValue(v reflect.Value) bool {
	return v.Interface() == reflect.Zero(v.Type()).Interface()
}

func (bs *BaseStore[T]) updateUniqueIndices(id int, item *T, add bool) {
	itemValue := reflect.ValueOf(item).Elem()

	for fieldName := range bs.uniqueIndices {
		fieldValue := itemValue.FieldByName(fieldName)
		if !fieldValue.IsValid() {
			continue
		}

		value := fieldValue.Interface()
		if add {
			bs.uniqueIndices[fieldName][value] = id
		} else {
			delete(bs.uniqueIndices[fieldName], value)
		}
	}
}

// RegisterIndex registers an index builder function
func (bs *BaseStore[T]) RegisterIndex(name string, builder IndexBuilder[T]) {
	bs.mu.Lock()
	defer bs.mu.Unlock()
	bs.indexBuilders[name] = builder
}

// GetIndex retrieves a named index
func (bs *BaseStore[T]) GetIndex(name string) (any, bool) {
	bs.mu.RLock()
	defer bs.mu.RUnlock()
	index, exists := bs.indices[name]
	return index, exists
}

// RebuildIndices rebuilds all registered indices
func (bs *BaseStore[T]) RebuildIndices() {
	bs.mu.Lock()
	defer bs.mu.Unlock()
	bs.rebuildIndicesUnsafe()
}

func (bs *BaseStore[T]) rebuildIndicesUnsafe() {
	allItems := make(map[int]*T, len(bs.items))
	maps.Copy(allItems, bs.items)

	for name, builder := range bs.indexBuilders {
		bs.indices[name] = builder(allItems)
	}
}

// AddWithValidation adds item with constraint validation and index rebuild
func (bs *BaseStore[T]) AddWithValidation(id int, item *T) error {
	bs.mu.Lock()
	defer bs.mu.Unlock()

	// Validate constraints
	if err := bs.ValidateConstraints(id, item); err != nil {
		return err
	}

	// Custom validation
	if validatable, ok := any(item).(Validatable); ok {
		if err := validatable.Validate(); err != nil {
			return err
		}
	}

	// Update unique indices
	bs.updateUniqueIndices(id, item, true)

	bs.items[id] = item
	if id > bs.maxID {
		bs.maxID = id
	}

	bs.rebuildIndicesUnsafe()
	return nil
}

// AddWithRebuild adds item with validation and index rebuild
func (bs *BaseStore[T]) AddWithRebuild(id int, item *T) error {
	return bs.AddWithValidation(id, item)
}

// RemoveWithValidation removes item and updates constraints
func (bs *BaseStore[T]) RemoveWithValidation(id int) {
	bs.mu.Lock()
	defer bs.mu.Unlock()

	if item, exists := bs.items[id]; exists {
		bs.updateUniqueIndices(id, item, false)
	}

	delete(bs.items, id)
	bs.rebuildIndicesUnsafe()
}

// RemoveWithRebuild removes item and rebuilds indices
func (bs *BaseStore[T]) RemoveWithRebuild(id int) {
	bs.RemoveWithValidation(id)
}

// UpdateWithValidation updates item with validation and index rebuild
func (bs *BaseStore[T]) UpdateWithValidation(id int, item *T) error {
	return bs.AddWithValidation(id, item)
}

// UpdateWithRebuild updates item with validation and index rebuild
func (bs *BaseStore[T]) UpdateWithRebuild(id int, item *T) error {
	return bs.AddWithValidation(id, item)
}

// Find retrieves an item by ID
func (bs *BaseStore[T]) Find(id int) (*T, bool) {
	bs.mu.RLock()
	defer bs.mu.RUnlock()
	item, exists := bs.items[id]
	return item, exists
}

// AllSorted returns all items using named sorted index
func (bs *BaseStore[T]) AllSorted(indexName string) []*T {
	bs.mu.RLock()
	defer bs.mu.RUnlock()

	if index, exists := bs.indices[indexName]; exists {
		if sortedIDs, ok := index.([]int); ok {
			result := make([]*T, 0, len(sortedIDs))
			for _, id := range sortedIDs {
				if item, exists := bs.items[id]; exists {
					result = append(result, item)
				}
			}
			return result
		}
	}

	// Fallback: return all items by ID order
	ids := make([]int, 0, len(bs.items))
	for id := range bs.items {
		ids = append(ids, id)
	}
	sort.Ints(ids)

	result := make([]*T, 0, len(ids))
	for _, id := range ids {
		result = append(result, bs.items[id])
	}
	return result
}

// LookupByIndex finds single item using string lookup index
func (bs *BaseStore[T]) LookupByIndex(indexName, key string) (*T, bool) {
	bs.mu.RLock()
	defer bs.mu.RUnlock()

	if index, exists := bs.indices[indexName]; exists {
		if lookupMap, ok := index.(map[string]int); ok {
			if id, found := lookupMap[key]; found {
				if item, exists := bs.items[id]; exists {
					return item, true
				}
			}
		}
	}
	return nil, false
}

// GroupByIndex returns items grouped by key
func (bs *BaseStore[T]) GroupByIndex(indexName string, key any) []*T {
	bs.mu.RLock()
	defer bs.mu.RUnlock()

	if index, exists := bs.indices[indexName]; exists {
		switch groupMap := index.(type) {
		case map[int][]int:
			if intKey, ok := key.(int); ok {
				if ids, found := groupMap[intKey]; found {
					result := make([]*T, 0, len(ids))
					for _, id := range ids {
						if item, exists := bs.items[id]; exists {
							result = append(result, item)
						}
					}
					return result
				}
			}
		case map[string][]int:
			if strKey, ok := key.(string); ok {
				if ids, found := groupMap[strKey]; found {
					result := make([]*T, 0, len(ids))
					for _, id := range ids {
						if item, exists := bs.items[id]; exists {
							result = append(result, item)
						}
					}
					return result
				}
			}
		}
	}
	return []*T{}
}

// FilterByIndex returns items matching filter criteria
func (bs *BaseStore[T]) FilterByIndex(indexName string, filterFunc func(*T) bool) []*T {
	bs.mu.RLock()
	defer bs.mu.RUnlock()

	var sourceIDs []int

	if index, exists := bs.indices[indexName]; exists {
		if sortedIDs, ok := index.([]int); ok {
			sourceIDs = sortedIDs
		}
	}

	if sourceIDs == nil {
		for id := range bs.items {
			sourceIDs = append(sourceIDs, id)
		}
		sort.Ints(sourceIDs)
	}

	var result []*T
	for _, id := range sourceIDs {
		if item, exists := bs.items[id]; exists && filterFunc(item) {
			result = append(result, item)
		}
	}
	return result
}

// GetNextID returns the next available ID atomically
func (bs *BaseStore[T]) GetNextID() int {
	bs.mu.Lock()
	defer bs.mu.Unlock()
	bs.maxID++
	return bs.maxID
}

// GetByID retrieves an item by ID
func (bs *BaseStore[T]) GetByID(id int) (*T, bool) {
	return bs.Find(id)
}

// Add adds an item to the store (no validation)
func (bs *BaseStore[T]) Add(id int, item *T) {
	bs.mu.Lock()
	defer bs.mu.Unlock()
	bs.items[id] = item
	if id > bs.maxID {
		bs.maxID = id
	}
}

// Remove removes an item from the store (no validation)
func (bs *BaseStore[T]) Remove(id int) {
	bs.mu.Lock()
	defer bs.mu.Unlock()
	delete(bs.items, id)
}

// GetAll returns all items
func (bs *BaseStore[T]) GetAll() map[int]*T {
	bs.mu.RLock()
	defer bs.mu.RUnlock()
	result := make(map[int]*T, len(bs.items))
	maps.Copy(result, bs.items)
	return result
}

// Clear removes all items
func (bs *BaseStore[T]) Clear() {
	bs.mu.Lock()
	defer bs.mu.Unlock()
	bs.items = make(map[int]*T)
	bs.maxID = 0

	// Clear unique indices
	for fieldName := range bs.uniqueIndices {
		bs.uniqueIndices[fieldName] = make(map[any]int)
	}

	bs.rebuildIndicesUnsafe()
}

// Index Builder Functions

// BuildFieldLookupIndex creates index for any field by name
func BuildFieldLookupIndex[T any](fieldName string) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		index := make(map[string]int)
		for id, item := range allItems {
			itemValue := reflect.ValueOf(item).Elem()
			fieldValue := itemValue.FieldByName(fieldName)
			if !fieldValue.IsValid() {
				continue
			}

			key := fmt.Sprintf("%v", fieldValue.Interface())
			index[key] = id
		}
		return index
	}
}

// BuildStringLookupIndex creates string-to-ID mapping
func BuildStringLookupIndex[T any](keyFunc func(*T) string) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		index := make(map[string]int)
		for id, item := range allItems {
			key := keyFunc(item)
			index[key] = id
		}
		return index
	}
}

// BuildCaseInsensitiveLookupIndex creates lowercase string-to-ID mapping
func BuildCaseInsensitiveLookupIndex[T any](keyFunc func(*T) string) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		index := make(map[string]int)
		for id, item := range allItems {
			key := strings.ToLower(keyFunc(item))
			index[key] = id
		}
		return index
	}
}

// BuildIntGroupIndex creates int-to-[]ID mapping
func BuildIntGroupIndex[T any](keyFunc func(*T) int) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		index := make(map[int][]int)
		for id, item := range allItems {
			key := keyFunc(item)
			index[key] = append(index[key], id)
		}

		// Sort each group by ID
		for key := range index {
			sort.Ints(index[key])
		}

		return index
	}
}

// BuildStringGroupIndex creates string-to-[]ID mapping
func BuildStringGroupIndex[T any](keyFunc func(*T) string) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		index := make(map[string][]int)
		for id, item := range allItems {
			key := keyFunc(item)
			index[key] = append(index[key], id)
		}

		// Sort each group by ID
		for key := range index {
			sort.Ints(index[key])
		}

		return index
	}
}

// BuildSortedListIndex creates sorted []ID list
func BuildSortedListIndex[T any](sortFunc func(*T, *T) bool) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		ids := make([]int, 0, len(allItems))
		for id := range allItems {
			ids = append(ids, id)
		}

		sort.Slice(ids, func(i, j int) bool {
			return sortFunc(allItems[ids[i]], allItems[ids[j]])
		})

		return ids
	}
}

// BuildFilteredIntGroupIndex creates int-to-[]ID mapping for items passing filter
func BuildFilteredIntGroupIndex[T any](filterFunc func(*T) bool, keyFunc func(*T) int) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		index := make(map[int][]int)
		for id, item := range allItems {
			if filterFunc(item) {
				key := keyFunc(item)
				index[key] = append(index[key], id)
			}
		}

		// Sort each group by ID
		for key := range index {
			sort.Ints(index[key])
		}

		return index
	}
}

// BuildFilteredStringGroupIndex creates string-to-[]ID mapping for items passing filter
func BuildFilteredStringGroupIndex[T any](filterFunc func(*T) bool, keyFunc func(*T) string) IndexBuilder[T] {
	return func(allItems map[int]*T) any {
		index := make(map[string][]int)
		for id, item := range allItems {
			if filterFunc(item) {
				key := keyFunc(item)
				index[key] = append(index[key], id)
			}
		}

		// Sort each group by ID
		for key := range index {
			sort.Ints(index[key])
		}

		return index
	}
}

// NewSingleton creates singleton store pattern with sync.Once
func NewSingleton[S any](initFunc func() *S) func() *S {
	var store *S
	var once sync.Once

	return func() *S {
		once.Do(func() {
			store = initFunc()
		})
		return store
	}
}