// Package memory provides a worker for memory background tasks.
package memory

import (
	"context"
	"log/slog"
	"sync"
	"time"
)

// MemoryWorker is a background worker that handles memory operations.
// It can be integrated with the agent's worker pool.
type MemoryWorker struct {
	mu sync.Mutex

	// integration provides memory operations
	integration *AgentMemoryIntegration

	// stopChan signals the worker to stop
	stopChan chan struct{}

	// doneChan signals the worker has stopped
	doneChan chan struct{}

	// running indicates if the worker is active
	running bool

	// logger for worker events
	logger *slog.Logger

	// workQueue for async memory operations
	workQueue chan MemoryWorkItem

	// workerCount for parallel processing
	workerCount int
}

// MemoryWorkItem represents a unit of work for the memory worker
type MemoryWorkItem struct {
	// Type of work
	Type WorkItemType

	// Context for the operation
	Ctx context.Context

	// Data for the operation
	Data interface{}

	// ResultChan for async results
	ResultChan chan<- WorkResult
}

// WorkItemType defines the type of memory work
type WorkItemType int

const (
	WorkStoreEntry WorkItemType = iota
	WorkStoreBatch
	WorkConsolidate
	WorkApplyTTL
	WorkDeleteUserData
)

// WorkResult contains the result of a work item
type WorkResult struct {
	Success bool
	Error   error
	Data    interface{}
}

// NewMemoryWorker creates a new memory worker
func NewMemoryWorker(integration *AgentMemoryIntegration, workerCount int) *MemoryWorker {
	if workerCount <= 0 {
		workerCount = 4
	}

	return &MemoryWorker{
		integration: integration,
		stopChan:    make(chan struct{}),
		doneChan:    make(chan struct{}),
		logger:      slog.Default().With("component", "memory-worker"),
		workQueue:   make(chan MemoryWorkItem, 1000),
		workerCount: workerCount,
	}
}

// Start starts the memory worker
func (w *MemoryWorker) Start() {
	w.mu.Lock()
	if w.running {
		w.mu.Unlock()
		return
	}
	w.running = true
	w.mu.Unlock()

	// Start the integration (consolidation worker, etc.)
	w.integration.Start()

	// Start worker goroutines
	var wg sync.WaitGroup
	for i := 0; i < w.workerCount; i++ {
		wg.Add(1)
		go func(id int) {
			defer wg.Done()
			w.runWorker(id)
		}(i)
	}

	// Wait for all workers to finish
	go func() {
		wg.Wait()
		close(w.doneChan)
	}()

	w.logger.Info("memory worker started", "workers", w.workerCount)
}

// Stop stops the memory worker
func (w *MemoryWorker) Stop() error {
	w.mu.Lock()
	if !w.running {
		w.mu.Unlock()
		return nil
	}
	w.running = false
	w.mu.Unlock()

	close(w.stopChan)
	<-w.doneChan

	// Stop the integration
	return w.integration.Stop()
}

// runWorker processes work items
func (w *MemoryWorker) runWorker(id int) {
	w.logger.Debug("worker started", "id", id)

	for {
		select {
		case <-w.stopChan:
			w.logger.Debug("worker stopping", "id", id)
			return

		case item := <-w.workQueue:
			w.processWorkItem(item)
		}
	}
}

// processWorkItem handles a single work item
func (w *MemoryWorker) processWorkItem(item MemoryWorkItem) {
	var result WorkResult

	switch item.Type {
	case WorkStoreEntry:
		if entry, ok := item.Data.(*MemoryEntry); ok {
			err := w.integration.orchestrator.Store(item.Ctx, entry)
			result = WorkResult{Success: err == nil, Error: err}
		}

	case WorkStoreBatch:
		if entries, ok := item.Data.([]*MemoryEntry); ok {
			err := w.integration.orchestrator.BatchStore(item.Ctx, entries)
			result = WorkResult{Success: err == nil, Error: err}
		}

	case WorkConsolidate:
		if sessionID, ok := item.Data.(string); ok {
			err := w.integration.ConsolidateSession(item.Ctx, sessionID)
			result = WorkResult{Success: err == nil, Error: err}
		}

	case WorkApplyTTL:
		deleted, err := w.integration.orchestrator.backend.ApplyTTL(item.Ctx)
		result = WorkResult{Success: err == nil, Error: err, Data: deleted}

	case WorkDeleteUserData:
		if req, ok := item.Data.(*DeleteUserDataRequest); ok {
			err := w.integration.DeleteUserData(item.Ctx, req.UserID, req.RequestedBy)
			result = WorkResult{Success: err == nil, Error: err}
		}
	}

	// Send result if channel provided
	if item.ResultChan != nil {
		select {
		case item.ResultChan <- result:
		default:
			// Channel full or closed
		}
	}
}

// DeleteUserDataRequest holds data for user deletion
type DeleteUserDataRequest struct {
	UserID      string
	RequestedBy string
}

// SubmitWork submits a work item to the queue
func (w *MemoryWorker) SubmitWork(item MemoryWorkItem) bool {
	select {
	case w.workQueue <- item:
		return true
	default:
		return false // Queue full
	}
}

// SubmitWorkWithResult submits work and waits for result
func (w *MemoryWorker) SubmitWorkWithResult(ctx context.Context, item MemoryWorkItem) (WorkResult, error) {
	resultChan := make(chan WorkResult, 1)
	item.ResultChan = resultChan
	item.Ctx = ctx

	if !w.SubmitWork(item) {
		return WorkResult{}, context.DeadlineExceeded
	}

	select {
	case <-ctx.Done():
		return WorkResult{}, ctx.Err()
	case result := <-resultChan:
		return result, nil
	}
}

// AsyncStoreEntry submits an entry for async storage
func (w *MemoryWorker) AsyncStoreEntry(ctx context.Context, entry *MemoryEntry) bool {
	return w.SubmitWork(MemoryWorkItem{
		Type: WorkStoreEntry,
		Ctx:  ctx,
		Data: entry,
	})
}

// AsyncStoreBatch submits entries for async batch storage
func (w *MemoryWorker) AsyncStoreBatch(ctx context.Context, entries []*MemoryEntry) bool {
	return w.SubmitWork(MemoryWorkItem{
		Type: WorkStoreBatch,
		Ctx:  ctx,
		Data: entries,
	})
}

// AsyncConsolidate submits a session for async consolidation
func (w *MemoryWorker) AsyncConsolidate(ctx context.Context, sessionID string) bool {
	return w.SubmitWork(MemoryWorkItem{
		Type: WorkConsolidate,
		Ctx:  ctx,
		Data: sessionID,
	})
}

// AsyncDeleteUserData submits a user data deletion request
func (w *MemoryWorker) AsyncDeleteUserData(ctx context.Context, userID, requestedBy string) bool {
	return w.SubmitWork(MemoryWorkItem{
		Type: WorkDeleteUserData,
		Ctx:  ctx,
		Data: &DeleteUserDataRequest{UserID: userID, RequestedBy: requestedBy},
	})
}

// QueueLength returns the current queue length
func (w *MemoryWorker) QueueLength() int {
	return len(w.workQueue)
}

// IsRunning returns whether the worker is running
func (w *MemoryWorker) IsRunning() bool {
	w.mu.Lock()
	defer w.mu.Unlock()
	return w.running
}

// WorkerPoolIntegration provides an interface compatible with common worker pools
type WorkerPoolIntegration struct {
	worker *MemoryWorker
}

// NewWorkerPoolIntegration creates a new worker pool integration
func NewWorkerPoolIntegration(worker *MemoryWorker) *WorkerPoolIntegration {
	return &WorkerPoolIntegration{worker: worker}
}

// Name returns the worker name
func (w *WorkerPoolIntegration) Name() string {
	return "memory-worker"
}

// Start starts the worker
func (w *WorkerPoolIntegration) Start(ctx context.Context) error {
	w.worker.Start()
	return nil
}

// Stop stops the worker
func (w *WorkerPoolIntegration) Stop(ctx context.Context) error {
	return w.worker.Stop()
}

// Health returns the health status
func (w *WorkerPoolIntegration) Health() error {
	if !w.worker.IsRunning() {
		return context.Canceled
	}
	return nil
}

// Metrics returns worker metrics
func (w *WorkerPoolIntegration) Metrics() map[string]interface{} {
	metrics := w.worker.integration.GetMetrics()
	return map[string]interface{}{
		"total_queries":           metrics.TotalQueries,
		"total_stores":            metrics.TotalStores,
		"avg_retrieval_ms":        metrics.AvgRetrievalMs,
		"consolidation_runs":      metrics.ConsolidationRuns,
		"queue_length":            w.worker.QueueLength(),
		"active_working_memories": metrics.ActiveWorkingMemories,
	}
}

// HealthCheckTask performs periodic health checks
type HealthCheckTask struct {
	integration *AgentMemoryIntegration
	interval    time.Duration
	stopChan    chan struct{}
}

// NewHealthCheckTask creates a new health check task
func NewHealthCheckTask(integration *AgentMemoryIntegration, interval time.Duration) *HealthCheckTask {
	if interval <= 0 {
		interval = 30 * time.Second
	}
	return &HealthCheckTask{
		integration: integration,
		interval:    interval,
		stopChan:    make(chan struct{}),
	}
}

// Start starts the health check task
func (h *HealthCheckTask) Start() {
	go func() {
		ticker := time.NewTicker(h.interval)
		defer ticker.Stop()

		for {
			select {
			case <-h.stopChan:
				return
			case <-ticker.C:
				metrics := h.integration.GetMetrics()
				slog.Info("memory health check",
					"active_memories", metrics.ActiveWorkingMemories,
					"total_queries", metrics.TotalQueries,
					"avg_retrieval_ms", metrics.AvgRetrievalMs)
			}
		}
	}()
}

// Stop stops the health check task
func (h *HealthCheckTask) Stop() {
	close(h.stopChan)
}