package backbeat

import (
	"context"
	"fmt"
	"log/slog"
	"os"
	"time"

	"github.com/chorus-services/backbeat/pkg/sdk"
	"chorus/pkg/config"
)

// Integration manages CHORUS's integration with the BACKBEAT timing system
type Integration struct {
	client   sdk.Client
	config   *BackbeatConfig
	logger   Logger
	ctx      context.Context
	cancel   context.CancelFunc
	started  bool
	nodeID   string
	
	// P2P operation tracking
	activeOperations map[string]*P2POperation
}

// BackbeatConfig holds BACKBEAT-specific configuration
type BackbeatConfig struct {
	Enabled     bool   
	ClusterID   string 
	AgentID     string 
	NATSUrl     string 
}

// Logger interface for integration with CHORUS logging
type Logger interface {
	Info(msg string, args ...interface{})
	Warn(msg string, args ...interface{})
	Error(msg string, args ...interface{})
}

// P2POperation tracks a P2P coordination operation's progress through BACKBEAT
type P2POperation struct {
	ID          string
	Type        string // "election", "dht_store", "pubsub_sync", "peer_discovery"
	StartBeat   int64
	EstimatedBeats int
	Phase       OperationPhase
	PeerCount   int
	StartTime   time.Time
	Data        interface{}
}

// OperationPhase represents the current phase of a P2P operation
type OperationPhase int

const (
	PhaseStarted OperationPhase = iota
	PhaseConnecting
	PhaseNegotiating
	PhaseExecuting
	PhaseCompleted
	PhaseFailed
)

func (p OperationPhase) String() string {
	switch p {
	case PhaseStarted:
		return "started"
	case PhaseConnecting:
		return "connecting"
	case PhaseNegotiating:
		return "negotiating"
	case PhaseExecuting:
		return "executing"
	case PhaseCompleted:
		return "completed"
	case PhaseFailed:
		return "failed"
	default:
		return "unknown"
	}
}

// NewIntegration creates a new BACKBEAT integration for CHORUS
func NewIntegration(cfg *config.Config, nodeID string, logger Logger) (*Integration, error) {
	backbeatCfg := extractBackbeatConfig(cfg)
	
	if !backbeatCfg.Enabled {
		return nil, fmt.Errorf("BACKBEAT integration is disabled")
	}

	// Create BACKBEAT SDK config with slog logger
	sdkConfig := sdk.DefaultConfig()
	sdkConfig.ClusterID = backbeatCfg.ClusterID
	sdkConfig.AgentID = backbeatCfg.AgentID
	sdkConfig.NATSUrl = backbeatCfg.NATSUrl
	sdkConfig.Logger = slog.Default() // Use default slog logger

	// Create SDK client
	client := sdk.NewClient(sdkConfig)

	return &Integration{
		client:           client,
		config:           backbeatCfg,
		logger:           logger,
		nodeID:           nodeID,
		activeOperations: make(map[string]*P2POperation),
	}, nil
}

// extractBackbeatConfig extracts BACKBEAT configuration from CHORUS config
func extractBackbeatConfig(cfg *config.Config) *BackbeatConfig {
	return &BackbeatConfig{
		Enabled:   getEnvBool("CHORUS_BACKBEAT_ENABLED", true),
		ClusterID: getEnv("CHORUS_BACKBEAT_CLUSTER_ID", "chorus-production"),
		AgentID:   getEnv("CHORUS_BACKBEAT_AGENT_ID", fmt.Sprintf("chorus-%s", cfg.Agent.ID)),
		NATSUrl:   getEnv("CHORUS_BACKBEAT_NATS_URL", "nats://backbeat-nats:4222"),
	}
}

// Start initializes the BACKBEAT integration
func (i *Integration) Start(ctx context.Context) error {
	if i.started {
		return fmt.Errorf("integration already started")
	}

	i.ctx, i.cancel = context.WithCancel(ctx)

	// Start the SDK client
	if err := i.client.Start(i.ctx); err != nil {
		return fmt.Errorf("failed to start BACKBEAT client: %w", err)
	}

	// Register beat callbacks
	if err := i.client.OnBeat(i.onBeat); err != nil {
		return fmt.Errorf("failed to register beat callback: %w", err)
	}

	if err := i.client.OnDownbeat(i.onDownbeat); err != nil {
		return fmt.Errorf("failed to register downbeat callback: %w", err)
	}

	i.started = true
	i.logger.Info("🎵 CHORUS BACKBEAT integration started - cluster=%s agent=%s", 
		i.config.ClusterID, i.config.AgentID)

	return nil
}

// Stop gracefully shuts down the BACKBEAT integration
func (i *Integration) Stop() error {
	if !i.started {
		return nil
	}

	if i.cancel != nil {
		i.cancel()
	}

	if err := i.client.Stop(); err != nil {
		i.logger.Warn("⚠️ Error stopping BACKBEAT client: %v", err)
	}

	i.started = false
	i.logger.Info("🎵 CHORUS BACKBEAT integration stopped")
	return nil
}

// onBeat handles regular beat events from BACKBEAT
func (i *Integration) onBeat(beat sdk.BeatFrame) {
	i.logger.Info("🥁 BACKBEAT beat received - beat=%d phase=%s tempo=%d window=%s", 
		beat.BeatIndex, beat.Phase, beat.TempoBPM, beat.WindowID)

	// Emit status claim for active operations
	for _, op := range i.activeOperations {
		i.emitOperationStatus(op)
	}

	// Periodic health status emission
	if beat.BeatIndex%8 == 0 { // Every 8 beats (4 minutes at 2 BPM)
		i.emitHealthStatus()
	}
}

// onDownbeat handles downbeat (bar start) events
func (i *Integration) onDownbeat(beat sdk.BeatFrame) {
	i.logger.Info("🎼 BACKBEAT downbeat - new bar started - beat=%d window=%s", 
		beat.BeatIndex, beat.WindowID)

	// Cleanup completed operations on downbeat
	i.cleanupCompletedOperations()
}

// StartP2POperation registers a new P2P operation with BACKBEAT
func (i *Integration) StartP2POperation(operationID, operationType string, estimatedBeats int, data interface{}) error {
	if !i.started {
		return fmt.Errorf("BACKBEAT integration not started")
	}

	operation := &P2POperation{
		ID:             operationID,
		Type:           operationType,
		StartBeat:      i.client.GetCurrentBeat(),
		EstimatedBeats: estimatedBeats,
		Phase:          PhaseStarted,
		StartTime:      time.Now(),
		Data:           data,
	}

	i.activeOperations[operationID] = operation

	// Emit initial status claim
	return i.emitOperationStatus(operation)
}

// UpdateP2POperationPhase updates the phase of an active P2P operation
func (i *Integration) UpdateP2POperationPhase(operationID string, phase OperationPhase, peerCount int) error {
	operation, exists := i.activeOperations[operationID]
	if !exists {
		return fmt.Errorf("operation %s not found", operationID)
	}

	operation.Phase = phase
	operation.PeerCount = peerCount

	// Emit updated status claim
	return i.emitOperationStatus(operation)
}

// CompleteP2POperation marks a P2P operation as completed
func (i *Integration) CompleteP2POperation(operationID string, peerCount int) error {
	operation, exists := i.activeOperations[operationID]
	if !exists {
		return fmt.Errorf("operation %s not found", operationID)
	}

	operation.Phase = PhaseCompleted
	operation.PeerCount = peerCount

	// Emit completion status claim
	if err := i.emitOperationStatus(operation); err != nil {
		return err
	}

	// Remove from active operations
	delete(i.activeOperations, operationID)
	return nil
}

// FailP2POperation marks a P2P operation as failed
func (i *Integration) FailP2POperation(operationID string, reason string) error {
	operation, exists := i.activeOperations[operationID]
	if !exists {
		return fmt.Errorf("operation %s not found", operationID)
	}

	operation.Phase = PhaseFailed

	// Emit failure status claim
	claim := sdk.StatusClaim{
		State:     "failed",
		BeatsLeft: 0,
		Progress:  0.0,
		Notes:     fmt.Sprintf("P2P operation failed: %s (type: %s)", reason, operation.Type),
	}

	if err := i.client.EmitStatusClaim(claim); err != nil {
		return fmt.Errorf("failed to emit failure status: %w", err)
	}

	// Remove from active operations
	delete(i.activeOperations, operationID)
	return nil
}

// emitOperationStatus emits a status claim for a P2P operation
func (i *Integration) emitOperationStatus(operation *P2POperation) error {
	currentBeat := i.client.GetCurrentBeat()
	beatsPassed := currentBeat - operation.StartBeat
	beatsLeft := operation.EstimatedBeats - int(beatsPassed)
	if beatsLeft < 0 {
		beatsLeft = 0
	}

	progress := float64(beatsPassed) / float64(operation.EstimatedBeats)
	if progress > 1.0 {
		progress = 1.0
	}

	state := "executing"
	if operation.Phase == PhaseCompleted {
		state = "done"
		progress = 1.0
		beatsLeft = 0
	} else if operation.Phase == PhaseFailed {
		state = "failed"
		progress = 0.0
		beatsLeft = 0
	}

	claim := sdk.StatusClaim{
		TaskID:    operation.ID,
		State:     state,
		BeatsLeft: beatsLeft,
		Progress:  progress,
		Notes:     fmt.Sprintf("P2P %s: %s (peers: %d, node: %s)", 
			operation.Type, operation.Phase.String(), operation.PeerCount, i.nodeID),
	}

	return i.client.EmitStatusClaim(claim)
}

// emitHealthStatus emits a general health status claim
func (i *Integration) emitHealthStatus() error {
	health := i.client.Health()
	
	state := "waiting"
	if len(i.activeOperations) > 0 {
		state = "executing"
	}

	notes := fmt.Sprintf("CHORUS P2P healthy: connected=%v, operations=%d, tempo=%d BPM, node=%s", 
		health.Connected, len(i.activeOperations), health.CurrentTempo, i.nodeID)
	
	if len(health.Errors) > 0 {
		state = "failed"
		notes += fmt.Sprintf(", errors: %d", len(health.Errors))
	}

	claim := sdk.StatusClaim{
		TaskID:    "chorus-p2p-health",
		State:     state,
		BeatsLeft: 0,
		Progress:  1.0,
		Notes:     notes,
	}

	return i.client.EmitStatusClaim(claim)
}

// cleanupCompletedOperations removes old completed operations
func (i *Integration) cleanupCompletedOperations() {
	// This is called on downbeat, cleanup already happens in CompleteP2POperation/FailP2POperation
	i.logger.Info("🧹 BACKBEAT operations cleanup check - active: %d", len(i.activeOperations))
}

// GetHealth returns the current BACKBEAT integration health
func (i *Integration) GetHealth() map[string]interface{} {
	if !i.started {
		return map[string]interface{}{
			"enabled":   i.config.Enabled,
			"started":   false,
			"connected": false,
		}
	}

	health := i.client.Health()
	return map[string]interface{}{
		"enabled":            i.config.Enabled,
		"started":            i.started,
		"connected":          health.Connected,
		"current_beat":       health.LastBeat,
		"current_tempo":      health.CurrentTempo,
		"measured_bpm":       health.MeasuredBPM,
		"tempo_drift":        health.TempoDrift.String(),
		"reconnect_count":    health.ReconnectCount,
		"active_operations":  len(i.activeOperations),
		"local_degradation":  health.LocalDegradation,
		"errors":             health.Errors,
		"node_id":            i.nodeID,
	}
}

// ExecuteWithBeatBudget executes a function with a BACKBEAT beat budget
func (i *Integration) ExecuteWithBeatBudget(beats int, fn func() error) error {
	if !i.started {
		return fn() // Fall back to regular execution if not started
	}

	return i.client.WithBeatBudget(beats, fn)
}


// Utility functions for environment variable handling
func getEnv(key, defaultValue string) string {
	if value := os.Getenv(key); value != "" {
		return value
	}
	return defaultValue
}

func getEnvBool(key string, defaultValue bool) bool {
	value := os.Getenv(key)
	if value == "" {
		return defaultValue
	}
	return value == "true" || value == "1" || value == "yes" || value == "on"
}