// Package scheduler provides HTTP handlers for scheduler management
package scheduler

import (
	"encoding/json"
	"fmt"
	"net/http"
	"time"

	"github.com/jfraeys/fetch_ml/internal/api/errors"
	"github.com/jfraeys/fetch_ml/internal/auth"
	"github.com/jfraeys/fetch_ml/internal/logging"
	sch "github.com/jfraeys/fetch_ml/internal/scheduler"
)

// APIHandler provides scheduler-related HTTP API handlers
type APIHandler struct {
	logger    *logging.Logger
	hub       *sch.SchedulerHub
	streaming map[string][]chan StreamingEvent
}

// NewHandler creates a new scheduler API handler
func NewHandler(hub *sch.SchedulerHub, logger *logging.Logger, authConfig *auth.Config) *APIHandler {
	return &APIHandler{
		logger:    logger,
		hub:       hub,
		streaming: make(map[string][]chan StreamingEvent),
	}
}

// StreamingEvent represents an event for SSE streaming
type StreamingEvent struct {
	Type    string          `json:"type"`
	Payload json.RawMessage `json:"payload"`
}

// WorkerInfo represents worker information for API responses
type WorkerInfo struct {
	ID            string                 `json:"id"`
	ConnectedAt   time.Time              `json:"connected_at"`
	LastHeartbeat time.Time              `json:"last_heartbeat,omitempty"`
	Capabilities  sch.WorkerCapabilities `json:"capabilities"`
	Slots         sch.SlotStatus         `json:"slots"`
	ActiveTasks   []string               `json:"active_tasks"`
	Status        string                 `json:"status"` // active, draining, offline
}

// SchedulerStatus represents scheduler status for API responses
type SchedulerStatus struct {
	WorkersTotal       int       `json:"workers_total"`
	WorkersActive      int       `json:"workers_active"`
	WorkersDraining    int       `json:"workers_draining"`
	BatchQueueDepth    int       `json:"batch_queue_depth"`
	ServiceQueueDepth  int       `json:"service_queue_depth"`
	TasksRunning       int       `json:"tasks_running"`
	TasksCompleted24h  int       `json:"tasks_completed_24h"`
	ReservationsActive int       `json:"reservations_active"`
	Timestamp          time.Time `json:"timestamp"`
}

// ReservationInfo represents reservation information for API responses
type ReservationInfo struct {
	ID        string    `json:"id"`
	UserID    string    `json:"user_id"`
	GPUCount  int       `json:"gpu_count"`
	GPUType   string    `json:"gpu_type,omitempty"`
	NodeCount int       `json:"node_count"`
	ExpiresAt time.Time `json:"expires_at"`
	Status    string    `json:"status"` // active, claimed, expired
}

// CreateReservationRequest represents a request to create a reservation
type CreateReservationRequest struct {
	GPUCount       int    `json:"gpu_count"`
	GPUType        string `json:"gpu_type,omitempty"`
	NodeCount      int    `json:"node_count,omitempty"`
	ExpiresMinutes int    `json:"expires_minutes,omitempty"`
}

// NewAPIHandler creates a new scheduler API handler
func NewAPIHandler(logger *logging.Logger, hub *sch.SchedulerHub) *APIHandler {
	handler := &APIHandler{
		logger:    logger,
		hub:       hub,
		streaming: make(map[string][]chan StreamingEvent),
	}
	return handler
}

// GetV1SchedulerStatus handles GET /v1/scheduler/status
func (h *APIHandler) GetV1SchedulerStatus(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:read") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	if h.hub == nil {
		errors.WriteHTTPError(w, http.StatusServiceUnavailable, errors.CodeServiceUnavailable, "Scheduler not available", "")
		return
	}

	// Get metrics from hub
	metrics := h.hub.GetMetricsPayload()

	status := SchedulerStatus{
		Timestamp: time.Now().UTC(),
	}

	// Extract values from metrics payload
	if v, ok := metrics["workers_connected"].(int); ok {
		status.WorkersTotal = v
		status.WorkersActive = v // Simplified - all connected are active
	}
	if v, ok := metrics["queue_depth_batch"].(int); ok {
		status.BatchQueueDepth = v
	}
	if v, ok := metrics["queue_depth_service"].(int); ok {
		status.ServiceQueueDepth = v
	}
	if v, ok := metrics["jobs_completed"].(int); ok {
		status.TasksCompleted24h = v
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(status); err != nil {
		h.logger.Warn("failed to encode status", "error", err)
	}
}

// GetV1SchedulerWorkers handles GET /v1/scheduler/workers
func (h *APIHandler) GetV1SchedulerWorkers(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:read") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	if h.hub == nil {
		errors.WriteHTTPError(w, http.StatusServiceUnavailable, errors.CodeServiceUnavailable, "Scheduler not available", "")
		return
	}

	// Get worker slots from metrics
	metrics := h.hub.GetMetricsPayload()
	slots, _ := metrics["worker_slots"].(map[string]sch.SlotStatus)

	workers := []WorkerInfo{}

	// Build worker list from slots data
	for workerID, slotStatus := range slots {
		worker := WorkerInfo{
			ID:           workerID,
			Slots:        slotStatus,
			Capabilities: sch.WorkerCapabilities{},
			Status:       "active",
			ActiveTasks:  []string{},
		}
		workers = append(workers, worker)
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(workers); err != nil {
		h.logger.Warn("failed to encode workers", "error", err)
	}
}

// GetV1SchedulerWorkersWorkerID handles GET /v1/scheduler/workers/{workerId}
func (h *APIHandler) GetV1SchedulerWorkersWorkerID(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:read") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	if h.hub == nil {
		errors.WriteHTTPError(w, http.StatusServiceUnavailable, errors.CodeServiceUnavailable, "Scheduler not available", "")
		return
	}

	workerID := r.PathValue("workerId")
	if workerID == "" {
		errors.WriteHTTPError(w, http.StatusBadRequest, errors.CodeInvalidRequest, "Missing worker ID", "")
		return
	}

	// Get worker slots from metrics
	metrics := h.hub.GetMetricsPayload()
	slots, _ := metrics["worker_slots"].(map[string]sch.SlotStatus)

	slotStatus, ok := slots[workerID]
	if !ok {
		errors.WriteHTTPError(w, http.StatusNotFound, errors.CodeNotFound, "Worker not found", "")
		return
	}

	worker := WorkerInfo{
		ID:           workerID,
		Slots:        slotStatus,
		Capabilities: sch.WorkerCapabilities{},
		Status:       "active",
		ActiveTasks:  []string{},
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(worker); err != nil {
		h.logger.Warn("failed to encode worker", "error", err)
	}
}

// DeleteV1SchedulerWorkersWorkerID handles DELETE /v1/scheduler/workers/{workerId}
func (h *APIHandler) DeleteV1SchedulerWorkersWorkerID(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:drain") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	if h.hub == nil {
		errors.WriteHTTPError(w, http.StatusServiceUnavailable, errors.CodeServiceUnavailable, "Scheduler not available", "")
		return
	}

	workerID := r.PathValue("workerId")
	if workerID == "" {
		errors.WriteHTTPError(w, http.StatusBadRequest, errors.CodeInvalidRequest, "Missing worker ID", "")
		return
	}

	h.logger.Info("draining worker", "worker_id", workerID, "user", user.Name)

	// Note: Actual drain implementation would involve signaling the worker
	// and waiting for tasks to complete. This is a simplified version.

	w.WriteHeader(http.StatusNoContent)
}

// GetV1SchedulerReservations handles GET /v1/scheduler/reservations
func (h *APIHandler) GetV1SchedulerReservations(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:read") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	if h.hub == nil {
		errors.WriteHTTPError(w, http.StatusServiceUnavailable, errors.CodeServiceUnavailable, "Scheduler not available", "")
		return
	}

	// Return empty list for now - reservations would be tracked in hub
	reservations := []ReservationInfo{}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(reservations); err != nil {
		h.logger.Warn("failed to encode reservations", "error", err)
	}
}

// PostV1SchedulerReservations handles POST /v1/scheduler/reservations
func (h *APIHandler) PostV1SchedulerReservations(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:write") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	if h.hub == nil {
		errors.WriteHTTPError(w, http.StatusServiceUnavailable, errors.CodeServiceUnavailable, "Scheduler not available", "")
		return
	}

	var req CreateReservationRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		errors.WriteHTTPError(w, http.StatusBadRequest, errors.CodeInvalidRequest, "Invalid request body", "")
		return
	}

	if req.GPUCount <= 0 {
		errors.WriteHTTPError(w, http.StatusUnprocessableEntity, errors.CodeInvalidRequest, "GPU count must be positive", "")
		return
	}

	if req.NodeCount <= 0 {
		req.NodeCount = 1
	}
	if req.ExpiresMinutes <= 0 {
		req.ExpiresMinutes = 30
	}

	reservation := ReservationInfo{
		ID:        fmt.Sprintf("res-%d", time.Now().UnixNano()),
		UserID:    user.Name,
		GPUCount:  req.GPUCount,
		GPUType:   req.GPUType,
		NodeCount: req.NodeCount,
		ExpiresAt: time.Now().Add(time.Duration(req.ExpiresMinutes) * time.Minute),
		Status:    "active",
	}

	h.logger.Info("created reservation", "reservation_id", reservation.ID, "user", user.Name)

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusCreated)
	if err := json.NewEncoder(w).Encode(reservation); err != nil {
		h.logger.Warn("failed to encode reservation", "error", err)
	}
}

// PatchV1SchedulerJobsJobIDPriority handles PATCH /v1/scheduler/jobs/{jobId}/priority
func (h *APIHandler) PatchV1SchedulerJobsJobIDPriority(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "tasks:priority") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	if h.hub == nil {
		errors.WriteHTTPError(w, http.StatusServiceUnavailable, errors.CodeServiceUnavailable, "Scheduler not available", "")
		return
	}

	jobID := r.PathValue("jobId")
	if jobID == "" {
		errors.WriteHTTPError(w, http.StatusBadRequest, errors.CodeInvalidRequest, "Missing job ID", "")
		return
	}

	var req struct {
		Priority int `json:"priority"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		errors.WriteHTTPError(w, http.StatusBadRequest, errors.CodeInvalidRequest, "Invalid request body", "")
		return
	}

	if req.Priority < 1 || req.Priority > 10 {
		errors.WriteHTTPError(w, http.StatusUnprocessableEntity, errors.CodeInvalidRequest, "Priority must be between 1 and 10", "")
		return
	}

	h.logger.Info("updating job priority", "job_id", jobID, "priority", req.Priority, "user", user.Name)

	// Note: Actual priority update would modify the task in the queue
	// This is a simplified version

	response := map[string]any{
		"id":       jobID,
		"priority": req.Priority,
		"status":   "queued",
	}

	w.Header().Set("Content-Type", "application/json")
	if err := json.NewEncoder(w).Encode(response); err != nil {
		h.logger.Warn("failed to encode priority response", "error", err)
	}
}

// GetV1SchedulerStatusStream handles GET /v1/scheduler/status/stream (SSE)
func (h *APIHandler) GetV1SchedulerStatusStream(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:read") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	// Set SSE headers
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")

	// Create event channel for this client
	eventChan := make(chan StreamingEvent, 10)
	clientID := fmt.Sprintf("%s-%d", user.Name, time.Now().UnixNano())
	h.streaming[clientID] = append(h.streaming[clientID], eventChan)

	// Clean up on disconnect
	defer func() {
		delete(h.streaming, clientID)
		close(eventChan)
	}()

	// Send initial status
	status := map[string]any{
		"type":      "connected",
		"timestamp": time.Now().UTC(),
	}
	data, _ := json.Marshal(status)
	fmt.Fprintf(w, "data: %s\n\n", data)
	w.(http.Flusher).Flush()

	// Keep connection alive and send periodic updates
	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-r.Context().Done():
			return
		case <-ticker.C:
			heartbeat := map[string]any{
				"type":      "heartbeat",
				"timestamp": time.Now().UTC(),
			}
			data, _ := json.Marshal(heartbeat)
			fmt.Fprintf(w, "data: %s\n\n", data)
			w.(http.Flusher).Flush()
		case event := <-eventChan:
			data, _ := json.Marshal(event)
			fmt.Fprintf(w, "data: %s\n\n", data)
			w.(http.Flusher).Flush()
		}
	}
}

// GetV1SchedulerJobsJobIDStream handles GET /v1/scheduler/jobs/{jobId}/stream (SSE)
func (h *APIHandler) GetV1SchedulerJobsJobIDStream(w http.ResponseWriter, r *http.Request) {
	user := auth.GetUserFromContext(r.Context())
	if !h.checkPermission(user, "scheduler:read") {
		errors.WriteHTTPError(w, http.StatusForbidden, errors.CodePermissionDenied, "Insufficient permissions", "")
		return
	}

	jobID := r.PathValue("jobId")
	if jobID == "" {
		errors.WriteHTTPError(w, http.StatusBadRequest, errors.CodeInvalidRequest, "Missing job ID", "")
		return
	}

	// Set SSE headers
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")

	// Send initial status
	response := map[string]any{
		"type":      "connected",
		"job_id":    jobID,
		"timestamp": time.Now().UTC(),
	}
	data, _ := json.Marshal(response)
	fmt.Fprintf(w, "data: %s\n\n", data)
	w.(http.Flusher).Flush()

	// Keep connection alive
	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case <-r.Context().Done():
			return
		case <-ticker.C:
			heartbeat := map[string]any{
				"type":      "heartbeat",
				"timestamp": time.Now().UTC(),
			}
			data, _ := json.Marshal(heartbeat)
			fmt.Fprintf(w, "data: %s\n\n", data)
			w.(http.Flusher).Flush()
		}
	}
}

// checkPermission checks if the user has the required permission
func (h *APIHandler) checkPermission(user *auth.User, permission string) bool {
	if user == nil {
		return false
	}

	// Admin has all permissions
	if user.Admin {
		return true
	}

	// Check specific permission
	return user.HasPermission(permission)
}