package monitoring

import (
	"context"
	"time"

	"github.com/atlasos/calypso/internal/common/database"
	"github.com/atlasos/calypso/internal/common/logger"
)

// HealthStatus represents the health status of a component
type HealthStatus string

const (
	HealthStatusHealthy   HealthStatus = "healthy"
	HealthStatusDegraded   HealthStatus = "degraded"
	HealthStatusUnhealthy  HealthStatus = "unhealthy"
	HealthStatusUnknown    HealthStatus = "unknown"
)

// ComponentHealth represents the health of a system component
type ComponentHealth struct {
	Name      string       `json:"name"`
	Status    HealthStatus `json:"status"`
	Message   string       `json:"message,omitempty"`
	Timestamp time.Time    `json:"timestamp"`
}

// EnhancedHealth represents enhanced health check response
type EnhancedHealth struct {
	Status     string            `json:"status"`
	Service    string            `json:"service"`
	Version    string            `json:"version,omitempty"`
	Uptime     int64             `json:"uptime_seconds"`
	Components []ComponentHealth `json:"components"`
	Timestamp  time.Time         `json:"timestamp"`
}

// HealthService provides enhanced health checking
type HealthService struct {
	db         *database.DB
	logger     *logger.Logger
	startTime  time.Time
	metricsService *MetricsService
}

// NewHealthService creates a new health service
func NewHealthService(db *database.DB, log *logger.Logger, metricsService *MetricsService) *HealthService {
	return &HealthService{
		db:            db,
		logger:        log,
		startTime:     time.Now(),
		metricsService: metricsService,
	}
}

// CheckHealth performs a comprehensive health check
func (s *HealthService) CheckHealth(ctx context.Context) *EnhancedHealth {
	health := &EnhancedHealth{
		Status:    string(HealthStatusHealthy),
		Service:   "calypso-api",
		Uptime:    int64(time.Since(s.startTime).Seconds()),
		Timestamp: time.Now(),
		Components: []ComponentHealth{},
	}

	// Check database
	dbHealth := s.checkDatabase(ctx)
	health.Components = append(health.Components, dbHealth)

	// Check storage
	storageHealth := s.checkStorage(ctx)
	health.Components = append(health.Components, storageHealth)

	// Check SCST
	scstHealth := s.checkSCST(ctx)
	health.Components = append(health.Components, scstHealth)

	// Determine overall status
	hasUnhealthy := false
	hasDegraded := false
	for _, comp := range health.Components {
		if comp.Status == HealthStatusUnhealthy {
			hasUnhealthy = true
		} else if comp.Status == HealthStatusDegraded {
			hasDegraded = true
		}
	}

	if hasUnhealthy {
		health.Status = string(HealthStatusUnhealthy)
	} else if hasDegraded {
		health.Status = string(HealthStatusDegraded)
	}

	return health
}

// checkDatabase checks database health
func (s *HealthService) checkDatabase(ctx context.Context) ComponentHealth {
	ctx, cancel := context.WithTimeout(ctx, 5*time.Second)
	defer cancel()

	if err := s.db.PingContext(ctx); err != nil {
		return ComponentHealth{
			Name:      "database",
			Status:    HealthStatusUnhealthy,
			Message:   "Database connection failed: " + err.Error(),
			Timestamp: time.Now(),
		}
	}

	// Check if we can query
	var count int
	if err := s.db.QueryRowContext(ctx, "SELECT 1").Scan(&count); err != nil {
		return ComponentHealth{
			Name:      "database",
			Status:    HealthStatusDegraded,
			Message:   "Database query failed: " + err.Error(),
			Timestamp: time.Now(),
		}
	}

	return ComponentHealth{
		Name:      "database",
		Status:    HealthStatusHealthy,
		Timestamp: time.Now(),
	}
}

// checkStorage checks storage component health
func (s *HealthService) checkStorage(ctx context.Context) ComponentHealth {
	// Check if we have any active repositories
	var count int
	if err := s.db.QueryRowContext(ctx, "SELECT COUNT(*) FROM disk_repositories WHERE is_active = true").Scan(&count); err != nil {
		return ComponentHealth{
			Name:      "storage",
			Status:    HealthStatusDegraded,
			Message:   "Failed to query storage repositories",
			Timestamp: time.Now(),
		}
	}

	if count == 0 {
		return ComponentHealth{
			Name:      "storage",
			Status:    HealthStatusDegraded,
			Message:   "No active storage repositories configured",
			Timestamp: time.Now(),
		}
	}

	// Check repository capacity
	var usagePercent float64
	query := `
		SELECT COALESCE(
			SUM(used_bytes)::float / NULLIF(SUM(total_bytes), 0) * 100,
			0
		)
		FROM disk_repositories
		WHERE is_active = true
	`
	if err := s.db.QueryRowContext(ctx, query).Scan(&usagePercent); err == nil {
		if usagePercent > 95 {
			return ComponentHealth{
				Name:      "storage",
				Status:    HealthStatusDegraded,
				Message:   "Storage repositories are nearly full",
				Timestamp: time.Now(),
			}
		}
	}

	return ComponentHealth{
		Name:      "storage",
		Status:    HealthStatusHealthy,
		Timestamp: time.Now(),
	}
}

// checkSCST checks SCST component health
func (s *HealthService) checkSCST(ctx context.Context) ComponentHealth {
	// Check if SCST targets exist
	var count int
	if err := s.db.QueryRowContext(ctx, "SELECT COUNT(*) FROM scst_targets").Scan(&count); err != nil {
		return ComponentHealth{
			Name:      "scst",
			Status:    HealthStatusUnknown,
			Message:   "Failed to query SCST targets",
			Timestamp: time.Now(),
		}
	}

	// SCST is healthy if we can query it (even if no targets exist)
	return ComponentHealth{
		Name:      "scst",
		Status:    HealthStatusHealthy,
		Timestamp: time.Now(),
	}
}