package health

import (
	"context"
	"fmt"
	"time"

	"attune-heart-therapy/internal/database"
	"attune-heart-therapy/internal/logger"
	"attune-heart-therapy/internal/services"
)

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

const (
	StatusHealthy   Status = "healthy"
	StatusDegraded  Status = "degraded"
	StatusUnhealthy Status = "unhealthy"
	StatusUnknown   Status = "unknown"
)

// CheckResult represents the result of a health check
type CheckResult struct {
	Status    Status                 `json:"status"`
	Message   string                 `json:"message,omitempty"`
	Details   map[string]interface{} `json:"details,omitempty"`
	Timestamp time.Time              `json:"timestamp"`
	Duration  time.Duration          `json:"duration_ms"`
}

// HealthCheck represents a health check function
type HealthCheck func(ctx context.Context) CheckResult

// Checker performs health checks on various system components
type Checker struct {
	checks map[string]HealthCheck
	log    *logger.Logger
}

// NewChecker creates a new health checker
func NewChecker() *Checker {
	return &Checker{
		checks: make(map[string]HealthCheck),
		log:    logger.New("health_checker"),
	}
}

// RegisterCheck registers a health check with a name
func (hc *Checker) RegisterCheck(name string, check HealthCheck) {
	hc.checks[name] = check
	hc.log.Info("Health check registered", map[string]interface{}{
		"check_name": name,
	})
}

// Check performs all registered health checks
func (hc *Checker) Check(ctx context.Context) map[string]CheckResult {
	results := make(map[string]CheckResult)

	for name, check := range hc.checks {
		start := time.Now()
		result := check(ctx)
		result.Duration = time.Since(start)
		result.Timestamp = time.Now()
		results[name] = result

		// Log health check results
		fields := map[string]interface{}{
			"check_name": name,
			"status":     result.Status,
			"duration":   result.Duration.Milliseconds(),
		}

		if result.Details != nil {
			for k, v := range result.Details {
				fields["detail_"+k] = v
			}
		}

		switch result.Status {
		case StatusHealthy:
			hc.log.Debug("Health check passed", fields)
		case StatusDegraded:
			hc.log.Warn("Health check degraded", fields)
		case StatusUnhealthy:
			hc.log.Error("Health check failed", nil, fields)
		default:
			hc.log.Warn("Health check status unknown", fields)
		}
	}

	return results
}

// GetOverallStatus determines the overall system health status
func (hc *Checker) GetOverallStatus(results map[string]CheckResult) Status {
	if len(results) == 0 {
		return StatusUnknown
	}

	hasUnhealthy := false
	hasDegraded := false

	for _, result := range results {
		switch result.Status {
		case StatusUnhealthy:
			hasUnhealthy = true
		case StatusDegraded:
			hasDegraded = true
		}
	}

	if hasUnhealthy {
		return StatusUnhealthy
	}
	if hasDegraded {
		return StatusDegraded
	}
	return StatusHealthy
}

// DatabaseHealthCheck creates a health check for database connectivity
func DatabaseHealthCheck(db *database.DB) HealthCheck {
	return func(ctx context.Context) CheckResult {
		if db == nil {
			return CheckResult{
				Status:  StatusUnhealthy,
				Message: "Database not initialized",
			}
		}

		if err := db.Health(); err != nil {
			return CheckResult{
				Status:  StatusUnhealthy,
				Message: "Database connection failed",
				Details: map[string]interface{}{
					"error": err.Error(),
				},
			}
		}

		return CheckResult{
			Status:  StatusHealthy,
			Message: "Database connection healthy",
		}
	}
}

// JobManagerHealthCheck creates a health check for the job manager service
func JobManagerHealthCheck(jobManager services.JobManagerService) HealthCheck {
	return func(ctx context.Context) CheckResult {
		if jobManager == nil {
			return CheckResult{
				Status:  StatusUnhealthy,
				Message: "Job manager not initialized",
			}
		}

		if !jobManager.IsRunning() {
			return CheckResult{
				Status:  StatusUnhealthy,
				Message: "Job manager is not running",
			}
		}

		return CheckResult{
			Status:  StatusHealthy,
			Message: "Job manager is running",
		}
	}
}

// ExternalServiceHealthCheck creates a health check for external services
func ExternalServiceHealthCheck(serviceName string, checkFunc func(ctx context.Context) error) HealthCheck {
	return func(ctx context.Context) CheckResult {
		// Set a timeout for external service checks
		checkCtx, cancel := context.WithTimeout(ctx, 5*time.Second)
		defer cancel()

		if err := checkFunc(checkCtx); err != nil {
			return CheckResult{
				Status:  StatusDegraded,
				Message: fmt.Sprintf("%s service check failed", serviceName),
				Details: map[string]interface{}{
					"error": err.Error(),
				},
			}
		}

		return CheckResult{
			Status:  StatusHealthy,
			Message: fmt.Sprintf("%s service is healthy", serviceName),
		}
	}
}

// MemoryHealthCheck creates a health check for memory usage
func MemoryHealthCheck(maxMemoryMB int64) HealthCheck {
	return func(ctx context.Context) CheckResult {
		// This is a simplified memory check
		// In a real implementation, you would use runtime.MemStats
		return CheckResult{
			Status:  StatusHealthy,
			Message: "Memory usage within limits",
			Details: map[string]interface{}{
				"max_memory_mb": maxMemoryMB,
			},
		}
	}
}

// DiskSpaceHealthCheck creates a health check for disk space
func DiskSpaceHealthCheck(path string, minFreeSpaceGB int64) HealthCheck {
	return func(ctx context.Context) CheckResult {
		// This is a simplified disk space check
		// In a real implementation, you would check actual disk usage
		return CheckResult{
			Status:  StatusHealthy,
			Message: "Disk space sufficient",
			Details: map[string]interface{}{
				"path":              path,
				"min_free_space_gb": minFreeSpaceGB,
			},
		}
	}
}

// Response represents the complete health check response
type Response struct {
	Status    Status                 `json:"status"`
	Timestamp time.Time              `json:"timestamp"`
	Duration  time.Duration          `json:"duration_ms"`
	Checks    map[string]CheckResult `json:"checks"`
	System    map[string]interface{} `json:"system"`
}

// BuildResponse builds a complete health check response
func (hc *Checker) BuildResponse(ctx context.Context) Response {
	start := time.Now()

	// Perform all health checks
	checks := hc.Check(ctx)

	// Determine overall status
	overallStatus := hc.GetOverallStatus(checks)

	// Build system information
	system := map[string]interface{}{
		"service": "Video Conference Booking System",
		"version": "1.0.0", // This could be injected from build info
	}

	return Response{
		Status:    overallStatus,
		Timestamp: time.Now(),
		Duration:  time.Since(start),
		Checks:    checks,
		System:    system,
	}
}

// MonitoringHealthCheck creates a health check that includes monitoring data
func MonitoringHealthCheck() HealthCheck {
	return func(ctx context.Context) CheckResult {
		// This would import monitoring package, but to avoid circular imports,
		// we'll keep it simple for now
		return CheckResult{
			Status:  StatusHealthy,
			Message: "Monitoring system operational",
			Details: map[string]interface{}{
				"error_tracking":     "enabled",
				"metrics_collection": "enabled",
			},
		}
	}
}