// Package tracing provides distributed tracing for the KnowFoolery application.
package tracing

import (
	"context"
	"fmt"
)

// Config holds the configuration for the tracer.
type Config struct {
	ServiceName    string
	ServiceVersion string
	Environment    string
	JaegerEndpoint string
	SampleRate     float64
	Enabled        bool
}

// DefaultConfig returns a default configuration.
func DefaultConfig() Config {
	return Config{
		ServiceName:    "knowfoolery",
		ServiceVersion: "0.0.0",
		Environment:    "development",
		JaegerEndpoint: "http://localhost:14268/api/traces",
		SampleRate:     1.0, // Sample all traces in development
		Enabled:        false,
	}
}

// Tracer provides distributed tracing functionality.
// This is a placeholder that should be implemented with OpenTelemetry.
type Tracer struct {
	config Config
}

// NewTracer creates a new Tracer.
// Note: Actual implementation should use OpenTelemetry SDK.
func NewTracer(config Config) (*Tracer, error) {
	if !config.Enabled {
		return &Tracer{config: config}, nil
	}

	// TODO: Initialize OpenTelemetry tracer provider
	// Example implementation:
	// - Create Jaeger exporter
	// - Create tracer provider with batching
	// - Set global tracer provider
	// - Configure resource with service info

	return &Tracer{config: config}, nil
}

// Shutdown gracefully shuts down the tracer.
func (t *Tracer) Shutdown(ctx context.Context) error {
	if !t.config.Enabled {
		return nil
	}

	// TODO: Shutdown tracer provider
	return nil
}

// StartSpan starts a new span.
// This is a placeholder that should be implemented with OpenTelemetry.
func (t *Tracer) StartSpan(ctx context.Context, name string) (context.Context, Span) {
	// TODO: Start actual OpenTelemetry span
	return ctx, &noopSpan{}
}

// Span represents a tracing span.
type Span interface {
	// End ends the span.
	End()
	// SetAttribute sets an attribute on the span.
	SetAttribute(key string, value interface{})
	// RecordError records an error on the span.
	RecordError(err error)
}

// noopSpan is a no-op implementation of Span.
type noopSpan struct{}

func (s *noopSpan) End()                                       {}
func (s *noopSpan) SetAttribute(key string, value interface{}) {}
func (s *noopSpan) RecordError(err error)                      {}

// TraceServiceOperation traces a service operation.
func TraceServiceOperation(ctx context.Context, tracer *Tracer, serviceName,
	operation string, fn func(context.Context) error) error {

	ctx, span := tracer.StartSpan(ctx, fmt.Sprintf("%s.%s", serviceName, operation))
	defer span.End()

	err := fn(ctx)
	if err != nil {
		span.RecordError(err)
		span.SetAttribute("error", true)
	}

	return err
}

// TraceDatabaseOperation traces a database operation.
func TraceDatabaseOperation(ctx context.Context, tracer *Tracer, operation,
	table string, fn func(context.Context) error) error {

	ctx, span := tracer.StartSpan(ctx, fmt.Sprintf("db.%s.%s", operation, table))
	defer span.End()

	span.SetAttribute("db.operation", operation)
	span.SetAttribute("db.table", table)
	span.SetAttribute("db.system", "postgresql")

	err := fn(ctx)
	if err != nil {
		span.RecordError(err)
	}

	return err
}

// ConfigFromEnv creates a Config from environment variables.
func ConfigFromEnv() Config {
	// TODO: Implement environment variable parsing
	return DefaultConfig()
}