package unitel

import (
	"context"
	"net/http"

	"github.com/getsentry/sentry-go"
	"github.com/rs/zerolog/log"
	"go.opentelemetry.io/otel/propagation"
	"go.opentelemetry.io/otel/trace"
)

type contextKey struct {
	Key string
}

var (
	tracerContextKey = contextKey{"tracer"}
)

func (t *Telemetry) StartSpan(ctx context.Context, operation, name string, cfgs ...ConfigureSpanStartFunc) *Span {
	otelStartOpts := make([]trace.SpanStartOption, 0)
	sentryStartOpts := []sentry.SpanOption{sentry.WithTransactionName(name), sentry.WithDescription(name)}

	for _, opt := range cfgs {
		var otel []trace.SpanStartOption
		var sentry []sentry.SpanOption

		ctx, otel, sentry = opt(ctx)

		otelStartOpts = append(otelStartOpts, otel...)
		sentryStartOpts = append(sentryStartOpts, sentry...)
	}

	var otelTracer trace.Tracer
	if tracer, ok := ctx.Value(tracerContextKey).(trace.Tracer); ok && tracer != nil {
		otelTracer = tracer
	} else {
		otelTracer = t.Tracer
	}

	ctx, otelSpan := otelTracer.Start(ctx, name, otelStartOpts...)
	sentrySpan := sentry.StartSpan(ctx, operation, sentryStartOpts...)

	return &Span{
		otel:   otelSpan,
		sentry: sentrySpan,
	}
}

type ConfigureSpanStartFunc = func(context.Context) (context.Context, []trace.SpanStartOption, []sentry.SpanOption)

func WithOtelOptions(opts ...trace.SpanStartOption) ConfigureSpanStartFunc {
	return func(ctx context.Context) (context.Context, []trace.SpanStartOption, []sentry.SpanOption) {
		return ctx, opts, []sentry.SpanOption{}
	}
}

func (t *Telemetry) InjectIntoHeaders(ctx context.Context, headers http.Header) {
	t.propagator.Inject(ctx, propagation.HeaderCarrier(headers))

	if sentrySpan := sentry.SpanFromContext(ctx); sentrySpan == nil {
		// this should never happen...
		log.Trace().Msgf("failed to inject Sentry span ID, Sentry span could not be extracted from the context.Context")
	} else {
		headers.Set("sentry-trace", sentrySpan.ToSentryTrace())
		headers.Set("sentry-baggage", sentrySpan.ToBaggage())
	}
}

func (t *Telemetry) ContinueFromRequest(r *http.Request) ConfigureSpanStartFunc {
	return func(ctx context.Context) (context.Context, []trace.SpanStartOption, []sentry.SpanOption) {
		ctx = t.propagator.Extract(ctx, propagation.HeaderCarrier(r.Header))

		return ctx, []trace.SpanStartOption{}, []sentry.SpanOption{sentry.ContinueFromRequest(r), sentry.WithTransactionSource(sentry.SourceURL)}
	}
}

func WithOtelTracer(tracer trace.Tracer) ConfigureSpanStartFunc {
	return func(ctx context.Context) (context.Context, []trace.SpanStartOption, []sentry.SpanOption) {
		return context.WithValue(ctx, tracerContextKey, tracer), []trace.SpanStartOption{}, []sentry.SpanOption{}
	}
}