package handler

import (
	"net/http"

	"github.com/zeromicro/go-zero/core/collection"
	"github.com/zeromicro/go-zero/core/trace"
	"github.com/zeromicro/go-zero/rest/internal/response"
	"go.opentelemetry.io/otel"
	"go.opentelemetry.io/otel/propagation"
	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
	oteltrace "go.opentelemetry.io/otel/trace"
)

type (
	// TracingOption defines the method to customize an tracingOptions.
	TracingOption func(options *tracingOptions)

	// tracingOptions is TracingHandler options.
	tracingOptions struct {
		traceIgnorePaths []string
	}
)

// TracingHandler return a middleware that process the opentelemetry.
func TracingHandler(serviceName, path string, opts ...TracingOption) func(http.Handler) http.Handler {
	var tracingOpts tracingOptions
	for _, opt := range opts {
		opt(&tracingOpts)
	}

	ignorePaths := collection.NewSet()
	ignorePaths.AddStr(tracingOpts.traceIgnorePaths...)
	traceHandler := func(checkIgnore bool) func(http.Handler) http.Handler {
		return func(next http.Handler) http.Handler {
			propagator := otel.GetTextMapPropagator()
			tracer := otel.GetTracerProvider().Tracer(trace.TraceName)

			return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
				spanName := path
				if len(spanName) == 0 {
					spanName = r.URL.Path
				}

				if checkIgnore && ignorePaths.Contains(spanName) {
					next.ServeHTTP(w, r)
					return
				}

				ctx := propagator.Extract(r.Context(), propagation.HeaderCarrier(r.Header))
				spanCtx, span := tracer.Start(
					ctx,
					spanName,
					oteltrace.WithSpanKind(oteltrace.SpanKindServer),
					oteltrace.WithAttributes(semconv.HTTPServerAttributesFromHTTPRequest(
						serviceName, spanName, r)...),
				)
				defer span.End()

				// convenient for tracking error messages
				propagator.Inject(spanCtx, propagation.HeaderCarrier(w.Header()))

				trw := &response.WithCodeResponseWriter{Writer: w, Code: http.StatusOK}
				next.ServeHTTP(trw, r.WithContext(spanCtx))

				span.SetAttributes(semconv.HTTPAttributesFromHTTPStatusCode(trw.Code)...)
				span.SetStatus(semconv.SpanStatusFromHTTPStatusCodeAndSpanKind(trw.Code, oteltrace.SpanKindServer))
			})
		}
	}
	checkIgnore := ignorePaths.Count() > 0
	return traceHandler(checkIgnore)
}

// WithTraceIgnorePaths specifies the traceIgnorePaths option for TracingHandler.
func WithTraceIgnorePaths(traceIgnorePaths []string) TracingOption {
	return func(options *tracingOptions) {
		options.traceIgnorePaths = append(options.traceIgnorePaths, traceIgnorePaths...)
	}
}