package utils

import (
	"context"

	"git.frostfs.info/TrueCloudLab/frostfs-observability/tracing"
	"github.com/valyala/fasthttp"
	"go.opentelemetry.io/otel/attribute"
	"go.opentelemetry.io/otel/codes"
	semconv "go.opentelemetry.io/otel/semconv/v1.17.0"
	"go.opentelemetry.io/otel/trace"
)

type httpCarrier struct {
	r *fasthttp.RequestCtx
}

func (c *httpCarrier) Get(key string) string {
	bytes := c.r.Request.Header.Peek(key)
	if len(bytes) == 0 {
		return ""
	}
	return string(bytes)
}

func (c *httpCarrier) Set(key string, value string) {
	c.r.Response.Header.Set(key, value)
}

func (c *httpCarrier) Keys() []string {
	dict := make(map[string]interface{})
	c.r.Request.Header.VisitAll(
		func(key, _ []byte) {
			dict[string(key)] = true
		},
	)
	c.r.Response.Header.VisitAll(
		func(key, _ []byte) {
			dict[string(key)] = true
		},
	)
	result := make([]string, 0, len(dict))
	for key := range dict {
		result = append(result, key)
	}
	return result
}

func extractHTTPTraceInfo(ctx context.Context, req *fasthttp.RequestCtx) context.Context {
	if req == nil {
		return ctx
	}
	carrier := &httpCarrier{r: req}
	return tracing.Propagator.Extract(ctx, carrier)
}

// SetHTTPTraceInfo saves trace headers to response.
func SetHTTPTraceInfo(ctx context.Context, span trace.Span, req *fasthttp.RequestCtx) {
	if req == nil {
		return
	}
	if err := req.Err(); err != nil {
		span.SetStatus(codes.Error, err.Error())
	}
	span.SetAttributes(
		semconv.HTTPStatusCode(req.Response.StatusCode()),
	)
	carrier := &httpCarrier{r: req}
	tracing.Propagator.Inject(ctx, carrier)
}

// StartHTTPServerSpan starts root HTTP server span.
func StartHTTPServerSpan(ctx context.Context, req *fasthttp.RequestCtx, operationName string, opts ...trace.SpanStartOption) (context.Context, trace.Span) {
	ctx = extractHTTPTraceInfo(ctx, req)
	opts = append(opts, trace.WithAttributes(
		attribute.String("http.client_address", req.RemoteAddr().String()),
		attribute.String("http.path", string(req.Path())),
		semconv.HTTPMethod(string(req.Method())),
		semconv.RPCService("frostfs-http-gw"),
		attribute.String("http.query", req.QueryArgs().String()),
	), trace.WithSpanKind(trace.SpanKindServer))
	return tracing.StartSpanFromContext(ctx, operationName, opts...)
}