// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

package b3_test

import (
	"fmt"

	"go.opentelemetry.io/otel/trace"

	"go.opentelemetry.io/contrib/propagators/b3"
)

const (
	b3Context      = "b3"
	b3Flags        = "x-b3-flags"
	b3TraceID      = "x-b3-traceid"
	b3SpanID       = "x-b3-spanid"
	b3Sampled      = "x-b3-sampled"
	b3ParentSpanID = "x-b3-parentspanid"
)

const (
	traceIDStr = "4bf92f3577b34da6a3ce929d0e0e4736"
	spanIDStr  = "00f067aa0ba902b7"
)

var (
	traceID = mustTraceIDFromHex(traceIDStr)
	spanID  = mustSpanIDFromHex(spanIDStr)

	traceID64bitPadded = mustTraceIDFromHex("0000000000000000a3ce929d0e0e4736")
)

func mustTraceIDFromHex(s string) trace.TraceID {
	t, err := trace.TraceIDFromHex(s)
	if err != nil {
		panic(err)
	}
	return t
}

func mustSpanIDFromHex(s string) trace.SpanID {
	t, err := trace.SpanIDFromHex(s)
	if err != nil {
		panic(err)
	}
	return t
}

type extractTest struct {
	name     string
	headers  map[string]string
	wantScc  trace.SpanContextConfig
	debug    bool
	deferred bool
}

var extractHeaders = []extractTest{
	{
		name:    "empty",
		headers: map[string]string{},
		wantScc: trace.SpanContextConfig{},
	},
	{
		name: "multiple: sampling state defer",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		deferred: true,
	},
	{
		name: "multiple: sampling state deny",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "0",
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
	},
	{
		name: "multiple: sampling state accept",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "1",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		name: "multiple: sampling state as a boolean: true",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "true",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		name: "multiple: sampling state as a boolean: false",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "false",
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
	},
	{
		name: "multiple: debug flag set",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Flags:   "1",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		debug: true,
	},
	{
		name: "multiple: debug flag set to not 1 (ignored)",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "1",
			b3Flags:   "2",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		// spec explicitly states "Debug implies an accept decision, so don't
		// also send the X-B3-Sampled header", make sure sampling is set in this case.
		name: "multiple: debug flag set and sampling state is deny",
		headers: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "0",
			b3Flags:   "1",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		debug: true,
	},
	{
		name: "multiple: with parent span id",
		headers: map[string]string{
			b3TraceID:      traceIDStr,
			b3SpanID:       spanIDStr,
			b3Sampled:      "1",
			b3ParentSpanID: "00f067aa0ba90200",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		name: "multiple: with only sampled state header",
		headers: map[string]string{
			b3Sampled: "0",
		},
		wantScc: trace.SpanContextConfig{},
	},
	{
		name: "multiple: left-padding 64-bit traceID",
		headers: map[string]string{
			b3TraceID: "a3ce929d0e0e4736",
			b3SpanID:  spanIDStr,
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID64bitPadded,
			SpanID:  spanID,
		},
		deferred: true,
	},
	{
		name: "single: sampling state defer",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s", traceIDStr, spanIDStr),
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		deferred: true,
	},
	{
		name: "single: sampling state deny",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-0", traceIDStr, spanIDStr),
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
	},
	{
		name: "single: sampling state accept",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-1", traceIDStr, spanIDStr),
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		name: "single: sampling state debug",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-d", traceIDStr, spanIDStr),
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		debug: true,
	},
	{
		name: "single: with parent span id",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-1-00000000000000cd", traceIDStr, spanIDStr),
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		name: "single: with only sampling state deny",
		headers: map[string]string{
			b3Context: "0",
		},
		wantScc: trace.SpanContextConfig{},
	},
	{
		name: "single: left-padding 64-bit traceID",
		headers: map[string]string{
			b3Context: fmt.Sprintf("a3ce929d0e0e4736-%s", spanIDStr),
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID64bitPadded,
			SpanID:  spanID,
		},
		deferred: true,
	},
	{
		name: "both single and multiple: single priority",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-1", traceIDStr, spanIDStr),
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "0",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	// An invalid Single Headers should fallback to multiple.
	{
		name: "both single and multiple: invalid single",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-", traceIDStr, spanIDStr),
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "0",
		},
		wantScc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
	},
	// Invalid Mult Header should not be noticed as Single takes precedence.
	{
		name: "both single and multiple: invalid multiple",
		headers: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-1", traceIDStr, spanIDStr),
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "invalid",
		},
		wantScc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
}

var extractInvalidHeaders = []extractTest{
	{
		name: "multiple: trace ID length > 32",
		headers: map[string]string{
			b3TraceID: "ab00000000000000000000000000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: trace ID length >16 and <32",
		headers: map[string]string{
			b3TraceID: "ab0000000000000000000000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: trace ID length <16",
		headers: map[string]string{
			b3TraceID: "ab0000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: wrong span ID length",
		headers: map[string]string{
			b3TraceID: "ab000000000000000000000000000000",
			b3SpanID:  "cd0000000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: wrong sampled flag length",
		headers: map[string]string{
			b3TraceID: "ab000000000000000000000000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "10",
		},
	},
	{
		name: "multiple: bogus trace ID",
		headers: map[string]string{
			b3TraceID: "qw000000000000000000000000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: bogus span ID",
		headers: map[string]string{
			b3TraceID: "ab000000000000000000000000000000",
			b3SpanID:  "qw00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: bogus sampled flag",
		headers: map[string]string{
			b3TraceID: "ab000000000000000000000000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "d",
		},
	},
	{
		name: "multiple: upper case trace ID",
		headers: map[string]string{
			b3TraceID: "AB000000000000000000000000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: upper case span ID",
		headers: map[string]string{
			b3TraceID: "ab000000000000000000000000000000",
			b3SpanID:  "CD00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: zero trace ID",
		headers: map[string]string{
			b3TraceID: "00000000000000000000000000000000",
			b3SpanID:  "cd00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: zero span ID",
		headers: map[string]string{
			b3TraceID: "ab000000000000000000000000000000",
			b3SpanID:  "0000000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: missing span ID",
		headers: map[string]string{
			b3TraceID: "ab000000000000000000000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: missing trace ID",
		headers: map[string]string{
			b3SpanID:  "cd00000000000000",
			b3Sampled: "1",
		},
	},
	{
		name: "multiple: sampled header set to 1 but trace ID and span ID are missing",
		headers: map[string]string{
			b3Sampled: "1",
		},
	},
	{
		name: "single: wrong trace ID length",
		headers: map[string]string{
			b3Context: "ab00000000000000000000000000000000-cd00000000000000-1",
		},
	},
	{
		name: "single: wrong span ID length",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-cd0000000000000000-1",
		},
	},
	{
		name: "single: wrong sampled state length",
		headers: map[string]string{
			b3Context: "00-ab000000000000000000000000000000-cd00000000000000-01",
		},
	},
	{
		name: "single: wrong parent span ID length",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-cd00000000000000-1-cd0000000000000000",
		},
	},
	{
		name: "single: bogus trace ID",
		headers: map[string]string{
			b3Context: "qw000000000000000000000000000000-cd00000000000000-1",
		},
	},
	{
		name: "single: bogus span ID",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-qw00000000000000-1",
		},
	},
	{
		name: "single: bogus sampled flag",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-cd00000000000000-q",
		},
	},
	{
		name: "single: bogus parent span ID",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-cd00000000000000-1-qw00000000000000",
		},
	},
	{
		name: "single: upper case trace ID",
		headers: map[string]string{
			b3Context: "AB000000000000000000000000000000-cd00000000000000-1",
		},
	},
	{
		name: "single: upper case span ID",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-CD00000000000000-1",
		},
	},
	{
		name: "single: upper case parent span ID",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-cd00000000000000-1-EF00000000000000",
		},
	},
	{
		name: "single: zero trace ID and span ID",
		headers: map[string]string{
			b3Context: "00000000000000000000000000000000-0000000000000000-1",
		},
	},
	{
		name: "single: with sampling set to true",
		headers: map[string]string{
			b3Context: "ab000000000000000000000000000000-cd00000000000000-true",
		},
	},
}

type injectTest struct {
	name             string
	encoding         b3.Encoding
	scc              trace.SpanContextConfig
	wantHeaders      map[string]string
	doNotWantHeaders []string
	debug            bool
	deferred         bool
}

var injectHeader = []injectTest{
	{
		name: "none: sampled",
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-%s", traceIDStr, spanIDStr, "1"),
		},
		doNotWantHeaders: []string{
			b3ParentSpanID,
			b3TraceID,
			b3SpanID,
			b3Sampled,
			b3Flags,
			b3Context,
		},
	},
	{
		name: "none: not sampled",
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-%s", traceIDStr, spanIDStr, "0"),
		},
		doNotWantHeaders: []string{
			b3ParentSpanID,
			b3TraceID,
			b3SpanID,
			b3Sampled,
			b3Flags,
			b3Context,
		},
	},
	{
		name: "none: unset sampled",
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3TraceID,
			b3SpanID,
			b3ParentSpanID,
			b3Flags,
			b3Context,
		},
		deferred: true,
	},
	{
		name: "none: sampled only",
		scc: trace.SpanContextConfig{
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Context: "1",
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3ParentSpanID,
			b3Flags,
			b3Context,
		},
	},
	{
		name: "none: debug",
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-%s", traceIDStr, spanIDStr, "d"),
		},
		doNotWantHeaders: []string{
			b3Sampled,
			traceIDStr,
			spanIDStr,
			b3ParentSpanID,
			b3Context,
		},
		debug: true,
	},
	{
		name: "none: debug omitting sample",
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-%s", traceIDStr, spanIDStr, "d"),
		},
		doNotWantHeaders: []string{
			b3Sampled,
			traceIDStr,
			spanIDStr,
			b3Flags,
			b3ParentSpanID,
			b3Context,
		},
		debug: true,
	},
	{
		name:     "multiple: sampled",
		encoding: b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "1",
		},
		doNotWantHeaders: []string{
			b3ParentSpanID,
			b3Flags,
			b3Context,
		},
	},
	{
		name:     "multiple: not sampled",
		encoding: b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "0",
		},
		doNotWantHeaders: []string{
			b3ParentSpanID,
			b3Flags,
			b3Context,
		},
	},
	{
		name:     "multiple: unset sampled",
		encoding: b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3ParentSpanID,
			b3Flags,
			b3Context,
		},
		deferred: true,
	},
	{
		name:     "multiple: sampled only",
		encoding: b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Sampled: "1",
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3ParentSpanID,
			b3Flags,
			b3Context,
		},
	},
	{
		name:     "multiple: debug",
		encoding: b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Flags:   "1",
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3ParentSpanID,
			b3Context,
		},
		debug: true,
	},
	{
		name:     "multiple: debug omitting sample",
		encoding: b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Flags:   "1",
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3ParentSpanID,
			b3Context,
		},
		debug: true,
	},
	{
		name:     "single: sampled",
		encoding: b3.B3SingleHeader,
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-1", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3Sampled,
			b3ParentSpanID,
			b3Flags,
		},
	},
	{
		name:     "single: not sampled",
		encoding: b3.B3SingleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-0", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3Sampled,
			b3ParentSpanID,
			b3Flags,
		},
	},
	{
		name:     "single: unset sampled",
		encoding: b3.B3SingleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3Sampled,
			b3ParentSpanID,
			b3Flags,
		},
		deferred: true,
	},
	{
		name:     "single: sampled only",
		encoding: b3.B3SingleHeader,
		scc: trace.SpanContextConfig{
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Context: "1",
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3TraceID,
			b3SpanID,
			b3ParentSpanID,
			b3Flags,
			b3Context,
		},
	},
	{
		name:     "single: debug",
		encoding: b3.B3SingleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-d", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3Flags,
			b3Sampled,
			b3ParentSpanID,
			b3Context,
		},
		debug: true,
	},
	{
		name:     "single: debug omitting sample",
		encoding: b3.B3SingleHeader,
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Context: fmt.Sprintf("%s-%s-d", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3Flags,
			b3Sampled,
			b3ParentSpanID,
			b3Context,
		},
		debug: true,
	},
	{
		name:     "single+multiple: sampled",
		encoding: b3.B3SingleHeader | b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "1",
			b3Context: fmt.Sprintf("%s-%s-1", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3ParentSpanID,
			b3Flags,
		},
	},
	{
		name:     "single+multiple: not sampled",
		encoding: b3.B3SingleHeader | b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Sampled: "0",
			b3Context: fmt.Sprintf("%s-%s-0", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3ParentSpanID,
			b3Flags,
		},
	},
	{
		name:     "single+multiple: unset sampled",
		encoding: b3.B3SingleHeader | b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Context: fmt.Sprintf("%s-%s", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3ParentSpanID,
			b3Flags,
		},
		deferred: true,
	},
	{
		name:     "single+multiple: sampled only",
		encoding: b3.B3SingleHeader | b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3Context: "1",
			b3Sampled: "1",
		},
		doNotWantHeaders: []string{
			b3TraceID,
			b3SpanID,
			b3ParentSpanID,
			b3Flags,
		},
	},
	{
		name:     "single+multiple: debug",
		encoding: b3.B3SingleHeader | b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID: traceID,
			SpanID:  spanID,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Flags:   "1",
			b3Context: fmt.Sprintf("%s-%s-d", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3ParentSpanID,
		},
		debug: true,
	},
	{
		name:     "single+multiple: debug omitting sample",
		encoding: b3.B3SingleHeader | b3.B3MultipleHeader,
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
		wantHeaders: map[string]string{
			b3TraceID: traceIDStr,
			b3SpanID:  spanIDStr,
			b3Flags:   "1",
			b3Context: fmt.Sprintf("%s-%s-d", traceIDStr, spanIDStr),
		},
		doNotWantHeaders: []string{
			b3Sampled,
			b3ParentSpanID,
		},
		debug: true,
	},
}

var injectInvalidHeaderGenerator = []injectTest{
	{
		name: "empty",
		scc:  trace.SpanContextConfig{},
	},
	{
		name: "missing traceID",
		scc: trace.SpanContextConfig{
			SpanID:     spanID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		name: "missing spanID",
		scc: trace.SpanContextConfig{
			TraceID:    traceID,
			TraceFlags: trace.FlagsSampled,
		},
	},
	{
		name: "missing traceID and spanID",
		scc: trace.SpanContextConfig{
			TraceFlags: trace.FlagsSampled,
		},
	},
}

var injectInvalidHeader []injectTest

func init() {
	// Perform a test for each invalid injectTest with all combinations of
	// encoding values.
	injectInvalidHeader = make([]injectTest, 0, len(injectInvalidHeaderGenerator)*4)
	allHeaders := []string{
		b3TraceID,
		b3SpanID,
		b3Sampled,
		b3ParentSpanID,
		b3Flags,
		b3Context,
	}
	// Nothing should be set for any header regardless of encoding.
	for i := range injectInvalidHeaderGenerator {
		t := &injectInvalidHeaderGenerator[i]
		injectInvalidHeader = append(
			injectInvalidHeader,
			injectTest{
				name:             "none: " + t.name,
				scc:              t.scc,
				doNotWantHeaders: allHeaders,
			},
			injectTest{
				name:             "multiple: " + t.name,
				encoding:         b3.B3MultipleHeader,
				scc:              t.scc,
				doNotWantHeaders: allHeaders,
			},
			injectTest{
				name:             "single: " + t.name,
				encoding:         b3.B3SingleHeader,
				scc:              t.scc,
				doNotWantHeaders: allHeaders,
			},
			injectTest{
				name:             "single+multiple: " + t.name,
				encoding:         b3.B3SingleHeader | b3.B3MultipleHeader,
				scc:              t.scc,
				doNotWantHeaders: allHeaders,
			},
		)
	}
}