// Copyright 2023 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package quic

import (
	"bytes"
	"encoding/hex"
	"strings"
	"testing"
)

func TestPacketHeader(t *testing.T) {
	for _, test := range []struct {
		name         string
		packet       []byte
		isLongHeader bool
		packetType   packetType
		dstConnID    []byte
	}{{
		// Initial packet from https://www.rfc-editor.org/rfc/rfc9001#section-a.1
		// (truncated)
		name: "rfc9001_a1",
		packet: unhex(`
			c000000001088394c8f03e5157080000 449e7b9aec34d1b1c98dd7689fb8ec11
		`),
		isLongHeader: true,
		packetType:   packetTypeInitial,
		dstConnID:    unhex(`8394c8f03e515708`),
	}, {
		// Initial packet from https://www.rfc-editor.org/rfc/rfc9001#section-a.3
		// (truncated)
		name: "rfc9001_a3",
		packet: unhex(`
			cf000000010008f067a5502a4262b500 4075c0d95a482cd0991cd25b0aac406a
		`),
		isLongHeader: true,
		packetType:   packetTypeInitial,
		dstConnID:    []byte{},
	}, {
		// Retry packet from https://www.rfc-editor.org/rfc/rfc9001#section-a.4
		name: "rfc9001_a4",
		packet: unhex(`
			ff000000010008f067a5502a4262b574 6f6b656e04a265ba2eff4d829058fb3f
			0f2496ba
		`),
		isLongHeader: true,
		packetType:   packetTypeRetry,
		dstConnID:    []byte{},
	}, {
		// Short header packet from https://www.rfc-editor.org/rfc/rfc9001#section-a.5
		name: "rfc9001_a5",
		packet: unhex(`
			4cfe4189655e5cd55c41f69080575d7999c25a5bfb
		`),
		isLongHeader: false,
		packetType:   packetType1RTT,
		dstConnID:    unhex(`fe4189655e5cd55c`),
	}, {
		// Version Negotiation packet.
		name: "version_negotiation",
		packet: unhex(`
			80 00000000 01ff0001020304
		`),
		isLongHeader: true,
		packetType:   packetTypeVersionNegotiation,
		dstConnID:    []byte{0xff},
	}, {
		// Too-short packet.
		name: "truncated_after_connid_length",
		packet: unhex(`
			cf0000000105
		`),
		isLongHeader: true,
		packetType:   packetTypeInitial,
		dstConnID:    nil,
	}, {
		// Too-short packet.
		name: "truncated_after_version",
		packet: unhex(`
			cf00000001
		`),
		isLongHeader: true,
		packetType:   packetTypeInitial,
		dstConnID:    nil,
	}, {
		// Much too short packet.
		name: "truncated_in_version",
		packet: unhex(`
			cf000000
		`),
		isLongHeader: true,
		packetType:   packetTypeInvalid,
		dstConnID:    nil,
	}} {
		t.Run(test.name, func(t *testing.T) {
			if got, want := isLongHeader(test.packet[0]), test.isLongHeader; got != want {
				t.Errorf("packet %x:\nisLongHeader(packet) = %v, want %v", test.packet, got, want)
			}
			if got, want := getPacketType(test.packet), test.packetType; got != want {
				t.Errorf("packet %x:\ngetPacketType(packet) = %v, want %v", test.packet, got, want)
			}
			gotConnID, gotOK := dstConnIDForDatagram(test.packet)
			wantConnID, wantOK := test.dstConnID, test.dstConnID != nil
			if !bytes.Equal(gotConnID, wantConnID) || gotOK != wantOK {
				t.Errorf("packet %x:\ndstConnIDForDatagram(packet) = {%x}, %v; want {%x}, %v", test.packet, gotConnID, gotOK, wantConnID, wantOK)
			}
		})
	}
}

func unhex(s string) []byte {
	b, err := hex.DecodeString(strings.Map(func(c rune) rune {
		switch c {
		case ' ', '\t', '\n':
			return -1
		}
		return c
	}, s))
	if err != nil {
		panic(err)
	}
	return b
}