/*
NAME
  mpegts_test.go

DESCRIPTION
  mpegts_test.go contains testing for functionality found in mpegts.go.

AUTHORS
  Saxon A. Nelson-Milton <saxon@ausocean.org>

LICENSE
  Copyright (C) 2019 the Australian Ocean Lab (AusOcean)

  It is free software: you can redistribute it and/or modify them
  under the terms of the GNU General Public License as published by the
  Free Software Foundation, either version 3 of the License, or (at your
  option) any later version.

  It is distributed in the hope that it will be useful, but WITHOUT
  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  for more details.

  You should have received a copy of the GNU General Public License
  in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

package mts

import (
	"bytes"
	"math/rand"
	"testing"
	"time"

	"bitbucket.org/ausocean/av/container/mts/pes"
	"bitbucket.org/ausocean/av/container/mts/psi"
	"github.com/Comcast/gots/packet"
)

// TestGetPTSRange checks that GetPTSRange can correctly get the first and last
// PTS in an MPEGTS clip for a general case.
func TestGetPTSRange1(t *testing.T) {
	const (
		numOfFrames  = 20
		maxFrameSize = 1000
		minFrameSize = 100
		rate         = 25                // fps
		interval     = float64(1) / rate // s
		ptsFreq      = 90000             // Hz
	)

	// Generate randomly sized data for each frame.
	rand.Seed(time.Now().UnixNano())
	frames := make([][]byte, numOfFrames)
	for i := range frames {
		size := rand.Intn(maxFrameSize-minFrameSize) + minFrameSize
		frames[i] = make([]byte, size)
	}

	var clip bytes.Buffer

	// Write the PSI first.
	err := writePSI(&clip)
	if err != nil {
		t.Fatalf("did not expect error writing psi: %v", err)
	}

	// Now write frames.
	var curTime float64
	for _, frame := range frames {
		nextPTS := curTime * ptsFreq

		err = writeFrame(&clip, frame, uint64(nextPTS))
		if err != nil {
			t.Fatalf("did not expect error writing frame: %v", err)
		}

		curTime += interval
	}

	got, err := GetPTSRange(clip.Bytes(), videoPid)
	if err != nil {
		t.Fatalf("did not expect error getting PTS range: %v", err)
	}

	want := [2]uint64{0, uint64((numOfFrames - 1) * interval * ptsFreq)}
	if got != want {
		t.Errorf("did not get expected result.\n Got: %v\n Want: %v\n", got, want)
	}
}

// writePSI is a helper function write the PSI found at the start of a clip.
func writePSI(b *bytes.Buffer) error {
	// Write PAT.
	pat := Packet{
		PUSI:    true,
		PID:     PatPid,
		CC:      0,
		AFC:     HasPayload,
		Payload: psi.AddPadding(patTable),
	}
	_, err := b.Write(pat.Bytes(nil))
	if err != nil {
		return err
	}

	// Write PMT.
	pmt := Packet{
		PUSI:    true,
		PID:     PmtPid,
		CC:      0,
		AFC:     HasPayload,
		Payload: psi.AddPadding(pmtTable),
	}
	_, err = b.Write(pmt.Bytes(nil))
	if err != nil {
		return err
	}
	return nil
}

// writeFrame is a helper function used to form a PES packet from a frame, and
// then fragment this across MPEGTS packets where they are then written to the
// given buffer.
func writeFrame(b *bytes.Buffer, frame []byte, pts uint64) error {
	// Prepare PES data.
	pesPkt := pes.Packet{
		StreamID:     H264ID,
		PDI:          hasPTS,
		PTS:          pts,
		Data:         frame,
		HeaderLength: 5,
	}
	buf := pesPkt.Bytes(nil)

	// Write PES data acroos MPEGTS packets.
	pusi := true
	for len(buf) != 0 {
		pkt := Packet{
			PUSI: pusi,
			PID:  videoPid,
			RAI:  pusi,
			CC:   0,
			AFC:  hasAdaptationField | hasPayload,
			PCRF: pusi,
		}
		n := pkt.FillPayload(buf)
		buf = buf[n:]

		pusi = false
		_, err := b.Write(pkt.Bytes(nil))
		if err != nil {
			return err
		}
	}
	return nil
}

// TestGetPTSRange2 checks that GetPTSRange behaves correctly with cases where
// the first instance of a PID is not a payload start, and also where there
// are no payload starts.
func TestGetPTSRange2(t *testing.T) {
	const (
		nPackets = 8 // The number of MTS packets we will generate.
		wantPID  = 1 // The PID we want.
	)
	tests := []struct {
		pusi []bool    // The value of PUSI for each packet.
		pid  []uint16  // The PIDs for each packet.
		pts  []uint64  // The PTS for each packet.
		want [2]uint64 // The wanted PTS from GetPTSRange.
		err  error     // The error we expect from GetPTSRange.
	}{
		{
			[]bool{false, false, false, true, false, false, true, false},
			[]uint16{0, 0, 1, 1, 1, 1, 1, 1},
			[]uint64{0, 0, 0, 1, 0, 0, 2, 0},
			[2]uint64{1, 2},
			nil,
		},
		{
			[]bool{false, false, false, true, false, false, false, false},
			[]uint16{0, 0, 1, 1, 1, 1, 1, 1},
			[]uint64{0, 0, 0, 1, 0, 0, 0, 0},
			[2]uint64{1, 1},
			nil,
		},
		{
			[]bool{false, false, false, false, false, false, false, false},
			[]uint16{0, 0, 1, 1, 1, 1, 1, 1},
			[]uint64{0, 0, 0, 0, 0, 0, 0, 0},
			[2]uint64{0, 0},
			errNoPTS,
		},
	}

	var clip bytes.Buffer

	for i, test := range tests {
		// Generate MTS packets for this test.
		clip.Reset()
		for j := 0; j < nPackets; j++ {
			pesPkt := pes.Packet{
				StreamID:     H264ID,
				PDI:          hasPTS,
				PTS:          test.pts[j],
				Data:         []byte{},
				HeaderLength: 5,
			}
			buf := pesPkt.Bytes(nil)

			pkt := Packet{
				PUSI: test.pusi[j],
				PID:  test.pid[j],
				RAI:  true,
				CC:   0,
				AFC:  hasAdaptationField | hasPayload,
				PCRF: true,
			}
			pkt.FillPayload(buf)

			_, err := clip.Write(pkt.Bytes(nil))
			if err != nil {
				t.Fatalf("did not expect clip write error: %v", err)
			}
		}

		pts, err := GetPTSRange(clip.Bytes(), wantPID)
		if err != test.err {
			t.Errorf("did not get expected error for test: %v\nGot: %v\nWant: %v\n", i, err, test.err)
		}

		if pts != test.want {
			t.Errorf("did not get expected result for test: %v\nGot: %v\nWant: %v\n", i, pts, test.want)
		}
	}
}

// TestBytes checks that Packet.Bytes() correctly produces a []byte
// representation of a Packet.
func TestBytes(t *testing.T) {
	const payloadLen, payloadChar, stuffingChar = 120, 0x11, 0xff
	const stuffingLen = PacketSize - payloadLen - 12

	tests := []struct {
		packet         Packet
		expectedHeader []byte
	}{
		{
			packet: Packet{
				PUSI: true,
				PID:  1,
				RAI:  true,
				CC:   4,
				AFC:  HasPayload | HasAdaptationField,
				PCRF: true,
				PCR:  1,
			},
			expectedHeader: []byte{
				0x47,                               // Sync byte.
				0x40,                               // TEI=0, PUSI=1, TP=0, PID=00000.
				0x01,                               // PID(Cont)=00000001.
				0x34,                               // TSC=00, AFC=11(adaptation followed by payload), CC=0100(4).
				byte(7 + stuffingLen),              // AFL=.
				0x50,                               // DI=0,RAI=1,ESPI=0,PCRF=1,OPCRF=0,SPF=0,TPDF=0, AFEF=0.
				0x00, 0x00, 0x00, 0x00, 0x80, 0x00, // PCR.
			},
		},
	}

	for testNum, test := range tests {
		// Construct payload.
		payload := make([]byte, 0, payloadLen)
		for i := 0; i < payloadLen; i++ {
			payload = append(payload, payloadChar)
		}

		// Fill the packet payload.
		test.packet.FillPayload(payload)

		// Create expected packet data and copy in expected header.
		expected := make([]byte, len(test.expectedHeader), PacketSize)
		copy(expected, test.expectedHeader)

		// Append stuffing.
		for i := 0; i < stuffingLen; i++ {
			expected = append(expected, stuffingChar)
		}

		// Append payload to expected bytes.
		expected = append(expected, payload...)

		// Compare got with expected.
		got := test.packet.Bytes(nil)
		if !bytes.Equal(got, expected) {
			t.Errorf("did not get expected result for test: %v.\n Got: %v\n Want: %v\n", testNum, got, expected)
		}
	}
}

// TestFindPid checks that FindPid can correctly extract the first instance
// of a PID from an MPEG-TS stream.
func TestFindPid(t *testing.T) {
	const targetPacketNum, numOfPackets, targetPid, stdPid = 6, 15, 1, 0

	// Prepare the stream of packets.
	var stream []byte
	for i := 0; i < numOfPackets; i++ {
		pid := uint16(stdPid)
		if i == targetPacketNum {
			pid = targetPid
		}

		p := Packet{
			PID: pid,
			AFC: hasPayload | hasAdaptationField,
		}
		p.FillPayload([]byte{byte(i)})
		stream = append(stream, p.Bytes(nil)...)
	}

	// Try to find the targetPid in the stream.
	p, i, err := FindPid(stream, targetPid)
	if err != nil {
		t.Fatalf("unexpected error finding PID: %v\n", err)
	}

	// Check the payload.
	var _p packet.Packet
	copy(_p[:], p)
	payload, err := packet.Payload(&_p)
	if err != nil {
		t.Fatalf("unexpected error getting packet payload: %v\n", err)
	}
	got := payload[0]
	if got != targetPacketNum {
		t.Errorf("payload of found packet is not correct.\nGot: %v, Want: %v\n", got, targetPacketNum)
	}

	// Check the index.
	_got := i / PacketSize
	if _got != targetPacketNum {
		t.Errorf("index of found packet is not correct.\nGot: %v, want: %v\n", _got, targetPacketNum)
	}
}