/*
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"
	"reflect"
	"strconv"
	"testing"
	"time"

	"bitbucket.org/ausocean/av/container/mts/meta"
	"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.
func TestGetPTSRange(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
}

// 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)
	}
}

// TestTrimToMetaRange checks that TrimToMetaRange can correctly return a segment
// of MPEG-TS corresponding to a meta interval in a slice of MPEG-TS.
func TestTrimToMetaRange(t *testing.T) {
	Meta = meta.New()

	const (
		nPSI = 10
		key  = "n"
	)

	var (
		clip bytes.Buffer
	)

	for i := 0; i < nPSI; i++ {
		Meta.Add(key, strconv.Itoa((i*2)+1))
		err := writePSIWithMeta(&clip)
		if err != nil {
			t.Fatalf("did not expect to get error writing PSI, error: %v", err)
		}
	}

	tests := []struct {
		from   string
		to     string
		expect []byte
		err    error
	}{
		{
			from:   "3",
			to:     "9",
			expect: clip.Bytes()[3*PacketSize : 10*PacketSize],
			err:    nil,
		},
		{
			from:   "30",
			to:     "8",
			expect: nil,
			err:    errMetaLowerBound,
		},
		{
			from:   "3",
			to:     "30",
			expect: nil,
			err:    errMetaUpperBound,
		},
	}

	// Run tests.
	for i, test := range tests {
		got, err := TrimToMetaRange(clip.Bytes(), key, test.from, test.to)

		// First check the error.
		if err != nil && err != test.err {
			t.Errorf("unexpected error: %v for test: %v", err, i)
			continue
		} else if err != test.err {
			t.Errorf("expected to get error: %v for test: %v", test.err, i)
			continue
		}

		// Now check data.
		if test.err == nil && !bytes.Equal(test.expect, got) {
			t.Errorf("did not get expected data for test: %v\n Got: %v\n, Want: %v\n", i, got, test.expect)
		}
	}
}

// TestSegmentForMeta checks that SegmentForMeta can correctly segment some MTS
// data based on a given meta key and value.
func TestSegmentForMeta(t *testing.T) {
	Meta = meta.New()

	const (
		nPSI = 10  // The number of PSI pairs to write.
		key  = "n" // The meta key we will work with.
		val  = "*" // This is the meta value we will look for.
	)

	tests := []struct {
		metaVals   [nPSI]string // This represents the meta value for meta pairs (PAT and PMT)
		expectIdxs []rng        // This gives the expect index ranges for the segments.
	}{
		{
			metaVals: [nPSI]string{"1", "2", val, val, val, "3", val, val, "4", "4"},
			expectIdxs: []rng{
				scale(2, 5),
				scale(6, 8),
			},
		},
		{
			metaVals: [nPSI]string{"1", "2", val, val, val, "", "3", val, val, "4"},
			expectIdxs: []rng{
				scale(2, 5),
				scale(7, 9),
			},
		},
		{
			metaVals: [nPSI]string{"1", "2", val, val, val, "", "3", val, val, val},
			expectIdxs: []rng{
				scale(2, 5),
				{((7 * 2) + 1) * PacketSize, (nPSI * 2) * PacketSize},
			},
		},
		{
			metaVals:   [nPSI]string{"1", "2", "3", "4", "5", "6", "7", "8", "9", "10"},
			expectIdxs: nil,
		},
	}

	var clip bytes.Buffer

	for testn, test := range tests {
		// We want a clean buffer for each new test, so reset.
		clip.Reset()

		// Add meta and write PSI to clip.
		for i := 0; i < nPSI; i++ {
			if test.metaVals[i] != "" {
				Meta.Add(key, test.metaVals[i])
			} else {
				Meta.Delete(key)
			}
			err := writePSIWithMeta(&clip)
			if err != nil {
				t.Fatalf("did not expect to get error writing PSI, error: %v", err)
			}
		}

		// Now we get the expected segments using the index ranges from the test.
		var want [][]byte
		for _, idxs := range test.expectIdxs {
			want = append(want, clip.Bytes()[idxs.start:idxs.end])
		}

		// Now use the function we're testing to get the segments.
		got, err := SegmentForMeta(clip.Bytes(), key, val)
		if err != nil {
			t.Fatalf("unexpected error: %v", err)
		}

		// Check that segments are OK.
		if !reflect.DeepEqual(want, got) {
			t.Errorf("did not get expected result for test %v\nGot: %v\nWant: %v\n", testn, got, want)
		}
	}
}

// rng describes an index range and is used by TestSegmentForMeta.
type rng struct {
	start int
	end   int
}

// scale takes a PSI index (i.e. first PSI is 0, next is 1) and modifies to be
// the index of the first byte of the PSI pair (PAT and PMT) in the byte stream.
// This assumes there are only PSI written consequitively, and is used by
// TestSegmentForMeta.
func scale(x, y int) rng {
	return rng{
		((x * 2) + 1) * PacketSize,
		((y * 2) + 1) * PacketSize,
	}
}