/*
NAME
  rtmp.go

DESCRIPTION
  See Readme.md

AUTHOR
  Saxon Nelson-Milton <saxon@ausocean.org>
  Dan Kortschak <dan@ausocean.org>

LICENSE
  rtmp.go is Copyright (C) 2017 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
  along with revid in gpl.txt.  If not, see http://www.gnu.org/licenses.
*/

package rtmp

/*
#cgo CFLAGS: -I/usr/local/include/librtmp
#cgo LDFLAGS: -lrtmp -Wl,-rpath=/usr/local/lib

#include <stdlib.h>
#include <string.h>
#include <rtmp.h>

RTMP* start_session(RTMP* rtmp, char* url, uint connect_timeout);
int write_frame(RTMP* rtmp, char* data, uint data_length);
int end_session(RTMP* rtmp);
void AV_queue(RTMP_METHOD **vals, int *num, AVal *av, int txn);
int WriteN(RTMP *r, const char *buffer, int n);
*/
import "C"

import (
	"errors"
	_ "fmt"
	"log"
	"math"
	"reflect"
	"strconv"
	"unsafe"
)

const (
	minDataSize = 11
	debugMode = false
	nullChar = "golang\000"
)

const (
	byteSize	= 1
	int32Size = 4
	int64Size = 8
)

const (
	RTMP_PACKET_SIZE_LARGE  = 0
	RTMP_PACKET_SIZE_MEDIUM = 1
	RTMP_PACKET_SIZE_SMALL  = 2
	RTMP_PACKET_TYPE_INFO   = 0x12
	RTMP_PACKET_TYPE_AUDIO  = 0x08
	RTMP_PACKET_TYPE_VIDEO  = 0x09
)

// C.AVal is in amf.h
// See #define AVC(str) {str, sizeof(str)-1} in amf.h
func AVC(str string) C.AVal {
	var aval C.AVal
	aval.av_val = C.CString(str)
	aval.av_len = C.int(len(str))
	return aval
}

// av_setDataFrame is a static const global in rtmp.c
var setDataFrame = AVC("@setDataFrame")

var packetSize = [...]int32{ 12, 8, 4, 1}

// Session provides an interface for sending flv tags over rtmp.
type Session interface {
	Open() error
	Write([]byte) (int, error)
	Close() error
}

// session provides parameters required for an rtmp communication session.
type session struct {
	rtmp    *C.RTMP
	url     string
	timeout uint
}

var _ Session = (*session)(nil)

// NewSession returns a new session.
func NewSession(url string, connectTimeout uint) Session {
	return &session{
		url:     url,
		timeout: connectTimeout,
	}
}

// Open establishes an rtmp connection with the url passed into the
// constructor
func (s *session) Open() error {
	if s.rtmp != nil {
		return errors.New("rtmp: attempt to start already running session")
	}
	var err error
	s.rtmp, err = C.start_session(s.rtmp, C.CString(s.url), C.uint(s.timeout))
	if s.rtmp == nil {
		return err
	}
	return nil
}

// Close terminates the rtmp connection
func (s *session) Close() error {
	if s.rtmp == nil {
		return Err(3)
	}
	ret := C.end_session(s.rtmp)
	s.rtmp = nil
	if ret != 0 {
		return Err(ret)
	}
	return nil
}

// Write writes a frame (flv tag) to the rtmp connection
func (s *session) Write(data []byte) (int, error) {
	if s.rtmp == nil {
		return 0, Err(3)
	}
	if C.RTMP_IsConnected(s.rtmp) == 0 {
		return 0, Err(1)
	}
	//if C.RTMP_Write(s.rtmp,(*C.char)(unsafe.Pointer(&data[0])),C.int(len(data))) == 0 {
	if rtmpWrite(s.rtmp, data) == 0 {
		return 0, Err(2)
	}
	return len(data), nil
}

// rtmpWrite writes data to the current rtmp connection encapsulated by r
func rtmpWrite(r *C.RTMP, data []byte) int {
	buf := sliceToPtr(data)
	// TODO: port RTMPPacket
	var pkt = &r.m_write
	var pend, enc unsafe.Pointer
	size := len(data)
	s2 := size
	var ret, num int

	pkt.m_nChannel = 0x04
	pkt.m_nInfoField2 = r.m_stream_id
	for s2 != 0 {
		if pkt.m_nBytesRead == 0 {
			if size < minDataSize {
				log.Printf("size: %d\n", size)
				log.Printf("too small \n")
				return 0
			}

			if indxBytePtr(buf,0) == 'F' && indxBytePtr(buf,1) == 'L' && indxBytePtr(buf,2) == 'V' {
				buf = unsafe.Pointer(uintptr(buf) + uintptr(13))
				s2 -= 13
			}

			pkt.m_packetType = C.uchar(indxBytePtr(buf,0))
			buf = incBytePtr(buf, 1)
			// TODO: port this
			pkt.m_nBodySize = C.AMF_DecodeInt24((*C.char)(buf))
			buf = incBytePtr(buf, 3)
			// TODO: replace with ported version
			pkt.m_nTimeStamp = C.AMF_DecodeInt24((*C.char)(buf))
			buf = incBytePtr(buf, 3)
			pkt.m_nTimeStamp |= C.uint(indxBytePtr(buf,0)) << 24
			buf = incBytePtr(buf, 4)
			s2 -= 11

			if ((pkt.m_packetType == RTMP_PACKET_TYPE_AUDIO ||
				pkt.m_packetType == RTMP_PACKET_TYPE_VIDEO) &&
				pkt.m_nTimeStamp == 0) || pkt.m_packetType == RTMP_PACKET_TYPE_INFO {

				pkt.m_headerType = RTMP_PACKET_SIZE_LARGE

				if pkt.m_packetType == RTMP_PACKET_TYPE_INFO {
					pkt.m_nBodySize += 16
				}
			} else {
				pkt.m_headerType = RTMP_PACKET_SIZE_MEDIUM
			}
			// TODO: Port this
			if int(C.RTMPPacket_Alloc(pkt, pkt.m_nBodySize)) == 0 {
				log.Println("Failed to allocate packet")
				return 0
			}

			enc = unsafe.Pointer(pkt.m_body)
			pend = incBytePtr(enc, int(pkt.m_nBodySize))

			if pkt.m_packetType == RTMP_PACKET_TYPE_INFO {
				// TODO: Port this
				enc = unsafe.Pointer(C.AMF_EncodeString((*C.char)(enc), (*C.char)(pend), &setDataFrame))
				pkt.m_nBytesRead = C.uint(math.Abs(float64(uintptr(enc) -
					uintptr(unsafe.Pointer(pkt.m_body)))))
			}

		} else {
			enc = incBytePtr(unsafe.Pointer(pkt.m_body), int(pkt.m_nBytesRead))
		}
		num = int(pkt.m_nBodySize - pkt.m_nBytesRead)
		if num > s2 {
			num = s2
		}

		memmove(enc,buf,uintptr(num))
		//copy(ptrToSlice(enc, num), ptrToSlice(buf, num))
		pkt.m_nBytesRead += C.uint(num)
		s2 -= num
		buf = incBytePtr(buf, num)
		if pkt.m_nBytesRead == pkt.m_nBodySize {
			// TODO: Port this
			ret = int(C.RTMP_SendPacket(r, pkt, 0))
			// TODO: Port this
			C.RTMPPacket_Free(pkt)
			pkt.m_nBytesRead = 0
			if ret == 0 {
				return -1
			}
			buf = incBytePtr(buf, 4)
			s2 -= 4
			if s2 < 0 {
				break
			}
		}
	}
	return size + s2
}


func sendPacket(r *C.RTMP, packet *C.RTMPPacket, queue int) int {
	var prevPacket *C.RTMPPacket
	last := 0
	var nSize, hSize, cSize, nChunkSize, tlen int
	var header, hptr, hend, buffer, tbuf, toff unsafe.Pointer
	var goHbuf [C.RTMP_MAX_HEADER_SIZE]byte
	var hbuf = unsafe.Pointer(&goHbuf[0])
	var c byte
	var t int32

	if packet.m_nChannel >= r.m_channelsAllocatedOut {
		n := int(packet.m_nChannel+10)
		var tmp *C.RTMPPacket
		packets := C.realloc(unsafe.Pointer(r.m_vecChannelsOut),
			C.ulong(unsafe.Sizeof(tmp) * uintptr(n)))

		if uintptr(packets) == uintptr(0) {
			C.free(unsafe.Pointer(r.m_vecChannelsOut))
			r.m_vecChannelsOut = nil
			r.m_channelsAllocatedOut = 0
			return 0
		}
		r.m_vecChannelsOut = (**C.RTMPPacket)(packets)
		C.memset(incPtr(unsafe.Pointer(r.m_vecChannelsOut), int(r.m_channelsAllocatedOut),
			int(unsafe.Sizeof(tmp))), 0, C.ulong(unsafe.Sizeof(tmp) *
			uintptr(n-int(r.m_channelsAllocatedOut))))
		r.m_channelsAllocatedOut = C.int(n)
	}
	prevPacket = *(**C.RTMPPacket)(incPtr(unsafe.Pointer(r.m_vecChannelsOut),
		int(packet.m_nChannel), int(unsafe.Sizeof(packet))))

	if prevPacket != nil && packet.m_headerType != RTMP_PACKET_SIZE_LARGE {
		// compress a bit by using the prev packet's attributes
		if prevPacket.m_nBodySize == packet.m_nBodySize &&
			prevPacket.m_packetType == packet.m_packetType &&
			packet.m_headerType == RTMP_PACKET_SIZE_MEDIUM {

			packet.m_headerType = RTMP_PACKET_SIZE_SMALL
		}

		if prevPacket.m_nTimeStamp == packet.m_nTimeStamp &&
			packet.m_headerType == RTMP_PACKET_SIZE_SMALL {
			// TODO: port this constant
			packet.m_headerType = C.RTMP_PACKET_SIZE_MINIMUM
		}

		last = int(prevPacket.m_nTimeStamp)
	}

	if packet.m_headerType > 3 {
		log.Printf("Sanity failed! trying to send header of type: 0x%02x.",
			packet.m_headerType)
		return 0
	}

	nSize = int(*(*int)(incInt32Ptr(unsafe.Pointer(&packetSize[0]),int(packet.m_headerType))))
	hSize = nSize
	cSize = 0
	t = int32(int(packet.m_nTimeStamp) - last)

	if packet.m_body != nil {
		header = decPtr(unsafe.Pointer(packet.m_body), nSize,
		hend = packet.m_body
	} else {
		header = incPtr(hbuf,6)
		// TODO: be cautious about this sizeof - make sure it works how you think it
		// does. C code used sizeof(hbuf) where hbuf is a *char
		hend = incPtr(hbuf,unsafe.Sizeof((*byte)(hbuf)))
	}

	switch {
	case packet.m_nChannel > 319:
		cSize = 2
	case packet.m_nChannel > 63:
		cSize = 1
	}

	if cSize != 0 {
		header = decPtr(header,4)
		hSize = incPtr(hSize,4)
		log.Printf("Larger timsetamp than 24-bit: 0x%x", t)
	}

	hptr = header
	c = byte(packet.m_headerType) << 6

	switch cSize {
	case 0:
		c |= byte(packet.m_nChannel)
	case 1:
	case 2:
		c |= byte(1)
	}

	*(*byte)(hptr) = byte(tmp >> 8)
	hptr = incPtr(hptr,1)

	if nSize > 1 {
		res := t
		if t > 0xffffff {
			res = 0xffffff
		}
		hptr = unsafe.Pointer(AMF_EncodeInt24((*C.char)(hptr),(*C.char)(hend), res))
	}

	if nSize > 4 {
			*(*byte)(hptr) = byte(packet.m_packetType)
			hptr = unsafe.Pointer(AMF_EncodeInt24((*C.char)(hptr), (*C.char)(hend),
				packet.m_nbodySize))
	}

	if nSize > 8 {
		hptr = incPtr(hptr, int(EncodeInt32LE((*C.char)(hptr), packet.m_nInfoField2)))
	}

	if t >= 0xffffff {
		hptr = unsafe.Pointer(AMF_EncodeInt32((*C.char)(hptr), (*C.char)(hend), t))
	}

	nSize = int(packet.m_nBodySize)
	buffer = unsafe.Pointer(m_body)
	nChunkSize = int(r.m_outChunkSize)

	if debugMode {
		log.Printf("sendPacket: fd=%v, size=%v", r.m_sb.sb_socket, nSize)
	}

	// send all chunks in one HTTP request
	// TODO: port RTMP_FEATURE_HTTP
	if r.Link.protocol & C.RTMP_FEATURE_HTTP {
		chunks := (nSize+nChunkSize-1)/nChunkSize
		if chunks > 1 {
			tlen = chunks *(cSize+1) +nSize +hSize
			// TODO: figure out how to do this in go
			tbuf = C.malloc(tlen)

			if tbuf == 0 {
				return 0
			}
			toff = tbuf
		}
	}
	for (nSize + hSize) != 0 {
		var wrote int

		if nSize < nChunkSize {
			nChunkSize = nSize
		}

		// TODO: figure out what's happening here:
		// RTMP_LogHexString(RTMP_LOGDEBUG2, (uint8_t *)header, hSize);
		// RTMP_LogHexString(RTMP_LOGDEBUG2, (uint8_t *)buffer, nChunkSize);

		if tbuf != nil {
			memmove(toff, header, nChunksize + hSize)
			toff = incPtr(toff, nChunkSize + hSize)
		} else {
			// TODO: port this
			wrote = C.WriteN(r, (*C.char)(header), C.int(nChunkSize+hSize))

			if wrote == 0 {
				return 0
			}
		}

		nSize -= nChunkSize
		buffer = incPtr(buffer,nChunkSize)
		hSize = 0

		if nSize > 0 {
			header = decPtr(buffer, 1)
			hSize = 1

			if cSize != 0 {
				header = decPtr(header,1)
				hSize += cSize
			}

			if t >= 0xffffff {
				header = decPtr(header,4)
				hSize += 4
			}

			*(*byte)(header) = byte(0xc0 | c)

			if cSize != 0 {
				tmp := int(packet.m_nChannel) - 64
				indxBytePtr(header,1) = byte(tmp & 0xff)

				if cSize == 2 {
					indxBytePtr(header,2) = byte(tmp >> 8)
				}
			}
			if t >= 0xffffff {
				extendedTimestamp := incPtr(header,1+cSize)
				// TODO: port this
				C.AMF_EncodeInt32((*C.char)(extendedTimestamp),
					(*C.char)(incPtr(extendedTimestamp,4)), t)
			}
		}
	}

	if tbuf != 0 {
		// TODO: port C.writeN
		wrote := int(C.WriteN(r, (*C.char)(tbuf), (*C.char)(decPtr(toff,tbuf))))
		C.free((*C.char)(tbuf))
		tbuf = nil

		if wrote == 0 {
			return 0
		}
	}

	// We invoked a remote method
	// TODO: port the const
	if packet.m_packetType == C.RTMP_PACKET_TYPE_INVOKE {
		// TODO: port C.AVal
		var method C.AVal
		var ptr unsafe.Pointer
		ptr = incPtr(unsafe.Pointer(packet.m_body),1)
		// TODO: port this
		C.AMF_DecodeString((*C.char)(ptr), &method)

		if debugMode {
			log.Printf("Invoking %v", method.av_val)
		}
		// keep it in call queue till result arrives
		if queue != 0 {
			var txn int
			ptr = incPtr(ptr, 3 + int(method.av_len))
			// TODO: port this
			txn = int(C.AMF_DecodeNumber((*C.char)(ptr)))
			// TODO: port this
			C.AV_queue(&r.m_methodCalls, &r.m_numCalls, &method, C.int(txn))
		}
	}

	if indxPtr(unsafe.Pointer(r.m_vecChannelsOut),packet.m_nChannel) == 0 {
		(*C.char)(indxPtr(r.m_vecChannelsOut)) = C.malloc(unsafe.Sizof(C.RTMPPacket))
	}

	memmove(indxPtr(unsafe.Pointer(r.m_vecChannelsOut),packet.m_nChannel),
		unsafe.Pointer(packet), unsafe.Sizeof(C.RTMPPacket))

	return 1
}

/*
func writeN(r *C.RTMP, buffer unsafe.Pointer, n int) int {
	ptr := buffer
	for n > 0 {
		var nBytes int

		if r.Link.protocol & C.RTMP_FEATURE_HTTP {
			// TODO: port HTTP_POST
			nbytes = int(C.HTTP_POST(r, C.RTMPT_SEND, (*C.char)(ptr), C.int(n)))
		} else {
			// TODO: port this if necessary
			nBytes = RTMPSockBuf_Send(&r.m_sb, (*C.char)(ptr), C.int(n))
		}

		if nBytes < 0 {
			// TODO: port this
			sockerr := int(C.GetSockError())

			if debugMode {
				log.Printf("WriteN, RTMP send error %v (%v bytes)",sockerr, n)
			}

			if sockerr == C.EINTR && RTMP_ctrlC == 0 {
				continue
			}

			// TODO: port this
			C.RTMP_Close(r)
			n = 1
			break
		}

		if nBytes == 0 {
			break
		}

		n -= nBytes
		ptr = incPtr(ptr, nBytes)
	}

	return n == 0
}

// TODO: port RTMP_METHOD
func avQueue(vals **C.RTMP_METHOD, num *int, av *AVal, txn int ) {
	var tmp unsafe.Pointer

	if (*num & 0x0f) == 0 {
		// TODO: work out what to do with the realloc
		*vals = C.realloc(*vals, (*num+16) * C.int(int(unsafe.sizeof(RTMP_METHOD))))
	}

	tmp := C.malloc(av.av_len + 1 )
	memmove(tmp, unsafe.Pointer(av.av_val), int(av.av_len))
	indxPtr(tmp,av.av_len) = byte(nullChar)
}
*/

// memmove copies n bytes from "from" to "to".
//go:linkname memmove runtime.memmove
func memmove(to, from unsafe.Pointer, n uintptr)

// indxBytePtr returns a byte at the indx inc give a ptr
func indxBytePtr(ptr unsafe.Pointer, inc int) byte {
	return *(*byte)(incPtr(ptr, inc, byteSize))
}

// indxInt32Ptr returns an int32 at the indx inc given a ptr
func indxInt32Ptr(ptr unsafe.Pointer, inc int) int32 {
	return *(*int32)(incPtr(ptr, inc, int32Size))
}

// indxInt64Ptr returns an int64 at the indx inc given a ptr
func indxInt64Ptr(ptr unsafe.Pointer, inc int) int64 {
	return *(*int64)(incPtr(ptr, inc, int64Size))
}

// incBytePtr returns an unsafe.Pointer to a byte that is inc positive positions
// from the passed ptr
func incBytePtr(ptr unsafe.Pointer, inc int) unsafe.Pointer {
	return incPtr(ptr,inc,byteSize)
}

// incInt32Ptr returns an unsafe.Pointer to an int32 that is inc positive
// positions from the passed ptr
func incInt32Ptr(ptr unsafe.Pointer, inc int) unsafe.Pointer {
	return incPtr(ptr,inc,int32Size)
}

// incInt64Ptr returns an unsafe.Pointer to an int64 that is inc positive
// positions from the passed ptr
func incInt64Ptr(ptr unsafe.Pointer, inc int) unsafe.Pointer {
	return incPtr(ptr,inc,int64Size)
}

// incPtr attempts to replicate C like pointer arithmatic functionality
func incPtr(ptr unsafe.Pointer, inc, typeSize int) unsafe.Pointer {
	return unsafe.Pointer(uintptr(ptr) + uintptr(inc*typeSize))
}

// incPtr attempts to replicate C like pointer arithmatic functionality
func decPtr(ptr unsafe.Pointer, dec, typeSize int) unsafe.Pointer {
	return unsafe.Pointer(uintptr(ptr) - uintptr(dec*typeSize))
}

// decBytePtr returns an unsafe.Pointer to a byte that is dec negative positions
// from ptr
func decBytePtr(ptr unsafe.Pointer, dec int) unsafe.Pointer {
	return decPtr(ptr,dec,byteSize)
}

// decBytePtr returns an unsafe.Pointer to a int32 that is dec negative positions
// from ptr
func decInt32Ptr(ptr unsafe.Pointer, dec int) unsafe.Pointer {
	return decPtr(ptr,dec,int32Size)
}

// decBytePtr returns an unsafe.Pointer to a int64 that is dec negative positions
// from ptr
func decInt64Ptr(ptr unsafe.Pointer, dec int) unsafe.Pointer {
	return decPTr(ptr,dec,int64Size)
}

// sliceToPtr get's the address of the first data element and returns as unsafe
// pointer
func sliceToPtr(data []byte) unsafe.Pointer {
	return unsafe.Pointer(&data[0])
}

// ptrToSlice returns a slice given unsafe pointer and size - no allocation and
// copying is required - same data is used.
func ptrToSlice(data unsafe.Pointer, size int) []byte {
	var ret []byte
	shDest := (*reflect.SliceHeader)(unsafe.Pointer(&ret))
	shDest.Data = uintptr(data)
	shDest.Len = size
	shDest.Cap = size
	return ret
}

var rtmpErrs = [...]string{
	1: "rtmp: not connected",
	2: "rtmp: write error",
	3: "rtmp: not started",
}

type Err uint

func (e Err) Error() string {
	if 0 <= int(e) && int(e) < len(rtmpErrs) {
		s := rtmpErrs[e]
		if s != "" {
			return s
		}
	}
	return "rtmp: " + strconv.Itoa(int(e))
}