/*
DESCRIPTION
  jpeg.go contains constants, structure and functions specific to the JPEG.

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

LICENSE
  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 mjpeg

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"io"
)

// JPEG marker codes.
const (
	codeSOI  = 0xd8 // Start of image.
	codeDRI  = 0xdd // Define restart interval.
	codeDQT  = 0xdb // Define quantization tables.
	codeDHT  = 0xc4 // Define huffman tables.
	codeSOS  = 0xda // Start of scan.
	codeAPP0 = 0xe0 // TODO: find out what this is.
	codeSOF0 = 0xc0 // Baseline
	codeEOI  = 0xd9 // End of image.
)

var (
	bitsDCLum = []byte{0, 0, 1, 5, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0}
	bitsDCChr = []byte{0, 0, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0}
	bitsACLum = []byte{0, 0, 2, 1, 3, 3, 2, 4, 3, 5, 5, 4, 4, 0, 0, 1, 0x7d}
	bitsACChr = []byte{0, 0, 2, 1, 2, 4, 4, 3, 4, 7, 5, 4, 4, 0, 1, 2, 0x77}
	valDC     = []byte{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11}
	valACLum  = []byte{
		0x01, 0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12,
		0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07,
		0x22, 0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08,
		0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0,
		0x24, 0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16,
		0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28,
		0x29, 0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39,
		0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49,
		0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59,
		0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69,
		0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79,
		0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89,
		0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98,
		0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
		0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6,
		0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5,
		0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4,
		0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2,
		0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea,
		0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
		0xf9, 0xfa,
	}

	valACChr = []byte{
		0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21,
		0x31, 0x06, 0x12, 0x41, 0x51, 0x07, 0x61, 0x71,
		0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91,
		0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33, 0x52, 0xf0,
		0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34,
		0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19, 0x1a, 0x26,
		0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38,
		0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48,
		0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58,
		0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68,
		0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
		0x79, 0x7a, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
		0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96,
		0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5,
		0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4,
		0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3,
		0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2,
		0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda,
		0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9,
		0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8,
		0xf9, 0xfa,
	}
)

type multiError []error

func (me multiError) Error() string {
	return fmt.Sprintf("%v", []error(me))
}

func (me multiError) add(e error) {
	me = append(me, e)
}

type putter struct {
	idx int
}

func (p *putter) put16(b []byte, v uint16) {
	binary.BigEndian.PutUint16(b[p.idx:], v)
	p.idx += 2
}

func (p *putter) put8(b []byte, v uint8) {
	b[p.idx] = byte(v)
	p.idx++
}

func (p *putter) putBuf(dst, src []byte, l int) {
	copy(dst[p.idx:], src)
	p.idx++
}

// writeHeader writes a JPEG header to the writer w.
func writeHeader(w io.Writer, _type, width, height, nbqTab, dri int, qtable []byte) error {
	width <<= 3
	height <<= 3

	// Indicate start of image.
	err := writeMarker(w, codeSOI)
	if err != nil {
		return fmt.Errorf("could not write SOI marker: %w", err)
	}

	err = writeMarker(w, codeAPP0)
	if err != nil {
		return fmt.Errorf("could not write APP0 marker: %w", err)
	}

	// Write JFIF header.
	b := make([]byte, 16)
	p := putter{}
	p.put16(b, 16)
	p.putBuf(b, []byte("JFIF"), 5)
	p.put16(b, 0x0201)
	p.put8(b, 0)
	p.put16(b, 1)
	p.put16(b, 1)
	p.put8(b, 0)
	p.put8(b, 0)
	_, err = w.Write(b)
	if err != nil {
		return fmt.Errorf("could not write JFIF header: %w", err)
	}

	// If we want to define restart interval.
	if dri != 0 {
		err = writeMarker(w, codeDRI)
		if err != nil {
			return fmt.Errorf("could not write DRI marker code: %w", err)
		}

		_, err := w.Write([]byte{0x00, 0x04, byte(dri >> 8), byte(dri)})
		if err != nil {
			return fmt.Errorf("could not write restart interval value: %w", err)
		}
	}

	// Define quantization tables.
	err = writeMarker(w, codeDQT)
	if err != nil {
		return fmt.Errorf("could not write DQI marker code: %w", err)
	}

	// Calculate table size and create slice for table.
	ts := 2 + nbqTab*(1+64)
	_, err = w.Write([]byte{byte(ts >> 8), byte(ts)})
	if err != nil {
		return fmt.Errorf("could not write quantization table size: %w", err)
	}

	for i := 0; i < nbqTab; i++ {
		_, err = w.Write([]byte{byte(i)})
		if err != nil {
			return fmt.Errorf("could not write quantization table entry no.: %w", err)
		}

		_, err = w.Write(qtable[64*i : (64*i)+64])
		if err != nil {
			return fmt.Errorf("could not write quantization table entry: %w", err)
		}
	}

	// Define huffman table.
	err = writeMarker(w, codeDHT)
	if err != nil {
		return fmt.Errorf("could not write DHT marker code: %w", err)
	}

	var me multiError
	buf := new(bytes.Buffer)
	me.add(writeHuffman(buf, 0, 0, bitsDCLum, valDC))
	me.add(writeHuffman(buf, 0, 1, bitsDCChr, valDC))
	me.add(writeHuffman(buf, 1, 0, bitsACLum, valACLum))
	me.add(writeHuffman(buf, 1, 1, bitsACChr, valACChr))
	if me != nil {
		return fmt.Errorf("error writing huffman tables: %w", err)
	}

	l := buf.Len() + 2
	_, err = w.Write([]byte{byte(l >> 8), byte(l)})
	if err != nil {
		return fmt.Errorf("could not write quantization table entry: %w", err)
	}

	_, err = buf.WriteTo(w)
	if err != nil {
		return fmt.Errorf("could not write huffman tables: %w", err)
	}

	// Start of frame.
	err = writeMarker(w, codeSOF0)
	if err != nil {
		return fmt.Errorf("could not write SOF0 marker code: %w", err)
	}

	// Derive sample type.
	sample := 1
	if _type != 0 {
		sample = 2
	}

	// Derive matrix number.
	mtxNo := 0
	if nbqTab == 2 {
		mtxNo = 1
	}

	b = make([]byte, 17)
	p = putter{}
	p.put16(b, 17)
	p.put8(b, 8)
	p.put16(b, uint16(height))
	p.put16(b, uint16(width))
	p.put8(b, 3)
	p.put8(b, 1)
	p.put8(b, uint8((2<<4)|sample))
	p.put8(b, 0)
	p.put8(b, 2)
	p.put8(b, 1<<4|1)
	p.put8(b, uint8(mtxNo))
	p.put8(b, 3)
	p.put8(b, 1<<4|1)
	p.put8(b, uint8(mtxNo))
	_, err = w.Write(b)
	if err != nil {
		return fmt.Errorf("could not write SOF0 info: %w", err)
	}

	// Write start of scan.
	err = writeMarker(w, codeSOS)
	if err != nil {
		return fmt.Errorf("could not write SOS marker code: %w", err)
	}

	b = make([]byte, 12)
	p = putter{}
	p.put16(b, 12)
	p.put8(b, 3)
	p.put8(b, 1)
	p.put8(b, 0)
	p.put8(b, 2)
	p.put8(b, 17)
	p.put8(b, 3)
	p.put8(b, 17)
	p.put8(b, 0)
	p.put8(b, 63)
	p.put8(b, 0)
	_, err = w.Write(b)
	if err != nil {
		return fmt.Errorf("could not write SOS info: %w", err)
	}

	return nil
}

// writeMarker writes an JPEG marker with code to w.
func writeMarker(w io.Writer, code byte) error {
	_, err := w.Write([]byte{0xff, code})
	if err != nil {
		return err
	}
	return nil
}

// writeHuffman write a JPEG huffman table to w.
func writeHuffman(w io.Writer, class, id int, bits, values []byte) error {
	_, err := w.Write([]byte{byte(class<<4 | id)})
	if err != nil {
		return fmt.Errorf("could not write class and id: %w", err)
	}

	var n int
	for i := 1; i <= 16; i++ {
		n += int(bits[i])
	}

	_, err = w.Write(bits[1:17])
	if err != nil {
		return fmt.Errorf("could not write first lot of huffman bytes: %w", err)
	}

	_, err = w.Write(values[0:n])
	if err != nil {
		return fmt.Errorf("could not write second lot of huffman bytes: %w", err)
	}

	return nil
}