package rle

import "fmt"

func decompress3(output *[]uint8, width, height int, input []uint8, size int) bool {
	var (
		prevline, line, count            int
		opcode, offset, code             int
		x                                int = width
		lastopcode                       int = -1
		insertmix, bicolour, isfillormix bool
		mixmask, mask                    uint8
		colour1                          = [3]uint8{0, 0, 0}
		colour2                          = [3]uint8{0, 0, 0}
		mix                              = [3]uint8{0xff, 0xff, 0xff}
		fom_mask                         uint8
	)
	out := *output
	for len(input) != 0 {
		fom_mask = 0
		code = CVAL(&input)
		opcode = code >> 4
		/* Handle different opcode forms */
		switch opcode {
		case 0xc, 0xd, 0xe:
			opcode -= 6
			count = code & 0xf
			offset = 16
			break
		case 0xf:
			opcode = code & 0xf
			if opcode < 9 {
				count = CVAL(&input)
				count |= CVAL(&input) << 8
			} else {
				count = 1
				if opcode < 0xb {
					count = 8
				}
			}
			offset = 0
			break
		default:
			opcode >>= 1
			count = code & 0x1f
			offset = 32
			break
		}

		/* Handle strange cases for counts */
		if offset != 0 {
			isfillormix = ((opcode == 2) || (opcode == 7))
			if count == 0 {
				if isfillormix {
					count = CVAL(&input) + 1
				} else {
					count = CVAL(&input) + offset
				}
			} else if isfillormix {
				count <<= 3
			}
		}
		/* Read preliminary data */
		switch opcode {
		case 0: /* Fill */
			if (lastopcode == opcode) && !((x == width) && (prevline == 0)) {
				insertmix = true
			}
			break
		case 8: /* Bicolour */
			CVAL3(&input, &colour1)
			CVAL3(&input, &colour2)
			break
		case 3: /* Colour */
			CVAL3(&input, &colour2)
			break
		case 6: /* SetMix/Mix */
			fallthrough
		case 7: /* SetMix/FillOrMix */
			CVAL3(&input, &mix)
			opcode -= 5
			break
		case 9: /* FillOrMix_1 */
			mask = 0x03
			opcode = 0x02
			fom_mask = 3
			break
		case 0x0a: /* FillOrMix_2 */
			mask = 0x05
			opcode = 0x02
			fom_mask = 5
			break
		}

		lastopcode = opcode
		mixmask = 0
		/* Output body */
		for count > 0 {
			if x >= width {
				if height <= 0 {
					return false
				}

				x = 0
				height--
				prevline = line
				line = height * width * 3
			}
			switch opcode {
			case 0: /* Fill */
				if insertmix {
					if prevline == 0 {
						out[3*x+line] = mix[0]
						out[3*x+line+1] = mix[1]
						out[3*x+line+2] = mix[2]
					} else {
						out[3*x+line] = out[prevline+3*x] ^ mix[0]
						out[3*x+line+1] = out[prevline+3*x+1] ^ mix[1]
						out[3*x+line+2] = out[prevline+3*x+2] ^ mix[2]
					}
					insertmix = false
					count--
					x++
				}
				n := min(count, width-x)
				if prevline == 0 {
					clear(out[3*x+line : 3*x+line+3*n])
				} else {
					dstBase := 3*x + line
					srcBase := prevline + 3*x
					copy(out[dstBase:dstBase+3*n], out[srcBase:srcBase+3*n])
				}
				count -= n
				x += n
				break
			case 1: /* Mix */
				n := min(count, width-x)
				dst1 := out[3*x+line : 3*x+line+3*n]
				if prevline == 0 {
					// Exponential-doubling copy: O(log n) memcpy calls
					dst1[0], dst1[1], dst1[2] = mix[0], mix[1], mix[2]
					for wrote := 3; wrote < len(dst1); {
						wrote += copy(dst1[wrote:], dst1[:wrote])
					}
				} else {
					src1 := out[prevline+3*x : prevline+3*x+3*n]
					for i := 0; i+2 < len(dst1); i += 3 {
						dst1[i] = src1[i] ^ mix[0]
						dst1[i+1] = src1[i+1] ^ mix[1]
						dst1[i+2] = src1[i+2] ^ mix[2]
					}
				}
				count -= n
				x += n
				break
			case 2: /* Fill or Mix */
				if prevline == 0 {
					base := 3*x + line
					for count > 0 && x < width {
						mixmask = mixmask << 1
						if mixmask == 0 {
							mask = fom_mask
							if fom_mask == 0 {
								mask = uint8(CVAL(&input))
								mixmask = 1
							}
						}
						if mask&mixmask != 0 {
							out[base] = mix[0]
							out[base+1] = mix[1]
							out[base+2] = mix[2]
						} else {
							out[base] = 0
							out[base+1] = 0
							out[base+2] = 0
						}
						base += 3
						count--
						x++
					}
				} else {
					base := 3*x + line
					prev := prevline + 3*x
					for count > 0 && x < width {
						mixmask = mixmask << 1
						if mixmask == 0 {
							mask = fom_mask
							if fom_mask == 0 {
								mask = uint8(CVAL(&input))
								mixmask = 1
							}
						}
						if mask&mixmask != 0 {
							out[base] = out[prev] ^ mix[0]
							out[base+1] = out[prev+1] ^ mix[1]
							out[base+2] = out[prev+2] ^ mix[2]
						} else {
							out[base] = out[prev]
							out[base+1] = out[prev+1]
							out[base+2] = out[prev+2]
						}
						base += 3
						prev += 3
						count--
						x++
					}
				}
				break
			case 3: /* Colour */
				n := min(count, width-x)
				seg3 := out[3*x+line : 3*x+line+3*n]
				seg3[0], seg3[1], seg3[2] = colour2[0], colour2[1], colour2[2]
				for wrote := 3; wrote < len(seg3); {
					wrote += copy(seg3[wrote:], seg3[:wrote])
				}
				count -= n
				x += n
				break
			case 4: /* Copy */
				for count > 0 && x < width {
					n := min(count, width-x)
					if len(input) < n*3 {
						return false
					}
					copy(out[3*x+line:3*x+line+n*3], input[:n*3])
					input = input[n*3:]
					count -= n
					x += n
				}
				break
			case 8: /* Bicolour */
				base8 := 3*x + line
				for count > 0 && x < width {
					if bicolour {
						out[base8] = colour2[0]
						out[base8+1] = colour2[1]
						out[base8+2] = colour2[2]
						bicolour = false
					} else {
						out[base8] = colour1[0]
						out[base8+1] = colour1[1]
						out[base8+2] = colour1[2]
						bicolour = true
						count++
					}
					base8 += 3
					count--
					x++
				}
				break
			case 0xd: /* White */
				n3 := min(count, width-x)
				seg3 := out[3*x+line : 3*x+line+3*n3]
				for i := range seg3 {
					seg3[i] = 0xff
				}
				count -= n3
				x += n3
				break
			case 0xe: /* Black */
				n2 := min(count, width-x)
				clear(out[3*x+line : 3*x+line+3*n2])
				count -= n2
				x += n2
				break
			default:
				fmt.Printf("bitmap opcode 0x%x\n", opcode)
				return false
			}
		}
	}

	return true
}

/* decompress a colour plane */
func processPlane(in *[]uint8, width, height int, output *[]uint8, j int) (int, bool) {
	var (
		indexw   int
		indexh   int
		code     int
		collen   int
		replen   int
		color    uint8
		x        uint8
		revcode  int
		lastline int
		thisline int
	)
	ln := len(*in)
	out := *output // hoist pointer dereference; writes to out[i] affect the underlying array

	readByte := func() (uint8, bool) {
		if len(*in) == 0 {
			return 0, false
		}
		v := (*in)[0]
		*in = (*in)[1:]
		return v, true
	}
	writePixel := func(pos int, value uint8) bool {
		if pos < 0 || pos >= len(out) {
			return false
		}
		out[pos] = value
		return true
	}

	lastline = 0
	indexh = 0
	i := 0
	for indexh < height {
		thisline = j + (width * height * 4) - ((indexh + 1) * width * 4)
		color = 0
		indexw = 0
		i = thisline

		if lastline == 0 {
			for indexw < width {
				b, ok := readByte()
				if !ok {
					return ln - len(*in), false
				}
				code = int(b)
				replen = int(code & 0xf)
				collen = int((code >> 4) & 0xf)
				revcode = (replen << 4) | collen
				if (revcode <= 47) && (revcode >= 16) {
					replen = revcode
					collen = 0
				}
				for collen > 0 {
					if indexw >= width {
						return ln - len(*in), false
					}
					v, ok := readByte()
					if !ok {
						return ln - len(*in), false
					}
					color = v
					if !writePixel(i, color) {
						return ln - len(*in), false
					}
					i += 4

					indexw++
					collen--
				}
				for replen > 0 {
					if indexw >= width {
						break
					}
					if !writePixel(i, color) {
						return ln - len(*in), false
					}
					i += 4
					indexw++
					replen--
				}
			}
		} else {
			// prevOffset is constant per row: indexw*4+lastline == i+(lastline-thisline)
			// because i == thisline+indexw*4. Pre-computing it eliminates a multiply
			// per pixel in both inner loops.
			prevOffset := lastline - thisline
			for indexw < width {
				b, ok := readByte()
				if !ok {
					return ln - len(*in), false
				}
				code = int(b)
				replen = int(code & 0xf)
				collen = int((code >> 4) & 0xf)
				revcode = (replen << 4) | collen
				if (revcode <= 47) && (revcode >= 16) {
					replen = revcode
					collen = 0
				}
				for collen > 0 {
					if indexw >= width {
						return ln - len(*in), false
					}
					v, ok := readByte()
					if !ok {
						return ln - len(*in), false
					}
					x = v
					if x&1 != 0 {
						x = x >> 1
						x = x + 1
						color = -x
					} else {
						x = x >> 1
						color = x
					}
					if i+prevOffset < 0 || i+prevOffset >= len(out) {
						return ln - len(*in), false
					}
					x = out[i+prevOffset] + color
					if !writePixel(i, x) {
						return ln - len(*in), false
					}
					i += 4
					indexw++
					collen--
				}
				for replen > 0 {
					if indexw >= width {
						break
					}
					if i+prevOffset < 0 || i+prevOffset >= len(out) {
						return ln - len(*in), false
					}
					x = out[i+prevOffset] + color
					if !writePixel(i, x) {
						return ln - len(*in), false
					}
					i += 4
					indexw++
					replen--
				}
			}
		}
		indexh++
		lastline = thisline
	}
	return ln - len(*in), true
}

/* 4 byte bitmap decompress */