// Copyright 2020 The Wuffs Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

pub status "#bad header"
pub status "#truncated input"
pub status "#unsupported NIE file"

pri status "@internal note: short read"

pub const DECODER_WORKBUF_LEN_MAX_INCL_WORST_CASE : base.u64 = 0

pub struct decoder? implements base.image_decoder(
	pixfmt : base.u32,
	width  : base.u32[..= 0x7FFF_FFFF],
	height : base.u32[..= 0x7FFF_FFFF],

	// The call sequence state machine is discussed in
	// (/doc/std/image-decoders-call-sequence.md).
	call_sequence : base.u8,

	dst_x : base.u32,
	dst_y : base.u32,

	swizzler : base.pixel_swizzler,
	util     : base.utility,
)

pub func decoder.set_quirk_enabled!(quirk: base.u32, enabled: base.bool) {
}

pub func decoder.decode_image_config?(dst: nptr base.image_config, src: base.io_reader) {
	var status : base.status

	while true {
		status =? this.do_decode_image_config?(dst: args.dst, src: args.src)
		if (status == base."$short read") and args.src.is_closed() {
			return "#truncated input"
		}
		yield? status
	} endwhile
}

pri func decoder.do_decode_image_config?(dst: nptr base.image_config, src: base.io_reader) {
	var a : base.u32

	if this.call_sequence <> 0x00 {
		return base."#bad call sequence"
	}

	a = args.src.read_u32le?()
	if a <> 'nïE'le {
		return "#bad header"
	}

	a = args.src.read_u32le?()
	if a == '\xFFbn4'le {
		this.pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL
	} else if a == '\xFFbn8'le {
		this.pixfmt = base.PIXEL_FORMAT__BGRA_NONPREMUL_4X16LE
	} else if a == '\xFFbp4'le {
		return "#unsupported NIE file"
	} else if a == '\xFFbp8'le {
		return "#unsupported NIE file"
	} else {
		return "#bad header"
	}

	a = args.src.read_u32le?()
	if a >= 0x8000_0000 {
		return "#bad header"
	}
	this.width = a

	a = args.src.read_u32le?()
	if a >= 0x8000_0000 {
		return "#bad header"
	}
	this.height = a

	if args.dst <> nullptr {
		args.dst.set!(
			pixfmt: this.pixfmt,
			pixsub: 0,
			width: this.width,
			height: this.height,
			first_frame_io_position: 16,
			first_frame_is_opaque: false)
	}

	this.call_sequence = 0x20
}

pub func decoder.decode_frame_config?(dst: nptr base.frame_config, src: base.io_reader) {
	var status : base.status

	while true {
		status =? this.do_decode_frame_config?(dst: args.dst, src: args.src)
		if (status == base."$short read") and args.src.is_closed() {
			return "#truncated input"
		}
		yield? status
	} endwhile
}

pri func decoder.do_decode_frame_config?(dst: nptr base.frame_config, src: base.io_reader) {
	if this.call_sequence == 0x20 {
		// No-op.
	} else if this.call_sequence < 0x20 {
		this.do_decode_image_config?(dst: nullptr, src: args.src)
	} else if this.call_sequence == 0x28 {
		if 16 <> args.src.position() {
			return base."#bad restart"
		}
	} else if this.call_sequence == 0x40 {
		this.call_sequence = 0x60
		return base."@end of data"
	} else {
		return base."@end of data"
	}

	if args.dst <> nullptr {
		args.dst.set!(bounds: this.util.make_rect_ie_u32(
			min_incl_x: 0,
			min_incl_y: 0,
			max_excl_x: this.width,
			max_excl_y: this.height),
			duration: 0,
			index: 0,
			io_position: 16,
			disposal: 0,
			opaque_within_bounds: false,
			overwrite_instead_of_blend: false,
			background_color: 0x0000_0000)
	}

	this.call_sequence = 0x40
}

pub func decoder.decode_frame?(dst: ptr base.pixel_buffer, src: base.io_reader, blend: base.pixel_blend, workbuf: slice base.u8, opts: nptr base.decode_frame_options) {
	var status : base.status

	while true {
		status =? this.do_decode_frame?(dst: args.dst, src: args.src, blend: args.blend, workbuf: args.workbuf, opts: args.opts)
		if (status == base."$short read") and args.src.is_closed() {
			return "#truncated input"
		}
		yield? status
	} endwhile
}

pri func decoder.do_decode_frame?(dst: ptr base.pixel_buffer, src: base.io_reader, blend: base.pixel_blend, workbuf: slice base.u8, opts: nptr base.decode_frame_options) {
	var status : base.status

	if this.call_sequence == 0x40 {
		// No-op.
	} else if this.call_sequence < 0x40 {
		this.do_decode_frame_config?(dst: nullptr, src: args.src)
	} else {
		return base."@end of data"
	}

	this.dst_x = 0
	this.dst_y = 0

	status = this.swizzler.prepare!(
		dst_pixfmt: args.dst.pixel_format(),
		dst_palette: args.dst.palette(),
		src_pixfmt: this.util.make_pixel_format(repr: this.pixfmt),
		src_palette: this.util.empty_slice_u8(),
		blend: args.blend)
	if not status.is_ok() {
		return status
	}

	while true {
		status = this.swizzle!(dst: args.dst, src: args.src)
		if status.is_ok() {
			break
		} else if status <> "@internal note: short read" {
			return status
		}
		yield? base."$short read"
	} endwhile

	this.call_sequence = 0x60
}

pri func decoder.swizzle!(dst: ptr base.pixel_buffer, src: base.io_reader) base.status {
	var dst_pixfmt          : base.pixel_format
	var dst_bits_per_pixel  : base.u32[..= 256]
	var dst_bytes_per_pixel : base.u64[..= 32]
	var dst_bytes_per_row   : base.u64
	var tab                 : table base.u8
	var dst                 : slice base.u8
	var i                   : base.u64
	var n                   : base.u64

	// TODO: the dst_pixfmt variable shouldn't be necessary. We should be able
	// to chain the two calls: "args.dst.pixel_format().bits_per_pixel()".
	dst_pixfmt = args.dst.pixel_format()
	dst_bits_per_pixel = dst_pixfmt.bits_per_pixel()
	if (dst_bits_per_pixel & 7) <> 0 {
		return base."#unsupported option"
	}
	dst_bytes_per_pixel = (dst_bits_per_pixel / 8) as base.u64
	dst_bytes_per_row = (this.width as base.u64) * dst_bytes_per_pixel
	tab = args.dst.plane(p: 0)

	while true {
		if this.dst_x == this.width {
			this.dst_x = 0
			this.dst_y ~mod+= 1
			if this.dst_y >= this.height {
				break
			}
		}

		dst = tab.row_u32(y: this.dst_y)
		if dst_bytes_per_row < dst.length() {
			dst = dst[.. dst_bytes_per_row]
		}
		i = (this.dst_x as base.u64) * dst_bytes_per_pixel
		if i >= dst.length() {
			// TODO: advance args.src if the dst pixel_buffer bounds is
			// smaller than this NIE's image bounds?
			continue
		}
		n = this.swizzler.swizzle_interleaved_from_reader!(
			dst: dst[i ..],
			dst_palette: args.dst.palette(),
			src: args.src)
		if n == 0 {
			return "@internal note: short read"
		}
		this.dst_x ~sat+= (n & 0xFFFF_FFFF) as base.u32
	} endwhile

	return ok
}

pub func decoder.frame_dirty_rect() base.rect_ie_u32 {
	return this.util.make_rect_ie_u32(
		min_incl_x: 0,
		min_incl_y: 0,
		max_excl_x: this.width,
		max_excl_y: this.height)
}

pub func decoder.num_animation_loops() base.u32 {
	return 0
}

pub func decoder.num_decoded_frame_configs() base.u64 {
	if this.call_sequence > 0x20 {
		return 1
	}
	return 0
}

pub func decoder.num_decoded_frames() base.u64 {
	if this.call_sequence > 0x40 {
		return 1
	}
	return 0
}

pub func decoder.restart_frame!(index: base.u64, io_position: base.u64) base.status {
	if this.call_sequence < 0x20 {
		return base."#bad call sequence"
	}
	if (args.index <> 0) or (args.io_position <> 16) {
		return base."#bad argument"
	}
	this.call_sequence = 0x28
	return ok
}

pub func decoder.set_report_metadata!(fourcc: base.u32, report: base.bool) {
	// No-op. NIE doesn't support metadata.
}

pub func decoder.tell_me_more?(dst: base.io_writer, minfo: nptr base.more_information, src: base.io_reader) {
	return base."#no more information"
}

pub func decoder.workbuf_len() base.range_ii_u64 {
	return this.util.make_range_ii_u64(min_incl: 0, max_incl: 0)
}