// 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 input"

pri status "#internal error: inconsistent I/O"

pub struct decoder? implements base.token_decoder(
	end_of_data : base.bool,

	util : base.utility,
)(
)

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

pub func decoder.workbuf_len() base.range_ii_u64 {
	return this.util.empty_range_ii_u64()
}

pub func decoder.decode_tokens?(dst: base.token_writer, src: base.io_reader, workbuf: slice base.u8) {
	var depth        : base.u32[..= 1024]
	var token_length : base.u32[..= 9]
	var c            : base.u8

	if this.end_of_data {
		return base."@end of data"
	}

	while.outer true {
		while.goto_parsed_a_leaf_value true {{
		if args.dst.available() <= 0 {
			yield? base."$short write"
			continue.outer
		}
		if args.src.available() <= 0 {
			if args.src.is_closed() {
				return "#bad input"
			}
			yield? base."$short read"
			continue.outer
		}
		c = args.src.peek_u8()
		if (0x18 <= (c & 0x1F)) and ((c & 0x1F) <= 0x1B) {
			token_length = 1 + ((1 as base.u32) << (c & 0x03))
			if args.src.available() < (token_length as base.u64) {
				if args.src.is_closed() {
					return "#bad input"
				}
				yield? base."$short read"
				continue.outer
			}
			args.src.skip_u32?(n: token_length)
		} else {
			args.src.skip_u32_fast!(actual: 1, worst_case: 1)
		}

		if c < 0x20 {
			c &= 0x1F
			if c < 0x18 {
				args.dst.write_simple_token_fast!(
					value_major: 0,
					value_minor: (base.TOKEN__VBC__INLINE_INTEGER << 21) |
					(c as base.u32),
					continued: 0,
					length: 1)
				break.goto_parsed_a_leaf_value
			} else if c < 0x1C {
				args.dst.write_simple_token_fast!(
					value_major: 0,
					value_minor: (base.TOKEN__VBC__NUMBER << 21) |
					base.TOKEN__VBD__NUMBER__CONTENT_INTEGER_UNSIGNED |
					base.TOKEN__VBD__NUMBER__FORMAT_BINARY_BIG_ENDIAN |
					base.TOKEN__VBD__NUMBER__FORMAT_IGNORE_FIRST_BYTE,
					continued: 0,
					length: 1 + ((1 as base.u32) << (c - 0x18)))
				break.goto_parsed_a_leaf_value
			}
		}

		if args.src.can_undo_byte() {
			args.src.undo_byte!()
			return "#bad input"
		}
		return "#internal error: inconsistent I/O"
		}} endwhile.goto_parsed_a_leaf_value

		// We've just parsed a leaf (non-container) value: literal (null,
		// false, true), number or string.
		if depth == 0 {
			break.outer
		}
	} endwhile.outer

	this.end_of_data = true
}