________________________________________________________________________

This file is part of Logtalk <https://logtalk.org/>
SPDX-FileCopyrightText: 1998-2026 Paulo Moura <pmoura@logtalk.org>
SPDX-License-Identifier: Apache-2.0

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

    http://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
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`wkt_wkb`
=========

The `wkt_wkb` library provides predicates for parsing, generating, and
validating geometries represented using the Well-Known Text (WKT) and
Well-Known Binary (WKB) interchange formats.

It complements the `geojson` and `geospatial` libraries by reusing the same
geometry constructors while adding support for the standard text and binary
geometry encodings widely used by spatial databases and GIS tooling.


API documentation
-----------------

Open the [../../apis/library_index.html#wkt_wkb](../../apis/library_index.html#wkt_wkb)
link in a web browser.


Loading
-------

To load all entities in this library, load the `loader.lgt` file:

	| ?- logtalk_load(wkt_wkb(loader)).


Testing
-------

To test this library predicates, load the `tester.lgt` file:

	| ?- logtalk_load(wkt_wkb(tester)).


Representation
--------------

The library uses the same native geometry constructors as the `geojson`
library for geometry values:

- `point(Position)` or `point(Position, Options)`
- `multi_point(Positions)` or `multi_point(Positions, Options)`
- `line_string(Positions)` or `line_string(Positions, Options)`
- `multi_line_string(LineStrings)` or `multi_line_string(LineStrings, Options)`
- `polygon(Rings)` or `polygon(Rings, Options)`
- `multi_polygon(Polygons)` or `multi_polygon(Polygons, Options)`
- `geometry_collection(Geometries)` or `geometry_collection(Geometries, Options)`

Positions are represented as lists of numeric coordinates. Empty geometries
use empty lists, e.g. `point([])` or `polygon([])`.

The optional `Options` lists currently support:

- `dimensions(xy)`
- `dimensions(z)`
- `dimensions(m)`
- `dimensions(zm)`

The `dimensions/1` option is mainly required to distinguish `Z` and `M`
three-coordinate geometries and to preserve dimensionality for empty
geometries. When the option is omitted, dimensionality is inferred from the
coordinates and defaults to `xy` for empty geometries.


Sources and sinks
-----------------

WKT sources and sinks are wrapped as `wkt(...)` terms:

- `wkt(file(Path))`
- `wkt(stream(Stream))`
- `wkt(atom(Atom))`
- `wkt(chars(List))`
- `wkt(codes(List))`

WKB sources and sinks are wrapped as `wkb(...)` terms:

- `wkb(file(Path))`
- `wkb(stream(Stream))`
- `wkb(bytes(List))`
- `wkb(hex(atom(Atom)))`
- `wkb(hex(chars(List)))`
- `wkb(hex(codes(List)))`

When generating WKB, byte order defaults to little-endian. A specific byte
order can be selected using `wkb(Sink, little)` or `wkb(Sink, big)`.


Examples
--------

Parse a WKT point:

	| ?- wkt_wkb::parse(wkt(atom('POINT Z (1 2 3)')), Geometry).
	Geometry = point([1, 2, 3], [dimensions(z)])
	yes

Generate canonical WKT for a polygon:

	| ?- wkt_wkb::generate(wkt(atom(WKT)), polygon([[[0,0],[1,0],[1,1],[0,1],[0,0]]])).
	WKT = 'POLYGON ((0 0, 1 0, 1 1, 0 1, 0 0))'
	yes

Generate WKB hex for a point:

	| ?- wkt_wkb::generate(wkb(hex(atom(Hex))), point([1, 2])).
	Hex = '0101000000000000000000f03f0000000000000040'
	yes

Round-trip through a big-endian WKB byte sequence:

	| ?- wkt_wkb::generate(wkb(bytes(Bytes), big), line_string([[0,0],[1,1]])),
	     wkt_wkb::parse(wkb(bytes(Bytes)), Geometry).

Validate a geometry term:

	| ?- wkt_wkb::validate(multi_point([[], [1, 2], [3, 4]])).
	yes

	| ?- wkt_wkb::validate(polygon([[[0,0],[1,0],[1,1],[0,1]]]), Errors).
	Errors = [ring_not_closed([coordinates,0])]
	yes


Notes
-----

- WKT parsing accepts the standard geometry keywords `POINT`, `LINESTRING`,
	`POLYGON`, `MULTIPOINT`, `MULTILINESTRING`, `MULTIPOLYGON`, and
	`GEOMETRYCOLLECTION`, together with the `Z`, `M`, and `ZM` dimension tags.
- Canonical WKT generation always uses uppercase geometry keywords.
- WKB generation uses the ISO/OGC type-code offsets `1000`, `2000`, and
	`3000` for `Z`, `M`, and `ZM` dimensionality.
- Empty WKB points are encoded using quiet NaN ordinates as required by the
	format, while empty non-point geometries are encoded using zero counts.
- Geometry validation checks coordinate dimensionality consistency, minimum
	cardinalities for line strings and rings, and polygon ring closure.
