Popeye Solver — third-party components and licensing
====================================================

1. Popeye  (vendor/py.js, vendor/py.wasm)
-----------------------------------------

Popeye is a chess problem solving program.
  Upstream: https://github.com/thomas-maeder/popeye
  Licence:  GNU General Public License, version 2. The full text is in
            COPYING, next to this file.

Authors
  Popeye was begun in 1983 by Philippe Schnoebelen, in a Pascal dialect under
  MS-DOS, and converted to C by Norbert Geissler. Version 4.103 credits, in
  its own py-engl.txt:

    Thomas Maeder, Stephen Emmerson, Norbert Geissler, Torsten Linss,
    Elmar Bartel, Joshua Green, Mu-Tsun Tsai

The files vendor/py.js and vendor/py.wasm are a compiled form of Popeye and
are therefore covered by the GPL.

Built from:
  tag        v4.103   (commit 8bf65b054482cae04fc36e07c6b880fb4f93c673)
  toolchain  Emscripten 6.0.9
  command    make -f makefile.unx TOOLCHAIN=emcc

Changes made to the upstream source
  popeye-build/popeye-4.103-emscripten.patch holds every change, and there are
  only four. No C source file was touched; the patch is confined to the
  Emscripten toolchain description.

    a) toolchains/emcc/make.incl, makefile.unx, .gitignore
       Cherry-picked from upstream's own feature/emcc branch
       (commit 6a8b140d26cc6b41f9457ab15fafb871826f7dd6, pull request #549,
       "Improve Emscripten support"). Modernises the link flags and adds the
       generated .wasm to the clobber list.

    b) -sENVIRONMENT=worker  ->  -sENVIRONMENT=worker,node
       So the same build can be run from node for regression testing.

    c) -sMIN_SAFARI_VERSION=120000  ->  150000
       Emscripten 6.0.9 refuses anything below 150000.

    d) OTHER += -Wno-c23-extensions
       Emscripten's clang is newer than the compilers upstream tests with and
       raises "enumerator value which exceeds the range of int" for
       optimisations/intelligent/proof.c, which upstream's -pedantic-errors
       turns into a hard error. Diagnostic only; no effect on code generation.

Corresponding source
  GPL v2 section 3(a) asks that object code be accompanied by the complete
  corresponding source. It is here, shipped beside the binary:

    popeye-build/popeye-4.103-wasm-src.tar.gz

  That archive is upstream v4.103 with the patch already applied — the exact
  tree py.wasm was built from. Nothing else is needed; it does not depend on
  upstream staying reachable.

  To rebuild from it:

    tar xzf popeye-build/popeye-4.103-wasm-src.tar.gz
    cd popeye-4.103-wasm
    source /path/to/emsdk/emsdk_env.sh      # Emscripten 6.0.9
    make -f makefile.unx TOOLCHAIN=emcc

  The build writes py.js and py.wasm into the source root; those are the two
  files in vendor/. With Emscripten 6.0.9 the result is byte-for-byte
  identical to what ships here — verified, SHA-256:

    py.js    c3a20d79dc7440d17104612d42fea20218a114c53d26698e603c284a27da4bf7
    py.wasm  ec9974550a7a34f63dd50669e3db8c646f52703c50f6ef36813aa9ce21069c3b

  popeye-build/popeye-4.103-emscripten.patch is the same change on its own,
  for reading rather than building.


2. Solution parser  (vendor/solution-parser.js)
-----------------------------------------------

Transpiled with esbuild from src/services/solutionParser.ts in the private
repository chess-problems (same author as this page). TypeScript types were
erased; nothing else was changed. Not third-party.


3. Piece artwork  (vendor/pieces.js)
------------------------------------

The cburnett chess piece set, as SVG path data.
  Licence: BSD.
Copied from chess-problems/local-experiments/anki-miniature/pieces.json and
converted from JSON to an ES module so the page needs no extra fetch.


4. Board renderer  (src/board.js)
---------------------------------

Adapted from chess-problems/local-experiments/anki-miniature/board-svg.mjs
(same author). Not third-party.