# WebAssembly cross-build via Emscripten.
#
# Includes Emscripten's own platform toolchain (found through $EMSDK, set by the
# emsdk image / `emsdk_env.sh`) and then layers the project's requirements:
#
#  * C++26 `import std;`. Emscripten ships the libc++ `std` module source and a
#    modules.json in its sysroot; its toolchain wires that up, but only if
#    `CMAKE_CXX_MODULE_STD` is on and no std-modules JSON has been set yet, so
#    both are arranged before Emscripten.cmake is included and before the
#    compiler is probed.
#  * Global `-fexceptions`. Emscripten disables exceptions by default, and the
#    libc++ `std` module must be built with the same setting as its consumers,
#    or clang rejects the prebuilt module ("configuration mismatch"). The engine
#    throws, so exceptions are enabled everywhere.
#  * Asyncify turns `emscripten_sleep` (used by display::sleep_frame on
#    Emscripten) into a yield: the engine's frame loops are blocking, and without
#    yielding the worker freezes and never paints.
#
# No pthreads: the runtime's main thread runs inside a plain Web Worker started
# by `apps/web/openra3.worker.js`, so its virtual filesystem is local to that
# worker and `FS.createLazyFile` (synchronous XHR) is legal. Under
# `PROXY_TO_PTHREAD` Emscripten proxies every filesystem syscall to the main
# browser thread, where synchronous XHR is forbidden, so lazy assets cannot work
# there - hence the plain worker. The SDL3 web port is only pulled in by the
# legacy main-thread backend (OPENRA3_WASM_SDL).

# `import std` support: the gate and the module switch must be in place before
# Emscripten.cmake runs and before the compiler is probed.
set(CMAKE_EXPERIMENTAL_CXX_IMPORT_STD "d0edc3af-4c50-42ea-a356-e2862fe7a444")
set(CMAKE_CXX_MODULE_STD ON)
# Let Emscripten.cmake point CMake at its own sysroot modules.json.
unset(CMAKE_CXX_STDLIB_MODULES_JSON)

if(DEFINED ENV{EMSDK})
    set(OPENRA3_EMSCRIPTEN_CMAKE "$ENV{EMSDK}/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake")
elseif(DEFINED ENV{EMSCRIPTEN_ROOT})
    set(OPENRA3_EMSCRIPTEN_CMAKE "$ENV{EMSCRIPTEN_ROOT}/cmake/Modules/Platform/Emscripten.cmake")
endif()
if(NOT EXISTS "${OPENRA3_EMSCRIPTEN_CMAKE}")
    message(FATAL_ERROR "Emscripten.cmake not found (set EMSDK); looked at '${OPENRA3_EMSCRIPTEN_CMAKE}'")
endif()
include("${OPENRA3_EMSCRIPTEN_CMAKE}")

# Exceptions are used by the engine; keep them on globally so the std module and
# its consumers agree.
#
# Asyncify turns `emscripten_sleep` (used by display::sleep_frame on Emscripten)
# into a yield to the browser: the engine's frame loops are blocking, and
# without yielding the worker freezes and never paints.
set(CMAKE_CXX_FLAGS_INIT "-fexceptions -sASYNCIFY=1")
set(CMAKE_C_FLAGS_INIT "-sASYNCIFY=1")
set(CMAKE_EXE_LINKER_FLAGS_INIT
    "-fexceptions -sDISABLE_EXCEPTION_CATCHING=0 -sALLOW_MEMORY_GROWTH=1 -sASYNCIFY=1")
set(CMAKE_SHARED_LINKER_FLAGS_INIT
    "-fexceptions -sDISABLE_EXCEPTION_CATCHING=0 -sALLOW_MEMORY_GROWTH=1 -sASYNCIFY=1")