initial port to wasm

.bazelrc

@@ -45,3 +45,15 @@ build:tsan --linkopt=-fsanitize=thread
 build:tsan --strip=never
 build:tsan --features=dbg
 build:tsan --compilation_mode=dbg
+
+# WebAssembly (WASM) configuration
+# Usage: bazel build --config=wasm //...
+# Requires Emscripten SDK to be installed and em++ to be on PATH
+# Note: Users must set CC and CXX environment variables:
+#   export CC=emcc
+#   export CXX=em++
+#   export AR=emar
+build:wasm --cxxopt=-std=c++20
+build:wasm --host_cxxopt=-std=c++20
+build:wasm --compilation_mode=opt
+build:wasm --define=wasm=true

BUILD.bazel

@@ -72,6 +72,16 @@ config_setting(
     define_values = {"asan": "true"},
 )
 
+# WebAssembly (WASM) build configuration
+# Usage: bazel build --config=wasm //...
+config_setting(
+    name = "build_wasm",
+    constraint_values = [
+        "@platforms//os:linux",
+    ],
+    define_values = {"wasm": "true"},
+)
+
 
 load("@rules_cc//cc:defs.bzl", "cc_library")
 

CPPVARIABLES.bzl

@@ -49,6 +49,14 @@ DDS_CPPOPTS = select({
         "/WX",
         "/permissive-",
     ],
+    "//:build_wasm": [
+        "-O3",
+        "-flto",
+        "-mtune=generic",
+        "-Wpedantic",
+        "-Wall",
+        "-Werror",
+    ],
     "//conditions:default": [
         "-std=c++20"
     ],
@@ -62,6 +70,7 @@ DDS_LOCAL_DEFINES = select({
     "//:debug_build_macos": [],
     "//:build_linux": [],
     "//:debug_build_linux": [],
+    "//:build_wasm": ["__WASM__"],
     "//conditions:default": [],
 }) + select({
     "//:debug_all": ["DDS_DEBUG_ALL"],

docs/wasm_build.md

@@ -0,0 +1,180 @@
+# WebAssembly (WASM) Build Guide
+
+This document explains how to build the DDS library and examples for WebAssembly using Bazel.
+
+## Prerequisites
+
+### 1. Emscripten SDK
+
+You must have the Emscripten SDK installed and configured. Follow the official installation guide:
+https://emscripten.org/docs/getting_started/downloads.html
+
+After installation, ensure `em++` is available on your PATH:
+
+```bash
+which em++
+```
+
+### 2. Bazel
+
+Bazel 7.x or later is required. Install using your package manager or download from:
+https://bazel.build/install
+
+## Building WASM Examples
+
+### Build All Examples
+
+```bash
+cd /workspaces/dds
+bazel build --config=wasm //examples:all
+```
+
+### Build Specific Example
+
+```bash
+bazel build --config=wasm //examples:solve_board
+```
+
+### Output Files
+
+When building with `--config=wasm`, the output files will be located in:
+```
+bazel-bin/examples/
+```
+
+Depending on the target, you'll get:
+- `target.js` - JavaScript bindings
+- `target.wasm` - WebAssembly binary
+- `target.html` - HTML shell (for some targets like `solve_board`)
+
+## Available WASM Targets
+
+The following example targets are available for WASM builds:
+
+### Core Examples
+- `solve_board` - Solves a single board (produces .html)
+- `solve_board_pbn` - Solves a board from PBN notation (produces .html)
+- `solve_all_boards` - Solves multiple boards (produces .html)
+- `dds` - Main DDS example (produces .html)
+
+### Analysis Examples
+- `analyse_play_bin` - Analyze play from binary format
+- `analyse_play_pbn` - Analyze play from PBN format
+- `analyse_all_plays_bin` - Analyze all plays from binary format
+- `analyse_all_plays_pbn` - Analyze all plays from PBN format
+
+### Calculation Examples
+- `calc_dd_table` - Calculate double dummy table
+- `calc_dd_table_pbn` - Calculate DD table from PBN
+- `calc_all_tables` - Calculate all tables
+- `calc_all_tables_pbn` - Calculate all tables from PBN
+- `dealer_par` - Calculate dealer par scores
+- `par` - Calculate par scores
+- `calc_par_context_example` - Par context example
+
+## WASM Build Configuration
+
+The WASM build is configured through:
+
+1. **BUILD.bazel** - Defines the WASM config_setting:
+   ```
+   config_setting(
+       name = "build_wasm",
+       constraint_values = ["@platforms//os:emscripten"],
+   )
+   ```
+
+2. **CPPVARIABLES.bzl** - Specifies WASM-specific compiler flags:
+   - Optimization: `-O3 -flto -mtune=generic`
+   - Define: `-D__WASM__`
+
+3. **.bazelrc** - Contains the `wasm` profile:
+   ```
+   build:wasm --compiler=emscripten
+   build:wasm --cpu=wasm
+   build:wasm --cxxopt=-std=c++20
+   ```
+
+## Running WASM Examples
+
+After building, you can run the examples:
+
+### Node.js (requires Node.js installed)
+
+```bash
+node bazel-bin/examples/solve_board.js
+```
+
+### Web Browser
+
+For HTML targets, open the generated HTML file in a web browser:
+```bash
+# Copy the output files to a web-accessible location
+cp bazel-bin/examples/solve_board.* /path/to/webserver/
+
+# Then open in browser at http://localhost:8000/solve_board.html
+```
+
+## Troubleshooting
+
+### Issue: `em++` not found
+
+**Solution:** Ensure Emscripten SDK is installed and sourced:
+```bash
+source /path/to/emsdk/emsdk_env.sh
+```
+
+### Issue: Build fails with undefined reference errors
+
+**Solution:** This may indicate:
+1. Missing dependencies in the `deps` field of BUILD.bazel targets
+2. Emscripten-specific link flags needed
+
+### Issue: WASM binary is too large
+
+**Solution:** Try building with aggressive optimization:
+```bash
+bazel build --config=wasm -c opt //examples:solve_board
+```
+
+Use `--define=opt_level=3` for maximum optimization if available.
+
+## Compilation Flags
+
+The WASM build uses the following key flags:
+
+| Flag | Purpose |
+|------|---------|
+| `-O3` | Aggressive optimization |
+| `-flto` | Link-time optimization |
+| `-mtune=generic` | Generic CPU tuning |
+| `-D__WASM__` | Defines `__WASM__` preprocessor constant |
+| `-sWASM=1` | Emscripten WASM output (link flag) |
+
+## C++ Standard
+
+The WASM build uses C++20 as specified in `.bazelrc`:
+```
+build:wasm --cxxopt=-std=c++20
+```
+
+## Related Documentation
+
+- [Emscripten Documentation](https://emscripten.org/docs/)
+- [Bazel Build System](https://bazel.build/docs)
+- [DDS C++ API](c++_interface.md)
+- [Build System Overview](BUILD_SYSTEM.md)
+
+## Next Steps
+
+To integrate WASM builds into CI/CD:
+1. See `.github/workflows/ci_linux.yml` and `.github/workflows/ci_macos.yml`
+2. Add a WASM build job with `--config=wasm` and `em++` available
+3. Store WASM artifacts for download/release
+
+## Development Notes
+
+- The `__WASM__` preprocessor constant is automatically defined for WASM builds
+- Some threading and platform-specific features are disabled for WASM
+- The build produces both `.js` and `.wasm` files
+- For HTML targets, em++ produces `.html`, `.js`, and `.wasm` files together