#2786 botan: add script to build botan3 amalgamation

Signed-off-by: Patrizio Bekerle <patrizio@bekerle.com>

justfile

@@ -202,3 +202,8 @@ format args='':
 [group('linter')]
 run-github-workflow args='format-check':
     nix-shell -p act --run "act -j {{ args }}"
+
+# Build botan3 amalgamation
+[group('maintenance')]
+build-botan3-amalgamation:
+    nix-build -E 'with import <nixpkgs> {}; callPackage ./scripts/botan3-amalgamation.nix {}'

scripts/botan3-amalgamation.nix

@@ -0,0 +1,174 @@
+{
+  lib,
+  stdenv,
+  fetchurl,
+  python3,
+  which,
+}:
+
+stdenv.mkDerivation rec {
+  pname = "botan3-amalgamation";
+  version = "3.8.1";
+
+  src = fetchurl {
+    url = "https://botan.randombit.net/releases/Botan-${version}.tar.xz";
+    hash = "sha256-sDloHUuGGi9YU3Rti6gG9VPiOGntctie2/o8Pb+hfmg=";
+  };
+
+  nativeBuildInputs = [
+    python3
+    which
+  ];
+
+  # Configure to build amalgamation
+  configurePhase = ''
+    runHook preConfigure
+
+    # Configure Botan to generate amalgamation files
+    # We only need the amalgamation, so we can use --no-install-python-module
+    # and other minimal flags to avoid building the full library
+    python3 configure.py \
+      --amalgamation \
+      --no-install-python-module \
+      --prefix=$out
+
+    runHook postConfigure
+  '';
+
+  # Build phase - we only need the amalgamation generation, not the full build
+  buildPhase = ''
+    runHook preBuild
+
+    # The amalgamation files are generated during configure
+    # We just need to make sure they exist
+    if [ ! -f botan_all.cpp ] || [ ! -f botan_all.h ]; then
+      echo "Error: Amalgamation files were not generated"
+      exit 1
+    fi
+
+    ls -hal
+
+    runHook postBuild
+  '';
+
+  # Install the amalgamation files
+  installPhase = ''
+        runHook preInstall
+
+        mkdir -p $out/include
+        mkdir -p $out/src
+
+        # Copy the amalgamation header and source
+        cp botan_all.h $out/include/
+        cp botan_all.cpp $out/src/
+
+        echo "Amalgamation files installed:"
+        echo "  Header: $out/include/botan_all.h"
+        echo "  Source: $out/src/botan_all.cpp"
+
+        # Create a simple usage example
+        cat > $out/README.md << EOF
+    # Botan ${version} Amalgamation
+
+    This package provides the Botan ${version} cryptography library as amalgamation files:
+
+    - \`include/botan_all.h\` - Single header file containing all Botan headers
+    - \`src/botan_all.cpp\` - Single source file containing all Botan implementation
+
+    ## Usage
+
+    To use in your C++ project:
+
+    1. Include the header: \`#include "botan_all.h"\`
+    2. Compile with the source: \`g++ -std=c++20 your_code.cpp botan_all.cpp\`
+
+    ## Example
+
+    \`\`\`cpp
+    #include "botan_all.h"
+    #include <iostream>
+
+    int main() {
+        // Initialize Botan
+        Botan::LibraryInitializer init;
+
+        // Use Botan functionality
+        auto rng = std::make_unique<Botan::AutoSeeded_RNG>();
+        auto random_data = rng->random_vec(32);
+
+        std::cout << "Generated " << random_data.size() << " random bytes" << std::endl;
+        return 0;
+    }
+    \`\`\`
+
+    ## Version Information
+
+    - Botan Version: ${version}
+    - Generated: $(date)
+    - Configuration: Amalgamation build
+    EOF
+
+        runHook postInstall
+  '';
+
+  # Verify the amalgamation files are valid
+  doCheck = true;
+  checkPhase = ''
+    runHook preCheck
+
+    echo "Checking amalgamation files..."
+
+    if [ ! -f botan_all.h ]; then
+      echo "ERROR: botan_all.h not found"
+      exit 1
+    fi
+
+    if [ ! -f botan_all.cpp ]; then
+      echo "ERROR: botan_all.cpp not found"
+      exit 1
+    fi
+
+    header_size=$(stat -c%s botan_all.h)
+    source_size=$(stat -c%s botan_all.cpp)
+
+    if [ $header_size -lt 100000 ]; then
+      echo "WARNING: Header file seems too small ($header_size bytes)"
+    fi
+
+    if [ $source_size -lt 1000000 ]; then
+      echo "WARNING: Source file seems too small ($source_size bytes)"
+    fi
+
+    if ! grep -q "namespace Botan" botan_all.h; then
+      echo "ERROR: Botan namespace not found in header"
+      exit 1
+    fi
+
+    echo "Amalgamation files validation passed"
+    echo "Header size: $header_size bytes"
+    echo "Source size: $source_size bytes"
+
+    runHook postCheck
+  '';
+
+  meta = with lib; {
+    description = "Botan ${version} cryptography library amalgamation files";
+    longDescription = ''
+      This package provides Botan ${version} as amalgamation files - a single
+      header (botan_all.h) and source file (botan_all.cpp) that contain the
+      entire Botan cryptography library. This makes it easy to integrate Botan
+      into projects without dealing with complex build dependencies.
+
+      Botan is a C++ cryptography library providing TLS, X.509, ECDSA, AES,
+      RSA, and many other cryptographic algorithms and protocols.
+    '';
+    homepage = "https://botan.randombit.net/";
+    changelog = "https://botan.randombit.net/news.html";
+    license = licenses.bsd2;
+    maintainers = [ pbek ];
+    platforms = platforms.all;
+
+    # This is a source-only package
+    hydraPlatforms = [ ];
+  };
+}