bunshin/build.rs

//! Builds the microReticulum carrier shim when the `rns` feature is on.
//!
//! The library source is not vendored into this repository: the environment
//! must point at a checkout via MICRORETICULUM_SOURCE_DIR (the Nix flake and
//! the dev shell both set it). The source tree is copied into OUT_DIR and
//! patched there — a one-line `<cstdint>` include the upstream master needs
//! under current libstdc++/libc++ — because the input may be read-only and
//! both build paths should compile identical sources.

#[cfg(feature = "rns")]
fn main() {
    println!("cargo:rerun-if-changed=shim/smolmail_rns.cpp");
    println!("cargo:rerun-if-changed=shim/udp_interface.cpp");
    println!("cargo:rerun-if-env-changed=MICRORETICULUM_SOURCE_DIR");
    for dep in DEP_VARS {
        println!("cargo:rerun-if-env-changed={dep}");
    }

    let out_dir = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
    let source = std::env::var("MICRORETICULUM_SOURCE_DIR")
        .expect("the rns feature requires MICRORETICULUM_SOURCE_DIR (a microReticulum checkout)");

    // Copy the parts cmake needs: the root CMakeLists.txt and src/.
    let copy = out_dir.join("microReticulum");
    copy_tree(
        std::path::Path::new(&source),
        &copy,
        &["CMakeLists.txt", "src", "LICENSE"],
    );

    // Upstream master (2026-07-20) relies on transitive <cstdint> includes
    // that libstdc++ 15 dropped; add the include itself.
    let memory_h = copy.join("src/microReticulum/Utilities/Memory.h");
    let text = std::fs::read_to_string(&memory_h).expect("Memory.h readable");
    if !text.contains("#include <cstdint>") {
        let patched = text.replacen(
            "#include <memory>",
            "#include <memory>\n#include <cstdint>",
            1,
        );
        std::fs::write(&memory_h, patched).expect("Memory.h writable");
    }

    // Configure + build the library. Dependency overrides (RNS_*_SOURCE_DIR)
    // are passed straight through so a sandboxed build never fetches.
    let build = out_dir.join("rns-build");
    let mut configure = std::process::Command::new("cmake");
    configure
        .arg("-S")
        .arg(&copy)
        .arg("-B")
        .arg(&build)
        .arg("-DCMAKE_BUILD_TYPE=Release")
        // The NixOS gcc wrapper injects -Werror=format-security, which
        // errors once the project's -Wno-format disables -Wformat.
        .arg("-DCMAKE_C_FLAGS=-Wno-error=format-security")
        .arg("-DCMAKE_CXX_FLAGS=-Wno-error=format-security")
        .arg("-DRNS_BUILD_TESTS=OFF")
        .arg("-DRNS_BUILD_EXAMPLES=OFF")
        .arg("-DRNS_BUILD_INTEROP=OFF")
        .arg("-DRNS_USE_FS=ON")
        .arg("-DRNS_PERSIST_PATHS=OFF")
        .arg("-DRNS_PERSIST_KNOWN_DESTINATIONS=OFF")
        .arg("-DRNS_PERSIST_HASHLIST=OFF");
    for dep in DEP_VARS {
        if let Ok(path) = std::env::var(dep) {
            configure.arg(format!("-D{dep}={path}"));
        }
    }
    let status = configure.status().expect("cmake configure");
    assert!(status.success(), "cmake configure failed");
    let status = std::process::Command::new("cmake")
        .arg("--build")
        .arg(&build)
        .arg("--target")
        .arg("microReticulum")
        .status()
        .expect("cmake build");
    assert!(status.success(), "cmake build failed");

    // The same include roots and defines the library's CMake target exports
    // publicly, mirrored so the shim TU sees identical macros (the upstream
    // CMakeLists warns about ODR divergence otherwise). A vendored dep (env
    // override) lives at its checkout root; a fetched one under _deps.
    let deps = build.join("_deps");
    let mut includes: Vec<std::path::PathBuf> = vec![copy.join("src")];
    for (env_var, fetch_name, sub) in DEP_INCLUDES {
        includes.push(match std::env::var(env_var) {
            Ok(root) => std::path::Path::new(&root).join(sub),
            Err(_) => deps.join(format!("{fetch_name}-src")).join(sub),
        });
    }

    let mut build_cc = cc::Build::new();
    build_cc
        .cpp(true)
        .std("c++17")
        .define("NATIVE", None)
        .define("USTORE_USE_UNIVERSALFS", None)
        .define("RNS_USE_FS", None)
        .file("shim/smolmail_rns.cpp")
        .file("shim/udp_interface.cpp");
    for include in &includes {
        build_cc.include(include);
    }
    build_cc.compile("smolmail_rns_shim");

    println!("cargo:rustc-link-search=native={}", build.display());
    println!("cargo:rustc-link-lib=static=microReticulum");
    println!("cargo:rustc-link-lib=static=CryptoLib");
}

// microReticulum's own local-checkout override variables.
#[cfg(feature = "rns")]
const DEP_VARS: &[&str] = &[
    "RNS_ARDUINOJSON_SOURCE_DIR",
    "RNS_MSGPACK_SOURCE_DIR",
    "RNS_CRYPTO_SOURCE_DIR",
    "RNS_MICROSTORE_SOURCE_DIR",
    "RNS_ARXCONTAINER_SOURCE_DIR",
    "RNS_ARXTYPETRAITS_SOURCE_DIR",
    "RNS_DEBUGLOG_SOURCE_DIR",
];

// (override env var, FetchContent name, include subdir within the dep root).
#[cfg(feature = "rns")]
const DEP_INCLUDES: &[(&str, &str, &str)] = &[
    ("RNS_ARDUINOJSON_SOURCE_DIR", "arduinojson", "src"),
    ("RNS_MSGPACK_SOURCE_DIR", "msgpack", ""),
    ("RNS_ARXCONTAINER_SOURCE_DIR", "arxcontainer", ""),
    ("RNS_ARXTYPETRAITS_SOURCE_DIR", "arxtypetraits", ""),
    ("RNS_DEBUGLOG_SOURCE_DIR", "debuglog", ""),
    ("RNS_CRYPTO_SOURCE_DIR", "crypto", ""),
    ("RNS_MICROSTORE_SOURCE_DIR", "microstore", "include"),
];

#[cfg(feature = "rns")]
fn copy_tree(src: &std::path::Path, dst: &std::path::Path, entries: &[&str]) {
    std::fs::create_dir_all(dst).expect("OUT_DIR writable");
    for entry in entries {
        let from = src.join(entry);
        if !from.exists() {
            continue;
        }
        let to = dst.join(entry);
        if from.is_dir() {
            copy_dir(&from, &to);
        } else {
            copy_file(&from, &to);
        }
    }
}

#[cfg(feature = "rns")]
fn copy_dir(src: &std::path::Path, dst: &std::path::Path) {
    std::fs::create_dir_all(dst).expect("OUT_DIR writable");
    for entry in std::fs::read_dir(src).expect("readable source dir") {
        let entry = entry.expect("readable source dir").path();
        let to = dst.join(entry.file_name().unwrap());
        if entry.is_dir() {
            copy_dir(&entry, &to);
        } else {
            copy_file(&entry, &to);
        }
    }
}

/// fs::copy preserves the source's mode, and a Nix store checkout is
/// read-only, so the copy must be made writable before the patch step.
#[cfg(feature = "rns")]
fn copy_file(from: &std::path::Path, to: &std::path::Path) {
    std::fs::copy(from, to).expect("copy file");
    #[cfg(unix)]
    {
        use std::os::unix::fs::PermissionsExt;
        std::fs::set_permissions(to, std::fs::Permissions::from_mode(0o644))
            .expect("copied file writable");
    }
}

#[cfg(not(feature = "rns"))]
fn main() {}