highs-sys 1.14.0

use std::env;
use std::path::{Path, PathBuf};

/// Used to exclude autogenerated files in the output dir from `cargo:rerun-if-changed` directives.
#[derive(Debug)]
pub struct CustomCargoCallbacks {
    exclude_dir: Option<PathBuf>,
}

impl bindgen::callbacks::ParseCallbacks for CustomCargoCallbacks {
    fn header_file(&self, filename: &str) {
        if matches!(&self.exclude_dir, Some(exclude_dir) if Path::new(filename).starts_with(exclude_dir))
        {
            return;
        }
        println!("cargo:rerun-if-changed={filename}");
    }

    fn include_file(&self, filename: &str) {
        if matches!(&self.exclude_dir, Some(exclude_dir) if Path::new(filename).starts_with(exclude_dir))
        {
            return;
        }
        println!("cargo:rerun-if-changed={filename}");
    }

    fn read_env_var(&self, key: &str) {
        println!("cargo:rerun-if-env-changed={key}");
    }
}

fn generate_bindings<'a>(
    exclude_dir: Option<PathBuf>,
    include_paths: impl IntoIterator<Item = &'a Path>,
) {
    let target = env::var("TARGET").unwrap();
    let emscripten = target.contains("emscripten");

    // The bindgen::Builder is the main entry point
    // to bindgen, and lets you build up options for
    // the resulting bindings.
    let builder = include_paths
        .into_iter()
        .fold(bindgen::Builder::default(), |builder, path| {
            builder.clang_arg(format!("-I{}", path.to_string_lossy()))
        });

    // Work around bindgen/libclang missing `Highs_*` function declarations for
    // `wasm32-unknown-emscripten` when parsing with emscripten's sysroot.
    // The C API signatures are target-independent, so parse as host and skip
    // cross-target layout assertions.
    let builder = if emscripten {
        println!("cargo:rerun-if-env-changed=HOST");
        let host = env::var("HOST")
            .expect("TARGET is emscripten but HOST is not set; needed for bindgen host parsing");
        builder
            .clang_arg(format!("--target={host}"))
            .layout_tests(false)
    } else {
        builder
    };

    let c_bindings = builder
        // The input header we would like to generate bindings for.
        // This is a trivial wrapper header so that the HiGHS headers
        // can be discovered from the include path.
        .header("wrapper.h")
        // Tell cargo to invalidate the built crate whenever any of the
        // included header files changed.
        .parse_callbacks(Box::new(CustomCargoCallbacks { exclude_dir }))
        // Finish the builder and generate the bindings.
        .generate()
        // Unwrap the Result and panic on failure.
        .expect("Unable to generate bindings");

    // Write the bindings to the $OUT_DIR/bindings.rs file.
    let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());
    c_bindings
        .write_to_file(out_path.join("c_bindings.rs"))
        .expect("Couldn't write bindings!");
}

#[cfg(feature = "build")]
fn build() -> bool {
    use cmake::Config;
    let target = env::var("TARGET").unwrap();
    let emscripten = target.contains("emscripten");
    let mut dst = Config::new("HiGHS");

    if cfg!(feature = "ninja") {
        dst.generator("Ninja");
    }

    dst.define("BUILD_CXX_EXE", "OFF");
    dst.define("BUILD_EXAMPLES", "OFF");

    // `cmake` crate default C++ flags inject `-fno-exceptions` for this target,
    // but HiGHS requires C++ exceptions. Use explicit flags for emscripten.
    if emscripten {
        dst.no_default_flags(true);
        dst.cxxflag("-fexceptions");
    }

    // Avoid using downstream project's profile setting for HiGHS build.
    if cfg!(feature = "highs_release") {
        dst.profile("Release");
    }

    let dst = dst
        .define("FAST_BUILD", "ON")
        .define("BUILD_SHARED_LIBS", "OFF")
        .define("CMAKE_MSVC_RUNTIME_LIBRARY", "MultiThreadedDLL")
        .define("CMAKE_INTERPROCEDURAL_OPTIMIZATION", "FALSE")
        .define("ZLIB", if cfg!(feature = "libz") { "ON" } else { "OFF" })
        .build();

    let include_path = dst.join("include").join("highs");
    generate_bindings(Some(dst.clone()), [include_path.as_path()]);

    println!("cargo:rustc-link-search=native={}/lib", dst.display());
    println!("cargo:rustc-link-search=native={}/lib64", dst.display());
    println!("cargo:rustc-link-lib=static=highs");

    if cfg!(feature = "libz") {
        println!("cargo:rustc-link-lib=z");
    }

    let apple = target.contains("apple");
    let linux = target.contains("linux");
    let mingw = target.contains("pc-windows-gnu");
    if apple || emscripten {
        println!("cargo:rustc-link-lib=c++");
    } else if linux || mingw {
        println!("cargo:rustc-link-lib=stdc++");
    }
    println!("cargo:rerun-if-changed=HiGHS/highs/interfaces/highs_c_api.h");

    true
}

#[cfg(not(feature = "build"))]
fn build() -> bool {
    false
}

#[cfg(feature = "discover")]
fn discover() -> bool {
    let lib = match pkg_config::Config::new()
        .atleast_version("1.5.0")
        .probe("highs")
    {
        Ok(lib) => lib,
        Err(_e) => return false,
    };

    generate_bindings(None, lib.include_paths.iter().map(|p| p.as_path()));

    true
}

#[cfg(not(feature = "discover"))]
fn discover() -> bool {
    false
}

fn main() {
    if cfg!(all(
        any(
            feature = "highs_release",
            feature = "libz",
            feature = "ninja"
        ),
        not(feature = "build")
    )) {
        panic!(
            "You have enabled features that control how HiGHS is built, but have not enabled the 'build' feature.\n\
               Thus, your features will never have any effect. Please enable the 'build' feature on highs-sys if you want to build HiGHS or disable the 'libz', 'ninja' and 'highs_release' features."
        );
    }

    if !discover() && !build() {
        panic!("Could neither discover nor build HiGHS");
    }
}