fn main() {
    // for Apple Mac M1
    // use brew to install
    // brew install boost
    // brew install open-babel
    // brew install sqlite
    //
    // export RECGEN_LIB=/opt/homebrew/lib/:/opt/homebrew/sqlite/lib
    // export RECGEN_INCL=/opt/homebrew/include:/opt/homebrew/include/openbabel3:/opt/homebrew/opt/sqlite/include 

    // for Mac OS x86_64
    // use conda to install
    // conda install -c conda-forge boost-cpp
    // conda install -c anaconda sqlite
    // conda install -c conda-forge openbabel
    // 
    // # export RECGEN_LIB=~/miniconda3/envs/openbabel/lib
    // # export RECGEN_INCL=~/miniconda3/envs/openbabel/include:~/miniconda3/envs/openbabel/include/openbabel3

    // for Ubuntu, use apt
    //      sudo apt-get install -y libboost-all-dev libsqlite3-dev libopenbabel-dev  
    //      export RECGEN_INCL=/usr/include:/usr/include/openbabel3
    //      export RECGEN_LIB=/usr/lib/x86_64-linux-gnu

    let recgen_incl_o = std::env::var_os("RECGEN_INCL");
    if recgen_incl_o.is_none() {
        println!("cargo:warning={}", "Set environment variable RECGEN_INCL for header files first");
        return;
    }
    let recgen_incl_raw = recgen_incl_o.unwrap().into_string().unwrap();
    let recgen_incls = recgen_incl_raw.split(":");

    let recgen_lib_o = std::env::var_os("RECGEN_LIB");
    if recgen_lib_o.is_none() {
        println!("cargo:warning={}", "Set environment variable RECGEN_LIB for libraries first");
        return;
    }
    let recgen_lib_raw = recgen_lib_o.unwrap().into_string().unwrap();
    let recgen_libs = recgen_lib_raw.split(":");

    cxx_build::bridge("src/lib.rs")
        .file("deps/ReCGen/src/WrapSQLite.cpp")
        .file("deps/ReCGen/src/ECMol.cpp")
        .file("deps/ReCGen/src/Overlap.cpp")
        .file("deps/ReCGen/src/Unit.cpp")
        .file("deps/ReCGen/src/Frame.cpp")
        .file("deps/ReCGen/src/BBMol.cpp")
        .file("deps/ReCGen/src/Build.cpp")
        .file("deps/ReCGen/src/SSS.cpp")
        .file("deps/ReCGen/src/Fragmentation.cpp")
        .file("deps/ReCGen/src/ECFP-build.cpp")
        .file("src/wrapper.cpp")
        .includes(recgen_incls)
        .include("deps/ReCGen/src")
        .include("src")
        .flag("-DREV=465") // required by ReCGEN
        .flag_if_supported("-std=c++14")
        .flag_if_supported("-Wno-c++11-extensions")
        .flag_if_supported("-Wno-unused-parameter")
        .flag_if_supported("-Wno-unused-variable")
        .flag_if_supported("-Wno-sign-compare")
        .flag_if_supported("-Wno-for-loop-analysis")
        .flag_if_supported("-Wno-ignored-qualifiers")
        .flag_if_supported("-Wno-return-type")
        .flag_if_supported("-Wno-deprecated-declarations")
        .warnings(false)
        .compile("recgen");

    for p in recgen_libs {
        println!("cargo:rustc-link-search=native={}", p);
    }
    println!("cargo:rustc-link-lib=dylib=openbabel");
    println!("cargo:rustc-link-lib=dylib=boost_iostreams");
    println!("cargo:rustc-link-lib=dylib=sqlite3");
    
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=src/wrapper.h");
    println!("cargo:rerun-if-changed=src/wrapper.cpp");
}