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


fn query_llvm_config(arg: &str) -> String {
    let llvm_config_cmd = env::var("LLVM_CONFIG_PATH").unwrap_or("llvm-config".to_string());
    let cmd_out = process::Command::new(llvm_config_cmd).arg(arg)
        .output()
        .expect("llvm-config must be in PATH or set LLVM_CONFIG_PATH to the llvm-config binary");
    String::from_utf8(cmd_out.stdout).expect("utf8")
        .trim_end().to_owned()
}

fn main() {
    let paths = collect_search_paths();
    let mut cfg = cc::Build::new();
    cfg
        .warnings(false)
        .cpp(true)
        .file("src/extensions.cpp")
        .include(&paths[0])
        .include(find_clang_include(&paths, "clang/AST/OperationKinds.h"))
        .include(find_clang_include(&paths, "llvm/Support/DataTypes.h"))
        .include(find_clang_include(&paths, "clang/AST/StmtNodes.inc"))
        .include(dunce::canonicalize("vendor").unwrap());
    if !env::var("TARGET").unwrap().contains("msvc") {
        cfg.flag("-std=c++11").flag("-Wno-comment");
    }
    cfg.compile("libc3_clang_extensions.a");
}

fn collect_search_paths() -> Vec<PathBuf> {
    let inc_path = PathBuf::from(query_llvm_config("--includedir"));
    let lib_inc_path = PathBuf::from(format!("{}/../include", query_llvm_config("--libdir")));
    let mut paths = vec![inc_path, lib_inc_path];

    if let Ok(user_paths) = env::var("LIBCLANG_INCLUDE_PATH") {
        paths.extend(env::split_paths(&user_paths));
    }

    paths
}

fn find_clang_include(std_search_paths: &[PathBuf], file_search: &str) -> PathBuf {
    let fallback_paths = [
        "/usr/lib/llvm-5.0/include/",
        "/usr/lib/llvm-4.0/include/",
        "C:\\Program Files\\LLVM\\include",
        "../clang/include/",
        "../../clang/include/",
        "../../../clang/include/",
        "../llvm/include/",
        "../../llvm/include/",
        "../../../llvm/include/",
    ];
    let candidate_paths = std_search_paths.iter()
        .map(|p|p.as_path())
        .chain(fallback_paths.iter().map(Path::new));

    for fspath in candidate_paths {
        if fspath.exists() && fspath.join(file_search).exists() {
            return dunce::canonicalize(fspath).unwrap();
        }
        if let Some(parent) = fspath.parent() {
            if parent.join(file_search).exists() {
                return dunce::canonicalize(parent).unwrap();
            }
        }
    }

    let searched = std_search_paths.iter().map(|p|p.to_string_lossy()).collect::<Vec<_>>().join(", ");
    println!("cargo:warning=Unable to find include path for '{file_search}'. Add dirs to LIBCLANG_INCLUDE_PATH");
    println!("cargo:warning=Searched {searched:?}");
    PathBuf::from("./clang/include/")
}