// Copyright Supranational LLC
// Licensed under the Apache License, Version 2.0, see LICENSE for details.
// SPDX-License-Identifier: Apache-2.0

use std::env;
use std::path::PathBuf;

fn main() {
    let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
    let mut base_dir = manifest_dir.join("sppark");
    if !base_dir.exists() {
        // Reach out to .., which is the root of the sppark repo.
        // Use an absolute path to avoid issues with relative paths
        // being treated as strings by `cc` and getting concatenated
        // in ways that reach out of the OUT_DIR.
        base_dir = manifest_dir
            .parent()
            .expect("can't access parent of current directory")
            .into();
        println!(
            "cargo:rerun-if-changed={}",
            base_dir.join("ec").to_string_lossy()
        );
        println!(
            "cargo:rerun-if-changed={}",
            base_dir.join("ff").to_string_lossy()
        );
        println!(
            "cargo:rerun-if-changed={}",
            base_dir.join("ntt").to_string_lossy()
        );
        println!(
            "cargo:rerun-if-changed={}",
            base_dir.join("msm").to_string_lossy()
        );
        println!(
            "cargo:rerun-if-changed={}",
            base_dir.join("util").to_string_lossy()
        );
    }
    // pass DEP_SPPARK_* variables to dependents
    println!("cargo:ROOT={}", base_dir.to_string_lossy());

    // Detect if there is CUDA compiler and engage "cuda" feature accordingly
    let nvcc = match env::var("NVCC") {
        Ok(var) => which::which(var),
        Err(_) => which::which("nvcc"),
    };
    if nvcc.is_ok() {
        let cuda_version = std::process::Command::new(nvcc.unwrap())
            .arg("--version")
            .output()
            .expect("impossible");
        if !cuda_version.status.success() {
            panic!("{:?}", cuda_version);
        }
        let cuda_version = String::from_utf8(cuda_version.stdout).unwrap();
        let x = cuda_version
            .find("release ")
            .expect("can't find \"release X.Y,\" in --version output")
            + 8;
        let y = cuda_version[x..]
            .find(",")
            .expect("can't parse \"release X.Y,\" in --version output");
        let v = cuda_version[x..x + y].parse::<f32>().unwrap();
        if v < 11.4 {
            panic!("Unsupported CUDA version {} < 11.4", v);
        }

        let util_dir = base_dir.join("util");
        let mut nvcc = cc::Build::new();
        nvcc.cuda(true);
        nvcc.include(base_dir);
        nvcc.file("src/lib.cpp")
            .file(util_dir.join("all_gpus.cpp"))
            .compile("sppark_cuda");
        println!("cargo:rerun-if-changed=src/lib.cpp");
        println!("cargo:rustc-cfg=feature=\"cuda\"");
    }
    println!("cargo:rerun-if-env-changed=NVCC");
}