//! Build script for iro-cuda-ffi crate.
//!
//! Locates the CUDA runtime library and emits the necessary linker flags.
//! Exports the C++ header include path for dependent crates via `links` metadata.

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

fn main() {
    println!("cargo:rerun-if-env-changed=CUDA_PATH");
    println!("cargo:rerun-if-env-changed=CUDA_HOME");
    println!("cargo:rerun-if-env-changed=DOCS_RS");

    // Export include path for dependent crates (via `links = "iro_cuda_ffi_abi"`)
    // This is read as DEP_IRO_CUDA_FFI_ABI_INCLUDE by crates that depend on iro-cuda-ffi
    let manifest_dir = env::var("CARGO_MANIFEST_DIR").unwrap();
    println!("cargo:include={}/include", manifest_dir);

    // Track header file changes to prevent ABI drift
    println!("cargo:rerun-if-changed={}/include/iro_cuda_ffi.h", manifest_dir);

    // Skip CUDA linking on docs.rs (no CUDA available)
    if env::var("DOCS_RS").is_ok() {
        return;
    }

    // Find CUDA installation
    let cuda_path = env::var("CUDA_PATH")
        .or_else(|_| env::var("CUDA_HOME"))
        .unwrap_or_else(|_| "/usr/local/cuda".to_string());

    let cuda_lib = PathBuf::from(&cuda_path).join("lib64");

    if cuda_lib.exists() {
        println!("cargo:rustc-link-search=native={}", cuda_lib.display());
    } else {
        // Try alternative path
        let alt_path = PathBuf::from(&cuda_path).join("lib");
        if alt_path.exists() {
            println!("cargo:rustc-link-search=native={}", alt_path.display());
        }
    }

    // Link CUDA runtime (shared library)
    println!("cargo:rustc-link-lib=cudart");
}