//! builds the engine archives and generates FFI bindings for femm-sys.

use std::env;
use std::path::PathBuf;
use std::process::Command;

fn main() {
    let manifest = PathBuf::from(env::var("CARGO_MANIFEST_DIR").unwrap());
    let repo_root = manifest.parent().unwrap().parent().unwrap().to_path_buf();
    let ffi_dir = repo_root.join("ffi");
    let build_dir = repo_root.join("build").join("ffi");

    // re-run on changes to any FFI header, build script, or solver source dir.
    println!("cargo:rerun-if-changed={}", ffi_dir.display());
    println!("cargo:rerun-if-changed={}", repo_root.join("scripts/macos/build_ffi.sh").display());
    println!("cargo:rerun-if-changed={}", repo_root.join("scripts/windows/build_ffi.ps1").display());
    println!("cargo:rerun-if-changed={}", repo_root.join("scripts/windows/_toolchain.ps1").display());
    for engine in ["fkn", "belasolv", "csolv", "hsolv", "liblua", "compat"] {
        println!("cargo:rerun-if-changed={}", repo_root.join(engine).display());
    }

    let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
    let target_env = env::var("CARGO_CFG_TARGET_ENV").unwrap_or_default();
    let status = match target_os.as_str() {
        "macos" => Command::new("bash")
            .arg(repo_root.join("scripts/macos/build_ffi.sh"))
            .status()
            .expect("failed to invoke bash for engine build script"),
        "windows" => {
            let script = repo_root.join("scripts/windows/build_ffi.ps1");
            Command::new("pwsh")
                .args([
                    "-NoProfile",
                    "-ExecutionPolicy",
                    "Bypass",
                    "-File",
                ])
                .arg(&script)
                .status()
                .expect("failed to invoke pwsh for engine build script")
        }
        other => panic!("femm-sys: no engine build script wired up for target_os={other}"),
    };
    if !status.success() {
        panic!("engine build script exited with {status}");
    }

    println!("cargo:rustc-link-search=native={}", build_dir.display());
    for lib in ["femm_mag", "femm_elec", "femm_heat", "femm_curr"] {
        println!("cargo:rustc-link-lib=static={lib}");
    }
    match (target_os.as_str(), target_env.as_str()) {
        ("macos", _) => println!("cargo:rustc-link-lib=dylib=c++"),
        ("windows", "gnu") => println!("cargo:rustc-link-lib=dylib=stdc++"),
        ("windows", "gnullvm") => println!("cargo:rustc-link-lib=dylib=c++"),
        ("windows", "msvc") => { /* MSVC links the C++ runtime automatically */ }
        _ => println!("cargo:rustc-link-lib=dylib=stdc++"),
    }

    let bindings = bindgen::Builder::default()
        .header(manifest.join("wrapper.h").to_str().unwrap())
        .clang_arg(format!("-I{}", ffi_dir.display()))
        .allowlist_function("femm_.*")
        .allowlist_type("Femm.*")
        .allowlist_var("FEMM_.*")
        .derive_default(true)
        .derive_copy(true)
        .derive_debug(true)
        .layout_tests(false)
        .generate()
        .expect("bindgen failed to generate FFI bindings");

    let out = PathBuf::from(env::var("OUT_DIR").unwrap()).join("bindings.rs");
    bindings.write_to_file(&out).expect("failed to write bindings.rs");
}