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

const PDFIUM_VERSION: &str = "chromium%2F7725";

fn pdfium_url(os: &str, arch: &str) -> String {
	let platform = match (os, arch) {
		("linux", "x86_64") => "linux-x64",
		("linux", "aarch64") => "linux-arm64",
		("macos", "x86_64") => "mac-x64",
		("macos", "aarch64") => "mac-arm64",
		_ => panic!("unsupported platform: {os}-{arch}"),
	};
	format!(
		"https://github.com/bblanchon/pdfium-binaries/releases/download/{PDFIUM_VERSION}/pdfium-{platform}.tgz"
	)
}

fn lib_name(os: &str) -> &'static str {
	match os {
		"macos" => "libpdfium.dylib",
		_ => "libpdfium.so",
	}
}

fn rpath_flag(os: &str) -> &'static str {
	match os {
		"macos" => "-Wl,-rpath,@loader_path",
		_ => "-Wl,-rpath,$ORIGIN",
	}
}

#[expect(clippy::expect_used)]
#[expect(clippy::unwrap_used)]
#[expect(clippy::print_stderr)]
fn main() {
	println!("cargo:rerun-if-changed=build.rs");

	if env::var("CARGO_FEATURE_PDFIUM").is_err() {
		return;
	}

	let os = env::var("CARGO_CFG_TARGET_OS").unwrap();
	let arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();

	let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());

	// OUT_DIR is target/<profile>/build/<pkg>-<hash>/out
	// Go up 3 levels to reach target/<profile>/
	let profile_dir = out_dir
		.ancestors()
		.nth(3)
		.expect("unexpected OUT_DIR structure")
		.to_path_buf();

	// If PDFIUM_LIB_DIR is set (e.g. by Nix), use the pre-installed library directly.
	if let Ok(lib_dir) = env::var("PDFIUM_LIB_DIR") {
		println!("cargo:rustc-link-search=native={lib_dir}");
		println!("cargo:rustc-link-lib=dylib=pdfium");
		return;
	}

	let lib_file = lib_name(&os);
	let lib_path = profile_dir.join(lib_file);

	if !lib_path.exists() {
		let url = pdfium_url(&os, &arch);
		let tgz_path = out_dir.join("pdfium.tgz");

		eprintln!("cargo:warning=Downloading PDFium from {url}");

		let status = std::process::Command::new("curl")
			.args(["-L", "--fail", "-o", tgz_path.to_str().unwrap(), &url])
			.status()
			.expect("failed to run curl");
		assert!(status.success(), "curl failed to download PDFium");

		let status = std::process::Command::new("tar")
			.args([
				"-xzf",
				tgz_path.to_str().unwrap(),
				"-C",
				out_dir.to_str().unwrap(),
			])
			.status()
			.expect("failed to run tar");
		assert!(status.success(), "tar failed to extract PDFium");

		std::fs::copy(out_dir.join("lib").join(lib_file), &lib_path)
			.expect("failed to copy pdfium library");
	}

	println!("cargo:rustc-link-search=native={}", profile_dir.display());
	println!("cargo:rustc-link-lib=dylib=pdfium");
	println!("cargo:rustc-link-arg={}", rpath_flag(&os));
}