matrix-rust-sdk

use std::{

    env,

    error::Error,

    path::{Path, PathBuf},

    process::Command,

};

use vergen_gitcl::{Emitter, GitclBuilder};

/// Adds a temporary workaround for an issue with the Rust compiler and Android

/// in x86_64 devices: https://github.com/rust-lang/rust/issues/109717.

/// The workaround is based on: https://github.com/mozilla/application-services/pull/5442

///

/// TODO: I think this is obsolete with cargo-ndk 4.0.0:

/// https://github.com/bbqsrc/cargo-ndk/commit/03c738653f935416580803b82fc6ad72c10dbebc

///

/// IMPORTANT: if you modify this, make sure to modify

/// [../matrix-sdk-ffi/build.rs] too!

fn setup_x86_64_android_workaround() {

    let target_os = env::var("CARGO_CFG_TARGET_OS").expect("CARGO_CFG_TARGET_OS not set");

    let target_arch = env::var("CARGO_CFG_TARGET_ARCH").expect("CARGO_CFG_TARGET_ARCH not set");

    if target_arch == "x86_64" && target_os == "android" {

        // Configure rust to statically link against the `libclang_rt.builtins` supplied

        // with clang.

        // cargo-ndk sets CC_x86_64-linux-android to the path to `clang`, within the

        // Android NDK.

        let clang_path = PathBuf::from(

            env::var("CC_x86_64-linux-android").expect("CC_x86_64-linux-android not set"),

        );

        // clang_path should now look something like

        // `.../sdk/ndk/28.0.12674087/toolchains/llvm/prebuilt/linux-x86_64/bin/clang`.

        // We strip `/bin/clang` from the end to get the toolchain path.

        let toolchain_path = clang_path

            .ancestors()

            .nth(2)

            .expect("could not find NDK toolchain path")

            .to_str()

            .expect("NDK toolchain path is not valid UTF-8");

        let clang_version = get_clang_major_version(&clang_path);

        println!("cargo:rustc-link-search={toolchain_path}/lib/clang/{clang_version}/lib/linux/");

        println!("cargo:rustc-link-lib=static=clang_rt.builtins-x86_64-android");

        // Ensure we re-run this build script if the location of the toolchain changes.

        println!("cargo:rerun-if-env-changed=CC_x86_64-linux-android");

    }

}

/// Run the clang binary at `clang_path`, and return its major version number

fn get_clang_major_version(clang_path: &Path) -> String {

    let clang_output =

        Command::new(clang_path).arg("-dumpversion").output().expect("failed to start clang");

    if !clang_output.status.success() {

        panic!("failed to run clang: {}", String::from_utf8_lossy(&clang_output.stderr));

    }

    let clang_version = String::from_utf8(clang_output.stdout).expect("clang output is not utf8");

    clang_version.split('.').next().expect("could not parse clang output").to_owned()

}

fn main() -> Result<(), Box<dyn Error>> {

    setup_x86_64_android_workaround();

    let git_config = GitclBuilder::default().sha(true).describe(true, false, None).build()?;

    Emitter::default().add_instructions(&git_config)?.emit()?;

    Ok(())

}