dev/bazel/rust_toolchain.bzl

def _required_path(repository_ctx, command):
    path = repository_ctx.which(command)
    if path == None:
        fail("{} must be available in PATH. Enter the rust dev shell first.".format(command))
    return path


def _execute(repository_ctx, arguments):
    result = repository_ctx.execute(arguments)
    if result.return_code != 0:
        fail("command failed: {}\n{}".format(" ".join(arguments), result.stderr))
    return result.stdout.strip()


def _rust_repository_impl(repository_ctx):
    rustc = _required_path(repository_ctx, "rustc")
    rustdoc = _required_path(repository_ctx, "rustdoc")
    cargo = _required_path(repository_ctx, "cargo")
    cargo_clippy = _required_path(repository_ctx, "cargo-clippy")
    clippy_driver = _required_path(repository_ctx, "clippy-driver")
    rustfmt = _required_path(repository_ctx, "rustfmt")
    cc = _required_path(repository_ctx, "cc")

    sysroot = _execute(repository_ctx, [str(rustc), "--print", "sysroot"])
    verbose_version = _execute(repository_ctx, [str(rustc), "-vV"])

    host_triple = None
    release = None
    for line in verbose_version.splitlines():
        if line.startswith("host: "):
            host_triple = line.removeprefix("host: ")
        if line.startswith("release: "):
            release = line.removeprefix("release: ")

    if host_triple == None:
        fail("rustc -vV did not report a host triple")
    if release == None:
        fail("rustc -vV did not report a release")

    repository_ctx.symlink(rustc, "bin/rustc")
    repository_ctx.symlink(rustdoc, "bin/rustdoc")
    repository_ctx.symlink(cargo, "bin/cargo")
    repository_ctx.symlink(cargo_clippy, "bin/cargo-clippy")
    repository_ctx.symlink(clippy_driver, "bin/clippy-driver")
    repository_ctx.symlink(rustfmt, "bin/rustfmt")
    repository_ctx.symlink(cc, "bin/cc")
    repository_ctx.symlink(sysroot, "rust")

    repository_ctx.file("WORKSPACE.bazel", "")
    repository_ctx.file("BUILD.bazel", _build_file(host_triple, release))


def _build_file(host_triple, release):
    return """
filegroup(
    name = "rustc",
    srcs = ["bin/rustc"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "rustdoc",
    srcs = ["bin/rustdoc"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "cargo",
    srcs = ["bin/cargo"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "cargo_clippy",
    srcs = ["bin/cargo-clippy"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "clippy_driver",
    srcs = ["bin/clippy-driver"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "rustfmt",
    srcs = ["bin/rustfmt"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "cc",
    srcs = ["bin/cc"],
    visibility = ["//visibility:public"],
)

filegroup(
    name = "rustc_lib",
    srcs = glob(
        [
            "rust/lib/*.so*",
            "rust/lib/rustlib/{host_triple}/codegen-backends/*.so",
            "rust/lib/rustlib/{host_triple}/lib/*.so*",
            "rust/lib/rustlib/{host_triple}/lib/*.rmeta",
        ],
        allow_empty = True,
    ),
    visibility = ["//visibility:public"],
)

filegroup(
    name = "rust_objcopy",
    srcs = glob(
        ["rust/lib/rustlib/{host_triple}/bin/rust-objcopy"],
        allow_empty = True,
    ),
    visibility = ["//visibility:public"],
)

load("@rules_rust//rust:toolchain.bzl", "rust_stdlib_filegroup")

rust_stdlib_filegroup(
    name = "rust_std",
    srcs = glob(
        [
            "rust/lib/rustlib/{host_triple}/lib/*.rlib",
            "rust/lib/rustlib/{host_triple}/lib/*.rmeta",
            "rust/lib/rustlib/{host_triple}/lib/*.so*",
            "rust/lib/rustlib/{host_triple}/lib/*.a",
            "rust/lib/rustlib/{host_triple}/lib/self-contained/**",
        ],
        allow_empty = True,
    ),
    visibility = ["//visibility:public"],
)

load("@rules_rust//rust:toolchain.bzl", "rust_toolchain")

rust_toolchain(
    name = "rust_toolchain_impl",
    rust_doc = ":rustdoc",
    rust_std = ":rust_std",
    rustc = ":rustc",
    linker = ":cc",
    linker_type = "indirect",
    rust_objcopy = ":rust_objcopy",
    rustfmt = ":rustfmt",
    cargo = ":cargo",
    clippy_driver = ":clippy_driver",
    cargo_clippy = ":cargo_clippy",
    rustc_lib = ":rustc_lib",
    allocator_library = None,
    global_allocator_library = None,
    binary_ext = "",
    staticlib_ext = ".a",
    dylib_ext = ".so",
    stdlib_linkflags = ["-ldl", "-lpthread"],
    default_edition = "2024",
    exec_triple = "{host_triple}",
    target_triple = "{host_triple}",
    version = "{release}",
    channel = "stable",
    visibility = ["//visibility:public"],
)

toolchain(
    name = "rust_toolchain",
    toolchain = ":rust_toolchain_impl",
    toolchain_type = "@rules_rust//rust:toolchain_type",
    visibility = ["//visibility:public"],
)
""".format(
        host_triple = host_triple,
        release = release,
    )


rust_repository = repository_rule(
    implementation = _rust_repository_impl,
    local = True,
    environ = ["PATH"],
)


def _rust_impl(module_ctx):
    rust_repository(name = "rust_toolchain")


rust = module_extension(
    implementation = _rust_impl,
)