load("@prelude//rust:rust_toolchain.bzl", "PanicRuntime", "RustToolchainInfo")

_DEFAULT_TRIPLE = select({
    "prelude//os:linux": select({
        "prelude//cpu:arm64": "aarch64-unknown-linux-gnu",
        "prelude//cpu:riscv64": "riscv64gc-unknown-linux-gnu",
        "prelude//cpu:x86_64": "x86_64-unknown-linux-gnu",
    }),
    "prelude//os:macos": select({
        "prelude//cpu:arm64": "aarch64-apple-darwin",
        "prelude//cpu:x86_64": "x86_64-apple-darwin",
    }),
    "prelude//os:windows": select({
        "prelude//cpu:arm64": select({
            # Rustup's default ABI for the host on Windows is MSVC, not GNU.
            "DEFAULT": "aarch64-pc-windows-msvc",
            "prelude//abi:gnu": "aarch64-pc-windows-gnu",
            "prelude//abi:msvc": "aarch64-pc-windows-msvc",
        }),
        "prelude//cpu:x86_64": select({
            "DEFAULT": "x86_64-pc-windows-msvc",
            "prelude//abi:gnu": "x86_64-pc-windows-gnu",
            "prelude//abi:msvc": "x86_64-pc-windows-msvc",
        }),
    }),
})


def _codex_rust_toolchain_impl(ctx):
    # Buck doesn't have a built-in notion of "Cargo profiles", but it's useful
    # to provide a simple local knob that roughly matches `cargo build` vs
    # `cargo build --release`.
    #
    # Default is "dev" to match local development expectations.
    rust_profile = read_config("codex", "rust_profile", "dev")
    extra_rustc_flags = []
    if rust_profile == "release":
        # Roughly mirrors Cargo's release defaults (not a perfect match).
        extra_rustc_flags = [
            "-C",
            "opt-level=3",
            "-C",
            "debuginfo=0",
        ]

    return [
        DefaultInfo(),
        RustToolchainInfo(
            allow_lints = ctx.attrs.allow_lints,
            clippy_driver = RunInfo(args = [ctx.attrs.clippy_driver]),
            clippy_toml = ctx.attrs.clippy_toml[DefaultInfo].default_outputs[0] if ctx.attrs.clippy_toml else None,
            compiler = RunInfo(args = [ctx.attrs.rustc]),
            default_edition = ctx.attrs.default_edition,
            deny_lints = ctx.attrs.deny_lints,
            doctests = ctx.attrs.doctests,
            nightly_features = ctx.attrs.nightly_features,
            panic_runtime = PanicRuntime("unwind"),
            report_unused_deps = ctx.attrs.report_unused_deps,
            rustc_binary_flags = ctx.attrs.rustc_binary_flags,
            rustc_flags = ctx.attrs.rustc_flags + extra_rustc_flags,
            rustc_target_triple = ctx.attrs.rustc_target_triple,
            rustc_test_flags = ctx.attrs.rustc_test_flags,
            rustdoc = RunInfo(args = [ctx.attrs.rustdoc]),
            rustdoc_flags = ctx.attrs.rustdoc_flags,
            warn_lints = ctx.attrs.warn_lints,
            # Enable the prelude's "metadata-only rlib" behavior consistently
            # across the crate graph. This avoids rustc "found possibly newer
            # version of crate ..." (E0460) mismatches between binaries and
            # libraries in large Rust graphs.
            advanced_unstable_linking = ctx.attrs.advanced_unstable_linking,
        ),
    ]


codex_rust_toolchain = rule(
    impl = _codex_rust_toolchain_impl,
    attrs = {
        "advanced_unstable_linking": attrs.bool(default = True),
        "allow_lints": attrs.list(attrs.string(), default = []),
        # Prefer explicit tool paths so the Buck execution directory doesn't
        # affect rustup toolchain resolution.
        "clippy_driver": attrs.string(default = "clippy-driver"),
        "clippy_toml": attrs.option(attrs.dep(providers = [DefaultInfo]), default = None),
        "default_edition": attrs.option(attrs.string(), default = None),
        "deny_lints": attrs.list(attrs.string(), default = []),
        "doctests": attrs.bool(default = False),
        "nightly_features": attrs.bool(default = False),
        "report_unused_deps": attrs.bool(default = False),
        "rustc": attrs.string(default = "rustc"),
        "rustc_binary_flags": attrs.list(attrs.arg(), default = []),
        "rustc_flags": attrs.list(attrs.arg(), default = []),
        "rustc_target_triple": attrs.string(default = _DEFAULT_TRIPLE),
        "rustc_test_flags": attrs.list(attrs.arg(), default = []),
        "rustdoc": attrs.string(default = "rustdoc"),
        "rustdoc_flags": attrs.list(attrs.arg(), default = []),
        "warn_lints": attrs.list(attrs.string(), default = []),
    },
    is_toolchain_rule = True,
)