"""Rule for generating integrity files

Default output is a .sha256 file but .sha1 and .md5 files are also available
via output groups.

Based on https://github.com/bazelbuild/examples/blob/main/rules/implicit_output/hash.bzl
"""

def _hash(ctx, algo, file):
    coreutils = ctx.toolchains["@aspect_bazel_lib//lib:coreutils_toolchain_type"]
    out = ctx.actions.declare_file("{}.{}".format(file.basename, algo), sibling = file)
    ctx.actions.run_shell(
        outputs = [out],
        inputs = [file],
        tools = [coreutils.coreutils_info.bin],
        # coreutils has --no-names option but it doesn't work in current version, so we have to use cut.
        command = """HASH=$({coreutils} hashsum --{algo} {src} | {coreutils} cut -f1 -d " ") && {coreutils} echo -ne "$HASH {basename}" > {out}""".format(
            coreutils = coreutils.coreutils_info.bin.path,
            algo = algo,
            src = file.path,
            basename = file.basename,
            out = out.path,
        ),
    )
    return out

def _impl(ctx):
    # Create actions to generate the three output files.
    # Actions are run only when the corresponding file is requested.

    md5out = _hash(ctx, "md5", ctx.file.src)
    sha1out = _hash(ctx, "sha1", ctx.file.src)
    sha256out = _hash(ctx, "sha256", ctx.file.src)

    # By default (if you run `bazel build` on this target, or if you use it as a
    # source of another target), only the sha256 is computed.
    return [
        DefaultInfo(
            files = depset([sha256out]),
        ),
        OutputGroupInfo(
            md5 = depset([md5out]),
            sha1 = depset([sha1out]),
            sha256 = depset([sha256out]),
        ),
    ]

_hashes = rule(
    implementation = _impl,
    toolchains = [
        "@aspect_bazel_lib//lib:coreutils_toolchain_type",
    ],
    attrs = {
        "src": attr.label(
            allow_single_file = True,
            mandatory = True,
        ),
    },
)

def hashes(name, src, **kwargs):
    _hashes(
        name = name,
        src = src,
        **kwargs
    )