# Copyright 2020 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Defines a rule for creating an instrumented fuzzing executable."""

load("//fuzzing/private:engine.bzl", "CcFuzzingEngineInfo")
load(
    "//fuzzing/private:instrum_opts.bzl",
    "instrum_defaults",
    "instrum_opts",
)
load(
    "//fuzzing:instrum_opts.bzl",
    "instrum_configs",
    "sanitizer_configs",
)

CcFuzzingBinaryInfo = provider(
    doc = """
Provider for storing information about a fuzz test binary.
""",
    fields = {
        "binary_file": "The instrumented fuzz test executable.",
        "binary_runfiles": "The runfiles of the fuzz test executable.",
        "corpus_dir": "The directory of the corpus files used as input seeds.",
        "dictionary_file": "The dictionary file to use in fuzzing runs.",
        "engine_info": "The `CcFuzzingEngineInfo` provider of the fuzzing engine used in the fuzz test.",
    },
)

def _fuzzing_binary_transition_impl(settings, attr):
    opts = instrum_opts.make(
        copts = settings["//command_line_option:copt"],
        conlyopts = settings["//command_line_option:conlyopt"],
        cxxopts = settings["//command_line_option:cxxopt"],
        linkopts = settings["//command_line_option:linkopt"],
    )

    is_fuzzing_build_mode = settings["@rules_fuzzing//fuzzing:cc_fuzzing_build_mode"]
    if is_fuzzing_build_mode:
        opts = instrum_opts.merge(opts, instrum_defaults.fuzzing_build)

    instrum_config = settings["@rules_fuzzing//fuzzing:cc_engine_instrumentation"]
    if instrum_config in instrum_configs:
        opts = instrum_opts.merge(opts, instrum_configs[instrum_config])
    else:
        fail("unsupported engine instrumentation '%s'" % instrum_config)

    sanitizer_config = settings["@rules_fuzzing//fuzzing:cc_engine_sanitizer"]
    if sanitizer_config in sanitizer_configs:
        opts = instrum_opts.merge(opts, sanitizer_configs[sanitizer_config])
    else:
        fail("unsupported sanitizer '%s'" % sanitizer_config)

    return {
        "//command_line_option:copt": opts.copts,
        "//command_line_option:linkopt": opts.linkopts,
        "//command_line_option:conlyopt": opts.conlyopts,
        "//command_line_option:cxxopt": opts.cxxopts,
        # Make sure binaries are built statically, to maximize the scope of the
        # instrumentation.
        "//command_line_option:dynamic_mode": "off",
    }

fuzzing_binary_transition = transition(
    implementation = _fuzzing_binary_transition_impl,
    inputs = [
        "@rules_fuzzing//fuzzing:cc_engine_instrumentation",
        "@rules_fuzzing//fuzzing:cc_engine_sanitizer",
        "@rules_fuzzing//fuzzing:cc_fuzzing_build_mode",
        "//command_line_option:copt",
        "//command_line_option:conlyopt",
        "//command_line_option:cxxopt",
        "//command_line_option:linkopt",
    ],
    outputs = [
        "//command_line_option:copt",
        "//command_line_option:conlyopt",
        "//command_line_option:cxxopt",
        "//command_line_option:linkopt",
        "//command_line_option:dynamic_mode",
    ],
)

def _fuzzing_binary_impl(ctx):
    output_file = ctx.actions.declare_file(ctx.label.name)
    ctx.actions.symlink(
        output = output_file,
        target_file = ctx.executable.binary,
        is_executable = True,
    )
    binary_runfiles = ctx.attr.binary[0][DefaultInfo].default_runfiles
    other_runfiles = []
    if ctx.file.corpus:
        other_runfiles.append(ctx.file.corpus)
    if ctx.file.dictionary:
        other_runfiles.append(ctx.file.dictionary)
    return [
        DefaultInfo(
            executable = output_file,
            runfiles = binary_runfiles.merge(ctx.runfiles(files = other_runfiles)),
        ),
        CcFuzzingBinaryInfo(
            binary_file = ctx.executable.binary,
            binary_runfiles = binary_runfiles,
            corpus_dir = ctx.file.corpus,
            dictionary_file = ctx.file.dictionary,
            engine_info = ctx.attr.engine[CcFuzzingEngineInfo],
        ),
    ]

fuzzing_binary = rule(
    implementation = _fuzzing_binary_impl,
    doc = """
Creates an instrumented fuzzing executable.

The executable runfiles include the corpus directory and the dictionary file,
if specified.

The instrumentation is controlled by the following flags:

 * `@rules_fuzzing//fuzzing:cc_engine_instrumentation`
 * `@rules_fuzzing//fuzzing:cc_engine_sanitizer`
 * `@rules_fuzzing//fuzzing:cc_fuzzing_build_mode`
""",
    attrs = {
        "binary": attr.label(
            executable = True,
            doc = "The fuzz test executable to instrument.",
            cfg = fuzzing_binary_transition,
            mandatory = True,
        ),
        "engine": attr.label(
            doc = "The specification of the fuzzing engine used in the binary.",
            providers = [CcFuzzingEngineInfo],
            mandatory = True,
        ),
        "corpus": attr.label(
            doc = "A directory of corpus files used as input seeds.",
            allow_single_file = True,
        ),
        "dictionary": attr.label(
            doc = "A dictionary file to use in fuzzing runs.",
            allow_single_file = True,
        ),
        "_allowlist_function_transition": attr.label(
            default = "@bazel_tools//tools/allowlists/function_transition_allowlist",
        ),
    },
    executable = True,
    provides = [CcFuzzingBinaryInfo],
)