# Copyright 2019 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import("//build/fuzzing/fuzzer.gni")
import("//build/go/go_build.gni")
import("//build/go/go_library.gni")

go_fuzzer_wrapper_template =
    read_file("//build/go/go_fuzzer_wrapper.go", "string")

# Defines a Go fuzz target.
#
#   gopackage (required)
#     The Go package exporting the target "Fuzz" function.
#
#   deps (required)
#     List of labels representing go_library targets this target depends on.
#
#   tags (optional)
#     List of additional Go build tags to specify for the build.
#
# Additionally, the `cmx`, `dictionary`, and `options` parameters
# defined for `fuzzer` are supported.

template("go_fuzzer") {
  assert(defined(invoker.gopackage),
         "gopackage must be defined for $target_name")
  assert(defined(invoker.deps), "deps must be defined for $target_name")

  fuzzer_name = target_name

  # Building a Go fuzzer involves a few steps:
  # - Generate the wrapper source file.
  # - Define a go_library rule containing that source file.
  # - Build the wrapper package as a C archive with Go's libfuzzer instrumentation.
  # - Link the resulting C archive as though it was a normal C++ fuzzer.

  write_file("${target_gen_dir}/${fuzzer_name}_wrapper.go",
             "// Code generated by //build/go/go_fuzzer.gni; DO NOT EDIT.\n\n" +
                 string_replace(go_fuzzer_wrapper_template,
                                "GO_FUZZER_PKG",
                                invoker.gopackage))

  go_library("${fuzzer_name}_wrapper_library") {
    name = "${fuzzer_name}_wrapper"
    source_dir = "${target_gen_dir}"
    sources = [
      "${fuzzer_name}_main.go",
    ]

    forward_variables_from(invoker, [ "deps" ])
  }

  go_build("${fuzzer_name}_wrapper") {
    gopackages = [ "${fuzzer_name}_wrapper" ]
    fuzzer = true
    forward_variables_from(invoker, [ "tags" ])
    if (!defined(tags)) {
      tags = []
    }
    tags += [ "libfuzzer" ]
    deps = [
      ":${fuzzer_name}_wrapper_library",
    ]
  }

  fuzzer("${fuzzer_name}") {
    libs = [ "${root_out_dir}/${fuzzer_name}_wrapper.a" ]
    deps = [
      ":${fuzzer_name}_wrapper",
    ]
    forward_variables_from(invoker,
                           [
                             "cmx",
                             "dictionary",
                             "options",
                           ])
  }
}