# Copyright 2017 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.

# Compile a flatbuffer.
#
#   sources
#       Specifies the sources to compile.
#
#   flatc_out_dir (optional)
#       Specifies the path suffix that output files are generated under. This
#       path will be appended to root_gen_dir.
#
#       Targets that depend on the proto target will be able to include the
#       resulting flatbuffers header with an include like:
#         #include "dir/for/my_flatbuffer/buffer_generated.h"
#       If undefined, this defaults to matching the input directory for each
#       .fbs file (you should almost always use the default mode).
#
#   deps (optional)
#       Additional dependencies.
#
# Parameters for compiling the generated code:
#
#   defines (optional)
#       Defines to supply to the source set that compiles the generated source
#       code.
#
#   extra_configs (optional)
#       A list of config labels that will be appended to the configs applying
#       to the source set.
#
#   testonly (optional)
#       Boolean to indicate whether the generated source sets should be labeled
#       as testonly.
#
# Example:
#  flatbuffer("mylib") {
#    sources = [
#      "foo.fbs",
#    ]
#  }

import("//build/compiled_action.gni")

template("flatbuffer") {
  assert(defined(invoker.sources), "Need sources for flatbuffers_library")

  # Don't apply OS-specific sources filtering to the assignments later on.
  # Platform files should have gotten filtered out in the sources assignment
  # when this template was invoked. If they weren't, it was on purpose and
  # this template shouldn't re-apply the filter.
  set_sources_assignment_filter([])

  action_name = "${target_name}_gen"
  source_set_name = target_name
  compiled_action_foreach(action_name) {
    visibility = [ ":$source_set_name" ]

    tool = "//third_party/flatbuffers:flatc"

    sources = invoker.sources

    if (defined(invoker.flatc_out_dir)) {
      out_dir = "$root_gen_dir/" + invoker.flatc_out_dir
    } else {
      out_dir = "{{source_gen_dir}}"
    }

    outputs = [
      "$out_dir/{{source_name_part}}_generated.h",
    ]

    args = [
      "-c",
      "-o",
      "$out_dir",
      "{{source}}",
    ]

    # The deps may have steps that have to run before running flatc.
    if (defined(invoker.deps)) {
      deps += invoker.deps
    }
  }

  source_set(target_name) {
    forward_variables_from(invoker,
                           [
                             "visibility",
                             "defines",
                           ])

    sources = get_target_outputs(":$action_name")

    if (defined(invoker.extra_configs)) {
      configs += invoker.extra_configs
    }

    if (defined(invoker.testonly)) {
      testonly = invoker.testonly
    }

    public_configs = [ "//third_party/flatbuffers:flatbuffers_config" ]

    public_deps = [
      # The generated headers reference headers within flatbuffers, so
      # dependencies must be able to find those headers too.
      "//third_party/flatbuffers",
    ]
    deps = [
      ":$action_name",
    ]

    # This will link any libraries in the deps (the use of invoker.deps in the
    # action won't link it).
    if (defined(invoker.deps)) {
      deps += invoker.deps
    }
  }
}