# Copyright 2020 The Pigweed Authors
#
# 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.

# gn-format disable
import("//build_overrides/pigweed.gni")

import("$dir_pw_build/input_group.gni")
import("$dir_pw_build/python_script.gni")
import("$dir_pw_build/target_types.gni")
import("nanopb.gni")
declare_args() {
  # Generators with which to compile protobuf code. These are used by the
  # pw_proto_library template to determine which build targets to create.
  #
  # Supported generators:
  #   "pwpb", "nanopb", "go"
  pw_protobuf_GENERATORS = [
    "pwpb",
    "go",
  ]
}

# Python script that invokes protoc.
_gen_script_path =
    "$dir_pw_protobuf_compiler/py/pw_protobuf_compiler/generate_protos.py"

_forwarded_vars = [
  "testonly",
  "visibility",
]

# Generates pw_protobuf C++ code for proto files, creating a source_set of the
# generated files. This is internal and should not be used outside of this file.
# Use pw_proto_library instead.
#
# Args:
#  protos: List of input .proto files.
template("_pw_pwpb_proto_library") {
  _proto_gen_dir = "$root_gen_dir/protos"
  _module_path = get_path_info(".", "abspath")
  _relative_proto_paths = rebase_path(invoker.protos, _module_path)

  _outputs = []
  foreach(_proto, _relative_proto_paths) {
    _output = string_replace(_proto, ".proto", ".pwpb.h")
    _outputs += [ "$_proto_gen_dir/$_output" ]
  }

  _gen_target = "${target_name}_gen"
  pw_python_script(_gen_target) {
    forward_variables_from(invoker, _forwarded_vars)
    script = _gen_script_path
    args = [
             "--language",
             "cc",
             "--module-path",
             _module_path,
             "--include-file",
             invoker.include_file,
             "--out-dir",
             _proto_gen_dir,
           ] + get_path_info(invoker.protos, "abspath")
    inputs = invoker.protos
    outputs = _outputs
    deps = invoker.deps
    if (defined(invoker.protoc_deps)) {
      deps += invoker.protoc_deps
    }
  }

  # For C++ proto files, the generated proto directory is added as an include
  # path for the code. This requires using "all_dependent_configs" to force the
  # include on any code that transitively depends on the generated protos.
  _include_config_target = "${target_name}_includes"
  config(_include_config_target) {
    include_dirs = [ "$_proto_gen_dir" ]
  }

  # Create a library with the generated source files.
  pw_source_set(target_name) {
    all_dependent_configs = [ ":$_include_config_target" ]
    deps = [ ":$_gen_target" ]
    public_deps = [ dir_pw_protobuf ] + invoker.gen_deps
    sources = get_target_outputs(":$_gen_target")
    public = filter_include(sources, [ "*.pwpb.h" ])
  }
}

# Generates nanopb code for proto files, creating a source_set of the generated
# files. This is internal and should not be used outside of this file. Use
# pw_proto_library instead.
#
# Args:
#  protos: List of input .proto files.
template("_pw_nanopb_proto_library") {
  assert(defined(dir_pw_third_party_nanopb) && dir_pw_third_party_nanopb != "",
         "\$dir_pw_third_party_nanopb must be set to compile nanopb protobufs")

  _proto_gen_dir = "$root_gen_dir/protos"
  _module_path = get_path_info(".", "abspath")
  _relative_proto_paths = rebase_path(invoker.protos, _module_path)

  _outputs = []
  foreach(_proto, _relative_proto_paths) {
    _output_h = string_replace(_proto, ".proto", ".pb.h")
    _output_c = string_replace(_proto, ".proto", ".pb.c")
    _outputs += [
      "$_proto_gen_dir/$_output_h",
      "$_proto_gen_dir/$_output_c",
    ]
  }

  _nanopb_plugin = "$dir_pw_third_party_nanopb/generator/protoc-gen-nanopb"
  if (host_os == "win") {
    _nanopb_plugin += ".bat"
  }

  # Create a target which runs protoc configured with the nanopb plugin to
  # generate the C proto sources.
  _gen_target = "${target_name}_gen"
  pw_python_script(_gen_target) {
    forward_variables_from(invoker, _forwarded_vars)
    script = _gen_script_path
    args = [
             "--language",
             "nanopb",
             "--module-path",
             _module_path,
             "--include-paths",
             "$dir_pw_third_party_nanopb/generator/proto",
             "--include-file",
             invoker.include_file,
             "--out-dir",
             _proto_gen_dir,
             "--custom-plugin",
             get_path_info(_nanopb_plugin, "abspath"),
           ] + get_path_info(invoker.protos, "abspath")
    inputs = invoker.protos
    outputs = _outputs

    deps = invoker.deps
    if (defined(invoker.protoc_deps)) {
      deps += invoker.protoc_deps
    }
  }

  # For C++ proto files, the generated proto directory is added as an include
  # path for the code. This requires using "all_dependent_configs" to force the
  # include on any code that transitively depends on the generated protos.
  _include_root = rebase_path(get_path_info(".", "abspath"), "//")
  _include_config_target = "${target_name}_includes"
  config(_include_config_target) {
    include_dirs = [
      "$_proto_gen_dir",
      "$_proto_gen_dir/$_include_root",
    ]
  }

  # Create a library with the generated source files.
  pw_source_set(target_name) {
    all_dependent_configs = [ ":$_include_config_target" ]
    deps = [ ":$_gen_target" ]
    public_deps = [ dir_pw_third_party_nanopb ] + invoker.gen_deps
    sources = get_target_outputs(":$_gen_target")
    public = filter_include(sources, [ "*.pb.h" ])
  }
}

# Generates Go code for proto files, listing the proto output directory in the
# metadata variable GOPATH. Internal use only.
#
# Args:
#  protos: List of input .proto files.
template("_pw_go_proto_library") {
  _proto_gopath = "$root_gen_dir/go"
  _proto_gen_dir = "$_proto_gopath/src"
  _rebased_gopath = rebase_path(_proto_gopath)

  pw_python_script(target_name) {
    forward_variables_from(invoker, _forwarded_vars)
    metadata = {
      gopath = [ "GOPATH+=$_rebased_gopath" ]
      external_deps = [
        "github.com/golang/protobuf/proto",
        "google.golang.org/grpc",
      ]
    }
    script = _gen_script_path
    args = [
             "--language",
             "go",
             "--module-path",
             "//",
             "--include-file",
             invoker.include_file,
             "--out-dir",
             _proto_gen_dir,
           ] + get_path_info(invoker.protos, "abspath")
    inputs = invoker.protos
    deps = invoker.deps + invoker.gen_deps
    stamp = true
  }
}

# Generates protobuf code from .proto definitions for various languages.
#
# The generators to use are defined in the pw_protobuf_GENERATORS build
# variable. Each listed generator creates a generated code target called
#
#   <target_name>_<generator>
#
# For example, with the following definitions:
#
#   pw_protobuf_GENERATORS = [ "pwpb", "py" ]
#
#   pw_proto_library("my_protos") {
#     sources = [ "foo.proto" ]
#   }
#
# Two build targets will be created for the declared "my_protos" target.
#
#   "my_protos_pwpb"  <-- C++ source_set containing generated proto code
#   "my_protos_py"    <-- Python module containing generated proto code
#
# Args:
#  sources: List of input .proto files.
#  deps: List of other pw_proto_library dependencies.
#  inputs: Other files on which the protos depend (e.g. nanopb .options files).
template("pw_proto_library") {
  assert(defined(invoker.sources) && invoker.sources != [],
         "pw_proto_library requires .proto source files")

  # For each proto target, create a file which collects the base directories of
  # all of its dependencies to list as include paths to protoc.
  _include_metadata_target = "${target_name}_include_paths"
  _include_metadata_file = "${target_gen_dir}/${target_name}_includes.txt"
  generated_file(_include_metadata_target) {
    if (defined(invoker.deps)) {
      # Collect metadata from the include path files of each dependency.
      deps = process_file_template(invoker.deps, "{{source}}_include_paths")
    } else {
      deps = []
    }
    data_keys = [ "protoc_includes" ]
    outputs = [ _include_metadata_file ]

    # Indicate this library's base directory for its dependents.
    metadata = {
      protoc_includes = [ rebase_path(".") ]
    }
  }

  _deps = [ ":$_include_metadata_target" ]

  if (defined(invoker.inputs)) {
    # Toss any additional inputs into an input group dependency.
    _input_target_name = "${target_name}_inputs"
    pw_input_group(_input_target_name) {
      inputs = invoker.inputs
    }
    _deps += [ ":$_input_target_name" ]
  }

  foreach(_gen, pw_protobuf_GENERATORS) {
    _lang_target = "${target_name}_${_gen}"
    _gen_deps = []
    if (defined(invoker.deps)) {
      _gen_deps = process_file_template(invoker.deps, "{{source}}_${_gen}")
    }

    if (_gen == "pwpb") {
      _pw_pwpb_proto_library(_lang_target) {
        forward_variables_from(invoker, _forwarded_vars)
        protos = invoker.sources
        deps = _deps
        include_file = _include_metadata_file
        gen_deps = _gen_deps

        # List the pw_protobuf plugin's files as a dependency to recompile
        # generated code if they are modified.
        protoc_deps = [ "$dir_pw_protobuf:codegen_protoc_plugin" ]
      }
    } else if (_gen == "nanopb") {
      _pw_nanopb_proto_library(_lang_target) {
        forward_variables_from(invoker, _forwarded_vars)
        protos = invoker.sources
        deps = _deps
        include_file = _include_metadata_file
        gen_deps = _gen_deps
      }
    } else if (_gen == "go") {
      _pw_go_proto_library(_lang_target) {
        forward_variables_from(invoker, _forwarded_vars)
        protos = invoker.sources
        deps = _deps
        include_file = _include_metadata_file
        gen_deps = _gen_deps
      }
    } else {
      assert(false,
             string_join(
                 " ",
                 [
                   "pw_proto_library doesn't know how to generate code for",
                   "generator '$_gen'. Please add support if you require it.",
                 ]))
    }
  }

  # All supported pw_protobuf generators.
  _protobuf_generators = [
    "pwpb",
    "nanopb",
    "go",
  ]

  # Create stub versions of the proto library for other protobuf generators.
  foreach(_gen, _protobuf_generators - pw_protobuf_GENERATORS) {
    pw_python_script("${target_name}_${_gen}") {
      forward_variables_from(invoker, _forwarded_vars)
      script = string_join("/",
                           [
                             dir_pw_protobuf_compiler,
                             "py",
                             "pw_protobuf_compiler",
                             "generator_not_selected.py",
                           ])
      args = [
        "--library",
        "${target_name}_${_gen}",
        "--generator",
        _gen,
      ]
      inputs = invoker.sources
      stamp = true
    }
  }

  # If the user attempts to use the target directly instead of one of the
  # generator targets, run a script which prints a nice error message.
  pw_python_script(target_name) {
    script = string_join("/",
                         [
                           dir_pw_protobuf_compiler,
                           "py",
                           "pw_protobuf_compiler",
                           "proto_target_invalid.py",
                         ])
    args = [
             "--target",
             target_name,
             "--dir",
             get_path_info(".", "abspath"),
             "--root",
             "//",
           ] + pw_protobuf_GENERATORS
    stamp = true
  }
}