# 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.

import("//build_overrides/pigweed.gni")

declare_args() {
  # Scope defining the current toolchain. Contains all of the arguments required
  # by the generate_toolchain template.
  pw_toolchain_SCOPE = {
  }

  # Prefix for compilation commands (e.g. the path to a Goma or CCache compiler
  # launcher). Example for ccache:
  #   gn gen out --args='pw_command_launcher="ccache"'
  pw_command_launcher = ""
}

# Creates a toolchain target.
#
# Args:
#   ar: (required) String indicating the archive tool to use.
#   cc: (required) String indicating the C compiler to use.
#   cxx: (required) String indicating the C++ compiler to use.
#   is_host_toolchain: (optional) Boolean indicating if the outputs are meant
#     for the $host_os.
#   final_binary_extension: (optional) The extension to apply to final linked
#     binaries.
#   link_whole_archive: (optional) Boolean indicating if the linker should load
#     all object files when resolving symbols.
#   link_group: (optional) Boolean indicating if the linker should use
#     a group to resolve circular dependencies between artifacts.
#   defaults: (required) A scope setting defaults to apply to GN
#     targets in this toolchain, as described in pw_vars_default.gni
#
# The defaults scope should contain values for builtin GN arguments:
#   current_cpu: The CPU of the toolchain.
#     Well known values include "arm", "arm64", "x64", "x86", and "mips".
#   current_os: The OS of the toolchain. Defaults to "".
#     Well known values include "win", "mac", "linux", "android", and "ios".
#
template("generate_toolchain") {
  assert(defined(invoker.defaults), "toolchain is missing 'defaults'")

  # In multi-toolchain builds from the top level, we run into issues where
  # toolchains defined with this template are re-generated each time. To avoid
  # collisions, the actual toolchain is only generated for the default (dummy)
  # toolchain, and an unused target is created otherwise.
  if (current_toolchain == default_toolchain) {
    invoker_toolchain_args = invoker.defaults

    # These values should always be set as they influence toolchain
    # behavior, but allow them to be unset as a transitional measure.
    if (!defined(invoker_toolchain_args.current_cpu)) {
      invoker_toolchain_args.current_cpu = ""
    }
    if (!defined(invoker_toolchain_args.current_os)) {
      invoker_toolchain_args.current_os = ""
    }

    # Determine OS of toolchain, which is the builtin argument "current_os".
    toolchain_os = invoker_toolchain_args.current_os

    toolchain(target_name) {
      assert(defined(invoker.cc), "toolchain is missing 'cc'")
      tool("asm") {
        if (pw_command_launcher != "") {
          command_launcher = pw_command_launcher
        }
        depfile = "{{output}}.d"
        command = string_join(" ",
                              [
                                invoker.cc,
                                "-MMD -MF $depfile",  # Write out dependencies.
                                "{{asmflags}}",
                                "{{cflags}}",
                                "{{defines}}",
                                "{{include_dirs}}",
                                "-c {{source}}",
                                "-o {{output}}",
                              ])
        depsformat = "gcc"
        description = "as {{output}}"
        outputs = [
          # Use {{source_file_part}}, which includes the extension, instead of
          # {{source_name_part}} so that object files created from <file_name>.c
          # and <file_name>.cc sources are unique.
          "{{source_out_dir}}/{{target_output_name}}.{{source_file_part}}.o",
        ]
      }

      tool("cc") {
        if (pw_command_launcher != "") {
          command_launcher = pw_command_launcher
        }
        depfile = "{{output}}.d"
        command = string_join(" ",
                              [
                                invoker.cc,
                                "-MMD -MF $depfile",  # Write out dependencies.
                                "{{cflags}}",
                                "{{cflags_c}}",  # Must come after {{cflags}}.
                                "{{defines}}",
                                "{{include_dirs}}",
                                "-c {{source}}",
                                "-o {{output}}",
                              ])
        depsformat = "gcc"
        description = "cc {{output}}"
        outputs = [
          "{{source_out_dir}}/{{target_output_name}}.{{source_file_part}}.o",
        ]
      }

      assert(defined(invoker.cxx), "toolchain is missing 'cxx'")
      tool("cxx") {
        if (pw_command_launcher != "") {
          command_launcher = pw_command_launcher
        }
        depfile = "{{output}}.d"
        command = string_join(" ",
                              [
                                invoker.cxx,
                                "-MMD -MF $depfile",  # Write out dependencies.
                                "{{cflags}}",
                                "{{cflags_cc}}",  # Must come after {{cflags}}.
                                "{{defines}}",
                                "{{include_dirs}}",
                                "-c {{source}}",
                                "-o {{output}}",
                              ])
        depsformat = "gcc"
        description = "c++ {{output}}"
        outputs = [
          "{{source_out_dir}}/{{target_output_name}}.{{source_file_part}}.o",
        ]
      }

      tool("objc") {
        if (pw_command_launcher != "") {
          command_launcher = pw_command_launcher
        }
        depfile = "{{output}}.d"
        command =
            string_join(" ",
                        [
                          invoker.cc,
                          "-MMD -MF $depfile",  # Write out dependencies.
                          "{{cflags}}",
                          "{{cflags_objc}}",  # Must come after {{cflags}}.
                          "{{defines}}",
                          "{{include_dirs}}",
                          "{{framework_dirs}}",
                          "-c {{source}}",
                          "-o {{output}}",
                        ])
        depsformat = "gcc"
        description = "objc {{output}}"
        outputs = [
          "{{source_out_dir}}/{{target_output_name}}.{{source_file_part}}.o",
        ]
      }

      tool("objcxx") {
        if (pw_command_launcher != "") {
          command_launcher = pw_command_launcher
        }
        depfile = "{{output}}.d"
        command =
            string_join(" ",
                        [
                          invoker.cxx,
                          "-MMD -MF $depfile",  # Write out dependencies.
                          "{{cflags}}",
                          "{{cflags_objcc}}",  # Must come after {{cflags}}.
                          "{{defines}}",
                          "{{include_dirs}}",
                          "{{framework_dirs}}",
                          "-c {{source}}",
                          "-o {{output}}",
                        ])
        depsformat = "gcc"
        description = "objc++ {{output}}"
        outputs = [
          "{{source_out_dir}}/{{target_output_name}}.{{source_file_part}}.o",
        ]
      }

      assert(defined(invoker.ar), "toolchain is missing 'ar'")
      tool("alink") {
        command = "rm -f {{output}} && ${invoker.ar} rcs {{output}} {{inputs}}"
        description = "ar {{target_output_name}}{{output_extension}}"
        outputs =
            [ "{{output_dir}}/{{target_output_name}}{{output_extension}}" ]
        default_output_extension = ".a"
        default_output_dir = "{{target_out_dir}}/lib"
      }

      lib_switch = "-l"
      lib_dir_switch = "-L"

      _link_outfile =
          "{{output_dir}}/{{target_output_name}}{{output_extension}}"
      _link_mapfile = "{{output_dir}}/{{target_output_name}}.map"
      _link_flags = [
        invoker.cxx,
        "{{ldflags}}",
      ]

      if (toolchain_os == "mac" || toolchain_os == "ios") {
        _link_flags += [
          # Output a map file that shows symbols and their location.
          "-Wl,-map,$_link_mapfile",

          # Delete unreferenced sections. Helpful with -ffunction-sections.
          "-Wl,-dead_strip",
        ]
      } else {
        _link_flags += [
          # Output a map file that shows symbols and their location.
          "-Wl,-Map,$_link_mapfile",

          # Delete unreferenced sections. Helpful with -ffunction-sections.
          "-Wl,--gc-sections",
        ]
      }

      _link_group = defined(invoker.link_group) && invoker.link_group
      if (_link_group) {
        _link_flags += [ "-Wl,--start-group" ]
      }
      _link_flags += [ "{{inputs}}" ]
      _link_flags += [ "{{frameworks}}" ]

      if (defined(invoker.link_whole_archive) && invoker.link_whole_archive) {
        # Load all object files from all libraries to resolve symbols.
        # Short of living in the ideal world where all dependency graphs
        # among static libs are acyclic and all developers diligently
        # express such graphs in terms that GN understands, this is the
        # safest option.
        # Make sure you use this with --gc-sections, otherwise the
        # resulting binary will contain every symbol defined in every
        # input file and every static library. That could be quite a lot.
        _link_flags += [
          "-Wl,--whole-archive",
          "{{libs}}",
          "-Wl,--no-whole-archive",
        ]
      } else {
        _link_flags += [ "{{libs}}" ]
      }

      if (_link_group) {
        _link_flags += [ "-Wl,--end-group" ]
      }
      _link_flags += [ "-o $_link_outfile" ]

      _link_command = string_join(" ", _link_flags)

      tool("link") {
        command = _link_command
        description = "ld $_link_outfile"
        outputs = [ _link_outfile ]
        default_output_dir = "{{target_out_dir}}/bin"

        if (defined(invoker.final_binary_extension)) {
          default_output_extension = invoker.final_binary_extension
        } else if (toolchain_os == "win") {
          default_output_extension = ".exe"
        } else {
          default_output_extension = ""
        }
      }

      tool("solink") {
        command = _link_command + " -shared"
        description = "ld -shared $_link_outfile"
        outputs = [ _link_outfile ]
        default_output_dir = "{{target_out_dir}}/lib"
        default_output_extension = ".so"
      }

      tool("stamp") {
        if (host_os == "win") {
          command = "cmd /c type nul > \"{{output}}\""
        } else {
          command = "touch {{output}}"
        }
        description = "stamp {{output}}"
      }

      tool("copy") {
        if (host_os != "win") {
          # Use a hard link if possible as this is faster. Also, Mac doesn't
          # preserve timestamps properly with cp -af.
          fallback_command = string_join(" ",
                                         [
                                           "rm -rf",
                                           "{{output}}",
                                           "&&",
                                           "cp -af",
                                           "{{source}}",
                                           "{{output}}",
                                         ])
          command = string_join(" ",
                                [
                                  "ln -f",
                                  "{{source}}",
                                  "{{output}}",
                                  "2>/dev/null",
                                  "||",
                                  "($fallback_command)",
                                ])
        } else {
          command = "cp -af {{source}} {{output}}"
        }
        description = "cp {{source}} {{output}}"
      }

      # Build arguments to be overridden when compiling cross-toolchain:
      #
      #   pw_toolchain_defaults: A scope setting defaults to apply to GN targets
      #     in this toolchain. It is analogous to $pw_target_defaults in
      #     $dir_pigweed/pw_vars_default.gni.
      #
      #   pw_toolchain_SCOPE: A copy of the invoker scope that defines the
      #     toolchain. Used for generating derivative toolchains.
      #
      toolchain_args = {
        pw_toolchain_SCOPE = {
        }
        pw_toolchain_SCOPE = {
          forward_variables_from(invoker, "*")
        }
        forward_variables_from(invoker_toolchain_args, "*")
      }
    }
  } else {
    not_needed(invoker, "*")
    group(target_name) {
    }
  }
}

# Creates a series of toolchain targets with common compiler options.
#
# Args:
#   toolchains: List of scopes defining each of the desired toolchains.
#     The scope must contain a "name" variable; other variables are forwarded to
#     $generate_toolchain.
template("generate_toolchains") {
  not_needed([ "target_name" ])
  assert(defined(invoker.toolchains),
         "generate_toolchains must be called with a list of toolchains")

  # Create a target for each of the desired toolchains, appending its own cflags
  # and ldflags to the common ones.
  foreach(_toolchain, invoker.toolchains) {
    generate_toolchain(_toolchain.name) {
      forward_variables_from(_toolchain, "*", [ "name" ])
    }
  }
}