# Copyright 2021 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/dist/resource.gni")
import("//build/images/shell_commands.gni")

# This template can be used in the seldom case where it is necessary
# to install inside a Fuchsia package a binary under a different name
# than its original one.
#
# For example:
#
#    # Install bin/update as a copy of bin/multi_universal_tool
#    # in any Fuchsia package that depends on this target.
#    renamed_binary("pkgsvr-binary") {
#      source = "$root_out_dir/multi_universal_tool"
#      source_deps = [ "//src/sys/pkg/bin/multi-universal-tool" ]
#      dest = "bin/update"
#    }
#
# Compared to a resource() target that does the same thing, this
# one also ensures that all runtime library dependencies will
# be properly installed as well.
#
# It is possible to use several renamed_binary() targets that all
# use the same source binary, each one will correspond to a different
# copy installed into the package.
#
# Note that the original binary file will _not_ be installed by default.
# This can be overridden by setting `keep_original` to true, in at least
# one of the renamed_binary() targets that use it.
#
# Optionally, one can also declare that the binary should be
# available in the shell, when a given package depends on this
# target. This is useful when fuchsia_shell_package() cannot be
# used directly, which happens when one does not want _all_ binaries
# in the packages to be made visible to shell users (including
# the original one, which is often undesirable).
#
# In other words:
#
#   renamed_binary("my-binary") {
#     dest = "bin/foo"
#     source = "$root_out_dir/original_binary"
#     source_deps = ...
#   }
#
#   fuchsia_shell_package("my-package") {
#     ...
#     deps = [ ":my-binary" ]
#   }
#
# Will make both 'foo' and 'original_binary' available to the
# shell, while:
#
#   renamed_binary("my-binary") {
#     dest = "bin/foo"
#     source = "$root_out_dir/original_binary"
#     source_deps = ...
#     fuchsia_shell_package_name = "my-package"
#   }
#
#   fuchsia_package_with_single_component("my-package") {
#     ...
#     deps = [ ":my-binary" ]
#   }
#
# Will only make 'foo' available to the shell, which is
# generally better.
#
# Finally, it is not possible to mix resource() and renamed_binary()
# targets that use the same source path. This will be detected as a
# conflict during the build, and an error message will be printed
# listing the affected targets. To solve the issue, simply replace
# the resource() target with a renamed_binary() one.
#
# Arguments:
#   dest (required)
#     [path] Destination path inside the package. Typically
#     begins with a 'bin/' or 'test/' prefix.
#
#   source (required)
#     [path] File path to the source executable. Typically
#     something like "$root_out_dir/<source_binary_name>"
#
#   source_deps (required)
#     [list of labels] A list of dependencies required to build
#     the source file.
#
#   fuchsia_shell_package_name (optional)
#     [string] If defined, must be a package name, and this template
#     will ensure that the renamed binary will be available from the shell
#     when said package depends on this target. Note that the
#     original source binary, while also installed in the package,
#     will _not_ be made visible to the shell through this target,
#     only the renamed one.
#
#   keep_original (optional)
#     [boolean] Set this to true to keep the original binary in the
#     package as well. By default, it will be removed, replaced by
#     its renamed version.
#
#   deps, testonly, visibility
#     Usual GN meaning.
#
template("renamed_binary") {
  main_target_name = target_name

  if (defined(invoker.fuchsia_shell_package_name)) {
    # Generate a shell wrapper for the renamed binary.
    # Do not use shell_command() here because it will create one wrapper for
    # every executable() in the dependency tree rooted at source_deps, including
    # one for the source binary. When the same source binary is used by several
    # renamed_binary() targets, this creates a conflict late in the build!
    _shell_package_name = invoker.fuchsia_shell_package_name
    _shell_file = target_gen_dir + "/" + invoker.dest + ".shell"
    _shell_file_target = "${main_target_name}.shell_file"
    generated_file(_shell_file_target) {
      outputs = [ _shell_file ]
      contents = [ "#!resolve fuchsia-pkg://fuchsia.com/${_shell_package_name}#${invoker.dest}" ]
      metadata = {
        # Used by shell_commands() template. This ensures that only the renamed binary
        # gets a shell wrapper, and not the source one.
        shell_binary_entries = [
          {
            source = rebase_path(_shell_file, root_build_dir)
            destination = invoker.dest
            label =
                get_label_info(":${main_target_name}", "label_with_toolchain")
          },
        ]
        shell_binary_barrier = []
      }
    }
  }

  group(main_target_name) {
    forward_variables_from(invoker,
                           [
                             "deps",
                             "testonly",
                             "visibility",
                           ])
    if (!defined(deps)) {
      deps = []
    }

    # Also depend on the original source binary target(s). This
    # is required to ensure that all runtime library dependencies
    # are also properly installed, because the resource() target
    # will actually block metadata collection for these.
    deps += invoker.source_deps

    if (defined(_shell_file_target)) {
      deps += [ ":${_shell_file_target}" ]
    }

    _rebased_source = rebase_path(invoker.source, root_build_dir)

    metadata = {
      # Used by the zbi() template.
      zbi_input_barrier = []

      if (defined(invoker.metadata)) {
        forward_variables_from(invoker.metadata, "*")
      }

      # Stop *_manifest() and zbi_test() from picking up files or
      # zbi_input() items from the deps, but let them reach the data_deps.
      if (defined(invoker.data_deps)) {
        zbi_input_barrier += invoker.data_deps
      }

      # Used by the distribution_manifest() template.
      # This create a 'renaming entry' as described in
      # //docs/concepts/build_system/internals/manifest_formats.mg.
      distribution_entries = [
        {
          renamed_source = _rebased_source
          destination = invoker.dest
          label = get_label_info(":$main_target_name", "label_with_toolchain")
          keep_original =
              defined(invoker.keep_original) && invoker.keep_original
        },
      ]
    }
  }
}