# 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.

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

# Defines an SDK element.
#
# Outputs
#
#   $target_gen_dir/$target_name.sdk
#     A manifest describing what files pertain to the atom and which other atoms
#     are required by this atom.
#
#   $target_gen_dir/$target_name.meta.json
#     A metadata file describing the atom.
#     This file is included in the final SDK and used to e.g. drive the
#     inclusion of the atom in a different build system.
#
# Parameters
#
#   id
#     Identifier of this element within SDKs.
#     The identifier should represent the canonical base path of the element
#     within SDKs according to the standard layout (https://fuchsia.googlesource.com/docs/+/master/development/sdk/layout.md).
#     For an element at $ROOT/pkg/foo, the id should be "sdk://pkg/foo".
#
#   category
#     Describes the availability of the element.
#     Possible values, from most restrictive to least restrictive:
#       - excluded     : the atom may not be included in SDKs;
#       - experimental : the atom is available with no quality guarantee;
#       - internal     : the atom is exposed within the Fuchsia tree;
#       - partner      : the atom may be used by select partners;
#       - public       : the atom may be included in published SDKs.
#
#   meta
#     Scope describing the element's metadata file.
#     See the "Metadata scope" section for how to populate this attribute.
#
#   files
#     List of scopes describing the contents of this element.
#     See the "File scopes" section for how to describe files.
#
#   file_list
#     Path to a file containing file mappings.
#     Each line in the file should contain a "dest=source" mapping, similarly to
#     file scopes.
#
#   deps (optional)
#     List of GN labels for other SDK elements this element depends on at build
#     time.
#     These labels must point to "sdk_atom" targets.
#
#   non_sdk_deps (optional)
#     List of GN labels which this target needs built.
#
# Metadata scope
#
# This scope describes a metadata file to be added to the SDK element. Its
# supported attributes are:
#
#   source (optional)
#     Path to the metadata file.
#
#   value (optional)
#     Scope representing the metadata contents.
#
#     NOTE: Exactly one of `source` or `value` must be set.
#
#   dest (required)
#     Path to the metadata file in the SDK, relatively to the SDK root
#
#   schema (required)
#     Name of the schema for this file, ignoring the extension.
#     Metadata files are hosted under //build/sdk/meta.
#     If the metadata file conforms to //build/sdk/meta/foo.json, the
#     present attribute should have a value of "foo".
#
# File scopes
#
# Each scope describes a file to be added to the SDK element. The supported
# attributes are:
#
#   source (required)
#     Path to the original file.
#     This path may be absolute or relative to the target's directory.
#
#   dest (required)
#     Destination path of the file relative to the SDK root.

template("sdk_atom") {
  assert(defined(invoker.category), "Must define an SDK category")
  category = invoker.category

  assert(defined(invoker.id), "Must define an SDK ID")

  assert(defined(invoker.meta), "Must specify some metadata")
  meta = invoker.meta

  gn_deps = []
  if (defined(invoker.non_sdk_deps)) {
    gn_deps = invoker.non_sdk_deps
  }

  dep_manifests = []
  if (defined(invoker.deps)) {
    gn_deps += invoker.deps
    foreach(dep, invoker.deps) {
      gen_dir = get_label_info(dep, "target_gen_dir")
      name = get_label_info(dep, "name")
      dep_manifests += [ rebase_path("$gen_dir/$name.sdk") ]
    }
  }

  assert(defined(invoker.files), "An atom must specify some files")
  file_args = []
  file_inputs = []
  foreach(file, invoker.files) {
    assert(defined(file.source), "File $file does not specify a source.")
    assert(defined(file.dest), "File $file does not specify a destination.")
    file_inputs += [ file.source ]
    source = rebase_path(file.source)
    file_args += [
      "--file",
      file.dest,
      source,
    ]
  }

  meta_target_name = "${target_name}_meta"
  meta_content = invoker.meta
  meta_file = "$target_gen_dir/$target_name.meta.json"

  if (defined(meta_content.value)) {
    # Directly write the value into a file in the output directory.
    write_file(meta_file, meta_content.value, "json")
    meta_deps = gn_deps
  } else {
    meta_copy_target_name = "${target_name}_meta_copy"
    assert(defined(meta_content.source), "Meta scope needs a source or value")

    # Copy the file to a canonical location for access by other rules.
    # TODO(DX-497): instead, make sure that all atoms generate their metadata
    # file in the right location.
    copy(meta_copy_target_name) {
      sources = [
        meta_content.source,
      ]

      outputs = [
        meta_file,
      ]

      deps = gn_deps
    }

    meta_deps = [ ":$meta_copy_target_name" ]
  }

  # Verify that the metadata complies with the specified schema.
  validate_json(meta_target_name) {
    forward_variables_from(invoker, [ "testonly" ])
    data = meta_file
    schema = "//build/sdk/meta/${meta_content.schema}.json"
    sources = [
      # This file is imported by all schemas.
      "//build/sdk/meta/common.json",
    ]
    public_deps = meta_deps
  }

  # Add the metadata file to the set of files to include in SDKs.
  meta_source = rebase_path(meta_file)
  file_args += [
    "--file",
    meta.dest,
    meta_source,
  ]

  # Builds a manifest representing this element.
  action(target_name) {
    forward_variables_from(invoker, [ "testonly" ])

    manifest = "$target_gen_dir/$target_name.sdk"
    depfile = "$manifest.d"

    script = "//build/sdk/create_atom_manifest.py"

    public_deps = gn_deps + [ ":$meta_target_name" ]

    inputs = dep_manifests + file_inputs + [
               # Imported by the action's script.
               "//build/sdk/sdk_common.py",
             ]

    outputs = [
      manifest,
    ]

    args = [
             "--id",
             invoker.id,
             "--out",
             rebase_path(manifest, root_build_dir),
             "--depfile",
             rebase_path(depfile),
             "--gn-label",
             get_label_info(":$target_name", "label_with_toolchain"),
             "--category",
             category,
             "--meta",
             meta.dest,
             "--deps",
           ] + dep_manifests + file_args

    if (defined(invoker.file_list)) {
      args += [
        "--file-list",
        rebase_path(invoker.file_list),
      ]
    }
  }
}