# 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/group_with_inputs.gni")
import("//build/python/python_validator.gni")

# Defines a python library
#
# Example
#
# ```
# python_library("lib") {
#   library_name = "lib"
#   sources = [
#     "__init__.py",
#     "lib.py",
#   ]
# }
# ```
#
# Parameters
#
#   library_name (optional)
#     Name of the library, Python scripts can import this library by this name.
#     Type: string
#     Default: ${target_name}
#
#   source_root (optional)
#     Path to root of the package, where __init__.py is.
#     Type: path
#     Default: current directory
#
#   sources (required)
#     List of sources for this python library, relative to source_root.
#     Type: list(path)
#
#   data_sources (optional)
#     List of data sources for this python library. The sources are accessible
#     at runtime as below:
#     ```python
#     from importlib.resources import files
#     from <library_name> import <data_package_name>
#
#     with files(<data_package_name>).joinpath(<source_name>).open("rb"):
#       ...
#     ```
#     Type: list(path)
#
#   data_package_name (required if |data_sources| is provided, else optional)
#     Name of the data package to store |data_sources| in.
#     See "data_sources" above for more detail.
#     Type: string
#
#   library_deps (optional)
#    List of targets for other python_library()s that this library depends on
#    Type: list(target)
#
#   enable_mypy (optional)
#     If true, enable MyPy type checking on the target and respective deps.
#     Type: boolean
#     Default: true
#
#   stubs_root (optional)
#     Base path for paths specified in `stubs`. This argument is required when `stubs` is
#     provided.
#     Type: path
#
#   stubs(optional)
#     Paths to .pyi stub files relative to `stubs_root`. When providing this argument, `stubs_root`
#     must be provided too. The stub files provided will be copied to the Python library generated
#     by this template with the same directory structure relative to `stubs_root`.
#     Type: list(path)
#
#   assert_no_deps (optional)
#     GN usual
#
# Metadata
#
#   library_info
#     Exactly one scope including name of this library, path to its root and all
#     of its sources (relative to root) and data_sources.
#
#   library_info_barrier
#     Empty for stopping metadata walks.
template("python_library") {
  assert(defined(invoker.sources), "sources is required")

  _labels = {
    main_target = target_name
    input_group = "${target_name}_input_group"
    mypy_checker = "${target_name}_mypy_checker"
    library_infos = "${target_name}.library_infos"
  }

  _files = {
    library_infos = "${target_gen_dir}/${target_name}_library_infos.json"
  }

  library_deps = []
  if (defined(invoker.library_deps)) {
    library_deps = invoker.library_deps
  }

  _data_sources = []
  _data_package_name = ""
  if (defined(invoker.data_sources)) {
    assert(defined(invoker.data_package_name),
           "data_package_name is required if data_sources are provided")
    _data_sources = invoker.data_sources
    _data_package_name = invoker.data_package_name
  }

  # Add the sources from the invoker
  if (defined(invoker.source_root)) {
    _source_root = invoker.source_root
  } else {
    _source_root = get_label_info(":$target_name", "dir")
  }
  _full_source_paths = []
  foreach(source, invoker.sources) {
    _full_source_paths += [ _source_root + "/" + source ]
  }

  _full_stub_paths = []
  if (defined(invoker.stubs)) {
    assert(defined(invoker.stubs_root),
           "stubs_root must be provided with stubs")
    foreach(stub, invoker.stubs) {
      _full_stub_paths += [ invoker.stubs_root + "/" + stub ]
    }
  }

  _full_data_source_paths = []
  foreach(data_source, _data_sources) {
    _full_data_source_paths += [ rebase_path(data_source, root_build_dir) ]
  }

  _enable_mypy = true
  if (defined(invoker.enable_mypy)) {
    _enable_mypy = invoker.enable_mypy
  }

  _library_name = target_name
  if (defined(invoker.library_name)) {
    _library_name = invoker.library_name
  }
  group_with_inputs(_labels.input_group) {
    forward_variables_from(invoker,
                           [
                             "assert_no_deps",
                             "testonly",
                             "visibility",
                           ])

    # Seed with the library_deps, and then add any other deps as well
    deps = library_deps
    if (defined(invoker.deps)) {
      deps += invoker.deps
    }

    source_root = _source_root
    metadata = {
      library_info = [
        {
          library_name = _library_name
          source_root = rebase_path(source_root, root_build_dir)
          sources = invoker.sources
          data_package_name = _data_package_name
          data_sources = _full_data_source_paths

          # Label a library as having mypy support if it includes stubs.
          # When included as a dependency, the libraries stubs will be
          # included in the type checking.
          mypy_support = _enable_mypy || defined(invoker.stubs)
          mypy_enable = _enable_mypy
          if (defined(invoker.stubs)) {
            stubs_root = rebase_path(invoker.stubs_root, root_build_dir)
            stubs = invoker.stubs
          }
        },
      ]

      # List sources outside of //out as additional source roots for Python IDE
      # tooling.
      #
      # The main case where sources inside //out are needed is for fidling,
      # which is handled by fidl_python_output metadata keys in the FIDL build
      # rules.
      if (string_replace(source_root, "//out", "") == source_root) {
        # Get the directory where the source_root exists.
        extra_python_dirs = [ rebase_path(source_root + "/..", root_build_dir) ]
      }

      # Collect library_info from any libraries that are needed.
      library_info_barrier = deps
    }
    sources = _full_source_paths + _full_stub_paths
  }

  # Generate library_info.json file with all the library dependencies info
  generated_file(_labels.library_infos) {
    forward_variables_from(invoker,
                           [
                             "assert_no_deps",
                             "testonly",
                           ])
    visibility = [ ":*" ]
    public_deps = [ ":${_labels.input_group}" ]
    outputs = [ _files.library_infos ]
    output_conversion = "json"
    data_keys = [ "library_info" ]
    walk_keys = [ "library_info_barrier" ]

    metadata = {
      library_info_barrier = public_deps
    }
  }

  validate_python_library(_labels.mypy_checker) {
    forward_variables_from(invoker,
                           [
                             "assert_no_deps",
                             "testonly",
                           ])
    visibility = [ ":${_labels.main_target}" ]

    library_infos = ":${_labels.library_infos}"

    # This source list includes only direct library sources and stubs, excluding
    # any dependencies.
    sources = _full_source_paths + _full_stub_paths

    # Required for generated sources like C extension wrappers.
    deps = library_deps
    if (defined(invoker.deps)) {
      deps += invoker.deps
    }
  }

  group(target_name) {
    forward_variables_from(invoker,
                           [
                             "assert_no_deps",
                             "testonly",
                             "visibility",
                             "data_deps",
                           ])
    deps = [ ":${_labels.input_group}" ]
    if (_enable_mypy) {
      # Run python type checks using Mypy if enable_mypy flag is set.
      validations = [ ":${_labels.mypy_checker}" ]
    }
    metadata = {
      # Ensure validation dependencies are excluded from metadata walk!
      # TODO(https://fxbug.dev/517150685): Remove this once new GN binary has rolled
      library_info_barrier = deps
    }
  }
}