# Copyright 2019 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("$zx/public/gn/fidl/fidlc.gni")

# List of FIDL support modules.  Each of these defines its own version of
# $fidl_support_fidlc and $fidl_support_templates.
#
# $fidl_support_templates:
# Type: list of scopes
#
#   import
#     Required: Source-absolute path to the .gni file that defines $target.
#     Type: file
#
#   target
#     Required: Name of a template to invoke, defined in the $import file.
#     Type: string
#
#   fidlc
#     Optional: Name of an entry in $fidl_support_fidlc describing fidlc
#     outputs that this template requires.
#
# The $target template is invoked with the $target_name from fidl_library()
# and these parameters:
#
#   fidl_deps
#     Required: $public_deps list from fidl_library() after canonicalization.
#     Type: list(label_no_toolchain)
#
#   fidl_name
#     Required: The FIDL library name (with dots).
#     Type: string
#
#   fidl_path
#     Required: $fidl_name with each `.` replaced by a `/`.
#     Type: string
#
#   fidl_gen_dir
#     Optional: If $fidlc was set, this is the directory in which those
#     fidlc outputs went.  e.g. "$fidl_gen_dir/include" might be useful.
#     Type: file
#
#   fidlc_outputs
#     Optional: If $fidlc was set, this is the list of output files generated
#     by fidlc for that entry in $fidl_support_fidlc.
#
#   fidlc_deps
#     Optional: If $fidlc was set, this is the label to include in $deps
#     of something using $fidlc_outputs.
#
#   visibility, testonly
#     Optional: Forwarded from fidl_library().
#
# $fidl_support_fidlc:
# Type: list of scopes
#
#   name
#     Required: Name for this collection of fidlc output
#     Type: string
#
#   files
#     Required: A list of scopes describing outputs from fidlc.
#     Type: list of scopes
#       switch
#         Required: fidlc command-line switch preceding output file name.
#         Type: string
#       path
#         Optional: Required unless $path_prefix and $path_suffix are given.
#         The fidlc output file is "$fidl_gen_dir/$path".
#         Type: string
#       path_prefix, path_suffix
#         Optional: If one is specified, both must be and $path must not be.
#         The output file is "$fidl_gen_dir/$path_prefix$fidl_path$path_suffix".
#         Type: string
#
# All these kinds of output will be generated in one run of fidlc.  Modules
# should use the $fidl_support_fidlc list only for generation work that is
# more or less free once you're running fidlc anyway.  These output files
# will be generated if *any* $fidl_support_fidlc output file from *any*
# support module is needed in the build.  For more costly generation steps
# (or ones requiring more than a simple fidlc command-line switch), support
# modules should use $fidl_support_templates.
#
# TODO(mcgrathr): Add more language generators.  For language support from
# a different petal, add a build argument to contribute to this list via
# default_overrides.
fidl_support = [ "$zx/public/gn/fidl/c.gni" ]

# Each support module defines $fidl_support_fidlc and
# $fidl_support_templates lists in its .gni file.
_fidl_generators = []
foreach(module, fidl_support) {
  _fidl_generators += [
    {
      import(module)
    },
  ]
}

# Collect all fidlc outputs from the support modules, and deduplicate.
# Collect all the generation templates to invoke, and deduplicate.  All
# these templates will be invoked by fidl_library() to define their targets.
_fidl_gen_fidlc = []
_fidl_gen_templates = []
foreach(gen, _fidl_generators) {
  _fidl_gen_fidlc += gen.fidl_support_fidlc
  _fidl_gen_fidlc -= gen.fidl_support_fidlc
  _fidl_gen_fidlc += gen.fidl_support_fidlc
  _fidl_gen_templates += gen.fidl_support_templates
  _fidl_gen_templates -= gen.fidl_support_templates
  _fidl_gen_templates += gen.fidl_support_templates
}

# Define a FIDL library and implicitly generate bindings targets.
#
# The $fidl_support global determines what targets this actually produces.
#
# Parameters
#
#   sources
#     Required: List of `.fidl` source files.
#
#   deps
#     Optional: This is *not* the way to express dependencies on other FIDL
#     libraries.  Use $public_deps for that.  The only use for $deps is if
#     some of $sources are generated, to depend on the targets generating them.
#     Type: list(label)
#
#   public_deps
#     Optional: Other fidl_library() targets this library depends on.
#     If `using foo;` appears in a $sources file, then the label of the
#     fidl_library() target should be listed here.  This must list only
#     other fidl_library() targets and may not use a "(toolchain)" suffix.
#     Type: list(label_no_toolchain)
#
template("fidl_library") {
  assert(defined(invoker.sources),
         "fidl_library(\"$target_name\") must set `sources`")

  fidl_target = target_name

  # TODO(mcgrathr): temporary until everything is renamed with . names
  fidl_name = string_replace(fidl_target, "-", ".")
  fidl_path = string_replace(fidl_name, ".", "/")

  # Collect the dependencies on other FIDL libraries, and canonicalize them.
  fidl_library_deps = []
  if (defined(invoker.public_deps)) {
    foreach(label, invoker.public_deps) {
      assert(get_label_info(label, "toolchain") == current_toolchain,
             "fidl_library() `deps` must be fidl_library() target labels")
      fidl_library_deps += [ get_label_info(label, "label_no_toolchain") ]
    }
  }

  files_rspfile_target = "_fidl_library.files.$fidl_target.rsp"
  fidl_gen_dir =
      get_label_info(":$fidl_target($default_toolchain)", "target_gen_dir")
  files_rspfile = "$fidl_gen_dir/$fidl_target.rsp"

  gen_target = "_fidl_library.generate.$fidl_target"

  # This is the label to use in deps.
  files_rspfile_label = ":$files_rspfile_target($default_toolchain)"
  gen_target_label = ":$gen_target($default_toolchain)"

  gens = []
  foreach(gen, _fidl_gen_fidlc) {
    gen_dir = "$fidl_gen_dir/$fidl_target.${gen.name}"
    gen_outputs = []
    gen_args = []
    foreach(file, gen.files) {
      gen_args += [ file.switch ]
      if (defined(file.path)) {
        file = file.path
      } else {
        file = "${file.path_prefix}${fidl_path}${file.path_suffix}"
      }
      gen_outputs += [ "$gen_dir/$file" ]
      gen_args += [ rebase_path("$gen_dir/$file", root_build_dir) ]
    }
    gens += [
      {
        name = gen.name
        outputs = gen_outputs
        args = gen_args
      },
    ]
  }

  if (current_toolchain == default_toolchain) {
    # This just groups the dependencies together with the metadata listing
    # the input files.
    group(fidl_target) {
      forward_variables_from(invoker,
                             [
                               "deps",
                               "public_deps",
                               "visibility",
                               "testonly",
                             ])
      if (defined(visibility)) {
        visibility += [ ":$files_rspfile_target" ]
      }

      metadata = {
        # These inputs are needed both here and in every dependent library.
        # Each --files switch introduces a group of source files that make
        # up a single FIDL library (all have identical `library ...;` lines).
        fidl_rspfile =
            [ "--files" ] + rebase_path(invoker.sources, root_build_dir)
      }
    }

    # Produce a metadata response file from all the fidl_rspfile lists.
    # fidlc() uses this file.
    generated_file(files_rspfile_target) {
      forward_variables_from(invoker, [ "testonly" ])
      deps = [
        ":$fidl_target",
      ]
      outputs = [
        files_rspfile,
      ]
      output_conversion = "list lines"
      data_keys = [ "fidl_rspfile" ]
    }

    fidlc(gen_target) {
      visibility = [ ":*" ]
      forward_variables_from(invoker, [ "testonly" ])
      deps = [
        ":$fidl_target",
      ]
      outputs = []
      args = []
      foreach(gen, gens) {
        outputs += gen.outputs
        args += gen.args
      }
    }
  } else {
    not_needed(invoker, "*")
  }

  # Subroutine used in the _fidl_gen_templates loop in fidl_library().
  # The inner template provides a local scope for the import so it
  # won't clobber the outer template scope.
  template("_fidl_gen_subtarget") {
    import(invoker.import)
    target(invoker.target, target_name) {
      forward_variables_from(invoker.args, "*")
    }
  }

  # Invoke each template.
  foreach(gen, _fidl_gen_templates) {
    # The target_name for the template is the main FIDL target name.
    # The template will define its targets using appropriate suffixes.
    _fidl_gen_subtarget(fidl_target) {
      import = gen.import
      target = gen.target
      args = {
        forward_variables_from(invoker,
                               [
                                 "visibility",
                                 "testonly",
                               ])

        # The bindings-library template can map these to corresponding
        # bindings-library targets.
        fidl_deps = fidl_library_deps

        # Provide these for convenience.  They're derived from target_name
        # but every generator will be doing it the same way.
        fidl_name = fidl_name
        fidl_path = fidl_path

        # If the template uses our main fidlc run, give it details about that.
        if (defined(gen.fidlc)) {
          fidlc_gen_dir = "$fidl_gen_dir/$fidl_target.${gen.fidlc}"
          fidlc_deps = [ gen_target_label ]
          foreach(gen_fidlc, gens) {
            if (gen.fidlc == gen_fidlc.name) {
              fidlc_outputs = gen_fidlc.outputs
            }
          }
        }
      }
    }
  }
}