#!/usr/bin/env python
# Copyright 2013 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""The frontend for the Mojo bindings system."""


import argparse
import hashlib
import importlib.util
import json
import os
import re
import struct
import sys

# Disable lint check for finding modules:
# pylint: disable=F0401

def _GetDirAbove(dirname):
  """Returns the directory "above" this file containing |dirname| (which must
  also be "above" this file)."""
  path = os.path.abspath(__file__)
  while True:
    path, tail = os.path.split(path)
    assert tail
    if tail == dirname:
      return path

# Manually check for the command-line flag. (This isn't quite right, since it
# ignores, e.g., "--", but it's close enough.)
if "--use_bundled_pylibs" in sys.argv[1:]:
  sys.path.insert(0, os.path.join(_GetDirAbove("components"), "third_party"))

sys.path.insert(0, os.path.join(_GetDirAbove("components"),
                                "mojo", "public", "tools", "mojom"))

# pylint: disable=wrong-import-position
from mojom.error import Error
import mojom.fileutil as fileutil
from mojom.generate import translate
from mojom.generate import template_expander
from mojom.generate.generator import AddComputedData
from mojom.parse.parser import Parse
# pylint: enable=wrong-import-position

# pylint: disable=useless-object-inheritance


_BUILTIN_GENERATORS = {
  "c": "cronet_c_generator.py",
}


def LoadGenerators(generators_string):
  if not generators_string:
    return []  # No generators.

  script_dir = os.path.dirname(os.path.abspath(__file__))
  generators = {}
  for generator_name in [s.strip() for s in generators_string.split(",")]:
    language = generator_name.lower()
    if language in _BUILTIN_GENERATORS:
      generator_name = os.path.join(script_dir,
                                    _BUILTIN_GENERATORS[language])
    else:
      print("Unknown generator name %s" % generator_name)
      sys.exit(1)
    spec = importlib.util.spec_from_file_location(
        os.path.basename(generator_name)[:-3], generator_name)
    generator_module = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(generator_module)
    generators[language] = generator_module
  return generators


def MakeImportStackMessage(imported_filename_stack):
  """Make a (human-readable) message listing a chain of imports. (Returned
  string begins with a newline (if nonempty) and does not end with one.)"""
  return ''.join(
      reversed(["\n  %s was imported by %s" % (a, b) for (a, b) in \
                    zip(imported_filename_stack[1:], imported_filename_stack)]))


class RelativePath(object):
  """Represents a path relative to the source tree."""
  def __init__(self, path, source_root):
    self.path = path
    self.source_root = source_root

  def relative_path(self):
    return os.path.relpath(os.path.abspath(self.path),
                           os.path.abspath(self.source_root))


def FindImportFile(rel_dir, file_name, search_rel_dirs):
  """Finds |file_name| in either |rel_dir| or |search_rel_dirs|. Returns a
  RelativePath with first file found, or an arbitrary non-existent file
  otherwise."""
  for rel_search_dir in [rel_dir] + search_rel_dirs:
    path = os.path.join(rel_search_dir.path, file_name)
    if os.path.isfile(path):
      return RelativePath(path, rel_search_dir.source_root)
  return RelativePath(os.path.join(rel_dir.path, file_name),
                      rel_dir.source_root)


def ScrambleMethodOrdinals(interfaces, salt):
  already_generated = set()
  for interface in interfaces:
    i = 0
    already_generated.clear()
    for method in interface.methods:
      while True:
        i = i + 1
        if i == 1000000:
          raise Exception("Could not generate %d method ordinals for %s" %
              (len(interface.methods), interface.mojom_name))
        # Generate a scrambled method.ordinal value. The algorithm doesn't have
        # to be very strong, cryptographically. It just needs to be non-trivial
        # to guess the results without the secret salt, in order to make it
        # harder for a compromised process to send fake Mojo messages.
        sha256 = hashlib.sha256(salt)
        sha256.update(interface.mojom_name)
        sha256.update(str(i))
        # Take the first 4 bytes as a little-endian uint32.
        ordinal = struct.unpack('<L', sha256.digest()[:4])[0]
        # Trim to 31 bits, so it always fits into a Java (signed) int.
        ordinal = ordinal & 0x7fffffff
        if ordinal in already_generated:
          continue
        already_generated.add(ordinal)
        method.ordinal = ordinal
        method.ordinal_comment = (
            'The %s value is based on sha256(salt + "%s%d").' %
            (ordinal, interface.mojom_name, i))
        break


def ReadFileContents(filename):
  with open(filename, 'rb') as f:
    return f.read()


class MojomProcessor(object):
  """Parses mojom files and creates ASTs for them.

  Attributes:
    _processed_files: {Dict[str, mojom.generate.module.Module]} Mapping from
        relative mojom filename paths to the module AST for that mojom file.
  """
  def __init__(self, should_generate):
    self._should_generate = should_generate
    self._processed_files = {}
    self._parsed_files = {}
    self._typemap = {}

  def LoadTypemaps(self, typemaps):
    # Support some very simple single-line comments in typemap JSON.
    comment_expr = r"^\s*//.*$"
    def no_comments(line):
      return not re.match(comment_expr, line)
    for filename in typemaps:
      with open(filename) as f:
        typemaps = json.loads("".join([l for l in f.readlines()
                                       if no_comments(l)]))
        for language, typemap in typemaps.items():
          language_map = self._typemap.get(language, {})
          language_map.update(typemap)
          self._typemap[language] = language_map

  def ProcessFile(self, args, remaining_args, generator_modules, filename):
    self._ParseFileAndImports(RelativePath(filename, args.depth),
                              args.import_directories, [])

    return self._GenerateModule(args, remaining_args, generator_modules,
        RelativePath(filename, args.depth))

  def _GenerateModule(self, args, remaining_args, generator_modules,
                      rel_filename):
    # Return the already-generated module.
    if rel_filename.path in self._processed_files:
      return self._processed_files[rel_filename.path]
    tree = self._parsed_files[rel_filename.path]

    dirname = os.path.dirname(rel_filename.path)

    # Process all our imports first and collect the module object for each.
    # We use these to generate proper type info.
    imports = {}
    for parsed_imp in tree.import_list:
      rel_import_file = FindImportFile(
          RelativePath(dirname, rel_filename.source_root),
          parsed_imp.import_filename, args.import_directories)
      imports[parsed_imp.import_filename] = self._GenerateModule(
          args, remaining_args, generator_modules, rel_import_file)

    # Set the module path as relative to the source root.
    # Normalize to unix-style path here to keep the generators simpler.
    module_path = rel_filename.relative_path().replace('\\', '/')

    module = translate.OrderedModule(tree, module_path, imports)

    if args.scrambled_message_id_salt_paths:
      salt = ''.join(
          [ReadFileContents(f) for f in args.scrambled_message_id_salt_paths])
      ScrambleMethodOrdinals(module.interfaces, salt)

    if self._should_generate(rel_filename.path):
      AddComputedData(module)
      for language, generator_module in generator_modules.items():
        generator = generator_module.Generator(
            module, args.output_dir, typemap=self._typemap.get(language, {}),
            variant=args.variant, bytecode_path=args.bytecode_path,
            for_blink=args.for_blink,
            export_attribute=args.export_attribute,
            export_header=args.export_header,
            generate_non_variant_code=args.generate_non_variant_code)
        filtered_args = []
        if hasattr(generator_module, 'GENERATOR_PREFIX'):
          prefix = '--' + generator_module.GENERATOR_PREFIX + '_'
          filtered_args = [arg for arg in remaining_args
                           if arg.startswith(prefix)]
        generator.GenerateFiles(filtered_args)

    # Save result.
    self._processed_files[rel_filename.path] = module
    return module

  def _ParseFileAndImports(self, rel_filename, import_directories,
      imported_filename_stack):
    # Ignore already-parsed files.
    if rel_filename.path in self._parsed_files:
      return

    if rel_filename.path in imported_filename_stack:
      print("%s: Error: Circular dependency" % rel_filename.path + \
          MakeImportStackMessage(imported_filename_stack + [rel_filename.path]))
      sys.exit(1)

    try:
      with open(rel_filename.path) as f:
        source = f.read()
    except IOError as e:
      print("%s: Error: %s" % (rel_filename.path, e.strerror) + \
          MakeImportStackMessage(imported_filename_stack + [rel_filename.path]))
      sys.exit(1)

    try:
      tree = Parse(source, rel_filename.path)
    except Error as e:
      full_stack = imported_filename_stack + [rel_filename.path]
      print(str(e) + MakeImportStackMessage(full_stack))
      sys.exit(1)

    dirname = os.path.split(rel_filename.path)[0]
    for imp_entry in tree.import_list:
      import_file_entry = FindImportFile(
          RelativePath(dirname, rel_filename.source_root),
          imp_entry.import_filename, import_directories)
      self._ParseFileAndImports(import_file_entry, import_directories,
          imported_filename_stack + [rel_filename.path])

    self._parsed_files[rel_filename.path] = tree


def _Generate(args, remaining_args):
  if args.variant == "none":
    args.variant = None

  for idx, import_dir in enumerate(args.import_directories):
    tokens = import_dir.split(":")
    if len(tokens) >= 2:
      args.import_directories[idx] = RelativePath(tokens[0], tokens[1])
    else:
      args.import_directories[idx] = RelativePath(tokens[0], args.depth)
  generator_modules = LoadGenerators(args.generators_string)

  fileutil.EnsureDirectoryExists(args.output_dir)

  processor = MojomProcessor(lambda filename: filename in args.filename)
  processor.LoadTypemaps(set(args.typemaps))
  for filename in args.filename:
    processor.ProcessFile(args, remaining_args, generator_modules, filename)
  if args.depfile:
    assert args.depfile_target
    with open(args.depfile, 'w') as f:
      f.write('%s: %s' % (
          args.depfile_target,
          ' '.join(list(processor._parsed_files.keys()))))

  return 0


def _Precompile(args, _):
  generator_modules = LoadGenerators(",".join(list(_BUILTIN_GENERATORS.keys())))

  template_expander.PrecompileTemplates(generator_modules, args.output_dir)
  return 0



def main():
  parser = argparse.ArgumentParser(
      description="Generate bindings from mojom files.")
  parser.add_argument("--use_bundled_pylibs", action="store_true",
                      help="use Python modules bundled in the SDK")

  subparsers = parser.add_subparsers()
  generate_parser = subparsers.add_parser(
      "generate", description="Generate bindings from mojom files.")
  generate_parser.add_argument("filename", nargs="+",
                               help="mojom input file")
  generate_parser.add_argument("-d", "--depth", dest="depth", default=".",
                               help="depth from source root")
  generate_parser.add_argument("-o", "--output_dir", dest="output_dir",
                               default=".",
                               help="output directory for generated files")
  generate_parser.add_argument("-g", "--generators",
                               dest="generators_string",
                               metavar="GENERATORS",
                               default="c++,javascript,java",
                               help="comma-separated list of generators")
  generate_parser.add_argument(
      "-I", dest="import_directories", action="append", metavar="directory",
      default=[],
      help="add a directory to be searched for import files. The depth from "
           "source root can be specified for each import by appending it after "
           "a colon")
  generate_parser.add_argument("--typemap", action="append", metavar="TYPEMAP",
                               default=[], dest="typemaps",
                               help="apply TYPEMAP to generated output")
  generate_parser.add_argument("--variant", dest="variant", default=None,
                               help="output a named variant of the bindings")
  generate_parser.add_argument(
      "--bytecode_path", required=True, help=(
          "the path from which to load template bytecode; to generate template "
          "bytecode, run %s precompile BYTECODE_PATH" % os.path.basename(
              sys.argv[0])))
  generate_parser.add_argument("--for_blink", action="store_true",
                               help="Use WTF types as generated types for mojo "
                               "string/array/map.")
  generate_parser.add_argument(
      "--export_attribute", default="",
      help="Optional attribute to specify on class declaration to export it "
      "for the component build.")
  generate_parser.add_argument(
      "--export_header", default="",
      help="Optional header to include in the generated headers to support the "
      "component build.")
  generate_parser.add_argument(
      "--generate_non_variant_code", action="store_true",
      help="Generate code that is shared by different variants.")
  generate_parser.add_argument(
      "--depfile",
      help="A file into which the list of input files will be written.")
  generate_parser.add_argument(
      "--depfile_target",
      help="The target name to use in the depfile.")
  generate_parser.add_argument(
      "--scrambled_message_id_salt_path",
      dest="scrambled_message_id_salt_paths",
      help="If non-empty, the path to a file whose contents should be used as"
      "a salt for generating scrambled message IDs. If this switch is specified"
      "more than once, the contents of all salt files are concatenated to form"
      "the salt value.", default=[], action="append")
  generate_parser.set_defaults(func=_Generate)

  precompile_parser = subparsers.add_parser("precompile",
      description="Precompile templates for the mojom bindings generator.")
  precompile_parser.add_argument(
      "-o", "--output_dir", dest="output_dir", default=".",
      help="output directory for precompiled templates")
  precompile_parser.set_defaults(func=_Precompile)

  args, remaining_args = parser.parse_known_args()
  return args.func(args, remaining_args)


if __name__ == "__main__":
  sys.exit(main())