# Copyright 2020 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Script generating a wrapper API for LibUV.

Note: This scriptis highly specific to LibUV's source code and does not
generalize to any other library
"""

import os
import re
import sys
from typing import List


def get_var_type(string: str) -> str:
  """Gets the type from an argument variable.

  Args:
    string: Input variable declaration

  Returns:
    The type of the argument variable as a string, e.g. "int x" -> "int".
  """

  var = string.strip()

  # Unnamed variable
  if var in ("void", "...") or var[-1] == "*":
    return var

  return " ".join(var.split(" ")[:-1]).strip()


def get_var_name(string: str) -> str:
  """Gets the name from an argument variable.

  Args:
    string: Input variable declaration

  Returns:
    The name of the arguments variable as a string, e.g. "int x" -> "x".
  """

  var = string.strip()

  # Not an actual variable
  if var in ("void", "..."):
    return ""

  # Unnamed variable, use an arbitrary name
  if var[-1] == "*":
    return var.split("_")[1]

  return var.split(" ")[-1].strip()


def fix_method_type(string: str) -> str:
  """Fixes the method type.

  Args:
    string: A parameter type declaration

  Returns:
    A fixed up string replacing pointers to concrete types with pointers to
    void, e.g. "const int*" -> "const void*".
  """

  method_type = string.strip()

  # Const pointer
  if "*" in method_type and "const" in method_type:
    return "const void*"

  # Regular pointer
  if "*" in method_type:
    return "void*"

  # Not a pointer
  return method_type


def fix_argument(string: str) -> str:
  """Fixes an argument.

  Args:
    string: An argument type to fix

  Returns:
    The fixed up argument as a string, e.g. "const int* x" -> "const void* x".
  """

  arg_type = get_var_type(string)
  arg_name = get_var_name(string)

  # Array argument, becomes a pointer
  if "[" in arg_name:
    arg_type += "*"
    arg_name = arg_name.split("[")[0] + arg_name.split("]")[-1]

  # Pointer (in LibUV, types endind in "_cb" or "_func" are pointers)
  if "*" in arg_type or "_cb" in arg_type or "_func" in arg_type:
    if "const" in arg_type:
      return "const void* " + arg_name
    return "void* " + arg_name

  # Not a pointer
  return arg_type + " " + arg_name


def fix_call_argument(string: str) -> str:
  """Fixes an argument in a call the orignal method.

  Args:
    string: A method call argument

  Returns:
    The fixed call argument, e.g. "const int* x" ->
    "reinterpret_cast<const int*>(x)".
  """

  arg_type = get_var_type(string)
  arg_name = get_var_name(string)

  # Array argument, becomes a pointer
  if "[" in arg_name:
    arg_type += "*"
    arg_name = arg_name.split("[")[0] + arg_name.split("]")[-1]

  # Pointer (in LibUV, types endind in "_cb" or "_func" are pointers)
  if "*" in arg_type or "_cb" in arg_type or "_func" in arg_type:
    return "reinterpret_cast<" + arg_type + ">(" + arg_name + ")"

  # Not a pointer
  return arg_name


def read_file(filename: str) -> str:
  """Returns contents of filename as a string.

  Args:
    filename: The name of the file to read

  Returns:
    The contents of the file as a string.
  """

  file = open(filename, "r")
  return str(file.read())


def clean_file(text: str) -> str:
  """Prepares the file for parsing.

  In particular, removes comments and macros from text
  Additionally, moves pointer asterisks next to its type

  Args:
    text: The contents of the text file to prepare

  Returns:
    The cleaned up file contents.
  """

  result = text
  result = re.sub(r"//.*?\n", "", result, flags=re.S)
  result = re.sub(r"/\*.*?\*/", "", result, flags=re.S)
  result = re.sub(r"#.*?\n", "", result, flags=re.S)
  result = result.replace(" *", "* ")
  return result


def get_signatures(text: str) -> str:
  """Gets the signatures of all the methods in the header.

  Note: This method only works on a certain version of LibUV's header.

  Args:
    text: The contents of the header file

  Returns:
    The extracted method signatures.
  """

  signatures = [x.split(";")[0].strip() for x in text.split("UV_EXTERN")[1:]]
  method_types = [
      " ".join(s.split("(")[0].split(" ")[:-1]).strip() for s in signatures
  ]
  names = [s.split("(")[0].split(" ")[-1].strip() for s in signatures]
  arguments = [s.split("(")[1][:-1] for s in signatures]
  arguments_lists = [[x.strip() for x in a.split(",")] for a in arguments]
  return zip(method_types, names, arguments_lists)


def append_method(method_type: str, name: str, arguments_list: List[str],
                  header: List[str], source: List[str]) -> None:
  """Writes the method to the header and the source list of lines.

  Args:
    method_type: The return type of the method as a string
    name: The name of the method
    arguments_list: A list of method aruments
    header: A list that receives method wrapper declarations
    source: A list that receives the declarations of the method wrappers
  """

  header.append(
      fix_method_type(method_type) + " sapi_" + name + "(" +
      ", ".join(map(fix_argument, arguments_list)) + ");")
  source.append(
      fix_method_type(method_type) + " sapi_" + name + "(" +
      ", ".join(map(fix_argument, arguments_list)) + ") {\n" + "  return " +
      name + "(" + ", ".join(map(fix_call_argument, arguments_list)) + ");\n" +
      "}")


def append_text(text: str, file: List[str]) -> None:
  """Writes text to file list of lines.

  Useful for additional methods, includes, extern "C"...

  Args:
    text: The text to append to the file
    file: A list receiving file lines
  """

  file.append(text)


def generate_wrapper() -> None:
  """Generates the wrapper."""

  header_file = open(sys.argv[2], "w")
  source_file = open(sys.argv[3], "w")

  text = read_file(sys.argv[1])
  text = clean_file(text)
  signatures = get_signatures(text)

  header = []
  source = []

  append_text("#include <uv.h>", header)
  append_text("#include <cstddef>", header)
  append_text("extern \"C\" {", header)
  append_text("#include \"" + os.path.abspath(header_file.name) + "\"", source)

  for (method_type, name, arguments_list) in signatures:
    # These wrapper methods are manually added at the end
    if name in ("uv_once", "uv_loop_configure"):
      continue
    append_method(method_type, name, arguments_list, header, source)

  # Add sapi_uv_once (uv_once uses a differnet kind of callback)
  append_text("void sapi_uv_once(void* guard, void (*callback)(void));", header)
  append_text(
      "void sapi_uv_once(void* guard, void (*callback)(void)) {\n" +
      "  return uv_once(reinterpret_cast<uv_once_t*>(guard)," + "callback);\n" +
      "}", source)

  # Add sapi_uv_loop_configure (uv_loop_configure is variadic)
  append_text(
      "int sapi_uv_loop_configure(void* loop, uv_loop_option option)" + ";",
      header)
  append_text(
      "int sapi_uv_loop_configure(void* loop, uv_loop_option option)" +
      " {\n  return uv_loop_configure(" +
      "reinterpret_cast<uv_loop_t*>(loop), option);\n" + "}", source)

  # Add sapi_uv_loop_configure_int (uv_loop_configure is variadic)
  append_text(
      "int sapi_uv_loop_configure_int(void* loop, " +
      "uv_loop_option option, int ap);", header)
  append_text(
      "int sapi_uv_loop_configure_int(void* loop, " +
      "uv_loop_option option, int ap) {\n" + "  return uv_loop_configure(" +
      "reinterpret_cast<uv_loop_t*>(loop), option, ap);\n}", source)

  append_text("}  // extern \"C\"\n", header)

  header_file.write("\n\n".join(header))
  source_file.write("\n\n".join(source))


generate_wrapper()