# coding=utf-8
# 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
#
#      http://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.
"""Library functions for IR extraction."""

import os
import pathlib
import re
import shutil
import subprocess
import multiprocessing
import functools
import json

from typing import Dict, List, Optional

from absl import logging

from compiler_opt.rl import constant


# TODO(ml-compiler-opt): maybe we can also convert here the cmdline file,from a
# \0 - separated list of strings, to a \n one.
def should_include_module(cmdline: str, match_regexp: Optional[str]) -> bool:
  """Determine if the module should be included."""
  if match_regexp is None:
    return True
  lines = cmdline.split('\0')
  return any(len(re.findall(match_regexp, l)) for l in lines)


def get_thinlto_index(cmdline: str, basedir: str) -> Optional[str]:
  opts = cmdline.split('\0')
  for option in opts:
    if option.startswith('-fthinlto-index'):
      return os.path.join(basedir, option.split('=')[1])
  return None


class TrainingIRExtractor:
  """IR and command line extraction from an object file."""

  def __init__(self, obj_relative_path, output_base_dir, obj_base_dir=None):
    """Set up a TrainingIRExtractor.

    Args:
      obj_relative_path: relative path to the input object file. It will be also
        used to construct the absolute path of the output IR and cmd files, by
        appending it to output_base_dir.
      output_base_dir: the directory under which the output will be produced.
      obj_base_dir: the base directory for all the input object files.
    """
    self._obj_relative_path = obj_relative_path
    self._output_base_dir = output_base_dir
    self._obj_base_dir = obj_base_dir if obj_base_dir is not None else ''

  def obj_base_dir(self):
    return self._obj_base_dir

  def output_base_dir(self):
    return self._output_base_dir

  def relative_output_path(self):
    return self._obj_relative_path

  def input_obj(self):
    return os.path.join(self.obj_base_dir(), self._obj_relative_path)

  def lld_src_bc(self):
    # .3.import.bc is the suffix attached to post-merge-pre-opt ('postimport')
    # IR bitcode saved by lld. It is hardcoded into lld.
    return os.path.join(self._obj_base_dir,
                        self._obj_relative_path + '.3.import.bc')

  def lld_src_thinlto(self):
    return os.path.join(self._obj_base_dir,
                        self._obj_relative_path + '.thinlto.bc')

  def dest_dir(self):
    return os.path.join(self.output_base_dir(),
                        os.path.dirname(self._obj_relative_path))

  def module_name(self):
    return os.path.basename(self._obj_relative_path)

  def cmd_file(self):
    return os.path.join(self.dest_dir(), self.module_name() + '.cmd')

  def bc_file(self):
    return os.path.join(self.dest_dir(), self.module_name() + '.bc')

  def thinlto_index_file(self):
    return os.path.join(self.dest_dir(), self.module_name() + '.thinlto.bc')

  def _get_extraction_cmd_command(self, llvm_objcopy_path: str,
                                  cmd_section_name: str):
    """Get llvm-objcopy and process args to a produce a command string that,
    when invoked, will extract the cmd section info ths self.cmd_file() file.
    """
    return [
        llvm_objcopy_path,
        '--dump-section=' + cmd_section_name + '=' + self.cmd_file(),
        self.input_obj(), '/dev/null'
    ]

  def _get_extraction_bc_command(self, llvm_objcopy_path: str,
                                 bitcode_section_name: str):
    """Gets llvm-objcopy and process args to produce a command string that,
    when invoked, will extract the bitcode section into the self.bc_file()
    file.
    """
    return [
        llvm_objcopy_path,
        '--dump-section=' + bitcode_section_name + '=' + self.bc_file(),
        self.input_obj(), '/dev/null'
    ]

  def _extract_clang_artifacts(self, llvm_objcopy_path: str, cmd_filter: str,
                               is_thinlto: bool, cmd_section_name: str,
                               bitcode_section_name: str) -> Optional[str]:
    """Run llvm-objcopy to extract the .bc and command line."""
    if not os.path.exists(self.input_obj()):
      logging.info('%s does not exist.', self.input_obj())
      return None
    os.makedirs(self.dest_dir(), exist_ok=True)
    try:
      subprocess.run(
          self._get_extraction_cmd_command(llvm_objcopy_path, cmd_section_name),
          check=True)
      if cmd_filter is not None or is_thinlto:
        with open(self.cmd_file(), encoding='utf-8') as f:
          lines = f.readlines()
        assert len(lines) == 1
        cmdline = lines[0]
        if not should_include_module(cmdline, cmd_filter):
          logging.info(
              'Excluding module %s because it does not match the filter',
              self.input_obj())
          os.remove(self.cmd_file())
          return None
        if is_thinlto:
          index_file = get_thinlto_index(cmdline, self.obj_base_dir())
          shutil.copy(index_file, self.thinlto_index_file())

      subprocess.run(
          self._get_extraction_bc_command(llvm_objcopy_path,
                                          bitcode_section_name),
          check=True)
    except subprocess.CalledProcessError as e:
      # This may happen if  .o file was build from asm (.S source).
      logging.warning('%s was not processed: %s', self.input_obj(), e)
      return None
    assert (os.path.exists(self.cmd_file()) and
            os.path.exists(self.bc_file()) and
            (not is_thinlto or os.path.exists(self.thinlto_index_file())))
    return self.relative_output_path()

  def _extract_lld_artifacts(self) -> Optional[str]:
    """Extract the .bc file with ThinLTO index from an lld ThinLTO invocation.
    """
    if not os.path.exists(self.lld_src_bc()):
      logging.info('%s does not exist.', self.lld_src_bc())
      return None
    if not os.path.exists(self.lld_src_thinlto()):
      logging.info('%s does not exist.', self.lld_src_thinlto())
      return None
    os.makedirs(self.dest_dir(), exist_ok=True)

    # Copy over the files
    shutil.copy(self.lld_src_bc(), self.bc_file())
    shutil.copy(self.lld_src_thinlto(), self.thinlto_index_file())

    assert os.path.exists(self.bc_file())
    assert os.path.exists(self.thinlto_index_file())
    return self._obj_relative_path

  def extract(self,
              llvm_objcopy_path: Optional[str] = None,
              cmd_filter: Optional[str] = None,
              thinlto_build: Optional[str] = None,
              cmd_section_name: Optional[str] = '.llvmcmd',
              bitcode_section_name: Optional[str] = '.llvmbc') -> Optional[str]:
    if thinlto_build == 'local':
      return self._extract_lld_artifacts()
    return self._extract_clang_artifacts(
        llvm_objcopy_path=llvm_objcopy_path,
        cmd_filter=cmd_filter,
        is_thinlto=thinlto_build == 'distributed',
        cmd_section_name=cmd_section_name,
        bitcode_section_name=bitcode_section_name)


def convert_compile_command_to_objectfile(
    command: Dict[str, str], output_dir: str) -> Optional[TrainingIRExtractor]:
  obj_base_dir = command['directory']
  cmd = command['command']

  cmd_parts = cmd.split()
  try:
    obj_index = cmd_parts.index('-o') + 1
  except ValueError:
    # This could happen if there are non-clang commands in compile_commands.json
    logging.info('Command has no -o option: %s', cmd)
    return None
  obj_rel_path = cmd_parts[obj_index]
  # TODO(mtrofin): is the obj_base_dir correct for thinlto index bc files?
  return TrainingIRExtractor(
      obj_relative_path=obj_rel_path,
      output_base_dir=output_dir,
      obj_base_dir=obj_base_dir)


def load_from_compile_commands(json_array: List[Dict[str, str]],
                               output_dir: str) -> List[TrainingIRExtractor]:
  objs = [
      convert_compile_command_to_objectfile(cmd, output_dir)
      for cmd in json_array
  ]
  # Filter out None, in case there were non-clang commands in the .json
  return [obj for obj in objs if obj is not None]


def load_from_lld_params(params_array: List[str], obj_base_dir: str,
                         output_dir: str) -> List[TrainingIRExtractor]:
  """Create an ObjectFile array based on lld's parameters."""
  # yank out -o and the output. After that, anything not starting with '-', and
  # ending in a '.o', is an object file.
  try:
    minus_o_idx = params_array.index('-o')
    del params_array[minus_o_idx:minus_o_idx + 2]
    just_obj_paths = [
        o for o in params_array if not o.startswith('-') and o.endswith('.o')
    ]
  except ValueError:
    logging.info('This params file does not have an explicit -o option.')
    just_obj_paths = params_array

  def make_obj(obj_file: str) -> TrainingIRExtractor:
    return TrainingIRExtractor(
        obj_relative_path=obj_file,
        output_base_dir=output_dir,
        obj_base_dir=obj_base_dir)

  return [make_obj(obj_file) for obj_file in just_obj_paths]


def load_from_directory(obj_base_dir: str,
                        output_dir: str) -> List[TrainingIRExtractor]:
  """Create an object file array by globbing an entire drectory.

  Args:
    obj_base_dir: The base build directory that all object files will be
      written out as being relative to.
    output_dir: The output directory where extracted .bc and .cmd files should
      be placed.
  """
  paths = [str(p) for p in pathlib.Path(obj_base_dir).glob('**/*.o')]

  def make_spec(obj_file: str):
    return TrainingIRExtractor(
        obj_relative_path=os.path.relpath(obj_file, start=obj_base_dir),
        output_base_dir=output_dir,
        obj_base_dir=obj_base_dir)

  return [make_spec(path) for path in paths]


def load_for_lld_thinlto(obj_base_dir: str,
                         output_dir: str) -> List[TrainingIRExtractor]:
  # .3.import.bc is the suffix attached to post-merge-pre-opt ('postimport')
  # IR bitcode saved by lld. It is hardcoded into lld. ThinLTO index files
  # are also emitted next to the postimport bitcode, with the suffix
  # .thinlto.bc instead
  paths = [str(p) for p in pathlib.Path(obj_base_dir).glob('**/*.3.import.bc')]

  def make_spec(obj_file: str):
    return TrainingIRExtractor(
        # Cut away .3.import.bc
        obj_relative_path=os.path.relpath(obj_file, start=obj_base_dir)[:-12],
        output_base_dir=output_dir,
        obj_base_dir=obj_base_dir)

  return [make_spec(path) for path in paths]


def run_extraction(objs: List[TrainingIRExtractor], num_workers: int,
                   llvm_objcopy_path: str, cmd_filter: str, thinlto_build: str,
                   cmd_section_name: str, bitcode_section_name: str):
  """Extracts all specified object files into the corpus directory.

  Args:
    objs: A list of TrainingIRExtractor Objects that represent the object files
      to extract bitcode/commands from.
    num_workers: The number of parallel processes to spawn to run the
      extraction.
    llvm_objcopy_path: The path to the llvm-objcopy to use for dumping sections.
    cmd_filter: A regular expression that is used to select for compilations
      performed with specific flags. If you want to include all compilations,
      set this to None.
    thinlto_build: Whether or not this is a ThinLTO build, and if so, the type.
      Set this to None if the build was not done with ThinLTO.
    cmd_section_name: The name of the command line section created by the
      bitcode embedding.
    bitcode_section_name: The name of the bitcode section created by the
      bitcode embedding.
  """
  extract_artifacts = functools.partial(
      TrainingIRExtractor.extract,
      llvm_objcopy_path=llvm_objcopy_path,
      cmd_filter=cmd_filter,
      thinlto_build=thinlto_build,
      cmd_section_name=cmd_section_name,
      bitcode_section_name=bitcode_section_name)

  with multiprocessing.Pool(num_workers) as pool:
    relative_output_paths = pool.map(extract_artifacts, objs)
    pool.close()
    pool.join()
  return relative_output_paths


def write_corpus_manifest(thinlto_build: str, relative_output_paths: List[str],
                          output_dir: str):
  """Writes a corpus_manifest.json containing all necessary information about
  the corpus.

  Args:
    thinlto_build: Whether or not the build was done with ThinLTO and if so,
      what kind of ThinLTO. Set this to none if the build was not performed with
      ThinLTO.
    relative_output_paths: The relative (to the corpus directory) output paths
      of all the bitcode files that should be placed in the corpus manifest
    output_dir: The corpus directory where the corpus manifest should be
      placed.
  """
  # This comes first rather than later so global_command_override is at the top
  # of the .json after being written
  if thinlto_build == 'local':
    corpus_description = {
        'global_command_override': constant.UNSPECIFIED_OVERRIDE
    }
  else:
    corpus_description = {}

  corpus_description.update({
      'has_thinlto': thinlto_build is not None,
      'modules': [path for path in relative_output_paths if path is not None]
  })

  with open(
      os.path.join(output_dir, 'corpus_description.json'),
      'w',
      encoding='utf-8') as f:
    json.dump(corpus_description, f, indent=2)
