#!/usr/bin/env python

## @package thtml2doxy_clang
#  Translates THtml C++ comments to Doxygen using libclang as parser.
#
#  This code relies on Python bindings for libclang: libclang's interface is pretty unstable, and
#  its Python bindings are unstable as well.
#
#  AST (Abstract Source Tree) traversal is performed entirely using libclang used as a C++ parser,
#  instead of attempting to write a parser ourselves.
#
#  This code (expecially AST traversal) was inspired by:
#
#   - [Implementing a code generator with libclang](http://szelei.me/code-generator/)
#     (this refers to API calls used here)
#   - [Parsing C++ in Python with Clang](http://eli.thegreenplace.net/2011/07/03/parsing-c-in-python-with-clang)
#     (outdated, API calls described there do not work anymore, but useful to understand some basic
#     concepts)
#
#  Usage:
#
#    `thtml2doxy_clang file1 [file2 [file3...]]`
#
#  @author Dario Berzano <dario.berzano@cern.ch>
#  @date 2014-12-05


import sys
import os
import re
import logging
import getopt
import clang.cindex


## Brain-dead color output for terminal.
class Colt(str):

  def red(self):
    return self.color('\033[31m')

  def green(self):
    return self.color('\033[32m')

  def yellow(self):
    return self.color('\033[33m')

  def blue(self):
    return self.color('\033[34m')

  def magenta(self):
    return self.color('\033[35m')

  def cyan(self):
    return self.color('\033[36m')

  def color(self, c):
    return c + self + '\033[m'


## Comment.
class Comment:

  def __init__(self, lines, first_line, first_col, last_line, last_col, indent, func):
    self.lines = lines
    self.first_line = first_line
    self.first_col = first_col
    self.last_line = last_line
    self.last_col = last_col
    self.indent = indent
    self.func = func

  def has_comment(self, line):
    return line >= self.first_line and line <= self.last_line

  def __str__(self):
    return "<Comment for %s: [%d,%d:%d,%d] %s>" % (self.func, self.first_line, self.first_col, self.last_line, self.last_col, self.lines)


## Parses method comments.
#
#  @param cursor   Current libclang parser cursor
#  @param comments Array of comments: new ones will be appended there
def comment_method(cursor, comments):

  # we are looking for the following structure: method -> compound statement -> comment, i.e. we
  # need to extract the first comment in the compound statement composing the method

  in_compound_stmt = False
  expect_comment = False
  emit_comment = False

  comment = []
  comment_function = cursor.spelling or cursor.displayname
  comment_line_start = -1
  comment_line_end = -1
  comment_col_start = -1
  comment_col_end = -1
  comment_indent = -1

  for token in cursor.get_tokens():

    if token.cursor.kind == clang.cindex.CursorKind.COMPOUND_STMT:
      if not in_compound_stmt:
        in_compound_stmt = True
        expect_comment = True
        comment_line_end = -1
    else:
      if in_compound_stmt:
        in_compound_stmt = False
        emit_comment = True

    # tkind = str(token.kind)[str(token.kind).index('.')+1:]
    # ckind = str(token.cursor.kind)[str(token.cursor.kind).index('.')+1:]

    if in_compound_stmt:

      if expect_comment:

        extent = token.extent
        line_start = extent.start.line
        line_end = extent.end.line

        if token.kind == clang.cindex.TokenKind.PUNCTUATION and token.spelling == '{':
          pass

        elif token.kind == clang.cindex.TokenKind.COMMENT and (comment_line_end == -1 or (line_start == comment_line_end+1 and line_end-line_start == 0)):
          comment_line_end = line_end
          comment_col_end = extent.end.column

          if comment_indent == -1 or (extent.start.column-1) < comment_indent:
            comment_indent = extent.start.column-1

          if comment_line_start == -1:
            comment_line_start = line_start
            comment_col_start = extent.start.column
          comment.extend( token.spelling.split('\n') )

          # multiline comments are parsed in one go, therefore don't expect subsequent comments
          if line_end - line_start > 0:
            emit_comment = True
            expect_comment = False

        else:
          emit_comment = True
          expect_comment = False

    if emit_comment:

      comment = refactor_comment( comment )

      if len(comment) > 0:
        logging.debug("Comment found for function %s" % Colt(comment_function).magenta())
        comments.append( Comment(comment, comment_line_start, comment_col_start, comment_line_end, comment_col_end, comment_indent, comment_function) )

      comment = []
      comment_line_start = -1
      comment_line_end = -1
      comment_col_start = -1
      comment_col_end = -1
      comment_indent = -1

      emit_comment = False
      break


## Traverse the AST recursively starting from the current cursor.
#
#  @param cursor    A Clang parser cursor
#  @param filename  Name of the current file
#  @param comments  Array of comments: new ones will be appended there
#  @param recursion Current recursion depth
def traverse_ast(cursor, filename, comments, recursion=0):

  # libclang traverses included files as well: we do not want this behavior
  if cursor.location.file is not None and str(cursor.location.file) != filename:
    logging.debug("Skipping processing of included %s" % cursor.location.file)
    return

  text = cursor.spelling or cursor.displayname
  kind = str(cursor.kind)[str(cursor.kind).index('.')+1:]

  indent = ''
  for i in range(0, recursion):
    indent = indent + '  '

  if cursor.kind == clang.cindex.CursorKind.CXX_METHOD or cursor.kind == clang.cindex.CursorKind.CONSTRUCTOR or cursor.kind == clang.cindex.CursorKind.DESTRUCTOR:

    # cursor ran into a C++ method
    logging.debug( "%5d %s%s(%s)" % (cursor.extent.start.line, indent, Colt(kind).magenta(), Colt(text).blue()) )
    comment_method(cursor, comments)

  else:

    logging.debug( "%5d %s%s(%s)" % (cursor.extent.start.line, indent, kind, text) )

  for child_cursor in cursor.get_children():
    traverse_ast(child_cursor, filename, comments, recursion+1)


## Remove garbage from comments and convert special tags from THtml to Doxygen.
#
#  @param comment An array containing the lines of the original comment
def refactor_comment(comment):

  recomm = r'^(/{2,}|/\*)?\s*(.*?)\s*((/{2,})?\s*|\*/)$'

  new_comment = []
  insert_blank = False
  wait_first_non_blank = True
  for line_comment in comment:
    mcomm = re.search( recomm, line_comment )
    if mcomm:
      new_line_comment = mcomm.group(2)
      if new_line_comment == '':
        insert_blank = True
      else:
        if insert_blank and not wait_first_non_blank:
          new_comment.append('')
          insert_blank = False
        wait_first_non_blank = False
        new_comment.append( new_line_comment )
    else:
      assert False, 'Comment regexp does not match'

  return new_comment


## Rewrites all comments from the given file handler.
#
#  @param fhin     The file handler to read from
#  @param fhout    The file handler to write to
#  @param comments Array of comments
def rewrite_comments(fhin, fhout, comments):

  line_num = 0
  cur_comment = 0
  in_comment = False
  skip_empty = False

  if len(comments) > 0:
    comm = comments[0]
  else:
    comm = None

  for line in fhin:

    line_num = line_num + 1

    if comm and comm.has_comment( line_num ):

      if not in_comment:
        in_comment = True

        # extract the non-comment part and print it if it exists
        non_comment = line[ 0:comments[cur_comment].first_col-1 ].rstrip()
        if non_comment != '':
          fhout.write( non_comment + '\n' )

    else:
      if in_comment:

        in_comment = False

        # dumping comments
        text_indent = ''
        for i in range(0,comments[cur_comment].indent):
          text_indent = text_indent + ' '

        for lc in comments[cur_comment].lines:
          fhout.write( "%s/// %s\n" % (text_indent, lc) );
        fhout.write('\n')
        skip_empty = True

        cur_comment = cur_comment + 1
        if cur_comment < len(comments):
          comm = comments[cur_comment]
        else:
          comm = None

      line_out = line.rstrip('\n')
      if skip_empty:
        skip_empty = False
        if line_out.strip() != '':
          fhout.write( line_out + '\n' )
      else:
        fhout.write( line_out + '\n' )


## The main function.
#
#  Return value is the executable's return value.
def main(argv):

  # Setup logging on stderr
  log_level = logging.INFO
  logging.basicConfig(
    level=log_level,
    format='%(levelname)-8s %(funcName)-20s %(message)s',
    stream=sys.stderr
  )

  # Parse command-line options
  output_on_stdout = False
  try:
    opts, args = getopt.getopt( argv, 'od', [ 'debug=', 'stdout' ] )
    for o, a in opts:
      if o == '--debug':
        log_level = getattr( logging, a.upper(), None )
        if not isinstance(log_level, int):
          raise getopt.GetoptError('log level must be one of: DEBUG, INFO, WARNING, ERROR, CRITICAL')
      elif o == '-d':
        log_level = logging.DEBUG
      elif o == '-o' or o == '--stdout':
        logging.debug('Output on stdout instead of replacing original files')
        output_on_stdout = True
      else:
        assert False, 'Unhandled argument'
  except getopt.GetoptError as e:
    logging.fatal('Invalid arguments: %s' % e)
    return 1

  logging.getLogger('').setLevel(log_level)

  # Attempt to load libclang from a list of known locations
  libclang_locations = [
    '/usr/lib/llvm-3.5/lib/libclang.so.1',
    '/usr/lib/libclang.so',
    '/Library/Developer/CommandLineTools/usr/lib/libclang.dylib'
  ]
  libclang_found = False

  for lib in libclang_locations:
    if os.path.isfile(lib):
      clang.cindex.Config.set_library_file(lib)
      libclang_found = True
      break

  if not libclang_found:
    logging.fatal('Cannot find libclang')
    return 1

  # Loop over all files
  for fn in args:

    logging.info('Input file: %s' % Colt(fn).magenta())
    index = clang.cindex.Index.create()
    translation_unit = index.parse(fn, args=['-x', 'c++'])

    comments = []
    traverse_ast( translation_unit.cursor, fn, comments )
    for c in comments:
      logging.debug("Comment found for %s:" % Colt(c.func).magenta())
      for l in c.lines:
        logging.debug(
          Colt("[%d,%d:%d,%d] " % (c.first_line, c.first_col, c.last_line, c.last_col)).green() +
          "{%s}" % Colt(l).cyan()
        )

    try:

      if output_on_stdout:
        with open(fn, 'r') as fhin:
          rewrite_comments( fhin, sys.stdout, comments )
      else:
        fn_back = fn + '.thtml2doxy_backup'
        os.rename( fn, fn_back )

        with open(fn_back, 'r') as fhin, open(fn, 'w') as fhout:
          rewrite_comments( fhin, fhout, comments )

        os.remove( fn_back )
        logging.info("File %s converted to Doxygen: check differences before committing!" % Colt(fn).magenta())
    except (IOError,OSError) as e:
      logging.error('File operation failed: %s' % e)

  return 0


if __name__ == '__main__':
  sys.exit( main( sys.argv[1:] ) )