#!/usr/bin/env python3
'''
NAME
    code-filter - AsciiDoc filter to highlight language keywords

SYNOPSIS
    code-filter -b backend -l language [ -t tabsize ]
                [ --help | -h ] [ --version | -v ]

DESCRIPTION
    This filter reads source code from the standard input, highlights language
    keywords and comments and writes to the standard output.

    The purpose of this program is to demonstrate how to write an AsciiDoc
    filter -- it's much to simplistic to be passed off as a code syntax
    highlighter. Use the 'source-highlight-filter' instead.


OPTIONS
    --help, -h
        Print this documentation.

    -b
        Backend output file format: 'docbook', 'linuxdoc', 'html', 'css'.

    -l
        The name of the source code language: 'python', 'ruby', 'c++', 'c'.

    -t tabsize
        Expand source tabs to tabsize spaces.

    --version, -v
        Print program version number.

BUGS
    - Code on the same line as a block comment is treated as comment.
      Keywords inside literal strings are highlighted.
    - There doesn't appear to be an easy way to accommodate linuxdoc so
      just pass it through without markup.

AUTHOR
    Written by Stuart Rackham, <srackham@gmail.com>

URLS
    https://github.com/asciidoc/asciidoc-py3
    https://asciidoc.org/

COPYING
    Copyright (C) 2002-2013 Stuart Rackham.
    Copyright (C) 2013-2020 AsciiDoc Contributors.

    Free use of this software is granted under the terms of the GNU General
    Public License version 2 (GPLv2).
'''

import os
import sys
import re

VERSION = '1.1.2'

# Globals.
language = None
backend = None
tabsize = 8
keywordtags = {
    'html':
        ('<strong>', '</strong>'),
    'css':
        ('<strong>', '</strong>'),
    'docbook':
        ('<emphasis role="strong">', '</emphasis>'),
    'linuxdoc':
        ('', '')
}
commenttags = {
    'html':
        ('<i>', '</i>'),
    'css':
        ('<i>', '</i>'),
    'docbook':
        ('<emphasis>', '</emphasis>'),
    'linuxdoc':
        ('', '')
}
keywords = {
    'python':
        (
            'and', 'del', 'for', 'is', 'raise', 'assert', 'elif', 'from',
            'lambda', 'return', 'break', 'else', 'global', 'not', 'try', 'class',
            'except', 'if', 'or', 'while', 'continue', 'exec', 'import', 'pass',
            'yield', 'def', 'finally', 'in', 'print'
        ),
    'ruby':
        (
            '__FILE__', 'and', 'def', 'end', 'in', 'or', 'self', 'unless',
            '__LINE__', 'begin', 'defined?' 'ensure', 'module', 'redo', 'super',
            'until', 'BEGIN', 'break', 'do', 'false', 'next', 'rescue', 'then',
            'when', 'END', 'case', 'else', 'for', 'nil', 'retry', 'true', 'while',
            'alias', 'class', 'elsif', 'if', 'not', 'return', 'undef', 'yield'
        ),
    'c++':
        (
            'asm', 'auto', 'bool', 'break', 'case', 'catch', 'char', 'class',
            'const', 'const_cast', 'continue', 'default', 'delete', 'do', 'double',
            'dynamic_cast', 'else', 'enum', 'explicit', 'export', 'extern',
            'false', 'float', 'for', 'friend', 'goto', 'if', 'inline', 'int',
            'long', 'mutable', 'namespace', 'new', 'operator', 'private',
            'protected', 'public', 'register', 'reinterpret_cast', 'return',
            'short', 'signed', 'sizeof', 'static', 'static_cast', 'struct',
            'switch', 'template', 'this', 'throw', 'true', 'try', 'typedef',
            'typeid', 'typename', 'union', 'unsigned', 'using', 'virtual', 'void',
            'volatile', 'wchar_t', 'while'
        )
}
block_comments = {
    'python': ("'''", "'''"),
    'ruby': None,
    'c++': ('/*', '*/')
}
inline_comments = {
    'python': '#',
    'ruby': '#',
    'c++': '//'
}


def print_stderr(line):
    sys.stderr.write(line+os.linesep)


def sub_keyword(mo):
    '''re.subs() argument to tag keywords.'''
    word = mo.group('word')
    if word in keywords[language]:
        stag, etag = keywordtags[backend]
        return stag+word+etag
    else:
        return word


def code_filter():
    '''This function does all the work.'''
    global language, backend
    inline_comment = inline_comments[language]
    blk_comment = block_comments[language]
    if blk_comment:
        blk_comment = (
            re.escape(block_comments[language][0]),
            re.escape(block_comments[language][1])
        )
    stag, etag = commenttags[backend]
    in_comment = 0  # True if we're inside a multi-line block comment.
    tag_comment = 0  # True if we should tag the current line as a comment.
    line = sys.stdin.readline()
    while line:
        line = line.rstrip()
        line = line.expandtabs(tabsize)
        # Escape special characters.
        line = line.replace('&', '&amp;')
        line = line.replace('<', '&lt;')
        line = line.replace('>', '&gt;')
        # Process block comment.
        if blk_comment:
            if in_comment:
                if re.match(r'.*'+blk_comment[1]+r'$', line):
                    in_comment = 0
            else:
                if re.match(r'^\s*'+blk_comment[0]+r'.*'+blk_comment[1], line):
                    # Single line block comment.
                    tag_comment = 1
                elif re.match(r'^\s*'+blk_comment[0], line):
                    # Start of multi-line block comment.
                    tag_comment = 1
                    in_comment = 1
                else:
                    tag_comment = 0
        if tag_comment:
            if line:
                line = stag+line+etag
        else:
            if inline_comment:
                pos = line.find(inline_comment)
            else:
                pos = -1
            if pos >= 0:
                # Process inline comment.
                line = re.sub(r'\b(?P<word>\w+)\b', sub_keyword, line[:pos]) \
                    + stag + line[pos:] + etag
            else:
                line = re.sub(r'\b(?P<word>\w+)\b', sub_keyword, line)
        sys.stdout.write(line + os.linesep)
        line = sys.stdin.readline()


def usage(msg=''):
    if msg:
        print_stderr(msg)
    print_stderr('Usage: code-filter -b backend -l language [ -t tabsize ]')
    print_stderr('                   [ --help | -h ] [ --version | -v ]')


def main():
    global language, backend, tabsize
    # Process command line options.
    import getopt
    opts, args = getopt.getopt(
        sys.argv[1:],
        'b:l:ht:v',
        ['help', 'version']
    )
    if len(args) > 0:
        usage()
        sys.exit(1)
    for o, v in opts:
        if o in ('--help', '-h'):
            print(__doc__)
            sys.exit(0)
        if o in ('--version', '-v'):
            print('code-filter version %s' % (VERSION,))
            sys.exit(0)
        if o == '-b':
            backend = v
        if o == '-l':
            v = v.lower()
            if v == 'c':
                v = 'c++'
            language = v
        if o == '-t':
            try:
                tabsize = int(v)
            except BaseException:
                usage('illegal tabsize')
                sys.exit(1)
            if tabsize <= 0:
                usage('illegal tabsize')
                sys.exit(1)
    if backend is None:
        usage('backend option is mandatory')
        sys.exit(1)
    if backend not in keywordtags:
        usage('illegal backend option')
        sys.exit(1)
    if language is None:
        usage('language option is mandatory')
        sys.exit(1)
    if language not in keywords:
        usage('illegal language option')
        sys.exit(1)
    # Do the work.
    code_filter()


if __name__ == "__main__":
    try:
        main()
    except (KeyboardInterrupt, SystemExit):
        pass
    except BaseException:
        print_stderr(
            "%s: unexpected exit status: %s" %
            (os.path.basename(sys.argv[0]), sys.exc_info()[1])
        )
    # Exit with previous sys.exit() status or zero if no sys.exit().
    sys.exit(sys.exc_info()[1])
