# -*- coding: utf-8 -*-
#
# Copyright (C) 2008 Edgewall Software
# All rights reserved.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at http://babel.edgewall.org/wiki/License.
#
# This software consists of voluntary contributions made by many
# individuals. For the exact contribution history, see the revision
# history and logs, available at http://babel.edgewall.org/log/.

"""A simple JavaScript 1.5 lexer which is used for the JavaScript
extractor.
"""

import re
from operator import itemgetter


operators = [
    '+', '-', '*', '%', '!=', '==', '<', '>', '<=', '>=', '=',
    '+=', '-=', '*=', '%=', '<<', '>>', '>>>', '<<=', '>>=',
    '>>>=', '&', '&=', '|', '|=', '&&', '||', '^', '^=', '(', ')',
    '[', ']', '{', '}', '!', '--', '++', '~', ',', ';', '.', ':'
]
operators.sort(lambda a, b: cmp(-len(a), -len(b)))

escapes = {'b': '\b', 'f': '\f', 'n': '\n', 'r': '\r', 't': '\t'}

rules = [
    (None, re.compile(r'\s+(?u)')),
    (None, re.compile(r'<!--.*')),
    ('linecomment', re.compile(r'//.*')),
    ('multilinecomment', re.compile(r'/\*.*?\*/(?us)')),
    ('name', re.compile(r'(\$+\w*|[^\W\d]\w*)(?u)')),
    ('number', re.compile(r'''(?x)(
        (?:0|[1-9]\d*)
        (\.\d+)?
        ([eE][-+]?\d+)? |
        (0x[a-fA-F0-9]+)
    )''')),
    ('operator', re.compile(r'(%s)' % '|'.join(map(re.escape, operators)))),
    ('string', re.compile(r'''(?xs)(
        '(?:[^'\\]*(?:\\.[^'\\]*)*)'  |
        "(?:[^"\\]*(?:\\.[^"\\]*)*)"
    )'''))
]

division_re = re.compile(r'/=?')
regex_re = re.compile(r'/(?:[^/\\]*(?:\\.[^/\\]*)*)/[a-zA-Z]*(?s)')
line_re = re.compile(r'(\r\n|\n|\r)')
line_join_re = re.compile(r'\\' + line_re.pattern)
uni_escape_re = re.compile(r'[a-fA-F0-9]{1,4}')


class Token(tuple):
    """Represents a token as returned by `tokenize`."""
    __slots__ = ()

    def __new__(cls, type, value, lineno):
        return tuple.__new__(cls, (type, value, lineno))

    type = property(itemgetter(0))
    value = property(itemgetter(1))
    lineno = property(itemgetter(2))


def indicates_division(token):
    """A helper function that helps the tokenizer to decide if the current
    token may be followed by a division operator.
    """
    if token.type == 'operator':
        return token.value in (')', ']', '}', '++', '--')
    return token.type in ('name', 'number', 'string', 'regexp')


def unquote_string(string):
    """Unquote a string with JavaScript rules.  The string has to start with
    string delimiters (``'`` or ``"``.)

    :return: a string
    """
    assert string and string[0] == string[-1] and string[0] in '"\'', \
        'string provided is not properly delimited'
    string = line_join_re.sub('\\1', string[1:-1])
    result = []
    add = result.append
    pos = 0

    while 1:
        # scan for the next escape
        escape_pos = string.find('\\', pos)
        if escape_pos < 0:
            break
        add(string[pos:escape_pos])

        # check which character is escaped
        next_char = string[escape_pos + 1]
        if next_char in escapes:
            add(escapes[next_char])

        # unicode escapes.  trie to consume up to four characters of
        # hexadecimal characters and try to interpret them as unicode
        # character point.  If there is no such character point, put
        # all the consumed characters into the string.
        elif next_char in 'uU':
            escaped = uni_escape_re.match(string, escape_pos + 2)
            if escaped is not None:
                escaped_value = escaped.group()
                if len(escaped_value) == 4:
                    try:
                        add(unichr(int(escaped_value, 16)))
                    except ValueError:
                        pass
                    else:
                        pos = escape_pos + 6
                        continue
                add(next_char + escaped_value)
                pos = escaped.end()
                continue
            else:
                add(next_char)

        # bogus escape.  Just remove the backslash.
        else:
            add(next_char)
        pos = escape_pos + 2

    if pos < len(string):
        add(string[pos:])

    return u''.join(result)


def tokenize(source):
    """Tokenize a JavaScript source.

    :return: generator of `Token`\s
    """
    may_divide = False
    pos = 0
    lineno = 1
    end = len(source)

    while pos < end:
        # handle regular rules first
        for token_type, rule in rules:
            match = rule.match(source, pos)
            if match is not None:
                break
        # if we don't have a match we don't give up yet, but check for
        # division operators or regular expression literals, based on
        # the status of `may_divide` which is determined by the last
        # processed non-whitespace token using `indicates_division`.
        else:
            if may_divide:
                match = division_re.match(source, pos)
                token_type = 'operator'
            else:
                match = regex_re.match(source, pos)
                token_type = 'regexp'
            if match is None:
                # woops. invalid syntax. jump one char ahead and try again.
                pos += 1
                continue

        token_value = match.group()
        if token_type is not None:
            token = Token(token_type, token_value, lineno)
            may_divide = indicates_division(token)
            yield token
        lineno += len(line_re.findall(token_value))
        pos = match.end()