# -*-python-*-
#
# Copyright (C) 1999-2008 The ViewCVS Group. All Rights Reserved.
#
# By using this file, you agree to the terms and conditions set forth in
# the LICENSE.html file which can be found at the top level of the ViewVC
# distribution or at http://viewvc.org/license-1.html.
#
# For more information, visit http://viewvc.org/
#
# -----------------------------------------------------------------------
#
# This file was originally based on portions of the blame.py script by
# Curt Hagenlocher.
#
# -----------------------------------------------------------------------

from __future__ import print_function
import string
from . import common


class _TokenStream:
    token_term = string.whitespace + ";:"
    try:
        token_term = frozenset(token_term)
    except NameError:
        pass

    # the algorithm is about the same speed for any CHUNK_SIZE chosen.
    # grab a good-sized chunk, but not too large to overwhelm memory.
    # note: we use a multiple of a standard block size
    CHUNK_SIZE  = 192 * 512  # about 100k

# CHUNK_SIZE  = 5   # for debugging, make the function grind...

    def __init__(self, file):
        self.rcsfile = file
        self.idx = 0
        self.buf = self.rcsfile.read(self.CHUNK_SIZE)
        if self.buf == '':
            raise RuntimeError('EOF')

    def get(self):
        "Get the next token from the RCS file."
        # Note: we can afford to loop within Python, examining individual
        # characters. For the whitespace and tokens, the number of iterations
        # is typically quite small. Thus, a simple iterative loop will beat
        # out more complex solutions.

        buf = self.buf
        lbuf = len(buf)
        idx = self.idx

        while 1:
            if idx == lbuf:
                buf = self.rcsfile.read(self.CHUNK_SIZE)
                if buf == '':
                    # signal EOF by returning None as the token
                    del self.buf   # so we fail if get() is called again
                    return None
                lbuf = len(buf)
                idx = 0

            if buf[idx] not in string.whitespace:
                break

            idx = idx + 1

        if buf[idx] in ';:':
            self.buf = buf
            self.idx = idx + 1
            return buf[idx]

        if buf[idx] != '@':
            end = idx + 1
            token = ''
            while 1:
                # find token characters in the current buffer
                while end < lbuf and buf[end] not in self.token_term:
                    end = end + 1
                token = token + buf[idx:end]

                if end < lbuf:
                    # we stopped before the end, so we have a full token
                    idx = end
                    break

                # we stopped at the end of the buffer, so we may have a partial token
                buf = self.rcsfile.read(self.CHUNK_SIZE)
                lbuf = len(buf)
                idx = end = 0

            self.buf = buf
            self.idx = idx
            return token

        # a "string" which starts with the "@" character. we'll skip it when we
        # search for content.
        idx = idx + 1

        chunks = []

        while 1:
            if idx == lbuf:
                idx = 0
                buf = self.rcsfile.read(self.CHUNK_SIZE)
                if buf == '':
                    raise RuntimeError('EOF')
                lbuf = len(buf)
            i = buf.find('@', idx)
            if i == -1:
                chunks.append(buf[idx:])
                idx = lbuf
                continue
            if i == lbuf - 1:
                chunks.append(buf[idx:i])
                idx = 0
                buf = '@' + self.rcsfile.read(self.CHUNK_SIZE)
                if buf == '@':
                    raise RuntimeError('EOF')
                lbuf = len(buf)
                continue
            if buf[i + 1] == '@':
                chunks.append(buf[idx:i+1])
                idx = i + 2
                continue

            chunks.append(buf[idx:i])

            self.buf = buf
            self.idx = i + 1

            return ''.join(chunks)

#  _get = get
#  def get(self):
        token = self._get()
        print('T:', repr(token))
        return token

    def match(self, match):
        "Try to match the next token from the input buffer."

        token = self.get()
        if token != match:
            raise common.RCSExpected(token, match)

    def unget(self, token):
        "Put this token back, for the next get() to return."

        # Override the class' .get method with a function which clears the
        # overridden method then returns the pushed token. Since this function
        # will not be looked up via the class mechanism, it should be a "normal"
        # function, meaning it won't have "self" automatically inserted.
        # Therefore, we need to pass both self and the token thru via defaults.

        # note: we don't put this into the input buffer because it may have been
        # @-unescaped already.

        def give_it_back(self=self, token=token):
            del self.get
            return token

        self.get = give_it_back

    def mget(self, count):
        "Return multiple tokens. 'next' is at the end."
        result = [ ]
        for i in range(count):
            result.append(self.get())
        result.reverse()
        return result


class Parser(common._Parser):
    stream_class = _TokenStream
