#!/usr/bin/env python
# encoding: utf-8

"""Some classes to conserve Vim's state for comparing over time."""

from collections import deque, namedtuple

from UltiSnips import _vim
from UltiSnips.compatibility import as_unicode, byte2col
from UltiSnips.position import Position

_Placeholder = namedtuple('_FrozenPlaceholder', ['current_text', 'start', 'end'])

class VimPosition(Position):

    """Represents the current position in the buffer, together with some status
    variables that might change our decisions down the line."""

    def __init__(self):
        pos = _vim.buf.cursor
        self._mode = _vim.eval('mode()')
        Position.__init__(self, pos.line, pos.col)

    @property
    def mode(self):
        """Returns the mode() this position was created."""
        return self._mode


class VimState(object):

    """Caches some state information from Vim to better guess what editing
    tasks the user might have done in the last step."""

    def __init__(self):
        self._poss = deque(maxlen=5)
        self._lvb = None

        self._text_to_expect = ''
        self._unnamed_reg_cached = False

        # We store the cached value of the unnamed register in Vim directly to
        # avoid any Unicode issues with saving and restoring the unnamed
        # register across the Python bindings.  The unnamed register can contain
        # data that cannot be coerced to Unicode, and so a simple vim.eval('@"')
        # fails badly.  Keeping the cached value in Vim directly, sidesteps the
        # problem.
        _vim.command('let g:_ultisnips_unnamed_reg_cache = ""')

    def remember_unnamed_register(self, text_to_expect):
        """Save the unnamed register.

        'text_to_expect' is text that we expect
        to be contained in the register the next time this method is called -
        this could be text from the tabstop that was selected and might have
        been overwritten. We will not cache that then.

        """
        self._unnamed_reg_cached = True
        escaped_text = self._text_to_expect.replace("'", "''")
        res = int(_vim.eval('@" != ' + "'" + escaped_text + "'"))
        if res:
            _vim.command('let g:_ultisnips_unnamed_reg_cache = @"')
        self._text_to_expect = text_to_expect

    def restore_unnamed_register(self):
        """Restores the unnamed register and forgets what we cached."""
        if not self._unnamed_reg_cached:
            return
        _vim.command('let @" = g:_ultisnips_unnamed_reg_cache')
        self._unnamed_reg_cached = False

    def remember_position(self):
        """Remember the current position as a previous pose."""
        self._poss.append(VimPosition())

    def remember_buffer(self, to):
        """Remember the content of the buffer and the position."""
        self._lvb = _vim.buf[to.start.line:to.end.line + 1]
        self._lvb_len = len(_vim.buf)
        self.remember_position()

    @property
    def diff_in_buffer_length(self):
        """Returns the difference in the length of the current buffer compared
        to the remembered."""
        return len(_vim.buf) - self._lvb_len

    @property
    def pos(self):
        """The last remembered position."""
        return self._poss[-1]

    @property
    def ppos(self):
        """The second to last remembered position."""
        return self._poss[-2]

    @property
    def remembered_buffer(self):
        """The content of the remembered buffer."""
        return self._lvb[:]


class VisualContentPreserver(object):

    """Saves the current visual selection and the selection mode it was done in
    (e.g. line selection, block selection or regular selection.)"""

    def __init__(self):
        self.reset()

    def reset(self):
        """Forget the preserved state."""
        self._mode = ''
        self._text = as_unicode('')
        self._placeholder = None

    def conserve(self):
        """Save the last visual selection ond the mode it was made in."""
        sl, sbyte = map(int,
                        (_vim.eval("""line("'<")"""), _vim.eval("""col("'<")""")))
        el, ebyte = map(int,
                        (_vim.eval("""line("'>")"""), _vim.eval("""col("'>")""")))
        sc = byte2col(sl, sbyte - 1)
        ec = byte2col(el, ebyte - 1)
        self._mode = _vim.eval('visualmode()')

        _vim_line_with_eol = lambda ln: _vim.buf[ln] + '\n'

        if sl == el:
            text = _vim_line_with_eol(sl - 1)[sc:ec + 1]
        else:
            text = _vim_line_with_eol(sl - 1)[sc:]
            for cl in range(sl, el - 1):
                text += _vim_line_with_eol(cl)
            text += _vim_line_with_eol(el - 1)[:ec + 1]
        self._text = text

    def conserve_placeholder(self, placeholder):
        if placeholder:
            self._placeholder = _Placeholder(
                placeholder.current_text,
                placeholder.start,
                placeholder.end
            )
        else:
            self._placeholder = None

    @property
    def text(self):
        """The conserved text."""
        return self._text

    @property
    def mode(self):
        """The conserved visualmode()."""
        return self._mode

    @property
    def placeholder(self):
        """Returns latest selected placeholder."""
        return self._placeholder