# *** encoding: utf-8 ***
"""
An :class:`~.InputProcessor` receives callbacks for the keystrokes parsed from
the input in the :class:`~prompt_toolkit.inputstream.InputStream` instance.

The `InputProcessor` will according to the implemented keybindings call the
correct callbacks when new key presses are feed through `feed`.
"""
from __future__ import unicode_literals
from prompt_toolkit.buffer import EditReadOnlyBuffer
from prompt_toolkit.filters.cli import ViNavigationMode
from prompt_toolkit.keys import Keys, Key
from prompt_toolkit.utils import Event

from .registry import BaseRegistry

from collections import deque
from six.moves import range
import weakref
import six

__all__ = (
    'InputProcessor',
    'KeyPress',
)


class KeyPress(object):
    """
    :param key: A `Keys` instance or text (one character).
    :param data: The received string on stdin. (Often vt100 escape codes.)
    """
    def __init__(self, key, data=None):
        assert isinstance(key, (six.text_type, Key))
        assert data is None or isinstance(data, six.text_type)

        if data is None:
            data = key.name if isinstance(key, Key) else key

        self.key = key
        self.data = data

    def __repr__(self):
        return '%s(key=%r, data=%r)' % (
            self.__class__.__name__, self.key, self.data)

    def __eq__(self, other):
        return self.key == other.key and self.data == other.data


class InputProcessor(object):
    """
    Statemachine that receives :class:`KeyPress` instances and according to the
    key bindings in the given :class:`Registry`, calls the matching handlers.

    ::

        p = InputProcessor(registry)

        # Send keys into the processor.
        p.feed(KeyPress(Keys.ControlX, '\x18'))
        p.feed(KeyPress(Keys.ControlC, '\x03')

        # Process all the keys in the queue.
        p.process_keys()

        # Now the ControlX-ControlC callback will be called if this sequence is
        # registered in the registry.

    :param registry: `BaseRegistry` instance.
    :param cli_ref: weakref to `CommandLineInterface`.
    """
    def __init__(self, registry, cli_ref):
        assert isinstance(registry, BaseRegistry)

        self._registry = registry
        self._cli_ref = cli_ref

        self.beforeKeyPress = Event(self)
        self.afterKeyPress = Event(self)

        # The queue of keys not yet send to our _process generator/state machine.
        self.input_queue = deque()

        # The key buffer that is matched in the generator state machine.
        # (This is at at most the amount of keys that make up for one key binding.)
        self.key_buffer = []

        # Simple macro recording. (Like readline does.)
        self.record_macro = False
        self.macro = []

        self.reset()

    def reset(self):
        self._previous_key_sequence = None
        self._previous_handler = None

        self._process_coroutine = self._process()
        self._process_coroutine.send(None)

        #: Readline argument (for repetition of commands.)
        #: https://www.gnu.org/software/bash/manual/html_node/Readline-Arguments.html
        self.arg = None

    def start_macro(self):
        " Start recording macro. "
        self.record_macro = True
        self.macro = []

    def end_macro(self):
        " End recording macro. "
        self.record_macro = False

    def call_macro(self):
        for k in self.macro:
            self.feed(k)

    def _get_matches(self, key_presses):
        """
        For a list of :class:`KeyPress` instances. Give the matching handlers
        that would handle this.
        """
        keys = tuple(k.key for k in key_presses)
        cli = self._cli_ref()

        # Try match, with mode flag
        return [b for b in self._registry.get_bindings_for_keys(keys) if b.filter(cli)]

    def _is_prefix_of_longer_match(self, key_presses):
        """
        For a list of :class:`KeyPress` instances. Return True if there is any
        handler that is bound to a suffix of this keys.
        """
        keys = tuple(k.key for k in key_presses)
        cli = self._cli_ref()

        # Get the filters for all the key bindings that have a longer match.
        # Note that we transform it into a `set`, because we don't care about
        # the actual bindings and executing it more than once doesn't make
        # sense. (Many key bindings share the same filter.)
        filters = set(b.filter for b in self._registry.get_bindings_starting_with_keys(keys))

        # When any key binding is active, return True.
        return any(f(cli) for f in filters)

    def _process(self):
        """
        Coroutine implementing the key match algorithm. Key strokes are sent
        into this generator, and it calls the appropriate handlers.
        """
        buffer = self.key_buffer
        retry = False

        while True:
            if retry:
                retry = False
            else:
                buffer.append((yield))

            # If we have some key presses, check for matches.
            if buffer:
                is_prefix_of_longer_match = self._is_prefix_of_longer_match(buffer)
                matches = self._get_matches(buffer)

                # When eager matches were found, give priority to them and also
                # ignore all the longer matches.
                eager_matches = [m for m in matches if m.eager(self._cli_ref())]

                if eager_matches:
                    matches = eager_matches
                    is_prefix_of_longer_match = False

                # Exact matches found, call handler.
                if not is_prefix_of_longer_match and matches:
                    self._call_handler(matches[-1], key_sequence=buffer)
                    del buffer[:]  # Keep reference.

                # No match found.
                elif not is_prefix_of_longer_match and not matches:
                    retry = True
                    found = False

                    # Loop over the input, try longest match first and shift.
                    for i in range(len(buffer), 0, -1):
                        matches = self._get_matches(buffer[:i])
                        if matches:
                            self._call_handler(matches[-1], key_sequence=buffer[:i])
                            del buffer[:i]
                            found = True
                            break

                    if not found:
                        del buffer[:1]

    def feed(self, key_press):
        """
        Add a new :class:`KeyPress` to the input queue.
        (Don't forget to call `process_keys` in order to process the queue.)
        """
        assert isinstance(key_press, KeyPress)
        self.input_queue.append(key_press)

    def process_keys(self):
        """
        Process all the keys in the `input_queue`.
        (To be called after `feed`.)

        Note: because of the `feed`/`process_keys` separation, it is
              possible to call `feed` from inside a key binding.
              This function keeps looping until the queue is empty.
        """
        while self.input_queue:
            key_press = self.input_queue.popleft()

            if key_press.key != Keys.CPRResponse:
                self.beforeKeyPress.fire()

            self._process_coroutine.send(key_press)

            if key_press.key != Keys.CPRResponse:
                self.afterKeyPress.fire()

        # Invalidate user interface.
        cli = self._cli_ref()
        if cli:
            cli.invalidate()

    def _call_handler(self, handler, key_sequence=None):
        was_recording = self.record_macro
        arg = self.arg
        self.arg = None

        event = KeyPressEvent(
            weakref.ref(self), arg=arg, key_sequence=key_sequence,
            previous_key_sequence=self._previous_key_sequence,
            is_repeat=(handler == self._previous_handler))

        # Save the state of the current buffer.
        cli = event.cli  # Can be `None` (In unit-tests only.)

        if handler.save_before(event) and cli:
            cli.current_buffer.save_to_undo_stack()

        # Call handler.
        try:
            handler.call(event)
            self._fix_vi_cursor_position(event)

        except EditReadOnlyBuffer:
            # When a key binding does an attempt to change a buffer which is
            # read-only, we can just silently ignore that.
            pass

        self._previous_key_sequence = key_sequence
        self._previous_handler = handler

        # Record the key sequence in our macro. (Only if we're in macro mode
        # before and after executing the key.)
        if self.record_macro and was_recording:
            self.macro.extend(key_sequence)

    def _fix_vi_cursor_position(self, event):
        """
        After every command, make sure that if we are in Vi navigation mode, we
        never put the cursor after the last character of a line. (Unless it's
        an empty line.)
        """
        cli = self._cli_ref()
        if cli:
            buff = cli.current_buffer
            preferred_column = buff.preferred_column

            if (ViNavigationMode()(event.cli) and
                    buff.document.is_cursor_at_the_end_of_line and
                    len(buff.document.current_line) > 0):
                buff.cursor_position -= 1

                # Set the preferred_column for arrow up/down again.
                # (This was cleared after changing the cursor position.)
                buff.preferred_column = preferred_column



class KeyPressEvent(object):
    """
    Key press event, delivered to key bindings.

    :param input_processor_ref: Weak reference to the `InputProcessor`.
    :param arg: Repetition argument.
    :param key_sequence: List of `KeyPress` instances.
    :param previouskey_sequence: Previous list of `KeyPress` instances.
    :param is_repeat: True when the previous event was delivered to the same handler.
    """
    def __init__(self, input_processor_ref, arg=None, key_sequence=None,
            previous_key_sequence=None, is_repeat=False):
        self._input_processor_ref = input_processor_ref
        self.key_sequence = key_sequence
        self.previous_key_sequence = previous_key_sequence

        #: True when the previous key sequence was handled by the same handler.
        self.is_repeat = is_repeat

        self._arg = arg

    def __repr__(self):
        return 'KeyPressEvent(arg=%r, key_sequence=%r, is_repeat=%r)' % (
                self.arg, self.key_sequence, self.is_repeat)

    @property
    def data(self):
        return self.key_sequence[-1].data

    @property
    def input_processor(self):
        return self._input_processor_ref()

    @property
    def cli(self):
        """
        Command line interface.
        """
        return self.input_processor._cli_ref()

    @property
    def current_buffer(self):
        """
        The current buffer.
        """
        return self.cli.current_buffer

    @property
    def arg(self):
        """
        Repetition argument.
        """
        if self._arg == '-':
            return -1

        result = int(self._arg or 1)

        # Don't exceed a million.
        if int(result) >= 1000000:
            result = 1

        return result

    @property
    def arg_present(self):
        """
        True if repetition argument was explicitly provided.
        """
        return self._arg is not None

    def append_to_arg_count(self, data):
        """
        Add digit to the input argument.

        :param data: the typed digit as string
        """
        assert data in '-0123456789'
        current = self._arg

        if data == '-':
            assert current is None or current == '-'
            result = data
        elif current is None:
            result = data
        else:
            result = "%s%s" % (current, data)

        self.input_processor.arg = result
