# Copyright 2014 Florian Bruhin (The Compiler) <mail@qutebrowser.org>
#
# This file is part of qutebrowser.
#
# qutebrowser is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# qutebrowser is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with qutebrowser.  If not, see <http://www.gnu.org/licenses/>.

"""A HintManager to draw hints over links."""

import logging
import math
from collections import namedtuple

from PyQt5.QtCore import pyqtSignal, pyqtSlot, QObject, QEvent, Qt
from PyQt5.QtGui import QMouseEvent, QClipboard
from PyQt5.QtWidgets import QApplication

import qutebrowser.config.config as config
import qutebrowser.keyinput.modeman as modeman
import qutebrowser.utils.message as message
import qutebrowser.utils.url as urlutils
import qutebrowser.utils.webelem as webelem
from qutebrowser.commands.exceptions import CommandError
from qutebrowser.utils.usertypes import enum


ElemTuple = namedtuple('ElemTuple', 'elem, label')


Target = enum('normal', 'tab', 'tab_bg', 'yank', 'yank_primary', 'cmd',
              'cmd_tab', 'cmd_tab_bg', 'rapid')


class HintManager(QObject):

    """Manage drawing hints over links or other elements.

    Class attributes:
        HINT_CSS: The CSS template to use for hints.
        HINT_TEXTS: Text displayed for different hinting modes.

    Attributes:
        _started: Whether we started hinting at the moment.
        _frames: The QWebFrames to use.
        _elems: A mapping from keystrings to (elem, label) namedtuples.
        _baseurl: The URL of the current page.
        _target: What to do with the opened links.
                 normal/tab/tab_bg: Get passed to BrowserTab.
                 yank/yank_primary: Yank to clipboard/primary selection
                 cmd/cmd_tab/cmd_tab_bg: Enter link to commandline
                 rapid: Rapid mode with background tabs
        _to_follow: The link to follow when enter is pressed.

    Signals:
        hint_strings_updated: Emitted when the possible hint strings changed.
                              arg: A list of hint strings.
        mouse_event: Mouse event to be posted in the web view.
                     arg: A QMouseEvent
        openurl: Open a new URL
                 arg 0: URL to open as QUrl.
                 arg 1: True if it should be opened in a new tab, else False.
        set_open_target: Set a new target to open the links in.
    """

    HINT_CSS = """
        display: {display};
        color: {config[colors][hints.fg]};
        background: {config[colors][hints.bg]};
        font: {config[fonts][hints]};
        border: {config[hints][border]};
        opacity: {config[hints][opacity]};
        z-index: 100000;
        pointer-events: none;
        position: absolute;
        left: {left}px;
        top: {top}px;
    """

    HINT_TEXTS = {
        Target.normal: "Follow hint...",
        Target.tab: "Follow hint in new tab...",
        Target.tab_bg: "Follow hint in background tab...",
        Target.yank: "Yank hint to clipboard...",
        Target.yank_primary: "Yank hint to primary selection...",
        Target.cmd: "Set hint in commandline...",
        Target.cmd_tab: "Set hint in commandline as new tab...",
        Target.cmd_tab_bg: "Set hint in commandline as background tab...",
        Target.rapid: "Follow hint (rapid mode)...",
    }

    hint_strings_updated = pyqtSignal(list)
    mouse_event = pyqtSignal('QMouseEvent')
    openurl = pyqtSignal('QUrl', bool)
    set_open_target = pyqtSignal(str)

    def __init__(self, parent=None):
        """Constructor.

        Args:
            frame: The QWebFrame to use for finding elements and drawing.
        """
        super().__init__(parent)
        self._elems = {}
        self._target = None
        self._baseurl = None
        self._to_follow = None
        self._started = False
        self._frames = []
        self._connected_frames = []
        modeman.instance().left.connect(self.on_mode_left)

    def _hint_strings(self, elems):
        """Calculate the hint strings for elems.

        Inspired by Vimium.

        Args:
            elems: The elements to get hint strings for.

        Return:
            A list of hint strings, in the same order as the elements.
        """
        if config.get('hints', 'mode') == 'number':
            chars = '0123456789'
        else:
            chars = config.get('hints', 'chars')
        # Determine how many digits the link hints will require in the worst
        # case. Usually we do not need all of these digits for every link
        # single hint, so we can show shorter hints for a few of the links.
        needed = math.ceil(math.log(len(elems), len(chars)))
        # Short hints are the number of hints we can possibly show which are
        # (needed - 1) digits in length.
        short_count = math.floor((len(chars) ** needed - len(elems)) /
                                 len(chars))
        long_count = len(elems) - short_count

        strings = []

        if needed > 1:
            for i in range(short_count):
                strings.append(self._number_to_hint_str(i, chars, needed - 1))

        start = short_count * len(chars)
        for i in range(start, start + long_count):
            strings.append(self._number_to_hint_str(i, chars, needed))

        return self._shuffle_hints(strings, len(chars))

    def _shuffle_hints(self, hints, length):
        """Shuffle the given set of hints so that they're scattered.

        Hints starting with the same character will be spread evenly throughout
        the array.

        Inspired by Vimium.

        Args:
            hints: A list of hint strings.
            length: Length of the available charset.

        Return:
            A list of shuffled hint strings.
        """
        buckets = [[] for i in range(length)]
        for i, hint in enumerate(hints):
            buckets[i % len(buckets)].append(hint)
        result = []
        for bucket in buckets:
            result += bucket
        return result

    def _number_to_hint_str(self, number, chars, digits=0):
        """Convert a number like "8" into a hint string like "JK".

        This is used to sequentially generate all of the hint text.
        The hint string will be "padded with zeroes" to ensure its length is >=
        digits.

        Inspired by Vimium.

        Args:
            number: The hint number.
            chars: The charset to use.
            digits: The minimum output length.

        Return:
            A hint string.
        """
        base = len(chars)
        hintstr = []
        remainder = 0
        while True:
            remainder = number % base
            hintstr.insert(0, chars[remainder])
            number -= remainder
            number //= base
            if number <= 0:
                break
        # Pad the hint string we're returning so that it matches digits.
        for _ in range(0, digits - len(hintstr)):
            hintstr.insert(0, chars[0])
        return ''.join(hintstr)

    def _get_hint_css(self, elem, label=None):
        """Get the hint CSS for the element given.

        Args:
            elem: The QWebElement to get the CSS for.
            label: The label QWebElement if display: none should be preserved.

        Return:
            The CSS to set as a string.
        """
        if label is None or label.attribute('hidden') != 'true':
            display = 'inline'
        else:
            display = 'none'
        rect = elem.geometry()
        return self.HINT_CSS.format(left=rect.x(), top=rect.y(),
                                    config=config.instance(), display=display)

    def _draw_label(self, elem, string):
        """Draw a hint label over an element.

        Args:
            elem: The QWebElement to use.
            string: The hint string to print.

        Return:
            The newly created label elment
        """
        css = self._get_hint_css(elem)
        doc = elem.webFrame().documentElement()
        # It seems impossible to create an empty QWebElement for which isNull()
        # is false so we can work with it.
        # As a workaround, we use appendInside() with markup as argument, and
        # then use lastChild() to get a reference to it.
        # See: http://stackoverflow.com/q/7364852/2085149
        doc.appendInside('<span class="qutehint" style="{}">{}</span>'.format(
                         css, string))
        return doc.lastChild()

    def _click(self, elem):
        """Click an element.

        Args:
            elem: The QWebElement to click.
        """
        if self._target == Target.rapid:
            target = Target.tab_bg
        else:
            target = self._target
        self.set_open_target.emit(Target[target])
        # FIXME Instead of clicking the center, we could have nicer heuristics.
        # e.g. parse (-webkit-)border-radius correctly and click text fields at
        # the bottom right, and everything else on the top left or so.
        pos = webelem.rect_on_view(elem).center()
        logging.debug("Clicking on '{}' at {}/{}".format(elem.toPlainText(),
                                                         pos.x(), pos.y()))
        events = [
            QMouseEvent(QEvent.MouseMove, pos, Qt.NoButton, Qt.NoButton,
                        Qt.NoModifier),
            QMouseEvent(QEvent.MouseButtonPress, pos, Qt.LeftButton,
                        Qt.NoButton, Qt.NoModifier),
            QMouseEvent(QEvent.MouseButtonRelease, pos, Qt.LeftButton,
                        Qt.NoButton, Qt.NoModifier),
        ]
        for evt in events:
            self.mouse_event.emit(evt)

    def _yank(self, link):
        """Yank an element to the clipboard or primary selection.

        Args:
            link: The URL to open.
        """
        sel = self._target == Target.yank_primary
        mode = QClipboard.Selection if sel else QClipboard.Clipboard
        QApplication.clipboard().setText(urlutils.urlstring(link), mode)
        message.info("URL yanked to {}".format("primary selection" if sel
                                               else "clipboard"))

    def _preset_cmd_text(self, link):
        """Preset a commandline text based on a hint URL.

        Args:
            link: The link to open.
        """
        commands = {
            Target.cmd: 'open',
            Target.cmd_tab: 'open-tab',
            Target.cmd_tab_bg: 'open-tab-bg',
        }
        message.set_cmd_text(':{} {}'.format(commands[self._target],
                                             urlutils.urlstring(link)))

    def _resolve_link(self, elem, baseurl=None):
        """Resolve a link and check if we want to keep it.

        Args:
            elem: The QWebElement to get the link of.
            baseurl: The baseurl of the current tab (overrides self._baseurl).

        Return:
            A QUrl with the absolute link, or None.
        """
        link = elem.attribute('href')
        if not link:
            return None
        if baseurl is None:
            baseurl = self._baseurl
        link = urlutils.qurl(link)
        if link.isRelative():
            link = baseurl.resolved(link)
        return link

    def _find_prevnext(self, frame, prev=False):
        """Find a prev/next element in frame."""
        # First check for <link rel="prev(ious)|next">
        elems = frame.findAllElements(
            webelem.SELECTORS[webelem.Group.prevnext_rel])
        rel_values = ['prev', 'previous'] if prev else ['next']
        for e in elems:
            if e.attribute('rel') in rel_values:
                return e
        # Then check for regular links
        elems = frame.findAllElements(
            webelem.SELECTORS[webelem.Group.prevnext])
        option = 'prev-regexes' if prev else 'next-regexes'
        if not elems:
            return None
        for regex in config.get('hints', option):
            for e in elems:
                if regex.match(e.toPlainText()):
                    return e
        return None

    def _connect_frame_signals(self):
        """Connect the contentsSizeChanged signals to all frames."""
        for f in self._frames:
            # For some reason we get segfaults sometimes when calling
            # frame.contentsSizeChanged.disconnect() later, maybe because Qt
            # already deleted the frame?
            # We work around this by never disconnecting this signal, and here
            # making sure we don't connect a frame which already was connected
            # at some point earlier.
            if f in self._connected_frames:
                logging.debug("Frame {} already connected!".format(f))
            else:
                logging.debug("Connecting frame {}".format(f))
                f.contentsSizeChanged.connect(self.on_contents_size_changed)
                self._connected_frames.append(f)

    def follow_prevnext(self, frame, baseurl, prev=False, newtab=False):
        """Click a "previous"/"next" element on the page.

        Args:
            frame: The frame where the element is in.
            baseurl: The base URL of the current tab.
            prev: True to open a "previous" link, False to open a "next" link.
            newtab: True to open in a new tab, False for the current tab.
        """
        elem = self._find_prevnext(frame, prev)
        if elem is None:
            raise CommandError("No {} links found!".format(
                "prev" if prev else "forward"))
        link = self._resolve_link(elem, baseurl)
        if link is None:
            raise CommandError("No {} links found!".format(
                "prev" if prev else "forward"))
        self.openurl.emit(link, newtab)

    def start(self, mainframe, baseurl, group=webelem.Group.all,
              target=Target.normal):
        """Start hinting.

        Args:
            mainframe: The main QWebFrame.
            baseurl: URL of the current page.
            group: Which group of elements to hint.
            target: What to do with the link. See attribute docstring.

        Emit:
            hint_strings_updated: Emitted to update keypraser.
        """
        if mainframe is None:
            # This should never happen since we check frame before calling
            # start. But since we had a bug where frame is None in
            # on_mode_left, we are extra careful here.
            raise ValueError("start() was called with frame=None")
        elems = []
        self._frames = webelem.get_child_frames(mainframe)
        for f in self._frames:
            elems += f.findAllElements(webelem.SELECTORS[group])
        filterfunc = webelem.FILTERS.get(group, lambda e: True)
        visible_elems = [e for e in elems if filterfunc(e) and
                         webelem.is_visible(e, mainframe)]
        if not visible_elems:
            raise CommandError("No elements found.")
        self._target = target
        self._baseurl = baseurl
        message.text(self.HINT_TEXTS[target])
        strings = self._hint_strings(visible_elems)
        for e, string in zip(visible_elems, strings):
            label = self._draw_label(e, string)
            self._elems[string] = ElemTuple(e, label)
        self._started = True
        self._connect_frame_signals()
        self.hint_strings_updated.emit(strings)
        modeman.enter('hint', 'HintManager.start')

    def handle_partial_key(self, keystr):
        """Handle a new partial keypress."""
        logging.debug("Handling new keystring: '{}'".format(keystr))
        for (string, elems) in self._elems.items():
            if string.startswith(keystr):
                matched = string[:len(keystr)]
                rest = string[len(keystr):]
                elems.label.setInnerXml('<font color="{}">{}</font>{}'.format(
                    config.get('colors', 'hints.fg.match'), matched, rest))
                if elems.label.attribute('hidden') == 'true':
                    # hidden element which matches again -> unhide it
                    elems.label.setAttribute('hidden', 'false')
                    css = self._get_hint_css(elems.elem, elems.label)
                    elems.label.setAttribute('style', css)
            else:
                # element doesn't match anymore -> hide it
                elems.label.setAttribute('hidden', 'true')
                css = self._get_hint_css(elems.elem, elems.label)
                elems.label.setAttribute('style', css)

    def filter_hints(self, filterstr):
        """Filter displayed hints according to a text."""
        for elems in self._elems.values():
            if elems.elem.toPlainText().lower().startswith(filterstr):
                if elems.label.attribute('hidden') == 'true':
                    # hidden element which matches again -> unhide it
                    elems.label.setAttribute('hidden', 'false')
                    css = self._get_hint_css(elems.elem, elems.label)
                    elems.label.setAttribute('style', css)
            else:
                # element doesn't match anymore -> hide it
                elems.label.setAttribute('hidden', 'true')
                css = self._get_hint_css(elems.elem, elems.label)
                elems.label.setAttribute('style', css)
        visible = {}
        for k, e in self._elems.items():
            if e.label.attribute('hidden') != 'true':
                visible[k] = e
        if not visible:
            # Whoops, filtered all hints
            modeman.leave('hint', 'all filtered')
        elif len(visible) == 1 and config.get('hints', 'auto-follow'):
            # unpacking gets us the first (and only) key in the dict.
            self.fire(*visible)

    def fire(self, keystr, force=False):
        """Fire a completed hint.

        Args:
            keystr: The keychain string to follow.
            force: When True, follow even when auto-follow is false.
        """
        if not (force or config.get('hints', 'auto-follow')):
            self.handle_partial_key(keystr)
            self._to_follow = keystr
            return
        # Handlers which take a QWebElement
        elem_handlers = {
            Target.normal: self._click,
            Target.tab: self._click,
            Target.tab_bg: self._click,
            Target.rapid: self._click,
        }
        # Handlers which take a link string
        link_handlers = {
            Target.yank: self._yank,
            Target.yank_primary: self._yank,
            Target.cmd: self._preset_cmd_text,
            Target.cmd_tab: self._preset_cmd_text,
            Target.cmd_tab_bg: self._preset_cmd_text,
        }
        elem = self._elems[keystr].elem
        if self._target in elem_handlers:
            elem_handlers[self._target](elem)
        elif self._target in link_handlers:
            link = self._resolve_link(elem)
            if link is None:
                raise CommandError("No suitable link found for this element.")
            link_handlers[self._target](link)
        else:
            raise ValueError("No suitable handler found!")
        if self._target != Target.rapid:
            modeman.leave('hint', 'followed')

    def follow_hint(self):
        """Follow the currently selected hint."""
        if not self._to_follow:
            raise CommandError("No hint to follow")
        self.fire(self._to_follow, force=True)

    @pyqtSlot('QSize')
    def on_contents_size_changed(self, _size):
        """Reposition hints if contents size changed."""
        if not self._started:
            # We got here because of some earlier hinting, but we can't simply
            # disconnect frames as this leads to occasional segfaults :-/
            logging.debug("Not hinting!")
            return
        logging.debug("Contents size changed...!")
        for elems in self._elems.values():
            css = self._get_hint_css(elems.elem, elems.label)
            elems.label.setAttribute('style', css)

    @pyqtSlot(str)
    def on_mode_left(self, mode):
        """Stop hinting when hinting mode was left."""
        if mode != 'hint':
            return
        self._started = False
        for elem in self._elems.values():
            if not elem.label.isNull():
                elem.label.removeFromDocument()
        self._elems = {}
        self._to_follow = None
        self._target = None
        self._frames = []
        message.clear()