# vim: ft=python fileencoding=utf-8 sts=4 sw=4 et:

# Copyright 2015-2021 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 <https://www.gnu.org/licenses/>.

"""Simple history which gets written to disk."""

import os
import time
import contextlib
import pathlib
from typing import cast, Mapping, MutableSequence, Optional

from PyQt5.QtCore import pyqtSlot, QUrl, QObject, pyqtSignal
from PyQt5.QtWidgets import QProgressDialog, QApplication

from qutebrowser.config import config
from qutebrowser.api import cmdutils
from qutebrowser.utils import utils, log, usertypes, message, qtutils
from qutebrowser.misc import objects, sql


web_history = cast('WebHistory', None)


class HistoryProgress:

    """Progress dialog for history imports/conversions.

    This makes WebHistory simpler as it can call methods of this class even
    when we don't want to show a progress dialog (for very small imports). This
    means tick() and finish() can be called even when start() wasn't.
    """

    def __init__(self):
        self._progress = None
        self._value = 0

    def start(self, text):
        """Start showing a progress dialog."""
        self._progress = QProgressDialog()
        self._progress.setMaximum(0)  # unknown
        self._progress.setMinimumDuration(0)
        self._progress.setLabelText(text)
        self._progress.setCancelButton(None)
        self._progress.setAutoClose(False)
        self._progress.show()
        QApplication.processEvents()

    def set_maximum(self, maximum):
        """Set the progress maximum as soon as we know about it."""
        assert self._progress is not None
        self._progress.setMaximum(maximum)
        QApplication.processEvents()

    def tick(self):
        """Increase the displayed progress value."""
        self._value += 1
        if self._progress is not None:
            self._progress.setValue(self._value)
            QApplication.processEvents()

    def finish(self):
        """Finish showing the progress dialog.

        After this is called, the object can be reused.
        """
        if self._progress is not None:
            self._progress.hide()


class CompletionMetaInfo(sql.SqlTable):

    """Table containing meta-information for the completion."""

    KEYS = {
        'excluded_patterns': '',
        'force_rebuild': False,
    }

    def __init__(self, database: sql.Database,
                 parent: Optional[QObject] = None) -> None:
        self._fields = ['key', 'value']
        self._constraints = {'key': 'PRIMARY KEY'}
        super().__init__(database, "CompletionMetaInfo", self._fields,
                         constraints=self._constraints, parent=parent)

        if database.user_version_changed():
            self._init_default_values()

    def _check_key(self, key):
        if key not in self.KEYS:
            raise KeyError(key)

    def try_recover(self):
        """Try recovering the table structure.

        This should be called if getting a value via __getattr__ failed. In theory, this
        should never happen, in practice, it does.
        """
        self._create_table(self._fields, constraints=self._constraints, force=True)
        self._init_default_values()

    def _init_default_values(self):
        for key, default in self.KEYS.items():
            if key not in self:
                self[key] = default

    def __contains__(self, key):
        self._check_key(key)
        query = self.contains_query('key')
        return query.run(val=key).value()

    def __getitem__(self, key):
        self._check_key(key)
        query = self.database.query('SELECT value FROM CompletionMetaInfo '
                                    'WHERE key = :key')
        return query.run(key=key).value()

    def __setitem__(self, key, value):
        self._check_key(key)
        self.insert({'key': key, 'value': value}, replace=True)


class CompletionHistory(sql.SqlTable):

    """History which only has the newest entry for each URL."""

    def __init__(self, database: sql.Database,
                 parent: Optional[QObject] = None) -> None:
        super().__init__(database, "CompletionHistory", ['url', 'title', 'last_atime'],
                         constraints={'url': 'PRIMARY KEY',
                                      'title': 'NOT NULL',
                                      'last_atime': 'NOT NULL'},
                         parent=parent)
        self.create_index('CompletionHistoryAtimeIndex', 'last_atime')


class WebHistory(sql.SqlTable):

    """The global history of visited pages.

    Attributes:
        completion: A CompletionHistory instance.
        metainfo: A CompletionMetaInfo instance.
        _progress: A HistoryProgress instance.
    """

    # All web history cleared
    history_cleared = pyqtSignal()
    # one url cleared
    url_cleared = pyqtSignal(QUrl)

    def __init__(self, database: sql.Database, progress: HistoryProgress,
                 parent: Optional[QObject] = None) -> None:
        super().__init__(database, "History", ['url', 'title', 'atime', 'redirect'],
                         constraints={'url': 'NOT NULL',
                                      'title': 'NOT NULL',
                                      'atime': 'NOT NULL',
                                      'redirect': 'NOT NULL'},
                         parent=parent)
        self._progress = progress
        # Store the last saved url to avoid duplicate immediate saves.
        self._last_url = None

        self.completion = CompletionHistory(database, parent=self)
        self.metainfo = CompletionMetaInfo(database, parent=self)

        try:
            rebuild_completion = self.metainfo['force_rebuild']
        except sql.BugError:  # pragma: no cover
            log.sql.warning("Failed to access meta info, trying to recover...",
                            exc_info=True)
            self.metainfo.try_recover()
            rebuild_completion = self.metainfo['force_rebuild']

        if self.database.user_version_changed():
            with self.database.transaction():
                # If the DB user version changed, run a full cleanup and rebuild the
                # completion history.
                #
                # In the future, this could be improved to only be done when actually
                # needed - but version changes happen very infrequently, rebuilding
                # everything gives us less corner-cases to deal with, and we can run a
                # VACUUM to make things smaller.
                self._cleanup_history()
                rebuild_completion = True
                self.database.upgrade_user_version()

        # Get a string of all patterns
        patterns = config.instance.get_str('completion.web_history.exclude')

        # If patterns changed, update them in database and rebuild completion
        if self.metainfo['excluded_patterns'] != patterns:
            self.metainfo['excluded_patterns'] = patterns
            rebuild_completion = True

        if rebuild_completion and self:
            # If no history exists, we don't need to spawn a dialog for
            # cleaning it up.
            self._rebuild_completion()

        self.create_index('HistoryIndex', 'url')
        self.create_index('HistoryAtimeIndex', 'atime')
        self._contains_query = self.contains_query('url')
        self._between_query = self.database.query('SELECT * FROM History '
                                                  'where not redirect '
                                                  'and not url like "qute://%" '
                                                  'and atime > :earliest '
                                                  'and atime <= :latest '
                                                  'ORDER BY atime desc')

        self._before_query = self.database.query('SELECT * FROM History '
                                                 'where not redirect '
                                                 'and not url like "qute://%" '
                                                 'and atime <= :latest '
                                                 'ORDER BY atime desc '
                                                 'limit :limit offset :offset')

    def __repr__(self):
        return utils.get_repr(self, length=len(self))

    def __contains__(self, url):
        return self._contains_query.run(val=url).value()

    @contextlib.contextmanager
    def _handle_sql_errors(self):
        try:
            yield
        except sql.KnownError as e:
            message.error(f"Failed to write history: {e.text()}")

    def _is_excluded_from_completion(self, url):
        """Check if the given URL is excluded from the completion."""
        patterns = config.cache['completion.web_history.exclude']
        return any(pattern.matches(url) for pattern in patterns)

    def _is_excluded_entirely(self, url):
        """Check if the given URL is excluded from the entire history.

        This is the case for URLs which can't be visited at a later point; or which are
        usually excessively long.

        NOTE: If you add new filters here, it might be a good idea to adjust the
        _USER_VERSION code and _cleanup_history so that older histories get cleaned up
        accordingly as well.
        """
        return (
            url.scheme() in {'data', 'view-source'} or
            (url.scheme() == 'qute' and url.host() in {'back', 'pdfjs'})
        )

    def _cleanup_history(self):
        """Do a one-time cleanup of the entire history.

        This is run only once after the v2.0.0 upgrade, based on the database's
        user_version.
        """
        terms = [
            'data:%',
            'view-source:%',
            'qute://back%',
            'qute://pdfjs%',
        ]
        where_clause = ' OR '.join(f"url LIKE '{term}'" for term in terms)
        q = self.database.query(f'DELETE FROM History WHERE {where_clause}')
        entries = q.run()
        log.sql.debug(f"Cleanup removed {entries.rows_affected()} items")

    def _rebuild_completion(self):
        # If this process was interrupted, make sure we trigger a rebuild again
        # at the next start.
        self.metainfo['force_rebuild'] = True

        data: Mapping[str, MutableSequence[str]] = {
            'url': [],
            'title': [],
            'last_atime': []
        }

        self._progress.start(
            "<b>Rebuilding completion...</b><br>"
            "This is a one-time operation and happens because the database version "
            "or <i>completion.web_history.exclude</i> was changed."
        )

        # Delete old entries
        self.completion.delete_all()
        QApplication.processEvents()

        # Select the latest entry for each url
        q = self.database.query('SELECT url, title, max(atime) AS atime FROM History '
                                'WHERE NOT redirect '
                                'GROUP BY url ORDER BY atime asc')
        result = q.run()
        QApplication.processEvents()
        entries = list(result)

        self._progress.set_maximum(len(entries))

        for entry in entries:
            self._progress.tick()

            url = QUrl(entry.url)
            if self._is_excluded_from_completion(url):
                continue
            data['url'].append(self._format_completion_url(url))
            data['title'].append(entry.title)
            data['last_atime'].append(entry.atime)

        self._progress.set_maximum(0)

        # We might have caused fragmentation - let's clean up.
        self.database.query('VACUUM').run()
        QApplication.processEvents()

        self.completion.insert_batch(data, replace=True)
        QApplication.processEvents()

        self._progress.finish()
        self.metainfo['force_rebuild'] = False

    def get_recent(self):
        """Get the most recent history entries."""
        return self.select(sort_by='atime', sort_order='desc', limit=100)

    def entries_between(self, earliest, latest):
        """Iterate non-redirect, non-qute entries between two timestamps.

        Args:
            earliest: Omit timestamps earlier than this.
            latest: Omit timestamps later than this.
        """
        self._between_query.run(earliest=earliest, latest=latest)
        return iter(self._between_query)

    def entries_before(self, latest, limit, offset):
        """Iterate non-redirect, non-qute entries occurring before a timestamp.

        Args:
            latest: Omit timestamps more recent than this.
            limit: Max number of entries to include.
            offset: Number of entries to skip.
        """
        self._before_query.run(latest=latest, limit=limit, offset=offset)
        return iter(self._before_query)

    def clear(self):
        """Clear all browsing history."""
        with self._handle_sql_errors():
            self.delete_all()
            self.completion.delete_all()
        self.history_cleared.emit()
        self._last_url = None

    def delete_url(self, url):
        """Remove all history entries with the given url.

        Args:
            url: URL string to delete.
        """
        qurl = QUrl(url)
        qtutils.ensure_valid(qurl)
        self.delete('url', self._format_url(qurl))
        self.completion.delete('url', self._format_completion_url(qurl))
        if self._last_url == url:
            self._last_url = None
        self.url_cleared.emit(qurl)

    @pyqtSlot(QUrl, QUrl, str)
    def add_from_tab(self, url, requested_url, title):
        """Add a new history entry as slot, called from a BrowserTab."""
        if self._is_excluded_entirely(url) or self._is_excluded_entirely(requested_url):
            return
        if url.isEmpty():
            # things set via setHtml
            return

        no_formatting = QUrl.UrlFormattingOption(0)
        if (requested_url.isValid() and
                not requested_url.matches(url, no_formatting)):
            # If the url of the page is different than the url of the link
            # originally clicked, save them both.
            self.add_url(requested_url, title, redirect=True)
        if url != self._last_url:
            self.add_url(url, title)
            self._last_url = url

    def add_url(self, url, title="", *, redirect=False, atime=None):
        """Called via add_from_tab when a URL should be added to the history.

        Args:
            url: A url (as QUrl) to add to the history.
            title: The tab title to add.
            redirect: Whether the entry was redirected to another URL
                      (hidden in completion)
            atime: Override the atime used to add the entry
        """
        if not url.isValid():
            log.misc.warning("Ignoring invalid URL being added to history")
            return

        if 'no-sql-history' in objects.debug_flags:
            return

        atime = int(atime) if (atime is not None) else int(time.time())

        with self._handle_sql_errors():
            self.insert({'url': self._format_url(url),
                         'title': title,
                         'atime': atime,
                         'redirect': redirect})

            if redirect or self._is_excluded_from_completion(url):
                return

            self.completion.insert({
                'url': self._format_completion_url(url),
                'title': title,
                'last_atime': atime
            }, replace=True)

    def _format_url(self, url):
        return url.toString(QUrl.RemovePassword | QUrl.FullyEncoded)

    def _format_completion_url(self, url):
        return url.toString(QUrl.RemovePassword)


@cmdutils.register()
def history_clear(force=False):
    """Clear all browsing history.

    Note this only clears the global history
    (e.g. `~/.local/share/qutebrowser/history` on Linux) but not cookies,
    the back/forward history of a tab, cache or other persistent data.

    Args:
        force: Don't ask for confirmation.
    """
    if force:
        web_history.clear()
    else:
        message.confirm_async(yes_action=web_history.clear,
                              title="Clear all browsing history?")


@cmdutils.register(debug=True)
def debug_dump_history(dest):
    """Dump the history to a file in the old pre-SQL format.

    Args:
        dest: Where to write the file to.
    """
    dest = os.path.expanduser(dest)

    lines = (f'{int(x.atime)}{"-r" * x.redirect} {x.url} {x.title}'
             for x in web_history.select(sort_by='atime', sort_order='asc'))

    try:
        with open(dest, 'w', encoding='utf-8') as f:
            f.write('\n'.join(lines))
        message.info(f"Dumped history to {dest}")
    except OSError as e:
        raise cmdutils.CommandError(f'Could not write history: {e}')


def init(db_path: pathlib.Path, parent: Optional[QObject] = None) -> None:
    """Initialize the web history.

    Args:
        db_path: The path for the SQLite database.
        parent: The parent to use for WebHistory.
    """
    global web_history
    progress = HistoryProgress()
    database = sql.Database(str(db_path))
    web_history = WebHistory(database=database, progress=progress, parent=parent)

    if objects.backend == usertypes.Backend.QtWebKit:  # pragma: no cover
        from qutebrowser.browser.webkit import webkithistory
        webkithistory.init(web_history)
        return
    assert objects.backend == usertypes.Backend.QtWebEngine, objects.backend
