earwigbot/wiki/tools/page.py

# -*- coding: utf-8  -*-

import re
from urllib import quote

from wiki.tools.exceptions import *

class Page(object):
    """
    EarwigBot's Wiki Toolset: Page Class

    Represents a Page on a given Site. Has methods for getting information
    about the page, getting page content, and so on. Category is a subclass of
    Page with additional methods.

    Public methods:
    title               -- returns the page's title, or pagename
    exists              -- returns whether the page exists
    pageid              -- returns an integer ID representing the page
    url                 -- returns the page's URL
    namespace           -- returns the page's namespace as an integer
    protection          -- returns the page's current protection status
    is_talkpage         -- returns True if the page is a talkpage, else False
    is_redirect         -- returns True if the page is a redirect, else False
    toggle_talk         -- returns a content page's talk page, or vice versa
    get                 -- returns page content
    get_redirect_target -- if the page is a redirect, returns its destination 
    """

    def __init__(self, site, title, follow_redirects=False):
        """Constructor for new Page instances.

        Takes three arguments: a Site object, the Page's title (or pagename),
        and whether or not to follow redirects (optional, defaults to False).

        As with User, site.get_page() is preferred. Site's method has support
        for a default `follow_redirects` value in our config, while __init__
        always defaults to False.

        __init__ will not do any API queries, but it will use basic namespace
        logic to determine our namespace ID and if we are a talkpage.
        """
        self._site = site
        self._title = title.strip()
        self._follow_redirects = self._keep_following = follow_redirects

        self._exists = 0
        self._pageid = None
        self._is_redirect = None
        self._lastrevid = None
        self._protection = None
        self._fullurl = None
        self._content = None

        # Try to determine the page's namespace using our site's namespace
        # converter:
        prefix = self._title.split(":", 1)[0]
        if prefix != title:  # ignore a page that's titled "Category" or "User"
            try:
                self._namespace = self._site.namespace_name_to_id(prefix)
            except NamespaceNotFoundError:
                self._namespace = 0
        else:
            self._namespace = 0

        # Is this a talkpage? Talkpages have odd IDs, while content pages have
        # even IDs, excluding the "special" namespaces:
        if self._namespace < 0:
            self._is_talkpage = False
        else:
            self._is_talkpage = self._namespace % 2 == 1

    def _force_validity(self):
        """Used to ensure that our page's title is valid.

        If this method is called when our page is not valid (and after
        _load_attributes() has been called), InvalidPageError will be raised.

        Note that validity != existence. If a page's title is invalid (e.g, it
        contains "[") it will always be invalid, and cannot be edited.
        """
        if self._exists == 1:
            e = "Page '{0}' is invalid.".format(self._title)
            raise InvalidPageError(e)

    def _force_existence(self):
        """Used to ensure that our page exists.

        If this method is called when our page doesn't exist (and after
        _load_attributes() has been called), PageNotFoundError will be raised.
        It will also call _force_validity() beforehand.
        """
        self._force_validity()
        if self._exists == 2:
            e = "Page '{0}' does not exist.".format(self._title)
            raise PageNotFoundError(e)

    def _load_wrapper(self):
        """Calls _load_attributes() and follows redirects if we're supposed to.

        This method will only follow redirects if follow_redirects=True was
        passed to __init__() (perhaps indirectly passed by site.get_page()).
        It avoids the API's &redirects param in favor of manual following,
        so we can act more realistically (we don't follow double redirects, and
        circular redirects don't break us).

        This will raise RedirectError if we have a problem following, but that
        is a bug and should NOT happen.

        If we're following a redirect, this will make a grand total of three
        API queries. It's a lot, but each one is quite small.
        """
        self._load_attributes()

        if self._keep_following and self._is_redirect:
            self._title = self.get_redirect_target()
            self._keep_following = False  # don't follow double redirects
            self._content = None  # reset the content we just loaded
            self._load_attributes()

    def _load_attributes(self, result=None):
        """Loads various data from the API in a single query.

        Loads self._title, ._exists, ._is_redirect, ._pageid, ._fullurl,
        ._protection, ._namespace, ._is_talkpage, and ._lastrevid using the
        API. It will do a query of its own unless `result` is provided, in
        which case we'll pretend `result` is what the query returned.

        Assuming the API is sound, this should not raise any exceptions.
        """
        if result is None:
            params = {"action": "query", "prop": "info", "titles": self._title,
                      "inprop": "protection|url"}
            result = self._site._api_query(params)

        res = result["query"]["pages"].values()[0]

        # Normalize our pagename/title thing:
        self._title = res["title"]

        try:
            res["redirect"]
        except KeyError:
            self._is_redirect = False
        else:
            self._is_redirect = True

        self._pageid = result["query"]["pages"].keys()[0]
        if int(self._pageid) < 0:
            try:
                res["missing"]
            except KeyError:
                # If it has a negative ID and it's invalid, then break here,
                # because there's no other data for us to get:
                self._exists = 1
                return
            else:
                # If it has a negative ID and it's missing; we can still get
                # data like the namespace, protection, and URL:
                self._exists = 2
        else:
            self._exists = 3

        self._fullurl = res["fullurl"]
        self._protection = res["protection"]

        # We've determined the namespace and talkpage status in __init__()
        # based on the title, but now we can be sure:
        self._namespace = res["ns"]
        self._is_talkpage = self._namespace % 2 == 1  # talkpages have odd IDs

        # This last field will only be specified if the page exists:
        try:
            self._lastrevid = res["lastrevid"]
        except KeyError:
            pass

    def _load_content(self, result=None):
        """Loads current page content from the API.

        If `result` is provided, we'll pretend that is the result of an API
        query and try to get content from that. Otherwise, we'll do an API
        query on our own.

        Don't call this directly, ever - use .get(force=True) if you want to
        force content reloading.
        """
        if result is None:
            params = {"action": "query", "prop": "revisions", "rvlimit": 1,
                      "rvprop": "content", "titles": self._title}
            result = self._site._api_query(params)

        res = result["query"]["pages"].values()[0]
        try:
            content = res["revisions"][0]["*"]
            self._content = content
        except KeyError:
            # This can only happen if the page was deleted since we last called
            # self._load_attributes(). In that case, some of our attributes are
            # outdated, so force another self._load_attributes():
            self._load_attributes()
            self._force_existence()

    def title(self, force=False):
        """Returns the Page's title, or pagename.

        This won't do any API queries on its own unless force is True, in which
        case the title will be forcibly reloaded from the API (normalizing it,
        and following redirects if follow_redirects=True was passed to
        __init__()). Any other methods that do API queries will reload title on
        their own, however, like exists() and get().
        """
        if force:
            self._load_wrapper()
        return self._title

    def exists(self, force=False):
        """Returns information about whether the Page exists or not.

        The returned "information" is a tuple with two items. The first is a
        bool, either True if the page exists or False if it does not. The
        second is a string giving more information, either "invalid", (title
        is invalid, e.g. it contains "["), "missing", or "exists".

        Makes an API query if force is True or if we haven't already made one.
        """
        cases = {
            0: (None, "unknown"),
            1: (False, "invalid"),
            2: (False, "missing"),
            3: (True, "exists"),
        }
        if self._exists == 0 or force:
            self._load_wrapper()
        return cases[self._exists]

    def pageid(self, force=False):
        """Returns an integer ID representing the Page.

        Makes an API query if force is True or if we haven't already made one.

        Raises InvalidPageError or PageNotFoundError if the page name is
        invalid or the page does not exist, respectively.
        """
        if self._exists == 0 or force:
            self._load_wrapper()
        self._force_existence()  # missing pages do not have IDs
        return self._pageid

    def url(self, force=False):
        """Returns the page's URL.

        Like title(), this won't do any API queries on its own unless force is
        True. If the API was never queried for this page, we will attempt to
        determine the URL ourselves based on the title.
        """
        if force:
            self._load_wrapper()
        if self._fullurl is not None:
            return self._fullurl
        else:
            slug = quote(self._title.replace(" ", "_"), safe="/:")
            path = self._site._article_path.replace("$1", slug)
            return ''.join((self._site._base_url, path))

    def namespace(self, force=False):
        """Returns the page's namespace ID (an integer).

        Like title(), this won't do any API queries on its own unless force is
        True. If the API was never queried for this page, we will attempt to
        determine the namespace ourselves based on the title.
        """
        if force:
            self._load_wrapper()
        return self._namespace

    def protection(self, force=False):
        """Returns the page's current protection status.

        Makes an API query if force is True or if we haven't already made one.

        Raises InvalidPageError if the page name is invalid. Will not raise an
        error if the page is missing because those can still be protected.
        """
        if self._exists == 0 or force:
            self._load_wrapper()
        self._force_validity()  # invalid pages cannot be protected
        return self._protection

    def is_talkpage(self, force=False):
        """Returns True if the page is a talkpage, else False.

        Like title(), this won't do any API queries on its own unless force is
        True. If the API was never queried for this page, we will attempt to
        determine the talkpage status ourselves based on its namespace ID.
        """
        if force:
            self._load_wrapper()
        return self._is_talkpage

    def is_redirect(self, force=False):
        """Returns True if the page is a redirect, else False.

        Makes an API query if force is True or if we haven't already made one.

        We will return False even if the page does not exist or is invalid.
        """
        if self._exists == 0 or force:
            self._load_wrapper()
        return self._is_redirect

    def toggle_talk(self, force=False, follow_redirects=None):
        """Returns a content page's talk page, or vice versa.

        The title of the new page is determined by namespace logic, not API
        queries. We won't make any API queries on our own unless force is True,
        and the only reason then would be to forcibly update the title or
        follow redirects if we haven't already made an API query.

        If `follow_redirects` is anything other than None (the default), it
        will be passed to the new Page's __init__(). Otherwise, we'll use the
        value passed to our own __init__().

        Will raise InvalidPageError if we try to get the talk page of a special
        page (in the Special: or Media: namespaces), but we won't raise an
        exception if our page is otherwise missing or invalid.
        """
        if force:
            self._load_wrapper()
        if self._namespace < 0:
            ns = self._site.namespace_id_to_name(self._namespace)
            e = "Pages in the {0} namespace can't have talk pages.".format(ns)
            raise InvalidPageError(e)

        if self._is_talkpage:
            new_ns = self._namespace - 1
        else:
            new_ns = self._namespace + 1

        try:
            body = self._title.split(":", 1)[1]
        except IndexError:
            body = self._title

        new_prefix = self._site.namespace_id_to_name(new_ns)

        # If the new page is in namespace 0, don't do ":Title" (it's correct,
        # but unnecessary), just do "Title":
        if new_prefix:
            new_title = ':'.join((new_prefix, body))
        else:
            new_title = body

        if follow_redirects is None:
            follow_redirects = self._follow_redirects
        return Page(self._site, new_title, follow_redirects)

    def get(self, force=False):
        """Returns page content, which is cached if you try to call get again.

        Use `force` to forcibly reload page content even if we've already
        loaded some. This is good if you want to edit a page multiple times,
        and you want to get updated content before you make your second edit.

        Raises InvalidPageError or PageNotFoundError if the page name is
        invalid or the page does not exist, respectively.
        """
        if force or self._exists == 0:
            # Kill two birds with one stone by doing an API query for both our
            # attributes and our page content:
            params = {"action": "query", "rvprop": "content", "rvlimit": 1,
                      "prop": "info|revisions", "inprop": "protection|url",
                      "titles": self._title}
            result = self._site._api_query(params)
            self._load_attributes(result=result)
            self._force_existence()
            self._load_content(result=result)

            # Follow redirects if we're told to:
            if self._keep_following and self._is_redirect:
                self._title = self.get_redirect_target()
                self._keep_following = False  # don't follow double redirects
                self._content = None  # reset the content we just loaded
                self.get(force=True)

            return self._content

        # Make sure we're dealing with a real page here. This may be outdated
        # if the page was deleted since we last called self._load_attributes(),
        # but self._load_content() can handle that:
        self._force_existence()

        if self._content is None:
            self._load_content()

        return self._content

    def get_redirect_target(self, force=False):
        """If the page is a redirect, returns its destination.

        Use `force` to forcibly reload content even if we've already loaded
        some before. Note that this method calls get() for page content.

        Raises InvalidPageError or PageNotFoundError if the page name is
        invalid or the page does not exist, respectively. Raises RedirectError
        if the page is not a redirect.
        """
        content = self.get(force)
        regexp = "^\s*\#\s*redirect\s*\[\[(.*?)\]\]"
        try:
            return re.findall(regexp, content, flags=re.IGNORECASE)[0]
        except IndexError:
            e = "The page does not appear to have a redirect target."
            raise RedirectError(e)