takahe/users/models/identity.py

from functools import cached_property, partial
from typing import Literal
from urllib.parse import urlparse

import httpx
import urlman
from asgiref.sync import async_to_sync, sync_to_async
from django.conf import settings
from django.db import IntegrityError, models
from django.utils import timezone
from django.utils.functional import lazy
from lxml import etree

from core.exceptions import ActorMismatchError
from core.html import ContentRenderer, strip_html
from core.ld import (
    canonicalise,
    format_ld_date,
    get_first_image_url,
    get_list,
    media_type_from_filename,
)
from core.models import Config
from core.signatures import HttpSignature, RsaKeys
from core.uploads import upload_namer
from core.uris import AutoAbsoluteUrl, RelativeAbsoluteUrl, StaticAbsoluteUrl
from stator.models import State, StateField, StateGraph, StatorModel
from users.models.domain import Domain
from users.models.system_actor import SystemActor


class IdentityStates(StateGraph):
    """
    Identities sit in "updated" for up to system.identity_max_age, and then
    go back to "outdated" for refetching.

    When a local identity is "edited" or "deleted", it will fanout the change to
    all followers and transition to "updated"
    """

    outdated = State(try_interval=3600, force_initial=True)
    updated = State(try_interval=86400 * 7, attempt_immediately=False)

    edited = State(try_interval=300, attempt_immediately=True)
    deleted = State(try_interval=300, attempt_immediately=True)
    deleted_fanned_out = State(externally_progressed=True)

    deleted.transitions_to(deleted_fanned_out)

    edited.transitions_to(updated)
    updated.transitions_to(edited)
    edited.transitions_to(deleted)

    outdated.transitions_to(updated)
    updated.transitions_to(outdated)

    @classmethod
    def group_deleted(cls):
        return [cls.deleted, cls.deleted_fanned_out]

    @classmethod
    async def targets_fan_out(cls, identity: "Identity", type_: str) -> None:
        from activities.models import FanOut
        from users.models import Follow

        # Fan out to each target
        shared_inboxes = set()
        async for follower in Follow.objects.select_related("source", "target").filter(
            target=identity
        ):
            # Dedupe shared_inbox_uri
            shared_uri = follower.source.shared_inbox_uri
            if shared_uri and shared_uri in shared_inboxes:
                continue

            await FanOut.objects.acreate(
                identity=follower.source,
                type=type_,
                subject_identity=identity,
            )
            shared_inboxes.add(shared_uri)

    @classmethod
    async def handle_edited(cls, instance: "Identity"):
        from activities.models import FanOut

        if not instance.local:
            return cls.updated

        identity = await instance.afetch_full()
        await cls.targets_fan_out(identity, FanOut.Types.identity_edited)
        return cls.updated

    @classmethod
    async def handle_deleted(cls, instance: "Identity"):
        from activities.models import FanOut

        if not instance.local:
            return cls.updated

        identity = await instance.afetch_full()
        await cls.targets_fan_out(identity, FanOut.Types.identity_deleted)
        return cls.deleted_fanned_out

    @classmethod
    async def handle_outdated(cls, identity: "Identity"):

        # Local identities never need fetching
        if identity.local:
            return cls.updated
        # Run the actor fetch and progress to updated if it succeeds
        if await identity.fetch_actor():
            return cls.updated

    @classmethod
    async def handle_updated(cls, instance: "Identity"):
        if instance.state_age > Config.system.identity_max_age:
            return cls.outdated


class IdentityQuerySet(models.QuerySet):
    def not_deleted(self):
        query = self.exclude(state__in=IdentityStates.group_deleted())
        return query


class IdentityManager(models.Manager):
    def get_queryset(self):
        return IdentityQuerySet(self.model, using=self._db)

    def not_deleted(self):
        return self.get_queryset().not_deleted()


class Identity(StatorModel):
    """
    Represents both local and remote Fediverse identities (actors)
    """

    class Restriction(models.IntegerChoices):
        none = 0
        limited = 1
        blocked = 2

    ACTOR_TYPES = ["person", "service", "application", "group", "organization"]

    # The Actor URI is essentially also a PK - we keep the default numeric
    # one around as well for making nice URLs etc.
    actor_uri = models.CharField(max_length=500, unique=True)

    state = StateField(IdentityStates)

    local = models.BooleanField()
    users = models.ManyToManyField(
        "users.User",
        related_name="identities",
        blank=True,
    )

    username = models.CharField(max_length=500, blank=True, null=True)
    # Must be a display domain if present
    domain = models.ForeignKey(
        "users.Domain",
        blank=True,
        null=True,
        on_delete=models.PROTECT,
        related_name="identities",
    )

    name = models.CharField(max_length=500, blank=True, null=True)
    summary = models.TextField(blank=True, null=True)
    manually_approves_followers = models.BooleanField(blank=True, null=True)
    discoverable = models.BooleanField(default=True)

    profile_uri = models.CharField(max_length=500, blank=True, null=True)
    inbox_uri = models.CharField(max_length=500, blank=True, null=True)
    shared_inbox_uri = models.CharField(max_length=500, blank=True, null=True)
    outbox_uri = models.CharField(max_length=500, blank=True, null=True)
    icon_uri = models.CharField(max_length=500, blank=True, null=True)
    image_uri = models.CharField(max_length=500, blank=True, null=True)
    followers_uri = models.CharField(max_length=500, blank=True, null=True)
    following_uri = models.CharField(max_length=500, blank=True, null=True)
    actor_type = models.CharField(max_length=100, default="person")

    icon = models.ImageField(
        upload_to=partial(upload_namer, "profile_images"), blank=True, null=True
    )
    image = models.ImageField(
        upload_to=partial(upload_namer, "background_images"), blank=True, null=True
    )

    # Should be a list of {"name":..., "value":...} dicts
    metadata = models.JSONField(blank=True, null=True)

    # Should be a list of object URIs (we don't want a full M2M here)
    pinned = models.JSONField(blank=True, null=True)

    # Admin-only moderation fields
    sensitive = models.BooleanField(default=False)
    restriction = models.IntegerField(
        choices=Restriction.choices, default=Restriction.none
    )
    admin_notes = models.TextField(null=True, blank=True)

    private_key = models.TextField(null=True, blank=True)
    public_key = models.TextField(null=True, blank=True)
    public_key_id = models.TextField(null=True, blank=True)

    created = models.DateTimeField(auto_now_add=True)
    updated = models.DateTimeField(auto_now=True)
    fetched = models.DateTimeField(null=True, blank=True)
    deleted = models.DateTimeField(null=True, blank=True)

    objects = IdentityManager()

    ### Model attributes ###

    class Meta:
        verbose_name_plural = "identities"
        unique_together = [("username", "domain")]

    class urls(urlman.Urls):
        view = "/@{self.username}@{self.domain_id}/"
        action = "{view}action/"
        followers = "{view}followers/"
        following = "{view}following/"
        activate = "{view}activate/"
        admin = "/admin/identities/"
        admin_edit = "{admin}{self.pk}/"

        def get_scheme(self, url):
            return "https"

        def get_hostname(self, url):
            return self.instance.domain.uri_domain

    def __str__(self):
        if self.username and self.domain_id:
            return self.handle
        return self.actor_uri

    def absolute_profile_uri(self):
        """
        Returns a profile URI that is always absolute, for sending out to
        other servers.
        """
        if self.local:
            return f"https://{self.domain.uri_domain}/@{self.username}/"
        else:
            return self.profile_uri

    def all_absolute_profile_uris(self) -> list[str]:
        """
        Returns alist of profile URIs that are always absolute. For local addresses,
        this includes the short and long form URIs.
        """
        if not self.local:
            return [self.profile_uri]
        return [
            f"https://{self.domain.uri_domain}/@{self.username}/",
            f"https://{self.domain.uri_domain}/@{self.username}@{self.domain_id}/",
        ]

    def local_icon_url(self) -> RelativeAbsoluteUrl:
        """
        Returns an icon for use by us, with fallbacks to a placeholder
        """
        if self.icon:
            return RelativeAbsoluteUrl(self.icon.url)
        elif self.icon_uri:
            return AutoAbsoluteUrl(f"/proxy/identity_icon/{self.pk}/")
        else:
            return StaticAbsoluteUrl("img/unknown-icon-128.png")

    def local_image_url(self) -> RelativeAbsoluteUrl | None:
        """
        Returns a background image for us, returning None if there isn't one
        """
        if self.image:
            return AutoAbsoluteUrl(self.image.url)
        elif self.image_uri:
            return AutoAbsoluteUrl(f"/proxy/identity_image/{self.pk}/")
        return None

    @property
    def safe_summary(self):
        return ContentRenderer(local=True).render_identity_summary(self.summary, self)

    @property
    def safe_metadata(self):
        renderer = ContentRenderer(local=True)

        if not self.metadata:
            return []
        return [
            {
                "name": renderer.render_identity_data(data["name"], self, strip=True),
                "value": renderer.render_identity_data(data["value"], self, strip=True),
            }
            for data in self.metadata
        ]

    ### Alternate constructors/fetchers ###

    @classmethod
    def by_username_and_domain(cls, username, domain, fetch=False, local=False):
        if username.startswith("@"):
            raise ValueError("Username must not start with @")
        domain = domain.lower()
        try:
            if local:
                return cls.objects.get(
                    username__iexact=username,
                    domain_id=domain,
                    local=True,
                )
            else:
                return cls.objects.get(
                    username__iexact=username,
                    domain_id=domain,
                )
        except cls.DoesNotExist:
            if fetch and not local:
                actor_uri, handle = async_to_sync(cls.fetch_webfinger)(
                    f"{username}@{domain}"
                )
                if handle is None:
                    return None
                # See if this actually does match an existing actor
                try:
                    return cls.objects.get(actor_uri=actor_uri)
                except cls.DoesNotExist:
                    pass
                # OK, make one
                username, domain = handle.split("@")
                domain = Domain.get_remote_domain(domain)
                return cls.objects.create(
                    actor_uri=actor_uri,
                    username=username,
                    domain_id=domain,
                    local=False,
                )
            return None

    @classmethod
    def by_actor_uri(cls, uri, create=False, transient=False) -> "Identity":
        try:
            return cls.objects.get(actor_uri=uri)
        except cls.DoesNotExist:
            if create:
                if transient:
                    # Some code (like inbox fetching) doesn't need this saved
                    # to the DB until the fetch succeeds
                    return cls(actor_uri=uri, local=False)
                else:
                    return cls.objects.create(actor_uri=uri, local=False)
            else:
                raise cls.DoesNotExist(f"No identity found with actor_uri {uri}")

    ### Dynamic properties ###

    @property
    def name_or_handle(self):
        return self.name or self.handle

    @cached_property
    def html_name_or_handle(self):
        """
        Return the name_or_handle with any HTML substitutions made
        """
        return ContentRenderer(local=True).render_identity_data(
            self.name_or_handle, self, strip=True
        )

    @property
    def handle(self):
        if self.username is None:
            return "(unknown user)"
        if self.domain_id:
            return f"{self.username}@{self.domain_id}"
        return f"{self.username}@(unknown server)"

    @property
    def data_age(self) -> float:
        """
        How old our copy of this data is, in seconds
        """
        if self.local:
            return 0
        if self.fetched is None:
            return 10000000000
        return (timezone.now() - self.fetched).total_seconds()

    @property
    def outdated(self) -> bool:
        # TODO: Setting
        return self.data_age > 60 * 24 * 24

    @property
    def blocked(self) -> bool:
        return self.restriction == self.Restriction.blocked

    @property
    def limited(self) -> bool:
        return self.restriction == self.Restriction.limited

    ### Async helpers ###

    async def afetch_full(self):
        """
        Returns a version of the object with all relations pre-loaded
        """
        return await Identity.objects.select_related("domain").aget(pk=self.pk)

    ### ActivityPub (outbound) ###

    def to_webfinger(self):
        aliases = [self.absolute_profile_uri()]

        actor_links = []

        if self.restriction != Identity.Restriction.blocked:
            # Blocked users don't get a profile page
            actor_links.append(
                {
                    "rel": "http://webfinger.net/rel/profile-page",
                    "type": "text/html",
                    "href": self.absolute_profile_uri(),
                },
            )

        # TODO: How to handle Restriction.limited and Restriction.blocked?
        #       Exposing the activity+json will allow migrating off server
        actor_links.extend(
            [
                {
                    "rel": "self",
                    "type": "application/activity+json",
                    "href": self.actor_uri,
                }
            ]
        )

        return {
            "subject": f"acct:{self.handle}",
            "aliases": aliases,
            "links": actor_links,
        }

    def to_ap(self):
        response = {
            "id": self.actor_uri,
            "type": self.actor_type.title(),
            "inbox": self.actor_uri + "inbox/",
            "outbox": self.actor_uri + "outbox/",
            "preferredUsername": self.username,
            "publicKey": {
                "id": self.public_key_id,
                "owner": self.actor_uri,
                "publicKeyPem": self.public_key,
            },
            "published": self.created.strftime("%Y-%m-%dT%H:%M:%SZ"),
            "url": self.absolute_profile_uri(),
            "toot:discoverable": self.discoverable,
        }
        if self.name:
            response["name"] = self.name
        if self.summary:
            response["summary"] = self.summary
        if self.icon:
            response["icon"] = {
                "type": "Image",
                "mediaType": media_type_from_filename(self.icon.name),
                "url": self.icon.url,
            }
        if self.image:
            response["image"] = {
                "type": "Image",
                "mediaType": media_type_from_filename(self.image.name),
                "url": self.image.url,
            }
        if self.local:
            response["endpoints"] = {
                "sharedInbox": f"https://{self.domain.uri_domain}/inbox/",
            }
        if self.metadata:
            response["attachment"] = [
                {
                    "type": "http://schema.org#PropertyValue",
                    "name": strip_html(item["name"], linkify=False),
                    "value": strip_html(item["value"]),
                }
                for item in self.metadata
            ]
        return response

    def to_ap_tag(self):
        """
        Return this Identity as an ActivityPub Tag
        """
        return {
            "href": self.actor_uri,
            "name": "@" + self.handle,
            "type": "Mention",
        }

    def to_update_ap(self):
        """
        Returns the AP JSON to update this object
        """
        object = self.to_ap()
        return {
            "type": "Update",
            "id": self.actor_uri + "#update",
            "actor": self.actor_uri,
            "object": object,
        }

    def to_delete_ap(self):
        """
        Returns the AP JSON to delete this object
        """
        object = self.to_ap()
        return {
            "type": "Delete",
            "id": self.actor_uri + "#delete",
            "actor": self.actor_uri,
            "object": object,
        }

    ### ActivityPub (inbound) ###

    @classmethod
    def handle_update_ap(cls, data):
        """
        Takes an incoming update.person message and just forces us to add it
        to our fetch queue (don't want to bother with two load paths right now)
        """
        # Find by actor
        try:
            actor = cls.by_actor_uri(data["actor"])
            actor.transition_perform(IdentityStates.outdated)
        except cls.DoesNotExist:
            pass

    @classmethod
    def handle_delete_ap(cls, data):
        """
        Takes an incoming update.person message and just forces us to add it
        to our fetch queue (don't want to bother with two load paths right now)
        """
        # Assert that the actor matches the object
        if data["actor"] != data["object"]:
            raise ActorMismatchError(
                f"Actor {data['actor']} trying to delete identity {data['object']}"
            )
        # Find by actor
        try:
            actor = cls.by_actor_uri(data["actor"])
            actor.delete()
        except cls.DoesNotExist:
            pass

    ### Actor/Webfinger fetching ###

    @classmethod
    async def fetch_webfinger(cls, handle: str) -> tuple[str | None, str | None]:
        """
        Given a username@domain handle, returns a tuple of
        (actor uri, canonical handle) or None, None if it does not resolve.
        """
        domain = handle.split("@")[1].lower()
        webfinger_url = f"https://{domain}/.well-known/webfinger?resource={{uri}}"

        async with httpx.AsyncClient(
            timeout=settings.SETUP.REMOTE_TIMEOUT,
            headers={"User-Agent": settings.TAKAHE_USER_AGENT},
        ) as client:
            try:
                response = await client.get(
                    f"https://{domain}/.well-known/host-meta",
                    follow_redirects=True,
                    headers={"Accept": "application/xml"},
                )

                # In the case of anything other than a success, we'll still try
                # hitting the webfinger URL on the domain we were given to handle
                # incorrectly setup servers.
                if response.status_code == 200 and response.content.strip():
                    tree = etree.fromstring(response.content)
                    template = tree.xpath(
                        "string(.//*[local-name() = 'Link' and @rel='lrdd']/@template)"
                    )
                    if template:
                        webfinger_url = template
            except (httpx.RequestError, etree.ParseError):
                pass

            try:
                response = await client.get(
                    webfinger_url.format(uri=f"acct:{handle}"),
                    follow_redirects=True,
                    headers={"Accept": "application/json"},
                )
                response.raise_for_status()
            except httpx.RequestError as ex:
                response = getattr(ex, "response", None)
                if (
                    response
                    and response.status_code < 500
                    and response.status_code not in [404, 410]
                ):
                    raise ValueError(
                        f"Client error fetching webfinger: {response.status_code}",
                        response.content,
                    )
                return None, None

        try:
            data = response.json()
        except ValueError:
            # Some servers return these with a 200 status code!
            if b"not found" in response.content.lower():
                return None, None
            raise ValueError(
                "JSON parse error fetching webfinger",
                response.content,
            )
        if data["subject"].startswith("acct:"):
            data["subject"] = data["subject"][5:]
        for link in data["links"]:
            if (
                link.get("type") == "application/activity+json"
                and link.get("rel") == "self"
            ):
                return link["href"], data["subject"]
        return None, None

    async def fetch_actor(self) -> bool:
        """
        Fetches the user's actor information, as well as their domain from
        webfinger if it's available.
        """
        from activities.models import Emoji

        if self.local:
            raise ValueError("Cannot fetch local identities")
        try:
            response = await SystemActor().signed_request(
                method="get",
                uri=self.actor_uri,
            )
        except httpx.RequestError:
            return False
        content_type = response.headers.get("content-type")
        if content_type and "html" in content_type:
            # Some servers don't properly handle "application/activity+json"
            return False
        if response.status_code == 410:
            # Their account got deleted, so let's do the same.
            if self.pk:
                await Identity.objects.filter(pk=self.pk).adelete()
            return False
        if response.status_code == 404:
            # We don't trust this as much as 410 Gone, but skip for now
            return False
        if response.status_code >= 500:
            return False
        if response.status_code >= 400:
            raise ValueError(
                f"Client error fetching actor: {response.status_code}", response.content
            )
        document = canonicalise(response.json(), include_security=True)
        if "type" not in document:
            return False
        self.name = document.get("name")
        self.profile_uri = document.get("url")
        self.inbox_uri = document.get("inbox")
        self.outbox_uri = document.get("outbox")
        self.followers_uri = document.get("followers")
        self.following_uri = document.get("following")
        self.actor_type = document["type"].lower()
        self.shared_inbox_uri = document.get("endpoints", {}).get("sharedInbox")
        self.summary = document.get("summary")
        self.username = document.get("preferredUsername")
        if self.username and "@value" in self.username:
            self.username = self.username["@value"]
        if self.username:
            self.username = self.username
        self.manually_approves_followers = document.get("manuallyApprovesFollowers")
        self.public_key = document.get("publicKey", {}).get("publicKeyPem")
        self.public_key_id = document.get("publicKey", {}).get("id")
        # Sometimes the public key PEM is in a language construct?
        if isinstance(self.public_key, dict):
            self.public_key = self.public_key["@value"]
        self.icon_uri = get_first_image_url(document.get("icon", None))
        self.image_uri = get_first_image_url(document.get("image", None))
        self.discoverable = document.get("toot:discoverable", True)
        # Profile links/metadata
        self.metadata = []
        for attachment in get_list(document, "attachment"):
            if (
                attachment["type"] == "http://schema.org#PropertyValue"
                and "name" in attachment
                and "http://schema.org#value" in attachment
            ):
                self.metadata.append(
                    {
                        "name": attachment.get("name"),
                        "value": strip_html(attachment.get("http://schema.org#value")),
                    }
                )
        # Now go do webfinger with that info to see if we can get a canonical domain
        actor_url_parts = urlparse(self.actor_uri)
        get_domain = sync_to_async(Domain.get_remote_domain)
        if self.username:
            webfinger_actor, webfinger_handle = await self.fetch_webfinger(
                f"{self.username}@{actor_url_parts.hostname}"
            )
            if webfinger_handle:
                webfinger_username, webfinger_domain = webfinger_handle.split("@")
                self.username = webfinger_username
                self.domain = await get_domain(webfinger_domain)
            else:
                self.domain = await get_domain(actor_url_parts.hostname)
        else:
            self.domain = await get_domain(actor_url_parts.hostname)
        # Emojis (we need the domain so we do them here)
        for tag in get_list(document, "tag"):
            if tag["type"].lower() == "toot:emoji":
                await sync_to_async(Emoji.by_ap_tag)(self.domain, tag, create=True)
        # Mark as fetched
        self.fetched = timezone.now()
        try:
            await sync_to_async(self.save)()
        except IntegrityError as e:
            # See if we can fetch a PK and save there
            if self.pk is None:
                try:
                    other_row = await Identity.objects.aget(actor_uri=self.actor_uri)
                except Identity.DoesNotExist:
                    raise ValueError(
                        f"Could not save Identity at end of actor fetch: {e}"
                    )
                self.pk: int | None = other_row.pk
                await sync_to_async(self.save)()
        return True

    ### OpenGraph API ###

    def to_opengraph_dict(self) -> dict:
        return {
            "og:title": f"{self.name} (@{self.handle})",
            "og:type": "profile",
            "og:description": self.summary,
            "og:profile:username": self.handle,
            "og:image:url": self.local_icon_url().absolute,
            "og:image:height": 85,
            "og:image:width": 85,
        }

    ### Mastodon Client API ###

    def to_mastodon_json(self):
        from activities.models import Emoji

        header_image = self.local_image_url()
        metadata_value_text = (
            " ".join([m["value"] for m in self.metadata]) if self.metadata else ""
        )
        emojis = Emoji.emojis_from_content(
            f"{self.name} {self.summary} {metadata_value_text}", self.domain
        )
        return {
            "id": self.pk,
            "username": self.username or "",
            "acct": self.username if self.local else self.handle,
            "url": self.absolute_profile_uri() or "",
            "display_name": self.name or "",
            "note": self.summary or "",
            "avatar": self.local_icon_url().absolute,
            "avatar_static": self.local_icon_url().absolute,
            "header": header_image.absolute if header_image else None,
            "header_static": header_image.absolute if header_image else None,
            "locked": False,
            "fields": (
                [
                    {"name": m["name"], "value": m["value"], "verified_at": None}
                    for m in self.metadata
                ]
                if self.metadata
                else []
            ),
            "emojis": [emoji.to_mastodon_json() for emoji in emojis],
            "bot": False,
            "group": False,
            "discoverable": self.discoverable,
            "suspended": False,
            "limited": False,
            "created_at": format_ld_date(
                self.created.replace(hour=0, minute=0, second=0, microsecond=0)
            ),
            "last_status_at": None,  # TODO: populate
            "statuses_count": self.posts.count(),
            "followers_count": self.inbound_follows.count(),
            "following_count": self.outbound_follows.count(),
        }

    ### Cryptography ###

    async def signed_request(
        self,
        method: Literal["get", "post"],
        uri: str,
        body: dict | None = None,
    ):
        """
        Performs a signed request on behalf of the System Actor.
        """
        return await HttpSignature.signed_request(
            method=method,
            uri=uri,
            body=body,
            private_key=self.private_key,
            key_id=self.public_key_id,
        )

    def generate_keypair(self):
        if not self.local:
            raise ValueError("Cannot generate keypair for remote user")
        self.private_key, self.public_key = RsaKeys.generate_keypair()
        self.public_key_id = self.actor_uri + "#main-key"
        self.save()

    ### Config ###

    @cached_property
    def config_identity(self) -> Config.IdentityOptions:
        return Config.load_identity(self)

    def lazy_config_value(self, key: str):
        """
        Lazily load a config value for this Identity
        """
        if key not in Config.IdentityOptions.__fields__:
            raise KeyError(f"Undefined IdentityOption for {key}")
        return lazy(lambda: getattr(self.config_identity, key))