#
# This file is licensed under the Affero General Public License (AGPL) version 3.
#
# Copyright 2020 The Matrix.org Foundation C.I.C.
# Copyright 2015, 2016 OpenMarket Ltd
# Copyright (C) 2023 New Vector, Ltd
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# See the GNU Affero General Public License for more details:
# <https://www.gnu.org/licenses/agpl-3.0.html>.
#
# Originally licensed under the Apache License, Version 2.0:
# <http://www.apache.org/licenses/LICENSE-2.0>.
#
# [This file includes modifications made by New Vector Limited]
#
#

import logging
import re
from collections import Counter
from http import HTTPStatus
from typing import TYPE_CHECKING, Any, Mapping

from pydantic import StrictBool, StrictStr, field_validator

from synapse.api.auth.mas import MasDelegatedAuth
from synapse.api.errors import (
    Codes,
    InteractiveAuthIncompleteError,
    InvalidAPICallError,
    SynapseError,
)
from synapse.http.server import HttpServer
from synapse.http.servlet import (
    RestServlet,
    parse_integer,
    parse_json_object_from_request,
    parse_string,
    validate_json_object,
)
from synapse.http.site import SynapseRequest
from synapse.logging.opentracing import set_tag
from synapse.rest.client._base import client_patterns, interactive_auth_handler
from synapse.types import JsonDict, StreamToken
from synapse.types.rest import RequestBodyModel
from synapse.util.cancellation import cancellable

if TYPE_CHECKING:
    from synapse.server import HomeServer

logger = logging.getLogger(__name__)


class KeyUploadServlet(RestServlet):
    """
    POST /keys/upload HTTP/1.1
    Content-Type: application/json

    {
        "device_keys": {
            "user_id": "<user_id>",
            "device_id": "<device_id>",
            "algorithms": [
                "m.olm.curve25519-aes-sha2",
            ]
            "keys": {
                "<algorithm>:<device_id>": "<key_base64>",
            },
            "signatures:" {
                "<user_id>" {
                    "<algorithm>:<device_id>": "<signature_base64>"
                }
            }
        },
        "fallback_keys": {
            "<algorithm>:<device_id>": "<key_base64>",
            "signed_<algorithm>:<device_id>": {
                "fallback": true,
                "key": "<key_base64>",
                "signatures": {
                    "<user_id>": {
                        "<algorithm>:<device_id>": "<key_base64>"
                    }
                }
            }
        }
        "one_time_keys": {
            "<algorithm>:<key_id>": "<key_base64>"
        },
    }

    response, e.g.:

    {
        "one_time_key_counts": {
            "curve25519": 10,
            "signed_curve25519": 20
        }
    }

    """

    PATTERNS = client_patterns("/keys/upload$")
    CATEGORY = "Encryption requests"

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.auth = hs.get_auth()
        self.e2e_keys_handler = hs.get_e2e_keys_handler()
        self.device_handler = hs.get_device_handler()
        self._clock = hs.get_clock()
        self._store = hs.get_datastores().main

    class KeyUploadRequestBody(RequestBodyModel):
        """
        The body of a `POST /_matrix/client/v3/keys/upload` request.

        Based on https://spec.matrix.org/v1.16/client-server-api/#post_matrixclientv3keysupload.
        """

        class DeviceKeys(RequestBodyModel):
            algorithms: list[StrictStr]
            """The encryption algorithms supported by this device."""

            device_id: StrictStr
            """The ID of the device these keys belong to. Must match the device ID used when logging in."""

            keys: Mapping[StrictStr, StrictStr]
            """
            Public identity keys. The names of the properties should be in the
            format `<algorithm>:<device_id>`. The keys themselves should be encoded as
            specified by the key algorithm.
            """

            signatures: Mapping[StrictStr, Mapping[StrictStr, StrictStr]]
            """Signatures for the device key object. A map from user ID, to a map from "<algorithm>:<device_id>" to the signature."""

            user_id: StrictStr
            """The ID of the user the device belongs to. Must match the user ID used when logging in."""

        class KeyObject(RequestBodyModel):
            key: StrictStr
            """The key, encoded using unpadded base64."""

            fallback: StrictBool | None = False
            """Whether this is a fallback key. Only used when handling fallback keys."""

            signatures: Mapping[StrictStr, Mapping[StrictStr, StrictStr]]
            """Signature for the device. Mapped from user ID to another map of key signing identifier to the signature itself.

            See the following for more detail: https://spec.matrix.org/v1.16/appendices/#signing-details
            """

        device_keys: DeviceKeys | None = None
        """Identity keys for the device. May be absent if no new identity keys are required."""

        @field_validator("device_keys", mode="before")
        @classmethod
        def validate_device_keys_not_null(cls, v: Any) -> Any:
            """Reject explicit `null` for `device_keys` while still allowing
            the field to be omitted (in which case the default `None` is used).

            The spec says `device_keys` may be omitted, but when present it
            must be a `DeviceKeys` object — not `null`.

            Pydantic's experimental `Missing` sentinel would be a cleaner way
            to express this, but it's not stable yet:
            https://docs.pydantic.dev/latest/concepts/experimental/#missing-sentinel
            """
            if v is None:
                raise ValueError("device_keys must not be null")
            return v

        fallback_keys: Mapping[StrictStr, StrictStr | KeyObject] | None = None
        """
        The public key which should be used if the device's one-time keys are
        exhausted. The fallback key is not deleted once used, but should be
        replaced when additional one-time keys are being uploaded. The server
        will notify the client of the fallback key being used through `/sync`.

        There can only be at most one key per algorithm uploaded, and the server
        will only persist one key per algorithm.

        When uploading a signed key, an additional fallback: true key should be
        included to denote that the key is a fallback key.

        May be absent if a new fallback key is not required.
        """

        @field_validator("fallback_keys", mode="before")
        @classmethod
        def validate_fallback_keys(cls, v: Any) -> Any:
            if v is None:
                return v
            if not isinstance(v, dict):
                raise TypeError("fallback_keys must be a mapping")

            for k in v.keys():
                if not len(k.split(":")) == 2:
                    raise SynapseError(
                        code=HTTPStatus.BAD_REQUEST,
                        errcode=Codes.BAD_JSON,
                        msg=f"Invalid fallback_keys key {k!r}. "
                        'Expected "<algorithm>:<device_id>".',
                    )
            return v

        one_time_keys: Mapping[StrictStr, StrictStr | KeyObject] | None = None
        """
        One-time public keys for "pre-key" messages. The names of the properties
        should be in the format `<algorithm>:<key_id>`.

        The format of the key is determined by the key algorithm, see:
        https://spec.matrix.org/v1.16/client-server-api/#key-algorithms.
        """

        @field_validator("one_time_keys", mode="before")
        @classmethod
        def validate_one_time_keys(cls, v: Any) -> Any:
            if v is None:
                return v
            if not isinstance(v, dict):
                raise TypeError("one_time_keys must be a mapping")

            for k, _ in v.items():
                if not len(k.split(":")) == 2:
                    raise SynapseError(
                        code=HTTPStatus.BAD_REQUEST,
                        errcode=Codes.BAD_JSON,
                        msg=f"Invalid one_time_keys key {k!r}. "
                        'Expected "<algorithm>:<device_id>".',
                    )
            return v

    async def on_POST(self, request: SynapseRequest) -> tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request, allow_guest=True)
        user_id = requester.user.to_string()

        # Parse the request body. Validate separately, as the handler expects a
        # plain dict, rather than any parsed object.
        #
        # Note: It would be nice to work with a parsed object, but the handler
        # needs to encode portions of the request body as canonical JSON before
        # storing the result in the DB. There's little point in converted to a
        # parsed object and then back to a dict.
        body = parse_json_object_from_request(request)
        validate_json_object(body, self.KeyUploadRequestBody)

        device_id = requester.device_id

        if device_id is None:
            raise SynapseError(
                400, "To upload keys, you must pass device_id when authenticating"
            )

        if "device_keys" in body:
            # Validate the provided `user_id` and `device_id` fields in
            # `device_keys` match that of the requesting user. We can't do
            # this directly in the pydantic model as we don't have access
            # to the requester yet.
            #
            # TODO: We could use ValidationInfo when we switch to Pydantic v2.
            # https://docs.pydantic.dev/latest/concepts/validators/#validation-info
            if body["device_keys"]["user_id"] != user_id:
                raise SynapseError(
                    code=HTTPStatus.BAD_REQUEST,
                    errcode=Codes.BAD_JSON,
                    msg="Provided `user_id` in `device_keys` does not match that of the authenticated user",
                )
            if body["device_keys"]["device_id"] != device_id:
                raise SynapseError(
                    code=HTTPStatus.BAD_REQUEST,
                    errcode=Codes.BAD_JSON,
                    msg="Provided `device_id` in `device_keys` does not match that of the authenticated user device",
                )

        result = await self.e2e_keys_handler.upload_keys_for_user(
            user_id=user_id,
            device_id=device_id,
            keys=body,
        )

        return 200, result


class KeyQueryServlet(RestServlet):
    """
    POST /keys/query HTTP/1.1
    Content-Type: application/json
    {
      "device_keys": {
        "<user_id>": ["<device_id>"]
    } }

    HTTP/1.1 200 OK
    {
      "device_keys": {
        "<user_id>": {
          "<device_id>": {
            "user_id": "<user_id>", // Duplicated to be signed
            "device_id": "<device_id>", // Duplicated to be signed
            "valid_until_ts": <millisecond_timestamp>,
            "algorithms": [ // List of supported algorithms
              "m.olm.curve25519-aes-sha2",
            ],
            "keys": { // Must include a ed25519 signing key
              "<algorithm>:<key_id>": "<key_base64>",
            },
            "signatures:" {
              // Must be signed with device's ed25519 key
              "<user_id>/<device_id>": {
                "<algorithm>:<key_id>": "<signature_base64>"
              }
              // Must be signed by this server.
              "<server_name>": {
                "<algorithm>:<key_id>": "<signature_base64>"
    } } } } } }
    """

    PATTERNS = client_patterns("/keys/query$")
    CATEGORY = "Encryption requests"

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.auth = hs.get_auth()
        self.e2e_keys_handler = hs.get_e2e_keys_handler()

    @cancellable
    async def on_POST(self, request: SynapseRequest) -> tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request, allow_guest=True)
        user_id = requester.user.to_string()
        device_id = requester.device_id
        timeout = parse_integer(request, "timeout", 10 * 1000)
        body = parse_json_object_from_request(request)

        device_keys = body.get("device_keys")
        if not isinstance(device_keys, dict):
            raise InvalidAPICallError("'device_keys' must be a JSON object")

        def is_list_of_strings(values: Any) -> bool:
            return isinstance(values, list) and all(isinstance(v, str) for v in values)

        if any(not is_list_of_strings(keys) for keys in device_keys.values()):
            raise InvalidAPICallError(
                "'device_keys' values must be a list of strings",
            )

        result = await self.e2e_keys_handler.query_devices(
            body, timeout, user_id, device_id
        )
        return 200, result


class KeyChangesServlet(RestServlet):
    """Returns the list of changes of keys between two stream tokens (may return
    spurious extra results, since we currently ignore the `to` param).

        GET /keys/changes?from=...&to=...

        200 OK
        { "changed": ["@foo:example.com"] }
    """

    PATTERNS = client_patterns("/keys/changes$")
    CATEGORY = "Encryption requests"

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.auth = hs.get_auth()
        self.device_handler = hs.get_device_handler()
        self.store = hs.get_datastores().main

    @cancellable
    async def on_GET(self, request: SynapseRequest) -> tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request, allow_guest=True)

        from_token_string = parse_string(request, "from", required=True)
        set_tag("from", from_token_string)

        # We want to enforce they do pass us one, but we ignore it and return
        # changes after the "to" as well as before.
        #
        # XXX This does not enforce that "to" is passed.
        set_tag("to", str(parse_string(request, "to")))

        from_token = await StreamToken.from_string(self.store, from_token_string)

        user_id = requester.user.to_string()

        device_list_updates = await self.device_handler.get_user_ids_changed(
            user_id, from_token
        )

        response: JsonDict = {}
        response["changed"] = list(device_list_updates.changed)
        response["left"] = list(device_list_updates.left)

        return 200, response


class OneTimeKeyServlet(RestServlet):
    """
    POST /keys/claim HTTP/1.1
    {
      "one_time_keys": {
        "<user_id>": {
          "<device_id>": "<algorithm>"
    } } }

    HTTP/1.1 200 OK
    {
      "one_time_keys": {
        "<user_id>": {
          "<device_id>": {
            "<algorithm>:<key_id>": "<key_base64>"
    } } } }

    """

    PATTERNS = client_patterns("/keys/claim$")
    CATEGORY = "Encryption requests"

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.auth = hs.get_auth()
        self.e2e_keys_handler = hs.get_e2e_keys_handler()

    async def on_POST(self, request: SynapseRequest) -> tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request, allow_guest=True)
        timeout = parse_integer(request, "timeout", 10 * 1000)
        body = parse_json_object_from_request(request)

        # Generate a count for each algorithm, which is hard-coded to 1.
        query: dict[str, dict[str, dict[str, int]]] = {}
        for user_id, one_time_keys in body.get("one_time_keys", {}).items():
            for device_id, algorithm in one_time_keys.items():
                query.setdefault(user_id, {})[device_id] = {algorithm: 1}

        result = await self.e2e_keys_handler.claim_one_time_keys(
            query, requester.user, timeout, always_include_fallback_keys=False
        )
        return 200, result


class UnstableOneTimeKeyServlet(RestServlet):
    """
    Identical to the stable endpoint (OneTimeKeyServlet) except it allows for
    querying for multiple OTKs at once and always includes fallback keys in the
    response.

    POST /keys/claim HTTP/1.1
    {
      "one_time_keys": {
        "<user_id>": {
          "<device_id>": ["<algorithm>", ...]
    } } }

    HTTP/1.1 200 OK
    {
      "one_time_keys": {
        "<user_id>": {
          "<device_id>": {
            "<algorithm>:<key_id>": "<key_base64>"
    } } } }

    """

    PATTERNS = [re.compile(r"^/_matrix/client/unstable/org.matrix.msc3983/keys/claim$")]
    CATEGORY = "Encryption requests"

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.auth = hs.get_auth()
        self.e2e_keys_handler = hs.get_e2e_keys_handler()

    async def on_POST(self, request: SynapseRequest) -> tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request, allow_guest=True)
        timeout = parse_integer(request, "timeout", 10 * 1000)
        body = parse_json_object_from_request(request)

        # Generate a count for each algorithm.
        query: dict[str, dict[str, dict[str, int]]] = {}
        for user_id, one_time_keys in body.get("one_time_keys", {}).items():
            for device_id, algorithms in one_time_keys.items():
                query.setdefault(user_id, {})[device_id] = Counter(algorithms)

        result = await self.e2e_keys_handler.claim_one_time_keys(
            query, requester.user, timeout, always_include_fallback_keys=True
        )
        return 200, result


class SigningKeyUploadServlet(RestServlet):
    """
    POST /keys/device_signing/upload HTTP/1.1
    Content-Type: application/json

    {
    }
    """

    PATTERNS = client_patterns("/keys/device_signing/upload$", releases=("v3",))

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.hs = hs
        self.auth = hs.get_auth()
        self.e2e_keys_handler = hs.get_e2e_keys_handler()
        self.auth_handler = hs.get_auth_handler()

    @interactive_auth_handler
    async def on_POST(self, request: SynapseRequest) -> tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request)
        user_id = requester.user.to_string()
        body = parse_json_object_from_request(request)

        (
            is_cross_signing_setup,
            master_key_updatable_without_uia,
        ) = await self.e2e_keys_handler.check_cross_signing_setup(user_id)

        # Resending exactly the same keys should just 200 OK without doing a UIA prompt.
        keys_are_different = await self.e2e_keys_handler.has_different_keys(
            user_id, body
        )
        if not keys_are_different:
            return 200, {}

        # The keys are different; is x-signing set up? If no, then this is first-time
        # setup, and that is allowed without UIA, per MSC3967.
        # If yes, then we need to authenticate the change.
        # MSC4190 can skip UIA for replacing cross-signing keys as well.
        if is_cross_signing_setup and not requester.app_service_id:
            # With MSC3861, UIA is not possible. Instead, the auth service has to
            # explicitly mark the master key as replaceable.
            if self.hs.config.mas.enabled:
                if not master_key_updatable_without_uia:
                    assert isinstance(self.auth, MasDelegatedAuth)
                    url = await self.auth.account_management_url()
                    url = f"{url}?action=org.matrix.cross_signing_reset"

                    # We use a dummy session ID as this isn't really a UIA flow, but we
                    # reuse the same API shape for better client compatibility.
                    raise InteractiveAuthIncompleteError(
                        "dummy",
                        {
                            "session": "dummy",
                            "flows": [
                                {"stages": ["m.oauth"]},
                                # The unstable name from MSC4312 should be supported until enough clients have adopted the stable (`m.oauth`) name:
                                {"stages": ["org.matrix.cross_signing_reset"]},
                            ],
                            "params": {
                                "m.oauth": {
                                    "url": url,
                                },
                                "org.matrix.cross_signing_reset": {
                                    "url": url,
                                },
                            },
                            "msg": "To reset your end-to-end encryption cross-signing "
                            f"identity, you first need to approve it at {url} and "
                            "then try again.",
                        },
                    )

            elif self.hs.config.experimental.msc3861.enabled:
                if not master_key_updatable_without_uia:
                    # If MSC3861 is enabled, we can assume self.auth is an instance of MSC3861DelegatedAuth
                    # We import lazily here because of the authlib requirement
                    from synapse.api.auth.msc3861_delegated import MSC3861DelegatedAuth

                    assert isinstance(self.auth, MSC3861DelegatedAuth)

                    uri = await self.auth.account_management_url()
                    if uri is not None:
                        url = f"{uri}?action=org.matrix.cross_signing_reset"
                    else:
                        url = await self.auth.issuer()

                    # We use a dummy session ID as this isn't really a UIA flow, but we
                    # reuse the same API shape for better client compatibility.
                    raise InteractiveAuthIncompleteError(
                        "dummy",
                        {
                            "session": "dummy",
                            "flows": [
                                {"stages": ["m.oauth"]},
                                # The unstable name from MSC4312 should be supported until enough clients have adopted the stable (`m.oauth`) name:
                                {"stages": ["org.matrix.cross_signing_reset"]},
                            ],
                            "params": {
                                "m.oauth": {
                                    "url": url,
                                },
                                "org.matrix.cross_signing_reset": {
                                    "url": url,
                                },
                            },
                            "msg": "To reset your end-to-end encryption cross-signing "
                            f"identity, you first need to approve it at {url} and "
                            "then try again.",
                        },
                    )

            else:
                # Without MSC3861, we require UIA.
                await self.auth_handler.validate_user_via_ui_auth(
                    requester,
                    request,
                    body,
                    "reset the device signing key on your account",
                    # Do not allow skipping of UIA auth.
                    can_skip_ui_auth=False,
                )

        result = await self.e2e_keys_handler.upload_signing_keys_for_user(user_id, body)
        return 200, result


class SignaturesUploadServlet(RestServlet):
    """
    POST /keys/signatures/upload HTTP/1.1
    Content-Type: application/json

    {
      "@alice:example.com": {
        "<device_id>": {
          "user_id": "<user_id>",
          "device_id": "<device_id>",
          "algorithms": [
            "m.olm.curve25519-aes-sha2",
            "m.megolm.v1.aes-sha2"
          ],
          "keys": {
            "<algorithm>:<device_id>": "<key_base64>",
          },
          "signatures": {
            "<signing_user_id>": {
              "<algorithm>:<signing_key_base64>": "<signature_base64>>"
            }
          }
        }
      }
    }
    """

    PATTERNS = client_patterns("/keys/signatures/upload$")

    def __init__(self, hs: "HomeServer"):
        super().__init__()
        self.auth = hs.get_auth()
        self.e2e_keys_handler = hs.get_e2e_keys_handler()

    async def on_POST(self, request: SynapseRequest) -> tuple[int, JsonDict]:
        requester = await self.auth.get_user_by_req(request, allow_guest=True)
        user_id = requester.user.to_string()
        body = parse_json_object_from_request(request)

        result = await self.e2e_keys_handler.upload_signatures_for_device_keys(
            user_id, body
        )
        return 200, result


def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
    KeyUploadServlet(hs).register(http_server)
    KeyQueryServlet(hs).register(http_server)
    KeyChangesServlet(hs).register(http_server)
    OneTimeKeyServlet(hs).register(http_server)
    if hs.config.experimental.msc3983_appservice_otk_claims:
        UnstableOneTimeKeyServlet(hs).register(http_server)
    SigningKeyUploadServlet(hs).register(http_server)
    SignaturesUploadServlet(hs).register(http_server)
