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# Copyright 2020 Hubert Chathi <hubert@uhoreg.ca>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
defmodule Polyjuice.Client.WellKnown do
@moduledoc """
Look up and interpret a server's `.well-known` file.
https://matrix.org/docs/spec/client_server/latest#well-known-uri
"""
@doc """
Get and parse a server's `.well-known` file based on its server name.
If the homeserver information is correct, returns a tuple of the form `{:ok,
homeserver_url, identity_server_url, well_known}`, where
`identity_server_url` is either a string giving the identity server's URL,
`nil` indicating no identity server was specified, or `:fail_error`
indicating an error in fetching the identity server URL; and `well_known` is
the full contents of the well_known file.
This function is essentially equivalent to calling `get_for_server` followed
by `get_homeserver` and `get_identity_server`.
"""
@spec discover_server(server_name :: String.t()) ::
{:ok, String.t(), String.t() | nil | :fail_error, map}
| {:error, :ignore}
| {:error, :fail_prompt}
| {:error, :fail_error}
def discover_server(server_name) when is_binary(server_name) do
with {:ok, json} <- get_for_server(server_name),
{:ok, hs_url} <- get_homeserver(json) do
case get_identity_server(json) do
{:ok, is_url} ->
{:ok, hs_url, is_url, json}
{:error, err} ->
{:ok, hs_url, err, json}
end
else
err ->
err
end
end
@doc """
Get a server's `.well-known` file based on its server name.
"""
@spec get_for_server(server_name :: String.t()) ::
map
| {:error, :ignore}
| {:error, :fail_prompt}
| {:error, :fail_error}
def get_for_server(server_name) when is_binary(server_name) do
url =
%URI{
scheme: "https",
host: server_name,
authority: server_name,
path: "/.well-known/matrix/client",
port: 443
}
|> to_string()
case :hackney.request(:get, url, [], "", follow_redirect: true) do
{:ok, 404, _, _} ->
{:error, :ignore}
{:ok, code, _headers, _client_ref} when code != 200 ->
{:error, :fail_prompt}
{:ok, 200, _headers, client_ref} ->
with {:ok, body} <- :hackney.body(client_ref),
{:ok, %{}} = ret <- Jason.decode(body) do
ret
else
_ ->
{:error, :fail_prompt}
end
_ ->
# if we can't find the server, treat it like a 404
{:error, :ignore}
end
end
@doc """
Get the homeserver that's specified in a `.well-known` file.
"""
@spec get_homeserver(map) :: {:ok, String.t()} | {:error, :fail_error} | {:error, :fail_prompt}
def get_homeserver(%{} = well_known) do
with %{"m.homeserver" => %{"base_url" => base_url}} <- well_known do
with %{host: host, scheme: scheme, path: path} = parsed_url
when host != nil and (scheme == "http" or scheme == "https") <- URI.parse(base_url),
slashed_url =
(if path != nil and !String.ends_with?(path, "/") do
%{parsed_url | path: path <> "/"}
else
parsed_url
end),
{:ok, %{"versions" => v}} when is_list(v) <-
URI.merge(slashed_url, "_matrix/client/versions") |> validate_server() do
{:ok, to_string(slashed_url)}
else
_ -> {:error, :fail_error}
end
else
_ ->
{:error, :fail_prompt}
end
end
@doc """
Get the identity server that's specified in a `.well-known` file.
"""
@spec get_identity_server(map) :: {:ok, String.t()} | {:error, :fail_error}
def get_identity_server(%{} = well_known) do
case well_known do
%{"m.identity_server" => is_info} ->
with %{"base_url" => base_url} <- is_info,
%{host: host, scheme: scheme, path: path} = parsed_url
when host != nil and (scheme == "http" or scheme == "https") <- URI.parse(base_url),
slashed_url =
(if path != nil and !String.ends_with?(path, "/") do
%{parsed_url | path: path <> "/"}
else
parsed_url
end),
{:ok, %{}} <- URI.merge(slashed_url, "_matrix/identity/api/v1") |> validate_server() do
{:ok, to_string(slashed_url)}
else
_ -> {:error, :fail_error}
end
_ ->
{:ok, nil}
end
end
# check that a given URL returns something JSON-y
defp validate_server(%URI{} = url) do
case :hackney.request(:get, to_string(url), [], "", []) do
{:ok, 200, headers, client_ref} ->
with "application/json" <- Polyjuice.Client.Endpoint.get_header(headers, "content-type"),
{:ok, body} <- :hackney.body(client_ref),
{:ok, json} <- Jason.decode(body) do
{:ok, json}
else
_ ->
{:error, :fail_error}
end
_ ->
{:error, :fail_error}
end
end
end
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