dudeswave2/dudeswave/src/dudeswave_auth.erl

%
% Copyright (c) 2024 Andrea Biscuola <a@abiscuola.com>
%
% Permission to use, copy, modify, and distribute this software for any
% purpose with or without fee is hereby granted, provided that the above
% copyright notice and this permission notice appear in all copies.
%
% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
%
-module(dudeswave_auth).
-moduledoc """
Dudes users management module.

Here lives all the functions needed to create, update and delete users
from the dudeswave database.
""".

-define(RANDBYTES, 32).
-define(DEFVALIDITY, 365).

-include_lib("storage/include/storage.hrl").

-export([authenticate/3, authenticate/4, details/2, new/4,
    update/5, delete/2]).

-doc """
Verify a session with an existing cookie.

Spec:

```
-spec authenticate(User, Cookie, Bucket) -> true | false | {error, Reason} when
	User :: binary(),
	Cookie :: binary(),
	Bucket :: atom(),
	Reason :: term().
```

Check against che `Bucket` table, containing the list of current cookies,
if `Cookie` is still valid to authenticate `User` session.
""".
-spec authenticate(User, Cookie, Bucket) -> true | false | {error, Reason} when
	User :: binary(),
	Cookie :: binary(),
	Bucket :: atom(),
	Reason :: term().

authenticate(User, Cookie, Bucket) ->
	case storage:read(Bucket, Cookie) of
		{ok, [R]} ->
			CurTime = calendar:now_to_universal_time(erlang:timestamp()),
			CookieTime = R#object.value,
			CookieUser = lists:keyfind(user, 1, R#object.metadata),

			if
				CookieTime >= CurTime ->
					if
						User =:= CookieUser -> true;
						true -> false
					end;
				true -> false
			end;
		{ok, []} -> false;
		{error, _} -> {error, service_unavailable}
	end.

-doc """
Authenticate a user and return a new cookie for the new session.

Spec:

```
-spec authenticate(User, Password, Cookies, Bucket) -> {true, Cookie, Validity} |
    false | {error, Reason} when
	User :: binary(),
	Password :: binary(),
	Cookies :: atom(),
	Bucket :: atom(),
	Cookie :: binary(),
	Validity :: non_neg_integer(),
	Reason :: term().
```

Authenticate `User` with `Password`, reading the user's details from `Bucket`.

If the authentication is successful, a new cookie is generated and stored in
the `Cookies` bucket. The cookie is returned to the caller in a tuple `{true, Cookie}`,
otherwise `false` is returned and the authentication is denied.
""".
-spec authenticate(User, Password, Cookies, Bucket) -> {true, Cookie, Validity} |
    false | {error, Reason} when
	User :: binary(),
	Password :: binary(),
	Cookies :: atom(),
	Bucket :: atom(),
	Cookie :: binary(),
	Validity :: non_neg_integer(),
	Reason :: term().

authenticate(User, Password, Cookies, Bucket) ->
	case storage:read(Bucket, User) of
		{ok, [R]} ->
			Validity = case application:get_env(cookie_validity) of
				{ok, Value} ->
				    erlang:system_time(seconds) + Value * 86400;
				undefined ->
				    erlang:system_time(seconds) + ?DEFVALIDITY * 86400
			end,

			{ok, Hash} = lists:keyfind(hash, 1, R#object.metadata),
			{ok, Salt} = lists:keyfind(salt, 1, R#object.metadata),
			Auth = crypto:hash(sha256, <<Password/binary, Salt/binary>>),

			if
				Auth =:= Hash ->
					Cookie = base64:encode(rand:bytes(64)),
					case storage:write(Cookies, <<Cookie/binary>>, Validity, [{user, User}]) of
						ok -> {true, Cookie, Validity};
						{error, Reason} -> {error, Reason}
					end;
				true -> false
			end;
		{ok, []} -> false;
		{error, Reason} -> {error, Reason}
	end.

-doc """
Return user details.

Spec:

```
-spec details(User, Bucket) -> Value | {error, Reason} when
	User :: binary(),
	Bucket :: atom(),
	Value :: term(),
	Reason :: term().
```
""".
-spec details(User, Bucket) -> Value | {error, Reason} when
	User :: binary(),
	Bucket :: atom(),
	Value :: term(),
	Reason :: term().

details(User, Bucket) ->
	case storage:read(Bucket, User) of
		{ok, [R]} -> R#object.value;
		{error, Reason} -> {error, Reason};
		{ok, []} -> {error, not_found}
	end.

-doc """
Create a new user.

Spec:

```
-spec new(User, Password, Email, Bucket) -> ok | {error, Reason} when
	User :: binary(),
	Password :: binary(),
	Email :: binary(),
	Bucket :: atom(),
	Reason :: term().
```

The `User` is added to `Bucket`, that is, the users bucket for the application.
`Password` is salted and hashed with SHA256 before being stored.

The new user is saved with a metadata `status` of `waiting_confirmation`,
based on the application settings, the confirmation method may vary.
""".
-spec new(User, Password, Email, Bucket) -> ok | {error, Reason} when
	User :: binary(),
	Password :: binary(),
	Email :: binary(),
	Bucket :: atom(),
	Reason :: term().

new(User, Password, Email, Bucket) ->
	Salt = rand:bytes(?RANDBYTES),
	Hash = crypto:hash(sha256, <<Password/binary, Salt/binary>>),

	Data = #{<<"email">> => Email},
	Metadata = [{salt, Salt}, {hash, Hash}, {status, waiting_confirmation}],

	storage:write(Bucket, User, Data, Metadata).

-doc """
Update user's details

Spec:

```
-spec update(User, Name, Email, Desc, Bucket) -> ok | {error, Reason} when
	User :: binary(),
	Name :: binary(),
	Email :: binary(),
	Desc :: binary(),
	Bucket :: atom(),
	Reason :: term().
```

The details apart from `User` are updated. The username itself is immutable
and cannot be modified. All the other fields, excluding the e-mail, are the
ones that can be seen in the public page.
""".
-spec update(User, Name, Email, Desc, Bucket) -> ok | {error, Reason} when
	User :: binary(),
	Name :: binary(),
	Email :: binary(),
	Desc :: binary(),
	Bucket :: atom(),
	Reason :: term().

update(User, Name, Email, Desc, Bucket) ->
	{ok, CurData, Metadata} = case storage:read(Bucket, User) of
		{ok, [R]} ->
			{ok, R#object.value, R#object.metadata};
		{error, Reason} -> {error, Reason}
	end,

	Data = CurData#{<<"email">> => Email, <<"name">> => Name,
	    <<"description">> => Desc},

	storage:write(Bucket, User, Data, Metadata).

-doc """
Delete an existing user from the database.

```
-spec delete(User, Bucket) -> ok | {error, Reason} when
	User :: binary(),
	Bucket :: atom(),
	Reason :: term().
```
""".
-spec delete(User, Bucket) -> ok | {error, Reason} when
	User :: binary(),
	Bucket :: atom(),
	Reason :: term().

delete(User, Bucket) ->
	% We are missing the cleanup of the cookies
	% here. For that, we need to add at least another
	% API to the storage layer.
	storage:delete(Bucket, User).