Reduce data redundancy

[yotsuya]

This PR modifies some data types to reduce data redundancy. The purpose of this PR is to make it easy to maintain the integrity of data when handling notifications.

Changes (UPDATE: see https://github.com/iij-ii/direct-hs/pull/62#issuecomment-440606390)

Implementation

• :new: data Users
  • This is a data type for managing list of User instead of just [User].
  • This has two fields:
    • myself: User for the logged-in user
    • acquaintances: [User] for other users
• data Client
  • clientMe: removed
    • Instead, clientUsers holds me (as myself)
  • clientUsers: data type changed from [User] to Users
• data TalkRoom
  • talkUsers: removed
  • :new: talkUserIds: [UserId] for talk room members
• data Channel
  • channelTalkRoom: removed

Interfaces

	Before	After
setUsers	Client -> [User] -> IO ()	Client -> Users -> IO ()
getUsers	Client -> IO [User]	Client -> IO Users
getMe	Client -> IO (Maybe User)	Client -> IO User
setAcquaintances	-	:new: Client -> [User] -> IO ()
getAcquaintances	-	:new: Client -> IO [User]
talkUsers	TalkRoom -> [User]	:no_entry: removed
getTalkUsers	-	:new: Client -> TalkRoom -> IO Users
channelTalkRoom	Channel -> TalkRoom	:no_entry: removed

[yotsuya]

The initial design of PR was changed by the above discussion. So, I summarized the changes again.

Changes

Implementation

• data Client
  • clientMe: data type changed from Maybe User to User
  • clientUsers: removed
  • clientAcquaintances: :new: [User] for acquaintance users (retrieved by get_acquaintances)
• data TalkRoom
  • talkUsers: removed
  • :new: talkUserIds: [UserId] for talk room members
• data Channel
  • channelTalkRoom: removed

Interfaces

	Before	After
getMe	Client -> IO (Maybe User)	Client -> IO User
setAcquaintances	-	:new: Client -> [User] -> IO ()
getAcquaintances	-	:new: Client -> IO [User]
setUsers	Client -> [User] -> IO ()	:no_entry: removed
talkUsers	TalkRoom -> [User]	:no_entry: removed
getTalkUsers	-	:new: Client -> TalkRoom -> IO Users
channelTalkRoom	Channel -> TalkRoom	:no_entry: removed