Add first (faulty) design of Timeline

src/Internal/Values/Timeline.elm

@@ -44,19 +44,67 @@ and maintain this room state.
 -}
 
 import Internal.Filter.Timeline as Filter exposing (Filter)
-
-
-{-| The Timeline type represents the timeline state in a Matrix room.
--}
-type Timeline
-    = Timeline
+import Internal.Tools.Mashdict as Mashdict exposing (Mashdict)
+import Internal.Tools.Iddict as Iddict exposing (Iddict)
+import FastDict as Dict exposing (Dict)
+import Set exposing (Set)
 
 
 {-| A batch is a batch of events that is placed onto the Timeline. Functions
 that require an insertion, generally require this data type.
 -}
 type Batch
-    = Batch
+    = StartOfTimeline
+    | BatchToken String
+    | BatchSlice Batch (List String) Filter String
+
+{-| Internal batch that's being saved by the Timeline to track a list of events.
+-}
+type alias IBatch =
+    { events : List String
+    , filter : Filter
+    , start : ITokenPTR
+    , end : ITokenPTR
+    }
+
+{-| Pointer to an IBatch in the Timeline.
+-}
+type IBatchPTR = IBatchPTR Int
+
+{-| Internal token value that's being stored by the Timeline.
+
+If name is `Nothing`, it indicates the start of the timeline.
+-}
+type alias IToken =
+    { name : Maybe String
+    , starts : Set Int      -- This itoken starts the following batches
+    , ends : Set Int        -- This itoken ends the following batches
+    , inFrontOf : Set Int   -- This itoken is in front of the following tokens
+    , behind : Set Int      -- This itoken is behind the following tokens
+    }
+
+{-| Pointer to an IToken in the Timeline.
+-}
+type ITokenPTR = ITokenPTR String
+
+{-| The Timeline type represents the timeline state in a Matrix room.
+
+Following the description of the Matrix spec, a timeline contains the following
+items:
+
+- Events that indicate timeline events
+- Batch values that can be used to paginate through the timeline
+
+The topological shape of the timeline makes older API responses somewhat
+unreliable - as a result,
+
+-}
+type Timeline
+    = Timeline
+        { batches : Iddict IBatch
+        , mostRecentSync : ITokenPTR
+        , tokens : Mashdict IToken
+        }
 
 
 {-| When syncing a Matrix room to its most recent state, add the most recent
@@ -66,19 +114,52 @@ addSync : Batch -> Timeline -> Timeline
 addSync _ timeline =
     timeline
 
+{-| Connect two tokens to each other, revealing their relative location.
+-}
+connectITokentoIToken : ITokenPTR -> ITokenPTR -> Timeline -> Timeline
+connectITokentoIToken (ITokenPTR early) (ITokenPTR late) (Timeline tl) =
+    Timeline
+        { tl
+        | tokens =
+            tl.tokens
+                |> Iddict.map early
+                    (\data ->
+                        { data | behind = Set.insert late data.behind }
+                    )
+                |> Iddict.map late
+                    (\data -> 
+                        { data | inFrontOf = Set.insert early data.inFrontOf }
+                    )
+        }
 
 {-| Create a new empty timeline.
 -}
 empty : Timeline
 empty =
-    Timeline
+    case Iddict.singleton Nothing of
+        ( key, iddict ) ->
+            Timeline
+                { batches = Iddict.empty
+                , mostRecentSync = ITokenPTR key
+                , tokens = iddict
+                , tokenToPtr = Dict.empty
+                }
 
+{-| Get an IBatch from the Timeline.
+-}
+getIBatch : IBatchPTR -> Timeline -> Maybe IBatch
+getIBatch (IBatchPTR ptr) (Timeline { batches }) =
+    Iddict.get ptr batches
+
+getITokenFromPTR : ITokenPTR -> Timeline -> Maybe IToken
+getITokenFromPTR (ITokenPTR ptr) ( Timeline { tokens }) =
+    Iddict.get ptr tokens
 
 {-| Turn a single token into a batch.
 -}
 fromToken : String -> Batch
-fromToken _ =
-    Batch
+fromToken token =
+    BatchToken token
 
 
 {-| Turn a slice of events into a batch.
@@ -88,15 +169,92 @@ connected until the start of the timeline.
 
 -}
 fromSlice : { start : Maybe String, events : List String, filter : Filter, end : String } -> Batch
-fromSlice _ =
-    Batch
+fromSlice data =
+    BatchSlice
+        ( case data.start of
+                Just s ->
+                    BatchToken s
+                
+                Nothing ->
+                    StartOfTimeline
+        )
+        data.events data.filter data.end
 
 
 {-| Insert a batch anywhere else in the timeline.
 -}
 insert : Batch -> Timeline -> Timeline
-insert _ timeline =
-    timeline
+insert batch (Timeline tl) =
+    (Timeline tl)
+
+-- {-| Insert a batch anywhere else in the timeline, and gain a ptr to its
+-- location.
+-- -}
+-- insertBatch : Batch -> Timeline -> { start : ITokenPTR, end : ITokenPTR, tl : Timeline }
+-- insertBatch batch (Timeline tl) =
+--     case batch of
+--         StartOfTimeline ->
+--             case Iddict.insert Nothing tl.tokens of
+--                 ( key, iddict ) ->
+--                     { start = ITokenPTR key
+--                     , end = ITokenPTR key
+--                     , tl = Timeline { tl | tokens = iddict }
+--                     }
+        
+--         BatchToken token ->
+--             -- TODO: Do not insert if it already exists
+--             case Iddict.insert (Just token) tl.tokens of
+--                 ( key, iddict ) ->
+--                     { start = ITokenPTR key
+--                     , end = ITokenPTR key
+--                     , tl = Timeline
+--                             { tl
+--                             | tokens = iddict
+--                             , tokenToPtr =
+--                                 Dict.insert token (ITokenPTR key) tl.tokenToPtr
+--                             }
+--                     }
+        
+--         BatchSlice prevBatch events filter end ->
+--             -- Insert previous batch
+--             case insertBatch prevBatch (Timeline tl) of
+--                 result ->
+--                     case result.tl of
+--                         (Timeline tl2) ->
+--                             { start = result.start
+--                             , end = 
+--                             }
+
+{-| Insert an internal batch into the timeline, and determine its result.
+-}
+insertIBatch : IBatch -> Timeline -> ( IBatchPTR, Timeline )
+insertIBatch ibatch (Timeline tl) =
+    case Iddict.insert ibatch tl.batches of
+        ( key, iddict ) ->
+            ( IBatchPTR key, Timeline { tl | batches = iddict } )
+
+insertIToken : IToken -> Timeline -> ( ITokenPTR, Timeline )
+insertIToken itoken (Timeline tl) =
+    case Maybe.andThen (\n -> Dict.get n tl.tokenToPtr) itoken.name of
+        -- Already exists: merge
+        Just ((ITokenPTR ptr) as pointer) ->
+            ( pointer
+            , Timeline
+                { tl
+                | tokens =
+                    Iddict.map ptr
+                        (\data ->
+                            { name = data.name
+                            , 
+                            }
+                        )
+                }
+            )
+
+        -- Doesn't exist yet: insert!
+        Nothing ->
+            (ITokenPTR 0, Timeline tl)
+
 
 
 {-| Under a given filter, find the most recent events.