first version of todo app with toy database

examples/todoapp/todoapp.nim

@@ -1,5 +1,5 @@
 
-import vdom, karax, karaxdsl, jstrutils, components, localstorage
+import vdom, karax, karaxdsl, jstrutils, components, karaxdb/client
 
 type
   Filter = enum
@@ -9,6 +9,12 @@ var
   selectedEntry = -1
   filter: Filter
   entriesLen: int
+  data: Db
+
+registerOnUpdate proc(newDb: Db) =
+  merge(newDb, data)
+  data = newDb
+  redraw()
 
 const
   contentSuffix = cstring"content"
@@ -16,25 +22,23 @@ const
   lenSuffix = cstring"entriesLen"
 
 proc getEntryContent(pos: int): cstring =
-  result = getItem(&pos & contentSuffix)
-  if result == cstring"null":
-    result = nil
+  extract(data, &pos, contentSuffix)
 
 proc isCompleted(pos: int): bool =
-  var value = getItem(&pos & completedSuffix)
+  var value = extract(data, &pos, completedSuffix)
   result = value == cstring"true"
 
 proc setEntryContent(pos: int, content: cstring) =
-  setItem(&pos & contentSuffix, content)
+  insert(data, &pos, contentSuffix, content)
 
 proc markAsCompleted(pos: int, completed: bool) =
-  setItem(&pos & completedSuffix, &completed)
+  insert(data, &pos, completedSuffix, &completed)
 
 proc addEntry(content: cstring, completed: bool) =
   setEntryContent(entriesLen, content)
   markAsCompleted(entriesLen, completed)
   inc entriesLen
-  setItem(lenSuffix, &entriesLen)
+  insert(data, lenSuffix, "equals", &entriesLen)
 
 proc updateEntry(pos: int, content: cstring, completed: bool) =
   setEntryContent(pos, content)
@@ -61,7 +65,7 @@ proc toggleEntry(ev: Event; n: VNode) =
   markAsCompleted(id, not isCompleted(id))
 
 proc onAllDone(ev: Event; n: VNode) =
-  clear()
+  insert(data, lenSuffix, "equals", "0")
   selectedEntry = -1
 
 proc clearCompleted(ev: Event, n: VNode) =
@@ -150,8 +154,5 @@ setOnHashChange(proc(hash: cstring) =
   elif hash == "#/active": filter = active
 )
 
-if hasItem(lenSuffix):
-  entriesLen = parseInt getItem(lenSuffix)
-else:
-  entriesLen = 0
+entriesLen = 0
 setRenderer createDom

src/kajax.nim

@@ -48,3 +48,21 @@ proc ajaxGet*(url: cstring; headers: openarray[(cstring, cstring)];
 
 proc toJson*[T](data: T): cstring {.importc: "JSON.stringify".}
 proc fromJson*[T](blob: cstring): T {.importc: "JSON.parse".}
+
+type
+  MessageEvent* {.importc.} = ref object
+    data*: cstring
+  ErrorEvent* {.importc.} = ref object
+  CloseEvent* {.importc.} = ref object
+    code*: int
+    reason*: cstring
+
+  WebSocket* {.importc.} = ref object
+    onopen*: proc()
+    onmessage*: proc(ev: MessageEvent)
+    onclose*: proc(ev: CloseEvent)
+    onerror*: proc(ev: ErrorEvent)
+
+proc newWebsocket*(url, protocol: cstring): WebSocket {.importc: "new WebSocket".}
+
+proc send*(socket: WebSocket, data: cstring) {.importcpp.}

src/karaxdb/client.nim

@@ -0,0 +1,99 @@
+
+import "../kajax", "../jdict", common
+export common
+from "../karax" import kout
+
+type
+  Db* = ref object
+    data: seq[Triple]
+    version*: int
+    next: Db
+
+  Query* = object
+    constraints*: set[TripleKind]
+    t*: Triple
+
+  Message {.importc.} = ref object
+    kind: MessageKind
+    data: seq[Triple]
+    version: int
+    id: MessageId
+#  RequestMessage {.importc.} = ref object
+
+let conn = newWebSocket("ws://localhost:8080", "karaxdb")
+var gid: MessageId
+var pendingIds = newJDict[MessageId, Message]()
+var pending: int
+
+#proc loadDb*(url: cstring): Db =
+#  result = nil
+
+proc newTransaction*(): Db =
+  result = Db(data: @[])
+
+proc insert*(head, newdb: Db) =
+  newdb.next = head
+  #result = newdb
+  let expectedVersion = if not head.isNil: head.version + 1 else: 1
+  inc gid.int
+  let m = Message(kind: NewData, data: newdb.data, version: expectedVersion, id: gid)
+  pendingIds[gid] = m
+  inc pending
+  conn.send(toJson(m))
+
+proc merge*(newer, older: Db) =
+  newer.next = older
+
+proc registerOnUpdate*(update: proc(db: Db)) =
+  conn.onmessage =
+    proc (e: MessageEvent) =
+      let msg = fromJson[Message](e.data)
+      case msg.kind
+      of Conflict:
+        # conflict, so throw away the sent data, don't apply the changes:
+        if pending > 0:
+          pendingIds.del msg.id
+          dec pending
+        # server sent data that caused the conflict:
+        if msg.data.len > 0:
+          let db = Db(data: msg.data, version: msg.version)
+          update(db)
+      of Accepted:
+        kout cstring"accepted", pending
+        if pending > 0:
+          let d = pendingIds[msg.id]
+          # data was not submitted again, so we use the in-memory version
+          # of the data:
+          let db = Db(data: d.data, version: d.version)
+          pendingIds.del msg.id
+          dec pending
+          update(db)
+      of Newdata:
+        let db = Db(data: msg.data, version: msg.version)
+        update(db)
+
+iterator list*(db: Db, q: Query): Triple =
+  # XXX here the datamodel comes in! We must not
+  # yield outdated data!
+  var it = db
+  while it != nil:
+    for d in it.data:
+      var match = true
+      for k in q.constraints:
+        if d[k] != q.t[k]: match = false
+      if match: yield d
+    it = it.next
+
+proc extract*(db: Db, q: Query): Triple =
+  for x in list(db, q):
+    result = x
+    break
+
+proc extract*(db: Db, subj, pred: kstring): kstring =
+  let q = Query(constraints: {Subj, Pred}, t: [subj, pred, ""])
+  result = extract(db, q)[Obj]
+
+proc insert*(db: Db, subj, pred, obj: kstring) =
+  let result = Db()
+  result.data.add([subj, pred, obj])
+  insert(db, result)

src/karaxdb/common.nim

@@ -0,0 +1,17 @@
+
+when defined(js):
+  type kstring* = cstring
+else:
+  type kstring* = string
+
+type
+  TripleKind* = enum
+    Subj, Pred, Obj
+
+  DbValue* = kstring
+  Triple* = array[TripleKind, DbValue]
+
+  MessageId* = distinct int
+
+  MessageKind* = enum
+    Newdata, Conflict, Accepted

src/karaxdb/server.nim

@@ -0,0 +1,56 @@
+
+import asynchttpserver, asyncdispatch, asyncnet, "../../../websocket/websocket", common, json
+
+type
+  Message = object
+    kind: MessageKind
+    id: MessageId
+    data: seq[Triple]
+    version: int
+
+proc `%`(id: MessageId): JsonNode = %BiggestInt(id)
+proc `%`(k: MessageKind): JsonNode = %BiggestInt(k)
+
+proc triplesFromJson(j: JsonNode): seq[Triple] =
+  result = newSeq[Triple](j.len)
+  var i = 0
+  for t in j:
+    doAssert t.kind == JArray
+    result[i] = [t[0].str, t[1].str, t[2].str]
+    inc i
+
+proc messageFromJson(j: JsonNode): Message =
+  Message(kind: MessageKind(j["kind"].num), id: MessageId(j["id"].num),
+          data: triplesFromJson(j["data"]), version: j["version"].num.int)
+
+var server = newAsyncHttpServer()
+
+proc cb(req: Request) {.async.} =
+  let (success, error) = await(verifyWebsocketRequest(req, "karaxdb"))
+  if not success:
+    echo "WS negotiation failed: " & error
+    await req.respond(Http400, "Websocket negotiation failed: " & error)
+    req.client.close
+  else:
+    echo "New websocket customer arrived!"
+    while true:
+      try:
+        var f = await req.client.readData(false)
+        echo "(opcode: " & $f.opcode & ", data: " & $f.data.len & ")"
+        let m = messageFromJson(f.data.parseJson)
+        let om = Message(kind: Accepted, id: m.id, data: @[], version: m.version)
+        let oms = $(%*om)
+        echo "OUTPUT ", oms
+        if f.opcode == Opcode.Text:
+          waitFor req.client.sendText(oms, false)
+        else:
+          echo "protocol error"
+          #waitFor req.client.sendBinary(f.data, false)
+      except:
+        echo getCurrentExceptionMsg()
+        break
+
+    req.client.close()
+    echo ".. socket went away."
+
+waitFor server.serve(Port(8080), cb)