Implemented epics read/write

internal/server/ws.go

@@ -163,6 +163,12 @@ func (c *wsClient) dispatchLoop(ctx context.Context) {
 	for {
 		select {
 		case u := <-c.updateCh:
+			if u.Value.MetaUpdate {
+				// Datasource refreshed metadata (e.g. after channel connected).
+				// Re-send the meta message so the client gets accurate type/unit info.
+				c.sendMeta(ctx, u.Ref)
+				continue
+			}
 			msg := outMsg{
 				Type:    "update",
 				DS:      u.Ref.DS,
@@ -265,6 +271,7 @@ func (c *wsClient) handleUnsubscribe(refs []sigRef) {
 func (c *wsClient) handleWrite(ctx context.Context, msg inMsg) {
 	ds, ok := c.broker.Source(msg.DS)
 	if !ok {
+		c.log.Warn("write: unknown data source", "ds", msg.DS, "name", msg.Name)
 		c.sendError(ctx, "NOT_FOUND", "unknown data source: "+msg.DS)
 		return
 	}
@@ -272,10 +279,12 @@ func (c *wsClient) handleWrite(ctx context.Context, msg inMsg) {
 	// Enforce write permission before touching the value payload.
 	meta, err := ds.GetMetadata(ctx, msg.Name)
 	if err != nil {
+		c.log.Warn("write: GetMetadata failed", "ds", msg.DS, "name", msg.Name, "err", err)
 		c.sendError(ctx, "NOT_FOUND", "unknown signal: "+msg.Name)
 		return
 	}
 	if !meta.Writable {
+		c.log.Warn("write: signal not writable", "ds", msg.DS, "name", msg.Name)
 		c.sendError(ctx, "NOT_WRITABLE", "signal is read-only: "+msg.Name)
 		return
 	}
@@ -283,12 +292,15 @@ func (c *wsClient) handleWrite(ctx context.Context, msg inMsg) {
 	// Decode the JSON value as the appropriate Go type.
 	var value any
 	if err := json.Unmarshal(msg.Value, &value); err != nil {
+		c.log.Warn("write: parse error", "ds", msg.DS, "name", msg.Name, "err", err)
 		c.sendError(ctx, "PARSE_ERROR", "invalid value: "+err.Error())
 		return
 	}
 
+	c.log.Info("write", "ds", msg.DS, "name", msg.Name, "value", value)
 	metrics.IncWrites()
 	if err := ds.Write(ctx, msg.Name, value); err != nil {
+		c.log.Warn("write: ds.Write failed", "ds", msg.DS, "name", msg.Name, "err", err)
 		c.sendError(ctx, "WRITE_ERROR", err.Error())
 	}
 }