add simple pagination to the ListSwaps command

This commit adds the ability to set a max_swaps and an index_offset
flag to the ListSwaps command. These new fields are applied AFTER
the initial filtering step. The response also now passes additional
information about the index count and total swaps filtered.

Author: kornpow

cmd/loop/swaps.go

@@ -35,6 +35,14 @@ var listSwapsCommand = cli.Command{
 		labelFlag,
 		channelFlag,
 		lastHopFlag,
+		cli.Uint64Flag{
+			Name:  "max_swaps",
+			Usage: "Max number of swaps to return after filtering",
+		},
+		cli.Uint64Flag{
+			Name:  "index_offset",
+			Usage: "index to start listing filtered swaps from",
+		},
 	},
 }
 
@@ -102,6 +110,8 @@ func listSwaps(ctx *cli.Context) error {
 	resp, err := client.ListSwaps(
 		context.Background(), &looprpc.ListSwapsRequest{
 			ListSwapFilter: filter,
+			IndexOffset:    uint32(ctx.Uint("index_offset")),
+			MaxSwaps:       uint32(ctx.Uint("max_swaps")),
 		},
 	)
 	if err != nil {

loopd/swapclient_server.go

@@ -587,7 +587,33 @@ func (s *swapClientServer) ListSwaps(ctx context.Context,
 		rpcSwaps = append(rpcSwaps, rpcSwap)
 		idx++
 	}
-	return &looprpc.ListSwapsResponse{Swaps: rpcSwaps}, nil
+
+	filteredSwapCount := len(rpcSwaps)
+	endIndex := filteredSwapCount
+
+	// Apply pagination if max_swaps or index_offset is specified
+	if req.MaxSwaps > 0 || req.IndexOffset > 0 {
+		// Calculate the end index for pagination
+		endIndex = int(req.IndexOffset + req.MaxSwaps)
+		if endIndex > filteredSwapCount {
+			endIndex = filteredSwapCount
+		}
+
+		// Make sure we don't go out of bounds
+		if int(req.IndexOffset) < filteredSwapCount {
+			rpcSwaps = rpcSwaps[req.IndexOffset:endIndex]
+		} else {
+			// If the offset is beyond the available swaps, return empty
+			rpcSwaps = []*looprpc.SwapStatus{}
+		}
+	}
+	response := looprpc.ListSwapsResponse{
+		Swaps:              rpcSwaps,
+		FirstIndexOffset:   req.IndexOffset,
+		LastIndexOffset:    uint32(endIndex),
+		TotalFilteredSwaps: uint32(filteredSwapCount),
+	}
+	return &response, nil
 }
 
 // filterSwap filters the given swap based on the provided filter.