WIP: Better re-assemble

op-node/cmd/batch_decoder/reassemble/reassemble.go

@@ -15,9 +15,10 @@ import (
 
 type ChannelWithMeta struct {
 	ID            derive.ChannelID    `json:"id"`
-	SkippedFrames []FrameWithMetadata `json:"skipped_frames"`
 	IsReady       bool                `json:"is_ready"`
+	InvalidFrames bool                `json:"invalid_frames"`
 	Frames        []FrameWithMetadata `json:"frames"`
+	SkippedFrames []FrameWithMetadata `json:"skipped_frames"`
 }
 
 type FrameWithMetadata struct {
@@ -71,20 +72,78 @@ func Channels(config Config) {
 }
 
 func processFrames(id derive.ChannelID, frames []FrameWithMetadata) ChannelWithMeta {
-	// TO DO: Use the same approach as in derivation.
-	ready := false
+	// This code is roughly copied from rollup/derive/channel.go
+	// We will use that file to reconstruct the batches, but need to implement this manually
+	// to figure out which frames got pruned.
+	var skippedFrames []FrameWithMetadata
+	framesByNumber := make(map[uint16]FrameWithMetadata)
+	closed := false
+	var endFrameNumber, highestFrameNumber uint16
 	for _, frame := range frames {
-		ready = frame.Frame.IsLast || ready
+		if frame.Frame.IsLast && closed {
+			fmt.Println("Trying to close channel twice")
+			skippedFrames = append(skippedFrames, frame)
+			continue
+		}
+		if _, ok := framesByNumber[frame.Frame.FrameNumber]; ok {
+			fmt.Println("Duplicate frame")
+			skippedFrames = append(skippedFrames, frame)
+			continue
+		}
+		if closed && frame.Frame.FrameNumber >= endFrameNumber {
+			fmt.Println("Frame number past the end of the channel")
+			skippedFrames = append(skippedFrames, frame)
+			continue
+		}
+		framesByNumber[frame.Frame.FrameNumber] = frame
+		if frame.Frame.IsLast {
+			endFrameNumber = frame.Frame.FrameNumber
+			closed = true
+		}
+
+		if frame.Frame.IsLast && endFrameNumber < highestFrameNumber {
+			// Do a linear scan over saved inputs instead of ranging over ID numbers
+			for id, prunedFrame := range framesByNumber {
+				if id >= endFrameNumber {
+					skippedFrames = append(skippedFrames, prunedFrame)
+				}
+			}
+			highestFrameNumber = endFrameNumber
+		}
+
+		if frame.Frame.FrameNumber > highestFrameNumber {
+			highestFrameNumber = frame.Frame.FrameNumber
+		}
 	}
+	ready := chReady(framesByNumber, closed, endFrameNumber)
+
 	if !ready {
 		fmt.Printf("Found channel that was not closed: %v\n", id.String())
 	}
 	return ChannelWithMeta{
 		ID:            id,
 		Frames:        frames,
-		SkippedFrames: nil,
+		SkippedFrames: skippedFrames,
 		IsReady:       ready,
+		InvalidFrames: len(skippedFrames) != 0,
+	}
+}
+
+func chReady(inputs map[uint16]FrameWithMetadata, closed bool, endFrameNumber uint16) bool {
+	if !closed {
+		return false
+	}
+	if len(inputs) != int(endFrameNumber)+1 {
+		return false
+	}
+	// Check for contiguous frames
+	for i := uint16(0); i <= endFrameNumber; i++ {
+		_, ok := inputs[i]
+		if !ok {
+			return false
+		}
 	}
+	return true
 }
 
 func transactionsToFrames(txns []fetch.TransactionWithMeta) []FrameWithMetadata {