🤔 [ISSUE] - attached Blocks infinite loop

[medtaher123]

Description:

A block can either have:

1. Next blocks (linked with a single arrow) — These are blocks with trigger conditions. Only one will be called after the user sends a message.
2. An attached block (linked with a double arrow) — This block is called automatically without any triggers.
   A block cannot have both nextBlocks and an attachedBlock.

Current Issue:

• The user can attach a block to itself, potentially causing an infinite loop if the block triggers itself continuously. This was partially handled in a previous PR (the check exists only on the frontend but not the backend).

Problem:

• Generalized issue: The same problem can occur when two or more blocks are attached to each other, forming an infinite loop (e.g., Block A attaches to Block B, and Block B attaches back to Block A).

Solution:

To prevent this, we need to:

1- Add a check in the backend API to detect and prevent circular attachments.
2- Add a check in the frontend to detect this issue as well.
3- Optionally, in the frontend, display a warning toast when the user attempts to complete the final link that would create a circular reference.

Circular Attachment Detection Algorithm:

1. Start at the source block and check if it has an attached block (the destination block).
2. Follow the chain: For each destination block, check if it also has an attached block.
3. Two possible outcomes:
   • No circular loop: The chain reaches a block with no attached block (valid scenario, the link is accepted).
   • Circular loop detected: The chain loops back to the original source block (invalid scenario, the link is rejected).

Reproduction steps

1. Go to visual editor
2. link a block A to a block B (with the double arrow)
3. link a block B to a block A (also with the double arrow)
4. trigger one of these two blocks in a conversation
5. see infinite loop
to stop the loop you can simply break it by removing one of the blocks or a link

Logs

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OS

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