transform primitives

First-Class Transform Primitives

OmegaEdit changes should converge on one primitive shape:

• DELETE
• INSERT
• OVERWRITE
• REPLACE
• TRANSFORM

Each primitive carries:

• primitive type
• byte range (offset, length)
• data payload

For INSERT, OVERWRITE, and REPLACE, the data payload is replacement bytes. For DELETE, the data payload is exactly the deleted bytes. Small payloads are stored inline; larger payloads are file-backed in the session checkpoint directory. The inline/file-backed threshold defaults to OMEGA_CHANGE_INLINE_PAYLOAD_LIMIT and can be lowered per session with omega_session_set_change_inline_payload_limit(), which keeps tests and low-memory callers from needing large allocations to exercise the file-backed path. That gives undo an inverse payload without replaying history. For OVERWRITE, the primary payload is the replacement bytes and the inverse payload is the bytes that were replaced, including file-backed storage for large ranges. For TRANSFORM, the data payload is JSON with the transform id and JSON arguments, for example:

{"transformId":"builtin:ascii-to-lower","args":{}}

The first implementation step makes omega_change_get_bytes() return the primitive payload. omega_change_get_data() is kept as an alias for callers that want a name tied to the primitive shape.

Large inverse payloads are not copied into memory-backed history. They use a session-owned file-backed payload path, while model segments read payload bytes through the same copy/write helpers regardless of storage.

Undo now applies inverse primitives directly for ordinary edit changes:

• INSERT undo deletes the inserted range.
• DELETE undo inserts the captured delete payload.
• OVERWRITE undo deletes the replacement payload and inserts the captured inverse payload.

Checkpoint-backed transform undo/redo still restores checkpoints.

Open migration steps:

• Promote REPLACE into the native core change kind instead of representing it as a transaction of delete/insert operations.
• Move protobuf change details further toward the same primitive shape by carrying data storage metadata where useful.
• Keep transform metadata accessors as compatibility helpers over the canonical transform JSON payload.
• Scope transform/plugin allocation ownership to the session or operation instead of using process-global maps and locks for payload cleanup.