Module shared 

The device-shadow state machine shared by the IoT Data Plane handlers: deep-merge with null-deletion semantics, state.delta computation, per-leaf metadata timestamp stamping, and epoch-time helpers.

Kept in one place so update / get / delete cannot diverge on the shadow document’s wire shape.

Functions

compute_delta

Compute state.delta: the subset of desired whose value differs from reported (a leaf missing from reported, or nested objects that differ). Returns None when there is no difference.

merge_into

Deep-merge patch into target. A null leaf in patch deletes that key from target (AWS shadow semantics); nested objects merge recursively; every other value overwrites.

now_millis

Current time as epoch milliseconds. Retained-message lastModifiedTime is epoch millis.

now_secs

Current time as epoch seconds. AWS shadow timestamp / metadata leaves are epoch seconds.

stamp_metadata

Stamp per-leaf metadata timestamps for every leaf touched by patch. A null leaf in patch removes the corresponding metadata leaf; objects recurse; arrays become an array of { "timestamp": ts } (one per element); scalars become { "timestamp": ts }.