distributor/docs/internal/state.md

# Destination State

## Purpose

`internal/state` parses, validates, writes, and compares `.distributor.json` destination state.

## Inputs and outputs

Input is JSON destination state plus the current source manifest, pipeline id, destination id, and whether the destination path has unmanaged content. Output is a deterministic comparison outcome and reason.

## State behavior

`.distributor.json` requires:

- `schema_version: 1`
- `pipeline_id`
- `destination_id`
- `published_at`
- `source.manifest`
- `outputs`

`distributor_version` is optional diagnostic metadata. `published_at` parses as RFC3339 and distributor-written state serializes it as RFC3339 UTC.

The embedded `source.manifest` is validated with the same source manifest rules used by `internal/bundle`.

## Outputs

Each output records `path`, `kind`, `source_path`, `sha256`, and `size`. Supported output kinds are `source` and `generated`. Generated outputs require `transform`.

## Comparison

Comparison outcomes cover absent destination state, unmanaged destination content, invalid state, pipeline or destination mismatch, same source manifest, older destination source, newer destination source, same-created digest conflict, and different source id conflict.

## Failure behavior

Invalid JSON, invalid state schema, invalid embedded source manifests, unsafe output paths, unsupported output kinds, missing generated-output transform names, and mismatched pipeline or destination ids produce comparison outcomes that publish planning can turn into fail actions.

## Boundaries

This package does not publish files, delete files, inspect storage backends, or choose transfer policy actions. Publish planning consumes these comparison outcomes later.

## Tests

Before changing destination state behavior, inspect tests under `internal/state`.

## Invariants

- `.distributor.json` is the destination sentinel and state record.
- Embedded source manifests use the same validation rules as source bundles.
- Generated outputs always record a transform id.
- Comparison returns outcomes and reasons; it does not mutate storage.
- `distributor_version` is diagnostic metadata, not a comparison key.