# ADR-0007: Sharing and export

## Status

Accepted

## Context

Learners and instructors will want to share projects: an
instructor distributing an exercise, a student attaching a
project to a question, a collaborator sending a snapshot.

The need is real, but committing to a hosted "publish" feature
(account system, server, namespace, moderation) would dwarf the
core app and is not warranted for a teaching tool. We can satisfy
the need entirely with local artifacts and documentation.

## Decision

No hosted publishing feature. Sharing is supported via two
mechanisms:

1. **`export` command.**
   - Available as an app-level command in both input modes
     (ADR-0003).
   - Produces a single zip file containing `project.yaml`,
     `data/`, and `history.log`, **excluding** `playground.db`
     (the recipient rebuilds it on open per ADR-0004).
   - Default output path is the parent directory of the project.
   - Default filename:
     `YYYYMMDD-<projectname>-export-<sequence>.zip`, where
     `YYYYMMDD` is today's local date and `<sequence>` is a
     two-digit zero-padded counter that starts at `01` and is
     incremented to avoid clobbering an existing file in the
     output directory on the same day.
   - An explicit path and/or filename may be given to override
     the default.

2. **Documented recipes.**
   - Each new project includes a `.gitignore` template that
     excludes `playground.db`, so committing a project to git
     yields a clean, diff-friendly history.
   - The user-facing documentation includes recipes for sharing
     via git, email, and direct file transfer.

If real-world usage later reveals friction these mechanisms cannot
solve, a publish feature can be revisited as a separate ADR.

## Consequences

- Zero server-side surface area, zero accounts, zero hosting
  costs.
- Sharing is a power-user-friendly workflow from day one without
  blocking on infrastructure decisions.
- Recipients reconstruct the database deterministically from the
  authoritative text sources — sharing is automatically a
  validation of the rebuild path.
- If a future hosted feature is ever added, this ADR is
  superseded, not extended.