# CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

## Running the Server

```bash
pipekit serve                          # default host/port from config.yaml
pipekit serve --host 0.0.0.0 --port 8080 --reload   # dev mode with auto-reload
```

The user runs the server themselves in their own terminal — do not nohup or background it.

## Other CLI Commands

```bash
pipekit init                           # create/upgrade SQLite schema
pipekit doctor                         # health check (config, jrunner, DB)
pipekit run <module_name>              # run a module synchronously (manual test)
pipekit set-password <username>        # set HTTP Basic Auth credentials
pipekit secrets set KEY [VALUE]        # add/update a secret (prompts if value omitted)
pipekit drivers list                   # show registered driver kinds
./deploy.sh                            # idempotent: venv, deps, launcher, driver registration
```

## Architecture

Pipekit is a database sync tool. A **module** defines a source query → dest table sync job. The engine runs a module by: resolving watermarks → materializing source SQL → staging data via jrunner → merging into dest.

**Layers (bottom to top):**

1. **SQLite** (`pipekit.db`) — single file, all state
2. **`repo.py`** — all CRUD for every table; ~1,900 LOC, the only layer that touches the DB
3. **`engine/`** — orchestrates a module run: lock acquisition, watermark resolution, jrunner calls, merge SQL, post-run hooks, run_log write, lock release
4. **jrunner** — external Java CLI; handles all JDBC access. Python never talks to remote DBs directly; it shells out to jrunner
5. **`api/`** — FastAPI REST endpoints under `/api/*`, HTTP Basic Auth (except `/health`)
6. **`web/`** — HTML pages (Jinja2 templates) at `/`; HTMX + Alpine.js for interactivity

## Key Data Model

- **driver** — JDBC driver registration (kind, jar, class, url_template)
- **connection** — named DB connection (jdbc_url, username, password as `$ENV_VAR` reference)
- **module** — sync job (source/dest connection, source query, merge strategy, merge key, enabled, running lock)
- **watermark** — named placeholder with resolver SQL; first column of first row used as opaque string; replaces `{watermark_name}` in source query
- **hook** — post-merge SQL (run_order, run_on: success/failure/always)
- **run_log** — immutable history record with resolved SQL, merge SQL, watermark values, stdout/stderr, timing

## Engine Flow

```
run_module(module_id)
  → atomic UPDATE module SET running=1 WHERE running=0  # fail if already locked
  → for each watermark: run resolver SQL via jrunner → capture first cell
  → materialize source query (simple string replace {name} → value)
  → jrunner create staging table (pipekit_staging.{module_name})
  → jrunner migrate source → staging
  → build merge SQL (engine/merge.py: full=truncate+insert, incremental=delete by key+insert, append=insert)
  → run merge SQL via jrunner
  → run hooks in order
  → write run_log entry
  → UPDATE module SET running=0 (in finally)
```

## Credentials Pattern

Passwords in connections are stored as `$VAR_NAME` references. At run time they are resolved from `/etc/pipekit/secrets.env` (override with `PIPEKIT_SECRETS` env var). Config path override: `PIPEKIT_CONFIG`.

## Driver Abstraction

Each driver in `pipekit/drivers/` inherits from `base.py::Driver` and implements: `browse_fields`, `list_tables`, `list_schemas`, `get_columns`, `map_type`, `default_expression`, `quote_identifier`. The wizard UI calls `/api/introspect/*` which dispatches to the appropriate driver.

## Module Columns

Modules store their column mapping as `columns_json` — a JSON list of dicts with keys `source_name`, `source_type`, `dest_name`, `dest_type`. The engine uses this to build the staging CREATE TABLE and the merge INSERT column lists.

## Merge Key

`merge_key` is stored as a comma-separated string (e.g., `"col1, col2"`). The engine parses it and generates a multi-column DELETE predicate for incremental strategy.

## Staging Table

Recreated on every run as `pipekit_staging.{module_name}` (DROP + CREATE, not IF NOT EXISTS). Ephemeral — exists only during the run.

## API vs. Web

- `/api/*` — JSON REST, HTTP Basic Auth, consumed by HTMX fragments and external callers
- `/` and other bare paths — full HTML pages (Jinja2), no auth currently
- `POST /modules/{id}/run` returns `{run_id}` immediately; run is async; poll `/runs/{id}` for status

## Tech Stack

- Python 3.10+, FastAPI, Uvicorn, Jinja2, PyYAML, SQLite3 (stdlib)
- `python-multipart` required for HTML form POSTs (not auto-installed as a FastAPI transitive dep)
- Frontend: HTMX + Alpine.js (CDN), no build step
- jrunner: separate Java tool, must be on PATH

## Full Spec

`/opt/pipekit/SPEC.md` is the authoritative design document. Read it for deep rationale on any architectural decision.