# Implementation Plan: Plugin Architecture & Svelte Web UI

**Branch**: `001-plugin-arch-svelte-ui` | **Date**: 2025-12-19 | **Spec**: [spec.md](spec.md)
**Input**: Feature specification from `specs/001-plugin-arch-svelte-ui/spec.md`

## Summary

This feature introduces a dual-layer architecture: a Python backend exposing core tools (Backup, Migration, Search) via API, and a Svelte-based Single Page Application (SPA) for user interaction. It also implements a dynamic plugin system allowing developers to extend functionality by adding Python modules to a specific directory without modifying core code.

## Technical Context

**Language/Version**: Python 3.9+ (Backend), Node.js 18+ (Frontend Build)
**Primary Dependencies**: 
- Backend: Flask or FastAPI [NEEDS CLARIFICATION: Choice of web framework], Pydantic (validation), Plugin loader mechanism (importlib)
- Frontend: Svelte, Vite, TailwindCSS (likely for UI)
**Storage**: Filesystem (plugins, logs, backups), SQLite (optional, for job history if needed)
**Testing**: pytest (Backend), vitest/playwright (Frontend)
**Target Platform**: Windows/Linux (Hosted Service)
**Project Type**: Web Application (Backend + Frontend)
**Performance Goals**: UI load < 1s, Log streaming latency < 200ms
**Constraints**: Must run in a hosted environment with ADFS authentication.
**Scale/Scope**: ~5-10 concurrent users, Extensible plugin system.

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

- [x] **Causal Validity**: Do all planned modules have defined Contracts (inputs/outputs/invariants) before implementation logic? (Will be enforced in Phase 1)
- [x] **Immutability**: Are architectural layers and constraints defined in Module Headers? (Will be enforced in Phase 1)
- [x] **Format Compliance**: Does the plan ensure all code will be wrapped in `[DEF]` anchors? (Will be enforced in Phase 1)
- [x] **Belief State**: Is logging planned to follow the `Entry` -> `Validation` -> `Action` -> `Coherence` state transition model? (Will be enforced in Phase 1)

## Project Structure

### Documentation (this feature)

```text
specs/001-plugin-arch-svelte-ui/
├── plan.md              # This file
├── research.md          # Phase 0 output
├── data-model.md        # Phase 1 output
├── quickstart.md        # Phase 1 output
├── contracts/           # Phase 1 output
└── tasks.md             # Phase 2 output
```

### Source Code (repository root)

```text
backend/
├── src/
│   ├── app.py           # Entry point
│   ├── api/             # REST API endpoints
│   ├── core/            # Plugin loader, Task manager
│   ├── plugins/         # Directory for dynamic plugins
│   └── services/        # Auth (ADFS), Logging
└── tests/

frontend/
├── src/
│   ├── components/      # Reusable UI components
│   ├── pages/           # Route views
│   ├── lib/             # API client, Stores
│   └── App.svelte
└── tests/

superset_tool/           # Existing core logic (refactored to be importable by backend)
```

**Structure Decision**: Adopting a standard "Web Application" structure with separated `backend` and `frontend` directories to maintain clean separation of concerns. The existing `superset_tool` library will be preserved and imported by the backend to execute actual tasks.

## Complexity Tracking

| Violation | Why Needed | Simpler Alternative Rejected Because |
|-----------|------------|-------------------------------------|
| N/A | | |
