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QuoteForge/bible/02-architecture.md

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# 02 — Architecture
## Local-First Principle
**SQLite** is the single source of truth for the user.
**MariaDB** is a sync server only — it never blocks local operations.
```
User
SQLite (qfs.db) ← all CRUD operations go here
│ background sync (every 5 min)
MariaDB (RFQ_LOG) ← pull/push only
```
**Rules:**
- All CRUD operations go through SQLite only
- If MariaDB is unavailable → local work continues without restrictions
- Changes are queued in `pending_changes` and pushed on next sync
---
## Synchronization
### Data Flow Diagram
```
[ SERVER / MariaDB ]
┌───────────────────────────┐
│ qt_projects │
│ qt_configurations │
│ qt_pricelists │
│ qt_pricelist_items │
│ qt_pricelist_sync_status │
└─────────────┬─────────────┘
pull (projects/configs/pricelists)
┌────────────────────┴────────────────────┐
│ │
[ CLIENT A / SQLite ] [ CLIENT B / SQLite ]
local_projects local_projects
local_configurations local_configurations
local_pricelists local_pricelists
local_pricelist_items local_pricelist_items
pending_changes pending_changes
│ │
└────── push (projects/configs only) ─────┘
[ SERVER / MariaDB ]
```
### Sync Direction by Entity
| Entity | Direction |
|--------|-----------|
| Configurations | Client ↔ Server ↔ Other Clients |
| Projects | Client ↔ Server ↔ Other Clients |
| Pricelists | Server → Clients only (no push) |
| Components | Server → Clients only |
Local pricelists not present on the server and not referenced by active configurations are deleted automatically on sync.
### Soft Deletes (Archive Pattern)
Configurations and projects are **never hard-deleted**. Deletion is archive via `is_active = false`.
- `DELETE /api/configs/:uuid` → sets `is_active = false` (archived); can be restored via `reactivate`
- `DELETE /api/projects/:uuid` → archives a project **variant** only (`variant` field must be non-empty); main projects cannot be deleted via this endpoint
## Sync Readiness Guard
Before every push/pull, a preflight check runs:
1. Is the server (MariaDB) reachable?
2. Can centralized local DB migrations be applied?
3. Does the application version satisfy `min_app_version` of pending migrations?
**If the check fails:**
- Local CRUD continues without restriction
- Sync API returns `423 Locked` with `reason_code` and `reason_text`
- UI shows a red indicator with the block reason
---
## Pricing
### Principle
**Prices come only from `local_pricelist_items`.**
Components (`local_components`) are metadata-only — they contain no pricing information.
### Lookup Pattern
```go
// Look up a price for a line item
price, found := s.lookupPriceByPricelistID(pricelistID, lotName)
if found && price > 0 {
// use price
}
// Inside lookupPriceByPricelistID:
localPL, err := s.localDB.GetLocalPricelistByServerID(pricelistID)
price, err := s.localDB.GetLocalPriceForLot(localPL.ID, lotName)
```
### Multi-Level Pricelists
A configuration can reference up to three pricelists simultaneously:
| Field | Purpose |
|-------|---------|
| `pricelist_id` | Primary (estimate) |
| `warehouse_pricelist_id` | Warehouse pricing |
| `competitor_pricelist_id` | Competitor pricing |
Pricelist sources: `estimate` | `warehouse` | `competitor`
### "Auto" Pricelist Selection
Configurator supports explicit and automatic selection per source (`estimate`, `warehouse`, `competitor`):
- **Explicit mode:** concrete `pricelist_id` is set by user in settings.
- **Auto mode:** client sends no explicit ID for that source; backend resolves the current latest active pricelist.
`auto` must stay `auto` after price-level refresh and after manual "refresh prices":
- resolved IDs are runtime-only and must not overwrite user's mode;
- switching to explicit selection must clear runtime auto resolution for that source.
### Latest Pricelist Resolution Rules
For both server (`qt_pricelists`) and local cache (`local_pricelists`), "latest by source" is resolved with:
1. only pricelists that have at least one item (`EXISTS ...pricelist_items`);
2. deterministic sort: `created_at DESC, id DESC`.
This prevents selecting empty/incomplete snapshots and removes nondeterministic ties.
---
## Configuration Versioning
### Principle
Append-only for **spec+price** changes: immutable snapshots are stored in `local_configuration_versions`.
```
local_configurations
└── current_version_id ──► local_configuration_versions (v3) ← active
local_configuration_versions (v2)
local_configuration_versions (v1)
```
- `version_no = max + 1` when configuration **spec+price** changes
- Old versions are never modified or deleted in normal flow
- Rollback does **not** rewind history — it creates a **new** version from the snapshot
- Operational updates (`line_no` reorder, server count, project move, rename)
are synced via `pending_changes` but do **not** create a new revision snapshot
### Rollback
```bash
POST /api/configs/:uuid/rollback
{
"target_version": 3,
"note": "optional comment"
}
```
Result:
- A new version `vN` is created with `data` from the target version
- `change_note = "rollback to v{target_version}"` (+ note if provided)
- `current_version_id` is switched to the new version
- Configuration moves to `sync_status = pending`
### Sync Status Flow
```
local → pending → synced
```
---
## Project Specification Ordering (`Line`)
- Each project configuration has persistent `line_no` (`10,20,30...`) in both SQLite and MariaDB.
- Project list ordering is deterministic:
`line_no ASC`, then `created_at DESC`, then `id DESC`.
- Drag-and-drop reorder in project UI updates `line_no` for active project configurations.
- Reorder writes are queued as configuration `update` events in `pending_changes`
without creating new configuration versions.
- Backward compatibility: if remote MariaDB schema does not yet include `line_no`,
sync falls back to create/update without `line_no` instead of failing.
---
## Sync Payload for Versioning
Events in `pending_changes` for configurations contain:
| Field | Description |
|-------|-------------|
| `configuration_uuid` | Identifier |
| `operation` | `create` / `update` / `rollback` |
| `current_version_id` | Active version ID |
| `current_version_no` | Version number |
| `snapshot` | Current configuration state |
| `idempotency_key` | For idempotent push |
| `conflict_policy` | `last_write_wins` |
---
## Background Processes
| Process | Interval | What it does |
|---------|----------|--------------|
| Sync worker | 5 min | push pending + pull all |
| Backup scheduler | configurable (`backup.time`) | creates ZIP archives |