# Runtime Flows

Critical mutation paths, deduplication logic, and cross-entity side effects.
Update this file in the same commit as any change to the flows below.

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## 1. Configuration save (create/update)

1. Handler receives JSON body; validates via `ShouldBindJSON`.
2. `LocalConfigurationService.Create` or `Update` is called.
3. Service computes `total_price` from `req.Items.Total()` (sum of `unit_price * quantity` per item).
4. A new revision snapshot is created via `createWithVersion`; revision number increments.
5. `quoteService.RecordUsage` is called best-effort (warn on failure, do not abort save).
6. Configuration row written to SQLite (`local_configurations`); version row appended to `local_configuration_versions`.
7. Pending change queued in `pending_changes` for later sync push.

**DO NOT** read prices from `local_components` during save - prices must already be on items.
**DO NOT** skip version creation on rename/reorder/project-move - those operations call different paths that must NOT call `createWithVersion`.

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## 2. Refresh prices (POST /api/configs/:uuid/refresh-prices)

1. Handler calls `LocalConfigurationService.RefreshPricesNoAuth(uuid, pricelistServerID)`.
2. If online, `SyncPricelistsIfNeeded` runs best-effort (warn on failure, do not block).
3. Resolves target pricelist in order:
   a. Explicitly requested pricelist (`pricelistServerID` param).
   b. Pricelist stored in configuration row (`localCfg.PricelistID`).
   c. Latest local pricelist as fallback.
4. For each item in the config, looks up price from `local_pricelist_items` via `GetLocalPricesForLots` (batch, single query).
5. Items with matching prices are updated; items with no price keep their existing `unit_price`.
6. Updated configuration saved as a new version (same flow as §1 from step 4 onward).

**DO NOT** read prices from `qt_pricelist_items` (MariaDB) directly - prices come from SQLite cache only.

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## 3. Pricelist sync (POST /api/sync/pricelists)

1. Readiness guard checked; returns 423 if guard blocks sync.
2. `SyncService.SyncPricelists` pulls from `qt_pricelists` and `qt_pricelist_items` (MariaDB).
3. For each pricelist: header upserted first, then items replaced atomically via `ReplaceLocalPricelistItems`.
4. After all pricelists: `RecalculateAllLocalPricelistUsage` marks which pricelists are referenced by active configurations.
5. Sync result (status, error, timestamp) written to `app_settings` via `SetPricelistSyncResult`.

**DO NOT** write pricelist header without items in the same transaction - must be atomic.
**DO NOT** query MariaDB from runtime handlers outside sync/setup flows.

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## 4. Vendor spec apply (POST /api/configs/:uuid/vendor-spec/apply)

1. Incoming `items[]` (lot_name, quantity, unit_price) replace the configuration's `items` entirely.
2. New item list saved through `LocalConfigurationService.UpdateItemsNoAuth`.
3. A new revision is created reflecting the BOM-derived item state.

**DO NOT** apply vendor spec without going through the service layer - handler must not write items directly to DB.

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## 5. Configuration versioning invariants

- `local_configuration_versions` is append-only; rows are never updated or deleted.
- Version deduplication: if new snapshot hash equals current head, no new version is created.
- Rollback = create new HEAD revision from old snapshot data (does not restore version pointer to old row).
- UI must always show "main" (implicit head) as the active state; never point to a numbered revision after save.
- Operations that do NOT create a new version: rename, reorder within project, project move, pricelist selector change only.

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## 6. Pending changes queue

- Every local write (create/update/delete) appends a row to `pending_changes`.
- `POST /api/sync/push` drains the queue by writing to MariaDB.
- If a push fails, `increment_attempts` and `last_error` are updated; row stays in queue.
- `RepairPendingChanges` reconciles orphaned changes (configuration/project deleted locally).

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## 7. Error handling boundary rules

- Handlers: log 500 responses with `slog.Error`; surface error message via `RespondError`.
- Services: wrap errors with `fmt.Errorf("context: %w", err)`; do NOT log inside service.
- Repositories: return raw errors; no logging.
- Best-effort operations (usage stats, background sync): log `slog.Warn` and continue.
