feat(flyer-import): add session management and retrieval endpoints

- Add new API endpoints for retrieving flyer import sessions:
  - GET /flyer-import/sessions/latest - Retrieve latest session for user
  - GET /flyer-import/sessions/:sessionId - Retrieve specific session
- Implement session persistence and restoration in Flutter UI
- Add toJson() methods to FlyerImportItem and FlyerImportResult for serialization
- Add new FlyerImportSession domain model for local session management
- Add unit test file for FlyerImportService
- Update FlyerImportController with new endpoints and user ID extraction
- Update FlyerImportService with session retrieval logic and response mapping
- Update API paths in Flutter client
- Add session restoration on widget init in FlyerImportTab

backend/src/flyer-import/flyer-import.service.ts

@@ -2,8 +2,9 @@ import {
   BadRequestException,
   Injectable,
   Logger,
+  NotFoundException,
   ServiceUnavailableException,
-} from '@nestjs/common';
+} from '@nestjs/common';
 import { Prisma } from '@prisma/client';
 import { PrismaService } from '../prisma/prisma.service';
 import { normalizeName } from '../common/utils/normalize-name';
@@ -51,7 +52,7 @@ type ProductLite = {
 };
 
 @Injectable()
-export class FlyerImportService {
+export class FlyerImportService {
   private readonly logger = new Logger(FlyerImportService.name);
 
   constructor(
@@ -61,7 +62,7 @@ export class FlyerImportService {
     private readonly normalizer: FlyerNormalizerService,
   ) {}
 
-  async parseAndMatch(file: Express.Multer.File, userId: number): Promise<FlyerImportResponse> {
+  async parseAndMatch(file: Express.Multer.File, userId: number): Promise<FlyerImportResponse> {
     const parsed = await this.parseViaInternal(file);
 
     const [products, aliases] = await Promise.all([
@@ -123,14 +124,47 @@ export class FlyerImportService {
 
     const persistedItems = await this.persistSessionWithItems(userId, parsed.retailer, items);
 
-    return {
-      sessionId: persistedItems.sessionId,
-      retailer: parsed.retailer,
-      parserVersion: parsed.parserVersion,
-      items: persistedItems.items,
-      warnings: parsed.warnings,
-    };
-  }
+    return {
+      sessionId: persistedItems.sessionId,
+      retailer: parsed.retailer,
+      parserVersion: parsed.parserVersion,
+      items: persistedItems.items,
+      warnings: parsed.warnings,
+    };
+  }
+
+  async getSession(sessionId: number, userId: number): Promise<FlyerImportResponse> {
+    const session = await this.prisma.flyerSession.findFirst({
+      where: { id: sessionId, userId },
+      include: { items: { orderBy: { id: 'asc' } } },
+    });
+
+    if (!session) {
+      throw new NotFoundException('Flyer-session hittades inte.');
+    }
+
+    return this.toFlyerImportResponseFromSession(session);
+  }
+
+  async getLatestSession(userId: number): Promise<FlyerImportResponse> {
+    const latest = await this.prisma.flyerSession.findFirst({
+      where: { userId },
+      orderBy: { createdAt: 'desc' },
+      include: { items: { orderBy: { id: 'asc' } } },
+    });
+
+    if (!latest) {
+      return {
+        sessionId: null,
+        retailer: 'willys',
+        parserVersion: 'v1',
+        items: [],
+        warnings: [],
+      };
+    }
+
+    return this.toFlyerImportResponseFromSession(latest);
+  }
 
   private async persistSessionWithItems(
     userId: number,
@@ -377,7 +411,7 @@ export class FlyerImportService {
     return allowed.has(cleaned) ? cleaned : cleaned;
   }
 
-  private async parseViaInternal(file: Express.Multer.File): Promise<FlyerParseResponse> {
+  private async parseViaInternal(file: Express.Multer.File): Promise<FlyerParseResponse> {
     try {
       this.logger.debug(`Parsing flyer file: ${file.originalname}`);
 
@@ -431,5 +465,92 @@ export class FlyerImportService {
         `Fel vid tolkning av flyer: ${err instanceof Error ? err.message : String(err)}`,
       );
     }
-  }
-}
+  }
+
+  private toFlyerImportItem(item: {
+    id: number;
+    rawName: string;
+    normalizedName: string;
+    categoryHint: string | null;
+    price: Prisma.Decimal | null;
+    priceUnit: string | null;
+    comparisonPrice: Prisma.Decimal | null;
+    comparisonUnit: string | null;
+    offerText: string | null;
+    parseConfidence: number;
+    parseReasons: Prisma.JsonValue | null;
+    matchedProductId: number | null;
+    matchedProductName: string | null;
+    matchedVia: string | null;
+    matchConfidence: number | null;
+    matchReasons: Prisma.JsonValue | null;
+  }): FlyerImportItem {
+    const toStringArray = (value: Prisma.JsonValue | null): string[] => {
+      if (!Array.isArray(value)) return [];
+      return value.map((entry) => String(entry));
+    };
+
+    const normalizedMatchVia =
+      item.matchedVia === 'alias' || item.matchedVia === 'exact' || item.matchedVia === 'token'
+        ? item.matchedVia
+        : 'none';
+
+    const offerLimitText = this.extractOfferLimitText(item.offerText);
+    const offerSignals = this.extractOfferSignals(item.offerText);
+
+    return {
+      flyerItemId: item.id,
+      rawName: item.rawName,
+      normalizedName: item.normalizedName,
+      category: item.categoryHint,
+      price: item.price != null ? item.price.toNumber() : offerSignals.price,
+      priceUnit: this.normalizeUnit(item.priceUnit) ?? offerSignals.priceUnit,
+      comparisonPrice: item.comparisonPrice != null ? item.comparisonPrice.toNumber() : offerSignals.comparisonPrice,
+      comparisonUnit: this.normalizeUnit(item.comparisonUnit) ?? offerSignals.comparisonUnit,
+      offerText: item.offerText,
+      isOffer:
+        item.price != null
+        || item.comparisonPrice != null
+        || !!item.offerText?.trim()
+        || offerSignals.hasCampaignPattern,
+      offerLimitText,
+      parseConfidence: item.parseConfidence,
+      parseReasons: toStringArray(item.parseReasons),
+      matchedProductId: item.matchedProductId,
+      matchedProductName: item.matchedProductName,
+      matchedVia: normalizedMatchVia,
+      matchConfidence: item.matchConfidence ?? 0,
+      matchReasons: toStringArray(item.matchReasons),
+    };
+  }
+
+  private toFlyerImportResponseFromSession(session: {
+    id: number;
+    items: Array<{
+      id: number;
+      rawName: string;
+      normalizedName: string;
+      categoryHint: string | null;
+      price: Prisma.Decimal | null;
+      priceUnit: string | null;
+      comparisonPrice: Prisma.Decimal | null;
+      comparisonUnit: string | null;
+      offerText: string | null;
+      parseConfidence: number;
+      parseReasons: Prisma.JsonValue | null;
+      matchedProductId: number | null;
+      matchedProductName: string | null;
+      matchedVia: string | null;
+      matchConfidence: number | null;
+      matchReasons: Prisma.JsonValue | null;
+    }>;
+  }): FlyerImportResponse {
+    return {
+      sessionId: session.id,
+      retailer: 'willys',
+      parserVersion: 'v1',
+      items: session.items.map((item) => this.toFlyerImportItem(item)),
+      warnings: [],
+    };
+  }
+}