Add offline merchant category suggestions

src/lib/category-suggestion.ts

@@ -0,0 +1,119 @@
+import { CATEGORY_VALUES, type CategoryValue } from "@/lib/categories";
+
+type SuggestionSource = "rule" | "model" | "unavailable";
+
+export type CategorySuggestion = {
+  category: CategoryValue | null;
+  message: string;
+  merchantName: string;
+  requiresConfirmation: boolean;
+  source: SuggestionSource;
+};
+
+type MerchantRule = {
+  category: CategoryValue;
+  patterns: RegExp[];
+};
+
+const MERCHANT_RULES: MerchantRule[] = [
+  { category: "SHOPPING", patterns: [/amazon/i, /flipkart/i, /myntra/i] },
+  { category: "FOOD", patterns: [/swiggy/i, /zomato/i, /starbucks/i, /instamart/i, /blinkit/i] },
+  { category: "TRANSPORT", patterns: [/uber/i, /ola/i, /rapido/i, /metro/i] },
+  { category: "BILLS", patterns: [/airtel/i, /jio/i, /electricity/i, /water bill/i] },
+  { category: "HEALTH", patterns: [/apollo/i, /pharmacy/i, /clinic/i, /hospital/i] },
+  { category: "ENTERTAINMENT", patterns: [/netflix/i, /spotify/i, /bookmyshow/i] },
+  { category: "RENT", patterns: [/rent/i, /landlord/i, /lease/i] },
+];
+
+export function normalizeMerchantName(value: string) {
+  return value.trim().replace(/\s+/g, " ");
+}
+
+export function getMerchantRuleCategory(merchantName: string): CategoryValue | null {
+  const normalized = normalizeMerchantName(merchantName);
+
+  for (const rule of MERCHANT_RULES) {
+    if (rule.patterns.some((pattern) => pattern.test(normalized))) {
+      return rule.category;
+    }
+  }
+
+  return null;
+}
+
+function parseSuggestedCategory(raw: unknown): CategoryValue | null {
+  if (typeof raw !== "string") {
+    return null;
+  }
+
+  const normalized = raw.trim().toUpperCase();
+  return CATEGORY_VALUES.includes(normalized as CategoryValue) ? (normalized as CategoryValue) : null;
+}
+
+export async function suggestCategoryForMerchant(merchantName: string): Promise<CategorySuggestion> {
+  const normalized = normalizeMerchantName(merchantName);
+
+  if (!normalized) {
+    return {
+      category: null,
+      message: "Enter a merchant name to get a suggestion.",
+      merchantName: normalized,
+      requiresConfirmation: false,
+      source: "unavailable",
+    };
+  }
+
+  const matchedCategory = getMerchantRuleCategory(normalized);
+  if (matchedCategory) {
+    return {
+      category: matchedCategory,
+      message: "Known merchant matched locally. Category auto-filled.",
+      merchantName: normalized,
+      requiresConfirmation: false,
+      source: "rule",
+    };
+  }
+
+  try {
+    const response = await fetch(`${process.env.OLLAMA_URL ?? "http://127.0.0.1:11434"}/api/generate`, {
+      method: "POST",
+      headers: { "Content-Type": "application/json" },
+      body: JSON.stringify({
+        model: process.env.OLLAMA_MODEL ?? "qwen2.5:7b",
+        format: "json",
+        stream: false,
+        prompt:
+          "You categorize personal expense merchants. Return JSON with one key named category. Allowed values only: RENT, FOOD, TRANSPORT, BILLS, SHOPPING, HEALTH, ENTERTAINMENT, MISC. Merchant: " +
+          normalized,
+      }),
+    });
+
+    if (!response.ok) {
+      throw new Error(`Ollama request failed with ${response.status}`);
+    }
+
+    const payload = (await response.json()) as { response?: string };
+    const parsed = payload.response ? JSON.parse(payload.response) : null;
+    const category = parseSuggestedCategory(parsed?.category);
+
+    if (!category) {
+      throw new Error("Model did not return a valid category.");
+    }
+
+    return {
+      category,
+      message: "Local AI suggested a category. Review before saving.",
+      merchantName: normalized,
+      requiresConfirmation: true,
+      source: "model",
+    };
+  } catch {
+    return {
+      category: null,
+      message: "Local AI suggestion is unavailable right now. Choose a category manually.",
+      merchantName: normalized,
+      requiresConfirmation: false,
+      source: "unavailable",
+    };
+  }
+}