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",
    };
  }
}