finance-app/src/app/api/rules/apply/route.ts

import { NextRequest, NextResponse } from "next/server";
import { getCurrentUser } from "@/lib/auth";
import { queryRaw } from "@/lib/db";
import { getTransactions } from "@/lib/queries";

interface Condition {
  field: "merchant_normalized" | "description" | "category" | "bank_name" | "amount";
  operator: "contains" | "equals" | "starts_with" | "gt" | "lt" | "not_equals";
  value: string;
}

interface Actions {
  set_category?: string;
  add_tag_ids?: number[];
  set_merchant?: string;
}

interface TxFields {
  effective_category: string;
  effective_merchant: string;
  description: string;
  bank_name: string;
  amount: number;
}

function evaluateCondition(cond: Condition, tx: TxFields): boolean {
  if (cond.field === "amount") {
    const numVal = Number(tx.amount);
    const numCond = Number(cond.value);
    switch (cond.operator) {
      case "equals": return numVal === numCond;
      case "not_equals": return numVal !== numCond;
      case "gt": return numVal > numCond;
      case "lt": return numVal < numCond;
      default: return false;
    }
  }

  let fieldVal: string;
  switch (cond.field) {
    case "merchant_normalized": fieldVal = tx.effective_merchant || ""; break;
    case "description": fieldVal = tx.description || ""; break;
    case "category": fieldVal = tx.effective_category || ""; break;
    case "bank_name": fieldVal = tx.bank_name || ""; break;
    default: return false;
  }

  const strVal = fieldVal.toLowerCase();
  const strCond = cond.value.toLowerCase();
  switch (cond.operator) {
    case "contains": return strVal.includes(strCond);
    case "equals": return strVal === strCond;
    case "starts_with": return strVal.startsWith(strCond);
    case "not_equals": return strVal !== strCond;
    default: return false;
  }
}

export async function POST(req: NextRequest) {
  const user = await getCurrentUser(req);
  if (!user) return NextResponse.json({ error: "Unauthorized" }, { status: 403 });

  const rules = await queryRaw<{ id: number; conditions: unknown; actions: unknown }>(
    `SELECT id, conditions, actions FROM rules WHERE owner_id = $1 AND enabled = true ORDER BY priority DESC`,
    [user.id]
  );

  if (!rules.length) return NextResponse.json({ matched: 0, transactions_affected: 0 });

  const { data: transactions } = await getTransactions(user.id, { limit: 100000, offset: 0 });

  let matched = 0;
  const affectedIds = new Set<number>();

  for (const rule of rules) {
    const conditions = (typeof rule.conditions === "string"
      ? JSON.parse(rule.conditions)
      : rule.conditions) as Condition[];
    const actions = (typeof rule.actions === "string"
      ? JSON.parse(rule.actions)
      : rule.actions) as Actions;

    for (const tx of transactions) {
      const allMatch =
        conditions.length === 0 || conditions.every((c) => evaluateCondition(c, tx));
      if (!allMatch) continue;

      matched++;
      affectedIds.add(tx.id);

      if (actions.set_category || actions.set_merchant) {
        await queryRaw(
          `INSERT INTO transaction_overrides (transaction_id, category_override, merchant_normalized)
           VALUES ($1, $2, $3)
           ON CONFLICT (transaction_id) DO UPDATE SET
             category_override = COALESCE($2, transaction_overrides.category_override),
             merchant_normalized = COALESCE($3, transaction_overrides.merchant_normalized),
             updated_at = NOW()`,
          [tx.id, actions.set_category || null, actions.set_merchant || null]
        );
      }

      if (actions.add_tag_ids?.length) {
        for (const tagId of actions.add_tag_ids) {
          await queryRaw(
            `INSERT INTO transaction_tags (transaction_id, tag_id) VALUES ($1, $2) ON CONFLICT DO NOTHING`,
            [tx.id, tagId]
          );
        }
      }
    }
  }

  return NextResponse.json({ matched, transactions_affected: affectedIds.size });
}