finance-app/src/lib/rules.ts

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

export interface SplitEntry {
  participant_id: number;
  share_percent: number;
}

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

export interface TxFields {
  effective_category: string;
  effective_merchant: string;
  description: string;
  bank_name: string;
  amount: number;
  transaction_type: string;
  tags: { id: number }[];
}

export 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;
    }
  }

  if (cond.field === "tag") {
    const tagId = Number(cond.value);
    const hasTag = tx.tags.some((t) => t.id === tagId);
    return cond.operator === "not_equals" ? !hasTag : hasTag;
  }

  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;
    case "transaction_type":    fieldVal = tx.transaction_type || ""; 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;
  }
}