feat(import): add Splitwise API import for full expense history

public/locales/en/common.json

@@ -31,6 +31,7 @@
     },
     "follow_on_x": "Follow us on X",
     "import_from_splitwise": "Import from Splitwise",
+    "import_from_splitwise_api": "Import from Splitwise (API)",
     "import_from_splitwise_details": {
       "choose_file": "Choose file",
       "export_splitwise_data_button": "Export splitwise data",

src/lib/splitwise-api.ts

@@ -0,0 +1,304 @@
+/**
+ * Splitwise API Service
+ *
+ * Provides methods to fetch data from Splitwise API for importing
+ * expenses into SplitPro with complete accuracy.
+ */
+
+const API_BASE = 'https://secure.splitwise.com/api/v3.0';
+
+// ============= TYPES =============
+
+export interface SplitwiseUserShare {
+  user_id: number;
+  user: {
+    id: number;
+    first_name: string;
+    last_name: string | null;
+    email: string;
+    picture?: {
+      medium?: string;
+    };
+  };
+  paid_share: string;
+  owed_share: string;
+  net_balance: string;
+}
+
+export interface SplitwiseExpense {
+  id: number;
+  cost: string;
+  description: string;
+  details: string | null;
+  date: string;
+  currency_code: string;
+  category: {
+    id: number;
+    name: string;
+  };
+  group_id: number | null;
+  friendship_id: number | null;
+  expense_bundle_id: number | null;
+  repeats: boolean;
+  repeat_interval: string | null;
+  email_reminder: boolean;
+  email_reminder_in_advance: number | null;
+  next_repeat: string | null;
+  comments_count: number;
+  payment: boolean;
+  transaction_confirmed: boolean;
+  created_at: string;
+  created_by: {
+    id: number;
+    first_name: string;
+    last_name: string | null;
+  };
+  updated_at: string;
+  updated_by: {
+    id: number;
+    first_name: string;
+    last_name: string | null;
+  } | null;
+  deleted_at: string | null;
+  deleted_by: {
+    id: number;
+    first_name: string;
+    last_name: string | null;
+  } | null;
+  users: SplitwiseUserShare[];
+  repayments: {
+    from: number;
+    to: number;
+    amount: string;
+  }[];
+}
+
+export interface SplitwiseGroupMember {
+  id: number;
+  first_name: string;
+  last_name: string | null;
+  email: string;
+  registration_status: string;
+  picture?: {
+    medium?: string;
+  };
+  balance: {
+    currency_code: string;
+    amount: string;
+  }[];
+}
+
+export interface SplitwiseGroup {
+  id: number;
+  name: string;
+  group_type: string;
+  updated_at: string;
+  created_at: string;
+  simplify_by_default: boolean;
+  members: SplitwiseGroupMember[];
+  original_debts: {
+    from: number;
+    to: number;
+    amount: string;
+    currency_code: string;
+  }[];
+  simplified_debts: {
+    from: number;
+    to: number;
+    amount: string;
+    currency_code: string;
+  }[];
+}
+
+export interface SplitwiseFriend {
+  id: number;
+  first_name: string;
+  last_name: string | null;
+  email: string;
+  registration_status: string;
+  picture?: {
+    medium?: string;
+  };
+  balance: {
+    currency_code: string;
+    amount: string;
+  }[];
+  groups: {
+    group_id: number;
+    balance: Array<{
+      currency_code: string;
+      amount: string;
+    }>;
+  }[];
+}
+
+export interface SplitwiseCurrentUser {
+  id: number;
+  first_name: string;
+  last_name: string | null;
+  email: string;
+  picture?: {
+    medium?: string;
+  };
+  default_currency: string;
+}
+
+// ============= API CLIENT =============
+
+export class SplitwiseApiError extends Error {
+  constructor(
+    message: string,
+    public status: number,
+    public statusText: string,
+  ) {
+    super(message);
+    this.name = 'SplitwiseApiError';
+  }
+}
+
+async function fetchFromSplitwise<T>(
+  endpoint: string,
+  apiKey: string,
+  params?: Record<string, string | number>,
+): Promise<T> {
+  const url = new URL(`${API_BASE}${endpoint}`);
+
+  if (params) {
+    Object.entries(params).forEach(([key, value]) => {
+      url.searchParams.append(key, String(value));
+    });
+  }
+
+  const response = await fetch(url.toString(), {
+    headers: {
+      Authorization: `Bearer ${apiKey}`,
+      'Content-Type': 'application/json',
+    },
+  });
+
+  if (!response.ok) {
+    throw new SplitwiseApiError(
+      `Splitwise API request failed: ${response.status} ${response.statusText}`,
+      response.status,
+      response.statusText,
+    );
+  }
+
+  return response.json() as Promise<T>;
+}
+
+// ============= API METHODS =============
+
+/**
+ * Get current user info to validate API key
+ */
+export async function getCurrentUser(apiKey: string): Promise<SplitwiseCurrentUser> {
+  const response = await fetchFromSplitwise<{
+    user: SplitwiseCurrentUser;
+  }>('/get_current_user', apiKey);
+  return response.user;
+}
+
+/**
+ * Get all groups for the current user
+ */
+export async function getGroups(apiKey: string): Promise<SplitwiseGroup[]> {
+  const response = await fetchFromSplitwise<{ groups: SplitwiseGroup[] }>('/get_groups', apiKey);
+  // Filter out the "Non-group expenses" (id: 0)
+  return response.groups.filter((g) => g.id !== 0);
+}
+
+/**
+ * Get all friends for the current user
+ */
+export async function getFriends(apiKey: string): Promise<SplitwiseFriend[]> {
+  const response = await fetchFromSplitwise<{ friends: SplitwiseFriend[] }>('/get_friends', apiKey);
+  return response.friends;
+}
+
+/**
+ * Get expenses for a specific group with pagination
+ */
+export async function getGroupExpenses(
+  apiKey: string,
+  groupId: number,
+  options: {
+    limit?: number;
+    offset?: number;
+    datedAfter?: string;
+    datedBefore?: string;
+  } = {},
+): Promise<SplitwiseExpense[]> {
+  const params: Record<string, string | number> = {
+    group_id: groupId,
+    limit: options.limit ?? 100,
+    offset: options.offset ?? 0,
+  };
+
+  if (options.datedAfter) {
+    params.dated_after = options.datedAfter;
+  }
+  if (options.datedBefore) {
+    params.dated_before = options.datedBefore;
+  }
+
+  const response = await fetchFromSplitwise<{ expenses: SplitwiseExpense[] }>(
+    '/get_expenses',
+    apiKey,
+    params,
+  );
+
+  return response.expenses;
+}
+
+/**
+ * Get ALL expenses for a group (handles pagination automatically)
+ */
+export async function getAllGroupExpenses(
+  apiKey: string,
+  groupId: number,
+  onProgress?: (fetched: number, total: number | null) => void,
+): Promise<SplitwiseExpense[]> {
+  const allExpenses: SplitwiseExpense[] = [];
+  const limit = 100;
+  let offset = 0;
+  let hasMore = true;
+
+  while (hasMore) {
+    const expenses = await getGroupExpenses(apiKey, groupId, { limit, offset });
+
+    // Filter out deleted expenses
+    const activeExpenses = expenses.filter((e) => !e.deleted_at);
+    allExpenses.push(...activeExpenses);
+
+    onProgress?.(allExpenses.length, null);
+
+    if (expenses.length < limit) {
+      hasMore = false;
+    } else {
+      offset += limit;
+    }
+  }
+
+  return allExpenses;
+}
+
+/**
+ * Validate API key by trying to fetch current user
+ */
+export async function validateApiKey(
+  apiKey: string,
+): Promise<{ valid: boolean; user?: SplitwiseCurrentUser; error?: string }> {
+  try {
+    const user = await getCurrentUser(apiKey);
+    return { valid: true, user };
+  } catch (error) {
+    if (error instanceof SplitwiseApiError) {
+      if (error.status === 401) {
+        return { valid: false, error: 'Invalid API key' };
+      }
+      return { valid: false, error: error.message };
+    }
+    return { valid: false, error: 'Failed to validate API key' };
+  }
+}