Getting Started

Installation

With Igniter (recommended for Phoenix)

Beta: The Igniter installer is new and under active testing. Report issues here.

If your project uses Igniter, one command adds the dependency and configures everything:

mix igniter.install polar_express

This will:

• Add PolarExpress.WebhookPlug to your endpoint (before Plug.Parsers)
• Scaffold a PolarWebhookController with event handler stubs
• Add the webhook route to your router
• Show where to start the Finch pool and pass credentials explicitly

Igniter shows a diff of all changes for your approval before writing anything. See the Igniter Installer guide for a detailed walkthrough, or the Webhooks guide for customizing the controller.

Manual

Add polar_express to your dependencies in mix.exs:

def deps do
  [
    {:polar_express, "~> 0.1.0"}
  ]
end

Requires Elixir 1.19+ and OTP 27+.

Configuration

PolarExpress does not read config :polar_express. Read credentials from your own application boundary, then pass them to PolarExpress.client/1 or PolarExpress.client/2.

Start the default Finch pool in your application supervision tree:

# lib/my_app/application.ex
children = [
  PolarExpress
]

If you already run your own Finch pool, pass its name when creating the client:

children = [
  {Finch, name: MyApp.Finch}
]

client = PolarExpress.client("pk_test_...", finch: MyApp.Finch)

Client Options

The only required key is :api_key. Everything else has sensible defaults:

PolarExpress.client(
  api_key: "pk_test_...",
  server: :sandbox,
  max_retries: 3,
  timeout_ms: 60_000,
  finch: MyApp.Finch
)

Creating a Client

Create a client with an explicit API key:

client = PolarExpress.client(System.fetch_env!("POLAR_ACCESS_TOKEN"))

Per-Client Options

Pass options for a specific client:

# Override the server environment
client = PolarExpress.client("pk_test_...", server: :production)

# Override retries and timeout
client = PolarExpress.client("pk_test_...", max_retries: 5, timeout_ms: 60_000)

Keyword API Key

You can also pass the key in keyword options:

client = PolarExpress.client(api_key: "pk_test_...", server: :sandbox)

Clients are plain structs with no global app config — safe for concurrent use with multiple API keys.

Making API Calls

Service modules map 1:1 to Polar's API resources. Each method takes the client as the first argument:

# Create a customer
{:ok, customer} = PolarExpress.Services.CustomersService.create_customer(client, %{
  email: "jane@example.com"
})

# Get a product
{:ok, product} = PolarExpress.Services.ProductsService.get_product(client, "prod_123")

# List orders
{:ok, orders} = PolarExpress.Services.OrdersService.list_orders(client, %{})

Typed Responses

API responses are automatically deserialized into typed Elixir structs:

customer.id        #=> "cus_abc123"
customer.email     #=> "jane@example.com"
customer.__struct__ #=> PolarExpress.Resources.Customer

Every resource struct has @type t definitions, so Dialyzer catches field access errors at compile time.

Error Handling

All API errors return {:error, %PolarExpress.Error{}}:

case PolarExpress.Services.CheckoutsService.create_checkout_session(client, params) do
  {:ok, checkout} ->
    checkout

  {:error, %PolarExpress.Error{type: :validation_error} = err} ->
    Logger.warning("Validation failed: #{err.message}")

  {:error, %PolarExpress.Error{type: :rate_limit_error}} ->
    Process.sleep(1_000)
    retry()

  {:error, err} ->
    Logger.error("Polar API error: #{err.message}")
end

Per-Request Overrides

Options can be overridden per-request for multi-environment scenarios:

PolarExpress.Services.OrdersService.list_orders(client, %{},
  server: :production
)

Pagination

List endpoints return paginated results with lazy auto-paging support:

{:ok, page} = PolarExpress.Services.CustomersService.list_customers(client, %{})

page
|> PolarExpress.ListObject.auto_paging_stream(client, "/v1/customers/")
|> Stream.filter(& &1.email)
|> Enum.to_list()

Retries

Failed requests (network errors, 408, 409, 429, 500, 502, 503, 504) are automatically retried with exponential backoff and jitter.

client = PolarExpress.client("pk_test_...", max_retries: 5)

Idempotency keys can be passed for idempotent operations:

PolarExpress.Services.CheckoutsService.create_checkout_session(client, params,
  idempotency_key: "checkout_123"
)

Next Steps

• Webhooks — receive and verify Polar events
• Testing — stub HTTP requests in your test suite
• Telemetry — observability and metrics
• Igniter Installer — automated Phoenix setup