Search documentation of polar_express

# Getting Started

Copy Markdown View Source

## 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 API key config to `config/dev.exs`
- Add runtime env var config to `config/runtime.exs`
- Add `PolarExpress.WebhookPlug` to your endpoint (before `Plug.Parsers`)
- Scaffold a `PolarWebhookController` with event handler stubs
- Add the webhook route to your router

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

Add your PolarExpress credentials to your application config. The recommended pattern is to use `config/dev.exs` for sandbox keys and `config/runtime.exs` for production:

    # config/dev.exs
    import Config

    config :polar_express,
      api_key: "pk_test_...",
      webhook_secret: "whsec_test_..."

    # config/runtime.exs
    import Config

    if config_env() == :prod do
      config :polar_express,
        api_key: System.fetch_env!("POLAR_ACCESS_TOKEN"),
        webhook_secret: System.fetch_env!("POLAR_WEBHOOK_SECRET")
    end

### All Config Options

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

    config :polar_express,
      # Required
      api_key: "pk_test_...",

      # Webhooks (required if using WebhookPlug)
      webhook_secret: "whsec_...",

      # Optional — all have defaults if omitted
      server: :sandbox,                  # :sandbox or :production (default: :production)
      max_retries: 3,                    # default: 2
      timeout_ms: 60_000,               # request timeout in ms (default: 30,000)
      finch: MyApp.Finch                 # custom Finch pool (default: PolarExpress.Finch)

Key | Used By | Default | Description
--- | --- | --- | ---
`:api_key` | `PolarExpress.client/0,1,2` | required | Polar API key
`:webhook_secret` | `PolarExpress.WebhookPlug` | — | Webhook signing secret
`:server` | `PolarExpress.client/0,1,2` | `:production` | API environment (`:sandbox` or `:production`)
`:max_retries` | `PolarExpress.client/0,1,2` | `2` | Max retry attempts
`:timeout_ms` | `PolarExpress.client/0,1,2` | `30_000` | Request timeout in ms
`:finch` | `PolarExpress.client/0,1,2` | `PolarExpress.Finch` | Custom Finch pool name

## Creating a Client

Once configured, create a client with no arguments — it reads from your config automatically:

    client = PolarExpress.client()

### Overriding Config

Pass options to override any config value for a specific client:

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

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

### Explicit API Key

Pass a string to use a different API key (config defaults still apply for other options):

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

### Config Precedence

Options are resolved in this order (highest wins):

1. Explicit arguments to `client/1` or `client/2`
2. Application config (`config :polar_express, ...`)
3. Struct defaults (e.g. `max_retries: 2`)

Clients are plain structs with no global state — 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.

    # Via config
    config :polar_express, max_retries: 5

    # Or per-client
    client = PolarExpress.client(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

← Previous Page Changelog
Next Page → Igniter Installer