Generic Req-based transport helper for the Polymarket SDK.

This module is the shared HTTP layer used by Polymarket.Gamma, Polymarket.Data, and any future read-mostly Polymarket public-API surface in this package. User code should prefer the higher-level modules; this is documented mainly so it is testable in isolation and so the response contract is recorded once instead of repeated in each consumer.

This module deliberately does not depend on polymarket_clob's HTTP layer. The two have different host defaults and different error semantics: polymarket_clob's HTTP.normalize/2 returns %PolymarketClob.Error{} structs, while this SDK's wrappers return flat tuples. Keeping the layers separate avoids leaking the lower package's namespace into this package's user-facing types.

Response contract

Every call returns one of:

• {:ok, body} — 2xx, body is the JSON-decoded response (Req's built-in :decode_body step handles JSON automatically when the response carries content-type: application/json).
• {:error, {:http_error, status, body}} — non-2xx HTTP response. status is the integer status code; body is the upstream payload (typically a JSON map, sometimes a raw string).
• {:error, {:transport_error, reason}} — Req-level transport failure (DNS, TCP, TLS, connection timeout, HTTP-2 protocol error). reason is the underlying exception or atom.

Options

• :params — keyword list serialized into the query string (default []).
• :plug — Req.Test plug, for tests.
• :timeout — receive_timeout in milliseconds (default 15_000).
• :retry — Req retry policy. Defaults to :transient for GETs and false for everything else, mirroring polymarket_clob's posture.
• :max_retries — Req max retries (default 2).
• :headers — extra request headers (default []).