DpExchange (DpExchangeCore v0.1.1)

The DpExchange family: one identical facade over every trading venue.

⚠️ EXPERIMENTAL

No package in this family has run in production. While they are 0.x the API may change without a major version — pin all three segments (~> 0.1.0). Coverage is uneven by design: in-process fakes and live public endpoints are well covered, order placement and authenticated flows are not.

Do not treat this banner as your check. Maturity is declared per endpoint through each venue's capabilities/0, which reports :proven, :experimental or :unsupported for individual calls. A package can be broadly usable while the one endpoint you depend on is unproven, and the reverse.

What this package is

dp_exchange_core is the contract, not a client. It talks to no exchange. It defines what a venue package is — the facade every one exposes, the value types they return, the canonical-pair normaliser, and the conformance suite that proves an implementation conforms.

Each venue lives in its own repository and its own Hex package, depends on this one, and shares this namespace.

What the facade guarantees

Every venue package exposes the same functions, and a consumer drives any venue through them without knowing which venue it is:

Declaration — provider_name/0, runtime_id/0, asset_classes/0, capabilities/0. Static, credential-free, safe to call at boot.
Market data — prices, historical candles, symbols, order books, instruments.
Account and trading — balances, accounts, fees, transfers, orders, fills. Credentials are passed in as arguments; a package never reads them from a vault.
Streaming — subscribe/2, unsubscribe/2, update_symbols/2, coverage/1. Subscriptions are addressed by the thing itself — the pair, or the symbol on an equity venue — never by a handle a caller would have to hold.

A new venue can be added by implementing that facade, with zero edits to this package, to any other venue package, or to the application consuming them.

What the facade deliberately does not do

It never tells you how the data arrived. Transport, rate limiting, credential and session handling, sharding and supervision are internal to a venue package. Whether subscribe/2 opened one WebSocket, twelve, an MQTT session or a polling loop is not observable through the facade, and that is the load-bearing decision of the whole family — not an omission.

What you can ask is what a venue can do and how fresh it is, through capabilities/0 and coverage/1. coverage/1 reports what is observed arriving, never what was subscribed: a venue that cannot observe delivery says so rather than claiming success.

It does not start anything. Venue packages expose child_spec/1 and are supervised by you. This package ships no aggregate supervisor and no start-everything entry point — it would have to know which venues exist, and it would take a decision that is the consuming application's: which venues run, in what restart strategy, under what names. A consumer who has not asked for a venue never finds a socket open.

The family

Package	Venue
`dp_exchange_core`	— this package, the contract
`dp_exchange_coinbase`	Coinbase
`dp_exchange_gemini`	Gemini
`dp_exchange_webull`	Webull
`dp_exchange_robinhood`	Robinhood
`dp_exchange_schwab`	Charles Schwab

dp_exchange_binance and dp_exchange_kraken are reserved names with no implementation. Neither venue can be verified past public market data from the maintainer's jurisdiction, so neither could ever leave EXPERIMENTAL, and shipping a package that can never be proven is worse than not shipping one.

The namespace is the registry

"coinbase" resolves to DpExchange.Coinbase by convention, so venue/1 needs no registry to maintain, no boot-time registration and no scan of loaded applications. See venue/1.

Summary

Functions

venue(name)

Resolves a venue name to its facade module.

Functions

venue(name)

@spec venue(String.t() | atom()) :: {:ok, module()} | {:error, :unknown_venue}

Resolves a venue name to its facade module.

"coinbase", :coinbase and "Coinbase" all resolve to DpExchange.Coinbase, if that package is a dependency of the calling application.

Fails closed

Returns {:error, :unknown_venue} — never a guess, never a nearby substitute — when the name does not correspond to a loaded venue module. Three distinct ways to be unknown, all one answer:

the atom does not exist, because no such module was ever compiled. Module.safe_concat/2 raises rather than minting an atom from caller input, so a hostile or mistyped name cannot grow the atom table;
the module exists but is not loaded, meaning that venue package is not a dependency;
the module is loaded but is not a venue — DpExchange.Core is a real module under this namespace and must not resolve as a venue.

Enumeration is not offered, deliberately

There is no list_venues/0. A consumer that wants to know which venues it has already has the list, in its own mix.exs. This package resolves; it does not enumerate.

Examples

iex> DpExchange.venue("no_such_venue")
{:error, :unknown_venue}

iex> DpExchange.venue(DpExchange.Core)
{:error, :unknown_venue}