# Txpost
Send and receive Bitcoin transactions from your Phoenix or Plug-based Elixir application.
Txpost implements a standard for encoding and decoding Bitcoin transactions and other data in a concise binary format using [CBOR](https://cbor.io). A number of modules following the Plug specification can easily be slotted in your Phoenix or Plug-based application's pipeline. An optional Router module is available, allowing you to implement routing logic for different types of transactions from a single endpoint.
* Receive Bitcoin transactions in a concise and efficient binary serialisation format
* Simple and flexible schema for sending Bitcoin data with other data parameters
* Send multiple transactions in a single request, or build streaming applications
* Sign and verify data payloads with ECDSA signatures
### BRFC specifications
Txpost is an implementation of the following BRFC specifications. They describe a standard for serialising Bitcoin transactions and associated parameters, along with arbitrary meta data, in a concise binary format using CBOR:
* BRFC `c9a2975b3d19` - [CBOR Tx Payload specification](https://github.com/libitx/txpost/blob/master/brfc-specs/cbor-tx-payload.md)
* BRFC `5b82a2ed7b16` - [CBOR Tx Envelope specification](https://github.com/libitx/txpost/blob/master/brfc-specs/cbor-tx-envelope.md)
## Installation
The package can be installed by adding `txpost` to your list of dependencies in `mix.exs`.
```elixir
def deps do
[
{:txpost, "~> 0.1"}
]
end
```
Add `Txpost.Parsers.CBOR` to your endpoint's list of parsers.
```elixir
plug Plug.Parsers,
parsers: [
:json,
Txpost.Parsers.CBOR
]
```
Finally create any routes needed to handle transaction requests and add `Txpost.Plug` to the plug pipeline. For example, adding a route to a Phoenix router:
```elixir
defmodule MyAppWeb.Router do
use MyAppWeb, :router
pipeline :tx_api do
plug :accepts, ["cbor"]
plug Txpost.Plug
end
scope "/tx" do
pipe_through :tx_api
post "/create", MyAppWeb.TxController, :create
end
end
```
For detailed examples, refer to the [full documentation](https://hexdocs.pm/txpost).
## Transaction routing
The example above creates a single route passing all transactions to the same controller. You could create many routes for different transactions but in some applications it may be desirable to advertise a single endpoint to receive different types of transactions, each handled by different controllers. In this case `Txpost.Router` can be used to route transactions to different controllers, using any logic you need.
A tx router is a module that implements the `Txpost.Router.handle_tx/2` callback.
```elixir
defmodule MyApp.TxRouter do
use Txpost.Router
def handle_tx(conn, _params) do
case get_req_meta(conn) do
%{"type" => "article"} -> ArticleController.call(conn, :create)
%{"type" => "image"} -> ImageController.call(conn, :create)
end
end
end
```
For more details, refer to the [full documentation](https://hexdocs.pm/txpost).
## License
Txpost is open source and released under the [Apache-2 License](https://github.com/libitx/txpost/blob/master/LICENSE).
© Copyright 2021 Chronos Labs Ltd.
