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blockfrost-client

Haskell SDK for Blockfrost.io API.

Development shell

nix-shell # from repository root, optional
cabal repl blockfrost-client

Usage

Blockfrost.io API token is required to use this SDK.

Obtaining token

Create a project at blockfrost.io and save the generated token to a file.

For authentication, client uses a Project type which carries an environment and a token itself, for example Project Testnet "someToken".

Project from file

Instead of constructing this type manually, you can load the Project from file using projectFromFile "/secrets/blockfrost-testnet-token".

In this case, token needs to be prefixed with the enviromnent to which it belongs to. The format expected is <env><token> (similar to human readable identifiers used for Cardano keys and addresses), examples:

  • testnet123notArealToken
  • mainnet456notRealEither
  • ipfs789mightBeARealOne

Using environment variables

In similar manner to loading project from file, you can use projectFromEnv function to load the Project from file pointed to by BLOCKFROST_TOKEN_PATH environment variable.

For custom variable name, a principled version projectFromEnv' "CUSTOM_ENV_VAR" can be used instead.

Exploring the API

You can now perform queries from cabal repl blockfrost-client, an example session follows:

λ: testnet <- projectFromFile "/secrets/blockfrost.testnet.token"
λ: testnet
Project {projectEnv = Testnet, projectId = "censored"}
λ: runBlockfrost testnet $ getLatestBlock
Right (Block {_blockTime = 1629716610s, ... })
λ: runBlockfrost testnet $ listPools
Right [PoolId "pool1adur9jcn0dkjpm3v8ayf94yn3fe5xfk2rqfz7rfpuh6cw6evd7w", ... ]

Pagination and sorting

Some API functions have a variant with trailing '. These accept Paged and SortOrder arguments for querying multiple pages and setting a custom sort order.

For example to query the second page of pool list, we can use listPools'

λ: runBlockfrost testnet $ listPools' (page 2) desc

To use default ordering (which is asc or Ascending), you can just use re-exported def from Data.Default.

λ: runBlockfrost testnet $ listPools' (page 2) def

Similar, to just change an ordering but use default page size and a first page:

λ: runBlockfrost testnet $ listPools' def desc

Catching errors

We can use tryError inside BlockfrostClient monad to try a call, when we it may fail (dealing with external inputs, enumerating addresses).

Complete program example with error handling:

{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Main
  where

import Blockfrost.Client

main = do
  -- reads token from BLOCKFROST_TOKEN_PATH
  -- environment variable. It expects token
  -- prefixed with Blockfrost environment name
  -- e.g.: testnet-someTokenHash
  prj <- projectFromEnv
  res <- runBlockfrost prj $ do
    latestBlocks <- getLatestBlock
    (ers :: Either BlockfrostError [AccountReward]) <-
        tryError $ getAccountRewards "gonnaFail"
    pure (latestBlocks, ers)

  print res