liblastfm

Complete API interface to last.fm service. Documentation is available in two flavours:

• original API reference

• liblastfm haddocks

Introduction

liblastfm provides Applicative interface for constructing requests. Also, it handles all machinery needed to prepare request for sending:

• signing

• url-encoding

• miscellaneous stuff like choosing correct HTTP method, etc

Once request is ready, liblastfm can send it and get you back a response. Response format might be:

• aeson Value for json queries

• xml-conduit Document for xml queries

Installation

To install either use hackage:

% cabal install liblastfm

Or git:

% git clone git@github.com:supki/liblastfm
% cd liblastfm
% cabal install

Usage

Suppose, you need to use tag.search API method. First find it in liblastfm: Tag would be the name of the module and search would be the name of function. Here it is. So import a couple of modules:

>>> import           Lastfm            -- a bunch of useful utilities
>>> import qualified Lastfm.Tag as Tag -- for Tag.search

Now you may use applicative <*> for required and <* or *> for optional parameters to construct desired request:

Tag.search <*> tag "russian-folk" <* limit 3 <*> apiKey "29effec263316a1f8a97f753caaa83e0" <* json

To send constructed request use lastfm:

>>> con <- newConnection
>>> lastfm con $ Tag.search <*> tag "russian-folk" <* limit 10 <*> apiKey "29effec263316a1f8a97f753caaa83e0" <* json
Right (Object (fromList [("results",Object (fromList [("tagmatches", ...

Wiki describes how to parse responses.

FAQ

Q: I'm getting the following error. How do I fix it?

>>> Artist.getInfo <*> artist "Pink Floyd" <*> apiKey "29effec263316a1f8a97f753caaa83e0"
<interactive>:8:27:
    Couldn't match expected type `Data.Text.Lazy.Internal.Text'
                with actual type `[Char]

A: This means you haven't OverloadedStrings extension enabled. To enable it (either one works):

• type in :set -XOverloadedStrings while in ghci session.

• add {-# LANGUAGE OverloadedStrings #-} to the top of the file

• compile with -XOverloadedStrings switch

Q: I'm getting the following error. How do I fix it?

>>> lastfm (Artist.getInfo <*> artist "Pink Floyd" <*> apiKey "29effec263316a1f8a97f753caaa83e0")
<interactive>:13:1:
    No instance for (Show (IO (Either LastfmError r0)))
      arising from a use of `print'
    Possible fix:
      add an instance declaration for (Show (IO (Either LastfmError r0)))
    In the first argument of `print', namely `it'
    In a stmt of an interactive GHCi command: print it

A: This error message indicates that GHC cannot infer response format for the Request. To fix it, add use json or xml helpers, depending on your needs

A note on testing

To test Lastfm API compatibility (api test suite)—specifically, authentication requiring examples—you will need to set HASKELL_LIBLASTFM_APIKEY, HASKELL_LIBLASTFM_SESSIONKEY, and HASKELL_LIBLASTFM_SECRET environment variables to your api key, session key, and secret respectively; for example (bash):

export HASKELL_LIBLASTFM_APIKEY="__API_KEY__"
export HASKELL_LIBLASTFM_SESSIONKEY="__SESSION_KEY__"
export HASKELL_LIBLASTFM_SECRET="__SECRET__"

Please, consult Lastfm API documentation and example/*-authentication.hs examples if you don't know where to get your credentials.