Smite API v2.0

package me.rabrg.smite;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

import me.rabrg.smite.response.LeagueLeaderboardResponse;
import me.rabrg.smite.response.SessionResponse;

import com.google.gson.Gson;

/**
 * The core class of the Smite API.
 * @author Ryan Greene
 *
 */
public final class SmiteApi {

    /**
     * An instance of the UTF-8 charset.
     */
    private static final Charset UTF_8_CHARSET = Charset.forName("UTF-8");

    /**
     * The date format used by Smite's API.
     */
    private static final DateFormat DATE_FORMAT = new SimpleDateFormat("yyyyMMddHHmmss");

    /**
     * The developer's identification number.
     */
    private final int devId;

    /**
     * The developer's authentication key.
     */
    private final String authKey;

    /**
     * The MessageDigest instance used to create signatures.
     */
    private final MessageDigest messageDigest;

    /**
     * The Gson instance for deserializing responses.
     */
    private final Gson gson;

    /**
     * The current session id.
     */
    private String sessionId;

    /**
     * Sets the DateFormat instanc's timezone to Smite API's.
     */
    static {
        DATE_FORMAT.setTimeZone(TimeZone.getTimeZone("UTC"));
    }

    /**
     * Constructs a new SmiteAPI instance with the specified developer credentials.
     * @param devId The developer's identification number.
     * @param authKey The developer's authentication key.
     */
    public SmiteApi(final int devId, final String authKey) {
        this.devId = devId;
        this.authKey = authKey;
        try {
            messageDigest = MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException("The provider for the MD5 algorithm does not exist");
        }
        gson = new Gson();
        createNewSession();
    }

    /**
     * Creates a new session, setting the session id for future requests.
     */
    public void createNewSession() {
        sessionId = getSessionResponse().getSessionId();
    }

    public SessionResponse getSessionResponse() {
        return gson.fromJson(getTextResponse("createsession"), SessionResponse.class);
    }

    public LeagueLeaderboardResponse[] getLeagueLeaderboardResponse(final int queue, final int tier, final int season) {
        return gson.fromJson(getTextResponse("getleagueleaderboard", "" + queue, "" + tier, "" + season), LeagueLeaderboardResponse[].class);
    }

    private String getTextResponse(final String method, final String... arguments) {
        final StringBuffer urlStringBuffer = new StringBuffer("http://api.smitegame.com/smiteapi.svc/").append(method).append("json");
        final String date = getDate();
        if (!method.equals("ping")) {
            urlStringBuffer.append('/').append(devId).append('/').append(createSignature(method, date));
            if (!method.equals("createsession")) {
                urlStringBuffer.append('/').append(sessionId);
            }
            urlStringBuffer.append('/').append(date);
            for (final String argument : arguments) {
                urlStringBuffer.append("/" + argument);
            }
        }
        System.out.println(urlStringBuffer);
        try {
            final BufferedReader reader = new BufferedReader(new InputStreamReader(new URL(urlStringBuffer.toString()).openStream()));
            final StringBuffer response = new StringBuffer();
            String line;
            while((line = reader.readLine()) != null) {
                response.append(line);
            }
            return response.toString();
        } catch (IOException e) {
            throw new IllegalStateException("Could not get response for method " + method + " and arguments " + arguments);
        }
    }

    /**
     * Creates a signature for the specified method name and with specified date.
     * @param methodName The name of the method the signature is created for.
     * @param date The date the signature is created at.
     * @return The created signature.
     */
    private String createSignature(final String methodName, final String date) {
        final StringBuilder signature = new StringBuilder();
        for (final byte b : messageDigest.digest(new StringBuffer().append(devId).append(methodName).append(authKey).append(date).toString().getBytes(UTF_8_CHARSET))) {
            signature.append(String.format("%02x", b).replaceAll("\\s", ""));
        }
        return signature.toString();
    }

    /**
     * Gets the developer's identification number.
     * @return The developer's identification number.
     */
    public int getDevId() {
        return devId;
    }

    /**
     * Gets the developer's authentication key.
     * @return The developer's authentication key.
     */
    public String getAuthKey() {
        return authKey;
    }

    /**
     * Gets the current formated date.
     * @return The current formated date.
     */
    public String getDate() {
        return DATE_FORMAT.format(new Date());
    }

}