package org.kohsuke.github;

import java.io.IOException;
import java.io.InterruptedIOException;
import java.net.HttpURLConnection;

/**
 * Pluggable strategy to determine what to do when the API rate limit is reached.
 *
 * @author Kohsuke Kawaguchi
 * @see GitHubBuilder#withRateLimitHandler(RateLimitHandler) GitHubBuilder#withRateLimitHandler(RateLimitHandler)
 * @see AbuseLimitHandler
 */
public abstract class RateLimitHandler {
    /**
     * Called when the library encounters HTTP error indicating that the API rate limit is reached.
     *
     * <p>
     * Any exception thrown from this method will cause the request to fail, and the caller of github-api will receive
     * an exception. If this method returns normally, another request will be attempted. For that to make sense, the
     * implementation needs to wait for some time.
     *
     * @param e
     *            Exception from Java I/O layer. If you decide to fail the processing, you can throw this exception (or
     *            wrap this exception into another exception and throw it.)
     * @param uc
     *            Connection that resulted in an error. Useful for accessing other response headers.
     * @throws IOException
     *             the io exception
     * @see <a href="https://developer.github.com/v3/#rate-limiting">API documentation from GitHub</a>
     */
    public abstract void onError(IOException e, HttpURLConnection uc) throws IOException;

    /**
     * Block until the API rate limit is reset. Useful for long-running batch processing.
     */
    public static final RateLimitHandler WAIT = new RateLimitHandler() {
        @Override
        public void onError(IOException e, HttpURLConnection uc) throws IOException {
            try {
                Thread.sleep(parseWaitTime(uc));
            } catch (InterruptedException x) {
                throw (InterruptedIOException) new InterruptedIOException().initCause(e);
            }
        }

        private long parseWaitTime(HttpURLConnection uc) {
            String v = uc.getHeaderField("X-RateLimit-Reset");
            if (v == null)
                return 10000; // can't tell

            return Math.max(10000, Long.parseLong(v) * 1000 - System.currentTimeMillis());
        }
    };

    /**
     * Fail immediately.
     */
    public static final RateLimitHandler FAIL = new RateLimitHandler() {
        @Override
        public void onError(IOException e, HttpURLConnection uc) throws IOException {
            throw (IOException) new IOException("API rate limit reached").initCause(e);
        }
    };
}
