package org.jboss.resteasy.plugins.providers;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;

import jakarta.ws.rs.WebApplicationException;
import jakarta.ws.rs.core.MediaType;
import jakarta.ws.rs.core.MultivaluedMap;
import jakarta.ws.rs.ext.Provider;

import org.jboss.resteasy.spi.AsyncMessageBodyWriter;
import org.jboss.resteasy.spi.AsyncOutputStream;
import org.jboss.resteasy.util.MediaTypeHelper;

import com.ibm.asyncutil.iteration.AsyncTrampoline;

/**
 * @author <a href="mailto:bill@burkecentral.com">Bill Burke</a>
 * @version $Revision: 1 $
 */
@Provider
public class FileRangeWriter implements AsyncMessageBodyWriter<FileRange> {
    @Override
    public boolean isWriteable(Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return type.equals(FileRange.class) && !MediaTypeHelper.isBlacklisted(mediaType);
    }

    @Override
    public long getSize(FileRange fileRange, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType) {
        return -1;
    }

    @Override
    public void writeTo(FileRange fileRange, Class<?> type, Type genericType, Annotation[] annotations, MediaType mediaType,
            MultivaluedMap<String, Object> httpHeaders, OutputStream entityStream) throws IOException, WebApplicationException {
        long fileSize = fileRange.getFile().length();
        String contentRange = "bytes " + fileRange.getBegin() + "-" + fileRange.getEnd() + "/" + fileSize;
        long length = (fileRange.getEnd() - fileRange.getBegin()) + 1;
        httpHeaders.putSingle("Content-Range", contentRange);
        httpHeaders.putSingle("Content-Length", length);
        FileInputStream fis = new FileInputStream(fileRange.getFile());
        try {
            if (fileRange.getBegin() > 0) {
                fis.getChannel().position(fileRange.getBegin());
            }
            final byte[] buf = new byte[2048];
            while (length > 0) {
                int len = 2048 > length ? (int) length : 2048;
                int read = fis.read(buf, 0, len);
                if (read == -1) {
                    break;
                }
                entityStream.write(buf, 0, read);
                length -= len;
            }
        } finally {
            fis.close();
        }

    }

    @Override
    public CompletionStage<Void> asyncWriteTo(FileRange fileRange, Class<?> type, Type genericType, Annotation[] annotations,
            MediaType mediaType, MultivaluedMap<String, Object> httpHeaders,
            AsyncOutputStream entityStream) {
        long fileSize = fileRange.getFile().length();
        String contentRange = "bytes " + fileRange.getBegin() + "-" + fileRange.getEnd() + "/" + fileSize;
        long length = (fileRange.getEnd() - fileRange.getBegin()) + 1;
        httpHeaders.putSingle("Content-Range", contentRange);
        httpHeaders.putSingle("Content-Length", length);
        try {
            FileInputStream fis = new FileInputStream(fileRange.getFile());
            if (fileRange.getBegin() > 0) {
                fis.getChannel().position(fileRange.getBegin());
            }
            final byte[] buf = new byte[2048];
            return writeTo(fis, length, entityStream, buf)
                    .whenComplete((v, t) -> {
                        try {
                            fis.close();
                        } catch (IOException e) {
                            throw new RuntimeException(e);
                        }
                    });
        } catch (IOException e) {
            return ProviderHelper.completedException(e);
        }
    }

    private CompletionStage<Void> writeTo(FileInputStream fis, long length, AsyncOutputStream entityStream, byte[] buf) {
        if (length > 0) {
            long[] mutableLength = new long[] { length };
            return AsyncTrampoline.asyncWhile(
                    read -> read != -1,
                    read -> entityStream.asyncWrite(buf, 0, read)
                            .thenApply(v -> {
                                mutableLength[0] -= read;
                                if (mutableLength[0] > 0)
                                    return ProviderHelper.asyncRead(fis, buf, 0, (int) Math.min(buf.length, mutableLength[0]));
                                // simulate EOF to exit the loop
                                return -1;
                            }),
                    ProviderHelper.asyncRead(fis, buf, 0, (int) Math.min(buf.length, mutableLength[0]))).thenApply(v -> null);
        }
        return CompletableFuture.completedFuture(null);
    }
}
