/*
 * Copyright (c) 2009, PostgreSQL Global Development Group
 * See the LICENSE file in the project root for more information.
 */

package org.postgresql.copy;

import org.postgresql.PGConnection;
import org.postgresql.util.GT;
import org.postgresql.util.PSQLException;
import org.postgresql.util.PSQLState;

import java.io.IOException;
import java.io.InputStream;
import java.sql.SQLException;

/**
 * InputStream for reading from a PostgreSQL COPY TO STDOUT operation.
 */
public class PGCopyInputStream extends InputStream implements CopyOut {
  private CopyOut op;
  private byte[] buf;
  private int at;
  private int len;

  /**
   * Uses given connection for specified COPY TO STDOUT operation.
   *
   * @param connection database connection to use for copying (protocol version 3 required)
   * @param sql COPY TO STDOUT statement
   * @throws SQLException if initializing the operation fails
   */
  public PGCopyInputStream(PGConnection connection, String sql) throws SQLException {
    this(connection.getCopyAPI().copyOut(sql));
  }

  /**
   * Use given CopyOut operation for reading.
   *
   * @param op COPY TO STDOUT operation
   */
  public PGCopyInputStream(CopyOut op) {
    this.op = op;
  }

  private boolean gotBuf() throws IOException {
    if (at >= len) {
      try {
        buf = op.readFromCopy();
      } catch (SQLException sqle) {
        throw new IOException(GT.tr("Copying from database failed: {0}", sqle));
      }
      if (buf == null) {
        at = -1;
        return false;
      } else {
        at = 0;
        len = buf.length;
        return true;
      }
    }
    return buf != null;
  }

  private void checkClosed() throws IOException {
    if (op == null) {
      throw new IOException(GT.tr("This copy stream is closed."));
    }
  }


  public int available() throws IOException {
    checkClosed();
    return (buf != null ? len - at : 0);
  }

  public int read() throws IOException {
    checkClosed();
    return gotBuf() ? buf[at++] : -1;
  }

  public int read(byte[] buf) throws IOException {
    return read(buf, 0, buf.length);
  }

  public int read(byte[] buf, int off, int siz) throws IOException {
    checkClosed();
    int got = 0;
    boolean didReadSomething = false;
    while (got < siz && (didReadSomething = gotBuf())) {
      buf[off + got++] = this.buf[at++];
    }
    return got == 0 && !didReadSomething ? -1 : got;
  }

  public byte[] readFromCopy() throws SQLException {
    byte[] result = buf;
    try {
      if (gotBuf()) {
        if (at > 0 || len < buf.length) {
          byte[] ba = new byte[len - at];
          for (int i = at; i < len; i++) {
            ba[i - at] = buf[i];
          }
          result = ba;
        }
        at = len; // either partly or fully returned, buffer is exhausted
      }
    } catch (IOException ioe) {
      throw new PSQLException(GT.tr("Read from copy failed."), PSQLState.CONNECTION_FAILURE);
    }
    return result;
  }

  @Override
  public byte[] readFromCopy(boolean block) throws SQLException {
    return readFromCopy();
  }

  public void close() throws IOException {
    // Don't complain about a double close.
    if (op == null) {
      return;
    }

    if (op.isActive()) {
      try {
        op.cancelCopy();
      } catch (SQLException se) {
        IOException ioe = new IOException("Failed to close copy reader.");
        ioe.initCause(se);
        throw ioe;
      }
    }
    op = null;
  }

  public void cancelCopy() throws SQLException {
    op.cancelCopy();
  }

  public int getFormat() {
    return op.getFormat();
  }

  public int getFieldFormat(int field) {
    return op.getFieldFormat(field);
  }

  public int getFieldCount() {
    return op.getFieldCount();
  }

  public boolean isActive() {
    return op != null && op.isActive();
  }

  public long getHandledRowCount() {
    return op.getHandledRowCount();
  }
}
