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package ru.curs.celesta.dbutils;

import ru.curs.celesta.CelestaException;
import ru.curs.celesta.ICallContext;
import ru.curs.celesta.dbutils.adaptors.DBAdaptor;
import ru.curs.celesta.score.GrainElement;

import java.io.Closeable;
import java.sql.Connection;
import java.sql.SQLException;

public abstract class CsqlBasicDataAccessor implements Closeable {
    protected static final String DATA_ACCESSOR_IS_CLOSED = "DataAccessor is closed.";

    private final T context;
    private final Connection conn;
    private final DBAdaptor db;

    private boolean closed = false;


    public CsqlBasicDataAccessor(T context) {
        validateConnection(context);
        validateInitContext(context);
        this.context = context;
        this.conn = context.getConn();
        this.db = context.getDbAdaptor();
    }

    private static void validateConnection(ICallContext context) {
        try {
            if (context.getConn().isClosed()) {
                throw new CelestaException("Trying to create a cursor on closed connection.");
            }
        } catch (SQLException e) {
            throw new CelestaException(e.getMessage(), e);
        }
    }

    /**
     * Validates call context passed to data accessor constructor.
     */
    @SuppressWarnings("HiddenField")
    protected void validateInitContext(T context) {
        if (context == null) {
            throw new CelestaException(
                    "Invalid context passed to %s constructor: context should not be null.",
                    this.getClass().getName());
        }
        if (context.getConn() == null) {
            throw new CelestaException(
                    "Invalid context passed to %s constructor: connection is null.",
                    this.getClass().getName());
        }
        if (context.isClosed()) {
            throw new CelestaException("Cannot create %s on a closed CallContext.",
                    this.getClass().getName());
        }
    }

    /**
     * Returns call context that current cursor is created in.
     */
    public final T callContext() {
        return context;
    }

    protected final DBAdaptor db() {
        return db;
    }

    protected final Connection conn() {
        return conn;
    }

    /**
     * Whether data accessor object is closed.
     */
    public boolean isClosed() {
        return closed;
    }

    /**
     * Closes data accessor if it hasn't been closed already.
     */
    @Override
    public final void close() {
        if (!isClosed()) {
            closed = true;
            closeInternal();
        }
    }

    protected abstract void closeInternal();

    public abstract void clear();

    /**
     * Metadata object (table, view or sequence) on the basis of which current data object was created.
     */
    public abstract GrainElement meta();
}