package org.ovirt.engine.core.bll;

import java.util.Set;

import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;

import org.ovirt.engine.core.bll.interfaces.BackendInternal;
import org.ovirt.engine.core.bll.session.SessionDataContainer;
import org.ovirt.engine.core.common.errors.VdcBLLException;
import org.ovirt.engine.core.common.interfaces.IVdcUser;
import org.ovirt.engine.core.common.queries.VdcQueryParametersBase;
import org.ovirt.engine.core.common.queries.VdcQueryReturnValue;
import org.ovirt.engine.core.common.queries.VdcQueryType;
import org.ovirt.engine.core.compat.Guid;
import org.ovirt.engine.core.dal.VdcCommandBase;
import org.ovirt.engine.core.dal.dbbroker.DbFacade;
import org.ovirt.engine.core.dao.ActionGroupDAO;
import org.ovirt.engine.core.dao.VdsDAO;
import org.ovirt.engine.core.utils.log.Logged;
import org.ovirt.engine.core.utils.log.Logged.LogLevel;

@Logged(executionLevel = LogLevel.TRACE, errorLevel = LogLevel.WARN)
public abstract class QueriesCommandBase<P extends VdcQueryParametersBase> extends VdcCommandBase {

    private final static Validator validator = Validation.buildDefaultValidatorFactory().getValidator();
    private static final String QuerySuffix = "Query";

    /**
     * Factory to determine the type of the ReturnValue field
     */
    protected VdcQueryReturnValue createReturnValue() {
        return new VdcQueryReturnValue();
    }

    // get correct return value type
    private final VdcQueryReturnValue returnValue;
    private final VdcQueryType queryType;
    private final IVdcUser user;
    private final P parameters;
    private boolean isInternalExecution = false;

    public QueriesCommandBase(P parameters) {
        this.parameters = parameters;
        returnValue = createReturnValue();
        queryType = initQueryType();
        user = initUser();
    }

    private final VdcQueryType initQueryType() {
        try {
            String name = getClass().getSimpleName();
            name = name.substring(0, name.length() - QuerySuffix.length());
            return VdcQueryType.valueOf(name);
        } catch (Exception e) {
            return VdcQueryType.Unknown;
        }
    }

    private final IVdcUser initUser() {
        return SessionDataContainer.getInstance().addUserToThreadContext(parameters.getSessionId(),
                parameters.getRefresh());
    }

    @Override
    protected void ExecuteCommand() {
        if (validatePermissions()) {
            if (validateInputs()) {
                try {
                    returnValue.setSucceeded(true);
                    executeQueryCommand();
                } catch (RuntimeException ex) {
                    returnValue.setSucceeded(false);
                    Throwable th = ex instanceof VdcBLLException ? ex : ex.getCause();
                    if (th != null && th instanceof VdcBLLException) {
                        VdcBLLException vdcExc = (VdcBLLException) th;
                        if (vdcExc.getErrorCode() != null) {
                            returnValue.setExceptionString(vdcExc.getErrorCode().toString());
                        } else {
                            returnValue.setExceptionString(vdcExc.getMessage());
                        }
                        log.errorFormat("Query {0} failed. Exception message is {1}",
                                getClass().getSimpleName(),
                                vdcExc.getMessage());
                        if (log.isDebugEnabled()) {
                            log.debugFormat("Detailed stacktrace:", vdcExc);
                        }
                    } else {
                        returnValue.setExceptionString(ex.getMessage());
                        log.errorFormat("Query {0} failed. Exception message is {1}",
                                getClass().getSimpleName(),
                                ex.getMessage());
                        if (log.isDebugEnabled()) {
                            log.debugFormat("Detailed stacktrace:", ex);
                        }
                    }
                }
            } else {
                log.error("Query execution failed due to invalid inputs. " + returnValue.getExceptionString());
            }
        } else {
            String errMessage = "Query execution failed due to insufficient permissions.";
            log.error(errMessage);
            returnValue.setExceptionString(errMessage);
        }
    }

    /**
    * Validates if this query is permitted to run.
    *
    * @return <code>true</code> if the query is OK (i.e., the issuing user has enough permissions to execute it), or
    *         <code>false</code> otherwise.
    */
    private final boolean validatePermissions() {
        // If the user requests filtered execution, his permissions are inconsequential.
        // If the query supports filtering it should be allowed, and if not - not.
        if (parameters.isFiltered()) {
            return !queryType.isAdmin();
        }

        // If the query was executed internally, it should be allowed in any event.
        if (isInternalExecution) {
            return true;
        }

        // In any other event, we have admin execution, which should only be allowed according to the user's
        // permissions.
        // Note that is cached per session
        return getUser().isAdmin();
    }

    /**
     * @return true if all parameters class and its inner members passed
     *         validation
     */
    protected boolean validateInputs() {
        Set<ConstraintViolation<P>> violations = validator.validate(getParameters());
        if (!violations.isEmpty()) {
            returnValue.setExceptionString(violations.toString());
            return false;
        }
        return true;
    }

    protected void ProceedOnFail() {
        // Empty default implementation, method is here to allow inheriting classes to override.
    }

    public VdcQueryReturnValue getQueryReturnValue() {
        return returnValue;
    }

    public P getParameters() {
        return parameters;
    }

    @Override
    public String toString() {
        return String.format("%s(%s)", super.toString(),
                (getParameters() != null ? getParameters().toString() : "null"));
    }

    protected abstract void executeQueryCommand();

    @Override
    public void setReturnValue(Object value) {
        returnValue.setReturnValue(value);
    }

    public boolean isInternalExecution() {
        return isInternalExecution;
    }

    public void setInternalExecution(boolean isInternalExecution) {
        this.isInternalExecution = isInternalExecution;
    }

    protected IVdcUser getUser() {
        return user;
    }

    protected Guid getUserID() {
        if (user == null) {
            return null;
        }
        return user.getUserId();
    }

    protected DbFacade getDbFacade() {
        return DbFacade.getInstance();
    }

    protected ActionGroupDAO getActionGroupDao() {
        return getDbFacade().getActionGroupDao();
    }

    public VdsDAO getVdsDao() {
        return DbFacade.getInstance().getVdsDao();
    }

    protected BackendInternal getBackend() {
        return Backend.getInstance();
    }

}
