/*******************************************************************************
 * Copyright (c) 2007, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.equinox.internal.provisional.p2.engine;

import java.util.*;
import org.eclipse.core.runtime.*;
import org.eclipse.equinox.internal.p2.engine.EngineActivator;

public abstract class Phase {
	protected static final String PARM_OPERAND = "operand"; //$NON-NLS-1$
	protected static final String PARM_PHASE_ID = "phaseId"; //$NON-NLS-1$
	protected static final String PARM_PROFILE = "profile"; //$NON-NLS-1$
	protected static final String PARM_CONTEXT = "context"; //$NON-NLS-1$

	protected final String phaseId;
	protected final int weight;
	protected int prePerformWork = 1000;
	protected int mainPerformWork = 10000;
	protected int postPerformWork = 1000;
	private Map phaseParameters;

	protected Phase(String phaseId, int weight) {
		if (phaseId == null || phaseId.length() == 0)
			throw new IllegalArgumentException(Messages.phaseid_not_set);
		if (weight <= 0)
			throw new IllegalArgumentException(Messages.phaseid_not_positive);
		this.weight = weight;
		this.phaseId = phaseId;
	}

	public String toString() {
		return getClass().getName() + " - " + this.weight; //$NON-NLS-1$
	}

	public final MultiStatus perform(EngineSession session, IProfile profile, Operand[] operands, ProvisioningContext context, IProgressMonitor monitor) {
		MultiStatus status = new MultiStatus(EngineActivator.ID, IStatus.OK, null, null);
		try {
			perform(status, session, profile, operands, context, monitor);
		} catch (OperationCanceledException e) {
			// propagate operation cancellation
			status.add(new Status(IStatus.CANCEL, EngineActivator.ID, e.getMessage(), e));
		} catch (RuntimeException e) {
			// "perform" calls user code and might throw an unchecked exception
			// we catch the error here to gather information on where the problem occurred.
			status.add(new Status(IStatus.ERROR, EngineActivator.ID, e.getMessage(), e));
		} catch (LinkageError e) {
			// Catch linkage errors as these are generally recoverable but let other Errors propagate (see bug 222001)
			status.add(new Status(IStatus.ERROR, EngineActivator.ID, e.getMessage(), e));
		}

		if (status.matches(IStatus.CANCEL)) {
			MultiStatus result = new MultiStatus(EngineActivator.ID, IStatus.CANCEL, Messages.Engine_Operation_Canceled_By_User, null);
			result.merge(status);
			return result;
		} else if (status.matches(IStatus.ERROR)) {
			MultiStatus result = new MultiStatus(EngineActivator.ID, IStatus.ERROR, getProblemMessage(), null);
			result.merge(status);
			return result;
		}
		return status;
	}

	void perform(MultiStatus status, EngineSession session, IProfile profile, Operand[] operands, ProvisioningContext context, IProgressMonitor monitor) {
		SubMonitor subMonitor = SubMonitor.convert(monitor, prePerformWork + mainPerformWork + postPerformWork);
		prePerform(status, profile, context, subMonitor.newChild(prePerformWork));
		if (status.matches(IStatus.ERROR | IStatus.CANCEL))
			return;
		session.recordPhaseStart(this);

		subMonitor.setWorkRemaining(mainPerformWork + postPerformWork);
		mainPerform(status, session, profile, operands, context, subMonitor.newChild(mainPerformWork));
		if (status.matches(IStatus.ERROR | IStatus.CANCEL))
			return;

		session.recordPhaseEnd(this);
		subMonitor.setWorkRemaining(postPerformWork);
		postPerform(status, profile, context, subMonitor.newChild(postPerformWork));
		if (status.matches(IStatus.ERROR | IStatus.CANCEL))
			return;

		subMonitor.done();
	}

	void prePerform(MultiStatus status, IProfile profile, ProvisioningContext context, IProgressMonitor monitor) {
		phaseParameters = new HashMap();
		phaseParameters.put(PARM_PROFILE, profile);
		phaseParameters.put(PARM_CONTEXT, context);
		phaseParameters.put(PARM_PHASE_ID, phaseId);

		mergeStatus(status, initializePhase(monitor, profile, phaseParameters));
	}

	private void mainPerform(MultiStatus status, EngineSession session, IProfile profile, Operand[] operands, ProvisioningContext context, SubMonitor subMonitor) {
		subMonitor.beginTask("", operands.length); //$NON-NLS-1$
		for (int i = 0; i < operands.length; i++) {
			subMonitor.setWorkRemaining(operands.length - i);
			if (subMonitor.isCanceled())
				throw new OperationCanceledException();
			Operand operand = operands[i];
			if (!isApplicable(operand))
				continue;

			ProvisioningAction[] actions = getActions(operand);
			Map parameters = new HashMap(phaseParameters);
			parameters.put(PARM_OPERAND, operand);
			mergeStatus(status, initializeOperand(profile, operand, parameters, subMonitor));
			if (status.matches(IStatus.ERROR | IStatus.CANCEL))
				return;
			parameters = Collections.unmodifiableMap(parameters);
			if (actions != null) {
				for (int j = 0; j < actions.length; j++) {
					ProvisioningAction action = actions[j];
					session.recordAction(action, operand);
					mergeStatus(status, action.execute(parameters));
					if (status.matches(IStatus.ERROR | IStatus.CANCEL))
						return;
				}
			}
			mergeStatus(status, completeOperand(profile, operand, parameters, subMonitor));
			if (status.matches(IStatus.ERROR | IStatus.CANCEL))
				return;
			subMonitor.worked(1);
		}
	}

	/**
	 * Merges a given IStatus into a MultiStatus
	 */
	protected static void mergeStatus(MultiStatus multi, IStatus status) {
		if (status != null && !status.isOK())
			multi.merge(status);
	}

	void postPerform(MultiStatus status, IProfile profile, ProvisioningContext context, IProgressMonitor monitor) {
		mergeStatus(status, completePhase(monitor, profile, phaseParameters));
		phaseParameters = null;
	}

	void undo(MultiStatus status, EngineSession session, IProfile profile, Operand operand, ProvisioningAction[] actions, ProvisioningContext context) {
		Map parameters = new HashMap(phaseParameters);
		parameters.put(PARM_OPERAND, operand);
		mergeStatus(status, initializeOperand(profile, operand, parameters, new NullProgressMonitor()));
		parameters = Collections.unmodifiableMap(parameters);
		for (int j = 0; j < actions.length; j++) {
			ProvisioningAction action = actions[j];
			mergeStatus(status, action.undo(parameters));
			// TODO: session.removeAction(...)
		}
		mergeStatus(status, completeOperand(profile, operand, parameters, new NullProgressMonitor()));
	}

	protected boolean isApplicable(Operand operand) {
		return true;
	}

	protected IStatus initializePhase(IProgressMonitor monitor, IProfile profile, Map parameters) {
		return Status.OK_STATUS;
	}

	protected IStatus completePhase(IProgressMonitor monitor, IProfile profile, Map parameters) {
		return Status.OK_STATUS;
	}

	protected IStatus completeOperand(IProfile profile, Operand operand, Map parameters, IProgressMonitor monitor) {
		return Status.OK_STATUS;
	}

	protected IStatus initializeOperand(IProfile profile, Operand operand, Map parameters, IProgressMonitor monitor) {
		return Status.OK_STATUS;
	}

	protected abstract ProvisioningAction[] getActions(Operand operand);

	/**
	 * Returns a human-readable message to be displayed in case of an error performing
	 * this phase. Subclasses should override.
	 */
	protected String getProblemMessage() {
		return Messages.phase_error;
	}

}