AttributesHandler.java

/*
 * Copyright (C) 2015, Ivan Motsch <ivan.motsch@bsiag.com>
 *
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Distribution License v1.0 which
 * accompanies this distribution, is reproduced below, and is
 * available at http://www.eclipse.org/org/documents/edl-v10.php
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or
 * without modification, are permitted provided that the following
 * conditions are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above
 *   copyright notice, this list of conditions and the following
 *   disclaimer in the documentation and/or other materials provided
 *   with the distribution.
 *
 * - Neither the name of the Eclipse Foundation, Inc. nor the
 *   names of its contributors may be used to endorse or promote
 *   products derived from this software without specific prior
 *   written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
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package org.eclipse.jgit.attributes;

import java.io.IOException;
import java.util.HashMap;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;

import org.eclipse.jgit.annotations.Nullable;
import org.eclipse.jgit.attributes.Attribute.State;
import org.eclipse.jgit.dircache.DirCacheIterator;
import org.eclipse.jgit.lib.FileMode;
import org.eclipse.jgit.treewalk.AbstractTreeIterator;
import org.eclipse.jgit.treewalk.CanonicalTreeParser;
import org.eclipse.jgit.treewalk.TreeWalk;
import org.eclipse.jgit.treewalk.TreeWalk.OperationType;
import org.eclipse.jgit.treewalk.WorkingTreeIterator;

/**
 * The attributes handler knows how to retrieve, parse and merge attributes from
 * the various gitattributes files. Furthermore it collects and expands macro
 * expressions. The method {@link #getAttributes()} yields the ready processed
 * attributes for the current path represented by the
 * {@link org.eclipse.jgit.treewalk.TreeWalk}
 * <p>
 * The implementation is based on the specifications in
 * http://git-scm.com/docs/gitattributes
 *
 * @since 4.3
 */
public class AttributesHandler {
    private static final String MACRO_PREFIX = "[attr]"; //$NON-NLS-1$

    private static final String BINARY_RULE_KEY = "binary"; //$NON-NLS-1$

    /**
     * This is the default <b>binary</b> rule that is present in any git folder
     * <code>[attr]binary -diff -merge -text</code>
     */
    private static final List<Attribute> BINARY_RULE_ATTRIBUTES = new AttributesRule(
            MACRO_PREFIX + BINARY_RULE_KEY, "-diff -merge -text") //$NON-NLS-1$
                    .getAttributes();

    private final TreeWalk treeWalk;

    private final AttributesNode globalNode;

    private final AttributesNode infoNode;

    private final Map<String, List<Attribute>> expansions = new HashMap<>();

    /**
     * Create an {@link org.eclipse.jgit.attributes.AttributesHandler} with
     * default rules as well as merged rules from global, info and worktree root
     * attributes
     *
     * @param treeWalk
     *            a {@link org.eclipse.jgit.treewalk.TreeWalk}
     * @throws java.io.IOException
     */
    public AttributesHandler(TreeWalk treeWalk) throws IOException {
        this.treeWalk = treeWalk;
        AttributesNodeProvider attributesNodeProvider =treeWalk.getAttributesNodeProvider();
        this.globalNode = attributesNodeProvider != null
                ? attributesNodeProvider.getGlobalAttributesNode() : null;
        this.infoNode = attributesNodeProvider != null
                ? attributesNodeProvider.getInfoAttributesNode() : null;

        AttributesNode rootNode = attributesNode(treeWalk,
                rootOf(
                        treeWalk.getTree(WorkingTreeIterator.class)),
                rootOf(
                        treeWalk.getTree(DirCacheIterator.class)),
                rootOf(treeWalk
                        .getTree(CanonicalTreeParser.class)));

        expansions.put(BINARY_RULE_KEY, BINARY_RULE_ATTRIBUTES);
        for (AttributesNode node : new AttributesNode[] { globalNode, rootNode,
                infoNode }) {
            if (node == null) {
                continue;
            }
            for (AttributesRule rule : node.getRules()) {
                if (rule.getPattern().startsWith(MACRO_PREFIX)) {
                    expansions.put(rule.getPattern()
                            .substring(MACRO_PREFIX.length()).trim(),
                            rule.getAttributes());
                }
            }
        }
    }

    /**
     * See {@link org.eclipse.jgit.treewalk.TreeWalk#getAttributes()}
     *
     * @return the {@link org.eclipse.jgit.attributes.Attributes} for the
     *         current path represented by the
     *         {@link org.eclipse.jgit.treewalk.TreeWalk}
     * @throws java.io.IOException
     */
    public Attributes getAttributes() throws IOException {
        String entryPath = treeWalk.getPathString();
        boolean isDirectory = (treeWalk.getFileMode() == FileMode.TREE);
        Attributes attributes = new Attributes();

        // Gets the info attributes
        mergeInfoAttributes(entryPath, isDirectory, attributes);

        // Gets the attributes located on the current entry path
        mergePerDirectoryEntryAttributes(entryPath, entryPath.lastIndexOf('/'),
                isDirectory,
                treeWalk.getTree(WorkingTreeIterator.class),
                treeWalk.getTree(DirCacheIterator.class),
                treeWalk.getTree(CanonicalTreeParser.class),
                attributes);

        // Gets the attributes located in the global attribute file
        mergeGlobalAttributes(entryPath, isDirectory, attributes);

        // now after all attributes are collected - in the correct hierarchy
        // order - remove all unspecified entries (the ! marker)
        for (Attribute a : attributes.getAll()) {
            if (a.getState() == State.UNSPECIFIED)
                attributes.remove(a.getKey());
        }

        return attributes;
    }

    /**
     * Merges the matching GLOBAL attributes for an entry path.
     *
     * @param entryPath
     *            the path to test. The path must be relative to this attribute
     *            node's own repository path, and in repository path format
     *            (uses '/' and not '\').
     * @param isDirectory
     *            true if the target item is a directory.
     * @param result
     *            that will hold the attributes matching this entry path. This
     *            method will NOT override any existing entry in attributes.
     */
    private void mergeGlobalAttributes(String entryPath, boolean isDirectory,
            Attributes result) {
        mergeAttributes(globalNode, entryPath, isDirectory, result);
    }

    /**
     * Merges the matching INFO attributes for an entry path.
     *
     * @param entryPath
     *            the path to test. The path must be relative to this attribute
     *            node's own repository path, and in repository path format
     *            (uses '/' and not '\').
     * @param isDirectory
     *            true if the target item is a directory.
     * @param result
     *            that will hold the attributes matching this entry path. This
     *            method will NOT override any existing entry in attributes.
     */
    private void mergeInfoAttributes(String entryPath, boolean isDirectory,
            Attributes result) {
        mergeAttributes(infoNode, entryPath, isDirectory, result);
    }

    /**
     * Merges the matching working directory attributes for an entry path.
     *
     * @param entryPath
     *            the path to test. The path must be relative to this attribute
     *            node's own repository path, and in repository path format
     *            (uses '/' and not '\').
     * @param nameRoot
     *            index of the '/' preceeding the current level, or -1 if none
     * @param isDirectory
     *            true if the target item is a directory.
     * @param workingTreeIterator
     * @param dirCacheIterator
     * @param otherTree
     * @param result
     *            that will hold the attributes matching this entry path. This
     *            method will NOT override any existing entry in attributes.
     * @throws IOException
     */
    private void mergePerDirectoryEntryAttributes(String entryPath,
            int nameRoot, boolean isDirectory,
            @Nullable WorkingTreeIterator workingTreeIterator,
            @Nullable DirCacheIterator dirCacheIterator,
            @Nullable CanonicalTreeParser otherTree, Attributes result)
                    throws IOException {
        // Prevents infinite recurrence
        if (workingTreeIterator != null || dirCacheIterator != null
                || otherTree != null) {
            AttributesNode attributesNode = attributesNode(
                    treeWalk, workingTreeIterator, dirCacheIterator, otherTree);
            if (attributesNode != null) {
                mergeAttributes(attributesNode,
                        entryPath.substring(nameRoot + 1), isDirectory,
                        result);
            }
            mergePerDirectoryEntryAttributes(entryPath,
                    entryPath.lastIndexOf('/', nameRoot - 1), isDirectory,
                    parentOf(workingTreeIterator), parentOf(dirCacheIterator),
                    parentOf(otherTree), result);
        }
    }

    /**
     * Merges the matching node attributes for an entry path.
     *
     * @param node
     *            the node to scan for matches to entryPath
     * @param entryPath
     *            the path to test. The path must be relative to this attribute
     *            node's own repository path, and in repository path format
     *            (uses '/' and not '\').
     * @param isDirectory
     *            true if the target item is a directory.
     * @param result
     *            that will hold the attributes matching this entry path. This
     *            method will NOT override any existing entry in attributes.
     */
    protected void mergeAttributes(@Nullable AttributesNode node,
            String entryPath,
            boolean isDirectory, Attributes result) {
        if (node == null)
            return;
        List<AttributesRule> rules = node.getRules();
        // Parse rules in the reverse order that they were read since the last
        // entry should be used
        ListIterator<AttributesRule> ruleIterator = rules
                .listIterator(rules.size());
        while (ruleIterator.hasPrevious()) {
            AttributesRule rule = ruleIterator.previous();
            if (rule.isMatch(entryPath, isDirectory)) {
                ListIterator<Attribute> attributeIte = rule.getAttributes()
                        .listIterator(rule.getAttributes().size());
                // Parses the attributes in the reverse order that they were
                // read since the last entry should be used
                while (attributeIte.hasPrevious()) {
                    expandMacro(attributeIte.previous(), result);
                }
            }
        }
    }

    /**
     * Expand a macro
     *
     * @param attr
     *            a {@link org.eclipse.jgit.attributes.Attribute}
     * @param result
     *            contains the (recursive) expanded and merged macro attributes
     *            including the attribute iself
     */
    protected void expandMacro(Attribute attr, Attributes result) {
        // loop detection = exists check
        if (result.containsKey(attr.getKey()))
            return;

        // also add macro to result set, same does native git
        result.put(attr);

        List<Attribute> expansion = expansions.get(attr.getKey());
        if (expansion == null) {
            return;
        }
        switch (attr.getState()) {
        case UNSET: {
            for (Attribute e : expansion) {
                switch (e.getState()) {
                case SET:
                    expandMacro(new Attribute(e.getKey(), State.UNSET), result);
                    break;
                case UNSET:
                    expandMacro(new Attribute(e.getKey(), State.SET), result);
                    break;
                case UNSPECIFIED:
                    expandMacro(new Attribute(e.getKey(), State.UNSPECIFIED),
                            result);
                    break;
                case CUSTOM:
                default:
                    expandMacro(e, result);
                }
            }
            break;
        }
        case CUSTOM: {
            for (Attribute e : expansion) {
                switch (e.getState()) {
                case SET:
                case UNSET:
                case UNSPECIFIED:
                    expandMacro(e, result);
                    break;
                case CUSTOM:
                default:
                    expandMacro(new Attribute(e.getKey(), attr.getValue()),
                            result);
                }
            }
            break;
        }
        case UNSPECIFIED: {
            for (Attribute e : expansion) {
                expandMacro(new Attribute(e.getKey(), State.UNSPECIFIED),
                        result);
            }
            break;
        }
        case SET:
        default:
            for (Attribute e : expansion) {
                expandMacro(e, result);
            }
            break;
        }
    }

    /**
     * Get the {@link AttributesNode} for the current entry.
     * <p>
     * This method implements the fallback mechanism between the index and the
     * working tree depending on the operation type
     * </p>
     *
     * @param treeWalk
     * @param workingTreeIterator
     * @param dirCacheIterator
     * @param otherTree
     * @return a {@link AttributesNode} of the current entry,
     *         {@link NullPointerException} otherwise.
     * @throws IOException
     *             It raises an {@link IOException} if a problem appears while
     *             parsing one on the attributes file.
     */
    private static AttributesNode attributesNode(TreeWalk treeWalk,
            @Nullable WorkingTreeIterator workingTreeIterator,
            @Nullable DirCacheIterator dirCacheIterator,
            @Nullable CanonicalTreeParser otherTree) throws IOException {
        AttributesNode attributesNode = null;
        switch (treeWalk.getOperationType()) {
        case CHECKIN_OP:
            if (workingTreeIterator != null) {
                attributesNode = workingTreeIterator.getEntryAttributesNode();
            }
            if (attributesNode == null && dirCacheIterator != null) {
                attributesNode = dirCacheIterator
                        .getEntryAttributesNode(treeWalk.getObjectReader());
            }
            if (attributesNode == null && otherTree != null) {
                attributesNode = otherTree
                        .getEntryAttributesNode(treeWalk.getObjectReader());
            }
            break;
        case CHECKOUT_OP:
            if (otherTree != null) {
                attributesNode = otherTree
                        .getEntryAttributesNode(treeWalk.getObjectReader());
            }
            if (attributesNode == null && dirCacheIterator != null) {
                attributesNode = dirCacheIterator
                        .getEntryAttributesNode(treeWalk.getObjectReader());
            }
            if (attributesNode == null && workingTreeIterator != null) {
                attributesNode = workingTreeIterator.getEntryAttributesNode();
            }
            break;
        default:
            throw new IllegalStateException(
                    "The only supported operation types are:" //$NON-NLS-1$
                            + OperationType.CHECKIN_OP + "," //$NON-NLS-1$
                            + OperationType.CHECKOUT_OP);
        }

        return attributesNode;
    }

    private static <T extends AbstractTreeIterator> T parentOf(@Nullable T node) {
        if(node==null) return null;
        @SuppressWarnings("unchecked")
        Class<T> type = (Class<T>) node.getClass();
        AbstractTreeIterator parent = node.parent;
        if (type.isInstance(parent)) {
            return type.cast(parent);
        }
        return null;
    }

    private static <T extends AbstractTreeIterator> T rootOf(
            @Nullable T node) {
        if(node==null) return null;
        AbstractTreeIterator t=node;
        while (t!= null && t.parent != null) {
            t= t.parent;
        }
        @SuppressWarnings("unchecked")
        Class<T> type = (Class<T>) node.getClass();
        if (type.isInstance(t)) {
            return type.cast(t);
        }
        return null;
    }

}