/*
    * Copyright (C) 2015, 2022 Ivan Motsch <ivan.motsch@bsiag.com> and others
    *
    * This program and the accompanying materials are made available under the
    * terms of the Eclipse Distribution License v. 1.0 which is available at
    * https://www.eclipse.org/org/documents/edl-v10.php.
    *
    * SPDX-License-Identifier: BSD-3-Clause
    */
  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 java.util.function.Supplier;
  
  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 Supplier<CanonicalTreeParser> attributesTree;
  
  	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
  	 * @deprecated since 6.1, use {@link #AttributesHandler(TreeWalk, Supplier)}
  	 *             instead
  	 */
  	@Deprecated
  	public AttributesHandler(TreeWalk treeWalk) throws IOException {
  		this(treeWalk, () -> treeWalk.getTree(CanonicalTreeParser.class));
  	}
  
  	/**
  	 * 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}
  	 * @param attributesTree
  	 *            the tree to read .gitattributes from
  	 * @throws java.io.IOException
  	 * @since 6.1
  	 */
  	public AttributesHandler(TreeWalk treeWalk,
  			Supplier<CanonicalTreeParser> attributesTree) throws IOException {
  		this.treeWalk = treeWalk;
  		this.attributesTree = attributesTree;
  		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(attributesTree.get()));
 
 		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),
 				attributesTree.get(),
 				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;
 	}
 
 }