/*
    * Copyright (C) 2019, Google LLC. 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.transport;
  
  import static java.math.BigInteger.ZERO;
  import static java.util.Objects.requireNonNull;
  import static org.eclipse.jgit.lib.Constants.OBJ_BLOB;
  import static org.eclipse.jgit.lib.Constants.OBJ_COMMIT;
  import static org.eclipse.jgit.lib.Constants.OBJ_TAG;
  import static org.eclipse.jgit.lib.Constants.OBJ_TREE;
  import static org.eclipse.jgit.transport.GitProtocolConstants.OPTION_FILTER;
  
  import java.math.BigInteger;
  import java.text.MessageFormat;
  
  import org.eclipse.jgit.annotations.Nullable;
  import org.eclipse.jgit.errors.PackProtocolException;
  import org.eclipse.jgit.internal.JGitText;
  
  /**
   * Represents either a filter specified in a protocol "filter" line, or a
   * placeholder to indicate no filtering.
   *
   * @since 5.4
   */
  public final class FilterSpec {
  
  	/** Immutable bit-set representation of a set of Git object types. */
  	static class ObjectTypes {
  		static ObjectTypes ALL = allow(OBJ_BLOB, OBJ_TREE, OBJ_COMMIT, OBJ_TAG);
  
  		private final BigInteger val;
  
  		private ObjectTypes(BigInteger val) {
  			this.val = requireNonNull(val);
  		}
  
  		static ObjectTypes allow(int... types) {
  			BigInteger bits = ZERO;
  			for (int type : types) {
  				bits = bits.setBit(type);
  			}
  			return new ObjectTypes(bits);
  		}
  
  		boolean contains(int type) {
  			return val.testBit(type);
  		}
  
  		/** {@inheritDoc} */
  		@Override
  		public boolean equals(Object obj) {
  			if (!(obj instanceof ObjectTypes)) {
  				return false;
  			}
  
  			ObjectTypes other = (ObjectTypes) obj;
  			return other.val.equals(val);
  		}
  
  		/** {@inheritDoc} */
  		@Override
  		public int hashCode() {
  			return val.hashCode();
  		}
  	}
  
  	private final ObjectTypes types;
  
  	private final long blobLimit;
  
  	private final long treeDepthLimit;
  
  	private FilterSpec(ObjectTypes types, long blobLimit, long treeDepthLimit) {
  		this.types = requireNonNull(types);
  		this.blobLimit = blobLimit;
  		this.treeDepthLimit = treeDepthLimit;
  	}
  
  	/**
  	 * Process the content of "filter" line from the protocol. It has a shape
  	 * like:
  	 *
  	 * <ul>
  	 *   <li>"blob:none"
  	 *   <li>"blob:limit=N", with N &gt;= 0
  	 *   <li>"tree:DEPTH", with DEPTH &gt;= 0
  	 * </ul>
  	 *
  	 * @param filterLine
  	 *            the content of the "filter" line in the protocol
 	 * @return a FilterSpec representing the given filter
 	 * @throws PackProtocolException
 	 *             invalid filter because due to unrecognized format or
 	 *             negative/non-numeric filter.
 	 */
 	public static FilterSpec fromFilterLine(String filterLine)
 			throws PackProtocolException {
 		if (filterLine.equals("blob:none")) { //$NON-NLS-1$
 			return FilterSpec.withObjectTypes(
 					ObjectTypes.allow(OBJ_TREE, OBJ_COMMIT, OBJ_TAG));
 		} else if (filterLine.startsWith("blob:limit=")) { //$NON-NLS-1$
 			long blobLimit = -1;
 			try {
 				blobLimit = Long
 						.parseLong(filterLine.substring("blob:limit=".length())); //$NON-NLS-1$
 			} catch (NumberFormatException e) {
 				// Do not change blobLimit so that we throw a
 				// PackProtocolException later.
 			}
 			if (blobLimit >= 0) {
 				return FilterSpec.withBlobLimit(blobLimit);
 			}
 		} else if (filterLine.startsWith("tree:")) { //$NON-NLS-1$
 			long treeDepthLimit = -1;
 			try {
 				treeDepthLimit = Long
 						.parseLong(filterLine.substring("tree:".length())); //$NON-NLS-1$
 			} catch (NumberFormatException e) {
 				// Do not change blobLimit so that we throw a
 				// PackProtocolException later.
 			}
 			if (treeDepthLimit >= 0) {
 				return FilterSpec.withTreeDepthLimit(treeDepthLimit);
 			}
 		}
 
 		// Did not match any known filter format.
 		throw new PackProtocolException(
 				MessageFormat.format(JGitText.get().invalidFilter, filterLine));
 	}
 
 	/**
 	 * @param types
 	 *            set of permitted object types, for use in "blob:none" and
 	 *            "object:none" filters
 	 * @return a filter spec which restricts to objects of the specified types
 	 */
 	static FilterSpec withObjectTypes(ObjectTypes types) {
 		return new FilterSpec(types, -1, -1);
 	}
 
 	/**
 	 * @param blobLimit
 	 *            the blob limit in a "blob:[limit]" filter line
 	 * @return a filter spec which filters blobs above a certain size
 	 */
 	static FilterSpec withBlobLimit(long blobLimit) {
 		if (blobLimit < 0) {
 			throw new IllegalArgumentException(
 					"blobLimit cannot be negative: " + blobLimit); //$NON-NLS-1$
 		}
 		return new FilterSpec(ObjectTypes.ALL, blobLimit, -1);
 	}
 
 	/**
 	 * @param treeDepthLimit
 	 *            the tree depth limit in a "tree:[depth]" filter line
 	 * @return a filter spec which filters blobs and trees beyond a certain tree
 	 *         depth
 	 */
 	static FilterSpec withTreeDepthLimit(long treeDepthLimit) {
 		if (treeDepthLimit < 0) {
 			throw new IllegalArgumentException(
 					"treeDepthLimit cannot be negative: " + treeDepthLimit); //$NON-NLS-1$
 		}
 		return new FilterSpec(ObjectTypes.ALL, -1, treeDepthLimit);
 	}
 
 	/**
 	 * A placeholder that indicates no filtering.
 	 */
 	public static final FilterSpecec.html#FilterSpec">FilterSpec NO_FILTER = new FilterSpec(ObjectTypes.ALL, -1, -1);
 
 	/**
 	 * @param type
 	 *            a Git object type, such as
 	 *            {@link org.eclipse.jgit.lib.Constants#OBJ_BLOB}
 	 * @return whether this filter allows objects of the specified type
 	 *
 	 * @since 5.9
 	 */
 	public boolean allowsType(int type) {
 		return types.contains(type);
 	}
 
 	/**
 	 * @return -1 if this filter does not filter blobs based on size, or a
 	 *         non-negative integer representing the max size of blobs to allow
 	 */
 	public long getBlobLimit() {
 		return blobLimit;
 	}
 
 	/**
 	 * @return -1 if this filter does not filter blobs and trees based on depth,
 	 *         or a non-negative integer representing the max tree depth of
 	 *         blobs and trees to fetch
 	 */
 	public long getTreeDepthLimit() {
 		return treeDepthLimit;
 	}
 
 	/**
 	 * @return true if this filter doesn't filter out anything
 	 */
 	public boolean isNoOp() {
 		return types.equals(ObjectTypes.ALL) && blobLimit == -1 && treeDepthLimit == -1;
 	}
 
 	/**
 	 * @return the filter line which describes this spec, e.g. "filter blob:limit=42"
 	 */
 	@Nullable
 	public String filterLine() {
 		if (isNoOp()) {
 			return null;
 		} else if (types.equals(ObjectTypes.allow(OBJ_TREE, OBJ_COMMIT, OBJ_TAG)) &&
 					blobLimit == -1 && treeDepthLimit == -1) {
 			return OPTION_FILTER + " blob:none"; //$NON-NLS-1$
 		} else if (types.equals(ObjectTypes.ALL) && blobLimit >= 0 && treeDepthLimit == -1) {
 			return OPTION_FILTER + " blob:limit=" + blobLimit; //$NON-NLS-1$
 		} else if (types.equals(ObjectTypes.ALL) && blobLimit == -1 && treeDepthLimit >= 0) {
 			return OPTION_FILTER + " tree:" + treeDepthLimit; //$NON-NLS-1$
 		} else {
 			throw new IllegalStateException();
 		}
 	}
 }