/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package aQute.bnd.runtime.gogo;

import static aQute.bnd.runtime.gogo.Util.CWD;

import java.io.File;
import java.io.FileFilter;
import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.felix.service.command.CommandSession;
import org.apache.felix.service.command.Descriptor;
import org.osgi.framework.BundleContext;

import aQute.lib.dtoformatter.DTOFormatter;
import aQute.lib.io.IO;

public class Files {
	public Files(BundleContext bc, DTOFormatter formatter) {}

	@Descriptor("get current directory")
	public File cd(@Descriptor("automatically supplied shell session") CommandSession session) {
		try {
			return cd(session, null);
		} catch (IOException ex) {
			throw new RuntimeException("Unable to get current directory");
		}
	}

	@Descriptor("change current directory")
	public File cd(@Descriptor("automatically supplied shell session") CommandSession session,
		@Descriptor("target directory") String dir) throws IOException {
		File cwd = (File) session.get(CWD);
		if (cwd == null) {
			cwd = new File(".").getCanonicalFile();
			session.put(CWD, cwd);
		}
		if ((dir == null) || (dir.length() == 0)) {
			return cwd;
		}

		URI curUri = cwd.toURI();
		URI newUri = curUri.resolve(dir);

		cwd = new File(newUri);
		if (!cwd.exists()) {
			throw new IOException("Directory does not exist");
		} else if (!cwd.isDirectory()) {
			throw new IOException("Target is not a directory");
		}
		session.put(CWD, cwd.getCanonicalFile());
		return cwd;
	}

	@Descriptor("get current directory contents")
	public File[] ls(@Descriptor("automatically supplied shell session") CommandSession session) throws IOException {
		return ls(session, null);
	}

	@Descriptor("get specified path contents")
	public File[] ls(@Descriptor("automatically supplied shell session") CommandSession session,
		@Descriptor("path with optionally wildcarded file name") String pattern) throws IOException {
		pattern = ((pattern == null) || (pattern.length() == 0)) ? "." : pattern;
		pattern = ((pattern.charAt(0) != File.separatorChar) && (pattern.charAt(0) != '.')) ? "./" + pattern : pattern;
		int idx = pattern.lastIndexOf(File.separatorChar);
		String parent = (idx < 0) ? "." : pattern.substring(0, idx + 1);
		String target = (idx < 0) ? pattern : pattern.substring(idx + 1);

		File actualParent = ((parent.charAt(0) == File.separatorChar) ? new File(parent)
			: new File(cd(session), parent)).getCanonicalFile();

		idx = target.indexOf(File.separatorChar, idx);
		boolean isWildcarded = (target.indexOf('*', idx) >= 0);
		File[] files;
		if (isWildcarded) {
			if (!actualParent.exists()) {
				throw new IOException("File does not exist");
			}
			final List<String> pieces = parseSubstring(target);
			files = actualParent.listFiles((FileFilter) pathname -> compareSubstring(pieces, pathname.getName()));
		} else {
			File actualTarget = new File(actualParent, target).getCanonicalFile();
			if (!actualTarget.exists()) {
				throw new IOException("File does not exist");
			}
			if (actualTarget.isDirectory()) {
				files = actualTarget.listFiles();
			} else {
				files = new File[] {
					actualTarget
				};
			}
		}
		Arrays.sort(files, IO.fileComparator(File::getName));
		return files;
	}

	public static List<String> parseSubstring(String value) {
		List<String> pieces = new ArrayList<>();
		StringBuilder ss = new StringBuilder();
		// int kind = SIMPLE; // assume until proven otherwise
		boolean wasStar = false; // indicates last piece was a star
		boolean leftstar = false; // track if the initial piece is a star
		boolean rightstar = false; // track if the final piece is a star

		int idx = 0;

		// We assume (sub)strings can contain leading and trailing blanks
		boolean escaped = false;
		loop: for (;;) {
			if (idx >= value.length()) {
				if (wasStar) {
					// insert last piece as "" to handle trailing star
					rightstar = true;
				} else {
					pieces.add(ss.toString());
					// accumulate the last piece
					// note that in the case of
					// (cn=); this might be
					// the string "" (!=null)
				}
				ss.setLength(0);
				break loop;
			}

			// Read the next character and account for escapes.
			char c = value.charAt(idx++);
			if (!escaped && ((c == '(') || (c == ')'))) {
				throw new IllegalArgumentException("Illegal value: " + value);
			} else if (!escaped && (c == '*')) {
				if (wasStar) {
					// encountered two successive stars;
					// I assume this is illegal
					throw new IllegalArgumentException("Invalid filter string: " + value);
				}
				if (ss.length() > 0) {
					pieces.add(ss.toString()); // accumulate the pieces
					// between '*' occurrences
				}
				ss.setLength(0);
				// if this is a leading star, then track it
				if (pieces.isEmpty()) {
					leftstar = true;
				}
				wasStar = true;
			} else if (!escaped && (c == '\\')) {
				escaped = true;
			} else {
				escaped = false;
				wasStar = false;
				ss.append(c);
			}
		}
		if (leftstar || rightstar || pieces.size() > 1) {
			// insert leading and/or trailing "" to anchor ends
			if (rightstar) {
				pieces.add("");
			}
			if (leftstar) {
				pieces.add(0, "");
			}
		}
		return pieces;
	}

	public static boolean compareSubstring(List<String> pieces, String s) {
		// Walk the pieces to match the string
		// There are implicit stars between each piece,
		// and the first and last pieces might be "" to anchor the match.
		// assert (pieces.length > 1)
		// minimal case is <string>*<string>

		int len = pieces.size();

		int index = 0;

		for (int i = 0; i < len; i++) {
			String piece = pieces.get(i);

			// If this is the first piece, then make sure the
			// string starts with it.
			if (i == 0) {
				if (!s.startsWith(piece)) {
					return false;
				}
			}

			// If this is the last piece, then make sure the
			// string ends with it.
			if (i == len - 1) {
				return s.endsWith(piece);
			}

			// If this is neither the first or last piece, then
			// make sure the string contains it.
			if (i > 0) {
				index = s.indexOf(piece, index);
				if (index < 0) {
					return false;
				}
			}

			// Move string index beyond the matching piece.
			index += piece.length();
		}

		return true;
	}
}
