Copyright (c) 2006, 2018 IBM Corporation and others.
This program and the accompanying materials
are made available under the terms of the Eclipse Public License 2.0
which accompanies this distribution, and is available at
https://www.eclipse.org/legal/epl-2.0/
SPDX-License-Identifier: EPL-2.0
Contributors:
    IBM Corporation - initial API and implementation
/*******************************************************************************
 * Copyright (c) 2006, 2018 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.compare.internal.core.patch;

import java.io.BufferedReader;
import java.io.IOException;
import java.text.ParseException;
import java.util.*;
import java.util.regex.Pattern;

import org.eclipse.compare.patch.IFilePatch2;
import org.eclipse.core.runtime.*;

import com.ibm.icu.text.DateFormat;
import com.ibm.icu.text.SimpleDateFormat;

public class PatchReader {
	private static final boolean DEBUG= false;

	private static final String DEV_NULL= "/dev/null"; //$NON-NLS-1$

	protected static final String MARKER_TYPE= "org.eclipse.compare.rejectedPatchMarker"; //$NON-NLS-1$

	// diff formats
	//	private static final int CONTEXT= 0;
	//	private static final int ED= 1;
	//	private static final int NORMAL= 2;
	//	private static final int UNIFIED= 3;

	// we recognize the following date/time formats
	private DateFormat[] fDateFormats= new DateFormat[] {
		new SimpleDateFormat("EEE MMM dd kk:mm:ss yyyy"), //$NON-NLS-1$
		new SimpleDateFormat("yyyy/MM/dd kk:mm:ss"), //$NON-NLS-1$
		new SimpleDateFormat("EEE MMM dd kk:mm:ss yyyy", Locale.US) //$NON-NLS-1$
	};

	private boolean fIsWorkspacePatch;
	private boolean fIsGitPatch;
	private DiffProject[] fDiffProjects;
	private FilePatch2[] fDiffs;

	// API for writing new multi-project patch format
	public static final String MULTIPROJECTPATCH_HEADER= "### Eclipse Workspace Patch"; //$NON-NLS-1$

	public static final String MULTIPROJECTPATCH_VERSION= "1.0"; //$NON-NLS-1$

	public static final String MULTIPROJECTPATCH_PROJECT= "#P"; //$NON-NLS-1$

	private static final Pattern GIT_PATCH_PATTERN= Pattern.compile("^diff --git a/.+ b/.+[\r\n]+$"); //$NON-NLS-1$

	
Create a patch reader for the default date formats.
/**
	 * Create a patch reader for the default date formats.
	 */
	public PatchReader() {
		// nothing here
	}

	
Create a patch reader for the given date formats.
Params:
dateFormats – 
           Array of DateFormats to be used when
           extracting dates from the patch./**
	 * Create a patch reader for the given date formats.
	 *
	 * @param dateFormats
	 *            Array of <code>DateFormat</code>s to be used when
	 *            extracting dates from the patch.
	 */
	public PatchReader(DateFormat[] dateFormats) {
		this();
		this.fDateFormats = dateFormats;
	}

	public void parse(BufferedReader reader) throws IOException {
		List<FilePatch2> diffs= new ArrayList<>();
		HashMap<String, DiffProject> diffProjects= new HashMap<>(4);
		String line= null;
		boolean reread= false;
		String diffArgs= null;
		String fileName= null;
		// no project means this is a single patch,create a placeholder project for now
		// which will be replaced by the target selected by the user in the preview pane
		String projectName= ""; //$NON-NLS-1$
		this.fIsWorkspacePatch= false;
		this.fIsGitPatch = false;

		LineReader lr= new LineReader(reader);
		lr.ignoreSingleCR(); // Don't treat single CRs as line feeds to be consistent with command line patch
		// Test for our format
		line= lr.readLine();
		if (line != null && line.startsWith(PatchReader.MULTIPROJECTPATCH_HEADER)) {
			this.fIsWorkspacePatch= true;
		} else {
			parse(lr, line);
			return;
		}

		// read leading garbage
		while (true) {
			if (!reread)
				line= lr.readLine();
			reread= false;
			if (line == null)
				break;
			if (line.length() < 4)
				continue; // too short

			if (line.startsWith(PatchReader.MULTIPROJECTPATCH_PROJECT)) {
				projectName= line.substring(2).trim();
				continue;
			}

			if (line.startsWith("Index: ")) { //$NON-NLS-1$
				fileName= line.substring(7).trim();
				continue;
			}
			if (line.startsWith("diff")) { //$NON-NLS-1$
				diffArgs= line.substring(4).trim();
				continue;
			}

			if (line.startsWith("--- ")) { //$NON-NLS-1$
				// if there is no current project or
				// the current project doesn't equal the newly parsed project
				// reset the current project to the newly parsed one, create a new DiffProject
				// and add it to the array
				DiffProject diffProject;
				if (!diffProjects.containsKey(projectName)) {
					diffProject= new DiffProject(projectName);
					diffProjects.put(projectName, diffProject);
				} else {
					diffProject= diffProjects.get(projectName);
				}

				line= readUnifiedDiff(diffs, lr, line, diffArgs, fileName, diffProject);
				diffArgs= fileName= null;
				reread= true;
			}
		}

		lr.close();

		this.fDiffProjects= diffProjects.values().toArray(new DiffProject[diffProjects.size()]);
		this.fDiffs = diffs.toArray(new FilePatch2[diffs.size()]);
	}

	protected FilePatch2 createFileDiff(IPath oldPath, long oldDate,
			IPath newPath, long newDate) {
		return new FilePatch2(oldPath, oldDate, newPath, newDate);
	}

	private String readUnifiedDiff(List<FilePatch2> diffs, LineReader lr, String line, String diffArgs, String fileName, DiffProject diffProject) throws IOException {
		List<FilePatch2> newDiffs= new ArrayList<>();
		String nextLine= readUnifiedDiff(newDiffs, lr, line, diffArgs, fileName);
		for (FilePatch2 diff : newDiffs) {
			diffProject.add(diff);
			diffs.add(diff);
		}
		return nextLine;
	}

	public void parse(LineReader lr, String line) throws IOException {
		List<FilePatch2> diffs= new ArrayList<>();
		boolean reread= false;
		String diffArgs= null;
		String fileName= null;
		List<String> headerLines = new ArrayList<>();
		boolean foundDiff= false;

		// read leading garbage
		reread= line!=null;
		while (true) {
			if (!reread)
				line= lr.readLine();
			reread= false;
			if (line == null)
				break;

			// remember some infos
			if (line.startsWith("Index: ")) { //$NON-NLS-1$
				fileName= line.substring(7).trim();
			} else if (line.startsWith("diff")) { //$NON-NLS-1$
				if (!foundDiff && GIT_PATCH_PATTERN.matcher(line).matches())
					this.fIsGitPatch= true;
				foundDiff= true;
				diffArgs= line.substring(4).trim();
			} else if (line.startsWith("--- ")) { //$NON-NLS-1$
				line= readUnifiedDiff(diffs, lr, line, diffArgs, fileName);
				if (!headerLines.isEmpty())
					setHeader(diffs.get(diffs.size() - 1), headerLines);
				diffArgs= fileName= null;
				reread= true;
			} else if (line.startsWith("*** ")) { //$NON-NLS-1$
				line= readContextDiff(diffs, lr, line, diffArgs, fileName);
				if (!headerLines.isEmpty())
					setHeader(diffs.get(diffs.size() - 1), headerLines);
				diffArgs= fileName= null;
				reread= true;
			}

			// Any lines we read here are header lines.
			// However, if reread is set, we will add them to the header on the next pass through
			if (!reread) {
				headerLines.add(line);
			}
		}

		lr.close();

		this.fDiffs = diffs.toArray(new FilePatch2[diffs.size()]);
	}

	private void setHeader(FilePatch2 diff, List<String> headerLines) {
		String header = LineReader.createString(false, headerLines);
		diff.setHeader(header);
		headerLines.clear();
	}

	/*
	 * Returns the next line that does not belong to this diff
	 */
	protected String readUnifiedDiff(List<FilePatch2> diffs, LineReader reader, String line, String args, String fileName) throws IOException {

		String[] oldArgs= split(line.substring(4));

		// read info about new file
		line= reader.readLine();
		if (line == null || !line.startsWith("+++ ")) //$NON-NLS-1$
			return line;

		String[] newArgs= split(line.substring(4));

		FilePatch2 diff = createFileDiff(extractPath(oldArgs, 0, fileName),
				extractDate(oldArgs, 1), extractPath(newArgs, 0, fileName),
				extractDate(newArgs, 1));
		diffs.add(diff);

		int[] oldRange= new int[2];
		int[] newRange= new int[2];
		int remainingOld= -1; // remaining old lines for current hunk
		int remainingNew= -1; // remaining new lines for current hunk
		List<String> lines= new ArrayList<>();

		boolean encounteredPlus = false;
		boolean encounteredMinus = false;
		boolean encounteredSpace = false;

		try {
			// read lines of hunk
			while (true) {

				line= reader.readLine();
				if (line == null)
					return null;

				if (reader.lineContentLength(line) == 0) {
					//System.out.println("Warning: found empty line in hunk; ignored");
					//lines.add(' ' + line);
					continue;
				}

				char c= line.charAt(0);
				if (remainingOld == 0 && remainingNew == 0 && c != '@' && c != '\\') {
					return line;
				}

				switch (c) {
					case '@':
						if (line.startsWith("@@ ")) { //$NON-NLS-1$
							// flush old hunk
							if (lines.size() > 0) {
								Hunk.createHunk(diff, oldRange, newRange, lines, encounteredPlus, encounteredMinus, encounteredSpace);
								lines.clear();
							}

							// format: @@ -oldStart,oldLength +newStart,newLength @@
							extractPair(line, '-', oldRange);
							extractPair(line, '+', newRange);
							remainingOld= oldRange[1];
							remainingNew= newRange[1];
							continue;
						}
						break;
					case ' ':
						encounteredSpace= true;
						remainingOld--;
						remainingNew--;
						lines.add(line);
						continue;
					case '+':
						encounteredPlus= true;
						remainingNew--;
						lines.add(line);
						continue;
					case '-':
						encounteredMinus= true;
						remainingOld--;
						lines.add(line);
						continue;
					case '\\':
						if (line.indexOf("newline at end") > 0) { //$NON-NLS-1$
							int lastIndex= lines.size();
							if (lastIndex > 0) {
								line= lines.get(lastIndex - 1);
								int end= line.length() - 1;
								char lc= line.charAt(end);
								if (lc == '\n') {
									end--;
									if (end > 0 && line.charAt(end) == '\r')
										end--;
								} else if (lc == '\r') {
									end--;
								}
								line= line.substring(0, end + 1);
								lines.set(lastIndex - 1, line);
							}
							continue;
						}
						break;
					case '#':
						break;
					case 'I':
						if (line.indexOf("Index:") == 0) //$NON-NLS-1$
							break;
						//$FALL-THROUGH$
					case 'd':
						if (line.indexOf("diff ") == 0) //$NON-NLS-1$
							break;
						//$FALL-THROUGH$
					case 'B':
						if (line.indexOf("Binary files differ") == 0) //$NON-NLS-1$
							break;
						//$FALL-THROUGH$
					default:
						break;
				}
				return line;
			}
		} finally {
			if (lines.size() > 0)
				Hunk.createHunk(diff, oldRange, newRange, lines, encounteredPlus, encounteredMinus, encounteredSpace);
		}
	}

	/*
	 * Returns the next line that does not belong to this diff
	 */
	private String readContextDiff(List<FilePatch2> diffs, LineReader reader, String line, String args, String fileName) throws IOException {

		String[] oldArgs= split(line.substring(4));

		// read info about new file
		line= reader.readLine();
		if (line == null || !line.startsWith("--- ")) //$NON-NLS-1$
			return line;

		String[] newArgs= split(line.substring(4));

		FilePatch2 diff = createFileDiff(extractPath(oldArgs, 0, fileName),
				extractDate(oldArgs, 1), extractPath(newArgs, 0, fileName),
				extractDate(newArgs, 1));
		diffs.add(diff);

		int[] oldRange= new int[2];
		int[] newRange= new int[2];
		List<String> oldLines= new ArrayList<>();
		List<String> newLines= new ArrayList<>();
		List<String> lines= oldLines;


		boolean encounteredPlus = false;
		boolean encounteredMinus = false;
		boolean encounteredSpace = false;

		try {
			// read lines of hunk
			while (true) {

				line= reader.readLine();
				if (line == null)
					return line;

				int l= line.length();
				if (l == 0)
					continue;
				if (l > 1) {
					switch (line.charAt(0)) {
					case '*':
						if (line.startsWith("***************")) {	// new hunk //$NON-NLS-1$
							// flush old hunk
							if (oldLines.size() > 0 || newLines.size() > 0) {
								Hunk.createHunk(diff, oldRange, newRange, unifyLines(oldLines, newLines), encounteredPlus, encounteredMinus, encounteredSpace);
								oldLines.clear();
								newLines.clear();
							}
							continue;
						}
						if (line.startsWith("*** ")) {	// old range //$NON-NLS-1$
							// format: *** oldStart,oldEnd ***
							extractPair(line, ' ', oldRange);
							if (oldRange[0] == 0) {
								oldRange[1] = 0; // In case of the file addition
							} else {
								oldRange[1] = oldRange[1] - oldRange[0] + 1;
							}
							lines= oldLines;
							continue;
						}
						break;
					case ' ':	// context line
						if (line.charAt(1) == ' ') {
							lines.add(line);
							continue;
						}
						break;
					case '+':	// addition
						if (line.charAt(1) == ' ') {
							encounteredPlus = true;
							lines.add(line);
							continue;
						}
						break;
					case '!':	// change
						if (line.charAt(1) == ' ') {
							encounteredSpace = true;
							lines.add(line);
							continue;
						}
						break;
					case '-':
						if (line.charAt(1) == ' ') {	// deletion
							encounteredMinus = true;
							lines.add(line);
							continue;
						}
						if (line.startsWith("--- ")) {	// new range //$NON-NLS-1$
							// format: *** newStart,newEnd ***
							extractPair(line, ' ', newRange);
							if (newRange[0] == 0) {
								newRange[1] = 0; // In case of the file removal
							} else {
								newRange[1] = newRange[1] - newRange[0] + 1;
							}
							lines= newLines;
							continue;
						}
						break;
					default:
						break;
					}
				}
				return line;
			}
		} finally {
			// flush last hunk
			if (oldLines.size() > 0 || newLines.size() > 0)
				Hunk.createHunk(diff, oldRange, newRange, unifyLines(oldLines, newLines), encounteredPlus, encounteredMinus, encounteredSpace);
		}
	}

	/*
	 * Creates a List of lines in the unified format from
	 * two Lists of lines in the 'classic' format.
	 */
	private List<String> unifyLines(List<String> oldLines, List<String> newLines) {
		List<String> result= new ArrayList<>();

		String[] ol= oldLines.toArray(new String[oldLines.size()]);
		String[] nl= newLines.toArray(new String[newLines.size()]);

		int oi= 0, ni= 0;

		while (true) {

			char oc= 0;
			String o= null;
			if (oi < ol.length) {
				o= ol[oi];
				oc= o.charAt(0);
			}

			char nc= 0;
			String n= null;
			if (ni < nl.length) {
				n= nl[ni];
				nc= n.charAt(0);
			}

			// EOF
			if (oc == 0 && nc == 0)
				break;

			// deletion in old
			if (oc == '-') {
				do {
					result.add('-' + o.substring(2));
					oi++;
					if (oi >= ol.length)
						break;
					o= ol[oi];
				} while (o.charAt(0) == '-');
				continue;
			}

			// addition in new
			if (nc == '+') {
				do {
					result.add('+' + n.substring(2));
					ni++;
					if (ni >= nl.length)
						break;
					n= nl[ni];
				} while (n.charAt(0) == '+');
				continue;
			}

			// differing lines on both sides
			if (oc == '!' && nc == '!') {
				// remove old
				do {
					result.add('-' + o.substring(2));
					oi++;
					if (oi >= ol.length)
						break;
					o= ol[oi];
				} while (o.charAt(0) == '!');

				// add new
				do {
					result.add('+' + n.substring(2));
					ni++;
					if (ni >= nl.length)
						break;
					n= nl[ni];
				} while (n.charAt(0) == '!');

				continue;
			}

			// context lines
			if (oc == ' ' && nc == ' ') {
				do {
					Assert.isTrue(o.equals(n), "non matching context lines"); //$NON-NLS-1$
					result.add(' ' + o.substring(2));
					oi++;
					ni++;
					if (oi >= ol.length || ni >= nl.length)
						break;
					o= ol[oi];
					n= nl[ni];
				} while (o.charAt(0) == ' ' && n.charAt(0) == ' ');
				continue;
			}

			if (oc == ' ') {
				do {
					result.add(' ' + o.substring(2));
					oi++;
					if (oi >= ol.length)
						break;
					o= ol[oi];
				} while (o.charAt(0) == ' ');
				continue;
			}

			if (nc == ' ') {
				do {
					result.add(' ' + n.substring(2));
					ni++;
					if (ni >= nl.length)
						break;
					n= nl[ni];
				} while (n.charAt(0) == ' ');
				continue;
			}

			Assert.isTrue(false, "unexpected char <" + oc + "> <" + nc + ">"); //$NON-NLS-1$ //$NON-NLS-2$ //$NON-NLS-3$
		}

		return result;
	}

	/*
	 * @return the parsed time/date in milliseconds or IFilePatch.DATE_UNKNOWN
	 * (0) on error
	 */
	private long extractDate(String[] args, int n) {
		if (n < args.length) {
			String line= args[n];
			for (DateFormat dateFormat : this.fDateFormats) {
				dateFormat.setLenient(true);
				try {
					Date date = dateFormat.parse(line);
					return date.getTime();
				} catch (ParseException ex) {
					// silently ignored
				}
			}
			// System.err.println("can't parse date: <" + line + ">");
		}
		return IFilePatch2.DATE_UNKNOWN;
	}

	/*
	 * Returns null if file name is "/dev/null".
	 */
	private IPath extractPath(String[] args, int n, String path2) {
		if (n < args.length) {
			String path= args[n];
			if (DEV_NULL.equals(path))
				return null;
			int pos= path.lastIndexOf(':');
			if (pos >= 0)
				path= path.substring(0, pos);
			if (path2 != null && !path2.equals(path)) {
				if (DEBUG) System.out.println("path mismatch: " + path2); //$NON-NLS-1$
				path= path2;
			}
			return new Path(path);
		}
		return null;
	}

	/*
	 * Tries to extract two integers separated by a comma.
	 * The parsing of the line starts at the position after
	 * the first occurrence of the given character start an ends
	 * at the first blank (or the end of the line).
	 * If only a single number is found this is assumed to be the start of a one line range.
	 * If an error occurs the range -1,-1 is returned.
	 */
	private void extractPair(String line, char start, int[] pair) {
		pair[0]= pair[1]= -1;
		int startPos= line.indexOf(start);
		if (startPos < 0) {
			if (DEBUG) System.out.println("parsing error in extractPair: couldn't find \'" + start + "\'"); //$NON-NLS-1$ //$NON-NLS-2$
			return;
		}
		line= line.substring(startPos+1);
		int endPos= line.indexOf(' ');
		if (endPos < 0) {
			if (DEBUG) System.out.println("parsing error in extractPair: couldn't find end blank"); //$NON-NLS-1$
			return;
		}
		line= line.substring(0, endPos);
		int comma= line.indexOf(',');
		if (comma >= 0) {
			pair[0]= Integer.parseInt(line.substring(0, comma));
			pair[1]= Integer.parseInt(line.substring(comma+1));
		} else {	// abbreviated form for one line patch
			pair[0]= Integer.parseInt(line);
			pair[1]= 1;
		}
	}

	/*
	 * Breaks the given string into tab separated substrings.
	 * Leading and trailing whitespace is removed from each token.
	 */
	private String[] split(String line) {
		List<String> l= new ArrayList<>();
		StringTokenizer st= new StringTokenizer(line, "\t"); //$NON-NLS-1$
		while (st.hasMoreElements()) {
			String token= st.nextToken().trim();
			if (token.length() > 0)
				l.add(token);
		}
		return l.toArray(new String[l.size()]);
	}

	public boolean isWorkspacePatch() {
		return this.fIsWorkspacePatch;
	}

	public boolean isGitPatch() {
		return this.fIsGitPatch;
	}

	public DiffProject[] getDiffProjects() {
		return this.fDiffProjects;
	}

	public FilePatch2[] getDiffs() {
		return this.fDiffs;
	}

	public FilePatch2[] getAdjustedDiffs() {
		if (!isWorkspacePatch() || this.fDiffs.length == 0)
			return this.fDiffs;
		List<FilePatch2> result = new ArrayList<>();
		for (FilePatch2 diff : this.fDiffs) {
			result.add(diff.asRelativeDiff());
		}
		return result.toArray(new FilePatch2[result.size()]);
	}

}