/*
 * Copyright 2010 Google Inc.
 *
 * Licensed 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 com.google.gwt.logging.server;

import com.google.gwt.thirdparty.debugging.sourcemap.SourceMapConsumerFactory;
import com.google.gwt.thirdparty.debugging.sourcemap.SourceMapping;
import com.google.gwt.thirdparty.debugging.sourcemap.proto.Mapping;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.logging.LogRecord;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

/**
 * Deobfuscates stack traces on the server side. This class requires that you have turned on
 * emulated stack traces, via <code>&lt;set-property name="compiler.stackMode" value="emulated"
 * /&gt;</code> in your <code>.gwt.xml</code> module file for non-Chrome browsers or
 * <code>&lt;set-property name="compiler.useSourceMaps" value="true"/&gt;</code> for Chrome, and
 * moved your symbol map files to a location accessible by your server sever side code. You can use
 * the GWT compiler <code>-deploy</code> command line argument to specify the location of the folder
 * into which the generated <code>symbolMaps</code> directory is written. By default, the final
 * <code>symbolMaps</code> directory is <code>war/WEB-INF/deploy/<i>yourmodulename</i>/symbolMaps/</code>.
 * Pass the resulting directory location into this class' {@link StackTraceDeobfuscator#symbolMapsDirectory}
 * constructor or {@link #setSymbolMapsDirectory(String)} setter method.
 *
 * TODO(unnurg): Combine this code with similar code in JUnitHostImpl
 */
public class StackTraceDeobfuscator {

  private static class SymbolMap extends HashMap<String, String> {
  }

  // From JsniRef class, which is in gwt-dev and so can't be accessed here
  // TODO(unnurg) once there is a place for shared code, move this to there.
  private static Pattern JsniRefPattern =
      Pattern.compile("@?([^:]+)::([^(]+)(\\((.*)\\))?");

  // The javadoc for StackTraceElement.getLineNumber() says it returns -1 when
  // the line number is unavailable
  private static final int LINE_NUMBER_UNKNOWN = -1;

  Pattern fragmentIdPattern = Pattern.compile(".*(\\d+)\\.js");

  protected File symbolMapsDirectory;

  // Map of strongName + fragmentId to sourceMap
  private Map<String, SourceMapping> sourceMaps =
      new HashMap<String, SourceMapping>();

  private Map<String, SymbolMap> symbolMaps =
      new HashMap<String, SymbolMap>();

  /**
   * Constructor, which takes a <code>symbolMaps</code> directory as its argument. Symbol maps are
   * generated into the location specified by the GWT compiler <code>-deploy</code> command line
   * argument.
   *
   * @param symbolMapsDirectory the <code>symbolMaps</code> directory with, or without trailing
   *                            directory separator character
   */
  public StackTraceDeobfuscator(String symbolMapsDirectory) {
    setSymbolMapsDirectory(symbolMapsDirectory);
  }

  /**
   * Best effort resymbolization of a log record's stack trace.
   *
   * @param lr         the log record to resymbolize
   * @param strongName the GWT permutation strong name
   * @return the best effort resymbolized log record
   */
  public LogRecord deobfuscateLogRecord(LogRecord lr, String strongName) {
    if (lr.getThrown() != null && strongName != null) {
      lr.setThrown(deobfuscateThrowable(lr.getThrown(), strongName));
    }
    return lr;
  }

  /**
   * Convenience method which resymbolizes an entire stack trace to extent possible.
   *
   * @param st         the stack trace to resymbolize
   * @param strongName the GWT permutation strong name
   * @return a best effort resymbolized stack trace
   */
  public StackTraceElement[] deobfuscateStackTrace(
      StackTraceElement[] st, String strongName) {
    StackTraceElement[] newSt = new StackTraceElement[st.length];
    for (int i = 0; i < st.length; i++) {
      newSt[i] = resymbolize(st[i], strongName);
    }
    return newSt;
  }

  /**
   * Best effort resymbolization of a a single stack trace element.
   *
   * @param ste        the stack trace element to resymbolize
   * @param strongName the GWT permutation strong name
   * @return the best effort resymbolized stack trace element
   */
  public StackTraceElement resymbolize(StackTraceElement ste,
      String strongName) {
    String declaringClass = null;
    String methodName = null;
    String filename = null;
    int lineNumber = -1;
    int fragmentId = -1;

    String steFilename = ste.getFileName();
    SymbolMap map = loadSymbolMap(strongName);
    String symbolData = map == null ? null : map.get(ste.getMethodName());

    boolean sourceMapCapable = false;

    int column = 1;
    // column information is encoded in filename after '@' for sourceMap capable browsers
    if (steFilename != null) {
      int columnMarkerIndex = steFilename.indexOf("@");
      if (columnMarkerIndex != -1) {
        try {
          column = Integer.parseInt(steFilename.substring(columnMarkerIndex + 1));
          sourceMapCapable = true;
        } catch (NumberFormatException nfe) {
        }
        steFilename = steFilename.substring(0, columnMarkerIndex);
      }
    }

    // first use symbolMap, then refine via sourceMap if possible
    if (symbolData != null) {
      // jsniIdent, className, memberName, sourceUri, sourceLine, fragmentId
      String[] parts = symbolData.split(",");
      if (parts.length == 6) {
        String[] ref = parse(
            parts[0].substring(0, parts[0].lastIndexOf(')') + 1));

        if (ref != null) {
          declaringClass = ref[0];
          methodName = ref[1];
        } else {
          declaringClass = ste.getClassName();
          methodName = ste.getMethodName();
        }

        // parts[3] contains the source file URI or "Unknown"
        filename = "Unknown".equals(parts[3]) ? null
            : parts[3].substring(parts[3].lastIndexOf('/') + 1);

        lineNumber = ste.getLineNumber();

        /*
         * When lineNumber is LINE_NUMBER_UNKNOWN, either because
         * compiler.stackMode is not emulated or
         * compiler.emulatedStack.recordLineNumbers is false, use the method
         * declaration line number from the symbol map.
         */
        if (lineNumber == LINE_NUMBER_UNKNOWN || (sourceMapCapable && column == -1)) {
          // Safari will send line numbers, with col == -1, we need to use symbolMap in this case
          lineNumber = Integer.parseInt(parts[4]);
        }

        fragmentId = Integer.parseInt(parts[5]);
      }
    }

    // anonymous function, try to use <fragmentNum>.js:line to determine fragment id
    if (fragmentId == -1 && steFilename != null) {
      // fragment identifier encoded in filename
      Matcher matcher = fragmentIdPattern.matcher(steFilename);
      if (matcher.matches()) {
        String fragment = matcher.group(1);
        try {
          fragmentId = Integer.parseInt(fragment);
        } catch (Exception e) {
        }
      } else if (steFilename.contains(strongName)) {
        // else it's <strongName>.cache.js which is the 0th fragment
        fragmentId = 0;
      }
    }


    int jsLineNumber = ste.getLineNumber();

    // try to refine location via sourcemap
    if (sourceMapCapable && fragmentId != -1 && column != -1) {
      SourceMapping sourceMapping = loadSourceMap(strongName, fragmentId);
      if (sourceMapping != null && ste.getLineNumber() > -1) {
        Mapping.OriginalMapping mappingForLine = sourceMapping
            .getMappingForLine(jsLineNumber, column);
        if (mappingForLine != null) {

          if (declaringClass == null || declaringClass.equals(ste.getClassName())) {
            declaringClass = mappingForLine.getOriginalFile();
            methodName = mappingForLine.getIdentifier();
          }
          filename = mappingForLine.getOriginalFile();
          lineNumber = mappingForLine.getLineNumber();
        }
      }
    }

    if (declaringClass != null) {
      return new StackTraceElement(declaringClass, methodName, filename, lineNumber);
    }

    // If anything goes wrong, just return the unobfuscated element
    return ste;
  }

  public void setSymbolMapsDirectory(String symbolMapsDirectory) {
    // permutations are unique, no need to clear the symbolMaps hash map
    this.symbolMapsDirectory = new File(symbolMapsDirectory);
  }

  protected InputStream getSourceMapInputStream(String permutationStrongName, int fragmentNumber)
      throws IOException {
    String filename = symbolMapsDirectory.getCanonicalPath()
        + File.separatorChar + permutationStrongName + "_sourceMap" + fragmentNumber + ".json";
    return new FileInputStream(filename);
  }

  /**
   * Retrieves a new {@link InputStream} for the given permutation strong name. This implementation,
   * which subclasses may override, returns a {@link InputStream} for the <code>
   * <i>permutation-strong-name</i>.symbolMap</code> file in the <code>symbolMaps</code> directory.
   *
   * @param permutationStrongName the GWT permutation strong name
   * @return a new {@link InputStream}
   */
  protected InputStream getSymbolMapInputStream(String permutationStrongName)
      throws IOException {
    String filename = symbolMapsDirectory.getCanonicalPath()
        + File.separatorChar + permutationStrongName + ".symbolMap";
    return new FileInputStream(filename);
  }

  private Throwable deobfuscateThrowable(Throwable old, String strongName) {
    Throwable t = new Throwable(old.getMessage());
    if (old.getStackTrace() != null) {
      t.setStackTrace(deobfuscateStackTrace(old.getStackTrace(), strongName));
    } else {
      t.setStackTrace(new StackTraceElement[0]);
    }
    if (old.getCause() != null) {
      t.initCause(deobfuscateThrowable(old.getCause(), strongName));
    }
    return t;
  }

  private SourceMapping loadSourceMap(String permutationStrongName, int fragmentId) {
    SourceMapping toReturn = sourceMaps.get(permutationStrongName + fragmentId);
    if (toReturn == null) {
      try {
        String sourceMapString = loadStreamAsString(
            getSourceMapInputStream(permutationStrongName, fragmentId));
        toReturn = SourceMapConsumerFactory.parse(sourceMapString);
        sourceMaps.put(permutationStrongName + fragmentId, toReturn);
      } catch (Exception e) {
      }
    }
    return toReturn;
  }

  private String loadStreamAsString(InputStream stream) {
    return new Scanner(stream).useDelimiter("\\A").next();
  }

  private SymbolMap loadSymbolMap(
      String strongName) {
    SymbolMap toReturn = symbolMaps.get(strongName);
    if (toReturn != null) {
      return toReturn;
    }
    toReturn = new SymbolMap();
    String line;

    try {
      BufferedReader bin = new BufferedReader(
          new InputStreamReader(getSymbolMapInputStream(strongName)));
      try {
        while ((line = bin.readLine()) != null) {
          if (line.charAt(0) == '#') {
            continue;
          }
          int idx = line.indexOf(',');
          toReturn.put(new String(line.substring(0, idx)),
              line.substring(idx + 1));
        }
      } finally {
        bin.close();
      }
    } catch (IOException e) {
      //  use empty symbol map to avoid repeated lookups
      toReturn = new SymbolMap();
    }

    symbolMaps.put(strongName, toReturn);
    return toReturn;
  }

  /**
   * Extracts the declaring class and method name from a JSNI ref, or null if the information cannot
   * be extracted.
   *
   * @param refString symbol map reference string
   * @return a string array contains the declaring class and method name, or null when the regex
   *         match fails
   * @see com.google.gwt.dev.util.JsniRef
   */
  private String[] parse(String refString) {
    Matcher matcher = JsniRefPattern.matcher(refString);
    if (!matcher.matches()) {
      return null;
    }
    String className = matcher.group(1);
    String memberName = matcher.group(2);
    String[] toReturn = new String[]{className, memberName};
    return toReturn;
  }
}