/*
 * Copyright 2007 ZXing authors
 *
 * 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.zxing.client.result;

import com.google.zxing.Result;

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;

/**
 * <p>Abstract class representing the result of decoding a barcode, as more than
 * a String -- as some type of structured data. This might be a subclass which represents
 * a URL, or an e-mail address. {@link #parseResult(Result)} will turn a raw
 * decoded string into the most appropriate type of structured representation.</p>
 *
 * <p>Thanks to Jeff Griffin for proposing rewrite of these classes that relies less
 * on exception-based mechanisms during parsing.</p>
 *
 * @author Sean Owen
 */
public abstract class ResultParser {

  private static final ResultParser[] PARSERS = {
      new BookmarkDoCoMoResultParser(),
      new AddressBookDoCoMoResultParser(),
      new EmailDoCoMoResultParser(),
      new AddressBookAUResultParser(),
      new VCardResultParser(),
      new BizcardResultParser(),
      new VEventResultParser(),
      new EmailAddressResultParser(),
      new SMTPResultParser(),
      new TelResultParser(),
      new SMSMMSResultParser(),
      new SMSTOMMSTOResultParser(),
      new GeoResultParser(),
      new WifiResultParser(),
      new URLTOResultParser(),
      new URIResultParser(),
      new ISBNResultParser(),
      new ProductResultParser(),
      new ExpandedProductResultParser(),
      new VINResultParser(),
  };

  private static final Pattern DIGITS = Pattern.compile("\\d+");
  private static final Pattern AMPERSAND = Pattern.compile("&");
  private static final Pattern EQUALS = Pattern.compile("=");
  private static final String BYTE_ORDER_MARK = "\ufeff";

  static final String[] EMPTY_STR_ARRAY = new String[0];

  /**
   * Attempts to parse the raw {@link Result}'s contents as a particular type
   * of information (email, URL, etc.) and return a {@link ParsedResult} encapsulating
   * the result of parsing.
   *
   * @param theResult the raw {@link Result} to parse
   * @return {@link ParsedResult} encapsulating the parsing result
   */
  public abstract ParsedResult parse(Result theResult);

  protected static String getMassagedText(Result result) {
    String text = result.getText();
    if (text.startsWith(BYTE_ORDER_MARK)) {
      text = text.substring(1);
    }
    return text;
  }

  public static ParsedResult parseResult(Result theResult) {
    for (ResultParser parser : PARSERS) {
      ParsedResult result = parser.parse(theResult);
      if (result != null) {
        return result;
      }
    }
    return new TextParsedResult(theResult.getText(), null);
  }

  protected static void maybeAppend(String value, StringBuilder result) {
    if (value != null) {
      result.append('\n');
      result.append(value);
    }
  }

  protected static void maybeAppend(String[] value, StringBuilder result) {
    if (value != null) {
      for (String s : value) {
        result.append('\n');
        result.append(s);
      }
    }
  }

  protected static String[] maybeWrap(String value) {
    return value == null ? null : new String[] { value };
  }

  protected static String unescapeBackslash(String escaped) {
    int backslash = escaped.indexOf('\\');
    if (backslash < 0) {
      return escaped;
    }
    int max = escaped.length();
    StringBuilder unescaped = new StringBuilder(max - 1);
    unescaped.append(escaped.toCharArray(), 0, backslash);
    boolean nextIsEscaped = false;
    for (int i = backslash; i < max; i++) {
      char c = escaped.charAt(i);
      if (nextIsEscaped || c != '\\') {
        unescaped.append(c);
        nextIsEscaped = false;
      } else {
        nextIsEscaped = true;
      }
    }
    return unescaped.toString();
  }

  protected static int parseHexDigit(char c) {
    if (c >= '0' && c <= '9') {
      return c - '0';
    }
    if (c >= 'a' && c <= 'f') {
      return 10 + (c - 'a');
    }
    if (c >= 'A' && c <= 'F') {
      return 10 + (c - 'A');
    }
    return -1;
  }

  protected static boolean isStringOfDigits(CharSequence value, int length) {
    return value != null && length > 0 && length == value.length() && DIGITS.matcher(value).matches();
  }

  protected static boolean isSubstringOfDigits(CharSequence value, int offset, int length) {
    if (value == null || length <= 0) {
      return false;
    }
    int max = offset + length;
    return value.length() >= max && DIGITS.matcher(value.subSequence(offset, max)).matches();
  }

  static Map<String,String> parseNameValuePairs(String uri) {
    int paramStart = uri.indexOf('?');
    if (paramStart < 0) {
      return null;
    }
    Map<String,String> result = new HashMap<>(3);
    for (String keyValue : AMPERSAND.split(uri.substring(paramStart + 1))) {
      appendKeyValue(keyValue, result);
    }
    return result;
  }

  private static void appendKeyValue(CharSequence keyValue, Map<String,String> result) {
    String[] keyValueTokens = EQUALS.split(keyValue, 2);
    if (keyValueTokens.length == 2) {
      String key = keyValueTokens[0];
      String value = keyValueTokens[1];
      try {
        value = urlDecode(value);
        result.put(key, value);
      } catch (IllegalArgumentException iae) {
        // continue; invalid data such as an escape like %0t
      }
    }
  }

  static String urlDecode(String encoded) {
    try {
      return URLDecoder.decode(encoded, "UTF-8");
    } catch (UnsupportedEncodingException uee) {
      throw new IllegalStateException(uee); // can't happen
    }
  }

  static String[] matchPrefixedField(String prefix, String rawText, char endChar, boolean trim) {
    List<String> matches = null;
    int i = 0;
    int max = rawText.length();
    while (i < max) {
      i = rawText.indexOf(prefix, i);
      if (i < 0) {
        break;
      }
      i += prefix.length(); // Skip past this prefix we found to start
      int start = i; // Found the start of a match here
      boolean more = true;
      while (more) {
        i = rawText.indexOf(endChar, i);
        if (i < 0) {
          // No terminating end character? uh, done. Set i such that loop terminates and break
          i = rawText.length();
          more = false;
        } else if (countPrecedingBackslashes(rawText, i) % 2 != 0) {
          // semicolon was escaped (odd count of preceding backslashes) so continue
          i++;
        } else {
          // found a match
          if (matches == null) {
            matches = new ArrayList<>(3); // lazy init
          }
          String element = unescapeBackslash(rawText.substring(start, i));
          if (trim) {
            element = element.trim();
          }
          if (!element.isEmpty()) {
            matches.add(element);
          }
          i++;
          more = false;
        }
      }
    }
    if (matches == null || matches.isEmpty()) {
      return null;
    }
    return matches.toArray(EMPTY_STR_ARRAY);
  }

  private static int countPrecedingBackslashes(CharSequence s, int pos) {
    int count = 0;
    for (int i = pos - 1; i >= 0; i--) {
      if (s.charAt(i) == '\\') {
        count++;
      } else {
        break;
      }
    }
    return count;
  }

  static String matchSinglePrefixedField(String prefix, String rawText, char endChar, boolean trim) {
    String[] matches = matchPrefixedField(prefix, rawText, endChar, trim);
    return matches == null ? null : matches[0];
  }

}
