/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * 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.squareup.okhttp.internal.http;

final class HeaderParser {

  public interface CacheControlHandler {
    void handle(String directive, String parameter);
  }

  /** Parse a comma-separated list of cache control header values. */
  public static void parseCacheControl(String value, CacheControlHandler handler) {
    int pos = 0;
    while (pos < value.length()) {
      int tokenStart = pos;
      pos = skipUntil(value, pos, "=,");
      String directive = value.substring(tokenStart, pos).trim();

      if (pos == value.length() || value.charAt(pos) == ',') {
        pos++; // consume ',' (if necessary)
        handler.handle(directive, null);
        continue;
      }

      pos++; // consume '='
      pos = skipWhitespace(value, pos);

      String parameter;

      // quoted string
      if (pos < value.length() && value.charAt(pos) == '\"') {
        pos++; // consume '"' open quote
        int parameterStart = pos;
        pos = skipUntil(value, pos, "\"");
        parameter = value.substring(parameterStart, pos);
        pos++; // consume '"' close quote (if necessary)

        // unquoted string
      } else {
        int parameterStart = pos;
        pos = skipUntil(value, pos, ",");
        parameter = value.substring(parameterStart, pos).trim();
      }

      handler.handle(directive, parameter);
    }
  }

  /**
   * Returns the next index in {@code input} at or after {@code pos} that
   * contains a character from {@code characters}. Returns the input length if
   * none of the requested characters can be found.
   */
  public static int skipUntil(String input, int pos, String characters) {
    for (; pos < input.length(); pos++) {
      if (characters.indexOf(input.charAt(pos)) != -1) {
        break;
      }
    }
    return pos;
  }

  /**
   * Returns the next non-whitespace character in {@code input} that is white
   * space. Result is undefined if input contains newline characters.
   */
  public static int skipWhitespace(String input, int pos) {
    for (; pos < input.length(); pos++) {
      char c = input.charAt(pos);
      if (c != ' ' && c != '\t') {
        break;
      }
    }
    return pos;
  }

  /**
   * Returns {@code value} as a positive integer, or 0 if it is negative, or
   * -1 if it cannot be parsed.
   */
  public static int parseSeconds(String value) {
    try {
      long seconds = Long.parseLong(value);
      if (seconds > Integer.MAX_VALUE) {
        return Integer.MAX_VALUE;
      } else if (seconds < 0) {
        return 0;
      } else {
        return (int) seconds;
      }
    } catch (NumberFormatException e) {
      return -1;
    }
  }

  private HeaderParser() {
  }
}