base.email.encoding.QuotedPrintableEncoding Maven / Gradle / Ivy

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/**
 * Creative commons Attribution-NonCommercial license.
 *
 * http://creativecommons.org/licenses/by-nc/2.5/au/deed.en_GB
 *
 * NO WARRANTY IS GIVEN OR IMPLIED, USE AT YOUR OWN RISK.
 */
package base.email.encoding;

import base.text.StringHelper;

public class QuotedPrintableEncoding extends Encoding{

	/**
	 * Break all lines greater than 80 characters long, Ensure
	 * all lines consistently end with CRLF, and ensure the full
	 * stop (period) character is escaped properly.
	 */
	public String encode(String message) {
		if(message == null || message == "") {
			return message;
		}

		int crlfCount = countSubstring(message, "\r\n");
		int crCount = countSubstring(message, "\r");
		int lfCount = countSubstring(message, "\n");
		String splitBy = "\n";

		if(crlfCount > crCount && crlfCount > lfCount) {
			splitBy = "\r\n";
		}
		if(crCount > crlfCount && crCount > lfCount) {
			splitBy = "\r";
		}
		if(lfCount > crCount && lfCount > crlfCount) {
			splitBy = "\n";
		}
		if(crlfCount == crCount && crlfCount == lfCount) {
			splitBy = "\r\n";
		}

		message = StringHelper.join(message.split(splitBy), "\r\n");

		int lineLength = 0;
		StringBuilder body = new StringBuilder();
		for(int i = 0; i < message.length(); i++) {
			char c = message.charAt(i);
			if(c == 13 || c == 10) {
				lineLength = 0;
			} else {
				lineLength++;
			}

			// Escape special or extended characters
			if((c > 127 && c < 256) || c < 10 || c == '=') {
				if(lineLength > 74) {
					body.append("=\r\n");
					lineLength = 0;
				}
				if(c > 15) {
					body.append("=" + Integer.toHexString(c).toUpperCase());
				} else {
					body.append("=0" + Integer.toHexString(c).toUpperCase());
				}
				lineLength += 2;

			// Escape full stop if it is at the start of the line
			} else if(c == '.' && lineLength == 1) {
				body.append(c);
				body.append(c);
				lineLength++;

			// Otherwise just append the next character
			} else {
				if(lineLength > 76) {
					body.append("=\r\n");
					lineLength = 1;
					if(c == '.') {
						body.append(c);
						lineLength++;
					}
				}
				body.append(c);
			}

		}

		if(!body.toString().endsWith("\r\n")) {
			body.append("\r\n");
		}

		return body.toString();
	}


}