Rewrite `FlowedMessageUtils.deflow()` (ef8d9abe) · Commits · e / os / Mail

mail/common/src/main/java/com/fsck/k9/mail/internet/FlowedMessageUtils.kt

+62 −99

Original line number	Diff line number	Diff line
		package com.fsck.k9.mail.internet;

		package com.fsck.k9.mail.internet

		/**
		* Adapted from the Apache James project, see
		* https://james.apache.org/mailet/base/apidocs/org/apache/mailet/base/FlowedMessageUtils.html
		*
		* <p>Manages texts encoded as <code>text/plain; format=flowed</code>.</p>
		* <p>As a reference see:</p>
		* <ul>
		* <li><a href='http://www.rfc-editor.org/rfc/rfc2646.txt'>RFC2646</a></li>
		* <li><a href='http://www.rfc-editor.org/rfc/rfc3676.txt'>RFC3676</a> (new method with DelSP support).
		* </ul>
		* <h4>Note</h4>
		* <ul>
		* <li>In order to decode, the input text must belong to a mail with headers similar to:
		* Content-Type: text/plain; charset="CHARSET"; [delsp="yes\|no"; ]format="flowed"
		* (the quotes around CHARSET are not mandatory).
		* Furthermore the header Content-Transfer-Encoding MUST NOT BE Quoted-Printable
		* (see RFC3676 paragraph 4.2).(In fact this happens often for non 7bit messages).
		* </li>
		* </ul>
		* Decodes text encoded as `text/plain; format=flowed` (RFC 3676).
		*/
		public final class FlowedMessageUtils {
		private static final char RFC2646_SPACE = ' ';
		private static final char RFC2646_QUOTE = '>';
		private static final String RFC2646_SIGNATURE = "-- ";
		private static final String RFC2646_CRLF = "\r\n";

		private FlowedMessageUtils() {
		// this class cannot be instantiated
		}
		object FlowedMessageUtils {
		private const val QUOTE = '>'
		private const val SPACE = ' '
		private const val CR = '\r'
		private const val LF = '\n'
		private const val SIGNATURE = "-- "
		private const val CRLF = "\r\n"

		/**
		* Decodes a text previously wrapped using "format=flowed".
		*/
		public static String deflow(String text, boolean delSp) {
		String[] lines = text.split("\r\n\|\n", -1);
		StringBuffer result = null;
		StringBuffer resultLine = new StringBuffer();
		int resultLineQuoteDepth = 0;
		boolean resultLineFlowed = false;
		// One more cycle, to close the last line
		for (int i = 0; i <= lines.length; i++) {
		String line = i < lines.length ? lines[i] : null;
		int actualQuoteDepth = 0;
		@JvmStatic
		fun deflow(text: String, delSp: Boolean): String {
		var lineStartIndex = 0
		var lastLineQuoteDepth = 0
		var lastLineFlowed = false

		if (line != null) {
		if (line.equals(RFC2646_SIGNATURE)) {
		// signature handling (the previous line is not flowed)
		resultLineFlowed = false;
		} else if (line.length() > 0 && line.charAt(0) == RFC2646_QUOTE) {
		// Quote
		actualQuoteDepth = 1;
		while (actualQuoteDepth < line.length() && line.charAt(actualQuoteDepth) == RFC2646_QUOTE) {
		actualQuoteDepth++;
		}
		// if quote-depth changes wrt the previous line then this is not flowed
		if (resultLineQuoteDepth != actualQuoteDepth) {
		resultLineFlowed = false;
		return buildString {
		while (lineStartIndex <= text.lastIndex) {
		var quoteDepth = 0
		while (lineStartIndex <= text.lastIndex && text[lineStartIndex] == QUOTE) {
		quoteDepth++
		lineStartIndex++
		}
		line = line.substring(actualQuoteDepth);

		} else {
		// if quote-depth changes wrt the first line then this is not flowed
		if (resultLineQuoteDepth > 0) {
		resultLineFlowed = false;
		}
		// Remove space stuffing
		if (lineStartIndex <= text.lastIndex && text[lineStartIndex] == SPACE) {
		lineStartIndex++
		}

		if (line.length() > 0 && line.charAt(0) == RFC2646_SPACE) {
		// Line space-stuffed
		line = line.substring(1);
		// We support both LF and CRLF line endings. To cover both cases we search for LF.
		val lineFeedIndex = text.indexOf(LF, lineStartIndex)
		val lineBreakFound = lineFeedIndex != -1

		var lineEndIndex = if (lineBreakFound) lineFeedIndex else text.length
		if (lineEndIndex > 0 && text[lineEndIndex - 1] == CR) {
		lineEndIndex--
		}

		// if the previous was the last then it was not flowed
		} else {
		resultLineFlowed = false;
		if (lastLineFlowed && quoteDepth != lastLineQuoteDepth) {
		append(CRLF)
		lastLineFlowed = false
		}

		// Add the PREVIOUS line.
		// This often will find the flow looking for a space as the last char of the line.
		// With quote changes or signatures it could be the following line to void the flow.
		if (!resultLineFlowed && i > 0) {
		if (resultLineQuoteDepth > 0) {
		resultLine.insert(0, RFC2646_SPACE);
		val lineIsSignatureMarker = lineEndIndex - lineStartIndex == SIGNATURE.length &&
		text.regionMatches(lineStartIndex, SIGNATURE, 0, SIGNATURE.length)

		var lineFlowed = false
		if (lineIsSignatureMarker) {
		if (lastLineFlowed) {
		append(CRLF)
		lastLineFlowed = false
		}
		} else if (lineEndIndex > lineStartIndex && text[lineEndIndex - 1] == SPACE) {
		lineFlowed = true
		if (delSp) {
		lineEndIndex--
		}
		for (int j = 0; j < resultLineQuoteDepth; j++) {
		resultLine.insert(0, RFC2646_QUOTE);
		}
		if (result == null) {
		result = new StringBuffer();
		} else {
		result.append(RFC2646_CRLF);

		if (!lastLineFlowed && quoteDepth > 0) {
		// This is not a continuation line, so prefix the text with quote characters.
		repeat(quoteDepth) {
		append(QUOTE)
		}
		result.append(resultLine.toString());
		resultLine = new StringBuffer();
		resultLineFlowed = false;
		append(SPACE)
		}
		resultLineQuoteDepth = actualQuoteDepth;

		if (line != null) {
		if (!line.equals(RFC2646_SIGNATURE) && line.endsWith("" + RFC2646_SPACE) && i < lines.length - 1) {
		// Line flowed (NOTE: for the split operation the line having i == lines.length is the last that
		// does not end with RFC2646_CRLF)
		if (delSp) {
		line = line.substring(0, line.length() - 1);
		}
		resultLineFlowed = true;
		} else {
		resultLineFlowed = false;
		append(text, lineStartIndex, lineEndIndex)

		if (!lineFlowed && lineBreakFound) {
		append(CRLF)
		}

		resultLine.append(line);
		lineStartIndex = if (lineBreakFound) lineFeedIndex + 1 else text.length
		lastLineQuoteDepth = quoteDepth
		lastLineFlowed = lineFlowed
		}
		}

		return result.toString();
		}
		}

mail/common/src/test/java/com/fsck/k9/mail/internet/FlowedMessageUtilsTest.kt

+31 −17

Original line number	Diff line number	Diff line
		@@ -4,16 +4,13 @@ import com.fsck.k9.mail.crlf
		import com.google.common.truth.Truth.assertThat
		import org.junit.Test

		private const val DEL_SP_NO = false
		private const val DEL_SP_YES = true

		class FlowedMessageUtilsTest {
		@Test
		fun `deflow() with simple text`() {
		val input = "Text that should be \r\n" +
		"displayed on one line"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo("Text that should be displayed on one line")
		}
		@@ -27,7 +24,7 @@ class FlowedMessageUtilsTest {
		"Text that should retain\r\n" +
		"its line break."

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo(
		"""
		@@ -42,7 +39,7 @@ class FlowedMessageUtilsTest {
		fun `deflow() with nothing to do`() {
		val input = "Line one\r\nLine two\r\n"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo(input)
		}
		@@ -56,7 +53,7 @@ class FlowedMessageUtilsTest {
		"Some more text that should be \r\n" +
		"displayed on one line.\r\n"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo(
		"""
		@@ -74,7 +71,7 @@ class FlowedMessageUtilsTest {
		val input = "> Quoted text \r\n" +
		"Some other text"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo("> Quoted text \r\nSome other text")
		}
		@@ -86,7 +83,7 @@ class FlowedMessageUtilsTest {
		"> is here\r\n" +
		"Some other text"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo(
		"""
		@@ -103,7 +100,7 @@ class FlowedMessageUtilsTest {
		"\r\n" +
		"Text"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo(input)
		}
		@@ -112,7 +109,7 @@ class FlowedMessageUtilsTest {
		fun `deflow() with delSp=true`() {
		val input = "Text that is wrapped mid wo \r\nrd"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_YES)
		val result = FlowedMessageUtils.deflow(input, delSp = true)

		assertThat(result).isEqualTo("Text that is wrapped mid word")
		}
		@@ -122,7 +119,7 @@ class FlowedMessageUtilsTest {
		val input = "> Quoted te \r\n" +
		"> xt"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_YES)
		val result = FlowedMessageUtils.deflow(input, delSp = true)

		assertThat(result).isEqualTo("> Quoted text")
		}
		@@ -132,7 +129,7 @@ class FlowedMessageUtilsTest {
		val input = "Text that should be \r\n" +
		" displayed on one line"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo("Text that should be displayed on one line")
		}
		@@ -143,7 +140,7 @@ class FlowedMessageUtilsTest {
		" Line 2\r\n" +
		" Line 3\r\n"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo("Line 1\r\nLine 2\r\nLine 3\r\n")
		}
		@@ -153,7 +150,7 @@ class FlowedMessageUtilsTest {
		val input = "> Text that should be \r\n" +
		"> displayed on one line"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo("> Text that should be displayed on one line")
		}
		@@ -167,7 +164,7 @@ class FlowedMessageUtilsTest {
		"Signature \r\n" +
		"text"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo(
		"""
		@@ -188,7 +185,7 @@ class FlowedMessageUtilsTest {
		"> Signature \r\n" +
		"> text"

		val result = FlowedMessageUtils.deflow(input, DEL_SP_NO)
		val result = FlowedMessageUtils.deflow(input, delSp = false)

		assertThat(result).isEqualTo(
		"""
		@@ -199,4 +196,21 @@ class FlowedMessageUtilsTest {
		""".trimIndent().crlf()
		)
		}

		@Test
		fun `deflow() with flowed line followed by signature separator`() {
		val input = "Fake flowed line \r\n" +
		"-- \r\n" +
		"Signature"

		val result = FlowedMessageUtils.deflow(input, delSp = true)

		assertThat(result).isEqualTo(
		"""
		Fake flowed line
		--${" "}
		Signature
		""".trimIndent().crlf()
		)
		}
		}