Add AddressHeaderBuilder to correctly fold recipient headers

ippschi · Feb 14, 2019 · 58d72e0 · 58d72e0
1 parent 272a03e
commit 58d72e0
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diff --git a/mail/common/src/main/java/com/fsck/k9/mail/internet/AddressHeaderBuilder.kt b/mail/common/src/main/java/com/fsck/k9/mail/internet/AddressHeaderBuilder.kt
@@ -0,0 +1,35 @@
+package com.fsck.k9.mail.internet
+
+import com.fsck.k9.mail.Address
+
+/**
+ * Encode and fold email addresses for use in header values.
+ */
+object AddressHeaderBuilder {
+    @JvmStatic
+    fun createHeaderValue(addresses: Array<Address>): String {
+        require(addresses.isNotEmpty()) { "addresses must not be empty" }
+
+        return buildString {
+            var lineLength = 0
+            for ((index, address) in addresses.withIndex()) {
+                val encodedAddress = address.toEncodedString()
+                val encodedAddressLength = encodedAddress.length
+
+                if (index > 0 && lineLength + 2 + encodedAddressLength + 1 > RECOMMENDED_MAX_LINE_LENGTH) {
+                    append(",$CRLF ")
+                    append(encodedAddress)
+                    lineLength = encodedAddressLength + 1
+                } else {
+                    if (index > 0) {
+                        append(", ")
+                        lineLength += 2
+                    }
+
+                    append(encodedAddress)
+                    lineLength += encodedAddressLength
+                }
+            }
+        }
+    }
+}
diff --git a/mail/common/src/main/java/com/fsck/k9/mail/internet/MimeExtensions.kt b/mail/common/src/main/java/com/fsck/k9/mail/internet/MimeExtensions.kt
@@ -1,6 +1,9 @@
 package com.fsck.k9.mail.internet
 
 
+// RFC 5322, section 2.1.1
+internal const val RECOMMENDED_MAX_LINE_LENGTH = 78
+
 // RFC 2045: tspecials :=  "(" / ")" / "<" / ">" / "@" / "," / ";" / ":" / "\" / <"> / "/" / "[" / "]" / "?" / "="
 private val TSPECIALS = charArrayOf('(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=')
 

diff --git a/mail/common/src/test/java/com/fsck/k9/mail/internet/AddressHeaderBuilderTest.kt b/mail/common/src/test/java/com/fsck/k9/mail/internet/AddressHeaderBuilderTest.kt
@@ -0,0 +1,60 @@
+package com.fsck.k9.mail.internet
+
+import com.fsck.k9.mail.Address
+import com.fsck.k9.mail.K9LibRobolectricTestRunner
+import com.fsck.k9.mail.crlf
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Test
+import org.junit.runner.RunWith
+
+
+@RunWith(K9LibRobolectricTestRunner::class)
+class AddressHeaderBuilderTest {
+
+    @Test
+    fun createHeaderValue_withSingleAddress() {
+        val addresses = arrayOf(Address("test@domain.example"))
+
+        val headerValue = AddressHeaderBuilder.createHeaderValue(addresses)
+
+        assertEquals("test@domain.example", headerValue)
+    }
+
+    @Test
+    fun createHeaderValue_withTwoAddressesThatFitOnSingleLine() {
+        val addresses = arrayOf(
+                Address("one@domain.example"),
+                Address("two@domain.example")
+        )
+
+        val headerValue = AddressHeaderBuilder.createHeaderValue(addresses)
+
+        assertEquals("one@domain.example, two@domain.example", headerValue)
+    }
+
+    @Test
+    fun createHeaderValue_withMultipleAddressesThatNeedWrapping() {
+        val addresses = arrayOf(
+                Address("one@domain.example", "Person One"),
+                Address("two+because.i.can@this.is.quite.some.domain.example", "Person \"Long Email Address\" Two"),
+                Address("three@domain.example", "Person Three"),
+                Address("four@domain.example", "Person Four"),
+                Address("five@domain.example", "Person Five")
+        )
+
+        val headerValue = AddressHeaderBuilder.createHeaderValue(addresses)
+
+        assertEquals("""
+            |Person One <one@domain.example>,
+            | "Person \"Long Email Address\" Two" <two+because.i.can@this.is.quite.some.domain.example>,
+            | Person Three <three@domain.example>, Person Four <four@domain.example>,
+            | Person Five <five@domain.example>
+        """.trimMargin().crlf(), headerValue)
+    }
+
+    @Test(expected = IllegalArgumentException::class)
+    fun createHeaderValue_withoutAddresses_shouldThrow() {
+        AddressHeaderBuilder.createHeaderValue(emptyArray())
+    }
+}