Use ktor's HttpHeaders everywhere, and add warning about ktor-okhttp in README

README.md

@@ -18,6 +18,18 @@ For questions, suggestions etc. use [Github discussions](https://github.com/bitf
 We're happy about contributions, but please let us know in the discussions before. Then make the changes
 in your own repository and send a pull request.
 
+> [!NOTE]
+> dav4jvm is currently being rewritten to use ktor instead of OkHttp to allow Kotlin Multiplatform support, and other engines.
+> 
+> In the mean time, there are two packages available:
+> - `at.bitfire.dav4jvm.okhttp` (the current one, using OkHttp, JVM only)
+> - `io.github.mcdjuady.ktor` (new package, uses ktor, supports Kotlin Multiplatform)
+> 
+> There's some common code shared between both packages, **and we cannot guarantee** that all of it is excluded from cross-dependencies (generic code using ktor-specific functions).
+> The usages are most likely indicated in the kdoc, but something might be missing.
+> 
+> Take this into consideration if you are going to exclude the ktor dependency on your project.
+
 
 ## Installation
 

src/main/kotlin/at/bitfire/dav4jvm/HttpHeaderNames.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright © All Contributors. See LICENSE and AUTHORS in the root directory for details.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ */
+
+package at.bitfire.dav4jvm
+
+object HttpHeaderNames {
+    /** [RFC4229 Section-2.1.2](https://datatracker.ietf.org/doc/html/rfc4229#section-2.1.2) */
+    const val Accept: String = "Accept"
+
+    /** [RFC4229 Section-2.1.5](https://datatracker.ietf.org/doc/html/rfc4229#section-2.1.5) */
+    const val AcceptEncoding: String = "Accept-Encoding"
+
+    /** [RFC4229 Section-2.1.45](https://datatracker.ietf.org/doc/html/rfc4229#section-2.1.45) */
+    const val ETag: String = "ETag"
+
+    /** [RFC6638 Section-8.2](https://datatracker.ietf.org/doc/html/rfc6638#section-8.2) */
+    const val ScheduleTag: String = "Schedule-Tag"
+}

src/main/kotlin/at/bitfire/dav4jvm/XmlReader.kt

@@ -158,6 +158,8 @@ class XmlReader(
      * Processes all the tags named [tagName], and sends every tag that has the [CONTENT_TYPE]
      * attribute with [onNewType].
      *
+     * **Requires Ktor.**
+     *
      * @param tagName The name of the tag that contains the [CONTENT_TYPE] attribute value.
      * @param onNewType Called every time a new [ContentType] is found.
      */

src/main/kotlin/at/bitfire/dav4jvm/property/caldav/ScheduleTag.kt

@@ -10,13 +10,12 @@
 
 package at.bitfire.dav4jvm.property.caldav
 
+import at.bitfire.dav4jvm.HttpHeaderNames
 import at.bitfire.dav4jvm.Property
 import at.bitfire.dav4jvm.PropertyFactory
 import at.bitfire.dav4jvm.QuotedStringUtils
 import at.bitfire.dav4jvm.XmlReader
-import at.bitfire.dav4jvm.property.webdav.GetETag
 import io.ktor.client.statement.HttpResponse
-import io.ktor.http.HttpHeaders
 import okhttp3.Response
 import org.xmlpull.v1.XmlPullParser
 
@@ -29,11 +28,16 @@ data class ScheduleTag(
         @JvmField
         val NAME = Property.Name(NS_CALDAV, "schedule-tag")
 
+        /**
+         * Creates a [ScheduleTag] from an HTTP response's `Schedule-Tag` header.
+         *
+         * **Requires Ktor.**
+         */
         fun fromHttpResponse(response: HttpResponse) =
-            response.headers[HttpHeaders.ScheduleTag]?.let { ScheduleTag(it) }
+            response.headers[HttpHeaderNames.ScheduleTag]?.let { ScheduleTag(it) }
 
         fun fromResponse(response: Response) =
-            response.header(HttpHeaders.ScheduleTag)?.let { ScheduleTag(it) }
+            response.header(HttpHeaderNames.ScheduleTag)?.let { ScheduleTag(it) }
 
     }
 

src/main/kotlin/at/bitfire/dav4jvm/property/caldav/SupportedCalendarData.kt

@@ -31,6 +31,11 @@ data class SupportedCalendarData(
 
     }
 
+    /**
+     * Checks whether the supported calendar data includes JCal (application/calendar+json).
+     *
+     * **Requires Ktor.**
+     */
     fun hasJCal() = types
         .map { ContentType.parse(it) }
         .any { ContentType.Application.contains(it) && "calendar+json".equals(it.contentSubtype, true) }

src/main/kotlin/at/bitfire/dav4jvm/property/carddav/SupportedAddressData.kt

@@ -31,9 +31,20 @@ class SupportedAddressData(
 
     }
 
+    /**
+     * Checks whether the supported address data includes vCard 4.0 (`text/vcard; version=4.0`).
+     *
+     * **Requires Ktor.**
+     */
     fun hasVCard4() = types
         .map { try { ContentType.parse(it) } catch (_: Exception) { ContentType.Any } }
         .any { "text/vcard; version=4.0".equals(it.toString(), true) }
+
+    /**
+     * Checks whether the supported address data includes JCard (`application/vcard+json`).
+     *
+     * **Requires Ktor.**
+     */
     fun hasJCard() = types
         .map { try { ContentType.parse(it) } catch (_: Exception) { ContentType.Any } }
         .any { ContentType.Application.contains(it) && "vcard+json".equals(it.contentSubtype, true) }

src/main/kotlin/at/bitfire/dav4jvm/property/webdav/GetETag.kt

@@ -10,12 +10,12 @@
 
 package at.bitfire.dav4jvm.property.webdav
 
+import at.bitfire.dav4jvm.HttpHeaderNames
 import at.bitfire.dav4jvm.Property
 import at.bitfire.dav4jvm.PropertyFactory
 import at.bitfire.dav4jvm.QuotedStringUtils
 import at.bitfire.dav4jvm.XmlReader
 import io.ktor.client.statement.HttpResponse
-import io.ktor.http.HttpHeaders
 import okhttp3.Response
 import org.xmlpull.v1.XmlPullParser
 
@@ -33,11 +33,16 @@ data class GetETag(
         @JvmField
         val NAME = Property.Name(NS_WEBDAV, "getetag")
 
+        /**
+         * Creates a [GetETag] from an HTTP response's `ETag` header.
+         *
+         * **Requires Ktor.**
+         */
         fun fromHttpResponse(response: HttpResponse) =
-            response.headers[HttpHeaders.ETag]?.let { GetETag(it) }
+            response.headers[HttpHeaderNames.ETag]?.let { GetETag(it) }
 
         fun fromResponse(response: Response) =
-            response.header("ETag")?.let { GetETag(it) }
+            response.header(HttpHeaderNames.ETag)?.let { GetETag(it) }
     }
 
     /**