GH-20: Fix Link pagination Link header parsing

Fixes: #20

The link in the `timeline` response header may come with `rel="prev"`.
Since we are interested in the `rel="next"`, remove everything before `rel="prev"` including this `prev` token

Author: artembilan

src/main/kotlin/io/spring/github/api/WebClientGitHubApi.kt

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2019 the original author or authors.
+ * Copyright 2002-2025 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -35,6 +35,7 @@ import java.util.*
 
 /**
  * @author Rob Winch
+ * @author Artem Bilan
  */
 class WebClientGitHubApi(val webClient: WebClient = WebClient.create(), val baseGitHubUrl: String = "https://api.github.com") : GitHubApi {
     override fun getPermissionForDefaultLogin(repositoryRef: RepositoryRef, accessToken: String): Mono<Permission> {
@@ -289,10 +290,17 @@ class WebClientGitHubApi(val webClient: WebClient = WebClient.create(), val base
     }
 
     private fun next(httpHeaders : HttpHeaders) : String? {
-        val linkHeaderValue = httpHeaders.getFirst("Link")
+        var linkHeaderValue = httpHeaders.getFirst("Link")
         if (linkHeaderValue == null) {
             return null
         }
+
+        val relPrevToken = """rel="prev", """
+        val index = linkHeaderValue.indexOf(relPrevToken)
+        if (index != -1) {
+            linkHeaderValue = linkHeaderValue.substring(index + relPrevToken.length)
+        }
+
         val nextRegex = """.*?<(.*?)>; rel="next".*""".toRegex()
         if (!linkHeaderValue.matches(nextRegex)) {
             return null

src/test/kotlin/io/spring/github/RegexTest.kt

@@ -17,15 +17,39 @@
 package io.spring.github
 
 import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.assertThatNoException
 import org.junit.jupiter.api.Test
+import java.net.URI
 
 /**
  * @author Rob Winch
  */
 class RegexTest {
-    @Test
-    fun regex() {
-        val r = """Fixes: gh-\d+""".toRegex()
-        assertThat(r.containsMatchIn("Hi\n\nHello\r\n\r\nFixes: gh-123")).isTrue()
-    }
+
+	@Test
+	fun regex() {
+		val r = """Fixes: gh-\d+""".toRegex()
+		assertThat(r.containsMatchIn("Hi\n\nHello\r\n\r\nFixes: gh-123")).isTrue()
+	}
+
+	@Test
+	fun nextLinkReplace() {
+		var linkHeaderValue =
+			"""<https://api.github.com/repositories/2090979/issues/10083/timeline?page=1>; rel="prev", <https://api.github.com/repositories/2090979/issues/10083/timeline?page=3>; rel="next", <https://api.github.com/repositories/2090979/issues/10083/timeline?page=3>; rel="last", <https://api.github.com/repositories/2090979/issues/10083/timeline?page=1>; rel="first""""
+
+		val relPrevToken = """rel="prev", """
+
+		val index = linkHeaderValue.indexOf(relPrevToken)
+		if (index != -1) {
+			linkHeaderValue = linkHeaderValue.substring(index + relPrevToken.length)
+		}
+
+		val nextRegex = """.*?<(.*?)>; rel="next".*"""
+		assertThat(linkHeaderValue).matches(nextRegex)
+
+		assertThatNoException().isThrownBy {
+			URI.create(linkHeaderValue.replace(nextRegex.toRegex(), "$1"))
+		}
+	}
+
 }