fix(abg): use the release date of the latest version for lastUpdated (#1612)

This makes the metadata file content more stable and allows to provide a checksum,
as Kotlin for example is quite unhappy if it finds no checksum or cannot successfully verify it.

Without this every request would produce a different file and thus also a different checksum file,
so the checksum would never match the file contents.

Author: Vampire

maven-binding-builder/src/main/kotlin/io/github/typesafegithub/workflows/mavenbinding/MavenMetadataBuilding.kt

@@ -1,24 +1,21 @@
 package io.github.typesafegithub.workflows.mavenbinding
 
 import io.github.typesafegithub.workflows.shared.internal.fetchAvailableVersions
-import java.time.Instant
-import java.time.ZoneId
 import java.time.format.DateTimeFormatter
 
 internal suspend fun buildMavenMetadataFile(
     owner: String,
     name: String,
     githubToken: String,
 ): String {
-    val lastUpdated =
-        DateTimeFormatter
-            .ofPattern("yyyyMMddHHmmss")
-            .withZone(ZoneId.systemDefault())
-            .format(Instant.now())
     val availableMajorVersions =
         fetchAvailableVersions(owner = owner, name = name.substringBefore("__"), githubToken = githubToken)
             .filter { it.isMajorVersion() }
     val newest = availableMajorVersions.max()
+    val lastUpdated =
+        DateTimeFormatter
+            .ofPattern("yyyyMMddHHmmss")
+            .format(newest.getReleaseDate())
     return """
         <?xml version="1.0" encoding="UTF-8"?>
         <metadata>

shared-internal/src/main/kotlin/io/github/typesafegithub/workflows/shared/internal/GithubApi.kt

@@ -9,6 +9,7 @@ import io.ktor.client.request.get
 import io.ktor.serialization.kotlinx.json.json
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.json.Json
+import java.time.ZonedDateTime
 
 suspend fun fetchAvailableVersions(
     owner: String,
@@ -19,12 +20,27 @@ suspend fun fetchAvailableVersions(
         apiTagsUrl(owner = owner, name = name),
         apiBranchesUrl(owner = owner, name = name),
     ).flatMap { url -> fetchGithubRefs(url, githubToken) }
-        .versions()
+        .versions(githubToken)
 
-private fun List<GithubRef>.versions(): List<Version> =
+private fun List<GithubRef>.versions(githubToken: String?): List<Version> =
     this.map { githubRef ->
         val version = githubRef.ref.substringAfterLast("/")
-        Version(version)
+        Version(version) {
+            val response =
+                httpClient
+                    .get(urlString = githubRef.`object`.url) {
+                        if (githubToken != null) {
+                            bearerAuth(githubToken)
+                        }
+                    }
+            val releaseDate =
+                when (githubRef.`object`.type) {
+                    "tag" -> response.body<Tag>().tagger
+                    "commit" -> response.body<Commit>().author
+                    else -> error("Unexpected target object type ${githubRef.`object`.type}")
+                }.date
+            ZonedDateTime.parse(releaseDate)
+        }
     }
 
 private suspend fun fetchGithubRefs(
@@ -51,6 +67,28 @@ private fun apiBranchesUrl(
 @Serializable
 private data class GithubRef(
     val ref: String,
+    val `object`: Object,
+)
+
+@Serializable
+private data class Object(
+    val type: String,
+    val url: String,
+)
+
+@Serializable
+private data class Tag(
+    val tagger: Person,
+)
+
+@Serializable
+private data class Commit(
+    val author: Person,
+)
+
+@Serializable
+private data class Person(
+    val date: String,
 )
 
 private val httpClient by lazy {

shared-internal/src/main/kotlin/io/github/typesafegithub/workflows/shared/internal/model/Version.kt

@@ -1,7 +1,10 @@
 package io.github.typesafegithub.workflows.shared.internal.model
 
+import java.time.ZonedDateTime
+
 data class Version(
     val version: String,
+    private val dateProvider: suspend () -> ZonedDateTime? = { null },
 ) : Comparable<Version> {
     val input: String = version.removePrefix("v").removePrefix("V")
     val major = input.substringBefore(".").toIntOrNull() ?: 0
@@ -23,4 +26,6 @@ data class Version(
     override fun toString(): String = version
 
     fun isMajorVersion(): Boolean = version.contains(".").not()
+
+    suspend fun getReleaseDate() = dateProvider()
 }