Rework get-snapshots predicates

qa/smoke-test-http/src/internalClusterTest/java/org/elasticsearch/http/snapshots/RestGetSnapshotsIT.java

@@ -12,6 +12,7 @@
 import org.apache.http.client.methods.HttpGet;
 import org.elasticsearch.action.ActionFuture;
 import org.elasticsearch.action.admin.cluster.snapshots.create.CreateSnapshotResponse;
+import org.elasticsearch.action.admin.cluster.snapshots.get.After;
 import org.elasticsearch.action.admin.cluster.snapshots.get.GetSnapshotsRequest;
 import org.elasticsearch.action.admin.cluster.snapshots.get.GetSnapshotsResponse;
 import org.elasticsearch.action.admin.cluster.snapshots.get.SnapshotSortKey;
@@ -386,7 +387,7 @@ private static void assertStablePagination(String repoName, Collection<String> a
                 final GetSnapshotsResponse getSnapshotsResponse = sortedWithLimit(
                     repoName,
                     sort,
-                    sort.encodeAfterQueryParam(after),
+                    After.fromSnapshotInfo(after, sort).toQueryParam(),
                     i,
                     order,
                     includeIndexNames

server/src/internalClusterTest/java/org/elasticsearch/snapshots/GetSnapshotsIT.java

@@ -20,6 +20,7 @@
 import org.elasticsearch.action.admin.cluster.snapshots.create.CreateSnapshotRequest;
 import org.elasticsearch.action.admin.cluster.snapshots.create.CreateSnapshotResponse;
 import org.elasticsearch.action.admin.cluster.snapshots.create.TransportCreateSnapshotAction;
+import org.elasticsearch.action.admin.cluster.snapshots.get.After;
 import org.elasticsearch.action.admin.cluster.snapshots.get.GetSnapshotsRequest;
 import org.elasticsearch.action.admin.cluster.snapshots.get.GetSnapshotsRequestBuilder;
 import org.elasticsearch.action.admin.cluster.snapshots.get.GetSnapshotsResponse;
@@ -826,7 +827,7 @@ private static void assertStablePagination(String[] repoNames, Collection<String
                 final GetSnapshotsResponse getSnapshotsResponse = sortedWithLimit(
                     repoNames,
                     sort,
-                    sort.encodeAfterQueryParam(after),
+                    After.fromSnapshotInfo(after, sort).toQueryParam(),
                     i,
                     order
                 );
@@ -1144,7 +1145,7 @@ public void testAllFeatures() {
                 .sort(sortKey)
                 .order(order)
                 .size(nextSize)
-                .after(SnapshotSortKey.decodeAfterQueryParam(nextRequestAfter))
+                .after(After.decodeAfterQueryParam(nextRequestAfter))
                 .states(requestedStates);
             final GetSnapshotsResponse nextResponse = safeAwait(l -> client().execute(TransportGetSnapshotsAction.TYPE, nextRequest, l));
 

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/After.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.action.admin.cluster.snapshots.get;
+
+import org.elasticsearch.common.io.stream.StreamInput;
+import org.elasticsearch.common.io.stream.StreamOutput;
+import org.elasticsearch.common.io.stream.Writeable;
+import org.elasticsearch.snapshots.SnapshotInfo;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.util.Base64;
+
+/**
+ * Cursor value for the {@code ?after} pagination parameter of the get-snapshots API. Encodes the sort key value plus snapshot and
+ * repository names for tiebreaking. Can be decoded from a query param and passed in a {@link GetSnapshotsRequest}, and used by
+ * {@link AfterPredicates} to filter out snapshots that are not after this cursor.
+ */
+public record After(String value, String repoName, String snapshotName) implements Writeable {
+
+    public After(StreamInput in) throws IOException {
+        this(in.readString(), in.readString(), in.readString());
+    }
+
+    @Override
+    public void writeTo(StreamOutput out) throws IOException {
+        out.writeString(value);
+        out.writeString(repoName);
+        out.writeString(snapshotName);
+    }
+
+    /**
+     * Build an {@link After} cursor from the last snapshot in a page, for use when building the {@code ?after} value for the next request.
+     *
+     * @param snapshotInfo the snapshot (typically the last in the current page)
+     * @param sortBy      the sort key used for the request
+     * @return the cursor
+     */
+    public static After fromSnapshotInfo(SnapshotInfo snapshotInfo, SnapshotSortKey sortBy) {
+        return new After(switch (sortBy) {
+            case START_TIME -> Long.toString(snapshotInfo.startTime());
+            case NAME -> snapshotInfo.snapshotId().getName();
+            case DURATION -> Long.toString(snapshotInfo.endTime() - snapshotInfo.startTime());
+            case INDICES -> Integer.toString(snapshotInfo.indices().size());
+            case SHARDS -> Integer.toString(snapshotInfo.totalShards());
+            case FAILED_SHARDS -> Integer.toString(snapshotInfo.failedShards());
+            case REPOSITORY -> snapshotInfo.repository();
+        }, snapshotInfo.repository(), snapshotInfo.snapshotId().getName());
+    }
+
+    /**
+     * Encode this cursor as the {@code ?after} query parameter value (base64url-encoded "value,repoName,snapshotName").
+     *
+     * @return the encoded string for use as the {@code after} query parameter
+     */
+    public String toQueryParam() {
+        return Base64.getUrlEncoder().encodeToString((value + "," + repoName + "," + snapshotName).getBytes(StandardCharsets.UTF_8));
+    }
+
+    /**
+     * Decode the {@code ?after} query parameter into an {@link After} instance.
+     *
+     * @param param the value of the {@code after} query parameter (base64url-encoded "value,repoName,snapshotName")
+     * @return the decoded cursor
+     * @throws IllegalArgumentException if the parameter format is invalid
+     */
+    public static After decodeAfterQueryParam(String param) {
+        final String[] parts = new String(Base64.getUrlDecoder().decode(param), StandardCharsets.UTF_8).split(",");
+        if (parts.length != 3) {
+            throw new IllegalArgumentException("invalid ?after parameter [" + param + "]");
+        }
+        return new After(parts[0], parts[1], parts[2]);
+    }
+}

server/src/main/java/org/elasticsearch/action/admin/cluster/snapshots/get/AfterPredicates.java

@@ -0,0 +1,101 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.action.admin.cluster.snapshots.get;
+
+import org.elasticsearch.core.Nullable;
+import org.elasticsearch.search.sort.SortOrder;
+import org.elasticsearch.snapshots.SnapshotInfo;
+
+import java.util.function.Predicate;
+import java.util.function.ToLongFunction;
+
+/**
+ * Predicate for the {@code ?after} filter of the get-snapshots action. The {@link #test(SnapshotInfo)} predicate is applied to
+ * {@link SnapshotInfo} instances to filter out those that sort before the cursor value (i.e. were returned on earlier pages of results).
+ */
+final class AfterPredicates {
+
+    private static final AfterPredicates MATCH_ALL = new AfterPredicates(null);
+
+    @Nullable // if MATCH_ALL
+    private final Predicate<SnapshotInfo> snapshotPredicate;
+
+    private AfterPredicates(@Nullable Predicate<SnapshotInfo> snapshotPredicate) {
+        this.snapshotPredicate = snapshotPredicate;
+    }
+
+    /**
+     * Test using the full {@link SnapshotInfo}. Returns true if the snapshot should be included (sorts after the cursor).
+     */
+    boolean test(SnapshotInfo snapshotInfo) {
+        return snapshotPredicate == null || snapshotPredicate.test(snapshotInfo);
+    }
+
+    static AfterPredicates forAfter(@Nullable After after, SnapshotSortKey sortBy, SortOrder order) {
+        if (after == null) {
+            return MATCH_ALL;
+        }
+
+        return new AfterPredicates(switch (sortBy) {
+            case START_TIME -> longValuePredicate(after, SnapshotInfo::startTime, order);
+            case NAME -> namePredicate(after, order);
+            case DURATION -> longValuePredicate(after, info -> info.endTime() - info.startTime(), order);
+            case INDICES -> longValuePredicate(after, info -> info.indices().size(), order);
+            case SHARDS -> longValuePredicate(after, SnapshotInfo::totalShards, order);
+            case FAILED_SHARDS -> longValuePredicate(after, SnapshotInfo::failedShards, order);
+            case REPOSITORY -> repositoryPredicate(after, order);
+        });
+    }
+
+    private static Predicate<SnapshotInfo> longValuePredicate(After after, ToLongFunction<SnapshotInfo> extractor, SortOrder sortOrder) {
+        final long afterVal = Long.parseLong(after.value());
+        final String snapshotName = after.snapshotName();
+        final String repoName = after.repoName();
+        return sortOrder == SortOrder.ASC ? info -> {
+            final long val = extractor.applyAsLong(info);
+            return afterVal < val || (afterVal == val && compareName(snapshotName, repoName, info) < 0);
+        } : info -> {
+            final long val = extractor.applyAsLong(info);
+            return afterVal > val || (afterVal == val && compareName(snapshotName, repoName, info) > 0);
+        };
+    }
+
+    private static Predicate<SnapshotInfo> namePredicate(After after, SortOrder sortOrder) {
+        final String snapshotName = after.snapshotName();
+        final String repoName = after.repoName();
+        return sortOrder == SortOrder.ASC
+            ? (info -> compareName(snapshotName, repoName, info) < 0)
+            : (info -> compareName(snapshotName, repoName, info) > 0);
+    }
+
+    private static Predicate<SnapshotInfo> repositoryPredicate(After after, SortOrder sortOrder) {
+        final String snapshotName = after.snapshotName();
+        final String repoName = after.repoName();
+        return sortOrder == SortOrder.ASC
+            ? (info -> compareRepositoryName(snapshotName, repoName, info) < 0)
+            : (info -> compareRepositoryName(snapshotName, repoName, info) > 0);
+    }
+
+    private static int compareName(String name, String repoName, SnapshotInfo info) {
+        final int res = name.compareTo(info.snapshotId().getName());
+        if (res != 0) {
+            return res;
+        }
+        return repoName.compareTo(info.repository());
+    }
+
+    private static int compareRepositoryName(String name, String repoName, SnapshotInfo info) {
+        final int res = repoName.compareTo(info.repository());
+        if (res != 0) {
+            return res;
+        }
+        return name.compareTo(info.snapshotId().getName());
+    }
+}