Adding initial migration classes

Author: jonathan-buttner

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/migration/EISMigrationContext.java

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+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.migration;
+
+import org.elasticsearch.xpack.inference.services.elastic.authorization.ElasticInferenceServiceAuthorizationModel;
+
+import java.util.Objects;
+
+/**
+ * Migration context for EIS (Elastic Inference Service) migrations.
+ * Contains the authorization model which provides access to endpoint metadata
+ * needed for batch migrations.
+ */
+public record EISMigrationContext(ElasticInferenceServiceAuthorizationModel authModel) implements MigrationContext {
+
+    public EISMigrationContext {
+        Objects.requireNonNull(authModel);
+    }
+
+    @Override
+    public ContextType getContextType() {
+        return ContextType.EIS;
+    }
+}

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/migration/EmptyMigrationContext.java

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+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.migration;
+
+/**
+ * Empty migration context for generic migrations that don't require
+ * migration-specific data. Used for single-endpoint migrations that
+ * only need the endpoint data itself.
+ */
+public enum EmptyMigrationContext implements MigrationContext {
+    INSTANCE;
+
+    @Override
+    public ContextType getContextType() {
+        return ContextType.EMPTY;
+    }
+}

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/migration/EndpointMigration.java

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+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.migration;
+
+import org.elasticsearch.core.Nullable;
+import org.elasticsearch.core.Strings;
+import org.elasticsearch.inference.Model;
+
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Unified interface for endpoint migrations supporting both single-endpoint
+ * and batch execution modes. Migrations can be run lazily when endpoints are
+ * read (single-endpoint) or efficiently during batch operations (batch mode).
+ */
+public interface EndpointMigration {
+
+    /**
+     * Returns the target version this migration migrates endpoints to.
+     * Migrations are executed in order from lowest to highest target version.
+     *
+     * @return the target version number
+     */
+    long getTargetVersion();
+
+    /**
+     * Returns the set of service names this migration applies to.
+     * Only endpoints from these services will be considered for migration.
+     *
+     * @return set of applicable service names
+     */
+    Set<String> getApplicableServices();
+
+    /**
+     * Checks if this migration is applicable to the given model.
+     * This is used to filter which migrations should be run for a specific endpoint.
+     *
+     * @param model the model to check
+     * @return true if this migration applies to the model
+     */
+    default boolean isApplicable(Model model) {
+        return getApplicableServices().contains(model.getConfigurations().getService());
+    }
+
+    /**
+     * Returns whether this migration supports batch execution mode.
+     * Batch migrations can process multiple endpoints efficiently with access
+     * to migration context data (e.g., authorization responses).
+     *
+     * @return true if batch mode is supported, false otherwise
+     */
+    default boolean supportsBatch() {
+        return false;
+    }
+
+    /**
+     * Migrates a single endpoint. This method is called for single-endpoint
+     * migrations when endpoints are read (lazy migration).
+     *
+     * @param model the model to migrate
+     * @param context optional migration context (may be null for single-endpoint migrations)
+     * @return the migration result
+     */
+    MigrationResult migrate(Model model, @Nullable MigrationContext context);
+
+    /**
+     * Migrates multiple endpoints in batch mode. This method is called when
+     * batch migrations are supported and context data is available.
+     *
+     * @param models the models to migrate
+     * @param context optional migration context (typically provided for batch migrations)
+     * @return list of migration results, one per model
+     */
+    default List<MigrationResult> migrateBatch(List<Model> models, @Nullable MigrationContext context) {
+        throw new UnsupportedOperationException("Batch migration not supported by this migration");
+    }
+
+    /**
+     * Record representing a successfully migrated model.
+     *
+     * @param model the migrated model
+     */
+    record MigratedModel(Model model) {
+        public MigratedModel {
+            if (model == null) {
+                throw new IllegalArgumentException("Migrated model cannot be null");
+            }
+        }
+    }
+
+    /**
+     * Record representing the result of a migration operation.
+     *
+     * @param success whether the migration succeeded
+     * @param migratedModel the migrated model if successful, null otherwise
+     * @param errorMessage error message if migration failed, null otherwise
+     */
+    record MigrationResult(boolean success, @Nullable MigratedModel migratedModel, @Nullable String errorMessage) {
+
+        /**
+         * Creates a successful migration result.
+         *
+         * @param model the migrated model
+         * @return successful migration result
+         */
+        public static MigrationResult success(Model model) {
+            return new MigrationResult(true, new MigratedModel(model), null);
+        }
+
+        /**
+         * Creates a failed migration result.
+         *
+         * @param errorMessage the error message describing the failure
+         * @return failed migration result
+         */
+        public static MigrationResult failure(String errorMessage) {
+            return new MigrationResult(false, null, errorMessage);
+        }
+
+        /**
+         * Creates a failed migration result with a formatted error message.
+         *
+         * @param format the format string
+         * @param args the format arguments
+         * @return failed migration result
+         */
+        public static MigrationResult failure(String format, Object... args) {
+            return failure(Strings.format(format, args));
+        }
+    }
+}

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/migration/MigrationContext.java

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+/*
+ * 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; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+package org.elasticsearch.xpack.inference.migration;
+
+/**
+ * Context interface for passing migration-specific data to batch migrations.
+ * Different migration types can use different context implementations to pass
+ * the data they need (e.g., authorization models, service-specific data).
+ */
+public interface MigrationContext {
+    /**
+     * Returns the type of this context, which can be used to safely cast
+     * the context to the appropriate implementation type.
+     *
+     * @return the context type
+     */
+    ContextType getContextType();
+
+    /**
+     * Enumeration of supported context types for type-safe context access.
+     */
+    enum ContextType {
+        EIS,
+        EMPTY
+    }
+}