/*
 * Copyright 2024-2026 the original author or authors.
 */

package io.modelcontextprotocol.server;

import java.time.Duration;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.BiFunction;

import io.modelcontextprotocol.common.McpTransportContext;
import io.modelcontextprotocol.json.McpJsonMapper;
import io.modelcontextprotocol.json.TypeRef;
import io.modelcontextprotocol.json.schema.JsonSchemaValidator;
import io.modelcontextprotocol.server.McpStatelessServerFeatures.AsyncResourceTemplateSpecification;
import io.modelcontextprotocol.spec.McpError;
import io.modelcontextprotocol.spec.McpSchema;
import io.modelcontextprotocol.spec.McpSchema.CallToolResult;
import io.modelcontextprotocol.spec.McpSchema.CompleteResult.CompleteCompletion;
import io.modelcontextprotocol.spec.McpSchema.ErrorCodes;
import io.modelcontextprotocol.spec.McpSchema.PromptReference;
import io.modelcontextprotocol.spec.McpSchema.ResourceReference;
import io.modelcontextprotocol.spec.McpSchema.Tool;
import io.modelcontextprotocol.spec.McpStatelessServerTransport;
import io.modelcontextprotocol.util.Assert;
import io.modelcontextprotocol.util.DefaultMcpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.McpUriTemplateManagerFactory;
import io.modelcontextprotocol.util.ToolInputValidator;
import io.modelcontextprotocol.util.Utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;

import static io.modelcontextprotocol.spec.McpError.RESOURCE_NOT_FOUND;

/**
 * A stateless MCP server implementation for use with Streamable HTTP transport types. It
 * allows simple horizontal scalability since it does not maintain a session and does not
 * require initialization. Each instance of the server can be reached with no prior
 * knowledge and can serve the clients with the capabilities it supports.
 *
 * @author Dariusz Jędrzejczyk
 */
public class McpStatelessAsyncServer {

	private static final Logger logger = LoggerFactory.getLogger(McpStatelessAsyncServer.class);

	private final McpStatelessServerTransport mcpTransportProvider;

	private final McpJsonMapper jsonMapper;

	private final McpSchema.ServerCapabilities serverCapabilities;

	private final McpSchema.Implementation serverInfo;

	private final String instructions;

	private final CopyOnWriteArrayList<McpStatelessServerFeatures.AsyncToolSpecification> tools = new CopyOnWriteArrayList<>();

	private final ConcurrentHashMap<String, McpStatelessServerFeatures.AsyncResourceTemplateSpecification> resourceTemplates = new ConcurrentHashMap<>();

	private final ConcurrentHashMap<String, McpStatelessServerFeatures.AsyncResourceSpecification> resources = new ConcurrentHashMap<>();

	private final ConcurrentHashMap<String, McpStatelessServerFeatures.AsyncPromptSpecification> prompts = new ConcurrentHashMap<>();

	private final ConcurrentHashMap<McpSchema.CompleteReference, McpStatelessServerFeatures.AsyncCompletionSpecification> completions = new ConcurrentHashMap<>();

	private List<String> protocolVersions;

	private McpUriTemplateManagerFactory uriTemplateManagerFactory = new DefaultMcpUriTemplateManagerFactory();

	private final JsonSchemaValidator jsonSchemaValidator;

	private final boolean validateToolInputs;

	McpStatelessAsyncServer(McpStatelessServerTransport mcpTransport, McpJsonMapper jsonMapper,
			McpStatelessServerFeatures.Async features, Duration requestTimeout,
			McpUriTemplateManagerFactory uriTemplateManagerFactory, JsonSchemaValidator jsonSchemaValidator,
			boolean validateToolInputs) {
		this.mcpTransportProvider = mcpTransport;
		this.jsonMapper = jsonMapper;
		this.serverInfo = features.serverInfo();
		this.serverCapabilities = features.serverCapabilities();
		this.instructions = features.instructions();
		this.tools.addAll(withStructuredOutputHandling(jsonSchemaValidator, features.tools()));
		this.resources.putAll(features.resources());
		this.resourceTemplates.putAll(features.resourceTemplates());
		this.prompts.putAll(features.prompts());
		this.completions.putAll(features.completions());
		this.uriTemplateManagerFactory = uriTemplateManagerFactory;
		this.jsonSchemaValidator = jsonSchemaValidator;
		this.validateToolInputs = validateToolInputs;

		Map<String, McpStatelessRequestHandler<?>> requestHandlers = new HashMap<>();

		// Initialize request handlers for standard MCP methods

		// Ping MUST respond with an empty data, but not NULL response.
		requestHandlers.put(McpSchema.METHOD_PING, (ctx, params) -> Mono.just(Map.of()));

		requestHandlers.put(McpSchema.METHOD_INITIALIZE, asyncInitializeRequestHandler());

		// Add tools API handlers if the tool capability is enabled
		if (this.serverCapabilities.tools() != null) {
			requestHandlers.put(McpSchema.METHOD_TOOLS_LIST, toolsListRequestHandler());
			requestHandlers.put(McpSchema.METHOD_TOOLS_CALL, toolsCallRequestHandler());
		}

		// Add resources API handlers if provided
		if (this.serverCapabilities.resources() != null) {
			requestHandlers.put(McpSchema.METHOD_RESOURCES_LIST, resourcesListRequestHandler());
			requestHandlers.put(McpSchema.METHOD_RESOURCES_READ, resourcesReadRequestHandler());
			requestHandlers.put(McpSchema.METHOD_RESOURCES_TEMPLATES_LIST, resourceTemplateListRequestHandler());
		}

		// Add prompts API handlers if provider exists
		if (this.serverCapabilities.prompts() != null) {
			requestHandlers.put(McpSchema.METHOD_PROMPT_LIST, promptsListRequestHandler());
			requestHandlers.put(McpSchema.METHOD_PROMPT_GET, promptsGetRequestHandler());
		}

		// Add completion API handlers if the completion capability is enabled
		if (this.serverCapabilities.completions() != null) {
			requestHandlers.put(McpSchema.METHOD_COMPLETION_COMPLETE, completionCompleteRequestHandler());
		}

		this.protocolVersions = new ArrayList<>(mcpTransport.protocolVersions());

		McpStatelessServerHandler handler = new DefaultMcpStatelessServerHandler(requestHandlers, Map.of());
		mcpTransport.setMcpHandler(handler);
	}

	// ---------------------------------------
	// Lifecycle Management
	// ---------------------------------------
	private McpStatelessRequestHandler<McpSchema.InitializeResult> asyncInitializeRequestHandler() {
		return (ctx, req) -> Mono.defer(() -> {
			McpSchema.InitializeRequest initializeRequest = this.jsonMapper.convertValue(req,
					McpSchema.InitializeRequest.class);

			logger.info("Client initialize request - Protocol: {}, Capabilities: {}, Info: {}",
					initializeRequest.protocolVersion(), initializeRequest.capabilities(),
					initializeRequest.clientInfo());

			// The server MUST respond with the highest protocol version it supports
			// if
			// it does not support the requested (e.g. Client) version.
			String serverProtocolVersion = this.protocolVersions.get(this.protocolVersions.size() - 1);

			if (this.protocolVersions.contains(initializeRequest.protocolVersion())) {
				// If the server supports the requested protocol version, it MUST
				// respond
				// with the same version.
				serverProtocolVersion = initializeRequest.protocolVersion();
			}
			else {
				logger.warn(
						"Client requested unsupported protocol version: {}, so the server will suggest the {} version instead",
						initializeRequest.protocolVersion(), serverProtocolVersion);
			}

			return Mono.just(new McpSchema.InitializeResult(serverProtocolVersion, this.serverCapabilities,
					this.serverInfo, this.instructions));
		});
	}

	/**
	 * Get the server capabilities that define the supported features and functionality.
	 * @return The server capabilities
	 */
	public McpSchema.ServerCapabilities getServerCapabilities() {
		return this.serverCapabilities;
	}

	/**
	 * Get the server implementation information.
	 * @return The server implementation details
	 */
	public McpSchema.Implementation getServerInfo() {
		return this.serverInfo;
	}

	/**
	 * Gracefully closes the server, allowing any in-progress operations to complete.
	 * @return A Mono that completes when the server has been closed
	 */
	public Mono<Void> closeGracefully() {
		return this.mcpTransportProvider.closeGracefully();
	}

	/**
	 * Close the server immediately.
	 */
	public void close() {
		this.mcpTransportProvider.close();
	}

	// ---------------------------------------
	// Tool Management
	// ---------------------------------------

	private static List<McpStatelessServerFeatures.AsyncToolSpecification> withStructuredOutputHandling(
			JsonSchemaValidator jsonSchemaValidator, List<McpStatelessServerFeatures.AsyncToolSpecification> tools) {

		if (Utils.isEmpty(tools)) {
			return tools;
		}

		return tools.stream().map(tool -> withStructuredOutputHandling(jsonSchemaValidator, tool)).toList();
	}

	private static McpStatelessServerFeatures.AsyncToolSpecification withStructuredOutputHandling(
			JsonSchemaValidator jsonSchemaValidator,
			McpStatelessServerFeatures.AsyncToolSpecification toolSpecification) {

		if (toolSpecification.callHandler() instanceof StructuredOutputCallToolHandler) {
			// If the tool is already wrapped, return it as is
			return toolSpecification;
		}

		if (toolSpecification.tool().outputSchema() == null) {
			// If the tool does not have an output schema, return it as is
			return toolSpecification;
		}

		return new McpStatelessServerFeatures.AsyncToolSpecification(toolSpecification.tool(),
				new StructuredOutputCallToolHandler(jsonSchemaValidator, toolSpecification.tool().outputSchema(),
						toolSpecification.callHandler()));
	}

	private static class StructuredOutputCallToolHandler
			implements BiFunction<McpTransportContext, McpSchema.CallToolRequest, Mono<McpSchema.CallToolResult>> {

		private final BiFunction<McpTransportContext, McpSchema.CallToolRequest, Mono<McpSchema.CallToolResult>> delegateHandler;

		private final JsonSchemaValidator jsonSchemaValidator;

		private final Map<String, Object> outputSchema;

		public StructuredOutputCallToolHandler(JsonSchemaValidator jsonSchemaValidator,
				Map<String, Object> outputSchema,
				BiFunction<McpTransportContext, McpSchema.CallToolRequest, Mono<McpSchema.CallToolResult>> delegateHandler) {

			Assert.notNull(jsonSchemaValidator, "JsonSchemaValidator must not be null");
			Assert.notNull(delegateHandler, "Delegate call tool result handler must not be null");

			this.delegateHandler = delegateHandler;
			this.outputSchema = outputSchema;
			this.jsonSchemaValidator = jsonSchemaValidator;
		}

		@Override
		public Mono<CallToolResult> apply(McpTransportContext transportContext, McpSchema.CallToolRequest request) {

			return this.delegateHandler.apply(transportContext, request).map(result -> {

				if (Boolean.TRUE.equals(result.isError())) {
					// If the tool call resulted in an error, skip further validation
					return result;
				}

				if (outputSchema == null) {
					if (result.structuredContent() != null) {
						logger.warn(
								"Tool call with no outputSchema is not expected to have a result with structured content, but got: {}",
								result.structuredContent());
					}
					// Pass through. No validation is required if no output schema is
					// provided.
					return result;
				}

				// If an output schema is provided, servers MUST provide structured
				// results that conform to this schema.
				// https://modelcontextprotocol.io/specification/2025-06-18/server/tools#output-schema
				if (result.structuredContent() == null) {
					String content = "Response missing structured content which is expected when calling tool with non-empty outputSchema";
					logger.warn(content);
					return CallToolResult.builder()
						.content(List.of(McpSchema.TextContent.builder(content).build()))
						.isError(true)
						.build();
				}

				// Validate the result against the output schema
				var validation = this.jsonSchemaValidator.validate(outputSchema, result.structuredContent());

				if (!validation.valid()) {
					String message = "Tool (" + request.name() + ") output validation failed: "
							+ validation.errorMessage();
					logger.warn(message);
					return CallToolResult.builder()
						.content(List.of(McpSchema.TextContent.builder(message).build()))
						.isError(true)
						.build();
				}

				if (Utils.isEmpty(result.content())) {
					// For backwards compatibility, a tool that returns structured
					// content SHOULD also return functionally equivalent unstructured
					// content. (For example, serialized JSON can be returned in a
					// TextContent block.)
					// https://modelcontextprotocol.io/specification/2025-06-18/server/tools#structured-content

					return CallToolResult.builder()
						.content(List.of(McpSchema.TextContent.builder(validation.jsonStructuredOutput()).build()))
						.isError(result.isError())
						.structuredContent(result.structuredContent())
						.build();
				}

				return result;
			});
		}

	}

	/**
	 * Add a new tool specification at runtime.
	 * @param toolSpecification The tool specification to add
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> addTool(McpStatelessServerFeatures.AsyncToolSpecification toolSpecification) {
		if (toolSpecification == null) {
			return Mono.error(new IllegalArgumentException("Tool specification must not be null"));
		}
		if (toolSpecification.tool() == null) {
			return Mono.error(new IllegalArgumentException("Tool must not be null"));
		}
		if (toolSpecification.callHandler() == null) {
			return Mono.error(new IllegalArgumentException("Tool call handler must not be null"));
		}
		if (this.serverCapabilities.tools() == null) {
			return Mono.error(new IllegalStateException("Server must be configured with tool capabilities"));
		}

		try {
			var t = toolSpecification.tool();
			this.jsonSchemaValidator.assertConforms("Tool '" + t.name() + "' inputSchema", t.inputSchema());
			this.jsonSchemaValidator.assertConforms("Tool '" + t.name() + "' outputSchema", t.outputSchema());
		}
		catch (IllegalArgumentException e) {
			return Mono.error(e);
		}

		var wrappedToolSpecification = withStructuredOutputHandling(this.jsonSchemaValidator, toolSpecification);

		return Mono.defer(() -> {
			// Remove tools with duplicate tool names first
			if (this.tools.removeIf(th -> th.tool().name().equals(wrappedToolSpecification.tool().name()))) {
				logger.warn("Replace existing Tool with name '{}'", wrappedToolSpecification.tool().name());
			}

			this.tools.add(wrappedToolSpecification);
			logger.debug("Added tool handler: {}", wrappedToolSpecification.tool().name());

			return Mono.empty();
		});
	}

	/**
	 * List all registered tools.
	 * @return A Flux stream of all registered tools
	 */
	public Flux<Tool> listTools() {
		return Flux.fromIterable(this.tools).map(McpStatelessServerFeatures.AsyncToolSpecification::tool);
	}

	/**
	 * Remove a tool handler at runtime.
	 * @param toolName The name of the tool handler to remove
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> removeTool(String toolName) {
		if (toolName == null) {
			return Mono.error(new IllegalArgumentException("Tool name must not be null"));
		}
		if (this.serverCapabilities.tools() == null) {
			return Mono.error(new IllegalStateException("Server must be configured with tool capabilities"));
		}

		return Mono.defer(() -> {
			if (this.tools.removeIf(toolSpecification -> toolSpecification.tool().name().equals(toolName))) {

				logger.debug("Removed tool handler: {}", toolName);
			}
			else {
				logger.warn("Failed to remove a tool with name '{}' (not found)", toolName);
			}

			return Mono.empty();
		});
	}

	private McpStatelessRequestHandler<McpSchema.ListToolsResult> toolsListRequestHandler() {
		return (ctx, params) -> {
			List<Tool> tools = this.tools.stream()
				.map(McpStatelessServerFeatures.AsyncToolSpecification::tool)
				.toList();
			return Mono.just(McpSchema.ListToolsResult.builder(tools).build());
		};
	}

	private McpStatelessRequestHandler<CallToolResult> toolsCallRequestHandler() {
		return (ctx, params) -> {
			McpSchema.CallToolRequest callToolRequest = jsonMapper.convertValue(params,
					new TypeRef<McpSchema.CallToolRequest>() {
					});

			Optional<McpStatelessServerFeatures.AsyncToolSpecification> toolSpecification = this.tools.stream()
				.filter(tr -> callToolRequest.name().equals(tr.tool().name()))
				.findAny();

			if (toolSpecification.isEmpty()) {
				return Mono.error(McpError.builder(McpSchema.ErrorCodes.INVALID_PARAMS)
					.message("Unknown tool: invalid_tool_name")
					.data("Tool not found: " + callToolRequest.name())
					.build());
			}

			McpSchema.Tool tool = toolSpecification.get().tool();
			CallToolResult validationError = ToolInputValidator.validate(tool, callToolRequest.arguments(),
					this.validateToolInputs, this.jsonSchemaValidator);
			if (validationError != null) {
				return Mono.just(validationError);
			}

			return toolSpecification.get().callHandler().apply(ctx, callToolRequest);
		};
	}

	// ---------------------------------------
	// Resource Management
	// ---------------------------------------

	/**
	 * Add a new resource handler at runtime.
	 * @param resourceSpecification The resource handler to add
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> addResource(McpStatelessServerFeatures.AsyncResourceSpecification resourceSpecification) {
		if (resourceSpecification == null || resourceSpecification.resource() == null) {
			return Mono.error(new IllegalArgumentException("Resource must not be null"));
		}

		if (this.serverCapabilities.resources() == null) {
			return Mono.error(new IllegalStateException("Server must be configured with resource capabilities"));
		}

		return Mono.defer(() -> {
			var previous = this.resources.put(resourceSpecification.resource().uri(), resourceSpecification);
			if (previous != null) {
				logger.warn("Replace existing Resource with URI '{}'", resourceSpecification.resource().uri());
			}
			else {
				logger.debug("Added resource handler: {}", resourceSpecification.resource().uri());
			}
			return Mono.empty();
		});
	}

	/**
	 * List all registered resources.
	 * @return A Flux stream of all registered resources
	 */
	public Flux<McpSchema.Resource> listResources() {
		return Flux.fromIterable(this.resources.values())
			.map(McpStatelessServerFeatures.AsyncResourceSpecification::resource);
	}

	/**
	 * Remove a resource handler at runtime.
	 * @param resourceUri The URI of the resource handler to remove
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> removeResource(String resourceUri) {
		if (resourceUri == null) {
			return Mono.error(new IllegalArgumentException("Resource URI must not be null"));
		}
		if (this.serverCapabilities.resources() == null) {
			return Mono.error(new IllegalStateException("Server must be configured with resource capabilities"));
		}

		return Mono.defer(() -> {
			McpStatelessServerFeatures.AsyncResourceSpecification removed = this.resources.remove(resourceUri);
			if (removed != null) {
				logger.debug("Removed resource handler: {}", resourceUri);
			}
			else {
				logger.warn("Failed to remove a resource with URI '{}' (not found)", resourceUri);
			}
			return Mono.empty();
		});
	}

	/**
	 * Add a new resource template at runtime.
	 * @param resourceTemplateSpecification The resource template to add
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> addResourceTemplate(
			McpStatelessServerFeatures.AsyncResourceTemplateSpecification resourceTemplateSpecification) {

		if (this.serverCapabilities.resources() == null) {
			return Mono.error(new IllegalStateException(
					"Server must be configured with resource capabilities to allow adding resource templates"));
		}

		return Mono.defer(() -> {
			var previous = this.resourceTemplates.put(resourceTemplateSpecification.resourceTemplate().uriTemplate(),
					resourceTemplateSpecification);
			if (previous != null) {
				logger.warn("Replace existing Resource Template with URI '{}'",
						resourceTemplateSpecification.resourceTemplate().uriTemplate());
			}
			else {
				logger.debug("Added resource template handler: {}",
						resourceTemplateSpecification.resourceTemplate().uriTemplate());
			}
			return Mono.empty();
		});
	}

	/**
	 * List all registered resource templates.
	 * @return A Flux stream of all registered resource templates
	 */
	public Flux<McpSchema.ResourceTemplate> listResourceTemplates() {
		return Flux.fromIterable(this.resourceTemplates.values())
			.map(McpStatelessServerFeatures.AsyncResourceTemplateSpecification::resourceTemplate);
	}

	/**
	 * Remove a resource template at runtime.
	 * @param uriTemplate The URI template of the resource template to remove
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> removeResourceTemplate(String uriTemplate) {

		if (this.serverCapabilities.resources() == null) {
			return Mono.error(new IllegalStateException(
					"Server must be configured with resource capabilities to allow removing resource templates"));
		}

		return Mono.defer(() -> {
			McpStatelessServerFeatures.AsyncResourceTemplateSpecification removed = this.resourceTemplates
				.remove(uriTemplate);
			if (removed != null) {
				logger.debug("Removed resource template: {}", uriTemplate);
			}
			else {
				logger.warn("Failed to remove a resource template with URI '{}' (not found)", uriTemplate);
			}
			return Mono.empty();
		});
	}

	private McpStatelessRequestHandler<McpSchema.ListResourcesResult> resourcesListRequestHandler() {
		return (ctx, params) -> {
			var resourceList = this.resources.values()
				.stream()
				.map(McpStatelessServerFeatures.AsyncResourceSpecification::resource)
				.toList();
			return Mono.just(McpSchema.ListResourcesResult.builder(resourceList).build());
		};
	}

	private McpStatelessRequestHandler<McpSchema.ListResourceTemplatesResult> resourceTemplateListRequestHandler() {
		return (exchange, params) -> {
			var resourceList = this.resourceTemplates.values()
				.stream()
				.map(AsyncResourceTemplateSpecification::resourceTemplate)
				.toList();
			return Mono.just(McpSchema.ListResourceTemplatesResult.builder(resourceList).build());
		};
	}

	private McpStatelessRequestHandler<McpSchema.ReadResourceResult> resourcesReadRequestHandler() {
		return (ctx, params) -> {
			McpSchema.ReadResourceRequest resourceRequest = jsonMapper.convertValue(params, new TypeRef<>() {
			});
			var resourceUri = resourceRequest.uri();

			// First try to find a static resource specification
			// Static resources have exact URIs
			return this.findResourceSpecification(resourceUri)
				.map(spec -> spec.readHandler().apply(ctx, resourceRequest))
				.orElseGet(() -> {
					// If not found, try to find a dynamic resource specification
					// Dynamic resources have URI templates
					return this.findResourceTemplateSpecification(resourceUri)
						.map(spec -> spec.readHandler().apply(ctx, resourceRequest))
						.orElseGet(() -> Mono.error(RESOURCE_NOT_FOUND.apply(resourceUri)));
				});

		};
	}

	private Optional<McpStatelessServerFeatures.AsyncResourceSpecification> findResourceSpecification(String uri) {
		var result = this.resources.values()
			.stream()
			.filter(spec -> this.uriTemplateManagerFactory.create(spec.resource().uri()).matches(uri))
			.findFirst();
		return result;
	}

	private Optional<McpStatelessServerFeatures.AsyncResourceTemplateSpecification> findResourceTemplateSpecification(
			String uri) {
		return this.resourceTemplates.values()
			.stream()
			.filter(spec -> this.uriTemplateManagerFactory.create(spec.resourceTemplate().uriTemplate()).matches(uri))
			.findFirst();
	}

	// ---------------------------------------
	// Prompt Management
	// ---------------------------------------

	/**
	 * Add a new prompt handler at runtime.
	 * @param promptSpecification The prompt handler to add
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> addPrompt(McpStatelessServerFeatures.AsyncPromptSpecification promptSpecification) {
		if (promptSpecification == null) {
			return Mono.error(new IllegalArgumentException("Prompt specification must not be null"));
		}
		if (this.serverCapabilities.prompts() == null) {
			return Mono.error(new IllegalStateException("Server must be configured with prompt capabilities"));
		}

		return Mono.defer(() -> {
			var previous = this.prompts.put(promptSpecification.prompt().name(), promptSpecification);
			if (previous != null) {
				logger.warn("Replace existing Prompt with name '{}'", promptSpecification.prompt().name());
			}
			else {
				logger.debug("Added prompt handler: {}", promptSpecification.prompt().name());
			}

			return Mono.empty();
		});
	}

	/**
	 * List all registered prompts.
	 * @return A Flux stream of all registered prompts
	 */
	public Flux<McpSchema.Prompt> listPrompts() {
		return Flux.fromIterable(this.prompts.values())
			.map(McpStatelessServerFeatures.AsyncPromptSpecification::prompt);
	}

	/**
	 * Remove a prompt handler at runtime.
	 * @param promptName The name of the prompt handler to remove
	 * @return Mono that completes when clients have been notified of the change
	 */
	public Mono<Void> removePrompt(String promptName) {
		if (promptName == null) {
			return Mono.error(new IllegalArgumentException("Prompt name must not be null"));
		}
		if (this.serverCapabilities.prompts() == null) {
			return Mono.error(new IllegalStateException("Server must be configured with prompt capabilities"));
		}

		return Mono.defer(() -> {
			McpStatelessServerFeatures.AsyncPromptSpecification removed = this.prompts.remove(promptName);

			if (removed != null) {
				logger.debug("Removed prompt handler: {}", promptName);
				return Mono.empty();
			}
			else {
				logger.warn("Failed to remove a prompt with name '{}' (not found)", promptName);
			}

			return Mono.empty();
		});
	}

	private McpStatelessRequestHandler<McpSchema.ListPromptsResult> promptsListRequestHandler() {
		return (ctx, params) -> {
			// TODO: Implement pagination
			// McpSchema.PaginatedRequest request = objectMapper.convertValue(params,
			// new TypeReference<McpSchema.PaginatedRequest>() {
			// });

			var promptList = this.prompts.values()
				.stream()
				.map(McpStatelessServerFeatures.AsyncPromptSpecification::prompt)
				.toList();

			return Mono.just(McpSchema.ListPromptsResult.builder(promptList).build());
		};
	}

	private McpStatelessRequestHandler<McpSchema.GetPromptResult> promptsGetRequestHandler() {
		return (ctx, params) -> {
			McpSchema.GetPromptRequest promptRequest = jsonMapper.convertValue(params,
					new TypeRef<McpSchema.GetPromptRequest>() {
					});

			// Implement prompt retrieval logic here
			McpStatelessServerFeatures.AsyncPromptSpecification specification = this.prompts.get(promptRequest.name());
			if (specification == null) {
				return Mono.error(McpError.builder(ErrorCodes.INVALID_PARAMS)
					.message("Invalid prompt name")
					.data("Prompt not found: " + promptRequest.name())
					.build());
			}

			return specification.promptHandler().apply(ctx, promptRequest);
		};
	}

	private static final Mono<McpSchema.CompleteResult> EMPTY_COMPLETION_RESULT = Mono
		.just(new McpSchema.CompleteResult(new CompleteCompletion(List.of(), 0, false)));

	private McpStatelessRequestHandler<McpSchema.CompleteResult> completionCompleteRequestHandler() {
		return (ctx, params) -> {
			McpSchema.CompleteRequest request = jsonMapper.convertValue(params, new TypeRef<>() {
			});

			if (request.ref() == null) {
				return Mono.error(
						McpError.builder(ErrorCodes.INVALID_PARAMS).message("Completion ref must not be null").build());
			}

			if (request.ref().type() == null) {
				return Mono.error(McpError.builder(ErrorCodes.INVALID_PARAMS)
					.message("Completion ref type must not be null")
					.build());
			}

			String type = request.ref().type();

			String argumentName = request.argument().name();

			// Check if valid a Prompt exists for this completion request
			if (type.equals(PromptReference.TYPE)
					&& request.ref() instanceof McpSchema.PromptReference promptReference) {

				McpStatelessServerFeatures.AsyncPromptSpecification promptSpec = this.prompts
					.get(promptReference.name());
				if (promptSpec == null) {
					return Mono.error(McpError.builder(ErrorCodes.INVALID_PARAMS)
						.message("Prompt not found: " + promptReference.name())
						.build());
				}
				List<McpSchema.PromptArgument> arguments = promptSpec.prompt().arguments();
				if (arguments == null
						|| !arguments.stream().filter(arg -> arg.name().equals(argumentName)).findFirst().isPresent()) {

					logger.warn("Argument not found: {} in prompt: {}", argumentName, promptReference.name());

					return EMPTY_COMPLETION_RESULT;
				}
			}

			// Check if valid Resource or ResourceTemplate exists for this completion
			// request
			if (type.equals(ResourceReference.TYPE)
					&& request.ref() instanceof McpSchema.ResourceReference resourceReference) {

				var uriTemplateManager = uriTemplateManagerFactory.create(resourceReference.uri());

				if (!uriTemplateManager.isUriTemplate(resourceReference.uri())) {
					// Attempting to autocomplete a fixed resource URI is not an error in
					// the spec (but probably should be).
					return EMPTY_COMPLETION_RESULT;
				}

				McpStatelessServerFeatures.AsyncResourceSpecification resourceSpec = this
					.findResourceSpecification(resourceReference.uri())
					.orElse(null);

				if (resourceSpec != null) {
					if (!uriTemplateManagerFactory.create(resourceSpec.resource().uri())
						.getVariableNames()
						.contains(argumentName)) {

						return Mono.error(McpError.builder(ErrorCodes.INVALID_PARAMS)
							.message("Argument not found: " + argumentName + " in resource: " + resourceReference.uri())
							.build());
					}
				}
				else {
					var templateSpec = this.findResourceTemplateSpecification(resourceReference.uri()).orElse(null);
					if (templateSpec != null) {

						if (!uriTemplateManagerFactory.create(templateSpec.resourceTemplate().uriTemplate())
							.getVariableNames()
							.contains(argumentName)) {

							return Mono.error(McpError.builder(ErrorCodes.INVALID_PARAMS)
								.message("Argument not found: " + argumentName + " in resource template: "
										+ resourceReference.uri())
								.build());
						}
					}
					else {
						return Mono.error(RESOURCE_NOT_FOUND.apply(resourceReference.uri()));
					}
				}
			}

			McpStatelessServerFeatures.AsyncCompletionSpecification specification = this.completions.get(request.ref());

			if (specification == null) {
				return EMPTY_COMPLETION_RESULT;
			}

			return specification.completionHandler().apply(ctx, request);
		};
	}

	/**
	 * This method is package-private and used for test only. Should not be called by user
	 * code.
	 * @param protocolVersions the Client supported protocol versions.
	 */
	void setProtocolVersions(List<String> protocolVersions) {
		this.protocolVersions = protocolVersions;
	}

}
