/*
 * Copyright (C) 2025 Mcp-Vala Project
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Author: Mcp-Vala Project
 */


/**
 * Prompt manager for MCP protocol.
 *
 * This class manages prompt templates and handles prompt-related
 * JSON-RPC method calls.
 */
namespace Mcp.Prompts {
    /**
     * Prompt manager implementation.
     */
    public class Manager : GLib.Object {
        private HashTable<string, Template> templates;
        
        /**
         * Signal emitted when the prompt list changes.
         */
        public signal void list_changed ();
        
        /**
         * Creates a new Manager.
         */
        public Manager () {
            templates = new HashTable<string, Template> (str_hash, str_equal);
        }
        
        /**
         * Registers a prompt template.
         *
         * @param name The prompt name
         * @param template The template implementation
         * @throws Error If registration fails
         */
        public void register_template (string name, Template template) throws Error {
            if (name == null || name.strip () == "") {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("Prompt name cannot be empty or null. Please provide a valid name for the prompt template.");
            }
            
            if (templates.contains (name)) {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("Prompt '%s' is already registered. Use a different name or unregister the existing prompt first.".printf (name));
            }
            
            templates.insert (name, template);
            list_changed ();
        }
        
        /**
         * Unregisters a prompt template.
         *
         * @param name The prompt name to unregister
         * @throws Error If unregistration fails
         */
        public void unregister_template (string name) throws Error {
            if (!templates.contains (name)) {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("Prompt '%s' not found. Cannot unregister a prompt that doesn't exist. Check the name and try again.".printf (name));
            }
            
            templates.remove (name);
            list_changed ();
        }
        
        /**
         * Gets a registered prompt template.
         *
         * @param name The prompt name
         * @return The template or null if not found
         */
        public Template? get_template (string name) {
            return templates.lookup (name);
        }
        
        /**
         * Gets all registered prompt templates.
         *
         * @return A hash table of all templates
         */
        public HashTable<string, Template> get_templates () {
            return templates;
        }
        
        /**
         * Lists all registered prompt names.
         *
         * @return A list of prompt names
         */
        public Gee.ArrayList<string> list_prompt_names () {
            var names = new Gee.ArrayList<string> ();
            foreach (var name in templates.get_keys ()) {
                names.add (name);
            }
            return names;
        }
        
        /**
         * Checks if a prompt is registered.
         *
         * @param name The prompt name
         * @return True if the prompt is registered
         */
        public bool has_prompt (string name) {
            return templates.contains (name);
        }
        
        /**
         * Handles the prompts/list JSON-RPC method.
         *
         * @param params The method parameters
         * @return The response result
         * @throws Error If handling fails
         */
        public async Variant handle_list (Variant @params) throws Error {
            // Extract cursor parameter if present
            string? cursor = null;
            if (@params.lookup_value ("cursor", null) != null) {
                cursor = @params.lookup_value ("cursor", VariantType.STRING).get_string ();
            }
            
            // Get all prompt definitions from all templates
            var all_prompts = new Gee.ArrayList<Mcp.Prompts.Types.PromptDefinition> ();
            foreach (var name in templates.get_keys ()) {
                var template = templates.lookup (name);
                
                try {
                    var definition = template.get_definition ();
                    all_prompts.add (definition);
                } catch (Error e) {
                    // Continue with other templates
                }
            }
            
            // Sort prompts by name for consistent pagination
            all_prompts.sort ((a, b) => {
                return strcmp (a.name, b.name);
            });
            
            // Pagination settings
            const int PAGE_SIZE = 10;
            int start_index = 0;
            
            // Parse cursor to determine starting position
            if (cursor != null) {
                // Simple cursor implementation: cursor is the page number as a string
                // Default to 0 if parsing fails
                start_index = int.parse (cursor) * PAGE_SIZE;
                if (start_index < 0) {
                    start_index = 0;
                }
            }
            
            // Calculate the end index for this page
            int end_index = int.min (start_index + PAGE_SIZE, all_prompts.size);
            
            // Get the prompts for this page
            var page_prompts = new Gee.ArrayList<Mcp.Prompts.Types.PromptDefinition> ();
            for (int i = start_index; i < end_index; i++) {
                page_prompts.add (all_prompts[i]);
            }
            
            // Build response as Variant using utility functions
            var result_builder = Mcp.Types.VariantUtils.new_dict_builder ();
            
            // Serialize prompts array
            var prompts_builder = Mcp.Types.VariantUtils.new_dict_array_builder ();
            foreach (var prompt in page_prompts) {
                prompts_builder.add_value (prompt.to_variant ());
            }
            result_builder.add ("{sv}", "prompts", prompts_builder.end ());
            
            // Add nextCursor if there are more prompts
            if (end_index < all_prompts.size) {
                // Next cursor is the next page number
                int next_page = start_index / PAGE_SIZE + 1;
                result_builder.add ("{sv}", "nextCursor", new Variant.string (next_page.to_string ()));
            }
            
            return result_builder.end ();
        }
        
        /**
         * Handles the prompts/get JSON-RPC method.
         *
         * @param params The method parameters
         * @return The response result
         * @throws Error If handling fails
         */
        public async Variant handle_get (Variant @params) throws Error {
            if (@params.lookup_value ("name", null) == null) {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("Missing required 'name' parameter. The prompts/get method requires a prompt name to retrieve.");
            }
            
            string name = @params.lookup_value ("name", VariantType.STRING).get_string ();
            
            if (name.strip () == "") {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("The 'name' parameter cannot be empty. Please provide a valid prompt name.");
            }
            
            Variant? arguments = null;
            if (@params.lookup_value ("arguments", null) != null) {
                arguments = @params.lookup_value ("arguments", VariantType.VARDICT);
            }
            
            Template? template = templates.lookup (name);
            if (template == null) {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("Prompt '%s' not found. Verify the prompt name is correct and that it has been registered.".printf (name));
            }
            
            try {
                var result = yield template.get_prompt (arguments);
                return result.to_variant ();
            } catch (Error e) {
                throw new Mcp.Core.McpError.INTERNAL_ERROR ("Failed to generate prompt '%s': %s".printf (name, e.message));
            }
        }
        
        /**
         * Sends a notification that the prompt list has changed.
         *
         * This method is called automatically when templates are registered
         * or unregistered, but can also be called manually.
         */
        public void notify_list_changed () {
            list_changed ();
        }
        
        /**
         * Validates a prompt template before registration.
         *
         * @param template The template to validate
         * @throws Error If validation fails
         */
        private void validate_template (Template template) throws Error {
            if (template == null) {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("Template cannot be null. Please provide a valid Template instance.");
            }
            
            try {
                var definition = template.get_definition ();
                if (definition == null) {
                    throw new Mcp.Core.McpError.INVALID_PARAMS ("Template definition cannot be null. The template must return a valid PromptDefinition.");
                }
                
                if (definition.name == null || definition.name.strip () == "") {
                    throw new Mcp.Core.McpError.INVALID_PARAMS ("Template name cannot be empty or null. Please provide a valid name for the prompt template.");
                }
                
                // Validate arguments
                if (definition.arguments != null) {
                    var argument_names = new Gee.HashSet<string> ();
                    foreach (var arg in definition.arguments) {
                        if (arg.name == null || arg.name.strip () == "") {
                            throw new Mcp.Core.McpError.INVALID_PARAMS ("Argument name cannot be empty or null. All arguments must have valid names.");
                        }
                        
                        if (argument_names.contains (arg.name)) {
                            throw new Mcp.Core.McpError.INVALID_PARAMS ("Duplicate argument name '%s'. Each argument must have a unique name.".printf (arg.name));
                        }
                        
                        argument_names.add (arg.name);
                    }
                }
            } catch (Error e) {
                throw new Mcp.Core.McpError.INVALID_PARAMS ("Template validation failed: %s. Please check the template implementation and fix any issues.".printf (e.message));
            }
        }
    }
}