using Invercargill.DataStructures;
using InvercargillSql.Dialects;
using InvercargillSql.Orm.Projections;

namespace InvercargillSql.Orm {
    
    /**
     * Registry for entity mappers and projection definitions.
     *
     * TypeRegistry centralizes the registration and lookup of entity mappers
     * and projection definitions, allowing them to be shared across multiple
     * OrmSession instances if needed.
     *
     * Example usage:
     * {{{
     * var registry = new TypeRegistry();
     * registry.register_entity<User>(user_mapper);
     * registry.register_projection<UserSummary>(user_summary_definition);
     *
     * var session = new OrmSession(connection, dialect, registry);
     * }}}
     */
    public class TypeRegistry : Object, TypeProvider {
        private Dictionary<Type, EntityMapper> _mappers;
        private Dictionary<Type, ProjectionDefinition> _projection_registry;
        
        /**
         * Creates a new TypeRegistry instance.
         */
        public TypeRegistry() {
            _mappers = new Dictionary<Type, EntityMapper>();
            _projection_registry = new Dictionary<Type, ProjectionDefinition>();
        }
        
        /**
         * Registers an entity mapper for type T.
         *
         * @param mapper The entity mapper to register
         */
        public void register_entity<T>(EntityMapper<T> mapper) {
            _mappers.set(typeof(T), mapper);
        }
        
        /**
         * Registers an entity mapper with schema introspection for type T.
         *
         * This method introspects the database schema to discover primary keys,
         * auto-increment columns, and other metadata.
         *
         * @param table_name The database table name
         * @param connection The database connection for schema introspection
         * @param dialect The SQL dialect for schema introspection
         * @param build_action A function that configures the EntityMapperBuilder
         * @throws SqlError if schema introspection fails
         */
        public void register_with_schema<T>(
            string table_name,
            Connection connection,
            SqlDialect dialect,
            owned GLib.Func<EntityMapperBuilder<T>> build_action
        ) throws SqlError {
            var builder = new EntityMapperBuilder<T>();
            builder.table(table_name);
            build_action(builder);
            
            // Introspect schema and apply to mapper
            var schema = dialect.introspect_schema(connection, table_name);
            var mapper = builder.build_with_schema(schema);
            
            _mappers.set(typeof(T), mapper);
        }
        
        /**
         * Registers an entity mapper by Type.
         * 
         * This is a non-generic version for advanced scenarios.
         * 
         * @param type The entity type
         * @param mapper The entity mapper to register
         */
        public void register_entity_for_type(Type type, EntityMapper mapper) {
            _mappers.set(type, mapper);
        }
        
        /**
         * Gets the entity mapper for type T.
         *
         * @return The EntityMapper<T> for type T
         * @throws SqlError if no mapper is registered for type T
         */
        public EntityMapper<T> get_mapper<T>() throws SqlError {
            var mapper = _mappers.get_or_default(typeof(T)) as EntityMapper<T>;
            if (mapper == null) {
                throw new SqlError.GENERAL_ERROR("Entity type not registered: " + typeof(T).name());
            }
            return mapper;
        }
        
        /**
         * Gets the entity mapper for a type.
         * 
         * This is a non-generic version that returns the base EntityMapper type.
         *
         * @param type The entity type to look up
         * @return The EntityMapper for the type, or null if not registered
         */
        public EntityMapper? get_mapper_for_type(Type type) {
            return _mappers.get_or_default(type);
        }
        
        /**
         * Checks if an entity mapper is registered for type T.
         *
         * @return true if a mapper is registered, false otherwise
         */
        public bool has_mapper<T>() {
            return _mappers.has(typeof(T));
        }
        
        /**
         * Checks if an entity mapper is registered for a type.
         *
         * @param type The entity type to check
         * @return true if a mapper is registered, false otherwise
         */
        public bool has_mapper_for_type(Type type) {
            return _mappers.has(type);
        }
        
        /**
         * Registers a projection definition for type T.
         * 
         * @param definition The projection definition to register
         */
        public void register_projection<TProjection>(ProjectionDefinition definition) {
            _projection_registry.set(typeof(TProjection), definition);
        }
        
        /**
         * Registers a projection definition by Type.
         * 
         * This is a non-generic version for advanced scenarios.
         * 
         * @param type The projection type
         * @param definition The projection definition to register
         */
        public void register_projection_for_type(Type type, ProjectionDefinition definition) {
            _projection_registry.set(type, definition);
        }
        
        /**
         * Gets the projection definition for type T.
         * 
         * @return The ProjectionDefinition for the type, or null if not registered
         */
        public ProjectionDefinition? get_projection<TProjection>() {
            return _projection_registry.get_or_default(typeof(TProjection));
        }
        
        /**
         * Gets the projection definition by type.
         * 
         * @param type The projection type to look up
         * @return The ProjectionDefinition for the type, or null if not registered
         */
        public ProjectionDefinition? get_projection_for_type(Type type) {
            return _projection_registry.get_or_default(type);
        }
        
        /**
         * Checks if a projection is registered for type T.
         *
         * @return true if a projection is registered, false otherwise
         */
        public bool has_projection<T>() {
            return _projection_registry.has(typeof(T));
        }
        
        /**
         * Checks if a projection is registered for a type.
         *
         * @param type The projection type to check
         * @return true if a projection is registered, false otherwise
         */
        public bool has_projection_for_type(Type type) {
            return _projection_registry.has(type);
        }
    }
}