using System;
using System.Collections.Generic;
using System.Text;

namespace WmData {

    /// <summary>
    /// The WmIntermediateObjectManager keeps a 
    /// collection of intermediate objects for both
    /// WmData and WmDirectData. It is aimed to
    /// overcome the drag that comes with the System.Reflection 
    /// namespace. By creating Intermediate objects, a speed gain 
    /// of approx. 80% is achieved. 
    /// </summary>
    public class WmIntermediateObjectManager {
        protected List<WmIntermediateObject> intermediateObjects;
        protected WmDataBaseCredentials databaseCredentials;

        public WmIntermediateObjectManager(WmDataBaseCredentials databaseCredentials){
            intermediateObjects = new List<WmIntermediateObject>();
            this.databaseCredentials = databaseCredentials;
        }

        /// <summary>
        /// Returns an intermediate object,
        /// if it does not exist than a threadsafe operation is carried out to create one.
        /// It always returns something safely.
        /// </summary>
        public WmIntermediateObject getIntermediateObject(Type objectType, bool createDatabaseTableIfNecessary) {
            WmIntermediateObject returnObject = null;
            string objectName = objectType.Name;

            using (TimedLock.Lock(intermediateObjects)){ 

                for (int i = 0; i < intermediateObjects.Count; i++) {
                    if (intermediateObjects[i].Name.Equals(objectName)) {
                        returnObject = intermediateObjects[i];
                        break; // stop searching, we've got 'm
                    }
                }

                if (returnObject == null) {
                     
                    // It may appear silly, but do search for one more time to be sure that no other thread has created the object int the meanwhile:
                    for (int i = 0; i < intermediateObjects.Count; i++) {
                        if (intermediateObjects[i].Name.Equals(objectName)) {
                            returnObject = intermediateObjects[i];
                            break; // stop searching, we've got 'm
                        }
                    }
                    if (returnObject == null) { // as a last resort: create the intermediate object
                        returnObject = new WmIntermediateObject(objectType, databaseCredentials);

                        // Only check database backend if we're managing such a thing.
                        if (databaseCredentials != null && createDatabaseTableIfNecessary) {
                            // also check if the object has a table, otherwise create it:
                            if (!WmDataBaseCreator.isTableExistent(returnObject.TableName, databaseCredentials)) {
                                // If not, make a glorious attempt to create the table
                                WmDataBaseCreator.createTable(objectType, databaseCredentials);
                            }
                        }

                        intermediateObjects.Add(returnObject);
                    }
                }
            }

            return returnObject;             
        }

        public WmIntermediateObject getExistingIntermediateObjectByTableName(string tableName) {
            WmIntermediateObject returnObject = null;
            
           using (TimedLock.Lock(intermediateObjects)){ 
                for (int i = 0; i < intermediateObjects.Count; i++) {
                    if (intermediateObjects[i].TableName.Equals(tableName)) {
                        returnObject = intermediateObjects[i];
                        break;
                    }
                }
            }

            return returnObject;
        }

    }
}