Libation/Source/ApplicationServices/SearchEngineCommands.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using DataLayer;
using LibationSearchEngine;

namespace ApplicationServices
{
	public static class SearchEngineCommands
	{
		#region Search
		public static SearchResultSet Search(string searchString) => performSafeQuery(e =>
			e.Search(searchString)
		);

		private static T performSafeQuery<T>(Func<SearchEngine, T> func)
		{
			var engine = new SearchEngine();
			try
			{
				return func(engine);
			}
			catch (FileNotFoundException)
			{
				fullReIndex(engine);
				return func(engine);
			}
		}
		#endregion

		public static event EventHandler SearchEngineUpdated;

		#region Update
		private static bool isUpdating;

		public static void UpdateBooks(IEnumerable<LibraryBook> books)
		{
			// Semi-arbitrary. At some point it's more worth it to do a full re-index than to do one offs.
			// I did not benchmark before choosing the number here
			if (books.Count() > 15)
				FullReIndex();
			else
			{
				foreach (var book in books)
					UpdateUserDefinedItems(book);
			}
		}

		public static void FullReIndex() => performSafeCommand(fullReIndex);
		public static void FullReIndex(List<LibraryBook> libraryBooks)
			=> performSafeCommand(se => fullReIndex(se, libraryBooks.WithoutParents()));

		internal static void UpdateUserDefinedItems(LibraryBook book) => performSafeCommand(e =>
			{
				e.UpdateLiberatedStatus(book);
				e.UpdateTags(book.Book.AudibleProductId, book.Book.UserDefinedItem.Tags);
				e.UpdateUserRatings(book);
			}
		);

		private static void performSafeCommand(Action<SearchEngine> action)
		{
			try
			{
				update(action);
			}
			catch (FileNotFoundException)
			{
				fullReIndex(new SearchEngine());
				update(action);
			}
		}

		private static void update(Action<SearchEngine> action)
		{
			if (action is null)
				return;

			// support nesting incl recursion
			var prevIsUpdating = isUpdating;
			try
			{
				isUpdating = true;

				action(new SearchEngine());
				if (!prevIsUpdating)
					SearchEngineUpdated?.Invoke(null, null);
			}
			finally
			{
				isUpdating = prevIsUpdating;
			}
		}

		private static void fullReIndex(SearchEngine engine)
		{
			var library = DbContexts.GetLibrary_Flat_NoTracking();
			fullReIndex(engine, library);
		}

		private static void fullReIndex(SearchEngine engine, IEnumerable<LibraryBook> libraryBooks)
		=> engine.CreateNewIndex(libraryBooks);
		#endregion
	}
}