/*
 * QUANTCONNECT.COM - Democratizing Finance, Empowering Individuals.
 * Lean Algorithmic Trading Engine v2.0. Copyright 2014 QuantConnect Corporation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
*/

using System;
using System.Linq;
using System.Text.RegularExpressions;
using Python.Runtime;
using QuantConnect.Util;

namespace QuantConnect.Exceptions
{
    /// <summary>
    /// Interprets Python ModuleNotFoundError exceptions
    /// </summary>
    public class ModuleNotFoundPythonExceptionInterpreter : PythonExceptionInterpreter
    {
        private static readonly Regex _camelCasedNameRegex = new Regex(@"^[A-Z][a-zA-Z0-9]*(\.[A-Z][a-zA-Z0-9]*)*$", RegexOptions.Compiled);

        /// <summary>
        /// Determines the order that an instance of this class should be called
        /// </summary>
        public override int Order => 0;

        /// <summary>
        /// Determines if this interpreter should be applied to the specified exception.
        /// </summary>
        /// <param name="exception">The exception to check</param>
        /// <returns>True if the exception can be interpreted, false otherwise</returns>
        public override bool CanInterpret(Exception exception)
        {
            var pythonException = exception as PythonException;
            if (pythonException == null)
            {
                return false;
            }

            using (Py.GIL())
            {
                return base.CanInterpret(exception) &&
                    pythonException.Type.Name.Equals("ModuleNotFoundError", StringComparison.InvariantCultureIgnoreCase);
            }
        }

        /// <summary>
        /// Interprets the specified exception into a new exception
        /// </summary>
        /// <param name="exception">The exception to be interpreted</param>
        /// <param name="innerInterpreter">An interpreter that should be applied to the inner exception.</param>
        /// <returns>The interpreted exception</returns>
        public override Exception Interpret(Exception exception, IExceptionInterpreter innerInterpreter)
        {
            var pe = (PythonException)exception;

            var moduleName = pe.Message.GetStringBetweenChars('\'', '\'');
            var message = Messages.ModuleNotFoundPythonExceptionInterpreter.ModuleNotFound(moduleName, IsCamelCased(moduleName));
            message += PythonUtil.PythonExceptionStackParser(pe.StackTrace);

            return new Exception(message, pe);
        }

        /// <summary>
        /// Determines whether the module name follows .NET namespace casing (e.g. "QuantConnect.Indicators"):
        /// every dot-separated segment starts with an uppercase letter and the name contains at least one
        /// lowercase letter, so all-uppercase Python packages like "PIL" are not treated as assemblies.
        /// </summary>
        private static bool IsCamelCased(string moduleName)
        {
            return _camelCasedNameRegex.IsMatch(moduleName) && moduleName.Any(char.IsLower);
        }
    }
}