/// <summary>
/// Gets an instance of <see cref="Town"/> from the <paramref name="railwaySystem"/>, or creates a new one if not exists.
/// </summary>
/// <param name="railwaySystem">An instance of <see cref="RailwaySystem"/>.</param>
/// <param name="townName">The name of the town to search.</param>
/// <returns>An instance of <see cref="Town"/>.</returns>
private Town GetOrAddTownByName(RailwaySystem railwaySystem, string townName)
{
if (railwaySystem.HasTown(townName))
{
return(railwaySystem.GetTownByName(townName) as Town);
}
var town = new Town(townName);
railwaySystem.AddTown(town);
return(town);
}
/// <summary>
/// Builds a new instance of <see cref="IRailwaySystem"/> based on a comma-separated route set.
/// </summary>
/// <param name="routeSet">A comma-separated <see cref="string"/> with the routes and their respective distances.</param>
/// <remarks>
/// The expected format is a comma separated of values as {origin town name}{destination town name}{total distance}.
/// For example: AB5,BC4,CD8,DC8,DE6,AD5,CE2,EB3,AE7.
/// </remarks>
/// <returns>A new instance of <see cref="IRailwaySystem"/>.</returns>
public IRailwaySystem Build(string routeSet)
{
if (string.IsNullOrWhiteSpace(routeSet))
{
throw new ArgumentNullException(nameof(routeSet));
}
var railwaySystem = new RailwaySystem();
foreach (var routeDefinition in routeSet.Split(','))
{
if (!CommaSeparatedRouteSetRegex.Match(routeDefinition).Success)
{
throw new ArgumentException($"Route {routeDefinition} is not in a valid format.", nameof(routeSet));
}
var routeParts = CommaSeparatedRouteSetRegex.Match(routeDefinition).Groups;
var origin = GetOrAddTownByName(railwaySystem, routeParts["origin"].Value);
var destination = GetOrAddTownByName(railwaySystem, routeParts["destination"].Value);
var distance = Convert.ToInt32(routeParts["distance"].Value);
var route = new Route(origin, destination, distance);
origin.AddRoute(route);
}
return(railwaySystem);
}