/// <summary>
/// Executes the command.
/// </summary>
/// <param name="context">The context of the command.</param>
/// <param name="input">The command string.</param>
/// <param name="services">The service to be used in the command's dependency injection.</param>
/// <param name="multiMatchHandling">The handling mode when multiple command matches are found.</param>
/// <returns>
/// A task that represents the asynchronous execution operation. The task result contains the result of the
/// command execution.
/// </returns>
public async Task <IResult> ExecuteAsync(ICommandContext context, string input, IServiceProvider services, MultiMatchHandling multiMatchHandling = MultiMatchHandling.Exception)
{
services = services ?? EmptyServiceProvider.Instance;
var searchResult = Search(input);
if (!searchResult.IsSuccess)
{
return(searchResult);
}
var commands = searchResult.Commands;
var preconditionResults = new Dictionary <CommandMatch, PreconditionResult>();
foreach (var match in commands)
{
preconditionResults[match] = await match.Command.CheckPreconditionsAsync(context, services).ConfigureAwait(false);
}
var successfulPreconditions = preconditionResults
.Where(x => x.Value.IsSuccess)
.ToArray();
if (successfulPreconditions.Length == 0)
{
//All preconditions failed, return the one from the highest priority command
var bestCandidate = preconditionResults
.OrderByDescending(x => x.Key.Command.Priority)
.FirstOrDefault(x => !x.Value.IsSuccess);
return(bestCandidate.Value);
}
//If we get this far, at least one precondition was successful.
var parseResultsDict = new Dictionary <CommandMatch, ParseResult>();
foreach (var pair in successfulPreconditions)
{
var parseResult = await pair.Key.ParseAsync(context, searchResult, pair.Value, services).ConfigureAwait(false);
if (parseResult.Error == CommandError.MultipleMatches)
{
IReadOnlyList <TypeReaderValue> argList, paramList;
switch (multiMatchHandling)
{
case MultiMatchHandling.Best:
argList = parseResult.ArgValues.Select(x => x.Values.OrderByDescending(y => y.Score).First()).ToImmutableArray();
paramList = parseResult.ParamValues.Select(x => x.Values.OrderByDescending(y => y.Score).First()).ToImmutableArray();
parseResult = ParseResult.FromSuccess(argList, paramList);
break;
}
}
parseResultsDict[pair.Key] = parseResult;
}
// Calculates the 'score' of a command given a parse result
float CalculateScore(CommandMatch match, ParseResult parseResult)
{
float argValuesScore = 0, paramValuesScore = 0;
if (match.Command.Parameters.Count > 0)
{
var argValuesSum = parseResult.ArgValues?.Sum(x => x.Values.OrderByDescending(y => y.Score).FirstOrDefault().Score) ?? 0;
var paramValuesSum = parseResult.ParamValues?.Sum(x => x.Values.OrderByDescending(y => y.Score).FirstOrDefault().Score) ?? 0;
argValuesScore = argValuesSum / match.Command.Parameters.Count;
paramValuesScore = paramValuesSum / match.Command.Parameters.Count;
}
var totalArgsScore = (argValuesScore + paramValuesScore) / 2;
return(match.Command.Priority + totalArgsScore * 0.99f);
}
//Order the parse results by their score so that we choose the most likely result to execute
var parseResults = parseResultsDict
.OrderByDescending(x => CalculateScore(x.Key, x.Value));
var successfulParses = parseResults
.Where(x => x.Value.IsSuccess)
.ToArray();
if (successfulParses.Length == 0)
{
//All parses failed, return the one from the highest priority command, using score as a tie breaker
var bestMatch = parseResults
.FirstOrDefault(x => !x.Value.IsSuccess);
return(bestMatch.Value);
}
//If we get this far, at least one parse was successful. Execute the most likely overload.
var chosenOverload = successfulParses[0];
return(await chosenOverload.Key.ExecuteAsync(context, chosenOverload.Value, services).ConfigureAwait(false));
}
