/// <summary>
/// Gets or creates the <see cref="CommandGrammar"/> corresponding to the <see cref="GlobalState"/>
/// </summary>
public static CommandGrammar From(GlobalState globals)
{
// if this is same set of commands as the default set, then just return the default grammar
if (globals.Commands == GlobalState.Default.Commands)
{
return(GetDefaultCommandGrammar());
}
CommandGrammar grammar = null;
bool foundInCache = false;
// if the globals has a cache, look in the cache
if (globals.Cache != null)
{
foundInCache = globals.Cache.TryGetValue <CommandGrammar>(out grammar);
}
// if we still don't have a grammar check the recently created grammar
// or create a new one
if (grammar == null)
{
var recent = s_recentGrammar;
if (recent != null && recent.Commands == globals.Commands)
{
grammar = recent.Grammar;
}
else
{
grammar = Create(globals);
// remember this grammar for next time
var newRecent = new RecentGrammar(globals.Commands, grammar);
Interlocked.CompareExchange(ref s_recentGrammar, newRecent, recent);
}
}
// if the grammar did not come from the cache, put it into the cache if there is one.
if (globals.Cache != null && !foundInCache)
{
grammar = globals.Cache.GetOrCreate <CommandGrammar>(() => grammar);
}
return(grammar);
}
public RecentGrammar(IReadOnlyList <CommandSymbol> commands, CommandGrammar grammar)
{
this.Commands = commands;
this.Grammar = grammar;
}
