public static (string filename, string source) Emit(UnionTypeSchema unionTypeSchema,
Action <Diagnostic> reportDiagnostic, CancellationToken cancellationToken)
{
var builder = new CSharpBuilder();
builder.WriteUsings("System", "System.Threading.Tasks");
using (builder.Namespace(unionTypeSchema.Namespace))
{
using (builder.PublicStaticPartialClass("MatchExtension"))
{
GenerateMatchMethod(builder, unionTypeSchema, "T");
builder.WriteLine("");
GenerateMatchMethod(builder, unionTypeSchema, "Task<T>");
builder.WriteLine("");
var thisParameter = ThisParameter(unionTypeSchema, $"Task<{unionTypeSchema.TypeName}>");
WriteMatchSignature(builder, unionTypeSchema, thisParameter, "Task<T>", "T", "public static async");
var caseParameters = unionTypeSchema.Cases.Select(c => c.ParameterName).ToSeparatedString();
builder.WriteLine($"(await {thisParameter.Name}.ConfigureAwait(false)).Match({caseParameters});");
builder.WriteLine("");
var thisParameter1 = ThisParameter(unionTypeSchema, $"Task<{unionTypeSchema.TypeName}>");
WriteMatchSignature(builder, unionTypeSchema, thisParameter1, "Task<T>", handlerReturnType: "Task<T>", "public static async");
builder.WriteLine($"await (await {thisParameter1.Name}.ConfigureAwait(false)).Match({caseParameters}).ConfigureAwait(false);");
}
}
return($"{unionTypeSchema.TypeName}MatchExtension.g.cs", builder.ToString());
}
static void GenerateMatchMethod(CSharpBuilder builder, UnionTypeSchema unionTypeSchema, string t)
{
var thisParameterType = unionTypeSchema.TypeName;
var thisParameter = ThisParameter(unionTypeSchema, thisParameterType);
var thisParameterName = thisParameter.Name;
WriteMatchSignature(builder, unionTypeSchema, thisParameter, t);
builder.WriteLine($"{thisParameterName} switch");
using (builder.ScopeWithSemicolon())
{
var caseIndex = 0;
foreach (var c in unionTypeSchema.Cases)
{
caseIndex++;
builder.WriteLine($"{c.FullTypeName} case{caseIndex} => {c.ParameterName}(case{caseIndex}),");
}
builder.WriteLine(
$"_ => throw new ArgumentException($\"Unknown type derived from {unionTypeSchema.TypeName}: {{{thisParameterName}.GetType().Name}}\")");
}
}
static Parameter ThisParameter(UnionTypeSchema unionTypeSchema, string thisParameterType) => new($"this {thisParameterType}", unionTypeSchema.TypeName.ToParameterName());