feat(arguments): enum argument (#354)

Author: sawa-ko

src/arguments/CoreEnum.ts

@@ -0,0 +1,23 @@
+import type { PieceContext } from '@sapphire/pieces';
+import { resolveEnum } from '../lib/resolvers';
+import { Argument } from '../lib/structures/Argument';
+
+export class CoreArgument extends Argument<string> {
+	public constructor(context: PieceContext) {
+		super(context, { name: 'enum' });
+	}
+
+	public run(
+		parameter: string,
+		context: { readonly enum?: string[]; readonly caseInsensitive?: boolean } & Argument.Context
+	): Argument.Result<string> {
+		const resolved = resolveEnum(parameter, { enum: context.enum, caseInsensitive: context.caseInsensitive });
+		if (resolved.success) return this.ok(resolved.value);
+		return this.error({
+			parameter,
+			identifier: resolved.error,
+			message: `The argument must have one of the following values: ${context.enum?.join(', ')}`,
+			context
+		});
+	}
+}

src/lib/errors/Identifiers.ts

@@ -37,6 +37,8 @@ export const enum Identifiers {
 	ArgumentStringTooLong = 'stringTooLong',
 	ArgumentStringTooShort = 'stringTooShort',
 	ArgumentUserError = 'userError',
+	ArgumentEnumEmptyError = 'enumEmptyError',
+	ArgumentEnumError = 'enumError',
 
 	CommandDisabled = 'commandDisabled',
 

src/lib/parsers/Args.ts

@@ -709,6 +709,7 @@ export interface ArgType {
 	string: string;
 	url: URL;
 	user: User;
+	enum: string;
 }
 
 export interface ArgOptions extends Omit<Argument.Context, 'message' | 'command'> {}

src/lib/resolvers/enum.ts

@@ -0,0 +1,21 @@
+import { Identifiers } from '../errors/Identifiers';
+import { err, ok, Result } from '../parsers/Result';
+
+export function resolveEnum(
+	parameter: string,
+	options?: { enum?: string[]; caseInsensitive?: boolean }
+): Result<string, Identifiers.ArgumentEnumEmptyError | Identifiers.ArgumentEnumError> {
+	if (!options?.enum?.length) {
+		return err(Identifiers.ArgumentEnumEmptyError);
+	}
+
+	if (!options.caseInsensitive && !options.enum.includes(parameter)) {
+		return err(Identifiers.ArgumentEnumError);
+	}
+
+	if (options.caseInsensitive && !options.enum.some((v) => v.toLowerCase() === parameter.toLowerCase())) {
+		return err(Identifiers.ArgumentEnumError);
+	}
+
+	return ok(parameter);
+}

src/lib/resolvers/index.ts

@@ -22,3 +22,4 @@ export * from './partialDMChannel';
 export * from './role';
 export * from './string';
 export * from './user';
+export * from './enum';