feat(types): add public interface

types.ts

@@ -0,0 +1,71 @@
+// Copyright 2023-latest Tomoki Miyauchi. All rights reserved. MIT license.
+// This module is browser compatible.
+
+/** Validator API. */
+export interface Validator<In = unknown> {
+  /** Validates the input and yield validation errors if exists. */
+  validate: (input: In) => Iterable<ValidationError>;
+}
+
+/** Assert API for validated data type. */
+export interface Assert<In = unknown, Out extends In = In> {
+  [Assert.symbol]: Out;
+}
+
+export class Assert {
+  static readonly symbol = Symbol("assert.type");
+}
+
+export interface AssertiveValidator<In = unknown, Out extends In = In>
+  extends Assert<In, Out>, Validator<In> {}
+
+/** Validation error options. */
+export interface ValidationErrorOptions extends ErrorOptions {
+  /** Path to instance. */
+  instancePath?: string[];
+}
+
+/** Validation error. */
+export class ValidationError extends Error {
+  /** The path to a part of the instance. */
+  instancePath: string[];
+
+  override name = "ValidationError";
+
+  constructor(
+    message?: string,
+    options: ValidationErrorOptions = {},
+  ) {
+    super(message, options);
+    this.instancePath = options.instancePath ?? [];
+  }
+}
+
+/** Result of OK API. */
+export class Ok<T> {
+  /** Node type. */
+  type: "ok" = "ok";
+
+  /** Actual data. */
+  data: T;
+
+  constructor(data: T) {
+    this.data = data;
+  }
+}
+
+/** Result of Error API. */
+export class Err {
+  /** Node type. */
+  type: "error" = "error";
+
+  /** Actual errors. */
+  errors: readonly ValidationError[];
+
+  constructor(errors: readonly ValidationError[]) {
+    this.errors = errors;
+  }
+}
+
+/** Represent {@link Ok} or {@link Err}.  */
+export type Result<T> = Ok<T> | Err;