add Platform.Adapter interface

src/platform-adapters/_base.ts

@@ -0,0 +1,14 @@
+// eslint-disable-next-line @typescript-eslint/no-namespace
+export namespace Platform {
+	export type Adapter = {
+		readonly env: { readonly get: (_: string) => string | undefined };
+		readonly os: { readonly homedir?: () => string; readonly tmpdir?: () => string };
+		readonly path: {
+			readonly join: (..._: readonly string[]) => string;
+			readonly normalize: (_: string) => string;
+		};
+		readonly process: {
+			readonly platform: string;
+		};
+	};
+}

src/platform-adapters/browser.ts

@@ -0,0 +1 @@
+'use strict';

src/platform-adapters/deno.deno.ts

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+// spell-checker:ignore Deno
+
+// eslint-disable-next-line @typescript-eslint/triple-slash-reference
+/// <reference path="../types/deno.d.ts"/>
+
+// eslint-disable-next-line @typescript-eslint/ban-ts-comment
+// @ts-ignore
+import * as path from 'https://deno.land/std@0.81.0/path/mod.ts';
+
+// eslint-disable-next-line @typescript-eslint/ban-ts-comment
+// @ts-ignore
+import { Platform } from './_base.ts';
+
+export const adapter: Platform.Adapter = {
+	env: { get: Deno.env.get },
+	// Deno (as of v1.6) has no built-in implementation for homedir() or tmpdir()
+	os: {}, // * module is tolerant of missing homedir()/tmpdir() functions
+	path,
+	process: { platform: Deno.build.os },
+};

src/platform-adapters/node.ts

@@ -0,0 +1,15 @@
+import * as os from 'os';
+import * as path from 'path';
+
+import { Platform } from './_base';
+
+export const adapter: Platform.Adapter = {
+	env: {
+		get: (s) => {
+			return process.env[s];
+		},
+	},
+	os,
+	path,
+	process,
+};