Effect Platform

Overview

@effect/platform provides cross-platform abstractions for:

• HTTP Client - Make HTTP requests
• HTTP Server - Build HTTP servers
• FileSystem - File operations
• KeyValueStore - Persistent storage
• Terminal - CLI interactions
• Worker - Background workers

HTTP Client

Installation

npm install @effect/platform
# For Node.js:
npm install @effect/platform-node
# For Bun:
npm install @effect/platform-bun

Basic Requests

import { HttpClient } from "@effect/platform";
import { NodeHttpClient } from "@effect/platform-node";
import { Effect } from "effect";

const program = Effect.gen(function* () {
  const client = yield* HttpClient.HttpClient;

  // GET request
  const response = yield* client.get("https://api.example.com/users");
  const data = yield* response.json;

  return data;
}).pipe(Effect.provide(NodeHttpClient.layer));

Request Configuration

const program = Effect.gen(function* () {
  const client = yield* HttpClient.HttpClient;

  // POST with body
  const response = yield* client.post("https://api.example.com/users", {
    body: HttpClientRequest.jsonBody({ name: "Alice", email: "alice@example.com" }),
  });

  // With headers
  const response = yield* client.get("https://api.example.com/protected", {
    headers: { Authorization: "Bearer token123" },
  });

  // With timeout
  const response = yield* client.get("https://api.example.com/slow").pipe(Effect.timeout("5 seconds"));
});

Response Handling

const program = Effect.gen(function* () {
  const client = yield* HttpClient.HttpClient;
  const response = yield* client.get("https://api.example.com/data");

  // Parse as JSON
  const json = yield* response.json;

  // Parse as text
  const text = yield* response.text;

  // Get status
  const status = response.status;

  // Get headers
  const contentType = response.headers["content-type"];
});

Schema Validation

import { HttpClient, HttpClientResponse } from "@effect/platform";
import { Schema } from "effect";

const User = Schema.Struct({
  id: Schema.Number,
  name: Schema.String,
  email: Schema.String,
});

const program = Effect.gen(function* () {
  const client = yield* HttpClient.HttpClient;
  const response = yield* client.get("https://api.example.com/users/1");

  // Validate response with schema
  const user = yield* HttpClientResponse.schemaBodyJson(User)(response);
  return user;
});

HTTP Server

Basic Server

import { HttpServer, HttpServerResponse } from "@effect/platform";
import { NodeHttpServer } from "@effect/platform-node";
import { Effect, Layer } from "effect";
import { createServer } from "node:http";

const app = HttpServer.router.empty.pipe(
  HttpServer.router.get("/", HttpServerResponse.text("Hello, World!")),
  HttpServer.router.get(
    "/users",
    HttpServerResponse.json([
      { id: 1, name: "Alice" },
      { id: 2, name: "Bob" },
    ]),
  ),
);

const ServerLive = NodeHttpServer.layer(createServer, { port: 3000 });

const program = Effect.gen(function* () {
  yield* Effect.log("Server starting on port 3000");
  yield* Effect.never; // Keep running
}).pipe(Effect.provide(HttpServer.router.Live(app)), Effect.provide(ServerLive));

Route Parameters

const app = HttpServer.router.empty.pipe(
  HttpServer.router.get(
    "/users/:id",
    Effect.gen(function* () {
      const params = yield* HttpServer.router.params;
      const id = params.id;
      return HttpServerResponse.json({ id, name: "User " + id });
    }),
  ),
);

Request Body

import { HttpServerRequest } from "@effect/platform";

const app = HttpServer.router.empty.pipe(
  HttpServer.router.post(
    "/users",
    Effect.gen(function* () {
      const request = yield* HttpServerRequest.HttpServerRequest;
      const body = yield* request.json;

      // Or with schema validation
      const validated = yield* HttpServerRequest.schemaBodyJson(CreateUser)(request);

      return HttpServerResponse.json({ created: true, user: validated });
    }),
  ),
);

FileSystem

Reading Files

import { FileSystem } from "@effect/platform";
import { NodeFileSystem } from "@effect/platform-node";

const program = Effect.gen(function* () {
  const fs = yield* FileSystem.FileSystem;

  const content = yield* fs.readFileString("./config.json");

  const bytes = yield* fs.readFile("./image.png");

  const exists = yield* fs.exists("./file.txt");
}).pipe(Effect.provide(NodeFileSystem.layer));

Writing Files

const program = Effect.gen(function* () {
  const fs = yield* FileSystem.FileSystem;

  yield* fs.writeFileString("./output.txt", "Hello, World!");

  yield* fs.writeFile("./data.bin", new Uint8Array([1, 2, 3]));

  yield* fs.appendFileString("./log.txt", "New log entry\n");
});

Directory Operations

const program = Effect.gen(function* () {
  const fs = yield* FileSystem.FileSystem;

  yield* fs.makeDirectory("./new-dir", { recursive: true });

  const files = yield* fs.readDirectory("./src");

  yield* fs.remove("./temp", { recursive: true });

  yield* fs.copy("./source.txt", "./dest.txt");

  yield* fs.rename("./old.txt", "./new.txt");
});

File Info

const program = Effect.gen(function* () {
  const fs = yield* FileSystem.FileSystem;

  const stat = yield* fs.stat("./file.txt");

  console.log({
    size: stat.size,
    isFile: stat.type === "File",
    isDirectory: stat.type === "Directory",
    modified: stat.mtime,
  });
});

KeyValueStore

Persistent key-value storage:

import { KeyValueStore } from "@effect/platform";
import { NodeKeyValueStore } from "@effect/platform-node";

const program = Effect.gen(function* () {
  const store = yield* KeyValueStore.KeyValueStore;

  yield* store.set("user:1", JSON.stringify({ name: "Alice" }));

  const value = yield* store.get("user:1");

  yield* store.remove("user:1");

  const exists = yield* store.has("user:1");
}).pipe(Effect.provide(NodeKeyValueStore.layerFileSystem("./data")));

Terminal

CLI interactions:

import { Terminal } from "@effect/platform";
import { NodeTerminal } from "@effect/platform-node";

const program = Effect.gen(function* () {
  const terminal = yield* Terminal.Terminal;

  const name = yield* terminal.readLine;

  yield* terminal.display(`Hello, ${name}!`);
}).pipe(Effect.provide(NodeTerminal.layer));

Complete Example: REST API

import { HttpServer, HttpServerResponse, HttpServerRequest } from "@effect/platform";
import { NodeHttpServer } from "@effect/platform-node";
import { Effect, Layer, Schema } from "effect";
import { createServer } from "node:http";

// Schemas
const CreateUser = Schema.Struct({
  name: Schema.String,
  email: Schema.String,
});

const User = Schema.Struct({
  id: Schema.Number,
  name: Schema.String,
  email: Schema.String,
});

// In-memory store
let users: Schema.Schema.Type<typeof User>[] = [];
let nextId = 1;

// Routes
const app = HttpServer.router.empty.pipe(
  HttpServer.router.get("/users", HttpServerResponse.json(users)),

  HttpServer.router.post(
    "/users",
    Effect.gen(function* () {
      const body = yield* HttpServerRequest.schemaBodyJson(CreateUser);
      const user = { id: nextId++, ...body };
      users.push(user);
      return HttpServerResponse.json(user, { status: 201 });
    }),
  ),

  HttpServer.router.get(
    "/users/:id",
    Effect.gen(function* () {
      const { id } = yield* HttpServer.router.params;
      const user = users.find((u) => u.id === parseInt(id));
      return user ? HttpServerResponse.json(user) : HttpServerResponse.json({ error: "Not found" }, { status: 404 });
    }),
  ),
);

// Server
const ServerLive = NodeHttpServer.layer(createServer, { port: 3000 });

const main = HttpServer.serve(app).pipe(Effect.provide(ServerLive), Effect.catchAllCause(Effect.logError));

Effect.runPromise(main);

Best Practices

1. Use Schema validation - Validate all external data
2. Provide platform layers - NodeHttpClient.layer, etc.
3. Handle errors - Network failures, file not found, etc.
4. Use Effect.scoped for resources - Files, connections
5. Configure timeouts - Prevent hanging requests

Additional Resources

For comprehensive platform documentation, consult ${CLAUDE_PLUGIN_ROOT}/references/llms-full.txt.

Search for these sections:

• "HTTP Client" for making requests
• "HTTP Server" for building servers
• "FileSystem" for file operations
• "KeyValueStore" for persistent storage
• "Terminal" for CLI interactions