effect-patterns-platform-getting-started

Effect-TS Patterns: Platform Getting Started

This skill provides 2 curated Effect-TS patterns for platform getting started. Use this skill when working on tasks related to:

• platform getting started
• Best practices in Effect-TS applications
• Real-world patterns and solutions

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🟢 Beginner Patterns

Your First Platform Operation

Rule: Use @effect/platform for cross-platform system operations with Effect integration.

Good Example:

import { Effect } from "effect"
import { FileSystem } from "@effect/platform"
import { NodeContext, NodeRuntime } from "@effect/platform-node"

// Read a file - returns Effect<string, PlatformError>
const readConfig = Effect.gen(function* () {
  const fs = yield* FileSystem.FileSystem
  
  // Read file as UTF-8 string
  const content = yield* fs.readFileString("./config.json")
  
  return JSON.parse(content)
})

// Write a file
const writeLog = Effect.gen(function* () {
  const fs = yield* FileSystem.FileSystem
  
  yield* fs.writeFileString(
    "./app.log",
    `Started at ${new Date().toISOString()}\n`
  )
})

// Combine operations
const program = Effect.gen(function* () {
  const config = yield* readConfig
  yield* Effect.log(`Loaded config: ${config.appName}`)
  
  yield* writeLog
  yield* Effect.log("Log file created")
})

// Run with Node.js platform
program.pipe(
  Effect.provide(NodeContext.layer),
  NodeRuntime.runMain
)

Rationale:

Effect Platform provides type-safe, cross-platform system operations. Use @effect/platform-node for Node.js or @effect/platform-bun for Bun.

---

Platform wraps system operations in Effect, giving you:

1. Type safety - File operations return Effect<Content, PlatformError>
2. Resource management - Files are automatically closed
3. Cross-platform - Same code works on Node.js, Bun, browser
4. Composability - Chain file ops with other effects

---

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Access Environment Variables

Rule: Use Effect to access environment variables with proper error handling.

Good Example:

import { Effect, Config, Option } from "effect"

// ============================================
// BASIC: Read required variable
// ============================================

const getApiKey = Config.string("API_KEY")

const program1 = Effect.gen(function* () {
  const apiKey = yield* getApiKey
  yield* Effect.log(`API Key: ${apiKey.slice(0, 4)}...`)
})

// ============================================
// OPTIONAL: With default value
// ============================================

const getPort = Config.number("PORT").pipe(
  Config.withDefault(3000)
)

const program2 = Effect.gen(function* () {
  const port = yield* getPort
  yield* Effect.log(`Server will run on port ${port}`)
})

// ============================================
// OPTIONAL: Return Option instead of failing
// ============================================

const getOptionalFeature = Config.string("FEATURE_FLAG").pipe(
  Config.option
)

const program3 = Effect.gen(function* () {
  const feature = yield* getOptionalFeature
  
  if (Option.isSome(feature)) {
    yield* Effect.log(`Feature enabled: ${feature.value}`)
  } else {
    yield* Effect.log("Feature flag not set")
  }
})

// ============================================
// COMBINED: Multiple variables as config object
// ============================================

const AppConfig = Config.all({
  apiKey: Config.string("API_KEY"),
  apiUrl: Config.string("API_URL"),
  port: Config.number("PORT").pipe(Config.withDefault(3000)),
  debug: Config.boolean("DEBUG").pipe(Config.withDefault(false)),
})

const program4 = Effect.gen(function* () {
  const config = yield* AppConfig
  
  yield* Effect.log(`API URL: ${config.apiUrl}`)
  yield* Effect.log(`Port: ${config.port}`)
  yield* Effect.log(`Debug: ${config.debug}`)
})

// ============================================
// RUN: Will fail if required vars missing
// ============================================

Effect.runPromise(program4).catch((error) => {
  console.error("Missing required environment variables")
  console.error(error)
})

Rationale:

Access environment variables using Effect's built-in functions or Platform's environment service for type-safe configuration.

---

Environment variables can be missing or malformed. Effect helps you:

1. Handle missing vars - Return Option or fail with typed error
2. Validate values - Parse and validate with Schema
3. Provide defaults - Fallback values when vars are missing
4. Document requirements - Types show what's needed

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