fp-refactor

# Refactoring Imperative Code to fp-ts This skill provides comprehensive patterns and strategies for migrating existing imperative TypeScript code to fp-ts functional programming patterns. ## When to Use - You are refactoring an existing imperative TypeScript codebase toward fp-ts patterns. - The task involves converting `try/catch`, null checks, callbacks, DI, or loops into functional equivalents. - You need migration guidance and tradeoffs, not just isolated fp-ts examples. ## Table of Contents 1. [Converting try-catch to Either/TaskEither](#1-converting-try-catch-to-eithertaskeither) 2. [Converting null checks to Option](#2-converting-null-checks-to-option) 3. [Converting callbacks to Task](#3-converting-callbacks-to-task) 4. [Converting class-based DI to Reader](#4-converting-class-based-di-to-reader) 5. [Converting imperative loops to functional operations](#5-converting-imperative-loops-to-functional-operations) 6. [Migrating Promise chains to TaskEither](#6-migrating-promise-chains-to-taskeither) 7. [Common Pitfalls](#7-common-pitfalls) 8. [Gradual Adoption Strategies](#8-gradual-adoption-strategies) 9. [When NOT to Refactor](#9-when-not-to-refactor) --- ## 1. Converting try-catch to Either/TaskEither ### The Problem with try-catch Traditional try-catch blocks have several issues: - Error handling is implicit and easy to forget - The type system doesn't track which functions can throw - Control flow is non-linear and harder to reason about - Composing multiple...