Typescript Effect

[H1][TYPESCRIPT-EFFECT]

Dictum: Six pillars govern TypeScript generation—algorithmic, parametric, polymorphic, functional, expressive, typed.

Generate TypeScript code adhering to Effect ecosystem patterns.

Pillars:

1. Algorithmic — Derive values from frozen B constant
2. Parametric — Expose tuning via factory parameters
3. Polymorphic — Select implementation via dispatch tables
4. Functional-Monadic — Chain via Effect/Option pipelines
5. Expression-Centric — Ternaries, implicit returns, no blocks
6. Strong-Typed — Branded types via @effect/schema

File Structure:

// --- [TYPES] -----------------------------------------------------------------
// --- [SCHEMA] ----------------------------------------------------------------
// --- [CONSTANTS] -------------------------------------------------------------
// --- [CLASSES] ---------------------------------------------------------------
// --- [SERVICES] --------------------------------------------------------------
// --- [PURE_FUNCTIONS] --------------------------------------------------------
// --- [DISPATCH_TABLES] -------------------------------------------------------
// --- [EFFECT_PIPELINE] -------------------------------------------------------
// --- [LAYERS] ----------------------------------------------------------------
// --- [ENTRY_POINT] -----------------------------------------------------------
// --- [EXPORT] ----------------------------------------------------------------

Core Sections (omit unused): Types → Schema → Constants → Classes → Services → Pure Functions → Dispatch Tables → Effect Pipeline → Layers → Entry Point → Export.

[CRITICAL]:

• [NEVER] any — use branded types.
• [NEVER] let/var — use const only.
• [NEVER] if/else — use dispatch tables or ternaries.
• [NEVER] for/while — use .map, .filter, Effect.
• [NEVER] try/catch — use Effect error channel.
• [NEVER] Default exports — use named exports (except *.config.ts).

[1][ALGORITHMIC]

Dictum: Derive values from base constant via formula—zero hardcoded literals.

Single frozen B constant per file. ALL values derive from B properties.

const B = Object.freeze({
  fontSize: 16,
  ratio: 1.333,
} as const);

const derive = (step: number): number => B.fontSize * B.ratio ** step;

const scale = Object.freeze({
  sm: derive(-1),  // 12px = 16 * 1.333^-1
  md: derive(0),   // 16px = 16 * 1.333^0
  lg: derive(1),   // 21px = 16 * 1.333^1
} as const);

[IMPORTANT]:

• [ALWAYS] Define ONE B constant with Object.freeze().
• [ALWAYS] Express derivations as inline calculations—formula IS the code.
• [ALWAYS] Trace every value to B through visible arithmetic.
• [NEVER] Numeric literals outside B constant.

[2][PARAMETRIC]

Dictum: Expose tuning at call-site via factory parameters—zero buried controls.

Factory functions accept partial config; merge with B defaults.

const B = Object.freeze({
  timeoutMs: 5000,
  maxAttempts: 3,
} as const);

const createRetry = (overrides: Partial<typeof B> = {}) =>
  Object.freeze({
    config: { ...B, ...overrides },
    execute: <T>(fn: () => Promise<T>): Promise<T> => fn(),
  });

// Call-site tuning
const fast = createRetry({ timeoutMs: 1000 });
const resilient = createRetry({ maxAttempts: 5 });

[IMPORTANT]:

• [ALWAYS] Defaults in B; overrides at call-site.
• [ALWAYS] Factory returns frozen object.
• [NEVER] Hardcode tunable values in implementation.

[3][POLYMORPHIC]

Dictum: Select implementation via keyed dispatch—zero conditional branching.

Dispatch tables replace if/else/switch. Discriminated unions enable exhaustiveness.

import { Schema } from 'effect';

const Shape = Schema.Union(
  Schema.Struct({ kind: Schema.Literal('circle'), radius: Schema.Number }),
  Schema.Struct({ kind: Schema.Literal('rect'), width: Schema.Number, height: Schema.Number }),
);
type Shape = typeof Shape.Type;

const handlers = {
  circle: (s: Extract<Shape, { kind: 'circle' }>) => Math.PI * s.radius ** 2,
  rect: (s: Extract<Shape, { kind: 'rect' }>) => s.width * s.height,
} as const satisfies Record<Shape['kind'], (s: never) => number>;

const area = (shape: Shape): number => handlers[shape.kind](shape as never);

[IMPORTANT]:

• [ALWAYS] Route via handlers[discriminant](data).
• [ALWAYS] Enforce exhaustiveness with satisfies Record<Discriminant, Handler>.
• [NEVER] if/else for type-based dispatch.
• [NEVER] switch/case statements.

[4][FUNCTIONAL-MONADIC]

Dictum: Chain operations via typed channels—Effect for async/failable, Option for nullable.

Effect pipelines replace try/catch. Option wraps nullable values.

import { Effect, Option, pipe } from 'effect';

class ValidationError {
  readonly _tag = 'ValidationError';
  constructor(readonly reason: string) {}
}

const processUser = (raw: { name?: string }) =>
  pipe(
    Option.fromNullable(raw.name),
    Option.map((name) => name.trim().toUpperCase()),
    Option.match({
      onNone: () => Effect.fail(new ValidationError('Missing name')),
      onSome: (name) => Effect.succeed({ name }),
    }),
  );
// Effect<{ name: string }, ValidationError, never>

[IMPORTANT]:

• [ALWAYS] Wrap nullable with Option.fromNullable().
• [ALWAYS] Sequence via pipe() and Effect.flatMap().
• [ALWAYS] Track outcomes in type parameters: Effect<A, E, R>.
• [NEVER] try/catch or throw in Effect code.
• [NEVER] Null checks or optional chaining in logic.

[5][EXPRESSION-CENTRIC]

Dictum: Write code as value-producing expressions—zero statement blocks.

Ternaries for conditionals. Implicit returns for arrows. Chain expressions.

// Expression: ternary + implicit return
const classify = (age: number): string =>
  age < 18 ? 'minor' : age < 65 ? 'adult' : 'senior';

// Expression: chained transforms
const processUsers = (users: ReadonlyArray<{ name: string; age: number }>) =>
  users
    .filter((u) => u.age >= 18)
    .map((u) => ({ ...u, name: u.name.toUpperCase() }))
    .sort((a, b) => a.name.localeCompare(b.name));

[IMPORTANT]:

• [ALWAYS] Ternary ? : over if/else.
• [ALWAYS] Arrow with implicit return: x => x * 2.
• [ALWAYS] Compose via .map(), .filter(), pipe().
• [NEVER] Curly braces {} in single-expression contexts.
• [NEVER] Intermediate let bindings.

[6][STRONG-TYPED]

Dictum: Brand domain primitives via @effect/schema—zero raw primitives in domain logic.

Branded types enforce semantic boundaries. Schema validates at system edges.

import { Schema } from 'effect';

// Branded primitive
const UserId = Schema.String.pipe(Schema.brand('UserId'));
type UserId = typeof UserId.Type;

// Validated struct
const UserSchema = Schema.Struct({
  id: UserId,
  email: Schema.String.pipe(Schema.pattern(/@/)),
  age: Schema.Number.pipe(Schema.positive()),
});
type User = typeof UserSchema.Type;

// Decode at boundary
const parseUser = Schema.decodeUnknownSync(UserSchema);

[IMPORTANT]:

• [ALWAYS] Brand domain primitives: UserId, Email, IsoDate.
• [ALWAYS] Validate at system boundaries (API input, external data).
• [ALWAYS] Derive type from schema: typeof Schema.Type.
• [NEVER] any or unbranded primitives in domain logic.

[7][VALIDATION]

Dictum: Gates prevent non-compliant code generation.

[VERIFY] Before completing any TypeScript generation:

• B Constant: Single frozen B with all tunable values.
• Derivation: All computed values trace to B via visible arithmetic.
• Factory: createX pattern with partial config merging B.
• Dispatch: Handlers object with satisfies Record<K, Handler>.
• Effect: Async/failable operations use Effect pipelines.
• Option: Nullable values wrapped with Option.fromNullable().
• Expression: No if/else blocks; ternaries and implicit returns.
• Branded: Domain primitives use Schema.brand().
• Sections: File uses canonical section separators.
• Exports: Named exports only (except *.config.ts).

[CRITICAL] Violation detected → Refactor before completion.