1/**
2 * @title Composing services with the Layer module
3 *
4 * Build focused service layers, then compose them with `Layer.provide` and
5 * `Layer.provideMerge` based on what services you want to expose.
6 */
7
8import { PgClient } from "@effect/sql-pg"
9import { Array, Config, Context, Effect, Layer, type Option, Schema } from "effect"
10import { SqlClient, SqlError } from "effect/sql"
11
12// Define a layer for the SqlClient service
13export const SqlClientLayer: Layer.Layer<
14 PgClient.PgClient | SqlClient.SqlClient,
15 Config.ConfigError | SqlError.SqlError
16> = PgClient.layerConfig({
17 url: Config.Redacted("DATABASE_URL")
18})
19
20export class UserRespositoryError extends Schema.TaggedError<UserRespositoryError>()("UserRespositoryError", {
21 reason: SqlError.SqlError
22}) {}
23
24export class UserRepository extends Context.Service<UserRepository, {
25 findById(id: string): Effect.Effect<
26 Option.Option<{ readonly id: string; readonly name: string }>,
27 UserRespositoryError
28 >
29}>()("myapp/UserRepository") {
30 // Implement the layer for the UserRepository service, which depends on the
31 // SqlClient service
32 static readonly layerNoDeps: Layer.Layer<
33 UserRepository,
34 never,
35 SqlClient.SqlClient
36 > = Layer.effect(
37 UserRepository,
38 Effect.gen(function*() {
39 const sql = yield* SqlClient.SqlClient
40
41 const findById = Effect.fn("UserRepository.findById")(function*(id: string) {
42 const results = yield* sql<{
43 readonly id: string
44 readonly name: string
45 }>`SELECT * FROM users WHERE id = '${id}'`
46 return Array.head(results)
47 }, Effect.mapError((reason) => new UserRespositoryError({ reason })))
48
49 return UserRepository.of({ findById })
50 })
51 )
52
53 // Use Layer.provide to compose the UserRepository layer with the SqlClient
54 // layer, exposing only the UserRepository service
55 static readonly layer: Layer.Layer<
56 UserRepository,
57 Config.ConfigError | SqlError.SqlError
58 > = this.layerNoDeps.pipe(
59 Layer.provide(SqlClientLayer)
60 )
61
62 // Use Layer.provideMerge to compose the UserRepository layer with the SqlClient
63 // layer, exposing both the UserRepository and SqlClient services
64 static readonly layerWithSqlClient: Layer.Layer<
65 UserRepository | SqlClient.SqlClient,
66 Config.ConfigError | SqlError.SqlError
67 > = this.layerNoDeps.pipe(
68 Layer.provideMerge(SqlClientLayer)
69 )
70}