add weather cli example

cli/src/index.ts

@@ -0,0 +1,38 @@
+import { Effect, Option, Cause, Layer } from 'effect'
+import * as Http from '@effect/platform-node/HttpClient'
+import * as Node from '@effect/platform-node/Runtime'
+import * as Command from '@effect/cli/Command'
+import * as Cli from '@effect/cli/CliApp'
+import * as Options from '@effect/cli/Options'
+import * as Args from '@effect/cli/Args'
+import * as Console from '@effect/cli/Console'
+import * as Wttr from './wttr'
+
+const cli = Cli.make({
+  name: 'Weather',
+  version: '1.2.3',
+  command: Command.make('weather', {
+    args: Args.between(Args.text({ name: 'location' }), 0, 1),
+    options: Options.all({
+      url: Options.withDefault(Options.text('url'), 'https://wttr.in'),
+    }),
+  })
+})
+
+Node.runMain(Effect.sync(() => process.argv.slice(2)).pipe(
+  Effect.flatMap((args) =>
+    Cli.run(cli, args, ({ options, args }) => {
+      const location = Option.fromIterable(args)
+      const program = Wttr.Wttr.pipe(
+        Effect.flatMap(wttr => wttr.getWeather(location)),
+        // TODO: Render the output properly.
+        Effect.tap(Effect.log),
+      )
+
+      const wttr = Layer.provide(Http.client.layer, Wttr.makeLayer(options.url))
+      return Effect.provideLayer(program, wttr)
+    })
+  ),
+  Effect.provideLayer(Console.layer),
+  Effect.tapErrorCause((_) => Effect.logError(Cause.pretty(_)))
+))

cli/src/wttr.ts

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+import { Effect, Data, Context, Layer, Option } from 'effect'
+import * as Http from '@effect/platform/HttpClient'
+import * as Schema from '@effect/schema/Schema'
+
+type WttrWeather = Schema.Schema.To<typeof WttrWeatherSchema>
+const WttrWeatherSchema = Schema.struct({
+  date: Schema.dateFromString(Schema.string),
+  avgtempC: Schema.numberFromString(Schema.string),
+  avgtempF: Schema.numberFromString(Schema.string),
+  maxtempC: Schema.numberFromString(Schema.string),
+  maxtempF: Schema.numberFromString(Schema.string),
+  mintempC: Schema.numberFromString(Schema.string),
+  mintempF: Schema.numberFromString(Schema.string),
+  sunHour: Schema.numberFromString(Schema.string),
+  uvIndex: Schema.numberFromString(Schema.string)
+})
+
+const WttrResponseSchema = Schema.struct({
+  weather: Schema.array(WttrWeatherSchema)
+})
+
+class WttrError extends Data.TaggedClass('WttrError')<{
+  cause: unknown
+}> {}
+
+export const Wttr = Context.Tag<Wttr>()
+export interface Wttr {
+  readonly getWeather: (location: Option.Option<string>) => Effect.Effect<never, WttrError, ReadonlyArray<WttrWeather>>
+}
+
+export const makeLayer = (url: string) => Layer.effect(Wttr, Effect.gen(function* ($) {
+  const defaultClient = yield* $(Http.client.Client)
+  const wttrClient = defaultClient.pipe(
+    Http.client.mapRequest(Http.request.prependUrl(url)),
+    Http.client.mapRequest(Http.request.appendUrlParam('format', 'j1')),
+    Http.client.filterStatusOk,
+    Http.client.mapEffect(Http.response.schemaBodyJson(WttrResponseSchema)),
+    Http.client.catchTags({
+      'RequestError': (cause) => Effect.fail(new WttrError({ cause })),
+      'ResponseError': (cause) => Effect.fail(new WttrError({ cause })),
+      'ParseError': (cause) => Effect.fail(new WttrError({ cause })),
+    }),
+  )
+
+  return Wttr.of({
+    getWeather: (location) => Option.match(location, {
+      onNone: () => Http.request.get('/'),
+      onSome: (_) => Http.request.get(`/${encodeURIComponent(_)}`),
+    }).pipe(wttrClient, Effect.map(_ => _.weather)),
+  })
+}))

cli/tsconfig.json

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+{
+  "compilerOptions": {
+    "noEmit": true,
+    "module": "Node16",
+    "moduleResolution": "Node16",
+    "strict": true,
+    "plugins": [{ "name": "@effect/language-service" }],
+  },
+  "include": ["src/**/*.ts"]
+}