fix: use CLI flag --output (#46)

The flag was not used to determine the output dir.

Now, if the flag is set, it is used as output dir,
if not set, directory containing the proto file is used.

packages/protons/src/index.ts

@@ -3,8 +3,9 @@ import path from 'path'
 import { promisify } from 'util'
 import fs from 'fs/promises'
 
-function pathWithExtension (input: string, extension: string) {
-  return path.join(path.dirname(input), path.basename(input).split('.').slice(0, -1).join('.') + extension)
+function pathWithExtension (input: string, extension: string, outputDir?: string) {
+  const output = outputDir ?? path.dirname(input)
+  return path.join(output, path.basename(input).split('.').slice(0, -1).join('.') + extension)
 }
 
 const types: Record<string, string> = {
@@ -285,7 +286,11 @@ function defineModule (def: ClassDef): ModuleDef {
   return moduleDef
 }
 
-export async function generate (source: string, flags: any) {
+interface Flags {
+  output?: string
+}
+
+export async function generate (source: string, flags: Flags) {
   // convert .protobuf to .json
   const json = await promisify(pbjs)(['-t', 'json', source])
 
@@ -318,5 +323,5 @@ export async function generate (source: string, flags: any) {
 
   const content = lines.join('\n').trim()
 
-  await fs.writeFile(pathWithExtension(source, '.ts'), content + '\n')
+  await fs.writeFile(pathWithExtension(source, '.ts', flags.output), content + '\n')
 }