Implement the whole thing

src/read_env.ts

@@ -0,0 +1,38 @@
+import logger from 'log'
+import fs from 'node:fs/promises'
+
+import type {Ok} from './helpers'
+
+const log = logger('config:read_env')
+const FILE_EXT = "__FILE"
+
+// Read from env or file
+export async function read_env(key: string): Promise<Ok<string | undefined>> {
+    const path = process.env[key + FILE_EXT]
+    if (path !== undefined) return from_file(path)
+    else return {ok: true, data: process.env[key]}
+}
+async function from_file(path: string): Promise<Ok<string>> {
+    log.debug("Read a key from a file")
+    log.trace("Path :", path)
+
+    let content = await get_file_content(path)
+    if (!content.ok) return content
+
+    content.data = content.data.trim()
+
+    return content
+}
+async function get_file_content(path: string) : Promise<Ok<string>> {
+    log.debug('Read file content')
+    log.trace('Path :', path)
+
+    try {
+        const data = await fs.readFile(path, {encoding: 'utf-8'})
+        return {ok: true, data}
+    } catch (e) {
+        log.warn('Failed to read file', path)
+        log.debug('Error :', e)
+        return {ok: false}
+    }
+}