1 files changed, 94 insertions, 0 deletions
diff --git a/deno/base/config.ts b/deno/base/config.ts
new file mode 100644
index 0000000..98722f6
--- /dev/null
+++ b/deno/base/config.ts
@@ -0,0 +1,94 @@
+import { camelCaseToKebabCase } from "./text.ts";
+
+export interface ConfigDefinitionItem {
+  readonly description: string;
+  readonly default?: string;
+  readonly secret?: boolean;
+}
+
+interface ConfigMapItem extends ConfigDefinitionItem {
+  readonly env: string;
+  value?: string;
+}
+
+export type ConfigDefinition<K extends string = string> = Record<
+  K,
+  ConfigDefinitionItem
+>;
+type ConfigMap<K extends string = string> = Record<K, ConfigMapItem>;
+
+export class ConfigProvider<K extends string> {
+  readonly #prefix: string;
+  readonly #map: ConfigMap<K>;
+
+  constructor(prefix: string, ...definitions: Partial<ConfigDefinition<K>>[]) {
+    this.#prefix = prefix;
+
+    const map: ConfigMap = {};
+    for (const definition of definitions) {
+      for (const [key, def] of Object.entries(definition as ConfigDefinition)) {
+        map[key] = {
+          ...def,
+          env: `${this.#prefix}-${camelCaseToKebabCase(key as string)}`
+            .replaceAll("-", "_")
+            .toUpperCase(),
+        };
+      }
+    }
+    this.#map = map as ConfigMap<K>;
+  }
+
+  resolveFromEnv(options?: { keys?: K[] }) {
+    const keys = options?.keys ?? Object.keys(this.#map);
+    for (const key of keys) {
+      const { env, description, default: _default } = this.#map[key as K];
+      const value = Deno.env.get(env) ?? _default;
+      if (value == null) {
+        throw new Error(`Required env ${env} (${description}) is not set.`);
+      }
+      this.#map[key as K].value = value;
+    }
+  }
+
+  get(key: K): string {
+    if (!(key in this.#map)) {
+      throw new Error(`Unknown config key ${key as string}.`);
+    }
+    if (this.#map[key].value == null) {
+      this.resolveFromEnv({ keys: [key] });
+    }
+    return this.#map[key].value!;
+  }
+
+  set(key: K, value: string) {
+    if (!(key in this.#map)) {
+      throw new Error(`Unknown config key ${key as string}.`);
+    }
+    this.#map[key].value = value;
+  }
+
+  getInt(key: K): number {
+    return Number(this.get(key));
+  }
+
+  getList(key: K, separator: string = ","): string[] {
+    const value = this.get(key);
+    if (value.length === 0) return [];
+    return value.split(separator);
+  }
+
+  [Symbol.for("Deno.customInspect")]() {
+    const getValueString = (item: ConfigMapItem): string => {
+      if (item.value == null) return "(unresolved)";
+      if (item.secret === true) return "***";
+      return item.value;
+    };
+
+    return Object.entries(this.#map as ConfigMap)
+      .map(
+        ([key, item]) => `${key} [env: ${item.env}]: ${getValueString(item)}`,
+      )
+      .join("\n");
+  }
+}
+