Add envar writer to generate code for jsr:@wuespace/envar

With this change, it is possible to, based on the example env file,
automatically generate code to use with the `jsr:@wuespace/envar` package.

This generates a self-contained file which exports a function `initEnv(): Promise<void>`,
which initializes the variables with basic validators.

Usage:

```shell
envardoc envar -o lib/env.ts example.env
```

README.md

@@ -18,6 +18,7 @@ envardoc <writer> <path-to-env-file>
 
 - `docs` - Prints the documentation in markdown format
 - `example` - Prints a `.env.example` file with all variables and comments
+- `envar` - Prints TypeScript code to use with the [`jsr:@wuespace/envar`](https://jsr.io/@wuespace/envar) package.
 
 ### With Deno
 

lib/writers/envar.ts

@@ -0,0 +1,58 @@
+import type { Writer } from "$writers";
+import type { Variable } from "$ast";
+
+export class EnvarWriter implements Writer {
+  writeHeader(prev: string): string {
+    return prev + `import {
+  initVariable,
+  REQUIRED,
+  OPTIONAL,
+} from "jsr:@wuespace/envar";
+ 
+/**
+ * Initializes the environment variables using the jsr:@wuespace/envar library.
+ * 
+ * Automatically generated by [envardoc](https://jsr.io/@wuespace/envardoc).
+ */
+export function initEnv(): Promise<void> {
+  return Promise.all([
+`;
+  }
+
+  writeVariable(variable: Variable, prev: string): string {
+    variable.description?.trim().split("\n").forEach((line) => {
+      prev += `    // ${line}\n`;
+    });
+    if (variable.optional) {
+      return this.writeOptionalVariable(variable, prev) + "\n";
+    } else {
+      return this.writeRequiredVariable(variable, prev) + "\n";
+    }
+  }
+
+  private writeOptionalVariable(variable: Variable, prev: string): string {
+    prev += '    initVariable("';
+    prev += variable.name;
+    prev += '", OPTIONAL';
+    if (variable.defaultValue) {
+      prev += ', "';
+      prev += variable.defaultValue;
+      prev += '"';
+    }
+    prev += "),\n";
+    return prev;
+  }
+
+  private writeRequiredVariable(variable: Variable, prev: string): string {
+    prev += '    initVariable("';
+    prev += variable.name;
+    prev += '", REQUIRED),\n';
+    return prev;
+  }
+
+  writeFooter(prev: string): string {
+    return prev.trimEnd() + `\n  ]);
+}
+`;
+  }
+}

lib/writers/mod.ts

@@ -1,3 +1,4 @@
 export * from "./docs.ts";
 export * from "./env-example.ts";
+export * from "./envar.ts";
 export * from "./Writer.ts";

main.ts

@@ -1,5 +1,10 @@
 import { parse } from "$parse";
-import { DocsWriter, EnvExampleWriter, type Writer } from "$writers";
+import {
+  DocsWriter,
+  EnvarWriter,
+  EnvExampleWriter,
+  type Writer,
+} from "$writers";
 import { Command } from "@cliffy/command";
 import { exists } from "@std/fs";
 import { resolve } from "@std/path";
@@ -23,6 +28,23 @@ if (import.meta.main) {
       }
     });
 
+  const envar = new Command()
+    .arguments("<path:file>")
+    .description("Generate jsr:@wuespace/envar source code from a .env file")
+    .option("-o, --output <path:string>", "Output file path")
+    .action(async ({ output }, path) => {
+      const sourceCode = await parseAndConvert(
+        path,
+        new EnvarWriter(),
+      );
+      if (output) {
+        await Deno.writeTextFile(output, sourceCode);
+        console.log(`File written: ${output}`);
+      } else {
+        console.log(sourceCode);
+      }
+    });
+
   const envExample = new Command()
     .arguments("<path:string>")
     .description("Generate example .env file")
@@ -52,6 +74,7 @@ if (import.meta.main) {
     )
     .command("docs", docs)
     .command("example", envExample)
+    .command("envar", envar)
     .parse(Deno.args);
 }