1 files changed, 80 insertions, 0 deletions
diff --git a/src/repl.ts b/src/repl.ts
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index 0000000..a42183a
--- /dev/null
+++ b/src/repl.ts
@@ -0,0 +1,80 @@
+import type { TracingLogger } from './utils';
+import * as readline from 'node:readline/promises';
+import { stdin as input, stdout as output } from 'node:process';
+import { peggyParse } from './parser';
+import { evaluate } from './interpreter';
+
+// cool asci logo for CPS
+const LOGO = `
+ _______   ________   ______   _______   __       
+/       \\ /        | /      \\ /       \\ /  |      
+$$$$$$$  |$$$$$$$$/ /$$$$$$  |$$$$$$$  |$$ |      
+$$ |__$$ |$$ |__    $$ |  $$/ $$ |__$$ |$$ |      
+$$    $$< $$    |   $$ |      $$    $$/ $$ |      
+$$$$$$$  |$$$$$/    $$ |   __ $$$$$$$/  $$ |      
+$$ |  $$ |$$ |_____ $$ \\__/  |$$ |      $$ |_____ 
+$$ |  $$ |$$       |$$    $$/ $$ |      $$       |
+$$/   $$/ $$$$$$$$/  $$$$$$/  $$/       $$$$$$$$/ 
+
+`;
+
+const HELP = `
+  This is the CPS REPL. You can enter CPS programs and see the result of evaluating them.
+  This REPL supports multi-line input. To end a multi-line input, enter an empty line.
+  
+  Commands:
+    help - Show this message
+    exit - Exit the REPL
+  
+  About:
+    Read "Compiling With Continuations" by Andrew W. Appel for more information about 
+    this Intermediate Representation.
+  
+  Example:
+    ~> PRIMOP(+, [INT 1, INT 2], [result], [
+     |   APP(LABEL id, [VAR result])
+     | ])
+`;
+
+export const doRepl = async (
+  logger: TracingLogger,
+  prompt = 0,
+  rl = readline.createInterface({ input, output }),
+): Promise<any> => {
+  if (prompt === 0) {
+    logger.info('welcome to recpl (read eval continue print loop) :)' + LOGO);
+  }
+
+  const promptString = `[ ${prompt} ] ~> `;
+  const lines: string[] = [await rl.question(promptString)];
+  while (lines.at(-1)) {
+    const line = lines.at(-1)!;
+
+    if (lines.length === 1 && line === 'help') {
+      logger.info(HELP);
+      return doRepl(logger, prompt + 1, rl);
+    }
+    if (line === 'exit') {
+      logger.info('Exiting REPL...');
+      rl.close();
+      return;
+    }
+
+    lines.push(
+      await rl.question(`|`.padStart(promptString.length - 1, ' ') + ' '),
+    );
+  }
+
+  const program = lines.slice(0, -1).join('\n');
+  try {
+    const ast = peggyParse(program);
+    logger.debug('AST: ' + JSON.stringify(ast, null, 2));
+
+    const result = await evaluate(ast, logger.createChild('evaluate'));
+    logger.info('Result: ' + JSON.stringify(result, null, 2) + '\n');
+  } catch (e) {
+    logger.error(e!.toString() + '\n');
+  }
+
+  return doRepl(logger, prompt + 1, rl);
+};