feat: add rollback_on_failure feature (#88)

This PR adds the ability to download existing code before deployment and automatically roll back if the post-deployment monitor detects a failure.

Reviewed-on: #88
Reviewed-by: LLMReview <27+autoreview@noreplay.horstenkamp.eu>

index.js

@@ -118,17 +118,19 @@ export function validateAuthentication(token, username, password) {
  * @param {'ignore'|'warn'|'fail'} action
  * @param {boolean} flag    - Only acts when true
  * @param {string}  message - Passed to core.warning / core.setFailed
+ * @returns {boolean} - Returns true if the action was 'fail' and the flag was true.
  */
 export function applyOnAction(action, flag, message) {
-  if (!flag) return;
+  if (!flag) return false;
   if (action === "warn") {
     core.warning(message);
-    return;
+    return false;
   }
   if (action === "fail") {
     core.setFailed(message);
+    return true;
   }
-  // 'ignore' → no-op
+  return false;
 }
 
 /**
@@ -179,33 +181,72 @@ export async function postCode() {
     return;
   }
   let api = new ScreepsAPI(login_arguments);
-  if (token) {
+
+  if (!token) {
+    core.info(`Logging in as user ${username}`);
+    try {
+      await api.auth(username, password, login_arguments);
+    } catch (err) {
+      core.error(`Authentication error: ${err}`);
+      throw err;
+    }
+  }
+
+  let oldCode = null;
+  let rollbackOnFailure = false;
+  try {
+    rollbackOnFailure = core.getBooleanInput("rollback_on_failure");
+  } catch (e) {
+    // getBooleanInput throws if not 'true' or 'false', ignore
+  }
+
+  if (rollbackOnFailure) {
+    core.info(
+      `Downloading existing code from branch ${branch} for potential rollback...`,
+    );
+    try {
+      const getResponse = await api.code.get(branch);
+      if (getResponse && getResponse.ok && getResponse.modules) {
+        oldCode = getResponse.modules;
+        core.info(
+          `Successfully downloaded existing code (modules: ${Object.keys(oldCode).join(", ")})`,
+        );
+      } else {
+        core.setFailed(
+          `Failed to download existing code, but rollback_on_failure is enabled. Aborting deployment.`,
+        );
+        return;
+      }
+    } catch (err) {
+      core.setFailed(
+        `Error downloading existing code: ${err.message}. Aborting deployment.`,
+      );
+      return;
+    }
+  }
+
+  try {
     const response = await api.code.set(branch, files_to_push);
     core.info(JSON.stringify(response, null, 2));
     core.info(`Code set successfully to ${branch}`);
-  } else {
-    core.info(`Logging in as user ${username}`);
-    await Promise.resolve()
-      .then(() => api.auth(username, password, login_arguments))
-      .then(() => api.code.set(branch, files_to_push))
-      .then(() => {
-        core.info(`Code set successfully to ${branch}`);
-      })
-      .catch((err) => {
-        core.error(`Upload error: ${err}`);
-        throw err;
-      });
+  } catch (err) {
+    core.error(`Upload error: ${err}`);
+    throw err;
   }
 
   // Console monitoring (optional)
   const monitorTicks = parseInt(core.getInput("monitor") || "0", 10);
   if (monitorTicks > 0) {
+    const onTraceback = core.getInput("on_traceback") || "fail";
+    const onErrorLog = core.getInput("on_error_log") || "warn";
+    const onWarningLog = core.getInput("on_warning_log") || "ignore";
+
     const result = await monitorConsole(api, {
       monitor: monitorTicks,
       logToFile: core.getBooleanInput("log_to_file"),
-      onTraceback: core.getInput("on_traceback") || "fail",
-      onErrorLog: core.getInput("on_error_log") || "warn",
-      onWarningLog: core.getInput("on_warning_log") || "ignore",
+      onTraceback,
+      onErrorLog,
+      onWarningLog,
       monitorInterval: parseInt(core.getInput("monitor_interval") || "10", 10),
       hostname,
       shard: core.getInput("shard") || undefined,
@@ -215,21 +256,37 @@ export async function postCode() {
     core.setOutput("saw_error_log", String(result.sawErrorLog));
     core.setOutput("saw_warning_log", String(result.sawWarningLog));
 
-    applyOnAction(
-      core.getInput("on_traceback"),
+    const fail1 = applyOnAction(
+      onTraceback,
       result.sawTraceback,
       "Screeps console: traceback detected",
     );
-    applyOnAction(
-      core.getInput("on_error_log"),
+    const fail2 = applyOnAction(
+      onErrorLog,
       result.sawErrorLog,
       "Screeps console: error log output detected",
     );
-    applyOnAction(
-      core.getInput("on_warning_log"),
+    const fail3 = applyOnAction(
+      onWarningLog,
       result.sawWarningLog,
       "Screeps console: warning log output detected",
     );
+
+    const shouldFail = fail1 || fail2 || fail3;
+
+    if (shouldFail && rollbackOnFailure && oldCode) {
+      core.info(
+        "Action failed based on monitor configuration. Rolling back to previous code...",
+      );
+      try {
+        await api.code.set(branch, oldCode);
+        core.info(
+          `Successfully rolled back to previous code on branch ${branch}.`,
+        );
+      } catch (err) {
+        core.error(`Rollback failed: ${err}`);
+      }
+    }
   }
 }