feat(issue): Add multi-queue support and enhanced failure handling

- Add --queue parameter for explicit queue targeting (next, dag, detail, done, retry)
- Implement serialized multi-queue execution (complete Q1 before Q2)
- Add queue activate/priority subcommands for multi-queue management
- Add FailureDetail interface for structured failure tracking
- Preserve failure history on retry for debugging
- Show failure reasons and retry count in queue status display
- Auto-detect queue from item ID in done/detail commands

ccw/src/cli.ts

@@ -288,6 +288,7 @@ export function run(argv: string[]): void {
     .option('--reason <text>', 'Failure reason')
     .option('--fail', 'Mark task as failed')
     .option('--from-queue [queue-id]', 'Sync issue statuses from queue (default: active queue)')
+    .option('--queue <queue-id>', 'Target queue ID for multi-queue operations')
     .action((subcommand, args, options) => issueCommand(subcommand, args, options));
 
   program.parse(argv);

ccw/src/commands/issue.ts

@@ -108,6 +108,15 @@ interface Solution {
   bound_at?: string;
 }
 
+// Structured failure detail for debugging
+interface FailureDetail {
+  task_id?: string;              // Which task failed within the solution
+  error_type: string;            // e.g., "compilation", "test_failure", "timeout"
+  message: string;               // Human-readable error message
+  stack_trace?: string;          // Optional stack trace
+  timestamp: string;             // ISO timestamp
+}
+
 interface QueueItem {
   item_id: string;               // Item ID in queue: T-1, T-2, ... (task-level) or S-1, S-2, ... (solution-level)
   issue_id: string;
@@ -124,7 +133,9 @@ interface QueueItem {
   started_at?: string;
   completed_at?: string;
   result?: Record<string, any>;
-  failure_reason?: string;
+  failure_reason?: string;       // Simple string (backward compat)
+  failure_details?: FailureDetail;   // Structured failure info
+  failure_history?: FailureDetail[]; // Preserved on retry for debugging
 }
 
 interface QueueConflict {
@@ -168,10 +179,12 @@ interface Queue {
 }
 
 interface QueueIndex {
-  active_queue_id: string | null;
+  active_queue_id: string | null;    // Single active queue (backward compat)
+  active_queue_ids?: string[];       // Multiple active queues, ordered by priority
   queues: {
     id: string;
     status: string;
+    priority?: number;               // Queue execution priority (lower = higher priority)
     issue_ids: string[];
     total_tasks?: number;          // For task-level queues
     total_solutions?: number;      // For solution-level queues
@@ -197,6 +210,7 @@ interface IssueOptions {
   brief?: boolean;      // List brief info only (id, title, status, priority, tags) - JSON format
   data?: string;        // JSON data for create
   fromQueue?: boolean | string;  // Sync statuses from queue (true=active, string=specific queue ID)
+  queue?: string;       // Target queue ID for multi-queue operations
 }
 
 const ISSUES_DIR = '.workflow/issues';
@@ -528,6 +542,119 @@ function createEmptyQueue(): Queue {
   };
 }
 
+// ============ Multi-Queue Helper Functions ============
+
+/**
+ * Find which queue contains a given item ID
+ * Supports both simple (S-1) and qualified (QUE-xxx:S-1) formats
+ */
+function findItemQueue(itemId: string): { queue: Queue; item: QueueItem; itemIndex: number } | null {
+  // Check if qualified format (QUE-xxx:S-1)
+  const qualifiedMatch = itemId.match(/^(QUE-[^:]+):(.+)$/);
+  if (qualifiedMatch) {
+    const [, queueId, actualItemId] = qualifiedMatch;
+    const queue = readQueue(queueId);
+    if (!queue) return null;
+    const items = queue.solutions || queue.tasks || [];
+    const itemIndex = items.findIndex(i => i.item_id === actualItemId);
+    if (itemIndex === -1) return null;
+    return { queue, item: items[itemIndex], itemIndex };
+  }
+
+  // Search all queues for unqualified item ID
+  const index = readQueueIndex();
+  const activeQueueIds = index.active_queue_ids || (index.active_queue_id ? [index.active_queue_id] : []);
+
+  // Search active queues first
+  for (const queueId of activeQueueIds) {
+    const queue = readQueue(queueId);
+    if (!queue) continue;
+    const items = queue.solutions || queue.tasks || [];
+    const itemIndex = items.findIndex(i => i.item_id === itemId);
+    if (itemIndex >= 0) {
+      return { queue, item: items[itemIndex], itemIndex };
+    }
+  }
+
+  // Search all other queues
+  for (const queueEntry of index.queues) {
+    if (activeQueueIds.includes(queueEntry.id)) continue;
+    const queue = readQueue(queueEntry.id);
+    if (!queue) continue;
+    const items = queue.solutions || queue.tasks || [];
+    const itemIndex = items.findIndex(i => i.item_id === itemId);
+    if (itemIndex >= 0) {
+      return { queue, item: items[itemIndex], itemIndex };
+    }
+  }
+
+  return null;
+}
+
+/**
+ * Get all active queues ordered by priority (lower = higher priority)
+ * Falls back to creation date order
+ */
+function getActiveQueues(): Queue[] {
+  const index = readQueueIndex();
+  const activeIds = index.active_queue_ids || (index.active_queue_id ? [index.active_queue_id] : []);
+
+  const queues: Queue[] = [];
+  for (const queueId of activeIds) {
+    const queue = readQueue(queueId);
+    if (queue && queue.status === 'active') {
+      queues.push(queue);
+    }
+  }
+
+  // Sort by priority field in index (lower = higher priority)
+  const priorityMap = new Map<string, number>();
+  for (const entry of index.queues) {
+    priorityMap.set(entry.id, entry.priority ?? Number.MAX_SAFE_INTEGER);
+  }
+
+  queues.sort((a, b) => {
+    const pa = priorityMap.get(a.id) ?? Number.MAX_SAFE_INTEGER;
+    const pb = priorityMap.get(b.id) ?? Number.MAX_SAFE_INTEGER;
+    if (pa !== pb) return pa - pb;
+    // Fall back to creation date (from queue ID)
+    return a.id.localeCompare(b.id);
+  });
+
+  return queues;
+}
+
+/**
+ * Parse failure reason into structured FailureDetail
+ * Detects JSON format vs plain string
+ */
+function parseFailureReason(reason: string): FailureDetail {
+  const timestamp = new Date().toISOString();
+
+  // Try to parse as JSON first
+  if (reason.trim().startsWith('{')) {
+    try {
+      const parsed = JSON.parse(reason);
+      return {
+        task_id: parsed.task_id,
+        error_type: parsed.error_type || 'unknown',
+        message: parsed.message || reason,
+        stack_trace: parsed.stack_trace,
+        timestamp
+      };
+    } catch {
+      // Not valid JSON, treat as plain message
+    }
+  }
+
+  // Plain string message
+  return {
+    error_type: 'execution_error',
+    message: reason,
+    timestamp
+  };
+}
+
 function writeQueue(queue: Queue): void {
   ensureQueuesDir();
 
@@ -1323,15 +1450,82 @@ async function queueAction(subAction: string | undefined, issueId: string | unde
 
     const index = readQueueIndex();
     index.active_queue_id = queueId;
+    // Also update active_queue_ids for multi-queue support
+    index.active_queue_ids = [queueId];
     writeQueueIndex(index);
 
     console.log(chalk.green(`✓ Switched to queue ${queueId}`));
     return;
   }
 
+  // Set queue priority (lower = higher priority)
+  if (subAction === 'priority' && issueId) {
+    const queueId = issueId;
+    const priority = parseInt(options.priority || '0');
+
+    if (isNaN(priority)) {
+      console.error(chalk.red('Invalid priority value (must be a number)'));
+      process.exit(1);
+    }
+
+    const index = readQueueIndex();
+    const queueEntry = index.queues.find(q => q.id === queueId);
+
+    if (!queueEntry) {
+      console.error(chalk.red(`Queue "${queueId}" not found`));
+      process.exit(1);
+    }
+
+    queueEntry.priority = priority;
+    writeQueueIndex(index);
+
+    console.log(chalk.green(`✓ Queue ${queueId} priority set to ${priority}`));
+    return;
+  }
+
+  // Activate multiple queues at once
+  if (subAction === 'activate' && issueId) {
+    const queueIds = issueId.split(',').map(id => id.trim());
+    const index = readQueueIndex();
+
+    // Validate all queue IDs
+    for (const queueId of queueIds) {
+      if (!index.queues.some(q => q.id === queueId)) {
+        console.error(chalk.red(`Queue "${queueId}" not found`));
+        process.exit(1);
+      }
+    }
+
+    index.active_queue_ids = queueIds;
+    index.active_queue_id = queueIds[0] || null; // Backward compat
+    writeQueueIndex(index);
+
+    console.log(chalk.green(`✓ Activated ${queueIds.length} queue(s): ${queueIds.join(', ')}`));
+    return;
+  }
+
   // DAG - Return dependency graph for parallel execution planning (solution-level)
   if (subAction === 'dag') {
-    const queue = readActiveQueue();
+    let queue: Queue;
+
+    // Use explicit queue if provided via --queue or issueId, otherwise use active queue
+    if (options.queue) {
+      const targetQueue = readQueue(options.queue);
+      if (!targetQueue) {
+        console.log(JSON.stringify({ error: `Queue ${options.queue} not found`, nodes: [], edges: [], groups: [] }));
+        return;
+      }
+      queue = targetQueue;
+    } else if (issueId && issueId.startsWith('QUE-')) {
+      const targetQueue = readQueue(issueId);
+      if (!targetQueue) {
+        console.log(JSON.stringify({ error: `Queue ${issueId} not found`, nodes: [], edges: [], groups: [] }));
+        return;
+      }
+      queue = targetQueue;
+    } else {
+      queue = readActiveQueue();
+    }
 
     // Support both old (tasks) and new (solutions) queue format
     const items = queue.solutions || queue.tasks || [];
@@ -1648,12 +1842,26 @@ async function queueAction(subAction: string | undefined, issueId: string | unde
       ? String(item.task_count || 0).padEnd(8)
       : (item.task_id || '-').padEnd(8);
 
-    console.log(
-      item.item_id.padEnd(10) +
+    let line = item.item_id.padEnd(10) +
       item.issue_id.substring(0, 13).padEnd(15) +
       thirdCol +
-      statusColor(item.status)
-    );
+      statusColor(item.status);
+
+    // Show failure reason for failed items
+    if (item.status === 'failed') {
+      const reason = item.failure_details?.message || item.failure_reason;
+      if (reason) {
+        // Truncate to 40 chars for display
+        const shortReason = reason.length > 40 ? reason.substring(0, 37) + '...' : reason;
+        line += chalk.gray(` [${shortReason}]`);
+      }
+      // Show retry count if there's failure history
+      if (item.failure_history && item.failure_history.length > 0) {
+        line += chalk.gray(` (${item.failure_history.length} retry)`);
+      }
+    }
+
+    console.log(line);
   }
 }
 
@@ -1662,17 +1870,58 @@ async function queueAction(subAction: string | undefined, issueId: string | unde
  * Accepts optional item_id to fetch a specific task directly
  */
 async function nextAction(itemId: string | undefined, options: IssueOptions): Promise<void> {
-  const queue = readActiveQueue();
-  // Support both old (tasks) and new (solutions) queue format
-  const items = queue.solutions || queue.tasks || [];
-  let nextItem: typeof items[0] | undefined;
+  let queue: Queue;
+  let items: QueueItem[];
+
+  // Determine which queue(s) to use
+  if (options.queue) {
+    // Explicit queue specified
+    const targetQueue = readQueue(options.queue);
+    if (!targetQueue) {
+      console.log(JSON.stringify({ status: 'error', message: `Queue ${options.queue} not found` }));
+      return;
+    }
+    queue = targetQueue;
+    items = queue.solutions || queue.tasks || [];
+  } else {
+    // Multi-queue: iterate active queues in priority order (serialized execution)
+    const activeQueues = getActiveQueues();
+
+    if (activeQueues.length === 0) {
+      console.log(JSON.stringify({ status: 'empty', message: 'No active queues' }));
+      return;
+    }
+
+    // Find first queue with incomplete items (serialized: complete Q1 before Q2)
+    let foundQueue: Queue | null = null;
+    for (const q of activeQueues) {
+      const queueItems = q.solutions || q.tasks || [];
+      const hasIncomplete = queueItems.some(i =>
+        i.status === 'pending' || i.status === 'executing'
+      );
+      if (hasIncomplete) {
+        foundQueue = q;
+        break;
+      }
+    }
+
+    if (!foundQueue) {
+      console.log(JSON.stringify({ status: 'empty', message: 'All queues completed' }));
+      return;
+    }
+
+    queue = foundQueue;
+    items = queue.solutions || queue.tasks || [];
+  }
+
+  let nextItem: QueueItem | undefined;
   let isResume = false;
 
   // If specific item_id provided, fetch that item directly
   if (itemId) {
     nextItem = items.find(t => t.item_id === itemId);
     if (!nextItem) {
-      console.log(JSON.stringify({ status: 'error', message: `Item ${itemId} not found` }));
+      console.log(JSON.stringify({ status: 'error', message: `Item ${itemId} not found in queue ${queue.id}` }));
       return;
     }
     if (nextItem.status === 'completed') {
@@ -1701,6 +1950,7 @@ async function nextAction(itemId: string | undefined, options: IssueOptions): Pr
       console.log(JSON.stringify({
         status: 'empty',
         message: 'No ready items',
+        queue_id: queue.id,
         queue_status: queue._metadata
       }, null, 2));
       return;
@@ -1748,6 +1998,7 @@ async function nextAction(itemId: string | undefined, options: IssueOptions): Pr
   const totalMinutes = solution.tasks?.reduce((sum, t) => sum + (t.estimated_minutes || 30), 0) || 30;
 
   console.log(JSON.stringify({
+    queue_id: queue.id,
     item_id: nextItem.item_id,
     issue_id: nextItem.issue_id,
     solution_id: nextItem.solution_id,
@@ -1783,10 +2034,30 @@ async function detailAction(itemId: string | undefined, options: IssueOptions):
     return;
   }
 
-  const queue = readActiveQueue();
-  // Support both old (tasks) and new (solutions) queue format
-  const items = queue.solutions || queue.tasks || [];
-  const queueItem = items.find(t => t.item_id === itemId);
+  let queue: Queue;
+  let queueItem: QueueItem | undefined;
+
+  // Use explicit queue if provided, otherwise auto-detect
+  if (options.queue) {
+    const targetQueue = readQueue(options.queue);
+    if (!targetQueue) {
+      console.log(JSON.stringify({ status: 'error', message: `Queue ${options.queue} not found` }));
+      return;
+    }
+    queue = targetQueue;
+    const items = queue.solutions || queue.tasks || [];
+    queueItem = items.find(t => t.item_id === itemId);
+  } else {
+    // Auto-detect queue from item ID
+    const found = findItemQueue(itemId);
+    if (found) {
+      queue = found.queue;
+      queueItem = found.item;
+    } else {
+      console.log(JSON.stringify({ status: 'error', message: `Item ${itemId} not found in any queue` }));
+      return;
+    }
+  }
 
   if (!queueItem) {
     console.log(JSON.stringify({ status: 'error', message: `Item ${itemId} not found` }));
@@ -1806,6 +2077,7 @@ async function detailAction(itemId: string | undefined, options: IssueOptions):
 
   // Return FULL SOLUTION with all tasks (READ-ONLY - no status update)
   console.log(JSON.stringify({
+    queue_id: queue.id,
     item_id: queueItem.item_id,
     issue_id: queueItem.issue_id,
     solution_id: queueItem.solution_id,
@@ -1827,21 +2099,41 @@ async function detailAction(itemId: string | undefined, options: IssueOptions):
 /**
  * done - Mark task completed or failed
  */
-async function doneAction(queueId: string | undefined, options: IssueOptions): Promise<void> {
-  if (!queueId) {
+async function doneAction(queueItemId: string | undefined, options: IssueOptions): Promise<void> {
+  if (!queueItemId) {
     console.error(chalk.red('Item ID is required'));
-    console.error(chalk.gray('Usage: ccw issue done <item-id> [--fail] [--reason "..."]'));
+    console.error(chalk.gray('Usage: ccw issue done <item-id> [--fail] [--reason "..."] [--queue <queue-id>]'));
     process.exit(1);
   }
 
-  const queue = readActiveQueue();
-  // Support both old (tasks) and new (solutions) queue format
-  const items = queue.solutions || queue.tasks || [];
-  const idx = items.findIndex(q => q.item_id === queueId);
+  let queue: Queue;
+  let items: QueueItem[];
+  let idx: number;
 
-  if (idx === -1) {
-    console.error(chalk.red(`Queue item "${queueId}" not found`));
-    process.exit(1);
+  // Use explicit queue if provided, otherwise auto-detect
+  if (options.queue) {
+    const targetQueue = readQueue(options.queue);
+    if (!targetQueue) {
+      console.error(chalk.red(`Queue "${options.queue}" not found`));
+      process.exit(1);
+    }
+    queue = targetQueue;
+    items = queue.solutions || queue.tasks || [];
+    idx = items.findIndex(q => q.item_id === queueItemId);
+    if (idx === -1) {
+      console.error(chalk.red(`Queue item "${queueItemId}" not found in queue ${options.queue}`));
+      process.exit(1);
+    }
+  } else {
+    // Auto-detect queue from item ID
+    const found = findItemQueue(queueItemId);
+    if (!found) {
+      console.error(chalk.red(`Queue item "${queueItemId}" not found in any queue`));
+      process.exit(1);
+    }
+    queue = found.queue;
+    items = queue.solutions || queue.tasks || [];
+    idx = found.itemIndex;
   }
 
   const isFail = options.fail;
@@ -1849,7 +2141,9 @@ async function doneAction(queueId: string | undefined, options: IssueOptions): P
   items[idx].completed_at = new Date().toISOString();
 
   if (isFail) {
-    items[idx].failure_reason = options.reason || 'Unknown failure';
+    const reason = options.reason || 'Unknown failure';
+    items[idx].failure_reason = reason;  // Backward compat
+    items[idx].failure_details = parseFailureReason(reason);  // Structured failure
   } else if (options.result) {
     try {
       items[idx].result = JSON.parse(options.result);
@@ -1863,10 +2157,10 @@ async function doneAction(queueId: string | undefined, options: IssueOptions): P
 
   if (isFail) {
     updateIssue(issueId, { status: 'failed' });
-    console.log(chalk.red(`✗ ${queueId} failed`));
+    console.log(chalk.red(`✗ ${queueItemId} failed`));
   } else {
     updateIssue(issueId, { status: 'completed', completed_at: new Date().toISOString() });
-    console.log(chalk.green(`✓ ${queueId} completed`));
+    console.log(chalk.green(`✓ ${queueItemId} completed`));
     console.log(chalk.green(`✓ Issue ${issueId} completed`));
   }
 
@@ -1895,53 +2189,81 @@ async function doneAction(queueId: string | undefined, options: IssueOptions): P
  * retry - Reset failed items to pending for re-execution
  */
 async function retryAction(issueId: string | undefined, options: IssueOptions): Promise<void> {
-  const queue = readActiveQueue();
-  // Support both old (tasks) and new (solutions) queue format
-  const items = queue.solutions || queue.tasks || [];
+  let queues: Queue[];
 
-  if (!queue.id || items.length === 0) {
-    console.log(chalk.yellow('No active queue'));
+  // Use explicit queue if provided, otherwise use all active queues
+  if (options.queue) {
+    const targetQueue = readQueue(options.queue);
+    if (!targetQueue) {
+      console.log(chalk.red(`Queue "${options.queue}" not found`));
+      return;
+    }
+    queues = [targetQueue];
+  } else {
+    queues = getActiveQueues();
+  }
+
+  if (queues.length === 0) {
+    console.log(chalk.yellow('No active queues'));
     return;
   }
 
-  let updated = 0;
+  let totalUpdated = 0;
 
-  for (const item of items) {
-    // Retry failed items only
-    if (item.status === 'failed') {
-      if (!issueId || item.issue_id === issueId) {
-        item.status = 'pending';
-        item.failure_reason = undefined;
-        item.started_at = undefined;
-        item.completed_at = undefined;
-        updated++;
+  for (const queue of queues) {
+    const items = queue.solutions || queue.tasks || [];
+    let queueUpdated = 0;
+
+    for (const item of items) {
+      // Retry failed items only
+      if (item.status === 'failed') {
+        if (!issueId || item.issue_id === issueId) {
+          // Preserve failure history before resetting
+          if (item.failure_details) {
+            if (!item.failure_history) {
+              item.failure_history = [];
+            }
+            item.failure_history.push(item.failure_details);
+          }
+
+          // Reset for retry
+          item.status = 'pending';
+          item.failure_reason = undefined;
+          item.failure_details = undefined;
+          item.started_at = undefined;
+          item.completed_at = undefined;
+          queueUpdated++;
+        }
       }
     }
+
+    if (queueUpdated > 0) {
+      // Reset queue status if it was failed
+      if (queue.status === 'failed') {
+        queue.status = 'active';
+      }
+
+      // Write back to queue
+      if (queue.solutions) {
+        queue.solutions = items;
+      } else {
+        queue.tasks = items;
+      }
+      writeQueue(queue);
+      totalUpdated += queueUpdated;
+    }
   }
 
-  if (updated === 0) {
+  if (totalUpdated === 0) {
     console.log(chalk.yellow('No failed items to retry'));
     return;
   }
 
-  // Reset queue status if it was failed
-  if (queue.status === 'failed') {
-    queue.status = 'active';
-  }
-
-  // Write back to queue
-  if (queue.solutions) {
-    queue.solutions = items;
-  } else {
-    queue.tasks = items;
-  }
-  writeQueue(queue);
-
   if (issueId) {
     updateIssue(issueId, { status: 'queued' });
   }
 
-  console.log(chalk.green(`✓ Reset ${updated} item(s) to pending`));
+  console.log(chalk.green(`✓ Reset ${totalUpdated} item(s) to pending (failure history preserved)`));
 }
 
 // ============ Main Entry ============
@@ -2025,16 +2347,18 @@ export async function issueCommand(
       console.log(chalk.gray('  queue list                         List all queues (history)'));
       console.log(chalk.gray('  queue add <issue-id>               Add issue to active queue (or create new)'));
       console.log(chalk.gray('  queue switch <queue-id>            Switch active queue'));
-      console.log(chalk.gray('  queue dag                          Get dependency graph (JSON) for parallel execution'));
+      console.log(chalk.gray('  queue activate <q1,q2,...>         Activate multiple queues (comma-separated)'));
+      console.log(chalk.gray('  queue priority <queue-id>          Set queue priority (--priority N, lower=higher)'));
+      console.log(chalk.gray('  queue dag [--queue <id>]           Get dependency graph (JSON) for parallel execution'));
       console.log(chalk.gray('  queue archive                      Archive current queue'));
       console.log(chalk.gray('  queue delete <queue-id>            Delete queue from history'));
-      console.log(chalk.gray('  retry [issue-id]                   Retry failed tasks'));
+      console.log(chalk.gray('  retry [issue-id] [--queue <id>]    Retry failed tasks'));
       console.log();
       console.log(chalk.bold('Execution Endpoints:'));
-      console.log(chalk.gray('  next [item-id]                     Get & mark task executing (JSON)'));
-      console.log(chalk.gray('  detail <item-id>                   Get task details (READ-ONLY, for parallel)'));
-      console.log(chalk.gray('  done <item-id>                     Mark task completed'));
-      console.log(chalk.gray('  done <item-id> --fail              Mark task failed'));
+      console.log(chalk.gray('  next [item-id] [--queue <id>]      Get & mark task executing (JSON)'));
+      console.log(chalk.gray('  detail <item-id> [--queue <id>]    Get task details (READ-ONLY, for parallel)'));
+      console.log(chalk.gray('  done <item-id> [--queue <id>]      Mark task completed'));
+      console.log(chalk.gray('  done <item-id> --fail --reason "." Mark task failed with reason (supports JSON)'));
       console.log();
       console.log(chalk.bold('Options:'));
       console.log(chalk.gray('  --title <title>                    Issue/task title'));
@@ -2042,7 +2366,9 @@ export async function issueCommand(
       console.log(chalk.gray('  --brief                            Brief JSON output (minimal fields)'));
       console.log(chalk.gray('  --solution <path>                  Solution JSON file'));
       console.log(chalk.gray('  --result <json>                    Execution result'));
-      console.log(chalk.gray('  --reason <text>                    Failure reason'));
+      console.log(chalk.gray('  --reason <text>                    Failure reason (string or JSON)'));
+      console.log(chalk.gray('  --queue <queue-id>                 Target queue for multi-queue operations'));
+      console.log(chalk.gray('  --priority <n>                     Queue priority (lower = higher)'));
       console.log(chalk.gray('  --json                             JSON output'));
       console.log(chalk.gray('  --force                            Force operation'));
       console.log();