Add documentation for new CLI commands: docs-related-cli and lite-fix

- Implemented the `docs-related-cli` command for context-aware documentation generation and update for changed modules using CLI execution with tool fallback. - Introduced the `lite-fix` command for lightweight bug diagnosis and fix workflow, featuring intelligent severity assessment and optional hotfix mode for production incidents.
2026-02-14 02:42:04 +08:00 · 2025-11-23 22:18:39 +08:00
parent 4bb4bdc124
commit 7453987cfe
76 changed files with 3848 additions and 2013 deletions
--- a/.claude/skills/command-guide/reference/commands/workflow/lite-fix.md
+++ b/.claude/skills/command-guide/reference/commands/workflow/lite-fix.md
@@ -0,0 +1,760 @@
+---
+name: lite-fix
+description: Lightweight bug diagnosis and fix workflow with intelligent severity assessment and optional hotfix mode for production incidents
+argument-hint: "[--hotfix] \"bug description or issue reference\""
+allowed-tools: TodoWrite(*), Task(*), SlashCommand(*), AskUserQuestion(*), Read(*), Bash(*)
+---
+
+# Workflow Lite-Fix Command (/workflow:lite-fix)
+
+## Overview
+
+Fast-track bug fixing workflow optimized for quick diagnosis, targeted fixes, and streamlined verification. Automatically adjusts process complexity based on impact assessment.
+
+**Core capabilities:**
+- Rapid root cause diagnosis with intelligent code search
+- Automatic severity assessment and adaptive workflow
+- Fix strategy selection (immediate patch vs comprehensive refactor)
+- Risk-aware verification (smoke tests to full suite)
+- Optional hotfix mode for production incidents with branch management
+- Automatic follow-up task generation for hotfixes
+
+## Usage
+
+### Command Syntax
+```bash
+/workflow:lite-fix [FLAGS] <BUG_DESCRIPTION>
+
+# Flags
+--hotfix, -h               Production hotfix mode (creates hotfix branch, auto follow-up)
+
+# Arguments
+<bug-description>          Bug description or issue reference (required)
+```
+
+### Modes
+
+| Mode | Time Budget | Use Case | Workflow Characteristics |
+|------|-------------|----------|--------------------------|
+| **Default** | Auto-adapt (15min-4h) | All standard bugs | Intelligent severity assessment + adaptive process |
+| **Hotfix** (`--hotfix`) | 15-30 min | Production outage | Minimal diagnosis + hotfix branch + auto follow-up |
+
+### Examples
+
+```bash
+# Default mode: Automatically adjusts based on impact
+/workflow:lite-fix "User avatar upload fails with 413 error"
+/workflow:lite-fix "Shopping cart randomly loses items at checkout"
+
+# Hotfix mode: Production incident
+/workflow:lite-fix --hotfix "Payment gateway 5xx errors"
+```
+
+## Execution Process
+
+### Workflow Overview
+
+```
+Bug Input → Diagnosis (Phase 1) → Impact Assessment (Phase 2)
+        ↓
+    Severity Auto-Detection → Fix Planning (Phase 3)
+        ↓
+    Verification Strategy (Phase 4) → User Confirmation (Phase 5) → Execution (Phase 6)
+```
+
+### Phase Summary
+
+| Phase | Default Mode | Hotfix Mode |
+|-------|--------------|-------------|
+| 1. Diagnosis | Adaptive search depth | Minimal (known issue) |
+| 2. Impact Assessment | Full risk scoring | Critical path only |
+| 3. Fix Planning | Strategy options based on complexity | Single surgical fix |
+| 4. Verification | Test level matches risk score | Smoke tests only |
+| 5. User Confirmation | 3 dimensions | 2 dimensions |
+| 6. Execution | Via lite-execute | Via lite-execute + monitoring |
+
+---
+
+## Detailed Phase Execution
+
+### Phase 1: Diagnosis & Root Cause Analysis
+
+**Goal**: Identify root cause and affected code paths
+
+**Session Folder Setup**:
+```javascript
+// Generate session identifiers for artifact storage
+const bugSlug = bug_description.toLowerCase().replace(/[^a-z0-9]+/g, '-').substring(0, 40)
+const timestamp = new Date().toISOString().replace(/[:.]/g, '-')
+const shortTimestamp = timestamp.substring(0, 19).replace('T', '-') // YYYY-MM-DD-HH-mm-ss
+const sessionId = `${bugSlug}-${shortTimestamp}`
+const sessionFolder = `.workflow/.lite-fix/${sessionId}`
+```
+
+**Execution Strategy**:
+
+**Default Mode** - Adaptive search:
+- **High confidence keywords** (e.g., specific error messages): Direct grep search (5min)
+- **Medium confidence**: cli-explore-agent with focused search (10-15min)
+- **Low confidence** (vague symptoms): cli-explore-agent with broad search (20min)
+
+```javascript
+// Confidence-based strategy selection
+if (has_specific_error_message || has_file_path_hint) {
+  // Quick targeted search
+  grep -r '${error_message}' src/ --include='*.ts' -n | head -10
+  git log --oneline --since='1 week ago' -- '*affected*'
+} else {
+  // Deep exploration
+  Task(subagent_type="cli-explore-agent", prompt=`
+    Bug: ${bug_description}
+    Execute diagnostic search:
+    1. Search error patterns and similar issues
+    2. Trace execution path in affected modules
+    3. Check recent changes
+    Return: Root cause hypothesis, affected paths, reproduction steps
+  `)
+}
+```
+
+**Hotfix Mode** - Minimal search:
+```bash
+Read(suspected_file)  # User typically knows the file
+git blame ${suspected_file}
+```
+
+**Output Structure**:
+```javascript
+diagnosisContext = {
+  symptom: string,
+  error_message: string | null,
+  keywords: string[],
+  confidence_level: "high" | "medium" | "low",
+  root_cause: {
+    file: "src/auth/tokenValidator.ts",
+    line_range: "45-52",
+    issue: "Token expiration check uses wrong comparison",
+    introduced_by: "commit abc123"
+  },
+  reproduction_steps: ["Login", "Wait 15min", "Access protected route"],
+  affected_scope: {
+    users: "All authenticated users",
+    features: ["login", "API access"],
+    data_risk: "none"
+  }
+}
+
+// Save diagnosis results for CLI/agent access in lite-execute
+const diagnosisFile = `${sessionFolder}/diagnosis.json`
+Write(diagnosisFile, JSON.stringify(diagnosisContext, null, 2))
+```
+
+**Output**: `diagnosisContext` (in-memory)
+**Artifact**: Saved to `{sessionFolder}/diagnosis.json` for CLI/agent use
+
+**TodoWrite**: Mark Phase 1 completed, Phase 2 in_progress
+
+---
+
+### Phase 2: Impact Assessment & Severity Auto-Detection
+
+**Goal**: Quantify blast radius and auto-determine severity
+
+**Risk Score Calculation**:
+```javascript
+risk_score = (user_impact × 0.4) + (system_risk × 0.3) + (business_impact × 0.3)
+
+// Auto-severity mapping
+if (risk_score >= 8.0) severity = "critical"
+else if (risk_score >= 5.0) severity = "high"
+else if (risk_score >= 3.0) severity = "medium"
+else severity = "low"
+
+// Workflow adaptation
+if (severity >= "high") {
+  diagnosis_depth = "focused"
+  test_strategy = "smoke_and_critical"
+  review_optional = true
+} else {
+  diagnosis_depth = "comprehensive"
+  test_strategy = "full_suite"
+  review_optional = false
+}
+```
+
+**Assessment Output**:
+```javascript
+impactContext = {
+  affected_users: {
+    count: "5000 active users (100%)",
+    severity: "high"
+  },
+  system_risk: {
+    availability: "degraded_30%",
+    cascading_failures: "possible_logout_storm"
+  },
+  business_impact: {
+    revenue: "medium",
+    reputation: "high",
+    sla_breach: "yes"
+  },
+  risk_score: 7.1,
+  severity: "high",
+  workflow_adaptation: {
+    test_strategy: "focused_integration",
+    review_required: false,
+    time_budget: "1_hour"
+  }
+}
+
+// Save impact assessment for CLI/agent access
+const impactFile = `${sessionFolder}/impact.json`
+Write(impactFile, JSON.stringify(impactContext, null, 2))
+```
+
+**Output**: `impactContext` (in-memory)
+**Artifact**: Saved to `{sessionFolder}/impact.json` for CLI/agent use
+
+**Hotfix Mode**: Skip detailed assessment, assume critical
+
+**TodoWrite**: Mark Phase 2 completed, Phase 3 in_progress
+
+---
+
+### Phase 3: Fix Planning & Strategy Selection
+
+**Goal**: Generate fix options with trade-off analysis
+
+**Strategy Generation**:
+
+**Default Mode** - Complexity-adaptive:
+- **Low risk score (<5.0)**: Generate 2-3 strategy options for user selection
+- **High risk score (≥5.0)**: Generate single best strategy for speed
+
+```javascript
+strategies = generateFixStrategies(root_cause, risk_score)
+
+if (risk_score >= 5.0 || mode === "hotfix") {
+  // Single best strategy
+  return strategies[0]  // Fastest viable fix
+} else {
+  // Multiple options with trade-offs
+  return strategies  // Let user choose
+}
+```
+
+**Example Strategies**:
+```javascript
+// Low risk: Multiple options
+[
+  {
+    strategy: "immediate_patch",
+    description: "Fix comparison operator",
+    estimated_time: "15 minutes",
+    risk: "low",
+    pros: ["Quick fix"],
+    cons: ["Doesn't address underlying issue"]
+  },
+  {
+    strategy: "comprehensive_fix",
+    description: "Refactor token validation logic",
+    estimated_time: "2 hours",
+    risk: "medium",
+    pros: ["Addresses root cause"],
+    cons: ["Longer implementation"]
+  }
+]
+
+// High risk or hotfix: Single option
+{
+  strategy: "surgical_fix",
+  description: "Minimal change to fix comparison",
+  files: ["src/auth/tokenValidator.ts:47"],
+  estimated_time: "5 minutes",
+  risk: "minimal"
+}
+```
+
+**Complexity Assessment**:
+```javascript
+if (complexity === "high" && risk_score < 5.0) {
+  suggestCommand("/workflow:plan --mode bugfix")
+  return  // Escalate to full planning
+}
+
+// Save fix plan for CLI/agent access
+const planFile = `${sessionFolder}/fix-plan.json`
+Write(planFile, JSON.stringify(fixPlan, null, 2))
+```
+
+**Output**: `fixPlan` (in-memory)
+**Artifact**: Saved to `{sessionFolder}/fix-plan.json` for CLI/agent use
+
+**TodoWrite**: Mark Phase 3 completed, Phase 4 in_progress
+
+---
+
+### Phase 4: Verification Strategy
+
+**Goal**: Define testing approach based on severity
+
+**Adaptive Test Strategy**:
+
+| Risk Score | Test Scope | Duration | Automation |
+|------------|------------|----------|------------|
+| **< 3.0** (Low) | Full test suite | 15-20 min | `npm test` |
+| **3.0-5.0** (Medium) | Focused integration | 8-12 min | `npm test -- affected-module.test.ts` |
+| **5.0-8.0** (High) | Smoke + critical | 5-8 min | `npm test -- critical.smoke.test.ts` |
+| **≥ 8.0** (Critical) | Smoke only | 2-5 min | `npm test -- smoke.test.ts` |
+| **Hotfix** | Production smoke | 2-3 min | `npm test -- production.smoke.test.ts` |
+
+**Branch Strategy**:
+
+**Default Mode**:
+```javascript
+{
+  type: "feature_branch",
+  base: "main",
+  name: "fix/token-expiration-edge-case",
+  merge_target: "main"
+}
+```
+
+**Hotfix Mode**:
+```javascript
+{
+  type: "hotfix_branch",
+  base: "production_tag_v2.3.1",  // ⚠️ From production tag
+  name: "hotfix/token-validation-fix",
+  merge_target: ["main", "production"]  // Dual merge
+}
+```
+
+**TodoWrite**: Mark Phase 4 completed, Phase 5 in_progress
+
+---
+
+### Phase 5: User Confirmation & Execution Selection
+
+**Adaptive Confirmation Dimensions**:
+
+**Default Mode** - 3 dimensions (adapted by risk score):
+
+```javascript
+dimensions = [
+  {
+    question: "Confirm fix approach?",
+    options: ["Proceed", "Modify", "Escalate to /workflow:plan"]
+  },
+  {
+    question: "Execution method:",
+    options: ["Agent", "CLI Tool (Codex/Gemini)", "Manual (plan only)"]
+  },
+  {
+    question: "Verification level:",
+    options: adaptedByRiskScore()  // Auto-suggest based on Phase 2
+  }
+]
+
+// If risk_score >= 5.0, auto-skip code review dimension
+// If risk_score < 5.0, add optional code review dimension
+if (risk_score < 5.0) {
+  dimensions.push({
+    question: "Post-fix review:",
+    options: ["Gemini", "Skip"]
+  })
+}
+```
+
+**Hotfix Mode** - 2 dimensions (minimal):
+```javascript
+[
+  {
+    question: "Confirm hotfix deployment:",
+    options: ["Deploy", "Stage First", "Abort"]
+  },
+  {
+    question: "Post-deployment monitoring:",
+    options: ["Real-time (15 min)", "Passive (alerts only)"]
+  }
+]
+```
+
+**TodoWrite**: Mark Phase 5 completed, Phase 6 in_progress
+
+---
+
+### Phase 6: Execution Dispatch & Follow-up
+
+**Export Enhanced Task JSON**:
+
+```javascript
+const taskId = `BUGFIX-${shortTimestamp}`
+const taskFile = `${sessionFolder}/task.json`
+
+const enhancedTaskJson = {
+  id: taskId,
+  title: bug_description,
+  status: "pending",
+
+  meta: {
+    type: "bugfix",
+    created_at: new Date().toISOString(),
+    severity: impactContext.severity,
+    risk_score: impactContext.risk_score,
+    estimated_time: fixPlan.estimated_time,
+    workflow: mode === "hotfix" ? "lite-fix-hotfix" : "lite-fix",
+    session_id: sessionId,
+    session_folder: sessionFolder
+  },
+
+  context: {
+    requirements: [bug_description],
+    diagnosis: diagnosisContext,
+    impact: impactContext,
+    plan: fixPlan,
+    verification_strategy: verificationStrategy,
+    branch_strategy: branchStrategy
+  }
+}
+
+Write(taskFile, JSON.stringify(enhancedTaskJson, null, 2))
+```
+
+**Dispatch to lite-execute**:
+
+```javascript
+executionContext = {
+  mode: "bugfix",
+  severity: impactContext.severity,
+  planObject: fixPlan,
+  diagnosisContext: diagnosisContext,
+  impactContext: impactContext,
+  verificationStrategy: verificationStrategy,
+  branchStrategy: branchStrategy,
+  executionMethod: user_selection.execution_method,
+
+  // Session artifacts location
+  session: {
+    id: sessionId,
+    folder: sessionFolder,
+    artifacts: {
+      diagnosis: `${sessionFolder}/diagnosis.json`,
+      impact: `${sessionFolder}/impact.json`,
+      plan: `${sessionFolder}/fix-plan.json`,
+      task: `${sessionFolder}/task.json`
+    }
+  }
+}
+
+SlashCommand("/workflow:lite-execute --in-memory --mode bugfix")
+```
+
+**Hotfix Auto Follow-up**:
+
+```javascript
+if (mode === "hotfix") {
+  follow_up_tasks = [
+    {
+      id: `FOLLOWUP-${taskId}-comprehensive`,
+      title: "Replace hotfix with comprehensive fix",
+      priority: "high",
+      due_date: "within_3_days",
+      description: "Refactor quick hotfix into proper solution with full test coverage"
+    },
+    {
+      id: `FOLLOWUP-${taskId}-postmortem`,
+      title: "Incident postmortem",
+      priority: "medium",
+      due_date: "within_1_week",
+      sections: ["Timeline", "Root cause", "Prevention measures"]
+    }
+  ]
+
+  Write(`${sessionFolder}/followup.json`, follow_up_tasks)
+
+  console.log(`
+  ⚠️ Hotfix follow-up tasks generated:
+  - Comprehensive fix: ${follow_up_tasks[0].id} (due in 3 days)
+  - Postmortem: ${follow_up_tasks[1].id} (due in 1 week)
+  - Location: ${sessionFolder}/followup.json
+  `)
+}
+}
+```
+
+**TodoWrite**: Mark Phase 6 completed
+
+---
+
+## Data Structures
+
+### diagnosisContext
+```javascript
+{
+  symptom: string,
+  error_message: string | null,
+  keywords: string[],
+  confidence_level: "high" | "medium" | "low",  // Search confidence
+  root_cause: {
+    file: string,
+    line_range: string,
+    issue: string,
+    introduced_by: string
+  },
+  reproduction_steps: string[],
+  affected_scope: {...}
+}
+```
+
+### impactContext
+```javascript
+{
+  affected_users: { count: string, severity: string },
+  system_risk: { availability: string, cascading_failures: string },
+  business_impact: { revenue: string, reputation: string, sla_breach: string },
+  risk_score: number,  // 0-10
+  severity: "low" | "medium" | "high" | "critical",
+  workflow_adaptation: {
+    diagnosis_depth: string,
+    test_strategy: string,
+    review_optional: boolean,
+    time_budget: string
+  }
+}
+```
+
+### fixPlan
+```javascript
+{
+  strategy: string,
+  summary: string,
+  tasks: [{
+    title: string,
+    file: string,
+    action: "Update" | "Create" | "Delete",
+    implementation: string[],
+    verification: string[]
+  }],
+  estimated_time: string,
+  recommended_execution: "Agent" | "CLI" | "Manual"
+}
+```
+
+### executionContext
+
+Context passed to lite-execute via --in-memory (Phase 6):
+
+```javascript
+{
+  mode: "bugfix",
+  severity: "high" | "medium" | "low" | "critical",
+
+  // Core data objects
+  planObject: {...},           // Complete fixPlan (see above)
+  diagnosisContext: {...},     // Complete diagnosisContext (see above)
+  impactContext: {...},        // Complete impactContext (see above)
+
+  // Verification and branch strategies
+  verificationStrategy: {...},
+  branchStrategy: {...},
+  executionMethod: "Agent" | "CLI" | "Manual",
+
+  // Session artifacts location (for lite-execute to access saved files)
+  session: {
+    id: string,                // Session identifier: {bugSlug}-{shortTimestamp}
+    folder: string,            // Session folder path: .workflow/.lite-fix/{session-id}
+    artifacts: {
+      diagnosis: string,       // diagnosis.json path
+      impact: string,          // impact.json path
+      plan: string,            // fix-plan.json path
+      task: string             // task.json path
+    }
+  }
+}
+```
+
+### Enhanced Task JSON Export
+
+Task JSON structure exported in Phase 6:
+
+```json
+{
+  "id": "BUGFIX-{timestamp}",
+  "title": "Original bug description",
+  "status": "pending",
+
+  "meta": {
+    "type": "bugfix",
+    "created_at": "ISO timestamp",
+    "severity": "low|medium|high|critical",
+    "risk_score": 7.1,
+    "estimated_time": "X minutes",
+    "workflow": "lite-fix|lite-fix-hotfix",
+    "session_id": "{bugSlug}-{shortTimestamp}",
+    "session_folder": ".workflow/.lite-fix/{session-id}"
+  },
+
+  "context": {
+    "requirements": ["Original bug description"],
+    "diagnosis": {/* diagnosisContext */},
+    "impact": {/* impactContext */},
+    "plan": {/* fixPlan */},
+    "verification_strategy": {/* test strategy */},
+    "branch_strategy": {/* branch strategy */}
+  }
+}
+```
+
+**Schema Notes**:
+- Aligns with Enhanced Task JSON Schema (6-field structure)
+- `context_package_path` omitted (not used by lite-fix)
+- `flow_control` omitted (handled by lite-execute)
+
+---
+
+## Best Practices
+
+### When to Use Default Mode
+
+**Use for all standard bugs:**
+- Automatically adapts to severity (no manual mode selection needed)
+- Risk score determines workflow complexity
+- Handles 90% of bug fixing scenarios
+
+**Typical scenarios:**
+- UI bugs, logic errors, edge cases
+- Performance issues (non-critical)
+- Integration failures
+- Data validation bugs
+
+### When to Use Hotfix Mode
+
+**Only use for production incidents:**
+- Production is down or critically degraded
+- Revenue/reputation at immediate risk
+- SLA breach occurring
+- Issue is well-understood (minimal diagnosis needed)
+
+**Hotfix characteristics:**
+- Creates hotfix branch from production tag
+- Minimal diagnosis (assumes known issue)
+- Smoke tests only
+- Auto-generates follow-up tasks
+- Requires incident tracking
+
+### Branching Strategy
+
+**Default Mode (feature branch)**:
+```bash
+# Standard feature branch workflow
+git checkout -b fix/issue-description main
+# ... implement fix
+git checkout main && git merge fix/issue-description
+```
+
+**Hotfix Mode (dual merge)**:
+```bash
+# ✅ Correct: Branch from production tag
+git checkout -b hotfix/fix-name v2.3.1
+
+# Merge to both targets
+git checkout main && git merge hotfix/fix-name
+git checkout production && git merge hotfix/fix-name
+git tag v2.3.2
+
+# ❌ Wrong: Branch from main
+git checkout -b hotfix/fix-name main  # Contains unreleased code!
+```
+
+---
+
+## Error Handling
+
+| Error | Cause | Resolution |
+|-------|-------|------------|
+| Root cause unclear | Vague symptoms | Extend diagnosis time or use /cli:mode:bug-diagnosis |
+| Multiple potential causes | Complex interaction | Use /cli:discuss-plan for analysis |
+| Fix too complex | High-risk refactor | Escalate to /workflow:plan --mode bugfix |
+| High risk score but unsure | Uncertain severity | Default mode will adapt, proceed normally |
+
+---
+
+## Session Folder Structure
+
+Each lite-fix execution creates a dedicated session folder to organize all artifacts:
+
+```
+.workflow/.lite-fix/{bug-slug}-{short-timestamp}/
+├── diagnosis.json    # Phase 1: Root cause analysis
+├── impact.json       # Phase 2: Impact assessment
+├── fix-plan.json     # Phase 3: Fix strategy
+├── task.json         # Phase 6: Enhanced Task JSON
+└── followup.json     # Hotfix mode only: Follow-up tasks
+```
+
+**Folder Naming Convention**:
+- `{bug-slug}`: First 40 characters of bug description, lowercased, non-alphanumeric replaced with `-`
+- `{short-timestamp}`: YYYY-MM-DD-HH-mm-ss format
+- Example: `.workflow/.lite-fix/user-avatar-upload-fails-413-2025-01-15-14-30-45/`
+
+**File Contents**:
+- `diagnosis.json`: Complete diagnosisContext object (Phase 1)
+- `impact.json`: Complete impactContext object (Phase 2)
+- `fix-plan.json`: Complete fixPlan object (Phase 3)
+- `task.json`: Enhanced Task JSON with all context (Phase 6)
+- `followup.json`: Follow-up tasks (hotfix mode only)
+
+**Access Patterns**:
+- **lite-fix**: Creates folder and writes all artifacts during execution, passes paths via `executionContext.session.artifacts`
+- **lite-execute**: Reads artifact paths from `executionContext.session.artifacts`
+- **User**: Can inspect artifacts for debugging or reference
+- **Reuse**: Pass `task.json` path to `/workflow:lite-execute {path}` for re-execution
+
+
+
+**Legacy Cache** (deprecated, use session folder instead):
+```
+.workflow/.lite-fix-cache/
+└── diagnosis-cache/
+    └── ${bug_hash}.json
+```
+
+
+## Quality Gates
+
+**Before execution** (auto-checked):
+- [ ] Root cause identified (>70% confidence for default, >90% for hotfix)
+- [ ] Impact scope defined
+- [ ] Fix strategy reviewed
+- [ ] Verification plan matches risk level
+
+**Hotfix-specific**:
+- [ ] Production tag identified
+- [ ] Rollback plan documented
+- [ ] Follow-up tasks generated
+- [ ] Monitoring configured
+
+---
+
+## When to Use lite-fix
+
+✅ **Perfect for:**
+- Any bug with clear symptoms
+- Localized fixes (1-5 files)
+- Known technology stack
+- Time-sensitive but not catastrophic (default mode adapts)
+- Production incidents (use --hotfix)
+
+❌ **Not suitable for:**
+- Root cause completely unclear → use `/cli:mode:bug-diagnosis` first
+- Requires architectural changes → use `/workflow:plan`
+- Complex legacy code without tests → use `/workflow:plan --legacy-refactor`
+- Performance deep-dive → use `/workflow:plan --performance-optimization`
+- Data migration → use `/workflow:plan --data-migration`
+
+---
+
+**Last Updated**: 2025-11-20
+**Version**: 2.0.0
+**Status**: Design Document (Simplified)