# Team Manager Validation - Complete ✅

## Overview
Added validation to ensure each shift manager can only be assigned to one team at a time.

---

## Features Implemented

### 1. Manager Availability Check ✅

**Create Team Page:**
- Validates that selected manager doesn't already have a team
- Shows error message if manager is already assigned
- Displays team assignments in dropdown options
- Prevents form submission if validation fails

**Edit Team Page:**
- Validates only if manager is being changed
- Allows keeping the same manager (no validation needed)
- Shows error message if new manager is already assigned
- Displays team assignments in dropdown options

---

## Implementation Details

### New API Endpoint
**`GET /api/admin/managers-with-teams`**
- Returns all active managers with their team assignments
- Includes team data for validation
- Used by both create and edit forms

### Validation Logic

**Create Team:**
```typescript
// Check if selected manager already has a team
const selectedManager = managers.find(m => m.id === formData.shiftManagerId)
if (selectedManager && selectedManager.teams && selectedManager.teams.length > 0) {
  setError(`This manager is already assigned to: ${selectedManager.teams.map(t => t.name).join(", ")}`)
  return
}
```

**Edit Team:**
```typescript
// Only check if manager changed
if (formData.shiftManagerId !== originalManagerId) {
  const selectedManager = managers.find(m => m.id === formData.shiftManagerId)
  if (selectedManager && selectedManager.teams && selectedManager.teams.length > 0) {
    setError(`This manager is already assigned to: ${selectedManager.teams.map(t => t.name).join(", ")}`)
    return
  }
}
```

---

## User Experience

### Visual Indicators

**Dropdown Options:**
- Shows manager name and employee number
- Displays existing team assignments inline
- Example: "John Smith (SM001) - Already assigned to: Red Team"

**Error Messages:**
- Red alert box appears when validation fails
- Clear message indicating which team(s) the manager is assigned to
- Error clears when user changes selection

**Form Behavior:**
- Submit button disabled during loading
- Error prevents form submission
- User must select a different manager to proceed

---

## Files Modified

### Pages
1. ✅ `app/admin/teams/create/page.tsx`
   - Added manager validation
   - Added error state
   - Enhanced dropdown with team info

2. ✅ `app/admin/teams/[id]/page.tsx`
   - Added manager validation (only on change)
   - Added error state
   - Enhanced dropdown with team info
   - Tracks original manager ID

### API Routes
1. ✅ `app/api/admin/managers-with-teams/route.ts` (NEW)
   - Returns managers with team relationships
   - Filters active managers only
   - Ordered by employee number

---

## Validation Rules

### One Manager Per Team
- ✅ Each team must have exactly one shift manager
- ✅ Each shift manager can only manage one team
- ✅ Validation happens before form submission
- ✅ Clear error messages guide the user

### Edit Behavior
- ✅ Can keep the same manager (no validation)
- ✅ Can change to unassigned manager (allowed)
- ✅ Cannot change to manager with existing team (blocked)

---

## Testing Scenarios

### Create Team
1. ✅ Select manager without team → Success
2. ✅ Select manager with team → Error shown
3. ✅ Change selection after error → Error clears
4. ✅ Submit with valid manager → Team created

### Edit Team
1. ✅ Keep same manager → Success (no validation)
2. ✅ Change to unassigned manager → Success
3. ✅ Change to manager with team → Error shown
4. ✅ Change back to original → Success

### Dropdown Display
1. ✅ Managers without teams show normally
2. ✅ Managers with teams show assignment info
3. ✅ Current team's manager doesn't show warning (edit only)

---

## Error Messages

### Format
```
This manager is already assigned to: [Team Name(s)]
```

### Examples
- "This manager is already assigned to: Red Team"
- "This manager is already assigned to: Blue Team, Green Team"

---

## Benefits

### Data Integrity
- Prevents duplicate team assignments
- Ensures one-to-one manager-team relationship
- Validates before database operation

### User Experience
- Clear visual feedback
- Helpful error messages
- Prevents invalid submissions
- Shows team assignments in dropdown

### System Reliability
- Client-side validation (fast feedback)
- Can add server-side validation for extra safety
- Consistent validation logic

---

## Future Enhancements

### Possible Additions
- [ ] Server-side validation in API route
- [ ] Show available managers count
- [ ] Filter dropdown to show only available managers
- [ ] Bulk team assignment interface
- [ ] Manager reassignment workflow
- [ ] Team history tracking

---

## Summary

✅ **Validation implemented for team manager assignments**
✅ **One manager per team rule enforced**
✅ **Clear error messages and visual feedback**
✅ **Works in both create and edit forms**
✅ **New API endpoint for manager data with teams**

The system now ensures that each shift manager can only be assigned to one team at a time, preventing conflicts and maintaining data integrity!