interface ScheduleEvent {
  id: string;
  title: string;
  location: string;
  startTime: string;
  endTime: string;
  assignedDriverId?: string;
  vipId: string;
  vipName: string;
}

interface ConflictInfo {
  type: 'overlap' | 'tight_turnaround' | 'back_to_back';
  severity: 'low' | 'medium' | 'high';
  message: string;
  conflictingEvent: ScheduleEvent;
  timeDifference?: number; // minutes
}

interface DriverAvailability {
  driverId: string;
  driverName: string;
  status: 'available' | 'scheduled' | 'overlapping' | 'tight_turnaround';
  assignmentCount: number;
  conflicts: ConflictInfo[];
  currentAssignments: ScheduleEvent[];
}

class DriverConflictService {
  
  // Check for conflicts when assigning a driver to an event
  checkDriverConflicts(
    driverId: string, 
    newEvent: { startTime: string; endTime: string; location: string },
    allSchedules: { [vipId: string]: ScheduleEvent[] },
    drivers: any[]
  ): ConflictInfo[] {
    const conflicts: ConflictInfo[] = [];
    const driver = drivers.find(d => d.id === driverId);
    if (!driver) return conflicts;

    // Get all events assigned to this driver
    const driverEvents = this.getDriverEvents(driverId, allSchedules);
    
    const newStartTime = new Date(newEvent.startTime);
    const newEndTime = new Date(newEvent.endTime);

    for (const existingEvent of driverEvents) {
      const existingStart = new Date(existingEvent.startTime);
      const existingEnd = new Date(existingEvent.endTime);

      // Check for direct time overlap
      if (this.hasTimeOverlap(newStartTime, newEndTime, existingStart, existingEnd)) {
        conflicts.push({
          type: 'overlap',
          severity: 'high',
          message: `Direct time conflict with "${existingEvent.title}" for ${existingEvent.vipName}`,
          conflictingEvent: existingEvent
        });
      }
      // Check for tight turnaround (less than 15 minutes between events)
      else {
        const timeBetween = this.getTimeBetweenEvents(
          newStartTime, newEndTime, existingStart, existingEnd
        );
        
        if (timeBetween !== null && timeBetween < 15) {
          conflicts.push({
            type: 'tight_turnaround',
            severity: timeBetween < 5 ? 'high' : 'medium',
            message: `Only ${timeBetween} minutes between events. Previous: "${existingEvent.title}"`,
            conflictingEvent: existingEvent,
            timeDifference: timeBetween
          });
        }
      }
    }

    return conflicts;
  }

  // Get availability status for all drivers for a specific time slot
  getDriverAvailability(
    eventTime: { startTime: string; endTime: string; location: string },
    allSchedules: { [vipId: string]: ScheduleEvent[] },
    drivers: any[]
  ): DriverAvailability[] {
    return drivers.map(driver => {
      const conflicts = this.checkDriverConflicts(driver.id, eventTime, allSchedules, drivers);
      const driverEvents = this.getDriverEvents(driver.id, allSchedules);
      
      let status: DriverAvailability['status'] = 'available';
      
      if (conflicts.length > 0) {
        const hasOverlap = conflicts.some(c => c.type === 'overlap');
        const hasTightTurnaround = conflicts.some(c => c.type === 'tight_turnaround');
        
        if (hasOverlap) {
          status = 'overlapping';
        } else if (hasTightTurnaround) {
          status = 'tight_turnaround';
        }
      } else if (driverEvents.length > 0) {
        status = 'scheduled';
      }

      return {
        driverId: driver.id,
        driverName: driver.name,
        status,
        assignmentCount: driverEvents.length,
        conflicts,
        currentAssignments: driverEvents
      };
    });
  }

  // Get all events assigned to a specific driver
  private getDriverEvents(driverId: string, allSchedules: { [vipId: string]: ScheduleEvent[] }): ScheduleEvent[] {
    const driverEvents: ScheduleEvent[] = [];
    
    Object.entries(allSchedules).forEach(([vipId, events]) => {
      events.forEach(event => {
        if (event.assignedDriverId === driverId) {
          driverEvents.push({
            ...event,
            vipId,
            vipName: event.title // We'll need to get actual VIP name from VIP data
          });
        }
      });
    });

    // Sort by start time
    return driverEvents.sort((a, b) => 
      new Date(a.startTime).getTime() - new Date(b.startTime).getTime()
    );
  }

  // Check if two time periods overlap
  private hasTimeOverlap(
    start1: Date, end1: Date, 
    start2: Date, end2: Date
  ): boolean {
    return start1 < end2 && start2 < end1;
  }

  // Get minutes between two events (null if they overlap)
  private getTimeBetweenEvents(
    newStart: Date, newEnd: Date,
    existingStart: Date, existingEnd: Date
  ): number | null {
    // If new event is after existing event
    if (newStart >= existingEnd) {
      return Math.floor((newStart.getTime() - existingEnd.getTime()) / (1000 * 60));
    }
    // If new event is before existing event
    else if (newEnd <= existingStart) {
      return Math.floor((existingStart.getTime() - newEnd.getTime()) / (1000 * 60));
    }
    // Events overlap
    return null;
  }

  // Generate summary message for driver status
  getDriverStatusSummary(availability: DriverAvailability): string {
    switch (availability.status) {
      case 'available':
        return `✅ Fully available (${availability.assignmentCount} assignments)`;
      case 'scheduled':
        return `🟡 Has ${availability.assignmentCount} assignment(s) but available for this time`;
      case 'tight_turnaround':
        const tightConflict = availability.conflicts.find(c => c.type === 'tight_turnaround');
        return `⚡ Tight turnaround - ${tightConflict?.timeDifference} min between events`;
      case 'overlapping':
        return `🔴 Time conflict with existing assignment`;
      default:
        return 'Unknown status';
    }
  }
}

export default new DriverConflictService();
export { DriverAvailability, ConflictInfo, ScheduleEvent };