backend-service/internal/models/schedule.go

package models

import (
	"errors"
	"time"

	"gorm.io/gorm"
)

// Schedule represents available time slots
type Schedule struct {
	gorm.Model
	StartTime   time.Time `json:"start_time" gorm:"not null;index" validate:"required"`
	EndTime     time.Time `json:"end_time" gorm:"not null;index" validate:"required"`
	IsAvailable bool      `json:"is_available" gorm:"default:true"`
	MaxBookings int       `json:"max_bookings" gorm:"default:1;check:max_bookings > 0" validate:"min=1,max=100"`
	BookedCount int       `json:"booked_count" gorm:"default:0;check:booked_count >= 0" validate:"min=0"`
}

// BeforeCreate is a GORM hook that runs before creating a schedule record
func (s *Schedule) BeforeCreate(tx *gorm.DB) error {
	// Validate that end time is after start time
	if !s.EndTime.After(s.StartTime) {
		return errors.New("end time must be after start time")
	}

	// Validate minimum duration (15 minutes)
	if s.EndTime.Sub(s.StartTime) < 15*time.Minute {
		return errors.New("schedule slot must be at least 15 minutes long")
	}

	// Validate that start time is in the future
	if s.StartTime.Before(time.Now()) {
		return errors.New("schedule slot cannot be created in the past")
	}

	// Set default values
	if s.MaxBookings == 0 {
		s.MaxBookings = 1
	}

	return nil
}

// BeforeUpdate is a GORM hook that runs before updating a schedule record
func (s *Schedule) BeforeUpdate(tx *gorm.DB) error {
	// Validate that end time is after start time
	if !s.EndTime.After(s.StartTime) {
		return errors.New("end time must be after start time")
	}

	// Validate that booked count doesn't exceed max bookings
	if s.BookedCount > s.MaxBookings {
		return errors.New("booked count cannot exceed max bookings")
	}

	return nil
}

// IsAvailableForBooking checks if the schedule slot has availability
func (s *Schedule) IsAvailableForBooking() bool {
	return s.IsAvailable && s.BookedCount < s.MaxBookings && s.StartTime.After(time.Now())
}

// GetRemainingSlots returns the number of remaining booking slots
func (s *Schedule) GetRemainingSlots() int {
	remaining := s.MaxBookings - s.BookedCount
	if remaining < 0 {
		return 0
	}
	return remaining
}

// Duration returns the duration of the schedule slot
func (s *Schedule) Duration() time.Duration {
	return s.EndTime.Sub(s.StartTime)
}