Dovodi_Backend/apps/course/serializers/course.py

from rest_framework import serializers
# from dj_filer.admin import get_thumbs
from utils import get_thumbs
from apps.course.models import Course, CourseCategory, Attachment, Glossary, LessonCompletion, Participant, Lesson, CourseAttachment, CourseGlossary, CourseLesson
from apps.chat.models import RoomMessage
from apps.account.serializers import UserProfileSerializer



class CourseCategorySerializer(serializers.ModelSerializer):
    course_count = serializers.SerializerMethodField()
    
    class Meta:
        model = CourseCategory
        fields = ['name', 'slug', 'course_count'] 

    def get_course_count(self, obj):
        return obj.course_count


class CourseListSerializer(serializers.ModelSerializer):
    category = CourseCategorySerializer()
    thumbnail = serializers.SerializerMethodField()
    participant_count = serializers.SerializerMethodField()
    lessons_count = serializers.SerializerMethodField()
    price = serializers.SerializerMethodField()
    discount_percentage = serializers.SerializerMethodField()
    final_price = serializers.SerializerMethodField()
    is_free = serializers.SerializerMethodField() 

    class Meta:
        model = Course        
        fields = [
            'id',
            'title',
            'slug',
            'participant_count',
            'category',
            'thumbnail',
            'is_online',
            'online_link',
            'level',
            'duration',
            'lessons_count',
            'short_description',
            'status',
            'is_free',
            'price',
            'discount_percentage',
            'final_price',    
        ]

    def get_thumbnail(self, obj):
        return get_thumbs(obj.thumbnail, self.context.get('request'))
    
    def get_participant_count(self, obj):
        return obj.participants.count()
    
    def get_lessons_count(self, obj):
        # Use prefetched lessons if available
        if hasattr(obj, 'lessons') and obj.lessons.all():
            lessons_count = sum(1 for lesson in obj.lessons.all() if lesson.is_active)
            return max(lessons_count, obj.lessons_count)
        # Fallback to direct query
        lessons_count = obj.lessons.filter(is_active=True).count()
        return max(lessons_count, obj.lessons_count)
        
    def get_price(self, obj):
        if obj.is_free or obj.price == 0:
            return "0.00"
        return str(obj.price)
        
    def get_discount_percentage(self, obj):
        if obj.is_free or obj.price == 0:
            return 0
        return obj.discount_percentage
        
    def get_final_price(self, obj):
        if obj.is_free or obj.price == 0:
            return "0.00"
        return str(obj.final_price)
    
    def get_is_free(self, obj):
        return obj.is_free or obj.price == 0
    
    
class CourseDetailSerializer(serializers.ModelSerializer):
    category = CourseCategorySerializer()
    professor = serializers.SerializerMethodField()
    thumbnail = serializers.SerializerMethodField()
    participant_count = serializers.SerializerMethodField()
    access = serializers.SerializerMethodField()
    lessons_complated_count = serializers.SerializerMethodField()
    lessons_count = serializers.SerializerMethodField()
    last_lesson_id = serializers.SerializerMethodField()
    room_id = serializers.SerializerMethodField()  
    user_transaction_status = serializers.SerializerMethodField()
    price = serializers.SerializerMethodField()
    discount_percentage = serializers.SerializerMethodField()
    final_price = serializers.SerializerMethodField()
    is_free = serializers.SerializerMethodField()
    is_professor = serializers.SerializerMethodField()

    class Meta:
        model = Course        
        fields = [
            'id',
            'title',
            'slug',
            'category',
            'access',
            'participant_count',
            'professor',
            'is_professor',
            'thumbnail',
            'video_type',
            'video_file',
            'video_link',
            'is_online',
            'online_link',
            'level',
            'description',
            'duration',
            'lessons_count',
            'lessons_complated_count',
            'short_description',
            'status',
            'is_free',
            'price',
            'discount_percentage',
            'final_price',
            'timing',
            'features',
            'last_lesson_id',
            'room_id',
            'user_transaction_status',
            'is_group_chat_locked',
            'is_professor_chat_locked'
        ]

    def get_room_id(self, obj):
        # Use prefetched room_messages if available
        if hasattr(obj, 'room_messages') and obj.room_messages.all():
            return obj.room_messages.first().id
        # Fallback to direct query if not prefetched
        room_message = RoomMessage.objects.filter(course=obj).first()
        if room_message:
            return room_message.id
        return None
    
    def get_user_transaction_status(self, obj):
        from apps.transaction.models import TransactionParticipant
        if student := self._get_authenticated_user():
            latest_transaction = TransactionParticipant.objects.filter(
                user=student,
                course=obj,
                is_deleted=False
            ).order_by('-created_at').first()
            if latest_transaction:
                return latest_transaction.status
        return None
    
    def get_last_lesson_id(self, obj):
        request = self.context.get('request')
        if request and request.user.is_authenticated:
            user = request.user

            # Use prefetched lessons if available
            if hasattr(obj, 'lessons') and obj.lessons.all():
                lessons = [lesson for lesson in obj.lessons.all() if lesson.is_active]
                completed_lessons = []

                # Check which lessons are completed using prefetched data
                for lesson in lessons:
                    if hasattr(lesson, 'completions') and lesson.completions.all():
                        if any(completion.student_id == user.id for completion in lesson.completions.all()):
                            completed_lessons.append(lesson)

                if completed_lessons:
                    # Find the last completed lesson by priority
                    last_completed = max(completed_lessons, key=lambda x: x.priority)
                    # Find next lesson
                    next_lessons = [l for l in lessons if l.priority > last_completed.priority]
                    if next_lessons:
                        return min(next_lessons, key=lambda x: x.priority).id

                # If no completed lessons or no next lesson, return first lesson
                if lessons:
                    return min(lessons, key=lambda x: x.priority).id

            # Fallback to direct queries if not prefetched
            last_completed_lesson = LessonCompletion.objects.filter(
                student=user,
                course_lesson__course=obj
            ).order_by('-completed_at').first()

            if last_completed_lesson:
                next_lesson = CourseLesson.objects.filter(
                    course=obj,
                    priority__gt=last_completed_lesson.course_lesson.priority,
                    is_active=True
                ).order_by('priority').first()
                if not next_lesson:
                    next_lesson = CourseLesson.objects.filter(
                        course=obj,
                        is_active=True
                    ).order_by('priority').first()
                if next_lesson:
                    return next_lesson.id
        return None
            
            
            
    def get_access(self, obj):
        if user := self._get_authenticated_user():
            return self._has_access(user, obj)
        return False
    
    def get_professor(self, obj):
        """Return the course professor's profile using UserProfileSerializer"""
        if obj.professor:
            return UserProfileSerializer(obj.professor, context=self.context).data
        return None
            
    def get_is_professor(self, obj):
        if professor := self._get_authenticated_user():
            return obj.professor == professor
        return False
        
    def get_lessons_count(self, obj):
        # Use prefetched lessons if available
        if hasattr(obj, 'lessons') and obj.lessons.all():
            lessons_count = sum(1 for lesson in obj.lessons.all() if lesson.is_active)
            return max(lessons_count, obj.lessons_count)
        # Fallback to direct query
        lessons_count = obj.lessons.filter(is_active=True).count()
        return max(lessons_count, obj.lessons_count)


    def get_lessons_complated_count(self, obj):
        if student := self._get_authenticated_user():
            if not self._is_participant(student, obj):
                return None
            completed_count = self._get_completed_lessons_count(student, obj)
            # Ensure completed count doesn't exceed total lessons count
            total_lessons = self.get_lessons_count(obj)
            return min(completed_count, total_lessons)
        return None
        
    def _has_access(self, user, course):
        """
        Check if the user has access to the course content.
        Access is granted if:
        1. User is the professor of the course.
        2. User is staff (admin).
        3. User is an active participant in the course.
        """
        if user.is_staff or user.is_superuser:
            return True
            
        if course.professor_id == user.id:
            return True
            
        return Participant.objects.filter(
            student_id=user.id, 
            course=course,
            is_active=True
        ).exists()

    def _is_participant(self, student, course):
        """Deprecated: use _has_access instead. Kept for backward compatibility if needed."""
        return self._has_access(student, course)

    def _get_authenticated_user(self):
        """Helper method to retrieve the authenticated user from the context."""
        request = self.context.get('request')
        return request.user if request and request.user.is_authenticated else None

    def _get_completed_lessons_count(self, student, course):
        """Helper method to count completed lessons for the student in the given course."""
        # Use prefetched completions if available
        if hasattr(course, 'lessons') and course.lessons.all():
            completed_count = 0
            for lesson in course.lessons.all():
                if hasattr(lesson, 'completions') and lesson.completions.all():
                    if any(completion.student_id == student.id for completion in lesson.completions.all()):
                        completed_count += 1
            return completed_count

        # Fallback to direct query if not prefetched
        return LessonCompletion.objects.filter(
            student=student,
            course_lesson__course=course
        ).count()
        

    def get_thumbnail(self, obj):
        return get_thumbs(obj.thumbnail, self.context.get('request'))
    
    def get_participant_count(self, obj):
        # Use prefetched participants if available
        if hasattr(obj, 'participants') and obj.participants.all():
            return len(obj.participants.all())
        # Fallback to direct query
        return obj.participants.count()
        
    def get_price(self, obj):
        if obj.is_free or obj.price == 0:
            return "0.00"
        return str(obj.price)
        
    def get_discount_percentage(self, obj):
        if obj.is_free or obj.price == 0:
            return 0
        return obj.discount_percentage
        
    def get_final_price(self, obj):
        if obj.is_free or obj.price == 0:
            return "0.00"
        return str(obj.final_price)
    def get_is_free(self, obj):
        return obj.is_free or obj.price == 0

    
    
class MyCourseListSerializer(serializers.ModelSerializer):
    category = CourseCategorySerializer()
    thumbnail = serializers.SerializerMethodField()
    lessons_count = serializers.SerializerMethodField()
    lessons_complated_count = serializers.SerializerMethodField()

    class Meta:
        model = Course
        fields = [
            'id',
            'title',
            'slug',
            'category',
            'thumbnail',
            'lessons_count',
            'lessons_complated_count',
            'short_description',
            'status',
        ]

    def get_thumbnail(self, obj):
        return get_thumbs(obj.thumbnail, self.context.get('request'))

    def get_lessons_count(self, obj):
        """Get the actual count of active lessons"""
        # Use prefetched lessons if available
        if hasattr(obj, 'lessons') and obj.lessons.all():
            lessons_count = sum(1 for lesson in obj.lessons.all() if lesson.is_active)
            return max(lessons_count, obj.lessons_count)
        # Fallback to direct query
        lessons_count = obj.lessons.filter(is_active=True).count()
        return max(lessons_count, obj.lessons_count)

    def get_lessons_complated_count(self, obj):
        if student := self._get_authenticated_user():
            if not self._is_participant(student, obj):
                return None
            completed_count = self._get_completed_lessons_count(student, obj)
            # Ensure completed count doesn't exceed total lessons count
            total_lessons = self.get_lessons_count(obj)
            return min(completed_count, total_lessons)
        return None
        
    def _is_participant(self, student, course):
        """Helper method to check if a student is a participant in the given course."""
        if student.is_staff or student.is_superuser:
            return True
            
        # اگر کاربر استاد دوره است، دسترسی کامل دارد
        if course.professor_id == student.id:
            return True
            
        # در غیر این صورت چک می‌کنیم که آیا participant است یا خیر
        return Participant.objects.filter(
            student_id=student.id, 
            course=course,
            is_active=True
        ).exists()

    def _get_authenticated_user(self):
        """Helper method to retrieve the authenticated user from the context."""
        request = self.context.get('request')
        return request.user if request and request.user.is_authenticated else None

    def _get_completed_lessons_count(self, student, course):
        """Helper method to count completed lessons for the student in the given course."""
        # Use prefetched completions if available
        if hasattr(course, 'lessons') and course.lessons.all():
            completed_count = 0
            for lesson in course.lessons.all():
                if hasattr(lesson, 'completions') and lesson.completions.all():
                    if any(completion.student_id == student.id for completion in lesson.completions.all()):
                        completed_count += 1
            return completed_count

        # Fallback to direct query if not prefetched
        return LessonCompletion.objects.filter(
            student=student,
            course_lesson__course=course
        ).count()
    

class AttachmentSerializer(serializers.ModelSerializer):
    class Meta:
        model = Attachment
        fields = ['id', 'title', 'file', 'file_size']


class CourseAttachmentSerializer(serializers.ModelSerializer):
    title = serializers.CharField(source='attachment.title', read_only=True)
    file = serializers.FileField(source='attachment.file', read_only=True)
    file_size = serializers.IntegerField(source='attachment.file_size', read_only=True)
    
    class Meta:
        model = CourseAttachment
        fields = ['id', 'title', 'file', 'file_size']
        

class GlossarySerializer(serializers.ModelSerializer):
    class Meta:
        model = Glossary
        fields = ['id', 'title', 'description']


class CourseGlossarySerializer(serializers.ModelSerializer):
    title = serializers.CharField(source='glossary.title', read_only=True)
    description = serializers.CharField(source='glossary.description', read_only=True)
    
    class Meta:
        model = CourseGlossary
        fields = ['id', 'title', 'description']