from rest_framework import serializers
from utils import FileFieldSerializer, get_thumbs
from apps.course.models import (
    Course,
    CourseCategory,
    CourseChapter,
    CourseLesson,
    Lesson,
    CourseAttachment,
    Attachment,
    CourseGlossary,
    Glossary,
    CourseLiveSession,
    LiveSessionUser,
    LiveSessionRecording,
    Participant
)
from apps.account.models import ProfessorUser
from apps.course.models.course import extract_text_from_json, get_localized_field

def get_request_lang(serializer_instance):
    request = serializer_instance.context.get('request')
    language_code = getattr(request, 'LANGUAGE_CODE', None)
    if language_code:
        return str(language_code).lower()

    header_value = ''
    if request is not None:
        if hasattr(request, 'headers'):
            header_value = request.headers.get('Accept-Language', '')
        if not header_value and hasattr(request, 'META'):
            header_value = request.META.get('HTTP_ACCEPT_LANGUAGE', '')

    if header_value:
        return header_value.split(',')[0].strip().lower()

    return 'en'

class AdminLessonSerializer(serializers.ModelSerializer):
    title_i18n = serializers.JSONField(source='title', read_only=True)
    content_type_i18n = serializers.JSONField(source='content_type', read_only=True)

    class Meta:
        model = Lesson
        fields = [
            'id',
            'title',
            'title_i18n',
            'content_type',
            'content_type_i18n',
            'content_file',
            'video_link',
            'duration',
            'created_at',
            'updated_at',
        ]

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        lang = get_request_lang(self)
        ret['title'] = get_localized_field(lang, instance.title)
        ret['content_type'] = get_localized_field(lang, instance.content_type)
        return ret

class AdminGlossarySerializer(serializers.ModelSerializer):
    description_i18n = serializers.JSONField(source='description', read_only=True)

    class Meta:
        model = Glossary
        fields = '__all__'

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        lang = get_request_lang(self)
        ret['description'] = get_localized_field(lang, instance.description)
        return ret

class AdminAttachmentSerializer(serializers.ModelSerializer):
    title_i18n = serializers.JSONField(source='title', read_only=True)

    class Meta:
        model = Attachment
        fields = '__all__'

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        lang = get_request_lang(self)
        ret['title'] = get_localized_field(lang, instance.title)
        return ret


def serialize_file(value, serializer):
    if not value:
        return None
    field = FileFieldSerializer()
    field.bind('', serializer)
    return field.to_representation(value)

class AdminCourseCategorySerializer(serializers.ModelSerializer):
    slug = serializers.JSONField(required=False, allow_null=True)
    name_i18n = serializers.JSONField(source='name', read_only=True)
    slug_i18n = serializers.JSONField(source='slug', read_only=True)

    class Meta:
        model = CourseCategory
        fields = ['id', 'name', 'name_i18n', 'slug', 'slug_i18n', 'icon']

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        lang = get_request_lang(self)
        ret['name'] = get_localized_field(lang, instance.name)
        ret['slug'] = get_localized_field(lang, instance.slug)
        icon = ret.get('icon')
        if icon and icon.startswith('/'):
            request = self.context.get('request')
            if request:
                ret['icon'] = request.build_absolute_uri(icon)
            else:
                from django.conf import settings
                ret['icon'] = f"{settings.SITE_DOMAIN}{icon}"
        return ret

class AdminCourseListSerializer(serializers.ModelSerializer):
    category_name = serializers.SerializerMethodField()
    professor_name = serializers.SerializerMethodField(read_only=True)
    professors = serializers.PrimaryKeyRelatedField(queryset=ProfessorUser.objects.all(), many=True, required=False)
    professor = serializers.PrimaryKeyRelatedField(queryset=ProfessorUser.objects.all(), required=False, allow_null=True, write_only=True)
    participant_count = serializers.SerializerMethodField()
    thumbnail = serializers.SerializerMethodField()

    class Meta:
        model = Course
        fields = [
            'id',
            'title',
            'slug',
            'category',
            'category_name',
            'professor',
            'professors',
            'professor_name',
            'thumbnail',
            'is_online',
            'level',
            'duration',
            'lessons_count',
            'status',
            'is_free',
            'price',
            'price_rub',
            'discount_percentage',
            'final_price',
            'final_price_rub',
            'participant_count',
            'created_at'
        ]

    def get_professor_name(self, obj):
        return ", ".join([p.fullname for p in obj.professors.all()])

    def get_participant_count(self, obj):
        return obj.participants.count()

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

    def get_category_name(self, obj):
        if not obj.category:
            return ""
        lang = get_request_lang(self)
        return get_localized_field(lang, obj.category.name)

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        lang = get_request_lang(self)
        ret['title'] = get_localized_field(lang, instance.title)
        ret['slug'] = get_localized_field(lang, instance.slug)
        ret['level'] = get_localized_field(lang, instance.level)
        ret['status'] = get_localized_field(lang, instance.status)
        
        # Inject legacy fields
        first_prof = instance.professors.first()
        ret['professor'] = first_prof.id if first_prof else None
        ret['professor_name'] = first_prof.fullname if first_prof else ""
        ret['professors'] = [p.id for p in instance.professors.all()]
        return ret


class AdminCourseDetailSerializer(serializers.ModelSerializer):
    slug = serializers.JSONField(required=False, allow_null=True)
    category_name = serializers.SerializerMethodField()
    professor_name = serializers.SerializerMethodField(read_only=True)
    professors = serializers.PrimaryKeyRelatedField(queryset=ProfessorUser.objects.all(), many=True, required=False)
    professor = serializers.PrimaryKeyRelatedField(queryset=ProfessorUser.objects.all(), required=False, allow_null=True, write_only=True)
    thumbnail = FileFieldSerializer(required=False, allow_null=True)
    video_file = FileFieldSerializer(required=False, allow_null=True)
    participant_count = serializers.SerializerMethodField()

    class Meta:
        model = Course
        fields = [
            'id',
            'title',
            'slug',
            'category',
            'category_name',
            'professor',
            'professors',
            'professor_name',
            'thumbnail',
            'video_type',
            'video_file',
            'video_link',
            'is_online',
            'online_link',
            'level',
            'duration',
            'lessons_count',
            'description',
            'short_description',
            'status',
            'is_free',
            'price',
            'price_rub',
            'discount_percentage',
            'final_price',
            'final_price_rub',
            'is_group_chat_locked',
            'is_professor_chat_locked',
            'timing',
            'features',
            'participant_count',
            'created_at',
            'updated_at'
        ]
        read_only_fields = ['id', 'final_price', 'final_price_rub', 'created_at', 'updated_at']

    def get_professor_name(self, obj):
        return ", ".join([p.fullname for p in obj.professors.all()])

    def get_participant_count(self, obj):
        return obj.participants.count()

    def get_category_name(self, obj):
        if not obj.category:
            return ""
        lang = get_request_lang(self)
        return get_localized_field(lang, obj.category.name)

    def create(self, validated_data):
        professor = validated_data.pop('professor', None)
        professors = validated_data.pop('professors', None)
        instance = super().create(validated_data)
        if professors is not None:
            instance.professors.set(professors)
        elif professor is not None:
            instance.professors.set([professor])
        return instance

    def update(self, instance, validated_data):
        professor = validated_data.pop('professor', None)
        professors = validated_data.pop('professors', None)
        instance = super().update(instance, validated_data)
        if professors is not None:
            instance.professors.set(professors)
        elif professor is not None:
            instance.professors.set([professor])
        return instance

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        lang = get_request_lang(self)
        ret['title'] = get_localized_field(lang, instance.title)
        ret['slug'] = get_localized_field(lang, instance.slug)
        ret['level'] = get_localized_field(lang, instance.level)
        ret['status'] = get_localized_field(lang, instance.status)
        ret['description'] = get_localized_field(lang, instance.description)
        ret['short_description'] = get_localized_field(lang, instance.short_description)
        # Inject legacy fields
        first_prof = instance.professors.first()
        ret['professor'] = first_prof.id if first_prof else None
        ret['professor_name'] = first_prof.fullname if first_prof else ""
        ret['professors'] = [p.id for p in instance.professors.all()]
        return ret


class AdminCourseChapterSerializer(serializers.ModelSerializer):
    title_i18n = serializers.JSONField(source='title', read_only=True)

    class Meta:
        model = CourseChapter
        fields = ['id', 'course', 'title', 'title_i18n', 'priority', 'is_active', 'created_at']
        read_only_fields = ['id', 'created_at']

    def to_representation(self, instance):
        ret = super().to_representation(instance)
        lang = get_request_lang(self)
        ret['title'] = get_localized_field(lang, instance.title)
        return ret


class AdminCourseLessonSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    course = serializers.IntegerField(required=False, read_only=True)
    chapter = serializers.IntegerField()
    lesson = serializers.IntegerField(required=False, write_only=True, allow_null=True)
    title = serializers.JSONField(required=False, allow_null=True)
    priority = serializers.IntegerField(required=False, allow_null=True)
    is_active = serializers.BooleanField(default=True)

    # Lesson (Base Content) fields
    content_type = serializers.JSONField(required=False, allow_null=True)
    content_file = FileFieldSerializer(required=False, allow_null=True)
    video_link = serializers.CharField(max_length=500, required=False, allow_blank=True, allow_null=True)
    duration = serializers.IntegerField(min_value=0, required=False, default=0)

    class Meta:
        ref_name = 'CourseAdminCourseLesson'

    def to_representation(self, instance):
        """
        Map a CourseLesson instance to representation fields.
        """
        lesson_obj = instance.lesson
        lang = get_request_lang(self)
        
        raw_title = instance.title or (lesson_obj.title if lesson_obj else [])
        localized_title = get_localized_field(lang, raw_title)
        
        raw_content_type = lesson_obj.content_type if lesson_obj else []
        localized_content_type = get_localized_field(lang, raw_content_type)
        
        return {
            'id': instance.id,
            'course': instance.course_id,
            'chapter': instance.chapter_id,
            'lesson': instance.lesson_id,
            'title': localized_title,
            'title_i18n': raw_title,
            'priority': instance.priority,
            'is_active': instance.is_active,
            'content_type': localized_content_type,
            'content_type_i18n': raw_content_type,
            'content_file': serialize_file(lesson_obj.content_file, self) if lesson_obj and lesson_obj.content_file else None,
            'video_link': lesson_obj.video_link if lesson_obj else "",
            'duration': lesson_obj.duration if lesson_obj else 0,
        }

    def create(self, validated_data):
        chapter_id = validated_data.pop('chapter')
        chapter = CourseChapter.objects.get(pk=chapter_id)
        course = chapter.course

        title = validated_data.get('title')
        priority = validated_data.get('priority')
        is_active = validated_data.get('is_active', True)

        lesson_id = validated_data.get('lesson')
        if lesson_id:
            try:
                lesson = Lesson.objects.get(pk=lesson_id)
            except Lesson.DoesNotExist:
                raise serializers.ValidationError({"lesson": "Lesson does not exist."})
            
            # Check if already linked to this course
            if CourseLesson.objects.filter(course=course, lesson=lesson).exists():
                raise serializers.ValidationError({"detail": "This lesson is already linked to this course."})
        else:
            content_type = validated_data.get('content_type')
            if not content_type:
                raise serializers.ValidationError({"detail": "Content type is required for new lessons."})
            content_file = validated_data.get('content_file')
            video_link = validated_data.get('video_link')
            duration = validated_data.get('duration', 0)

            # 1. Create Lesson Base
            lesson = Lesson.objects.create(
                title=title or "Base Lesson",
                content_type=content_type,
                content_file=content_file,
                video_link=video_link,
                duration=duration
            )

        # 2. Create CourseLesson junction
        course_lesson = CourseLesson.objects.create(
            course=course,
            chapter=chapter,
            lesson=lesson,
            title=title,
            priority=priority,
            is_active=is_active
        )
        return course_lesson

    def update(self, instance, validated_data):
        chapter_id = validated_data.get('chapter')
        if chapter_id:
            chapter = CourseChapter.objects.get(pk=chapter_id)
            instance.chapter = chapter
            instance.course = chapter.course

        if 'title' in validated_data:
            instance.title = validated_data['title']
        if 'priority' in validated_data:
            instance.priority = validated_data['priority']
        if 'is_active' in validated_data:
            instance.is_active = validated_data['is_active']

        instance.save()

        # Update the Base Lesson as well
        lesson = instance.lesson
        if lesson:
            if 'title' in validated_data and validated_data['title']:
                lesson.title = validated_data['title']
            if 'content_type' in validated_data:
                lesson.content_type = validated_data['content_type']
            if 'content_file' in validated_data:
                lesson.content_file = validated_data['content_file']
            if 'video_link' in validated_data:
                lesson.video_link = validated_data['video_link']
            if 'duration' in validated_data:
                lesson.duration = validated_data['duration']
            lesson.save()

        return instance


class AdminCourseAttachmentSerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    course = serializers.IntegerField()
    attachment = serializers.IntegerField(required=False, write_only=True, allow_null=True)
    title = serializers.JSONField(required=False, allow_null=True)
    file = FileFieldSerializer(required=False, allow_null=True)
    file_size = serializers.IntegerField(read_only=True)

    def to_representation(self, instance):
        attachment_obj = instance.attachment
        lang = get_request_lang(self)
        raw_title = attachment_obj.title if attachment_obj else []
        localized_title = get_localized_field(lang, raw_title)
        return {
            'id': instance.id,
            'course': instance.course_id,
            'attachment': instance.attachment_id,
            'title': localized_title,
            'title_i18n': raw_title,
            'file': serialize_file(attachment_obj.file, self) if attachment_obj and attachment_obj.file else None,
            'file_size': attachment_obj.file_size if attachment_obj else 0
        }

    def create(self, validated_data):
        course_id = validated_data.pop('course')
        course = Course.objects.get(pk=course_id)

        attachment_id = validated_data.get('attachment')
        if attachment_id:
            try:
                attachment = Attachment.objects.get(pk=attachment_id)
            except Attachment.DoesNotExist:
                raise serializers.ValidationError({"attachment": "Attachment does not exist."})
            
            # Check if already linked
            if CourseAttachment.objects.filter(course=course, attachment=attachment).exists():
                raise serializers.ValidationError({"detail": "This attachment is already linked to this course."})
        else:
            title = validated_data.get('title')
            file_data = validated_data.get('file')
            if not title or not file_data:
                raise serializers.ValidationError({"detail": "Title and file are required for new attachments."})

            # 1. Create Base Attachment
            attachment = Attachment.objects.create(
                title=title,
                file=file_data
            )

        # 2. Link to Course
        course_attachment = CourseAttachment.objects.create(
            course=course,
            attachment=attachment
        )
        return course_attachment

    def update(self, instance, validated_data):
        # We don't change the course in updates, just details of attachment
        attachment = instance.attachment
        if attachment:
            if 'title' in validated_data:
                attachment.title = validated_data['title']
            if 'file' in validated_data:
                attachment.file = validated_data['file']
                # Reset file size to trigger recalculation in save()
                attachment.file_size = None
            attachment.save()

        return instance


class AdminCourseGlossarySerializer(serializers.Serializer):
    id = serializers.IntegerField(read_only=True)
    course = serializers.IntegerField()
    glossary = serializers.IntegerField(required=False, write_only=True, allow_null=True)
    title = serializers.CharField(max_length=555, required=False, allow_blank=True, allow_null=True)
    description = serializers.JSONField(required=False, allow_null=True)

    def to_representation(self, instance):
        glossary_obj = instance.glossary
        lang = get_request_lang(self)
        raw_description = glossary_obj.description if glossary_obj else []
        localized_description = get_localized_field(lang, raw_description)
        return {
            'id': instance.id,
            'course': instance.course_id,
            'glossary': instance.glossary_id,
            'title': glossary_obj.title if glossary_obj else "",
            'description': localized_description,
            'description_i18n': raw_description,
        }

    def create(self, validated_data):
        course_id = validated_data.pop('course')
        course = Course.objects.get(pk=course_id)

        glossary_id = validated_data.get('glossary')
        if glossary_id:
            try:
                glossary = Glossary.objects.get(pk=glossary_id)
            except Glossary.DoesNotExist:
                raise serializers.ValidationError({"glossary": "Glossary term does not exist."})
            
            # Check if already linked
            if CourseGlossary.objects.filter(course=course, glossary=glossary).exists():
                raise serializers.ValidationError({"detail": "This glossary term is already linked to this course."})
        else:
            title = validated_data.get('title')
            description = validated_data.get('description')
            if not title or not description:
                raise serializers.ValidationError({"detail": "Title and description are required for new glossary terms."})

            # 1. Create Base Glossary
            glossary = Glossary.objects.create(
                title=title,
                description=description
            )

        # 2. Link to Course
        course_glossary = CourseGlossary.objects.create(
            course=course,
            glossary=glossary
        )
        return course_glossary

    def update(self, instance, validated_data):
        glossary = instance.glossary
        if glossary:
            if 'title' in validated_data:
                glossary.title = validated_data['title']
            if 'description' in validated_data:
                glossary.description = validated_data['description']
            glossary.save()

        return instance


class AdminLiveSessionUserSerializer(serializers.ModelSerializer):
    user_name = serializers.CharField(source='user.fullname', read_only=True)
    user_email = serializers.CharField(source='user.email', read_only=True)

    class Meta:
        model = LiveSessionUser
        fields = ['id', 'session', 'user', 'user_name', 'user_email', 'role', 'entered_at', 'exited_at', 'is_online']


class AdminLiveSessionRecordingSerializer(serializers.ModelSerializer):
    file = FileFieldSerializer(required=False, allow_null=True)
    thumbnail = FileFieldSerializer(required=False, allow_null=True)

    class Meta:
        model = LiveSessionRecording
        fields = ['id', 'session', 'title', 'file', 'file_time', 'recording_type', 'thumbnail', 'is_active', 'created_at']


class AdminLiveSessionListSerializer(serializers.ModelSerializer):
    course_title = serializers.SerializerMethodField()
    participant_count = serializers.SerializerMethodField()
    media_count = serializers.IntegerField(read_only=True)

    class Meta:
        model = CourseLiveSession
        fields = ['id', 'course', 'course_title', 'room_id', 'subject', 'started_at', 'ended_at', 'participant_count', 'media_count', 'created_at']

    def get_course_title(self, obj):
        if not obj.course:
            return ""
        lang = get_request_lang(self)
        return get_localized_field(lang, obj.course.title)

    def get_participant_count(self, obj):
        return obj.user_sessions.count()


class AdminLiveSessionDetailSerializer(serializers.ModelSerializer):
    course_title = serializers.SerializerMethodField()
    user_sessions = serializers.SerializerMethodField()
    recordings = AdminLiveSessionRecordingSerializer(many=True, read_only=True)
    recorded_file = FileFieldSerializer(required=False, allow_null=True)

    class Meta:
        model = CourseLiveSession
        fields = ['id', 'course', 'course_title', 'room_id', 'subject', 'started_at', 'ended_at', 'recorded_file', 'user_sessions', 'recordings', 'created_at', 'updated_at']

    def get_course_title(self, obj):
        if not obj.course:
            return ""
        lang = get_request_lang(self)
        return get_localized_field(lang, obj.course.title)

    def get_user_sessions(self, obj):
        # 1. Get all active participants of this course
        participants = obj.course.participants.filter(is_active=True).select_related('student')
        
        # 2. Get all live session user records for this session
        attendance_map = {
            ls_user.user_id: ls_user 
            for ls_user in obj.user_sessions.all().select_related('user')
        }
        
        # 3. Build the combined list
        data = []
        for p in participants:
            student = p.student
            # Check if this student has an attendance record
            attendance = attendance_map.get(student.id)
            
            if attendance:
                data.append({
                    'id': attendance.id,
                    'session': obj.id,
                    'user': student.id,
                    'user_name': student.fullname or student.username,
                    'user_email': student.email,
                    'role': attendance.role,
                    'entered_at': attendance.entered_at.isoformat() if attendance.entered_at else None,
                    'exited_at': attendance.exited_at.isoformat() if attendance.exited_at else None,
                    'is_online': attendance.is_online,
                    'has_attended': True
                })
            else:
                data.append({
                    'id': None,
                    'session': obj.id,
                    'user': student.id,
                    'user_name': student.fullname or student.username,
                    'user_email': student.email,
                    'role': 'participant',
                    'entered_at': None,
                    'exited_at': None,
                    'is_online': False,
                    'has_attended': False
                })
                
        # Also append any attendees who are NOT in the participants list (e.g. professor/moderator/observer)
        participant_student_ids = {p.student_id for p in participants}
        for user_id, attendance in attendance_map.items():
            if user_id not in participant_student_ids:
                data.append({
                    'id': attendance.id,
                    'session': obj.id,
                    'user': user_id,
                    'user_name': attendance.user.fullname or attendance.user.username,
                    'user_email': attendance.user.email,
                    'role': attendance.role,
                    'entered_at': attendance.entered_at.isoformat() if attendance.entered_at else None,
                    'exited_at': attendance.exited_at.isoformat() if attendance.exited_at else None,
                    'is_online': attendance.is_online,
                    'has_attended': True
                })
                
        return data