from rest_framework import serializers

from apps.courses.api.serializers import (
    CategorySerializer,
    CourseFAQSerializer,
    CourseHighlightSerializer,
    LessonReadSerializer,
    SectionReadSerializer,
)
from apps.courses.models import Lesson, LessonStatus
from apps.enrollments.models import Enrollment, LessonProgress


class EnrolledCourseSummarySerializer(serializers.Serializer):
    """Used by the my-courses dashboard list. Mirrors the design's MY_COURSES shape."""

    id = serializers.IntegerField()
    slug = serializers.CharField()
    title = serializers.CharField()
    tagline = serializers.CharField()
    color = serializers.CharField()
    cover_image = serializers.SerializerMethodField()
    instructor_id = serializers.IntegerField()
    instructor_name = serializers.SerializerMethodField()
    enrolled_at = serializers.DateTimeField()
    completed_at = serializers.DateTimeField(allow_null=True)
    progress_percent = serializers.IntegerField()
    completed_lessons = serializers.IntegerField()
    total_lessons = serializers.IntegerField()
    last_lesson_id = serializers.IntegerField(allow_null=True)
    last_lesson_title = serializers.CharField(allow_null=True)
    next_lesson_id = serializers.IntegerField(allow_null=True)
    next_lesson_title = serializers.CharField(allow_null=True)

    def get_cover_image(self, obj):
        url = obj.get("cover_image_url")
        request = self.context.get("request")
        if url and request:
            return request.build_absolute_uri(url)
        return url

    def get_instructor_name(self, obj):
        return obj.get("instructor_name")


class StudentCourseDetailSerializer(serializers.Serializer):
    """Full course detail for an enrolled student — all published lesson content unlocked."""

    id = serializers.IntegerField()
    slug = serializers.CharField()
    title = serializers.CharField()
    tagline = serializers.CharField()
    description = serializers.CharField()
    level = serializers.CharField()
    language = serializers.CharField()
    color = serializers.CharField()
    cover_image = serializers.SerializerMethodField()
    instructor_id = serializers.IntegerField()
    instructor_name = serializers.CharField()
    category = CategorySerializer(allow_null=True)
    highlights = CourseHighlightSerializer(many=True)
    faqs = CourseFAQSerializer(many=True)
    sections = serializers.SerializerMethodField()
    enrollment = serializers.SerializerMethodField()

    def get_cover_image(self, obj):
        course = obj["course"]
        if not course.cover_image:
            return None
        request = self.context.get("request")
        if request:
            return request.build_absolute_uri(course.cover_image.url)
        return course.cover_image.url

    def get_sections(self, obj):
        course = obj["course"]
        completed_lesson_ids = obj["completed_lesson_ids"]
        sections = course.sections.all().prefetch_related(
            "lessons"
        )
        out = []
        for sec in sections:
            published = [l for l in sec.lessons.all() if l.status == LessonStatus.PUBLISHED]
            published.sort(key=lambda l: (l.order, l.id))
            out.append({
                "id": sec.id,
                "title": sec.title,
                "order": sec.order,
                "lessons": LessonReadSerializer(
                    published, many=True
                ).data,
                "lessons_completed": [
                    l.id for l in published if l.id in completed_lesson_ids
                ],
            })
        return out

    def get_enrollment(self, obj):
        e = obj["enrollment"]
        return {
            "enrolled_at": e.enrolled_at,
            "completed_at": e.completed_at,
            "progress_percent": e.progress_percent(),
            "completed_lessons": e.completed_lessons_count(),
            "total_lessons": e.total_lessons_count(),
        }


class EnrollResponseSerializer(serializers.Serializer):
    enrolled = serializers.BooleanField()
    course_id = serializers.IntegerField()
    course_slug = serializers.CharField()
    enrolled_at = serializers.DateTimeField()


class LessonProgressResponseSerializer(serializers.ModelSerializer):
    progress_percent = serializers.SerializerMethodField()
    course_completed = serializers.SerializerMethodField()

    class Meta:
        model = LessonProgress
        fields = ["id", "lesson", "completed_at", "progress_percent", "course_completed"]
        read_only_fields = fields

    def get_progress_percent(self, obj):
        return obj.enrollment.progress_percent()

    def get_course_completed(self, obj):
        return obj.enrollment.is_completed


class InstructorEnrollmentSerializer(serializers.ModelSerializer):
    """Compact list view for the instructor's CRM-style student panel."""

    student_id = serializers.IntegerField(source="student.id", read_only=True)
    student_name = serializers.CharField(source="student.full_name", read_only=True)
    student_phone = serializers.CharField(source="student.phone_number", read_only=True)
    student_last_active_at = serializers.DateTimeField(source="student.last_active_at", read_only=True)
    progress_percent = serializers.SerializerMethodField()
    completed_lessons = serializers.SerializerMethodField()
    total_lessons = serializers.SerializerMethodField()
    engagement_status = serializers.SerializerMethodField()

    class Meta:
        model = Enrollment
        fields = [
            "id",
            "student_id",
            "student_name",
            "student_phone",
            "student_last_active_at",
            "course_id",
            "enrolled_at",
            "completed_at",
            "progress_percent",
            "completed_lessons",
            "total_lessons",
            "engagement_status",
        ]
        read_only_fields = fields

    def get_progress_percent(self, obj):
        return obj.progress_percent()

    def get_completed_lessons(self, obj):
        return obj.completed_lessons_count()

    def get_total_lessons(self, obj):
        return obj.total_lessons_count()

    def get_engagement_status(self, obj):
        return obj.engagement_status()