from rest_framework.permissions import BasePermission, SAFE_METHODS

from apps.accounts.models import Role


class IsTeacher(BasePermission):
    message = "Only teachers can perform this action."

    def has_permission(self, request, view):
        u = request.user
        return bool(u and u.is_authenticated and u.role == Role.TEACHER)


class IsApprovedTeacher(BasePermission):
    message = "Your teacher profile must be approved by an admin first."

    def has_permission(self, request, view):
        u = request.user
        if not (u and u.is_authenticated and u.role == Role.TEACHER):
            return False
        tp = getattr(u, "teacher_profile", None)
        return bool(tp and tp.is_approved)


class IsCourseOwner(BasePermission):
    """Object-level: the course (or its parent for sections/lessons) must be owned by the request user."""

    message = "You do not own this course."

    def has_object_permission(self, request, view, obj):
        from apps.courses.models import Course, Lesson, Section

        if isinstance(obj, Course):
            return obj.instructor_id == request.user.id
        if isinstance(obj, Section):
            return obj.course.instructor_id == request.user.id
        if isinstance(obj, Lesson):
            return obj.section.course.instructor_id == request.user.id
        return False


class ReadOnly(BasePermission):
    def has_permission(self, request, view):
        return request.method in SAFE_METHODS