import random
import pandas as pd
from io import BytesIO


class ProbabilityCalculator:
    @staticmethod
    def weighted_random_selection(students):
        if not students:
            raise ValueError("学生列表不能为空")

        base_weight = 100
        decay_factor = 8  # 积分越高，权重越低
        weights = []
        for student in students:
            score_deduction = min(student.total_score * decay_factor, 85)
            weight = max(base_weight - score_deduction, 15)
            weights.append({'student': student, 'weight': weight})

        total_weight = sum(item['weight'] for item in weights)
        random_value = random.uniform(0, total_weight)
        current_sum = 0
        for item in weights:
            current_sum += item['weight']
            if current_sum >= random_value:
                return item['student']
        return weights[0]['student']


class ScoreCalculator:
    @staticmethod
    def calculate_score(answer_type, performance):
        score_map = {
            'repeat_question': {'correct': 0.5, 'incorrect': -1},
            'answer_question': {'excellent': 3, 'good': 2, 'normal': 1, 'poor': 0.5},
            'present': {'present': 1}
        }
        return score_map.get(answer_type, {}).get(performance, 0)


class ExcelService:

    # 导出详单（含专业、点名次数）
    @staticmethod
    def export_detailed_scores(students):
        data = []
        for student in students:
            data.append({
                '学号': student.student_id,
                '姓名': student.name,
                '专业': student.major,
                '班级': student.class_name,
                '随机点名次数': student.call_count,
                '总积分': student.total_score
            })
        df = pd.DataFrame(data)
        output = BytesIO()
        with pd.ExcelWriter(output, engine='openpyxl') as writer:
            df.to_excel(writer, sheet_name='积分详单', index=False)
        output.seek(0)
        return output