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backend/src/services/CalculationService.ts

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+import pool from '../config/database';
+import { PerformanceLevel } from '../dao/PerformanceDAO';
+
+export interface AttendanceInput {
+  leaveDays: number;
+  lateTimes: number;
+  lackCardTimes: number;
+}
+
+export interface LevelAndReward {
+  level: PerformanceLevel;
+  rewardPunish: string;
+}
+
+export interface ConsecutiveLowScoreResult {
+  consecutiveMonths: number;
+  warning: 'none' | 'written_warning' | 'dismissal';
+}
+
+/**
+ * Calculate attendance score.
+ * Base: 10 points. Deduct 5 per leave day, 2 per late/lack-card occurrence. Minimum 0.
+ * Requirements: 11.1, 11.2, 11.3, 11.5
+ */
+export function calculateAttendanceScore(input: AttendanceInput): number {
+  const { leaveDays, lateTimes, lackCardTimes } = input;
+  const deduction = leaveDays * 5 + lateTimes * 2 + lackCardTimes * 2;
+  return Math.max(0, 10 - deduction);
+}
+
+/**
+ * Calculate performance level and reward/punishment description based on total score.
+ * Requirements: 5.1, 5.2, 5.3, 5.4, 5.5
+ */
+export function calculateLevelAndReward(totalScore: number): LevelAndReward {
+  if (totalScore >= 90) {
+    return { level: 'excellent', rewardPunish: '优秀，按公司规定给予奖励' };
+  } else if (totalScore >= 80) {
+    return { level: 'qualified', rewardPunish: '合格，扣除当月绩效工资100元' };
+  } else if (totalScore >= 70) {
+    return { level: 'qualified', rewardPunish: '合格，扣除当月绩效工资200元' };
+  } else if (totalScore >= 60) {
+    return { level: 'need_motivation', rewardPunish: '需激励，扣除当月绩效工资300元' };
+  } else {
+    return { level: 'unqualified', rewardPunish: '不合格，扣除当月绩效工资600元' };
+  }
+}
+
+/**
+ * Check consecutive low score warning for an employee.
+ * Queries the most recent completed performance records and counts consecutive months below 60.
+ * Requirements: 5.6, 5.7
+ */
+export async function checkConsecutiveLowScore(
+  userId: number,
+  lookbackMonths: number = 3
+): Promise<ConsecutiveLowScoreResult> {
+  const [rows] = await pool.query<any[]>(
+    `SELECT total_score FROM performance_month
+     WHERE user_id = ? AND status = 'completed' AND total_score IS NOT NULL
+     ORDER BY month DESC
+     LIMIT ?`,
+    [userId, lookbackMonths]
+  );
+
+  let consecutiveMonths = 0;
+  for (const row of rows) {
+    if (row.total_score < 60) {
+      consecutiveMonths++;
+    } else {
+      break;
+    }
+  }
+
+  let warning: ConsecutiveLowScoreResult['warning'] = 'none';
+  if (consecutiveMonths >= 3) {
+    warning = 'dismissal';
+  } else if (consecutiveMonths >= 2) {
+    warning = 'written_warning';
+  }
+
+  return { consecutiveMonths, warning };
+}