feat: 고정/유동 스케줄 생성 (#5)

services/scheduleService.js

+const { Op } = require('sequelize');
+const Schedule = require('../models/Schedule');
+
+class schedulService {
+
+    /**
+     * 유동 스케줄 만료일 구하기
+     */
+    getNextMonday() {
+        const date = new Date();
+        const day = date.getDay();
+        const daysUntilNextMonday = (8 - day) % 7;
+        date.setDate(date.getDate() + daysUntilNextMonday);
+        date.setHours(0, 0, 0, 0);
+        return date;
+    }
+
+    /**
+     * 사용자 스케줄 생성
+     */
+    async createSchedule({ userId, title, start_time, end_time, is_fixed }) {
+        try {
+            const scehduleData = {
+                user_id: userId,
+                title,
+                start_time,
+                end_time,
+                is_fixed,
+                expiry_date: is_fixed ? null : this.getNextMonday()
+            };
+
+            const schedule = await Schedule.create(scehduleData);
+            return schedule;
+        } catch (error) {
+            throw new Error(`Failed to create schedule: ${error.message}`);
+        }
+    }
+
+}
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