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backend/utils/dateUtils.js

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+/**
+ * Date and Time Utilities for WIB (UTC+7) Timezone Handling
+ * Implements D-1 data filtering logic for dashboard display before 17:00 WIB
+ */
+
+const CUTOFF_HOUR = process.env.CUTOFF_HOUR_OVERRIDE
+    ? parseInt(process.env.CUTOFF_HOUR_OVERRIDE, 10)
+    : 17;
+
+/**
+ * Get current date/time in WIB (Asia/Jakarta, UTC+7) timezone
+ * @returns {Date} Current date in WIB
+ */
+function getCurrentWibDate() {
+    const now = new Date();
+
+    // Convert to WIB using toLocaleString with Jakarta timezone
+    const wibDateString = now.toLocaleString('en-US', {
+        timeZone: 'Asia/Jakarta',
+        year: 'numeric',
+        month: '2-digit',
+        day: '2-digit',
+        hour: '2-digit',
+        minute: '2-digit',
+        second: '2-digit',
+        hour12: false
+    });
+
+    // Parse the formatted string back to Date object
+    return new Date(wibDateString);
+}
+
+/**
+ * Check if current WIB time is before the cutoff hour (default 17:00)
+ * @returns {boolean} True if before cutoff, false otherwise
+ */
+function isBeforeCutoffTime() {
+    const wibNow = getCurrentWibDate();
+    const currentHour = wibNow.getHours();
+    return currentHour < CUTOFF_HOUR;
+}
+
+/**
+ * Get the effective query date (D-1 if before cutoff, else today)
+ * @returns {Date} Effective date for data queries
+ */
+function getEffectiveQueryDate() {
+    const wibToday = getCurrentWibDate();
+
+    if (isBeforeCutoffTime()) {
+        // Return D-1 (previous day)
+        const yesterday = new Date(wibToday);
+        yesterday.setDate(yesterday.getDate() - 1);
+        return yesterday;
+    }
+
+    return wibToday;
+}
+
+/**
+ * Calculate effective day of cycle accounting for D-1 filter
+ * @param {Date|string} cycleStartDate - Cycle start date
+ * @returns {number} Effective cycle day (0-indexed from start date)
+ */
+function getEffectiveCycleDay(cycleStartDate) {
+    const effectiveDate = getEffectiveQueryDate();
+    const startDate = new Date(cycleStartDate);
+
+    // Reset hours to compare dates only
+    effectiveDate.setHours(0, 0, 0, 0);
+    startDate.setHours(0, 0, 0, 0);
+
+    const diffMs = effectiveDate.getTime() - startDate.getTime();
+
+    // Return -1 if effective date is before cycle start (edge case)
+    if (diffMs < 0) {
+        return -1;
+    }
+
+    const dayOfCycle = Math.floor(diffMs / (1000 * 60 * 60 * 24));
+    return dayOfCycle;
+}
+
+/**
+ * Format date as YYYY-MM-DD for database queries
+ * @param {Date} date - Date object to format
+ * @returns {string} Date in YYYY-MM-DD format
+ */
+function formatDateForDb(date) {
+    const year = date.getFullYear();
+    const month = String(date.getMonth() + 1).padStart(2, '0');
+    const day = String(date.getDate()).padStart(2, '0');
+    return `${year}-${month}-${day}`;
+}
+
+/**
+ * Get previous date (D-1) from a given date
+ * @param {string} dateString - Date string in YYYY-MM-DD format
+ * @returns {string} Previous date in YYYY-MM-DD format
+ */
+function getPreviousDate(dateString) {
+    const date = new Date(dateString);
+    date.setDate(date.getDate() - 1);
+    return formatDateForDb(date);
+}
+
+/**
+ * Create API response metadata for D-1 filtering
+ * @param {boolean} isD1Applied - Whether D-1 filter was applied
+ * @returns {object} Metadata object for API response
+ */
+function createResponseMetadata(isD1Applied = false) {
+    const wibNow = getCurrentWibDate();
+    const effectiveDate = getEffectiveQueryDate();
+
+    return {
+        effectiveDate: formatDateForDb(effectiveDate),
+        queryDate: formatDateForDb(wibNow),
+        isD1Filter: isD1Applied,
+        currentWibTime: wibNow.toLocaleTimeString('id-ID', {
+            timeZone: 'Asia/Jakarta',
+            hour: '2-digit',
+            minute: '2-digit'
+        })
+    };
+}
+
+module.exports = {
+    getCurrentWibDate,
+    isBeforeCutoffTime,
+    getEffectiveQueryDate,
+    getEffectiveCycleDay,
+    formatDateForDb,
+    getPreviousDate,
+    createResponseMetadata,
+    CUTOFF_HOUR // Export for testing
+};