// Overtime Service: Berechnung der aktuellen Überstunden-Bilanz pro User
// Wird von /api/user/stats und /api/verwaltung/employees/current-overtime genutzt.

const { getHolidaysForDateRange } = require('./feiertage-service');

/**
 * Berechnet die aktuelle Überstunden-Bilanz für einen User (nur eingereichte Wochen).
 * Entspricht der Anzeige "Aktuelle Überstunden" im Mitarbeiter-Dashboard.
 *
 * @param {number} userId - User-ID
 * @param {object} db - Database-Instanz (sqlite3)
 * @param {function} callback - (err, currentOvertime) currentOvertime in Stunden (kann negativ sein)
 */
function getCurrentOvertimeForUser(userId, db, callback) {
  db.get(
    'SELECT wochenstunden, arbeitstage, overtime_offset_hours FROM users WHERE id = ?',
    [userId],
    (err, user) => {
      if (err) {
        return callback(err, null);
      }
      if (!user) {
        return callback(null, null);
      }

      const wochenstunden = user.wochenstunden || 0;
      const arbeitstage = user.arbeitstage || 5;
      const overtimeOffsetHours = user.overtime_offset_hours ? parseFloat(user.overtime_offset_hours) : 0;

      db.all(
        `SELECT DISTINCT week_start, week_end
         FROM weekly_timesheets
         WHERE user_id = ? AND status = 'eingereicht'
         ORDER BY week_start`,
        [userId],
        (err, weeks) => {
          if (err) {
            return callback(err, null);
          }

          if (!weeks || weeks.length === 0) {
            return callback(null, overtimeOffsetHours);
          }

          let totalOvertimeHours = 0;
          let totalOvertimeTaken = 0;
          let processedWeeks = 0;
          let hasError = false;
          let callbackDone = false;

          function done(value) {
            if (callbackDone) return;
            callbackDone = true;
            callback(null, value);
          }

          weeks.forEach((week) => {
            db.all(
              `SELECT id, date, total_hours, overtime_taken_hours, vacation_type, sick_status, start_time, end_time, updated_at
               FROM timesheet_entries
               WHERE user_id = ? AND date >= ? AND date <= ?
               ORDER BY date, updated_at DESC, id DESC`,
              [userId, week.week_start, week.week_end],
              (err, allEntries) => {
                if (hasError) return;
                if (err) {
                  hasError = true;
                  if (!callbackDone) {
                    callbackDone = true;
                    callback(err, null);
                  }
                  return;
                }

                const entriesByDate = {};
                (allEntries || []).forEach((entry) => {
                  const existing = entriesByDate[entry.date];
                  if (!existing) {
                    entriesByDate[entry.date] = entry;
                  } else {
                    const existingTime = existing.updated_at ? new Date(existing.updated_at).getTime() : 0;
                    const currentTime = entry.updated_at ? new Date(entry.updated_at).getTime() : 0;
                    if (currentTime > existingTime || (currentTime === existingTime && entry.id > existing.id)) {
                      entriesByDate[entry.date] = entry;
                    }
                  }
                });
                const entries = Object.values(entriesByDate);

                getHolidaysForDateRange(week.week_start, week.week_end)
                  .catch(() => new Set())
                  .then((holidaySet) => {
                    const startDate = new Date(week.week_start);
                    const endDate = new Date(week.week_end);
                    let workdays = 0;
                    let filledWorkdays = 0;
                    const fullDayHoursForCheck = wochenstunden > 0 && arbeitstage > 0 ? wochenstunden / arbeitstage : 8;

                    for (let d = new Date(startDate); d <= endDate; d.setDate(d.getDate() + 1)) {
                      const day = d.getDay();
                      if (day >= 1 && day <= 5) {
                        workdays++;
                        const dateStr = d.toISOString().split('T')[0];
                        if (holidaySet.has(dateStr)) {
                          filledWorkdays++;
                          continue;
                        }
                        const entry = entriesByDate[dateStr];
                        if (entry) {
                          const isFullDayVacation = entry.vacation_type === 'full';
                          const isSick = entry.sick_status === 1 || entry.sick_status === true;
                          const overtimeValue = entry.overtime_taken_hours ? parseFloat(entry.overtime_taken_hours) : 0;
                          const isFullDayOvertime = overtimeValue > 0 && Math.abs(overtimeValue - fullDayHoursForCheck) < 0.01;
                          const hasStartAndEnd =
                            entry.start_time &&
                            entry.end_time &&
                            entry.start_time.toString().trim() !== '' &&
                            entry.end_time.toString().trim() !== '';
                          if (isFullDayVacation || isSick || isFullDayOvertime || hasStartAndEnd) {
                            filledWorkdays++;
                          }
                        }
                      }
                    }

                    const fullDayHours = wochenstunden > 0 && arbeitstage > 0 ? wochenstunden / arbeitstage : 8;
                    let weekTotalHours = 0;
                    let weekOvertimeTaken = 0;
                    let weekVacationHours = 0;
                    let fullDayOvertimeDays = 0;

                    entries.forEach((entry) => {
                      const overtimeValue = entry.overtime_taken_hours ? parseFloat(entry.overtime_taken_hours) : 0;
                      const isFullDayOvertime = overtimeValue > 0 && Math.abs(overtimeValue - fullDayHours) < 0.01;

                      if (entry.overtime_taken_hours) {
                        weekOvertimeTaken += parseFloat(entry.overtime_taken_hours) || 0;
                      }
                      if (isFullDayOvertime) {
                        fullDayOvertimeDays++;
                      }

                      if (entry.vacation_type === 'full') {
                        weekVacationHours += fullDayHours;
                      } else if (entry.vacation_type === 'half') {
                        weekVacationHours += fullDayHours / 2;
                        if (entry.total_hours && !isFullDayOvertime) {
                          weekTotalHours += parseFloat(entry.total_hours) || 0;
                        }
                      } else {
                        if (entry.total_hours && !isFullDayOvertime) {
                          weekTotalHours += parseFloat(entry.total_hours) || 0;
                        }
                      }
                    });

                    let holidayHours = 0;
                    for (let d = new Date(startDate); d <= endDate; d.setDate(d.getDate() + 1)) {
                      const day = d.getDay();
                      if (day >= 1 && day <= 5) {
                        const dateStr = d.toISOString().split('T')[0];
                        if (holidaySet.has(dateStr)) holidayHours += fullDayHours;
                      }
                    }

                    // Variante B: Soll immer vertraglich, Verbleibend ohne Abzug „genommen“
                    //const sollStunden = (wochenstunden / arbeitstage) * workdays;
                    const sollStunden = wochenstunden;
                    const weekTotalHoursWithVacation = weekTotalHours + weekVacationHours + holidayHours;
                    const weekOvertimeHours = weekTotalHoursWithVacation - sollStunden;

                    totalOvertimeHours += weekOvertimeHours;
                    totalOvertimeTaken += weekOvertimeTaken;
                    processedWeeks++;

                    if (processedWeeks === weeks.length && !hasError) {
                      done(totalOvertimeHours + overtimeOffsetHours);
                    }
                  });
              }
            );
          });
        }
      );
    }
  );
}

module.exports = {
  getCurrentOvertimeForUser
};