// services/quarterService.js

/**
 * Get Quarter and Month details based on current quarter and Calander year
 * @param {number} currentYear - e.g. 2025
 * @param {string} currentQuarter - e.g. 'Q4'
 * @returns {object} - structured period data
 */
exports.getQuarterPeriods =  (currentYear, currentQuarter) => {
    // Define quarters based on Calander year (Jan–Dec)
    const quarters = {
      Q1: ["Jan", "Feb", "Mar"],
      Q2: ["Apr", "May", "Jun"],
      Q3: ["Jul", "Aug", "Sep"],
      Q4: ["Oct", "Nov", "Dec"],
    };
  
    const allQuarters = ["Q1", "Q2", "Q3", "Q4"];
    const currentIndex = allQuarters.indexOf(currentQuarter);
  
    if (currentIndex === -1) {
      throw new Error("Invalid quarter. Use one of: Q1, Q2, Q3, Q4");
    }
  
    // --- Previous Quarter ---
    let previousQuarter = allQuarters[(currentIndex - 1 + 4) % 4];
    let previousYear = currentYear;
    
    if (currentQuarter === "Q1") {
      previousYear = currentYear - 1;
    } 
  
    // --- Forecast Quarter ---
    let forecastQuarter = allQuarters[(currentIndex + 1) % 4];
    let forecastYear = currentYear;
    // If next quarter is Q1, then financial year increments
    if (forecastQuarter === "Q1") {
      forecastYear = currentYear + 1;
    }
  
    // Construct Output Object
    const output = {
      previous_month: {
        previous_period_one: quarters[previousQuarter][0],
        previous_period_two: quarters[previousQuarter][1],
        previous_period_three: quarters[previousQuarter][2],
      },
      previous_year: previousYear,
      previous_quarter: previousQuarter,
  
      current_month: {
        current_period_one: quarters[currentQuarter][0],
        current_period_two: quarters[currentQuarter][1],
        current_period_three: quarters[currentQuarter][2],
      },
      current_year: currentYear,
      current_quarter: currentQuarter,
  
      forecast_month: {
        forecast_period_one: quarters[forecastQuarter][0],
        forecast_period_two: quarters[forecastQuarter][1],
        forecast_period_three: quarters[forecastQuarter][2],
      },
      forecast_year: forecastYear,
      forecast_quarter: forecastQuarter,
    };
  
    return output;
  };