import moment from 'moment';

/***************************************************
 * HELPER: Approx State Tax Rates
 ***************************************************/
const APPROX_STATE_TAX_RATES = {
  AL: 0.05, AK: 0.00, AZ: 0.025, AR: 0.05, CA: 0.07, CO: 0.045, CT: 0.055, DE: 0.05,
  FL: 0.00, GA: 0.05, HI: 0.06, ID: 0.058, IL: 0.05, IN: 0.035, IA: 0.05, KS: 0.05,
  KY: 0.05, LA: 0.04, ME: 0.055, MD: 0.05, MA: 0.05, MI: 0.0425, MN: 0.06, MS: 0.04,
  MO: 0.05, MT: 0.05, NE: 0.05, NV: 0.00, NH: 0.00, NJ: 0.057, NM: 0.045, NY: 0.06,
  NC: 0.0475, ND: 0.02, OH: 0.04, OK: 0.045, OR: 0.07, PA: 0.03, RI: 0.045, SC: 0.04,
  SD: 0.00, TN: 0.00, TX: 0.00, UT: 0.045, VT: 0.055, VA: 0.05, WA: 0.00, WV: 0.05,
  WI: 0.05, WY: 0.00, DC: 0.05
};

/***************************************************
 * HELPER: Federal Tax Brackets
 ***************************************************/
const STANDARD_DEDUCTION_SINGLE = 13850;
function calculateAnnualFederalTaxSingle(annualTaxable) {
  const brackets = [
    { limit: 11000,    rate: 0.10 },
    { limit: 44725,    rate: 0.12 },
    { limit: 95375,    rate: 0.22 },
    { limit: 182100,   rate: 0.24 },
    { limit: 231250,   rate: 0.32 },
    { limit: 578125,   rate: 0.35 },
    { limit: Infinity, rate: 0.37 }
  ];

  let tax = 0;
  let lastLimit = 0;
  for (let i = 0; i < brackets.length; i++) {
    const { limit, rate } = brackets[i];
    if (annualTaxable <= limit) {
      tax += (annualTaxable - lastLimit) * rate;
      break;
    } else {
      tax += (limit - lastLimit) * rate;
      lastLimit = limit;
    }
  }
  return tax;
}

/***************************************************
 * HELPER: Monthly Federal Tax (no YTD)
 * We just treat (monthlyGross * 12) - standardDed
 * -> bracket -> / 12
 ***************************************************/
function calculateMonthlyFedTaxNoYTD(monthlyGross) {
  const annualGross = monthlyGross * 12;
  let annualTaxable = annualGross - STANDARD_DEDUCTION_SINGLE;
  if (annualTaxable < 0) annualTaxable = 0;

  const annualTax = calculateAnnualFederalTaxSingle(annualTaxable);
  return annualTax / 12;
}

/***************************************************
 * HELPER: Monthly State Tax (no YTD)
 * Uses GA (5%) by default if user doesn't override
 ***************************************************/
function calculateMonthlyStateTaxNoYTD(monthlyGross, stateCode = 'GA') {
  const rate = APPROX_STATE_TAX_RATES[stateCode] ?? 0.05;
  return monthlyGross * rate;
}

/***************************************************
 * HELPER: Loan Payment (if not deferring)
 ***************************************************/
function calculateLoanPayment(principal, annualRate, years) {
  if (principal <= 0) return 0;
  const monthlyRate = annualRate / 100 / 12;
  const numPayments = years * 12;

  if (monthlyRate === 0) {
    return principal / numPayments;
  }
  return (
    (principal * monthlyRate) /
    (1 - Math.pow(1 + monthlyRate, -numPayments))
  );
}

/***************************************************
 * MAIN SIMULATION FUNCTION
 ***************************************************/
export function simulateFinancialProjection(userProfile) {
  /***************************************************
   * 1) DESTRUCTURE USER PROFILE
   ***************************************************/
  const {
    // Basic incomes
    currentSalary = 0,
    monthlyExpenses = 0,
    monthlyDebtPayments = 0,
    partTimeIncome = 0,
    extraPayment = 0,

    // Student loan config
    studentLoanAmount = 0,
    interestRate = 5,
    loanTerm = 10,
    loanDeferralUntilGraduation = false,

    // College config
    inCollege = false,
    programType,
    hoursCompleted = 0,
    creditHoursPerYear,
    calculatedTuition,
    gradDate,
    startDate,
    academicCalendar = 'monthly',
    annualFinancialAid = 0,

    // Post-college salary
    expectedSalary = 0,

    // Savings & monthly contributions
    emergencySavings = 0,
    retirementSavings = 0,
    monthlyRetirementContribution = 0,
    monthlyEmergencyContribution = 0,

    // Surplus distribution
    surplusEmergencyAllocation = 50,
    surplusRetirementAllocation = 50,

    // Program length override
    programLength,

    // State code for taxes (default to GA if not provided)
    stateCode = 'GA',

    // Financial milestone impacts
    milestoneImpacts = []
  } = userProfile;

  /***************************************************
   * 2) CLAMP THE SCENARIO START TO MONTH-BEGIN
   ***************************************************/
  const scenarioStartClamped = moment(startDate || new Date()).startOf('month');

  /***************************************************
   * 3) DETERMINE PROGRAM LENGTH (credit hours)
   ***************************************************/
  let requiredCreditHours = 120;
  switch (programType) {
    case "Associate's Degree":
      requiredCreditHours = 60;
      break;
    case "Master's Degree":
      requiredCreditHours = 30;
      break;
    case "Doctoral Degree":
      requiredCreditHours = 60;
      break;
    // else Bachelor's = 120
  }
  const remainingCreditHours = Math.max(0, requiredCreditHours - hoursCompleted);
  const dynamicProgramLength = Math.ceil(
    remainingCreditHours / (creditHoursPerYear || 30)
  );
  const finalProgramLength = programLength || dynamicProgramLength;

  /***************************************************
   * 4) TUITION CALC: lumps, deferral, etc.
   ***************************************************/
  const netAnnualTuition = Math.max(0, (calculatedTuition || 0) - (annualFinancialAid || 0));
  const totalTuitionCost = netAnnualTuition * finalProgramLength;

  let lumpsPerYear, lumpsSchedule;
  switch (academicCalendar) {
    case 'semester':
      lumpsPerYear = 2;
      lumpsSchedule = [0, 6];
      break;
    case 'quarter':
      lumpsPerYear = 4;
      lumpsSchedule = [0, 3, 6, 9];
      break;
    case 'trimester':
      lumpsPerYear = 3;
      lumpsSchedule = [0, 4, 8];
      break;
    case 'monthly':
    default:
      lumpsPerYear = 12;
      lumpsSchedule = [...Array(12).keys()];
      break;
  }
  const totalAcademicMonths = finalProgramLength * 12;
  const lumpAmount = totalTuitionCost / (lumpsPerYear * finalProgramLength);

  /***************************************************
   * 5) LOAN PAYMENT (if not deferring)
   ***************************************************/
  let monthlyLoanPayment = loanDeferralUntilGraduation
    ? 0
    : calculateLoanPayment(studentLoanAmount, interestRate, loanTerm);

  /***************************************************
   * 6) SETUP FOR THE SIMULATION LOOP
   ***************************************************/
  const maxMonths = 240; // 20 years
  let loanBalance = Math.max(studentLoanAmount, 0);
  let loanPaidOffMonth = null;

  let currentEmergencySavings = emergencySavings;
  let currentRetirementSavings = retirementSavings;

  let projectionData = [];

  // Keep track of YTD gross & tax for reference
  let fedYTDgross = 0;
  let fedYTDtax = 0;
  let stateYTDgross = 0;
  let stateYTDtax = 0;

  let wasInDeferral = inCollege && loanDeferralUntilGraduation;
  const graduationDateObj = gradDate ? moment(gradDate).startOf('month') : null;

  console.log('simulateFinancialProjection - monthly tax approach');
  console.log('scenarioStartClamped:', scenarioStartClamped.format('YYYY-MM-DD'));

  /***************************************************
   * 7) THE MONTHLY LOOP
   ***************************************************/
  for (let monthIndex = 0; monthIndex < maxMonths; monthIndex++) {
    // date for this iteration
    const currentSimDate = scenarioStartClamped.clone().add(monthIndex, 'months');

    // check if loan is fully paid
    if (loanBalance <= 0 && !loanPaidOffMonth) {
      loanPaidOffMonth = currentSimDate.format('YYYY-MM');
    }

    // Are we still in college?
    let stillInCollege = false;
    if (inCollege) {
      if (graduationDateObj) {
        stillInCollege = currentSimDate.isBefore(graduationDateObj, 'month');
      } else {
        stillInCollege = (monthIndex < totalAcademicMonths);
      }
    }

    /************************************************
     * 7.1 TUITION lumps
     ************************************************/
    let tuitionCostThisMonth = 0;
    if (stillInCollege && lumpsPerYear > 0) {
      const academicYearIndex = Math.floor(monthIndex / 12);
      const monthInYear = monthIndex % 12;
      if (lumpsSchedule.includes(monthInYear) && academicYearIndex < finalProgramLength) {
        tuitionCostThisMonth = lumpAmount;
      }
    }

    // If deferring tuition => add to loan, no direct expense
    if (stillInCollege && loanDeferralUntilGraduation && tuitionCostThisMonth > 0) {
      loanBalance += tuitionCostThisMonth;
      tuitionCostThisMonth = 0;
    }

    /************************************************
     * 7.2 BASE MONTHLY INCOME
     ************************************************/
    let baseMonthlyIncome = 0;
    if (!stillInCollege) {
      // user is out of college => expected or current
      baseMonthlyIncome = (expectedSalary || currentSalary) / 12;
    } else {
      // in college => might have partTimeIncome + current
      baseMonthlyIncome = (currentSalary / 12) + (partTimeIncome / 12);
    }

    /************************************************
     * 7.3 MILESTONE IMPACTS
     ************************************************/
    let extraImpactsThisMonth = 0;
    milestoneImpacts.forEach((impact) => {
      const startDateClamped = moment(impact.start_date).startOf('month');
      let startOffset = startDateClamped.diff(scenarioStartClamped, 'months');
      if (startOffset < 0) startOffset = 0;

      let endOffset = Infinity;
      if (impact.end_date && impact.end_date.trim() !== '') {
        const endDateClamped = moment(impact.end_date).startOf('month');
        endOffset = endDateClamped.diff(scenarioStartClamped, 'months');
        if (endOffset < 0) endOffset = 0;
      }

      if (impact.impact_type === 'ONE_TIME') {
        if (monthIndex === startOffset) {
          if (impact.direction === 'add') {
            baseMonthlyIncome += impact.amount;
          } else {
            extraImpactsThisMonth += impact.amount;
          }
        }
      } else {
        // 'MONTHLY'
        if (monthIndex >= startOffset && monthIndex <= endOffset) {
          if (impact.direction === 'add') {
            baseMonthlyIncome += impact.amount;
          } else {
            extraImpactsThisMonth += impact.amount;
          }
        }
      }
    });

    /************************************************
     * 7.4 CALCULATE TAXES (No YTD approach)
     ************************************************/
    const monthlyFederalTax = calculateMonthlyFedTaxNoYTD(baseMonthlyIncome);
    const monthlyStateTax = calculateMonthlyStateTaxNoYTD(baseMonthlyIncome, stateCode);
    const combinedTax = monthlyFederalTax + monthlyStateTax;

    // net after tax
    const netMonthlyIncome = baseMonthlyIncome - combinedTax;

    // increment YTD gross & tax for reference
    fedYTDgross   += baseMonthlyIncome;
    fedYTDtax     += monthlyFederalTax;
    stateYTDgross += baseMonthlyIncome;
    stateYTDtax   += monthlyStateTax;

    /************************************************
     * 7.5 LOAN + EXPENSES
     ************************************************/
    const nowExitingCollege = wasInDeferral && !stillInCollege;
    if (nowExitingCollege) {
      monthlyLoanPayment = calculateLoanPayment(loanBalance, interestRate, loanTerm);
    }

    let totalMonthlyExpenses = monthlyExpenses + monthlyDebtPayments + tuitionCostThisMonth + extraImpactsThisMonth;

    if (stillInCollege && loanDeferralUntilGraduation) {
      // accumulate interest
      const interestForMonth = loanBalance * (interestRate / 100 / 12);
      loanBalance += interestForMonth;
    } else {
      // pay principal
      if (loanBalance > 0) {
        const interestForMonth = loanBalance * (interestRate / 100 / 12);
        const principalForMonth = Math.min(
          loanBalance,
          (monthlyLoanPayment + extraPayment) - interestForMonth
        );
        loanBalance = Math.max(loanBalance - principalForMonth, 0);

        totalMonthlyExpenses += (monthlyLoanPayment + extraPayment);
      }
    }

    let leftover = netMonthlyIncome - totalMonthlyExpenses;

    // baseline contributions
    const baselineContributions = monthlyRetirementContribution + monthlyEmergencyContribution;
    let effectiveRetirementContribution = 0;
    let effectiveEmergencyContribution = 0;

    if (leftover >= baselineContributions) {
      effectiveRetirementContribution = monthlyRetirementContribution;
      effectiveEmergencyContribution = monthlyEmergencyContribution;
      leftover -= baselineContributions;
    }

    const actualExpensesPaid = totalMonthlyExpenses + effectiveRetirementContribution + effectiveEmergencyContribution;
    let shortfall = actualExpensesPaid - netMonthlyIncome;

    // cover shortfall with emergency
    if (shortfall > 0) {
      const canCover = Math.min(shortfall, currentEmergencySavings);
      currentEmergencySavings -= canCover;
      shortfall -= canCover;
      // leftover -= shortfall; // if you want negative leftover
    }

    // Surplus => leftover
    if (leftover > 0) {
      const totalPct = surplusEmergencyAllocation + surplusRetirementAllocation;
      const emergPortion = leftover * (surplusEmergencyAllocation / totalPct);
      const retPortion = leftover * (surplusRetirementAllocation / totalPct);

      currentEmergencySavings += emergPortion;
      currentRetirementSavings += retPortion;
    }

    // net savings
    const netSavings = netMonthlyIncome - actualExpensesPaid;

    projectionData.push({
      month: currentSimDate.format('YYYY-MM'),
      grossMonthlyIncome: +baseMonthlyIncome.toFixed(2),
      monthlyFederalTax: +monthlyFederalTax.toFixed(2),
      monthlyStateTax: +monthlyStateTax.toFixed(2),
      combinedTax: +combinedTax.toFixed(2),
      netMonthlyIncome: +netMonthlyIncome.toFixed(2),

      totalExpenses: +actualExpensesPaid.toFixed(2),
      effectiveRetirementContribution: +effectiveRetirementContribution.toFixed(2),
      effectiveEmergencyContribution: +effectiveEmergencyContribution.toFixed(2),

      netSavings: +netSavings.toFixed(2),
      emergencySavings: +currentEmergencySavings.toFixed(2),
      retirementSavings: +currentRetirementSavings.toFixed(2),
      loanBalance: +loanBalance.toFixed(2),

      // actual loan payment
      loanPaymentThisMonth: +(monthlyLoanPayment + extraPayment).toFixed(2),

      // YTD references
      fedYTDgross: +fedYTDgross.toFixed(2),
      fedYTDtax: +fedYTDtax.toFixed(2),
      stateYTDgross: +stateYTDgross.toFixed(2),
      stateYTDtax: +stateYTDtax.toFixed(2),
    });

    // update deferral
    wasInDeferral = stillInCollege && loanDeferralUntilGraduation;
  }

  return {
    projectionData,
    loanPaidOffMonth,
    finalEmergencySavings: +currentEmergencySavings.toFixed(2),
    finalRetirementSavings: +currentRetirementSavings.toFixed(2),
    finalLoanBalance: +loanBalance.toFixed(2),

    // Final YTD totals
    fedYTDgross: +fedYTDgross.toFixed(2),
    fedYTDtax: +fedYTDtax.toFixed(2),
    stateYTDgross: +stateYTDgross.toFixed(2),
    stateYTDtax: +stateYTDtax.toFixed(2),
  };
}