const prisma = require('../config/db');

const METHOD_BUCKETS = ['cash', 'card', 'eft'];
const ALL_METHODS = ['cash', 'card', 'eft', 'other'];

// Standard South African Rand note/coin denominations used for the cash count grid.
const ZAR_DENOMINATIONS = [200, 100, 50, 20, 10, 5, 2, 1, 0.5, 0.2, 0.1];

function emptyByMethod(fill = 0) {
  return { cash: fill, card: fill, eft: fill, other: fill };
}

// Normalizes a free-text Payment.method into one of the fixed cashup buckets.
// Card-network wallets (Apple Pay, Google Pay, etc.) settle exactly like a card payment —
// no separate float to reconcile — so they belong in the 'card' bucket, not 'other'.
function bucketForMethod(method) {
  const m = String(method || '').toLowerCase();
  if (m.includes('cash')) return 'cash';
  if (m.includes('eft')) return 'eft';
  if (m.includes('card') || m.includes('yoco') || m.includes('pay')) return 'card';
  return 'other';
}

// A donation is never mutated once created — assigning it to a registration creates a separate
// "leg" Payment row (isDonation:false, originalPaymentId -> the donation, amount > 0) instead.
// That leg is not new money: it just re-labels part of an already-counted donation as applied
// to a registration. Revenue/cash totals must count each real inflow exactly once, so legs are
// excluded everywhere money is summed — the money was already counted via the donation itself.
// (Refunds also set originalPaymentId, but always with a negative amount, so they're unaffected.)
function isDonationLeg(p) {
  return !p.isDonation && !!p.originalPaymentId && p.amount > 0;
}

// Throws if the event is closed. Callers wrap this in their existing try/catch
// (res.statusCode is set before throwing, matching the rest of the controllers).
async function assertEventOpen(eventId, res) {
  const event = await prisma.event.findUnique({ where: { id: eventId }, select: { id: true, cashupStatus: true } });
  if (!event) {
    if (res) res.status(404);
    throw new Error('Event not found');
  }
  if (event.cashupStatus === 'closed') {
    if (res) res.status(400);
    throw new Error('This event is closed. Reopen it (admin only) before making changes.');
  }
  return event;
}

// Same check, but resolves the event via a registrationId first (for payment/registration flows
// that receive a registrationId rather than an eventId directly).
async function assertRegistrationEventOpen(registrationId, res) {
  const registration = await prisma.registration.findUnique({ where: { id: registrationId }, select: { eventId: true } });
  if (!registration) {
    if (res) res.status(404);
    throw new Error('Registration not found');
  }
  await assertEventOpen(registration.eventId, res);
  return registration;
}

// Core computation shared by the cashup preview/close endpoints and the Cashup/Finance/Profit reports.
//
// Two figures must never be conflated: "revenue" (gross, profit-relevant) and "expected cash"
// (net of any costs paid out of a method's float, for physically verifying a drawer/float).
// Mixing them up would double-subtract method-tagged costs from profit.
async function computeEventFinancials(eventId) {
  const event = await prisma.event.findUnique({
    where: { id: eventId },
    select: { id: true, title: true, cashupStatus: true, cashupDraft: true, closedAt: true, closedById: true, reopenedAt: true, reopenedById: true }
  });
  if (!event) {
    throw new Error('Event not found');
  }

  const [payments, costs, tickets, salesRows, history] = await Promise.all([
    prisma.payment.findMany({
      where: { OR: [{ eventId }, { registration: { eventId } }] }
    }),
    prisma.eventCost.findMany({ where: { eventId }, include: { eventOption: { select: { id: true, name: true } } } }),
    prisma.ticket.findMany({
      where: { eventId },
      include: { registrationOption: { select: { eventOptionId: true } } }
    }),
    prisma.registrationOption.findMany({
      where: { registration: { eventId, status: 'paid' } },
      include: { eventOption: { select: { id: true, name: true, price: true } }, tranches: true }
    }),
    prisma.eventCashup.findMany({
      where: { eventId },
      include: {
        lines: { include: { denominations: true } },
        performedBy: { select: { id: true, name: true, email: true } }
      },
      orderBy: { createdAt: 'desc' }
    })
  ]);

  // Ticket quantity sold per EventOption (used to price per-item costs)
  const quantityByOption = {};
  for (const t of tickets) {
    const optId = t.registrationOption?.eventOptionId;
    if (!optId) continue;
    quantityByOption[optId] = (quantityByOption[optId] || 0) + t.quantity;
  }

  // Excludes donation-application legs, which would otherwise double-count money already
  // counted once via the source donation (e.g. a R250 donation with R50 assigned to a
  // registration must total R250 received, not R300). Refunds (negative amount) are kept in —
  // a card refund must subtract from the 'card' bucket it was refunded against, not vanish from
  // the per-method breakdown while still being netted out of totalRevenue below.
  const realPayments = payments.filter(p => !isDonationLeg(p));
  // Donations are never mutated once assigned — assignment creates a separate "leg" Payment
  // row (isDonation:false, originalPaymentId -> the donation), so a donation's registrationId
  // stays null forever. Its actual unallocated amount is its original amount minus every leg
  // that already references it, not simply "every donation with no registrationId". A refund
  // of the donation itself also creates such a leg, with a negative amount — Math.abs() so a
  // refund reduces the unallocated balance instead of inflating it (a raw signed sum would
  // subtract a negative, adding the refund back on top).
  const legsByDonationId = new Map();
  for (const p of payments) {
    if (p.originalPaymentId && !p.isDonation) {
      legsByDonationId.set(p.originalPaymentId, (legsByDonationId.get(p.originalPaymentId) || 0) + Math.abs(p.amount));
    }
  }
  const donationPayments = payments.filter(p => p.isDonation);
  const unallocatedDonations = donationPayments.filter(p => (p.amount - (legsByDonationId.get(p.id) || 0)) > 0.000001);
  const unallocatedDonationsTotal = unallocatedDonations.reduce((sum, p) => sum + Math.max(p.amount - (legsByDonationId.get(p.id) || 0), 0), 0);
  const totalDonations = donationPayments.reduce((sum, p) => sum + p.amount, 0);

  const paymentsByMethod = emptyByMethod();
  for (const p of realPayments) {
    paymentsByMethod[bucketForMethod(p.method)] += p.amount;
  }
  const totalRevenue = payments.reduce((sum, p) => sum + (isDonationLeg(p) ? 0 : p.amount), 0);

  // Costs, with computed totals and attribution to a payment method's float (if tagged)
  const costBreakdown = costs.map(c => {
    const total = c.costType === 'per_item'
      ? c.amount * (quantityByOption[c.eventOptionId] || 0)
      : c.amount;
    return { ...c, total };
  });
  const costsByMethod = emptyByMethod();
  let untaggedCostsTotal = 0;
  for (const c of costBreakdown) {
    if (c.paidFromMethod && ALL_METHODS.includes(c.paidFromMethod)) {
      costsByMethod[c.paidFromMethod] += c.total;
    } else {
      untaggedCostsTotal += c.total;
    }
  }
  const totalCosts = untaggedCostsTotal + ALL_METHODS.reduce((s, m) => s + costsByMethod[m], 0);

  // What should physically be on hand per method, after known payouts from that float
  const expectedCashByMethod = emptyByMethod();
  for (const m of ALL_METHODS) expectedCashByMethod[m] = paymentsByMethod[m] - costsByMethod[m];

  // Most recent reconciliation on record (if any) — the source of "actual" truth
  const latestReconciled = history.find(h => h.action === 'closed' || h.action === 'quick_closed') || null;
  const reconciled = latestReconciled ? {
    id: latestReconciled.id,
    action: latestReconciled.action,
    createdAt: latestReconciled.createdAt,
    performedBy: latestReconciled.performedBy,
    notes: latestReconciled.notes,
    byMethod: (() => {
      const out = {};
      for (const m of ALL_METHODS) {
        const line = latestReconciled.lines.find(l => l.method === m);
        out[m] = {
          expected: line ? line.expectedAmount : expectedCashByMethod[m],
          actual: line && line.actualAmount != null ? line.actualAmount : null,
          variance: line && line.variance != null ? line.variance : null,
          notes: line ? line.notes : null,
          denominations: line ? line.denominations : []
        };
      }
      return out;
    })()
  } : null;

  // Reconciled value is truth; system (expected) value is the fallback when nothing was counted.
  // Tagged costs are added back so a reconciled cash count still yields a correct *gross* income figure —
  // costs get subtracted from profit exactly once, via totalCosts, never twice.
  const effectiveGrossIncomeByMethod = emptyByMethod();
  for (const m of ALL_METHODS) {
    const actual = reconciled?.byMethod?.[m]?.actual;
    const base = actual != null ? actual : expectedCashByMethod[m];
    effectiveGrossIncomeByMethod[m] = base + costsByMethod[m];
  }
  const effectiveTotalRevenue = ALL_METHODS.reduce((s, m) => s + effectiveGrossIncomeByMethod[m], 0);
  const netProfit = effectiveTotalRevenue - totalCosts;

  // What was actually sold, by ticket type — for the Finance report's income-stream breakdown.
  // Revenue is tranche-aware: a line spanning two early-bird prices contributes each tranche
  // at the price it was actually bought at, not one blended/stale price for the whole line.
  const { computeOptionLineTotal } = require('./pricing');
  const salesByOptionMap = {};
  for (const ro of salesRows) {
    const opt = ro.eventOption;
    if (!opt) continue;
    if (!salesByOptionMap[opt.id]) salesByOptionMap[opt.id] = { eventOptionId: opt.id, name: opt.name, quantitySold: 0, revenue: 0 };
    salesByOptionMap[opt.id].quantitySold += ro.quantity;
    salesByOptionMap[opt.id].revenue += computeOptionLineTotal(ro, null, new Date());
  }
  const salesByOption = Object.values(salesByOptionMap);

  return {
    event,
    paymentsByMethod,
    totalRevenue,
    costs: costBreakdown,
    costsByMethod,
    untaggedCostsTotal,
    totalCosts,
    expectedCashByMethod,
    reconciled,
    effectiveGrossIncomeByMethod,
    effectiveTotalRevenue,
    netProfit,
    unallocatedDonations,
    unallocatedDonationsTotal,
    totalDonations,
    salesByOption,
    history
  };
}

// Payment accountability, per staff member who recorded the payment, broken down by every
// method (not just cash) — lets a cashup reconcile not just the total float but who is
// responsible for which portion of it. Cash also folds in any actual physical count entered for
// that person (EventCashupPersonCount, entered any time, independent of the event-wide close) to
// show an actual-vs-expected variance per person — the event's cash actual is the sum of these
// per-person counts (see computeEventCashActualFromPersonCounts), not a separate manual entry.
// Card/EFT/Other have no physical "count" concept, so they're just recorded amounts.
async function computeAccountabilityByUser(eventId) {
  const [payments, personCounts] = await Promise.all([
    prisma.payment.findMany({
      where: { OR: [{ eventId }, { registration: { eventId } }] },
      include: { recordedBy: { select: { id: true, name: true, email: true } } }
    }),
    prisma.eventCashupPersonCount.findMany({
      where: { eventId },
      include: {
        user: { select: { id: true, name: true, email: true } },
        enteredBy: { select: { id: true, name: true } },
        denominations: true
      }
    })
  ]);

  const emptyMethodTotals = () => ({ total: 0, count: 0 });
  const emptyEntry = (userId, name, email) => ({
    userId: userId || null,
    name: name || 'Unknown / legacy',
    email: email || null,
    cash: { ...emptyMethodTotals(), actual: null, variance: null, denominations: [], enteredBy: null, countUpdatedAt: null, notes: null },
    card: emptyMethodTotals(),
    eft: emptyMethodTotals(),
    other: emptyMethodTotals()
  });

  const byUser = new Map();
  for (const p of payments) {
    // A donation-application leg isn't new money — it's the same money already recorded once,
    // as the donation. Counting it again here would double-attribute it to whoever did the
    // assignment, on top of whoever originally recorded the donation.
    if (isDonationLeg(p)) continue;
    const method = bucketForMethod(p.method);
    const key = p.recordedById || 'unknown';
    const entry = byUser.get(key) || emptyEntry(p.recordedById, p.recordedBy?.name, p.recordedBy?.email);
    entry[method].total += p.amount;
    entry[method].count += 1;
    byUser.set(key, entry);
  }

  for (const pc of personCounts) {
    const key = pc.userId;
    const entry = byUser.get(key) || emptyEntry(pc.userId, pc.user?.name, pc.user?.email);
    const actual = pc.denominations.reduce((s, d) => s + d.value * d.count, 0);
    entry.cash.actual = actual;
    entry.cash.variance = actual - entry.cash.total;
    entry.cash.denominations = pc.denominations.map(d => ({ value: d.value, count: d.count }));
    entry.cash.enteredBy = pc.enteredBy ? { id: pc.enteredBy.id, name: pc.enteredBy.name } : null;
    entry.cash.countUpdatedAt = pc.updatedAt;
    entry.cash.notes = pc.notes || null;
    byUser.set(key, entry);
  }

  return Array.from(byUser.values()).sort((a, b) => {
    const totalA = a.cash.total + a.card.total + a.eft.total + a.other.total;
    const totalB = b.cash.total + b.card.total + b.eft.total + b.other.total;
    return totalB - totalA;
  });
}

// The event's cash "actual" is the live sum of every staff member's entered physical count —
// there is no separate event-wide entry any more. Used both to display a live figure before
// close and to source the closed cashup's permanent Cash line.
async function computeEventCashActualFromPersonCounts(eventId) {
  const personCounts = await prisma.eventCashupPersonCount.findMany({
    where: { eventId },
    include: { denominations: true }
  });
  if (personCounts.length === 0) return { actual: null, denominations: [] };

  const byValue = new Map();
  let actual = 0;
  for (const pc of personCounts) {
    for (const d of pc.denominations) {
      actual += d.value * d.count;
      byValue.set(d.value, (byValue.get(d.value) || 0) + d.count);
    }
  }
  const denominations = Array.from(byValue.entries())
    .map(([value, count]) => ({ value, count }))
    .sort((a, b) => b.value - a.value);
  return { actual, denominations };
}

// Upsert one staff member's actual physical cash count for an event — optional, can be entered
// any time (not required to close the event), purely for per-person accountability.
async function savePersonCashCount(eventId, userId, { denominations, notes, enteredById }) {
  const cleanDenoms = (Array.isArray(denominations) ? denominations : [])
    .map(d => ({ value: Number(d.value), count: parseInt(d.count, 10) || 0 }))
    .filter(d => d.value > 0 && d.count > 0);

  const existing = await prisma.eventCashupPersonCount.findUnique({
    where: { eventId_userId: { eventId, userId } }
  });

  const record = existing
    ? await prisma.eventCashupPersonCount.update({
        where: { id: existing.id },
        data: {
          notes: notes || null,
          enteredById: enteredById || null,
          denominations: { deleteMany: {}, create: cleanDenoms }
        },
        include: { denominations: true }
      })
    : await prisma.eventCashupPersonCount.create({
        data: {
          eventId,
          userId,
          notes: notes || null,
          enteredById: enteredById || null,
          denominations: { create: cleanDenoms }
        },
        include: { denominations: true }
      });

  return record;
}

module.exports = {
  METHOD_BUCKETS,
  ALL_METHODS,
  ZAR_DENOMINATIONS,
  bucketForMethod,
  isDonationLeg,
  assertEventOpen,
  assertRegistrationEventOpen,
  computeEventFinancials,
  computeAccountabilityByUser,
  computeEventCashActualFromPersonCounts,
  savePersonCashCount
};