const prisma = require('../config/db');
const { safeErrorMessage } = require('../utils/errorUtils');
const { logAdminAction } = require('../utils/adminAudit');
const { getClientIp } = require('../utils/requestUtils');
const { KINDS, describeBundle, describeBundleItems, isBundleAvailable } = require('../utils/bundles');
const { previewBundles } = require('../utils/coupons');
const { basketBuyer, priceBasket } = require('./couponController');

const round2 = (n) => Math.round(Number(n || 0) * 100) / 100;
const fmtR = (n) => `R${Number(n || 0).toFixed(2).replace(/\.00$/, '')}`;
const GROUP_PRICING = ['per_ticket', 'percent'];

const optionalDate = (v, label) => {
  if (v === undefined) return undefined;
  if (v === null || v === '') return null;
  const d = new Date(v);
  if (isNaN(d.getTime())) throw new Error(`${label} is not a valid date`);
  return d;
};

/** Standard (variant or option) price of one unit of an item. */
function itemPrice(i) {
  const variant = i.variantId ? (i.eventOption?.variants || []).find(v => v.id === i.variantId) : null;
  return Number((variant && variant.price !== null && variant.price !== undefined ? variant.price : i.eventOption?.price) || 0);
}

/**
 * What the deal is worth at standard prices: `standardValue` is what an exact set costs
 * separately (or the dearest pick-any set); `savingText` is a short "save …" line, or
 * null when the headline already says it.
 */
function valueOf(bundle) {
  const kind = bundle.kind || 'exact';
  const items = bundle.items || [];
  const dearest = items.reduce((m, i) => Math.max(m, itemPrice(i)), 0);
  const price = Number(bundle.price || 0);
  if (kind === 'exact') {
    const standard = round2(items.reduce((s, i) => s + itemPrice(i) * Number(i.quantity || 0), 0));
    return { standardValue: standard, savingText: standard - price > 0.005 ? `save ${fmtR(standard - price)}` : null };
  }
  if (kind === 'mix') {
    const standard = round2(dearest * Number(bundle.setSize || 0));
    return { standardValue: standard, savingText: standard - price > 0.005 ? `save up to ${fmtR(standard - price)}` : null };
  }
  if (kind === 'free') {
    return { standardValue: null, savingText: dearest > 0 ? `save up to ${fmtR(dearest * Number(bundle.freeCount || 0))} a set` : null };
  }
  if (bundle.groupPricing === 'per_ticket' && dearest - price > 0.005) {
    return { standardValue: null, savingText: `save up to ${fmtR(dearest - price)} a ticket` };
  }
  return { standardValue: null, savingText: null };
}

// Items with prices loaded, so the standard value can be shown next to the bundle price.
const DETAIL_INCLUDE = {
  items: {
    include: {
      eventOption: { select: { id: true, name: true, price: true, variants: { select: { id: true, price: true } } } },
      variant: { select: { id: true, name: true } },
    },
  },
};

function shape(bundle, now = new Date()) {
  const items = (bundle.items || []).map(({ eventOption, ...i }) => ({ ...i, eventOption: eventOption ? { id: eventOption.id, name: eventOption.name, price: eventOption.price } : null }));
  return {
    ...bundle,
    items,
    summary: describeBundleItems(bundle),
    headline: describeBundle(bundle),
    ...valueOf(bundle),
    available: isBundleAvailable(bundle, now),
  };
}

const PRICING_FIELDS = ['kind', 'price', 'setSize', 'freeCount', 'groupPricing', 'items'];

/**
 * Turns a create/update body into Prisma data plus the item list. On update, fields
 * left out of the body are left alone; when any pricing field is sent, the bundle as a
 * whole (saved values plus the new ones) is checked. Items must belong to the event.
 */
async function parseBundleBody(body, eventId, { isCreate, current = null }) {
  const data = {};
  if (isCreate || body.name !== undefined) {
    const name = String(body.name || '').trim();
    if (!name) throw new Error('Give the bundle a name');
    if (name.length > 80) throw new Error('Keep the name under 80 characters');
    data.name = name;
  }
  if (body.description !== undefined) data.description = body.description ? String(body.description).trim() : null;
  if (body.isActive !== undefined) data.isActive = !!body.isActive;
  if (body.order !== undefined) data.order = Number.isInteger(Number(body.order)) ? Number(body.order) : 0;
  const validFrom = optionalDate(body.validFrom, 'Available from');
  const validUntil = optionalDate(body.validUntil, 'Available until');
  if (validFrom !== undefined) data.validFrom = validFrom;
  if (validUntil !== undefined) data.validUntil = validUntil;
  if (validFrom && validUntil && validFrom > validUntil) throw new Error('"Available from" must be before "Available until"');

  let items;
  if (!isCreate && !PRICING_FIELDS.some(f => body[f] !== undefined)) return { data, items };

  const pick = (f) => (body[f] !== undefined ? body[f] : current?.[f]);
  const kind = pick('kind') || 'exact';
  if (!KINDS.includes(kind)) throw new Error('Unknown bundle type');
  data.kind = kind;

  const rawItems = body.items !== undefined ? body.items : (current?.items || []);
  // The same option/variant twice becomes one line.
  const merged = new Map();
  for (const it of Array.isArray(rawItems) ? rawItems : []) {
    if (!it || !it.eventOptionId) continue;
    const quantity = kind === 'exact' ? Number(it.quantity) : 1;
    if (!Number.isInteger(quantity) || quantity < 1) throw new Error('Each ticket needs a quantity of at least 1');
    const key = `${it.eventOptionId}::${it.variantId || ''}`;
    const prev = merged.get(key);
    merged.set(key, { eventOptionId: it.eventOptionId, variantId: it.variantId || null, quantity: kind === 'exact' ? (prev?.quantity || 0) + quantity : 1 });
  }
  items = [...merged.values()];
  if (items.length === 0) throw new Error(kind === 'exact' ? 'Add at least one ticket to the bundle' : 'Choose at least one qualifying ticket');

  const price = Number(pick('price'));
  const setSize = Number(pick('setSize'));
  const freeCount = Number(pick('freeCount'));
  const groupPricing = pick('groupPricing');
  const priceGiven = pick('price') !== '' && pick('price') !== null && pick('price') !== undefined;

  if (kind === 'exact') {
    if (items.reduce((s, i) => s + i.quantity, 0) < 2) throw new Error('A bundle needs at least two tickets in it');
    if (!priceGiven || !(price >= 0)) throw new Error('Enter the bundle price (zero or more)');
    Object.assign(data, { price: round2(price), setSize: null, freeCount: null, groupPricing: null });
  } else if (kind === 'mix') {
    if (!Number.isInteger(setSize) || setSize < 2) throw new Error('A pick-any bundle needs at least 2 tickets per set');
    if (!priceGiven || !(price >= 0)) throw new Error('Enter the price for the set (zero or more)');
    Object.assign(data, { price: round2(price), setSize, freeCount: null, groupPricing: null });
  } else if (kind === 'free') {
    if (!Number.isInteger(freeCount) || freeCount < 1) throw new Error('At least one ticket must be free');
    if (!Number.isInteger(setSize) || setSize <= freeCount) throw new Error('Buy at least one ticket to get the free ones');
    Object.assign(data, { price: 0, setSize, freeCount, groupPricing: null });
  } else {
    if (!Number.isInteger(setSize) || setSize < 2) throw new Error('A group needs at least 2 tickets');
    if (!GROUP_PRICING.includes(groupPricing)) throw new Error('Choose a price per ticket or a percentage off');
    if (groupPricing === 'percent' && !(price > 0 && price <= 100)) throw new Error('Enter a percentage between 1 and 100');
    if (groupPricing === 'per_ticket' && (!priceGiven || !(price >= 0))) throw new Error('Enter the price per ticket (zero or more)');
    Object.assign(data, { price: round2(price), setSize, freeCount: null, groupPricing });
  }

  const options = await prisma.eventOption.findMany({
    where: { id: { in: items.map(i => i.eventOptionId) } },
    select: { id: true, eventId: true, variants: { select: { id: true } } },
  });
  for (const i of items) {
    const row = options.find(o => o.id === i.eventOptionId);
    if (!row || row.eventId !== eventId) throw new Error('One of the tickets isn\'t part of this event');
    if (i.variantId && !row.variants.some(v => v.id === i.variantId)) throw new Error('One of the selected variants no longer exists');
  }
  return { data, items };
}

async function eventOr404(eventId, res) {
  const event = await prisma.event.findUnique({ where: { id: eventId }, select: { id: true, title: true } });
  if (!event) { res.status(404); throw new Error('Event not found'); }
  return event;
}

// @desc    An event's bundle deals with how often each has been used
// @route   GET /api/bundles/event/:eventId
// @access  Private/Supervisor
const listBundles = async (req, res) => {
  try {
    await eventOr404(req.params.eventId, res);
    const bundles = await prisma.eventBundle.findMany({
      where: { eventId: req.params.eventId },
      include: DETAIL_INCLUDE,
      orderBy: [{ order: 'asc' }, { createdAt: 'asc' }],
    });
    const totals = await prisma.registrationBundle.groupBy({
      by: ['bundleId'],
      where: { bundle: { eventId: req.params.eventId }, registration: { status: { not: 'cancelled' } } },
      _sum: { count: true, discount: true },
      _count: { _all: true },
    });
    const byId = Object.fromEntries(totals.map(t => [t.bundleId, t]));
    const now = new Date();
    res.json(bundles.map(b => ({
      ...shape(b, now),
      uses: byId[b.id]?._sum?.count || 0,
      registrations: byId[b.id]?._count?._all || 0,
      totalDiscount: round2(byId[b.id]?._sum?.discount || 0),
    })));
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

// @desc    Create a bundle deal
// @route   POST /api/bundles/event/:eventId
// @access  Private/Supervisor
const createBundle = async (req, res) => {
  try {
    const event = await eventOr404(req.params.eventId, res);
    let parsed;
    try {
      parsed = await parseBundleBody(req.body || {}, event.id, { isCreate: true });
    } catch (e) { res.status(400); throw e; }
    const bundle = await prisma.eventBundle.create({
      data: { ...parsed.data, eventId: event.id, items: { create: parsed.items } },
      include: DETAIL_INCLUDE,
    });
    logAdminAction({
      actorId: req.user.id, actorRole: req.user.role, action: 'bundle_created',
      targetType: 'EventBundle', targetId: bundle.id,
      metadata: { eventId: event.id, name: bundle.name, kind: bundle.kind, deal: describeBundle(bundle) },
      ip: getClientIp(req),
    });
    res.status(201).json({ ...shape(bundle), uses: 0, registrations: 0, totalDiscount: 0 });
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

// @desc    Edit a bundle deal (including switching it off). Registrations that already
//          have it are only re-worked when their own items change.
// @route   PUT /api/bundles/:id
// @access  Private/Supervisor
const updateBundle = async (req, res) => {
  try {
    const existing = await prisma.eventBundle.findUnique({ where: { id: req.params.id }, include: { items: true } });
    if (!existing) { res.status(404); throw new Error('Bundle not found'); }
    let parsed;
    try {
      parsed = await parseBundleBody(req.body || {}, existing.eventId, { isCreate: false, current: existing });
    } catch (e) { res.status(400); throw e; }
    const bundle = await prisma.eventBundle.update({
      where: { id: existing.id },
      data: { ...parsed.data, ...(parsed.items ? { items: { deleteMany: {}, create: parsed.items } } : {}) },
      include: DETAIL_INCLUDE,
    });
    logAdminAction({
      actorId: req.user.id, actorRole: req.user.role, action: 'bundle_updated',
      targetType: 'EventBundle', targetId: bundle.id,
      metadata: { eventId: bundle.eventId, name: bundle.name, changedKeys: Object.keys(req.body || {}) },
      ip: getClientIp(req),
    });
    res.json(shape(bundle));
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

// @desc    Delete a bundle deal. One that's been used is switched off instead, so the
//          registrations that got it keep their price.
// @route   DELETE /api/bundles/:id
// @access  Private/Supervisor
const deleteBundle = async (req, res) => {
  try {
    const existing = await prisma.eventBundle.findUnique({ where: { id: req.params.id } });
    if (!existing) { res.status(404); throw new Error('Bundle not found'); }
    const used = await prisma.registrationBundle.count({ where: { bundleId: existing.id } });
    if (used > 0) {
      await prisma.eventBundle.update({ where: { id: existing.id }, data: { isActive: false } });
    } else {
      await prisma.eventBundle.delete({ where: { id: existing.id } });
    }
    logAdminAction({
      actorId: req.user.id, actorRole: req.user.role, action: 'bundle_deleted',
      targetType: 'EventBundle', targetId: existing.id,
      metadata: { eventId: existing.eventId, name: existing.name, switchedOff: used > 0 },
      ip: getClientIp(req),
    });
    res.json(used > 0
      ? { switchedOff: true, message: 'This bundle has been used, so it\'s been switched off instead. Registrations that got it keep their price.' }
      : { deleted: true, message: 'Bundle deleted' });
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

// @desc    The bundle deals a basket gets, before any coupon code
// @route   POST /api/bundles/quote
// @access  Public. Body: { eventId, options: [{ eventOptionId, variantId?, quantity }], forUserId? }
const quoteBundles = async (req, res) => {
  try {
    const { eventId, options, forUserId } = req.body || {};
    if (!eventId || !Array.isArray(options)) { res.status(400); throw new Error('eventId and options are required'); }
    const event = await prisma.event.findUnique({
      where: { id: eventId },
      include: { eventOptions: { include: { earlyBirdTiers: true, variants: true } } },
    });
    if (!event) { res.status(404); throw new Error('Event not found'); }
    const { buyer } = await basketBuyer(req, forUserId);
    const lines = await priceBasket(event, options, buyer);
    const subtotal = round2(lines.reduce((s, l) => s + l.unitPrice * l.quantity, 0));
    const bundles = await previewBundles(eventId, lines);
    res.json({
      subtotal,
      bundleDiscount: bundles.discount,
      bundles: bundles.applications,
      total: round2(Math.max(0, subtotal - bundles.discount)),
    });
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

/** The deals to show on an event's page: available bundles, without internal fields. */
async function publicBundlesForEvent(eventId) {
  const bundles = await prisma.eventBundle.findMany({
    where: { eventId, isActive: true },
    include: DETAIL_INCLUDE,
    orderBy: [{ order: 'asc' }, { createdAt: 'asc' }],
  });
  const now = new Date();
  return bundles.filter(b => isBundleAvailable(b, now)).map(b => {
    const s = shape(b, now);
    return {
      id: s.id, name: s.name, description: s.description, validUntil: s.validUntil,
      kind: s.kind, price: s.price, setSize: s.setSize, freeCount: s.freeCount, groupPricing: s.groupPricing,
      summary: s.summary, headline: s.headline, standardValue: s.standardValue, savingText: s.savingText,
      items: s.items.map(i => ({ eventOptionId: i.eventOptionId, variantId: i.variantId, quantity: i.quantity })),
    };
  });
}

module.exports = { listBundles, createBundle, updateBundle, deleteBundle, quoteBundles, publicBundlesForEvent };