import { createHash } from 'node:crypto';
import type { Pool, PoolConnection } from 'mariadb';
import { customerSchema, deliverySchema, totalPrice, type Change, type Delivery, type Operation, type PullResponse } from '@model/shared';

export class SyncError extends Error {
  constructor(public code: string, public statusCode: number, message: string, public current?: Change) { super(message); }
}
function json<T>(value: string | T): T { return typeof value === 'string' ? JSON.parse(value) as T : value; }
function requestHashes(operation: Operation): string[] {
  const hashes = [createHash('sha256').update(JSON.stringify(operation)).digest('hex')];
  const addCompatibleHash = (compatible: unknown) => {
    const hash = createHash('sha256').update(JSON.stringify(compatible)).digest('hex');
    if (!hashes.includes(hash)) hashes.push(hash);
  };
  // V2 clients did not send the optional profile/structured-address defaults added in V3.
  // Accept only that exact old representation for an already-owned idempotency receipt.
  if (operation.kind === 'customer.create' && !operation.data.contactName && !operation.data.phone && !operation.data.comments && Object.values(operation.data.deliveryWindows).every(value => value === null)) {
    const legacy = { name: operation.data.name };
    addCompatibleHash({ ...operation, data: legacy });
  }
  if (operation.kind === 'address.create' && !operation.data.city && !operation.data.street && !operation.data.buildingNumber) {
    const legacy = { customerId: operation.data.customerId, label: operation.data.label, address: operation.data.address };
    addCompatibleHash({ ...operation, data: legacy });
  }
  let timingCompatible: Operation | undefined;
  if ((operation.kind === 'delivery.create' || operation.kind === 'delivery.update') && operation.data.deliverySlot == null && operation.data.specificTime == null && operation.data.deliveryWindow == null) {
    const { deliverySlot: _deliverySlot, specificTime: _specificTime, deliveryWindow: _deliveryWindow, ...legacy } = operation.data;
    timingCompatible = { ...operation, data: legacy } as Operation;
    addCompatibleHash(timingCompatible);
  }
  if (operation.kind === 'delivery.create' && operation.data.scheduledDate === null) {
    const { scheduledDate: _scheduledDate, ...legacy } = operation.data;
    addCompatibleHash({ ...operation, data: legacy });
    if (timingCompatible?.kind === 'delivery.create') {
      const { scheduledDate: _legacyScheduledDate, ...oldest } = timingCompatible.data;
      addCompatibleHash({ ...timingCompatible, data: oldest });
    }
  }
  return hashes;
}

export async function appendChange(conn: PoolConnection, change: Change) {
  // Caller holds sync_state FOR UPDATE through commit. Sequence order is commit order.
  await conn.query('UPDATE sync_state SET sequence = sequence + 1 WHERE id = 1');
  await conn.query('INSERT INTO sync_changes(sequence, entity_type, entity_id, change_json) SELECT sequence, ?, ?, ? FROM sync_state WHERE id = 1', [change.entityType, change.record.id, JSON.stringify(change)]);
}

export async function applyOperation(pool: Pool, operation: Operation, actorUserId: string | null = null) {
  const [requestHash, ...compatibleHashes] = requestHashes(operation);
  const conn = await pool.getConnection();
  try {
    await conn.beginTransaction();
    const state = await conn.query('SELECT next_delivery_number FROM sync_state WHERE id = 1 FOR UPDATE');
    if (!state.length) throw new Error('Database is not migrated');
    const previous = await conn.query('SELECT request_hash, result_json, actor_user_id FROM sync_operations WHERE operation_id = ?', [operation.operationId]);
    if (previous.length) {
      if (previous[0].request_hash !== requestHash && !compatibleHashes.includes(previous[0].request_hash)) throw new SyncError('OPERATION_REUSED', 409, 'Operation ID has different content');
      if (previous[0].actor_user_id && previous[0].actor_user_id !== actorUserId) throw new SyncError('OPERATION_OWNER_CHANGED', 409, 'Operation belongs to another account');
      await conn.commit();
      return { change: json<Change>(previous[0].result_json), replayed: true };
    }
    const entityType = operation.kind.split('.')[0]!;
    const existing = await conn.query('SELECT change_json FROM sync_changes WHERE entity_type = ? AND entity_id = ? ORDER BY sequence DESC LIMIT 1', [entityType, operation.entityId]);
    if (existing.length && operation.kind.endsWith('.create')) throw new SyncError('VERSION_CONFLICT', 409, 'Entity already exists', json<Change>(existing[0].change_json));

    const meta = { id: operation.entityId, version: 1, createdAt: new Date().toISOString(), deletedAt: null };
    let change: Change;
    if (operation.kind === 'customer.create') {
      const record = customerSchema.parse({ ...operation.data, ...meta, updatedAt: null });
      const windows = record.deliveryWindows;
      await conn.query('INSERT INTO customers(id, name, contact_name, phone, comments, morning_start, morning_end, afternoon_start, afternoon_end, late_night_start, late_night_end, created_at) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)', [record.id, record.name, record.contactName, record.phone, record.comments, windows.morning?.start ?? null, windows.morning?.end ?? null, windows.afternoon?.start ?? null, windows.afternoon?.end ?? null, windows.lateNight?.start ?? null, windows.lateNight?.end ?? null, record.createdAt]);
      change = { entityType: 'customer', record };
    } else if (operation.kind === 'customer.update' || operation.kind === 'customer.remove') {
      if (!existing.length) throw new SyncError('CUSTOMER_MISSING', 404, 'Customer is not available');
      const current = customerSchema.parse(json<Change>(existing[0].change_json).record);
      const currentChange: Change = { entityType: 'customer', record: current };
      if (current.version !== operation.baseVersion) throw new SyncError('VERSION_CONFLICT', 409, 'Customer changed on another device', currentChange);
      if (current.deletedAt) throw new SyncError('CUSTOMER_REMOVED', 409, 'Customer is archived', currentChange);
      const record = customerSchema.parse(operation.kind === 'customer.update'
        ? { ...current, ...operation.data, version: current.version + 1, updatedAt: meta.createdAt }
        : { ...current, version: current.version + 1, updatedAt: meta.createdAt, deletedAt: meta.createdAt });
      const windows = record.deliveryWindows;
      await conn.query('UPDATE customers SET name = ?, contact_name = ?, phone = ?, comments = ?, morning_start = ?, morning_end = ?, afternoon_start = ?, afternoon_end = ?, late_night_start = ?, late_night_end = ?, version = ?, updated_at = ?, deleted_at = ? WHERE id = ? AND version = ?', [record.name, record.contactName, record.phone, record.comments, windows.morning?.start ?? null, windows.morning?.end ?? null, windows.afternoon?.start ?? null, windows.afternoon?.end ?? null, windows.lateNight?.start ?? null, windows.lateNight?.end ?? null, record.version, record.updatedAt, record.deletedAt, record.id, operation.baseVersion]);
      change = { entityType: 'customer', record };
    } else if (operation.kind === 'address.create') {
      const record = { ...operation.data, ...meta };
      const customer = await conn.query('SELECT id FROM customers WHERE id = ? AND deleted_at IS NULL', [record.customerId]);
      if (!customer.length) throw new SyncError('CUSTOMER_MISSING', 422, 'Customer is not available');
      await conn.query('INSERT INTO customer_addresses(id, customer_id, label, address, city, street, building_number, created_at) VALUES (?, ?, ?, ?, ?, ?, ?, ?)', [record.id, record.customerId, record.label, record.address, record.city, record.street, record.buildingNumber, record.createdAt]);
      change = { entityType: 'address', record };
    } else if (operation.kind === 'delivery.create') {
      const data = operation.data;
      const address = await conn.query('SELECT a.id FROM customer_addresses a JOIN customers c ON c.id = a.customer_id WHERE a.id = ? AND a.customer_id = ? AND a.deleted_at IS NULL AND c.deleted_at IS NULL', [data.addressId, data.customerId]);
      if (!address.length) throw new SyncError('ADDRESS_MISMATCH', 422, 'Select an active address assigned to this customer');
      const types = await conn.query('SELECT version, shipment_unit_hundredths FROM delivery_types WHERE id = ? AND deleted_at IS NULL', [data.deliveryTypeId]);
      if (!types.length || types[0].version !== data.deliveryTypeVersion || types[0].shipment_unit_hundredths !== data.shipmentUnitHundredths) {
        throw new SyncError('CATALOG_CONFLICT', 409, 'Delivery type changed; the saved draft needs review');
      }
      const record = deliverySchema.parse({ ...data, ...meta, deliveryNumber: state[0].next_delivery_number as number, totalPriceAgorot: totalPrice(data.unitPriceAgorot, data.shipmentUnitHundredths), status: 'created' });
      await conn.query('UPDATE sync_state SET next_delivery_number = next_delivery_number + 1 WHERE id = 1');
      await conn.query('INSERT INTO deliveries(id, delivery_number, customer_id, address_id, scheduled_date, delivery_slot, specific_time, delivery_window_start, delivery_window_end, delivery_type_id, delivery_type_version, shipment_unit_hundredths, unit_price_agorot, total_price_agorot, notes, created_at) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)', [record.id, record.deliveryNumber, record.customerId, record.addressId, record.scheduledDate, record.deliverySlot, record.specificTime, record.deliveryWindow?.start ?? null, record.deliveryWindow?.end ?? null, record.deliveryTypeId, record.deliveryTypeVersion, record.shipmentUnitHundredths, record.unitPriceAgorot, record.totalPriceAgorot, record.notes, record.createdAt]);
      change = { entityType: 'delivery', record };
    } else {
      if (!existing.length) throw new SyncError('DELIVERY_MISSING', 404, 'Delivery is not available');
      const saved = json<Change>(existing[0].change_json);
      const current = deliverySchema.parse(saved.record);
      const currentChange: Change = { entityType: 'delivery', record: current };
      if (current.version !== operation.baseVersion) throw new SyncError('VERSION_CONFLICT', 409, 'Delivery changed on another device', currentChange);
      if (current.status === 'cancelled' || current.deletedAt) throw new SyncError('DELIVERY_CANCELLED', 409, 'Cancelled deliveries cannot be changed', currentChange);
      let record: Delivery = { ...current, version: current.version + 1, updatedAt: meta.createdAt };
      if (operation.kind === 'delivery.update') {
        const data = operation.data;
        const address = await conn.query('SELECT a.id FROM customer_addresses a JOIN customers c ON c.id = a.customer_id WHERE a.id = ? AND a.customer_id = ? AND a.deleted_at IS NULL AND c.deleted_at IS NULL', [data.addressId, data.customerId]);
        if (!address.length) throw new SyncError('ADDRESS_MISMATCH', 422, 'Select an active address assigned to this customer');
        record = deliverySchema.parse({ ...record, ...data, scheduledDate: data.scheduledDate ?? current.scheduledDate });
      } else record = { ...record, status: 'cancelled', cancelledAt: meta.createdAt, cancellationReason: operation.data.reason };
      await conn.query('UPDATE deliveries SET customer_id = ?, address_id = ?, scheduled_date = ?, delivery_slot = ?, specific_time = ?, delivery_window_start = ?, delivery_window_end = ?, notes = ?, status = ?, version = ?, updated_at = ?, cancelled_at = ?, cancellation_reason = ? WHERE id = ? AND version = ?', [record.customerId, record.addressId, record.scheduledDate, record.deliverySlot, record.specificTime, record.deliveryWindow?.start ?? null, record.deliveryWindow?.end ?? null, record.notes, record.status, record.version, record.updatedAt, record.cancelledAt, record.cancellationReason, record.id, operation.baseVersion]);
      change = { entityType: 'delivery', record };
    }
    await appendChange(conn, change);
    await conn.query('INSERT INTO sync_operations(operation_id, device_id, request_hash, result_json, created_at, actor_user_id) VALUES (?, ?, ?, ?, ?, ?)', [operation.operationId, operation.deviceId, requestHash, JSON.stringify(change), meta.createdAt, actorUserId]);
    await conn.commit();
    return { change, replayed: false };
  } catch (error) {
    await conn.rollback();
    throw error;
  } finally { conn.release(); }
}

export async function pullChanges(pool: Pool, cursor: string, limit = 100): Promise<PullResponse> {
  const conn = await pool.getConnection();
  try {
    const state = await conn.query('SELECT sequence FROM sync_state WHERE id = 1');
    if (BigInt(cursor) > BigInt(state[0].sequence)) throw new SyncError('CURSOR_AHEAD', 409, 'Server history is older than this device; restore or reconcile before syncing');
    const rows = await conn.query('SELECT sequence, change_json FROM sync_changes WHERE sequence > ? ORDER BY sequence LIMIT ?', [cursor, limit + 1]);
    const changes: PullResponse['changes'] = rows.slice(0, limit).map((row: { sequence: bigint; change_json: string }) => ({ sequence: String(row.sequence), change: json<Change>(row.change_json) }));
    return { changes, nextCursor: changes.at(-1)?.sequence ?? cursor, hasMore: rows.length > limit };
  } finally { conn.release(); }
}