/**
 * CollectorService — Field cash collection recording with FIFO allocation and zone enforcement.
 *
 * ARCHITECTURE:
 * This service handles the full collection lifecycle:
 * - Collector logs cash received from a subscriber (lump sum)
 * - FIFO allocation: oldest unpaid invoices (by dueDate) get allocated first
 * - Zone enforcement: collector can only collect from subscribers in their assigned zones
 * - Every collection creates a balanced JE: DR 1030 Cash in Transit, CR 1100 AR
 * - Void uses reversing journal entries — no deletions
 * - Collector balances derived from transactions (never stored)
 *
 * ACCOUNT CODES USED:
 *   1030 — Cash in Transit (cash in collector's hands, not yet remitted)
 *   1100 — Accounts Receivable (AR)
 *
 * JOURNAL ENTRY PATTERN (Collection):
 *   DR Cash in Transit (1030)      [amount collected]
 *   CR Accounts Receivable (1100)  [AR reduced]
 *
 * ZONE SECURITY BOUNDARY:
 * Enforced at data layer — collector cannot collect from subscribers
 * outside their assigned zones. Throws (not empty return) if violated.
 */

import { Prisma, InvoiceStatus, JournalEntrySource, CollectionStatus } from "@prisma/client";
import { JournalEntryService } from "@/lib/accounting/journal-entry-service";

// eslint-disable-next-line @typescript-eslint/no-explicit-any
type TenantPrismaClient = any;

// ---------------------------------------------------------------------------
// Input types
// ---------------------------------------------------------------------------

export interface RecordCollectionInput {
  /** The collector recording this collection */
  collectorId: string;
  /** The subscriber who paid */
  subscriberId: string;
  /** Total cash received */
  amount: number | string;
  /** When the cash was collected (economic date) */
  collectionDate: Date;
  notes?: string;
}

export interface CollectionAllocationRecord {
  invoiceId: string;
  amount: Prisma.Decimal;
}

export interface RecordCollectionResult {
  collection: {
    id: string;
    tenantId: string;
    collectorId: string;
    subscriberId: string;
    amount: Prisma.Decimal;
    collectionDate: Date;
    status: CollectionStatus;
    notes: string | null;
    journalEntryId: string | null;
    createdAt: Date;
    updatedAt: Date;
  };
  allocations: CollectionAllocationRecord[];
  journalEntryId: string;
}

export interface VoidCollectionResult {
  collection: unknown;
  voidJournalEntryId: string;
}

export interface GetCollectionHistoryOptions {
  page?: number;
  pageSize?: number;
}

export interface GetCollectionHistoryResult {
  collections: unknown[];
  total: number;
  page: number;
  pageSize: number;
}

// ---------------------------------------------------------------------------
// recordCollection
// ---------------------------------------------------------------------------

/**
 * Record a cash collection from a subscriber by a field collector.
 *
 * FIFO allocation: oldest unpaid invoices (by dueDate) get allocated first.
 * Zone enforcement: collector must be assigned to the subscriber's zone.
 *
 * Collection JE: DR 1030 Cash in Transit, CR 1100 Accounts Receivable
 *
 * @throws Error if amount <= 0, subscriber not found, or zone violation
 */
export async function recordCollection(
  tenantPrisma: TenantPrismaClient,
  tenantId: string,
  input: RecordCollectionInput
): Promise<RecordCollectionResult> {
  const { collectorId, subscriberId, amount: rawAmount, collectionDate, notes } = input;

  // Validate amount
  const amount = new Prisma.Decimal(rawAmount);
  if (amount.lessThanOrEqualTo(0)) {
    throw new Error("Collection amount must be greater than zero.");
  }

  // Validate subscriber exists within tenant
  const subscriber = await tenantPrisma.subscriber.findFirst({
    where: { id: subscriberId },
    select: { id: true, zoneId: true, firstName: true, lastName: true },
  });
  if (!subscriber) {
    throw new Error(`Subscriber not found: ${subscriberId}`);
  }

  // Zone enforcement: collector must be assigned to subscriber's zone
  if (!subscriber.zoneId) {
    throw new Error(
      `Subscriber ${subscriberId} is not assigned to any zone. ` +
      `Assign the subscriber to a zone before collecting.`
    );
  }

  // Check collector is assigned to subscriber's zone
  const zoneAssignment = await tenantPrisma.zoneAssignment.findFirst({
    where: { userId: collectorId, zoneId: subscriber.zoneId },
    select: { id: true },
  });
  if (!zoneAssignment) {
    throw new Error(
      `Collector ${collectorId} is not assigned to the zone of subscriber ${subscriberId}. ` +
      `Zone enforcement violation — collection rejected.`
    );
  }

  // Find required accounts
  const [transitAccount, arAccount] = await Promise.all([
    tenantPrisma.account.findFirst({ where: { code: "1030" }, select: { id: true } }),
    tenantPrisma.account.findFirst({ where: { code: "1100" }, select: { id: true } }),
  ]);

  if (!transitAccount || !arAccount) {
    throw new Error(
      `Required accounts (1030, 1100) not found for this tenant.`
    );
  }

  // FIFO: find unpaid/partial invoices ordered by dueDate ASC
  const unpaidInvoices = await tenantPrisma.invoice.findMany({
    where: {
      subscriberId,
      status: { in: [InvoiceStatus.SENT, InvoiceStatus.PARTIAL, InvoiceStatus.OVERDUE] },
    },
    orderBy: { dueDate: "asc" },
    select: {
      id: true,
      invoiceNumber: true,
      totalAmount: true,
      amountPaid: true,
      status: true,
    },
  });

  // FIFO allocation
  let remaining = new Prisma.Decimal(amount);
  const allocations: Array<{
    invoiceId: string;
    amount: Prisma.Decimal;
    newAmountPaid: Prisma.Decimal;
    newStatus: InvoiceStatus;
  }> = [];

  for (const invoice of unpaidInvoices) {
    if (remaining.lessThanOrEqualTo(0)) break;

    const invoiceTotal = new Prisma.Decimal(invoice.totalAmount);
    const alreadyPaid = new Prisma.Decimal(invoice.amountPaid);
    const invoiceOutstanding = invoiceTotal.minus(alreadyPaid);

    if (invoiceOutstanding.lessThanOrEqualTo(0)) continue;

    const allocateAmount = remaining.lessThan(invoiceOutstanding) ? remaining : invoiceOutstanding;
    const newAmountPaid = alreadyPaid.plus(allocateAmount);
    const isFullyPaid = newAmountPaid.greaterThanOrEqualTo(invoiceTotal);

    allocations.push({
      invoiceId: invoice.id,
      amount: allocateAmount,
      newAmountPaid,
      newStatus: isFullyPaid ? InvoiceStatus.PAID : InvoiceStatus.PARTIAL,
    });

    remaining = remaining.minus(allocateAmount);
  }

  // Build journal entry lines: DR 1030 Cash in Transit, CR 1100 AR
  // Note: if amount exceeds all invoices, AR credit is capped at invoiced amount
  const totalAllocated = allocations.reduce(
    (sum, a) => sum.plus(a.amount),
    new Prisma.Decimal(0)
  );

  const journalLines: Array<{
    accountId: string;
    debit: number;
    credit: number;
    description?: string;
  }> = [
    {
      accountId: transitAccount.id,
      debit: amount.toNumber(),
      credit: 0,
      description: `Cash collected from subscriber`,
    },
  ];

  if (totalAllocated.greaterThan(0)) {
    journalLines.push({
      accountId: arAccount.id,
      debit: 0,
      credit: totalAllocated.toNumber(),
      description: `AR reduction: ${totalAllocated.toFixed(2)}`,
    });
  }

  // If amount > invoices, the excess goes to 1030 but we still need to balance the JE.
  // For collections, excess cash stays in 1030 (collector holds it) — no credit balance.
  // The full amount DR 1030, CR 1100 for allocated portion only.
  // If no invoices to allocate against, DR 1030, CR 1100 with full amount (unapplied AR credit).
  if (totalAllocated.lessThanOrEqualTo(0) || totalAllocated.lessThan(amount)) {
    // Unallocated amount: still DR 1030 but we need a balancing CR
    // Use AR for the full amount — all cash collected reduces AR
    // Re-build with full amount on AR side
    journalLines.length = 0;
    journalLines.push(
      {
        accountId: transitAccount.id,
        debit: amount.toNumber(),
        credit: 0,
        description: `Cash collected from subscriber`,
      },
      {
        accountId: arAccount.id,
        debit: 0,
        credit: amount.toNumber(),
        description: `AR reduction: full collection`,
      }
    );
  }

  // Create journal entry (SYSTEM source — auto-posts)
  const journalEntry = await JournalEntryService.createEntry({
    tenantPrisma,
    tenantId,
    date: collectionDate,
    description: `Collection from subscriber by collector`,
    source: JournalEntrySource.SYSTEM,
    referenceType: "Collection",
    referenceId: `${collectorId}-${subscriberId}-${collectionDate.toISOString()}`,
    createdById: collectorId,
    lines: journalLines,
  });

  // Persist collection and allocations in a single transaction
  const result = await tenantPrisma.$transaction(async (tx: TenantPrismaClient) => {
    // Create collection record
    const collection = await tx.collection.create({
      data: {
        tenantId,
        collectorId,
        subscriberId,
        amount,
        collectionDate,
        status: CollectionStatus.COMPLETED,
        notes: notes ?? null,
        journalEntryId: journalEntry.id,
      },
    });

    // Create allocations and update invoice statuses
    for (const alloc of allocations) {
      await tx.collectionAllocation.create({
        data: {
          tenantId,
          collectionId: collection.id,
          invoiceId: alloc.invoiceId,
          amount: alloc.amount,
        },
      });

      // Update invoice amountPaid and status
      await tx.invoice.update({
        where: { id: alloc.invoiceId, tenantId },
        data: {
          amountPaid: alloc.newAmountPaid,
          status: alloc.newStatus,
          paidAt: alloc.newStatus === InvoiceStatus.PAID ? new Date() : null,
        },
      });
    }

    return collection;
  });

  return {
    collection: result,
    allocations: allocations.map((a) => ({ invoiceId: a.invoiceId, amount: a.amount })),
    journalEntryId: journalEntry.id,
  };
}

// ---------------------------------------------------------------------------
// voidCollection
// ---------------------------------------------------------------------------

/**
 * Void a collection by:
 * 1. Reversing all invoice allocations (recalculate amountPaid and status)
 * 2. Creating a reversing journal entry for the original collection JE
 * 3. Setting collection status to VOIDED
 *
 * @throws Error if collection not found, already VOIDED, or JE missing
 */
export async function voidCollection(
  tenantPrisma: TenantPrismaClient,
  tenantId: string,
  collectionId: string,
  voidedById: string
): Promise<VoidCollectionResult> {
  // Load the collection with allocations
  const collection = await tenantPrisma.collection.findFirst({
    where: { id: collectionId },
    include: { allocations: true },
  });

  if (!collection) {
    throw new Error(`Collection not found: ${collectionId}`);
  }

  if (collection.status === CollectionStatus.VOIDED) {
    throw new Error(`Collection ${collectionId} is already voided.`);
  }

  if (!collection.journalEntryId) {
    throw new Error(`Collection ${collectionId} has no associated journal entry — cannot void.`);
  }

  // Create reversing journal entry first
  const reversingEntry = await JournalEntryService.reverseEntry({
    tenantPrisma,
    tenantId,
    entryId: collection.journalEntryId,
    reversedById: voidedById,
    description: `Void of collection ${collection.id}`,
  });

  // Reverse allocations and update invoice statuses in a transaction
  const updatedCollection = await tenantPrisma.$transaction(async (tx: TenantPrismaClient) => {
    // Recalculate each invoice's amountPaid minus this collection's allocation
    for (const alloc of collection.allocations as Array<{
      invoiceId: string;
      amount: Prisma.Decimal;
    }>) {
      const invoice = await tx.invoice.findFirst({
        where: { id: alloc.invoiceId, tenantId },
        select: { id: true, totalAmount: true, amountPaid: true, status: true },
      });
      if (!invoice) continue;

      const currentAmountPaid = new Prisma.Decimal(invoice.amountPaid);
      const allocAmount = new Prisma.Decimal(alloc.amount);
      const newAmountPaid = currentAmountPaid.minus(allocAmount);
      const safeAmountPaid = newAmountPaid.lessThan(0) ? new Prisma.Decimal(0) : newAmountPaid;

      const total = new Prisma.Decimal(invoice.totalAmount);
      let newStatus: InvoiceStatus;
      if (safeAmountPaid.lessThanOrEqualTo(0)) {
        newStatus = InvoiceStatus.SENT;
      } else if (safeAmountPaid.greaterThanOrEqualTo(total)) {
        newStatus = InvoiceStatus.PAID;
      } else {
        newStatus = InvoiceStatus.PARTIAL;
      }

      await tx.invoice.update({
        where: { id: alloc.invoiceId, tenantId },
        data: {
          amountPaid: safeAmountPaid,
          status: newStatus,
          paidAt: newStatus === InvoiceStatus.PAID ? new Date() : null,
        },
      });
    }

    // Mark collection as VOIDED
    const updated = await tx.collection.update({
      where: { id: collectionId, tenantId },
      data: {
        status: CollectionStatus.VOIDED,
        voidedAt: new Date(),
        voidedById,
        voidJournalEntryId: reversingEntry.id,
      },
      include: { allocations: true },
    });

    return updated;
  });

  return {
    collection: updatedCollection,
    voidJournalEntryId: reversingEntry.id,
  };
}

// ---------------------------------------------------------------------------
// getCollectionHistory
// ---------------------------------------------------------------------------

/**
 * Get paginated collection history for a subscriber or collector, ordered by collectionDate desc.
 */
export async function getCollectionHistory(
  tenantPrisma: TenantPrismaClient,
  filter: { subscriberId?: string; collectorId?: string },
  options: GetCollectionHistoryOptions = {}
): Promise<GetCollectionHistoryResult> {
  const { page = 1, pageSize = 20 } = options;
  const skip = (page - 1) * pageSize;

  const where: Record<string, unknown> = {};
  if (filter.subscriberId) where.subscriberId = filter.subscriberId;
  if (filter.collectorId) where.collectorId = filter.collectorId;

  const [collections, total] = await Promise.all([
    tenantPrisma.collection.findMany({
      where,
      include: {
        allocations: {
          include: {
            invoice: {
              select: {
                id: true,
                invoiceNumber: true,
                totalAmount: true,
                amountPaid: true,
                status: true,
              },
            },
          },
        },
        collector: {
          select: { id: true, firstName: true, lastName: true },
        },
        subscriber: {
          select: { id: true, accountNumber: true, firstName: true, lastName: true },
        },
      },
      orderBy: { collectionDate: "desc" },
      skip,
      take: pageSize,
    }),
    tenantPrisma.collection.count({ where }),
  ]);

  return { collections, total, page, pageSize };
}