import { err, ok, type CommandContext } from "@tailor-platform/erp-kit/core";
import { Decimal } from "decimal.js";
import type { Selectable, Transaction } from "../generated/kysely-tailordb";
import { ApAcquisitionCostAdjustmentFailedError } from "../lib/errors.generated";
import type { InventoryCommands, PurchaseQueries } from "../module";

type AccountPayableDocument = Selectable<"AccountPayableDocument">;
type AccountPayableDocumentLine = Selectable<"AccountPayableDocumentLine">;

/**
 * Declares each purchase-order sourced line's price variance against the order
 * to inventory, which adjusts the acquisition cost of the received stock.
 */
export async function postAcquisitionCostAdjustment(
  db: Transaction,
  input: {
    document: AccountPayableDocument;
    lines: AccountPayableDocumentLine[];
  },
  ctx: CommandContext,
  purchaseQueries: Pick<PurchaseQueries, "listPurchaseOrderLinesForMatching">,
  inventoryCommands: Pick<InventoryCommands, "postAcquisitionCostAdjustment">,
) {
  const { document } = input;
  const adjustmentLines = input.lines.flatMap((line) => {
    if (
      line.sourceType !== "PURCHASE_ORDER" ||
      line.purchaseOrderLineId === null ||
      line.quantity === null ||
      line.unitPrice === null
    ) {
      return [];
    }
    // An AMOUNT correction declares money that is not per-unit goods cost
    // (charges, lump-sum credits), so it stays in AP and never adjusts inventory.
    if (line.correctionType === "AMOUNT") return [];
    return [
      {
        id: line.id,
        purchaseOrderLineId: line.purchaseOrderLineId,
        quantity: line.quantity,
        unitPrice: line.unitPrice,
        matchedPurchaseOrderUnitPrice: line.matchedPurchaseOrderUnitPrice,
        correctionType: line.correctionType,
      },
    ];
  });
  if (adjustmentLines.length === 0) return ok(undefined);

  const purchaseOrderLineIds = [
    ...new Set(adjustmentLines.map((line) => line.purchaseOrderLineId)),
  ];
  const { purchaseOrderLines } = (
    await purchaseQueries.listPurchaseOrderLinesForMatching(db, { purchaseOrderLineIds }, ctx)
  ).value;
  const purchaseOrderLineById = new Map(
    purchaseOrderLines.map((purchaseOrderLine) => [purchaseOrderLine.id, purchaseOrderLine]),
  );

  const isInvoice = document.documentType === "INVOICE";
  const varianceLines = [];
  for (const line of adjustmentLines) {
    const purchaseOrderLine = purchaseOrderLineById.get(line.purchaseOrderLineId);
    if (!purchaseOrderLine) return err(new ApAcquisitionCostAdjustmentFailedError(line.id));

    // A PRICE correction's unitPrice is already the per-unit change; other lines
    // compare against the matched price, since a later change declares its own.
    let perUnit: Decimal;
    if (line.correctionType === "PRICE") {
      perUnit = new Decimal(line.unitPrice);
    } else {
      if (line.matchedPurchaseOrderUnitPrice === null) {
        return err(new ApAcquisitionCostAdjustmentFailedError(line.id));
      }
      perUnit = new Decimal(line.unitPrice).minus(line.matchedPurchaseOrderUnitPrice);
    }
    // Line values are positive; the document type carries the direction.
    const amount = perUnit.mul(line.quantity).mul(isInvoice ? 1 : -1);
    if (amount.isZero()) continue;

    varianceLines.push({
      sourceLineId: line.id,
      purchaseOrderId: purchaseOrderLine.purchaseOrderId,
      purchaseOrderLineId: line.purchaseOrderLineId,
      amount: amount.toString(),
    });
  }
  if (varianceLines.length === 0) return ok(undefined);

  const adjustmentResult = await inventoryCommands.postAcquisitionCostAdjustment(
    db,
    {
      sourceType: "ACCOUNT_PAYABLE_DOCUMENT",
      sourceId: document.id,
      varianceKind: "INVOICE_PRICE",
      effectiveDate: document.postingDate,
      lines: varianceLines,
    },
    ctx,
  );
  if (!adjustmentResult.ok) return err(new ApAcquisitionCostAdjustmentFailedError(document.id));

  return ok(undefined);
}

/**
 * Declares the matched-versus-current price difference on the quantity a
 * cancelled REGISTERED document returns to the unbilled pool.
 */
export async function postCancellationCostCompensation(
  db: Transaction,
  input: {
    document: AccountPayableDocument;
    lines: AccountPayableDocumentLine[];
  },
  ctx: CommandContext,
  purchaseQueries: Pick<PurchaseQueries, "listPurchaseOrderLinesForMatching">,
  inventoryCommands: Pick<InventoryCommands, "postAcquisitionCostAdjustment">,
) {
  const { document } = input;
  // PRICE and AMOUNT corrections carry no billed quantity, so their
  // cancellation moves nothing between the pools.
  const matchedLines = input.lines.flatMap((line) => {
    if (
      line.sourceType !== "PURCHASE_ORDER" ||
      line.purchaseOrderLineId === null ||
      line.quantity === null
    ) {
      return [];
    }
    if (line.correctionType === "PRICE" || line.correctionType === "AMOUNT") return [];
    return [
      {
        id: line.id,
        purchaseOrderLineId: line.purchaseOrderLineId,
        quantity: line.quantity,
        matchedPurchaseOrderUnitPrice: line.matchedPurchaseOrderUnitPrice,
      },
    ];
  });
  if (matchedLines.length === 0) return ok(undefined);

  const purchaseOrderLineIds = [...new Set(matchedLines.map((line) => line.purchaseOrderLineId))];
  const { purchaseOrderLines } = (
    await purchaseQueries.listPurchaseOrderLinesForMatching(db, { purchaseOrderLineIds }, ctx)
  ).value;
  const purchaseOrderLineById = new Map(
    purchaseOrderLines.map((purchaseOrderLine) => [purchaseOrderLine.id, purchaseOrderLine]),
  );

  const isCreditMemo = document.documentType === "CREDIT_MEMO";
  const compensationLines = [];
  for (const line of matchedLines) {
    const purchaseOrderLine = purchaseOrderLineById.get(line.purchaseOrderLineId);
    if (!purchaseOrderLine) return err(new ApAcquisitionCostAdjustmentFailedError(line.id));
    if (line.matchedPurchaseOrderUnitPrice === null) {
      return err(new ApAcquisitionCostAdjustmentFailedError(line.id));
    }
    const amount = new Decimal(purchaseOrderLine.unitPrice)
      .minus(line.matchedPurchaseOrderUnitPrice)
      .mul(line.quantity)
      .mul(isCreditMemo ? -1 : 1);
    if (amount.isZero()) continue;

    compensationLines.push({
      sourceLineId: line.id,
      purchaseOrderId: purchaseOrderLine.purchaseOrderId,
      purchaseOrderLineId: line.purchaseOrderLineId,
      amount: amount.toString(),
    });
  }
  if (compensationLines.length === 0) return ok(undefined);

  const adjustmentResult = await inventoryCommands.postAcquisitionCostAdjustment(
    db,
    {
      sourceType: "ACCOUNT_PAYABLE_DOCUMENT",
      sourceId: document.id,
      varianceKind: "ORDER_PRICE",
      effectiveDate: new Date(),
      lines: compensationLines,
    },
    ctx,
  );
  if (!adjustmentResult.ok) return err(new ApAcquisitionCostAdjustmentFailedError(document.id));

  return ok(undefined);
}