import Link from "next/link";
import { PoStatusBadge } from "@/components/po/po-status-badge";
import { LineItemsEditor } from "@/components/po/po-line-items-editor";
import { DiscardDraftButton } from "@/components/po/discard-draft-button";
import { SubmitDraftButton } from "@/components/po/submit-draft-button";
import { formatCurrency, formatDate, formatDateTime } from "@/lib/utils";
import { generateDownloadUrl } from "@/lib/storage";
import { TC_FIXED_LINE } from "@/lib/validations/po";
import type { LineItemInput } from "@/lib/validations/po";
import type { Role } from "@prisma/client";

type PoWithRelations = {
  id: string;
  poNumber: string;
  title: string;
  status: import("@prisma/client").POStatus;
  totalAmount: import("@prisma/client").Prisma.Decimal;
  currency: string;
  projectCode: string | null;
  dateRequired: Date | null;
  managerNote: string | null;
  paymentRef: string | null;
  paidAmount?: import("@prisma/client").Prisma.Decimal | null;
  piQuotationNo?: string | null;
  piQuotationDate?: Date | null;
  requisitionNo?: string | null;
  requisitionDate?: Date | null;
  placeOfDelivery?: string | null;
  tcDelivery?: string | null;
  tcDispatch?: string | null;
  tcInspection?: string | null;
  tcTransitInsurance?: string | null;
  tcPaymentTerms?: string | null;
  tcOthers?: string | null;
  createdAt: Date;
  submittedAt: Date | null;
  approvedAt: Date | null;
  paidAt: Date | null;
  closedAt: Date | null;
  submitter: { id: string; name: string; email: string };
  vessel: { id: string; name: string };
  account: { id: string; name: string; code: string };
  vendor: {
    id: string;
    name: string;
    vendorId: string | null;
    address?: string | null;
    gstin?: string | null;
    contactName?: string | null;
    contactMobile?: string | null;
    contactEmail?: string | null;
  } | null;
  lineItems: {
    id: string;
    name: string;
    description?: string | null;
    quantity: import("@prisma/client").Prisma.Decimal;
    unit: string;
    size?: string | null;
    unitPrice: import("@prisma/client").Prisma.Decimal;
    totalPrice: import("@prisma/client").Prisma.Decimal;
    gstRate?: import("@prisma/client").Prisma.Decimal | null;
    sortOrder: number;
  }[];
  documents: { id: string; fileName: string; fileSize: number; storageKey: string; uploadedAt: Date }[];
  actions: { id: string; actionType: string; note: string | null; metadata: import("@prisma/client").Prisma.JsonValue; createdAt: Date; actor: { name: string } }[];
};

interface Props {
  po: PoWithRelations;
  currentUserId: string;
  currentRole: Role;
  readOnly?: boolean;
}

const ACTION_LABELS: Record<string, string> = {
  CREATED: "Created",
  SUBMITTED: "Submitted for review",
  APPROVED: "Approved",
  APPROVED_WITH_NOTE: "Approved with note",
  REJECTED: "Rejected",
  EDITS_REQUESTED: "Edits requested",
  VENDOR_ID_REQUESTED: "Vendor ID requested",
  VENDOR_ID_PROVIDED: "Vendor ID provided",
  PAYMENT_SENT: "Payment confirmed",
  PARTIAL_PAYMENT_CONFIRMED: "Partial payment confirmed",
  RECEIPT_CONFIRMED: "Receipt confirmed",
  PARTIAL_RECEIPT_CONFIRMED: "Partial receipt confirmed",
  CLOSED: "Closed",
  MANAGER_LINE_EDIT: "Manager amended line items",
  PRODUCT_PRICE_UPDATED: "Product prices updated",
};

export async function PoDetail({ po, currentUserId, currentRole, readOnly = false }: Props) {
  const lineItemsForEditor = po.lineItems.map((li) => ({
    name: li.name,
    description: li.description ?? undefined,
    quantity: Number(li.quantity),
    unit: li.unit,
    size: li.size ?? undefined,
    unitPrice: Number(li.unitPrice),
    gstRate: li.gstRate != null ? Number(li.gstRate) : 0.18,
  }));

  const managerEditAction = [...po.actions]
    .reverse()
    .find((a) => a.actionType === "MANAGER_LINE_EDIT");

  const noteAction = [...po.actions]
    .reverse()
    .find((a) =>
      ["EDITS_REQUESTED", "REJECTED", "APPROVED", "APPROVED_WITH_NOTE"].includes(a.actionType) &&
      a.note
    );
  const managerNoteAuthor = noteAction?.actor.name ?? null;

  // Resubmit snapshot: stored in the most recent SUBMITTED action's metadata
  // when the submitter resubmits after EDITS_REQUESTED.
  type ResubmitSnapshot = {
    lineItems: LineItemInput[];
    fields: {
      title: string;
      vessel: string | null; vesselId: string;
      account: string; accountId: string;
      vendor: string | null; vendorId: string | null;
      projectCode: string | null; dateRequired: string | null; placeOfDelivery: string | null;
    };
  };
  const resubmitAction = [...po.actions]
    .reverse()
    .find(
      (a) =>
        a.actionType === "SUBMITTED" &&
        !!(a.metadata as { editSnapshot?: unknown } | null)?.editSnapshot
    );
  const resubmitSnapshot = resubmitAction
    ? (resubmitAction.metadata as { editSnapshot: ResubmitSnapshot }).editSnapshot
    : null;

  // Resubmit snapshot takes priority over manager line edit diff.
  const originalLineItems: LineItemInput[] | undefined = resubmitSnapshot?.lineItems
    ?? (managerEditAction
      ? (managerEditAction.metadata as { original: typeof lineItemsForEditor } | null)?.original
      : undefined);

  const lineItemsDiffLabel = resubmitSnapshot
    ? "Submitter updated these line items after edits were requested. Previous values shown with strikethrough."
    : "Line items were amended by manager. Current values shown; original values shown with strikethrough.";

  const downloadUrls = await Promise.all(
    po.documents.map((doc) => generateDownloadUrl(doc.storageKey))
  );

  const canConfirmReceipt =
    (po.status === "PAID_DELIVERED" || po.status === "PARTIALLY_CLOSED" || po.status === "PARTIALLY_PAID") &&
    (po.submitter.id === currentUserId || currentRole === "SUPERUSER") &&
    !readOnly;

  // Find the approver from actions
  const approvalAction = [...po.actions]
    .reverse()
    .find((a) => a.actionType === "APPROVED" || a.actionType === "APPROVED_WITH_NOTE");

  return (
    <div className="space-y-6">
      {/* Header */}
      <div className="flex items-start justify-between gap-4 flex-wrap">
        <div>
          <div className="flex items-center gap-3 mb-1">
            <span className="font-mono text-sm text-neutral-500">{po.poNumber}</span>
            <PoStatusBadge status={po.status} />
          </div>
          <h2 className="text-xl font-semibold text-neutral-900">{po.title}</h2>
        </div>
        <div className="flex items-center gap-2 flex-wrap">
          {["DRAFT", "EDITS_REQUESTED"].includes(po.status) &&
            (po.submitter.id === currentUserId || currentRole === "SUPERUSER") &&
            !readOnly && (
            <Link
              href={`/po/${po.id}/edit`}
              className="rounded-lg border border-neutral-300 bg-white px-3 py-2 text-sm font-medium text-neutral-700 hover:bg-neutral-50"
            >
              Edit
            </Link>
          )}
          {po.status === "DRAFT" &&
            (po.submitter.id === currentUserId || currentRole === "SUPERUSER") &&
            !readOnly && (
            <SubmitDraftButton poId={po.id} />
          )}
          {po.status === "DRAFT" &&
            (po.submitter.id === currentUserId || ["MANAGER", "SUPERUSER"].includes(currentRole)) &&
            !readOnly && (
            <DiscardDraftButton poId={po.id} />
          )}
          {/* Export buttons — only available once the PO has been approved by a manager */}
          {["MGR_APPROVED", "SENT_FOR_PAYMENT", "PARTIALLY_PAID", "PAID_DELIVERED", "PARTIALLY_CLOSED", "CLOSED"].includes(po.status) && (<>
            <a
              href={`/api/po/${po.id}/export?format=pdf`}
              target="_blank"
              rel="noopener noreferrer"
              className="rounded-lg border border-neutral-300 bg-white px-3 py-2 text-sm font-medium text-neutral-700 hover:bg-neutral-50"
            >
              Export PDF
            </a>
            <a
              href={`/api/po/${po.id}/export?format=xlsx`}
              className="rounded-lg border border-neutral-300 bg-white px-3 py-2 text-sm font-medium text-neutral-700 hover:bg-neutral-50"
            >
              Export XLSX
            </a>
          </>)}
        </div>
      </div>

      {/* Manager note banner */}
      {po.managerNote && (
        <div className="rounded-lg border border-warning-100 bg-warning-50 px-4 py-3">
          <p className="text-sm font-medium text-warning-700 mb-0.5">
            {managerNoteAuthor ? `Note from ${managerNoteAuthor}` : "Manager note"}
          </p>
          <p className="text-sm text-warning-700">{po.managerNote}</p>
        </div>
      )}

      {/* Submitter changes banner — shown to managers when PO is resubmitted after edits */}
      {resubmitSnapshot &&
        po.status === "MGR_REVIEW" &&
        (currentRole === "MANAGER" || currentRole === "SUPERUSER") && (() => {
          const snap = resubmitSnapshot.fields;
          const currentVessel = po.vessel?.name ?? null;
          const currentAccount = `${po.account.name} (${po.account.code})`;
          const currentVendor = po.vendor?.name ?? null;
          const currentDateRequired = po.dateRequired?.toISOString() ?? null;

          const fieldChanges: { label: string; before: string | null; after: string | null }[] = [];
          if (snap.title !== po.title)
            fieldChanges.push({ label: "Title", before: snap.title, after: po.title });
          if (snap.vesselId !== po.vessel.id)
            fieldChanges.push({ label: "Cost Centre", before: snap.vessel, after: currentVessel });
          if (snap.accountId !== po.account.id)
            fieldChanges.push({ label: "Account", before: snap.account, after: currentAccount });
          if (snap.vendorId !== (po.vendor?.id ?? null))
            fieldChanges.push({ label: "Vendor", before: snap.vendor ?? "None", after: currentVendor ?? "None" });
          if (snap.projectCode !== po.projectCode)
            fieldChanges.push({ label: "Project Code", before: snap.projectCode ?? "—", after: po.projectCode ?? "—" });
          if (snap.dateRequired !== currentDateRequired)
            fieldChanges.push({
              label: "Date Required",
              before: snap.dateRequired ? formatDate(snap.dateRequired) : "—",
              after: po.dateRequired ? formatDate(po.dateRequired) : "—",
            });
          if (snap.placeOfDelivery !== po.placeOfDelivery)
            fieldChanges.push({ label: "Place of Delivery", before: snap.placeOfDelivery ?? "—", after: po.placeOfDelivery ?? "—" });

          if (fieldChanges.length === 0) return null;

          return (
            <div className="rounded-lg border border-amber-200 bg-amber-50 p-4">
              <p className="text-sm font-semibold text-amber-800 mb-2">
                Submitter updated the following fields after edits were requested
              </p>
              <table className="w-full text-xs">
                <thead>
                  <tr className="border-b border-amber-200">
                    <th className="pb-1.5 text-left font-medium text-amber-700 w-32">Field</th>
                    <th className="pb-1.5 text-left font-medium text-amber-700 pl-4">Before</th>
                    <th className="pb-1.5 text-left font-medium text-amber-700 pl-4">After</th>
                  </tr>
                </thead>
                <tbody className="divide-y divide-amber-100">
                  {fieldChanges.map(({ label, before, after }) => (
                    <tr key={label}>
                      <td className="py-1.5 font-medium text-amber-700">{label}</td>
                      <td className="py-1.5 pl-4 text-neutral-500 line-through">{before}</td>
                      <td className="py-1.5 pl-4 font-medium text-amber-900">{after}</td>
                    </tr>
                  ))}
                </tbody>
              </table>
            </div>
          );
        })()}

      {/* Order Details */}
      <div className="rounded-lg border border-neutral-200 bg-white p-4 md:p-6">
        <h3 className="text-sm font-semibold text-neutral-900 mb-4">Order Details</h3>
        <dl className="grid grid-cols-1 sm:grid-cols-2 gap-x-6 gap-y-3 text-sm">
          <div><dt className="text-neutral-500">Cost Centre</dt><dd className="font-medium text-neutral-900">{po.vessel?.name ?? "—"}</dd></div>
          <div><dt className="text-neutral-500">Accounting Code</dt><dd className="font-medium text-neutral-900">{po.account.name} ({po.account.code})</dd></div>
          <div><dt className="text-neutral-500">Requested By</dt><dd className="font-medium text-neutral-900">{po.submitter.name}</dd></div>
          {approvalAction && (
            <div><dt className="text-neutral-500">Approved By</dt><dd className="font-medium text-neutral-900">{approvalAction.actor.name}</dd></div>
          )}
          {po.projectCode && <div><dt className="text-neutral-500">Project Code</dt><dd className="font-medium text-neutral-900">{po.projectCode}</dd></div>}
          {po.dateRequired && <div><dt className="text-neutral-500">Delivery Date Required</dt><dd className="font-medium text-neutral-900">{formatDate(po.dateRequired)}</dd></div>}
          {po.piQuotationNo && <div><dt className="text-neutral-500">PI / Quotation No.</dt><dd className="font-medium text-neutral-900">{po.piQuotationNo}</dd></div>}
          {po.piQuotationDate && <div><dt className="text-neutral-500">PI / Quotation Date</dt><dd className="font-medium text-neutral-900">{formatDate(po.piQuotationDate)}</dd></div>}
          {po.requisitionNo && <div><dt className="text-neutral-500">Requisition No.</dt><dd className="font-medium text-neutral-900">{po.requisitionNo}</dd></div>}
          {po.requisitionDate && <div><dt className="text-neutral-500">Requisition Date</dt><dd className="font-medium text-neutral-900">{formatDate(po.requisitionDate)}</dd></div>}
          {po.paymentRef && <div><dt className="text-neutral-500">Payment Ref</dt><dd className="font-mono text-sm text-neutral-900">{po.paymentRef}</dd></div>}
        </dl>
        {po.placeOfDelivery && (
          <div className="mt-3 pt-3 border-t border-neutral-100 text-sm">
            <dt className="text-neutral-500 mb-0.5">Place of Delivery</dt>
            <dd className="font-medium text-neutral-900 whitespace-pre-wrap">{po.placeOfDelivery}</dd>
          </div>
        )}
      </div>

      {/* Vendor */}
      {po.vendor ? (
        <div className="rounded-lg border border-neutral-200 bg-white p-4 md:p-6">
          <h3 className="text-sm font-semibold text-neutral-900 mb-3">Vendor</h3>
          <dl className="grid grid-cols-1 sm:grid-cols-2 gap-x-6 gap-y-2 text-sm">
            <div><dt className="text-neutral-500">Name</dt><dd className="font-medium text-neutral-900">{po.vendor.name}</dd></div>
            <div>
              <dt className="text-neutral-500">Vendor ID</dt>
              <dd className="font-medium text-neutral-900">
                {po.vendor.vendorId ?? (
                  <span className="inline-flex items-center rounded-full bg-warning-50 px-2 py-0.5 text-xs font-medium text-warning-700 ring-1 ring-inset ring-warning-200">
                    Not assigned
                  </span>
                )}
              </dd>
            </div>
            {po.vendor.gstin && (
              <div>
                <dt className="text-neutral-500">GSTIN</dt>
                <dd className="font-medium text-neutral-900 font-mono tracking-wide text-sm">{po.vendor.gstin}</dd>
              </div>
            )}
            {po.vendor.address && <div className="col-span-2"><dt className="text-neutral-500">Address</dt><dd className="font-medium text-neutral-900 whitespace-pre-wrap">{po.vendor.address}</dd></div>}
            {(po.vendor.contactName || po.vendor.contactMobile || po.vendor.contactEmail) && (
              <div className="col-span-2">
                <dt className="text-neutral-500">Contact</dt>
                <dd className="font-medium text-neutral-900">
                  {[po.vendor.contactName, po.vendor.contactMobile, po.vendor.contactEmail].filter(Boolean).join(" · ")}
                </dd>
              </div>
            )}
          </dl>
        </div>
      ) : (
        <div className="rounded-lg border border-warning-100 bg-warning-50 px-4 py-3">
          <p className="text-sm text-warning-700">No vendor assigned to this PO.</p>
        </div>
      )}

      {/* Line Items */}
      <div className="rounded-lg border border-neutral-200 bg-white p-3 md:p-6">
        <h3 className="text-sm font-semibold text-neutral-900 mb-4">Line Items</h3>
        <LineItemsEditor
          items={lineItemsForEditor}
          readOnly
          originalItems={originalLineItems}
          originalItemsLabel={lineItemsDiffLabel}
        />
      </div>

      {/* Terms & Conditions */}
      {(po.tcDelivery || po.tcDispatch || po.tcInspection || po.tcTransitInsurance || po.tcPaymentTerms || po.tcOthers) && (
        <div className="rounded-lg border border-neutral-200 bg-white p-6">
          <h3 className="text-sm font-semibold text-neutral-900 mb-3">Terms &amp; Conditions</h3>
          <ol className="space-y-1.5 text-sm text-neutral-700" style={{ listStyle: "none", padding: 0 }}>
            <li className="flex gap-2">
              <span className="shrink-0 font-medium text-neutral-500">1.</span>
              <span>{TC_FIXED_LINE}</span>
            </li>
            {([
              { n: 2, label: "DELIVERY",              value: po.tcDelivery },
              { n: 3, label: "DISPATCH INSTRUCTIONS", value: po.tcDispatch },
              { n: 4, label: "INSPECTION",            value: po.tcInspection },
              { n: 5, label: "TRANSIT INSURANCE",     value: po.tcTransitInsurance },
              { n: 6, label: "PAYMENT TERMS",         value: po.tcPaymentTerms },
              { n: 7, label: "OTHERS",                value: po.tcOthers },
            ] as const).filter(({ value }) => value).map(({ n, label, value }) => (
              <li key={n} className="flex gap-2">
                <span className="shrink-0 font-medium text-neutral-500">{n}.</span>
                <span><span className="font-medium">{label}:</span> {value}</span>
              </li>
            ))}
          </ol>
        </div>
      )}

      {/* Documents */}
      {po.documents.length > 0 && (
        <div className="rounded-lg border border-neutral-200 bg-white p-6">
          <h3 className="text-sm font-semibold text-neutral-900 mb-4">Attachments</h3>
          <ul className="space-y-2">
            {po.documents.map((doc, i) => (
              <li key={doc.id} className="flex items-center gap-3 text-sm">
                <a
                  href={downloadUrls[i]}
                  target="_blank"
                  rel="noopener noreferrer"
                  className="font-medium text-primary-600 hover:underline"
                >
                  {doc.fileName}
                </a>
                <span className="text-neutral-400 text-xs">
                  {(doc.fileSize / 1024).toFixed(0)} KB · {formatDate(doc.uploadedAt)}
                </span>
              </li>
            ))}
          </ul>
        </div>
      )}

      {/* Confirm receipt CTA */}
      {canConfirmReceipt && (
        <div className={`rounded-lg border p-5 flex items-center justify-between flex-wrap gap-3 ${
          po.status === "PARTIALLY_CLOSED" || po.status === "PARTIALLY_PAID"
            ? "border-warning-100 bg-warning-50"
            : "border-success-100 bg-success-50"
        }`}>
          <div>
            <p className={`font-medium ${po.status === "PARTIALLY_CLOSED" || po.status === "PARTIALLY_PAID" ? "text-warning-700" : "text-success-700"}`}>
              {po.status === "PARTIALLY_CLOSED"
                ? "Partially received"
                : po.status === "PARTIALLY_PAID"
                ? "Advance payment received"
                : "Payment confirmed"}
            </p>
            <p className={`text-sm mt-0.5 ${po.status === "PARTIALLY_CLOSED" || po.status === "PARTIALLY_PAID" ? "text-warning-700" : "text-success-700"}`}>
              {po.status === "PARTIALLY_CLOSED"
                ? "Some items are still outstanding. Confirm remaining deliveries."
                : po.status === "PARTIALLY_PAID"
                ? `Advance payment received (${formatCurrency(Number(po.paidAmount ?? 0), po.currency)} of ${formatCurrency(Number(po.totalAmount), po.currency)}). Items can be received now — PO closes when fully paid and delivered.`
                : "Please confirm that you have received all items."}
            </p>
          </div>
          <Link
            href={`/po/${po.id}/receipt`}
            className={`rounded-lg px-4 py-2.5 text-sm font-semibold text-white hover:opacity-90 ${
              po.status === "PARTIALLY_CLOSED" || po.status === "PARTIALLY_PAID" ? "bg-warning-600" : "bg-success"
            }`}
          >
            {po.status === "PARTIALLY_CLOSED" ? "Confirm Remaining" : "Confirm Receipt"}
          </Link>
        </div>
      )}

      {/* Audit trail */}
      <div className="rounded-lg border border-neutral-200 bg-white p-6">
        <h3 className="text-sm font-semibold text-neutral-900 mb-4">Activity</h3>
        <ol className="relative border-l border-neutral-200 ml-2 space-y-4">
          {po.actions.map((action) => (
            <li key={action.id} className="pl-5">
              <div className="absolute -left-1.5 mt-1.5 h-3 w-3 rounded-full border-2 border-white bg-neutral-400" />
              <div className="flex items-baseline gap-2">
                <span className="text-sm font-medium text-neutral-900">
                  {ACTION_LABELS[action.actionType] ?? action.actionType}
                </span>
                <span className="text-xs text-neutral-400">by {action.actor.name}</span>
                <span className="text-xs text-neutral-400 ml-auto">{formatDateTime(action.createdAt)}</span>
              </div>
              {action.note && (
                <p className="mt-1 text-sm text-neutral-600 italic">"{action.note}"</p>
              )}
            </li>
          ))}
        </ol>
      </div>
    </div>
  );
}