"use client";

import Link from "next/link";
import { useState } from "react";
import { useRouter } from "next/navigation";
import {
  Badge,
  Button,
  Card,
  ErrorBanner,
  Input,
  PageHeader,
} from "@/components/ui";
import { apiFetch, ApiClientError } from "@/lib/client-api";

interface POInfo {
  id: string;
  vendor: string;
  status: string;
  createdAt: string;
  sentAt: string | null;
  receivedAt: string | null;
  notes: string | null;
}

interface LineRow {
  id: string;
  fastener: {
    id: string;
    partNumber: string;
    description: string;
    supplier: string | null;
    unitCost: number | null;
  };
  qty: number;
  receivedQty: number;
  unitCost: number | null;
}

const STATUS_TONE: Record<string, "slate" | "blue" | "green" | "amber" | "red"> = {
  draft: "slate",
  sent: "blue",
  partial: "amber",
  received: "green",
  cancelled: "red",
};

function formatDate(iso: string | null) {
  if (!iso) return "—";
  return new Date(iso).toLocaleDateString(undefined, {
    year: "numeric",
    month: "short",
    day: "numeric",
  });
}

export default function POClient({
  project,
  po,
  lines,
}: {
  project: { id: string; code: string; name: string };
  po: POInfo;
  lines: LineRow[];
}) {
  const router = useRouter();
  const [error, setError] = useState<string | null>(null);
  const [busy, setBusy] = useState(false);

  // Per-line receive input. Keyed by line id so re-renders don't clobber state.
  const [receipts, setReceipts] = useState<Record<string, string>>({});

  const total = lines.reduce((a, l) => {
    const cost = l.unitCost ?? l.fastener.unitCost ?? 0;
    return a + cost * l.qty;
  }, 0);
  const totalReceived = lines.reduce((a, l) => a + l.receivedQty, 0);
  const totalQty = lines.reduce((a, l) => a + l.qty, 0);

  async function changeStatus(next: string) {
    if (!confirm(`Move PO to "${next}"?`)) return;
    setBusy(true);
    setError(null);
    try {
      await apiFetch(`/api/v1/purchase-orders/${po.id}/status`, {
        method: "POST",
        body: JSON.stringify({ status: next }),
      });
      router.refresh();
    } catch (err) {
      setError(err instanceof ApiClientError ? err.message : "Status change failed");
    } finally {
      setBusy(false);
    }
  }

  async function submitReceipts() {
    const payload = Object.entries(receipts)
      .map(([lineId, qty]) => ({ lineId, qty: Number(qty) }))
      .filter((r) => r.qty > 0);
    if (payload.length === 0) {
      setError("Enter at least one receipt quantity");
      return;
    }
    setBusy(true);
    setError(null);
    try {
      await apiFetch(`/api/v1/purchase-orders/${po.id}/receive`, {
        method: "POST",
        body: JSON.stringify({ receipts: payload }),
      });
      setReceipts({});
      router.refresh();
    } catch (err) {
      setError(err instanceof ApiClientError ? err.message : "Receipt failed");
    } finally {
      setBusy(false);
    }
  }

  async function deleteDraft() {
    if (!confirm("Delete this draft PO? This can't be undone.")) return;
    setBusy(true);
    setError(null);
    try {
      await apiFetch(`/api/v1/purchase-orders/${po.id}`, { method: "DELETE" });
      router.push(`/admin/projects/${project.id}/purchase-orders`);
    } catch (err) {
      setError(err instanceof ApiClientError ? err.message : "Delete failed");
      setBusy(false);
    }
  }

  // Which state transitions are offered here — mirror of PO_TRANSITIONS in the API.
  const canSend = po.status === "draft";
  const canCancel = po.status !== "received" && po.status !== "cancelled";
  const canReceive = po.status === "sent" || po.status === "partial";
  const canDeleteDraft = po.status === "draft";

  return (
    <div className="mx-auto max-w-5xl px-4 py-8">
      <nav className="mb-3 text-sm text-slate-500">
        <Link href="/admin/projects" className="hover:underline">
          Projects
        </Link>
        <span className="mx-1">›</span>
        <Link href={`/admin/projects/${project.id}`} className="hover:underline">
          {project.code}
        </Link>
        <span className="mx-1">›</span>
        <Link
          href={`/admin/projects/${project.id}/purchase-orders`}
          className="hover:underline"
        >
          POs
        </Link>
        <span className="mx-1">›</span>
        <span className="font-mono text-xs">{po.id.slice(0, 8)}</span>
      </nav>

      <PageHeader
        title={
          <span className="flex items-center gap-3">
            <span>{po.vendor}</span>
            <Badge tone={STATUS_TONE[po.status] ?? "slate"}>{po.status}</Badge>
          </span>
        }
        description={
          <span className="flex flex-wrap items-center gap-2 text-slate-500">
            <span>PO {po.id.slice(0, 8).toUpperCase()}</span>
            <span className="text-slate-400">·</span>
            <span>Created {formatDate(po.createdAt)}</span>
            <span className="text-slate-400">·</span>
            <span>Sent {formatDate(po.sentAt)}</span>
            <span className="text-slate-400">·</span>
            <span>Received {formatDate(po.receivedAt)}</span>
          </span>
        }
        actions={
          <div className="flex flex-wrap items-center gap-2">
            <a
              href={`/api/v1/purchase-orders/${po.id}/pdf`}
              target="_blank"
              rel="noopener"
              className="inline-flex items-center rounded-md bg-white border border-slate-300 text-slate-900 text-sm px-3 py-1.5 hover:border-slate-900"
            >
              Download PDF
            </a>
            {canSend ? (
              <Button onClick={() => changeStatus("sent")} disabled={busy}>
                Mark sent
              </Button>
            ) : null}
            {canCancel ? (
              <Button variant="secondary" onClick={() => changeStatus("cancelled")} disabled={busy}>
                Cancel PO
              </Button>
            ) : null}
            {canDeleteDraft ? (
              <Button variant="danger" size="sm" onClick={deleteDraft} disabled={busy}>
                Delete draft
              </Button>
            ) : null}
          </div>
        }
      />

      {po.notes ? (
        <Card className="mb-4">
          <div className="p-4 text-sm text-slate-700 whitespace-pre-wrap">{po.notes}</div>
        </Card>
      ) : null}

      <ErrorBanner message={error} />

      <Card>
        <table className="w-full text-sm">
          <thead className="bg-slate-50 text-left text-slate-600 border-b border-slate-200">
            <tr>
              <th className="px-4 py-2 font-medium">Part #</th>
              <th className="px-4 py-2 font-medium">Description</th>
              <th className="px-4 py-2 font-medium text-right">Qty</th>
              <th className="px-4 py-2 font-medium text-right">Received</th>
              <th className="px-4 py-2 font-medium text-right">Unit</th>
              <th className="px-4 py-2 font-medium text-right">Line total</th>
              {canReceive ? (
                <th className="px-4 py-2 font-medium text-right">Receive +</th>
              ) : null}
            </tr>
          </thead>
          <tbody>
            {lines.map((l) => {
              const effectiveCost = l.unitCost ?? l.fastener.unitCost ?? null;
              const lineTotal = effectiveCost !== null ? effectiveCost * l.qty : null;
              const remaining = l.qty - l.receivedQty;
              const full = remaining === 0;
              return (
                <tr key={l.id} className="border-b border-slate-100 last:border-0">
                  <td className="px-4 py-3 font-mono text-slate-700">
                    {l.fastener.partNumber}
                  </td>
                  <td className="px-4 py-3">
                    <div className="font-medium">{l.fastener.description}</div>
                    {l.fastener.supplier ? (
                      <div className="text-xs text-slate-500">{l.fastener.supplier}</div>
                    ) : null}
                  </td>
                  <td className="px-4 py-3 text-right tabular-nums">{l.qty}</td>
                  <td className="px-4 py-3 text-right tabular-nums">
                    {l.receivedQty}
                    {full && l.receivedQty > 0 ? (
                      <Badge tone="green" className="ml-1">
                        full
                      </Badge>
                    ) : null}
                  </td>
                  <td className="px-4 py-3 text-right tabular-nums">
                    {effectiveCost !== null ? effectiveCost.toFixed(2) : "—"}
                  </td>
                  <td className="px-4 py-3 text-right tabular-nums">
                    {lineTotal !== null ? lineTotal.toFixed(2) : "—"}
                  </td>
                  {canReceive ? (
                    <td className="px-4 py-3 text-right">
                      <Input
                        type="number"
                        min={0}
                        max={remaining}
                        value={receipts[l.id] ?? ""}
                        onChange={(e) =>
                          setReceipts((prev) => ({ ...prev, [l.id]: e.target.value }))
                        }
                        placeholder={remaining.toString()}
                        className="w-20 text-right"
                        disabled={full || busy}
                      />
                    </td>
                  ) : null}
                </tr>
              );
            })}
          </tbody>
          <tfoot className="bg-slate-50 border-t border-slate-200">
            <tr>
              <td className="px-4 py-3" colSpan={2}>
                <span className="text-slate-500 text-xs uppercase tracking-wide">Totals</span>
              </td>
              <td className="px-4 py-3 text-right tabular-nums font-medium">{totalQty}</td>
              <td className="px-4 py-3 text-right tabular-nums font-medium">{totalReceived}</td>
              <td></td>
              <td className="px-4 py-3 text-right tabular-nums font-medium">
                {total > 0 ? total.toFixed(2) : "—"}
              </td>
              {canReceive ? <td></td> : null}
            </tr>
          </tfoot>
        </table>
      </Card>

      {canReceive ? (
        <div className="mt-4 flex justify-end">
          <Button onClick={submitReceipts} disabled={busy}>
            Record receipts
          </Button>
        </div>
      ) : null}
    </div>
  );
}