"use client";

import { useState, useEffect } from "react";
import { useParams, useRouter } from "next/navigation";
import useSWR from "swr";
import {
  Card,
  CardContent,
  CardHeader,
  CardTitle,
} from "@/components/ui/card";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import { Badge } from "@/components/ui/badge";
import { Textarea } from "@/components/ui/textarea";
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from "@/components/ui/select";
import {
  Table,
  TableBody,
  TableCell,
  TableHead,
  TableHeader,
  TableRow,
} from "@/components/ui/table";
import { Progress } from "@/components/ui/progress";
import { ArrowLeft, Plus, Trash2, Package, Save, Euro, Layers, Truck, FileDown } from "lucide-react";
import { toast } from "sonner";
import { formatCurrency } from "@/lib/format";
import type { Product, PurchaseOrder, PurchaseOrderItem } from "@/lib/types";

const fetcher = (url: string) => fetch(url).then((r) => r.json());

interface OrderLineItem {
  product_id: string;
  quantity: string;
  unit_price: string;
  notes: string;
}

const statusConfig: Record<string, { label: string; variant: "default" | "secondary" | "destructive" | "outline" }> = {
  draft: { label: "Draft", variant: "secondary" },
  confirmed: { label: "Confirmed", variant: "default" },
  in_production: { label: "In Production", variant: "outline" },
  shipped: { label: "Shipped", variant: "default" },
  completed: { label: "Completed", variant: "default" },
  cancelled: { label: "Cancelled", variant: "destructive" },
};

export default function OrderDetailPage() {
  const params = useParams();
  const router = useRouter();
  const customerId = params.id as string;
  const orderId = params.orderId as string;

  const [loading, setLoading] = useState(false);
  const [editing, setEditing] = useState(false);

  const [form, setForm] = useState({
    po_number: "",
    customer_ref: "",
    status: "draft",
    order_date: "",
    due_date: "",
    notes: "",
  });

  const [items, setItems] = useState<OrderLineItem[]>([]);

  const { data: orderData, mutate } = useSWR<
    PurchaseOrder & { items: PurchaseOrderItem[] }
  >(`/api/orders/${orderId}`, fetcher);

  const { data: products = [] } = useSWR<Product[]>("/api/products", fetcher);

  useEffect(() => {
    if (orderData) {
      setForm({
        po_number: orderData.po_number || "",
        customer_ref: orderData.customer_ref || "",
        status: orderData.status || "draft",
        order_date: orderData.order_date
          ? new Date(orderData.order_date).toISOString().slice(0, 10)
          : "",
        due_date: orderData.due_date
          ? new Date(orderData.due_date).toISOString().slice(0, 10)
          : "",
        notes: orderData.notes || "",
      });
      setItems(
        (orderData.items || []).map((item) => ({
          product_id: String(item.product_id),
          quantity: String(item.quantity),
          unit_price: String(item.unit_price),
          notes: item.notes || "",
        }))
      );
    }
  }, [orderData]);

  function addLine() {
    setItems([
      ...items,
      { product_id: "", quantity: "1", unit_price: "", notes: "" },
    ]);
  }

  function removeLine(index: number) {
    if (items.length <= 1) return;
    setItems(items.filter((_, i) => i !== index));
  }

  function updateLine(index: number, field: keyof OrderLineItem, value: string) {
    const updated = [...items];
    updated[index] = { ...updated[index], [field]: value };
    setItems(updated);
  }

  function getLineTotal(item: OrderLineItem) {
    return (Number(item.quantity) || 0) * (Number(item.unit_price) || 0);
  }

  const orderTotal = items.reduce((sum, item) => sum + getLineTotal(item), 0);

  async function handleDownloadPO() {
    if (!orderData) return;
    const { generatePoPdf } = await import("@/lib/generate-po-pdf");
    const doc = generatePoPdf({
      po_number: orderData.po_number,
      order_date: orderData.order_date,
      due_date: orderData.due_date,
      customer_ref: orderData.customer_ref,
      status: orderData.status,
      customer_name: orderData.customer_name || "",
      customer_code: orderData.customer_code || "",
      customer_email: (orderData as Record<string, unknown>).customer_email as string | null,
      customer_phone: (orderData as Record<string, unknown>).customer_phone as string | null,
      customer_address: (orderData as Record<string, unknown>).customer_address as string | null,
      customer_contact: (orderData as Record<string, unknown>).customer_contact as string | null,
      notes: orderData.notes,
      items: (orderData.items || []).map((item) => ({
        product_name: item.product_name || "",
        product_sku: item.product_sku || "",
        quantity: Number(item.quantity),
        unit_price: Number(item.unit_price),
        line_total: Number(item.line_total || 0),
        notes: item.notes,
      })),
    });
    doc.save(`${orderData.po_number}.pdf`);
  }

  async function handleSave() {
    setLoading(true);
    try {
      const validItems = items.filter((item) => item.product_id);
      const res = await fetch(`/api/orders/${orderId}`, {
        method: "PUT",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          customer_id: Number(customerId),
          ...form,
          due_date: form.due_date || null,
          items: validItems.map((item) => ({
            product_id: Number(item.product_id),
            quantity: Number(item.quantity) || 1,
            unit_price: Number(item.unit_price) || 0,
            notes: item.notes || null,
          })),
        }),
      });

      if (!res.ok) throw new Error("Failed to update");
      toast.success("Purchase order updated");
      mutate();
      setEditing(false);
    } catch {
      toast.error("Failed to update order");
    } finally {
      setLoading(false);
    }
  }

  if (!orderData) {
    return (
      <div className="flex items-center justify-center p-12">
        <p className="text-muted-foreground">Loading order...</p>
      </div>
    );
  }

  const sc = statusConfig[orderData.status] || statusConfig.draft;

  // VIEW MODE
  if (!editing) {
    return (
      <div className="flex flex-col gap-6 p-6">
        <div className="flex items-start justify-between">
          <div className="flex items-center gap-4">
            <Button
              variant="ghost"
              size="icon"
              onClick={() => router.push(`/customers/${customerId}`)}
            >
              <ArrowLeft className="h-4 w-4" />
            </Button>
            <div>
              <div className="flex items-center gap-3">
                <h1 className="text-2xl font-bold tracking-tight font-mono text-foreground">
                  {orderData.po_number}
                </h1>
                <Badge variant={sc.variant}>{sc.label}</Badge>
              </div>
              <p className="text-sm text-muted-foreground">
                Order for {orderData.customer_name} ({orderData.customer_code})
              </p>
            </div>
          </div>
          <div className="flex items-center gap-2">
            <Button variant="outline" size="sm" onClick={handleDownloadPO}>
              <FileDown className="mr-2 h-3.5 w-3.5" />
              Download PO
            </Button>
            <Button variant="outline" size="sm" onClick={() => setEditing(true)}>
              Edit Order
            </Button>
          </div>
        </div>

        {/* Summary Cards */}
        {(() => {
          const itemsList = orderData.items || [];
          const totalOrdered = itemsList.reduce((s, i) => s + Number(i.quantity), 0);
          const totalShipped = itemsList.reduce((s, i) => s + Number(i.shipped_quantity || 0), 0);
          const totalRemaining = totalOrdered - totalShipped;
          const fulfillmentPct = totalOrdered > 0 ? Math.round((totalShipped / totalOrdered) * 100) : 0;
          const isOverdue = orderData.due_date && new Date(orderData.due_date) < new Date() && fulfillmentPct < 100;

          return (
            <div className="grid grid-cols-1 gap-4 md:grid-cols-5">
              <Card>
                <CardHeader className="flex flex-row items-center justify-between pb-2">
                  <CardTitle className="text-sm font-medium text-muted-foreground">
                    Order Date
                  </CardTitle>
                </CardHeader>
                <CardContent>
                  <p className="text-lg font-semibold">
                    {new Date(orderData.order_date).toLocaleDateString()}
                  </p>
                </CardContent>
              </Card>
              <Card>
                <CardHeader className="flex flex-row items-center justify-between pb-2">
                  <CardTitle className="text-sm font-medium text-muted-foreground">
                    Due Date
                  </CardTitle>
                </CardHeader>
                <CardContent>
                  <p className={`text-lg font-semibold ${isOverdue ? "text-destructive" : ""}`}>
                    {orderData.due_date
                      ? new Date(orderData.due_date).toLocaleDateString()
                      : "Not set"}
                    {isOverdue && (
                      <span className="ml-1 text-xs font-normal">(overdue)</span>
                    )}
                  </p>
                </CardContent>
              </Card>
              <Card>
                <CardHeader className="flex flex-row items-center justify-between pb-2">
                  <CardTitle className="text-sm font-medium text-muted-foreground">
                    Order Total
                  </CardTitle>
                  <Euro className="h-4 w-4 text-accent" />
                </CardHeader>
                <CardContent>
                  <p className="text-2xl font-bold">
                    {formatCurrency(
                      itemsList.reduce((s, i) => s + Number(i.line_total || 0), 0)
                    )}
                  </p>
                  <p className="text-xs text-muted-foreground">
                    {itemsList.length} line item{itemsList.length !== 1 ? "s" : ""}
                  </p>
                </CardContent>
              </Card>
              <Card>
                <CardHeader className="flex flex-row items-center justify-between pb-2">
                  <CardTitle className="text-sm font-medium text-muted-foreground">
                    Units Remaining
                  </CardTitle>
                  <Package className="h-4 w-4 text-primary" />
                </CardHeader>
                <CardContent>
                  <p className="text-2xl font-bold font-mono">
                    <span className={totalRemaining > 0 ? "text-foreground" : "text-accent"}>
                      {totalRemaining}
                    </span>
                    <span className="text-sm font-normal text-muted-foreground ml-1">
                      / {totalOrdered}
                    </span>
                  </p>
                  <p className="text-xs text-muted-foreground">
                    {totalShipped} shipped
                  </p>
                </CardContent>
              </Card>
              <Card>
                <CardHeader className="flex flex-row items-center justify-between pb-2">
                  <CardTitle className="text-sm font-medium text-muted-foreground">
                    Fulfillment
                  </CardTitle>
                  <Truck className="h-4 w-4 text-primary" />
                </CardHeader>
                <CardContent>
                  <p className={`text-2xl font-bold font-mono ${fulfillmentPct === 100 ? "text-accent" : ""}`}>
                    {fulfillmentPct}%
                  </p>
                  <Progress value={fulfillmentPct} className="mt-2 h-2" />
                </CardContent>
              </Card>
            </div>
          );
        })()}

        {orderData.customer_ref && (
          <div className="text-sm text-muted-foreground">
            Customer Reference:{" "}
            <span className="font-mono font-medium text-foreground">
              {orderData.customer_ref}
            </span>
          </div>
        )}

        {orderData.notes && (
          <Card>
            <CardContent className="p-4 text-sm text-muted-foreground">
              {orderData.notes}
            </CardContent>
          </Card>
        )}

        {/* Line Items Table */}
        <Card>
          <CardHeader>
            <CardTitle className="flex items-center gap-2 text-base">
              <Package className="h-4 w-4 text-primary" />
              Order Items
            </CardTitle>
          </CardHeader>
          <CardContent className="p-0">
            <Table>
              <TableHeader>
                <TableRow>
                  <TableHead>#</TableHead>
                  <TableHead>Product</TableHead>
                  <TableHead>SKU</TableHead>
                  <TableHead className="text-right">Ordered</TableHead>
                  <TableHead className="text-right">Shipped</TableHead>
                  <TableHead className="text-right">Remaining</TableHead>
                  <TableHead className="w-[120px]">Fulfillment</TableHead>
                  <TableHead className="text-right">Unit Price</TableHead>
                  <TableHead className="text-right">Line Total</TableHead>
                  <TableHead>Notes</TableHead>
                </TableRow>
              </TableHeader>
              <TableBody>
                {(orderData.items || []).map(
                  (item: PurchaseOrderItem, idx: number) => {
                    const ordered = Number(item.quantity);
                    const shipped = Number(item.shipped_quantity || 0);
                    const remaining = ordered - shipped;
                    const pct = ordered > 0 ? Math.round((shipped / ordered) * 100) : 0;

                    return (
                      <TableRow key={item.id}>
                        <TableCell className="text-xs text-muted-foreground">
                          {idx + 1}
                        </TableCell>
                        <TableCell className="font-medium">
                          {item.product_name}
                        </TableCell>
                        <TableCell className="font-mono text-xs text-muted-foreground">
                          {item.product_sku}
                        </TableCell>
                        <TableCell className="text-right font-mono">
                          {ordered.toLocaleString()}
                        </TableCell>
                        <TableCell className="text-right font-mono">
                          {shipped.toLocaleString()}
                        </TableCell>
                        <TableCell className="text-right font-mono font-semibold">
                          <span className={remaining > 0 ? "text-foreground" : "text-accent"}>
                            {remaining.toLocaleString()}
                          </span>
                        </TableCell>
                        <TableCell>
                          <div className="flex flex-col gap-1">
                            <div className="flex items-center justify-between text-xs">
                              <span className="font-mono text-muted-foreground">
                                {shipped}/{ordered}
                              </span>
                              <span className={pct === 100 ? "font-semibold text-accent" : "text-muted-foreground"}>
                                {pct}%
                              </span>
                            </div>
                            <Progress value={pct} className="h-1.5" />
                          </div>
                        </TableCell>
                        <TableCell className="text-right font-mono">
                          {formatCurrency(Number(item.unit_price))}
                        </TableCell>
                        <TableCell className="text-right font-mono font-semibold">
                          {formatCurrency(Number(item.line_total || 0))}
                        </TableCell>
                        <TableCell className="text-xs text-muted-foreground">
                          {item.notes || "-"}
                        </TableCell>
                      </TableRow>
                    );
                  }
                )}
              </TableBody>
            </Table>
          </CardContent>
        </Card>
      </div>
    );
  }

  // EDIT MODE
  return (
    <div className="flex flex-col gap-6 p-6">
      <div className="flex items-center gap-4">
        <Button
          variant="ghost"
          size="icon"
          onClick={() => setEditing(false)}
        >
          <ArrowLeft className="h-4 w-4" />
        </Button>
        <div>
          <h1 className="text-2xl font-bold tracking-tight text-foreground">
            Edit Purchase Order
          </h1>
          <p className="text-sm text-muted-foreground">
            {orderData.po_number} - {orderData.customer_name}
          </p>
        </div>
      </div>

      <Card>
        <CardHeader>
          <CardTitle className="text-base">Order Details</CardTitle>
        </CardHeader>
        <CardContent className="flex flex-col gap-4">
          <div className="grid grid-cols-1 gap-4 md:grid-cols-3">
            <div className="flex flex-col gap-2">
              <Label htmlFor="po_number">PO Number</Label>
              <Input
                id="po_number"
                value={form.po_number}
                onChange={(e) =>
                  setForm({ ...form, po_number: e.target.value })
                }
                className="font-mono"
              />
            </div>
            <div className="flex flex-col gap-2">
              <Label htmlFor="customer_ref">Customer Reference</Label>
              <Input
                id="customer_ref"
                value={form.customer_ref}
                onChange={(e) =>
                  setForm({ ...form, customer_ref: e.target.value })
                }
              />
            </div>
            <div className="flex flex-col gap-2">
              <Label htmlFor="status">Status</Label>
              <Select
                value={form.status}
                onValueChange={(v) => setForm({ ...form, status: v })}
              >
                <SelectTrigger id="status">
                  <SelectValue />
                </SelectTrigger>
                <SelectContent>
                  <SelectItem value="draft">Draft</SelectItem>
                  <SelectItem value="confirmed">Confirmed</SelectItem>
                  <SelectItem value="in_production">In Production</SelectItem>
                  <SelectItem value="shipped">Shipped</SelectItem>
                  <SelectItem value="completed">Completed</SelectItem>
                  <SelectItem value="cancelled">Cancelled</SelectItem>
                </SelectContent>
              </Select>
            </div>
          </div>
          <div className="grid grid-cols-1 gap-4 md:grid-cols-3">
            <div className="flex flex-col gap-2">
              <Label htmlFor="order_date">Order Date</Label>
              <Input
                id="order_date"
                type="date"
                value={form.order_date}
                onChange={(e) =>
                  setForm({ ...form, order_date: e.target.value })
                }
              />
            </div>
            <div className="flex flex-col gap-2">
              <Label htmlFor="due_date">Due Date</Label>
              <Input
                id="due_date"
                type="date"
                value={form.due_date}
                onChange={(e) =>
                  setForm({ ...form, due_date: e.target.value })
                }
              />
            </div>
          </div>
          <div className="flex flex-col gap-2">
            <Label htmlFor="notes">Notes</Label>
            <Textarea
              id="notes"
              value={form.notes}
              onChange={(e) => setForm({ ...form, notes: e.target.value })}
              rows={2}
            />
          </div>
        </CardContent>
      </Card>

      {/* Line Items */}
      <Card>
        <CardHeader className="flex flex-row items-center justify-between">
          <CardTitle className="flex items-center gap-2 text-base">
            <Package className="h-4 w-4 text-primary" />
            Line Items
          </CardTitle>
          <Button type="button" variant="outline" size="sm" onClick={addLine}>
            <Plus className="mr-2 h-3.5 w-3.5" />
            Add Line
          </Button>
        </CardHeader>
        <CardContent className="p-0">
          <div className="overflow-x-auto">
            <Table>
              <TableHeader>
                <TableRow>
                  <TableHead className="w-[40px]">#</TableHead>
                  <TableHead>Product</TableHead>
                  <TableHead className="w-[120px]">Quantity</TableHead>
                  <TableHead className="w-[140px]">Unit Price</TableHead>
                  <TableHead className="w-[140px] text-right">
                    Line Total
                  </TableHead>
                  <TableHead>Notes</TableHead>
                  <TableHead className="w-[50px]" />
                </TableRow>
              </TableHeader>
              <TableBody>
                {items.map((item, index) => (
                  <TableRow key={index}>
                    <TableCell className="text-center text-xs text-muted-foreground">
                      {index + 1}
                    </TableCell>
                    <TableCell>
                      <Select
                        value={item.product_id}
                        onValueChange={(v) =>
                          updateLine(index, "product_id", v)
                        }
                      >
                        <SelectTrigger className="h-9">
                          <SelectValue placeholder="Select product..." />
                        </SelectTrigger>
                        <SelectContent>
                          {products.map((p) => (
                            <SelectItem key={p.id} value={String(p.id)}>
                              <span className="font-mono text-xs text-muted-foreground mr-2">
                                {p.sku}
                              </span>
                              {p.name}
                            </SelectItem>
                          ))}
                        </SelectContent>
                      </Select>
                    </TableCell>
                    <TableCell>
                      <Input
                        type="number"
                        min="1"
                        value={item.quantity}
                        onChange={(e) =>
                          updateLine(index, "quantity", e.target.value)
                        }
                        className="h-9 font-mono"
                      />
                    </TableCell>
                    <TableCell>
                      <div className="relative">
                        <span className="absolute left-3 top-1/2 -translate-y-1/2 text-xs text-muted-foreground">
                          {'€'}
                        </span>
                        <Input
                          type="number"
                          step="0.01"
                          min="0"
                          value={item.unit_price}
                          onChange={(e) =>
                            updateLine(index, "unit_price", e.target.value)
                          }
                          className="h-9 pl-7 font-mono"
                        />
                      </div>
                    </TableCell>
                    <TableCell className="text-right font-mono text-sm font-semibold">
                      {formatCurrency(getLineTotal(item))}
                    </TableCell>
                    <TableCell>
                      <Input
                        value={item.notes}
                        onChange={(e) =>
                          updateLine(index, "notes", e.target.value)
                        }
                        placeholder="Optional"
                        className="h-9 text-xs"
                      />
                    </TableCell>
                    <TableCell>
                      <Button
                        type="button"
                        variant="ghost"
                        size="icon"
                        className="h-8 w-8 text-destructive hover:text-destructive"
                        onClick={() => removeLine(index)}
                        disabled={items.length <= 1}
                      >
                        <Trash2 className="h-3.5 w-3.5" />
                      </Button>
                    </TableCell>
                  </TableRow>
                ))}
                <TableRow className="bg-muted/50">
                  <TableCell colSpan={4} className="text-right font-semibold">
                    Order Total
                  </TableCell>
                  <TableCell className="text-right font-mono text-base font-bold text-primary">
                    {formatCurrency(orderTotal)}
                  </TableCell>
                  <TableCell colSpan={2} />
                </TableRow>
              </TableBody>
            </Table>
          </div>
        </CardContent>
      </Card>

      <div className="flex justify-end gap-3">
        <Button variant="outline" onClick={() => setEditing(false)}>
          Cancel
        </Button>
        <Button onClick={handleSave} disabled={loading}>
          <Save className="mr-2 h-4 w-4" />
          {loading ? "Saving..." : "Save Changes"}
        </Button>
      </div>
    </div>
  );
}