"use client";

import { useActionState, useEffect, useRef, useState, useTransition } from "react";
import { useRouter } from "next/navigation";
import { Button } from "@/components/ui/button";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import { Card, CardContent, CardFooter, CardHeader, CardTitle } from "@/components/ui/card";
import { Select } from "@/components/ui/select";
import { Combobox } from "@/components/ui/combobox";
import { createDeliveryNote, updateDeliveryNote, type ActionResult } from "@/actions/delivery-notes";
import { toast } from "sonner";
import type { Customer, DeliveryNote } from "@/lib/types";
import { DELIVERY_STATUSES, TANK_OPTIONS } from "@/lib/types";
import { RefreshCw } from "lucide-react";

const initial: ActionResult = { ok: false, error: "" };

interface Props {
  customers: Customer[];
  note?: DeliveryNote;
  customerName?: string;
  preselectedCustomerId?: string;
}

function todayISO() {
  return new Date().toISOString().slice(0, 10);
}

export function DeliveryNoteForm({ customers, note, customerName, preselectedCustomerId }: Props) {
  const router = useRouter();
  const isEdit = !!note;
  const boundAction = isEdit ? updateDeliveryNote.bind(null, note!.id) : createDeliveryNote;
  const [state, formAction, pending] = useActionState(boundAction, initial);
  const formRef = useRef<HTMLFormElement>(null);
  const [number, setNumber] = useState(note?.number || "");
  const [date, setDate] = useState((note?.date || "").slice(0, 10) || todayISO());
  const [customerId, setCustomerId] = useState(note?.customer || preselectedCustomerId || "");
  const [qty, setQty] = useState<number | "">(note?.qty_litres_supplied ?? "");
  const [price, setPrice] = useState<number | "">(note?.price_per_litre ?? "");
  const [total, setTotal] = useState<number | "">(note?.total_value ?? "");
  const [source, setSource] = useState<string>(note?.pricing_source || "");
  const [autoFilled, setAutoFilled] = useState(false);
  const [tank, setTank] = useState<string>(note?.plant_dispensing || "Plant 1");
  const [, startTransition] = useTransition();

  // Auto-fill price when customer/date change
  useEffect(() => {
    if (isEdit) return;
    if (!customerId || !date) return;
    startTransition(async () => {
      try {
        const res = await fetch(`/api/delivery-notes/price?customer=${customerId}&date=${date}`);
        if (res.ok) {
          const data = await res.json();
          if (data.price) {
            setPrice(data.price);
            setSource(data.source || "");
            setAutoFilled(true);
            if (qty) setTotal(Number((data.price * Number(qty)).toFixed(2)));
          }
        }
      } catch {}
    });
  }, [customerId, date, isEdit, qty]);

  // Recompute total on qty/price change
  useEffect(() => {
    if (qty && price) {
      setTotal(Number((Number(qty) * Number(price)).toFixed(2)));
    }
  }, [qty, price]);

  // Auto-suggest next note number — called by the "Auto-Number" button, not on mount.
  function autoNumber() {
    if (isEdit) return;
    startTransition(async () => {
      try {
        const res = await fetch("/api/delivery-notes/next-number");
        if (res.ok) {
          const data = await res.json();
          if (data.number) setNumber(data.number);
        }
      } catch {}
    });
  }

  useEffect(() => {
    if (state.ok) {
      toast.success(isEdit ? "Delivery note updated" : "Delivery note created");
      if (!isEdit) {
        router.push("/delivery-notes");
      } else {
        router.push(`/delivery-notes/${note!.id}`);
      }
    } else if (state.error) {
      toast.error(state.error);
    }
  }, [state, isEdit, router, note]);

  const customerItems = customers.map((c) => ({
    value: c.id,
    label: c.name,
    hint: c.email || c.contact_number || undefined,
  }));

  return (
    <Card className="max-w-3xl">
      <CardHeader>
        <CardTitle>{isEdit ? `Edit ${note!.number}` : "Add delivery note"}</CardTitle>
      </CardHeader>
      <form ref={formRef} action={formAction}>
        <CardContent className="space-y-4">
          <div className="grid gap-4 sm:grid-cols-2">
            <div className="space-y-2">
              <Label htmlFor="number">Delivery note # *</Label>
              <div className="flex gap-2">
                <Input
                  id="number"
                  name="number"
                  value={number}
                  onChange={(e) => setNumber(e.target.value)}
                  required
                  placeholder="e.g. 0001"
                  className="font-mono"
                />
                {!isEdit && (
                  <Button
                    type="button"
                    variant="outline"
                    onClick={autoNumber}
                    aria-label="Auto-Number"
                    title="Suggest next number from the highest existing"
                  >
                    <RefreshCw className="h-4 w-4" />
                    Auto-Number
                  </Button>
                )}
              </div>
            </div>
            <div className="space-y-2">
              <Label htmlFor="date">Delivery date *</Label>
              <Input
                id="date"
                name="date"
                type="date"
                value={date}
                onChange={(e) => setDate(e.target.value)}
                max={todayISO()}
                required
              />
            </div>
          </div>
          <div className="space-y-2">
            <Label htmlFor="customer">Customer *</Label>
            <Combobox
              id="customer"
              name="customer"
              items={customerItems}
              value={customerId}
              onChange={setCustomerId}
              placeholder="Search customers…"
              emptyMessage={customers.length === 0 ? "No customers — add one first." : "No matches."}
              required
            />
          </div>
          <div className="grid gap-4 sm:grid-cols-2">
            <div className="space-y-2">
              <Label htmlFor="plant_dispensing">Plant / Dispensing</Label>
              <Select
                id="plant_dispensing"
                name="plant_dispensing"
                value={tank}
                onChange={(e) => setTank(e.target.value)}
                options={[
                  { value: "Plant 1", label: "Plant 1" },
                  ...TANK_OPTIONS.map((t) => ({ value: t, label: t })),
                ]}
              />
            </div>
            <div className="space-y-2">
              <Label htmlFor="vehicle_registration">Vehicle registration</Label>
              <Input
                id="vehicle_registration"
                name="vehicle_registration"
                defaultValue={note?.vehicle_registration || ""}
                placeholder="e.g. ABC 123 GP"
              />
            </div>
          </div>
          <div className="grid gap-4 sm:grid-cols-3">
            <div className="space-y-2">
              <Label htmlFor="qty_litres_supplied">Qty (litres) *</Label>
              <Input
                id="qty_litres_supplied"
                name="qty_litres_supplied"
                type="number"
                step="0.01"
                min="0.01"
                value={qty}
                onChange={(e) => setQty(e.target.value === "" ? "" : Number(e.target.value))}
                required
              />
            </div>
            <div className="space-y-2">
              <Label htmlFor="price_per_litre">Price / L</Label>
              <Input
                id="price_per_litre"
                name="price_per_litre"
                type="number"
                step="0.01"
                min="0"
                value={price}
                onChange={(e) => {
                  setPrice(e.target.value === "" ? "" : Number(e.target.value));
                  setAutoFilled(false);
                }}
              />
              {autoFilled && source && (
                <p className="text-xs text-muted-foreground">auto-filled from {source} pricing</p>
              )}
              <input type="hidden" name="pricing_source" value={source} />
            </div>
            <div className="space-y-2">
              <Label htmlFor="total_value">Total value</Label>
              <Input
                id="total_value"
                name="total_value"
                type="number"
                step="0.01"
                min="0"
                value={total}
                onChange={(e) => setTotal(e.target.value === "" ? "" : Number(e.target.value))}
              />
            </div>
          </div>
          <div className="space-y-2">
            <Label htmlFor="status">Status</Label>
            <Select
              id="status"
              name="status"
              defaultValue={note?.status || "Pending"}
              options={DELIVERY_STATUSES.map((s) => ({ value: s, label: s }))}
            />
          </div>
        </CardContent>
        <CardFooter className="flex justify-between">
          <Button type="button" variant="ghost" onClick={() => router.back()}>
            Cancel
          </Button>
          <Button type="submit" disabled={pending}>
            {pending ? "Saving…" : isEdit ? "Update note" : "Create note"}
          </Button>
        </CardFooter>
      </form>
    </Card>
  );
}