import { createFileRoute, useNavigate, useSearch } from "@tanstack/react-router";
import { useEffect, useState } from "react";
import { ProtectedLayout } from "@/components/protected-layout";
import { PageContainer, PageHeader } from "@/components/app-shell";
import { Card, CardContent } from "@/components/ui/card";
import { Button } from "@/components/ui/button";
import { Checkbox } from "@/components/ui/checkbox";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import { Textarea } from "@/components/ui/textarea";
import { supabase } from "@/integrations/supabase/client";
import { useAuth } from "@/lib/auth";
import { Loader2, FilePlus, ArrowLeft } from "lucide-react";
import { formatCurrency } from "@/lib/format";
import { toast } from "sonner";
import { generateInvoiceForClient } from "@/lib/invoice-generation";

interface SearchParams {
  caseId?: string;
}

export const Route = createFileRoute("/invoices/new/$clientId")({
  validateSearch: (search: Record<string, unknown>): SearchParams => ({
    caseId: typeof search.caseId === "string" ? search.caseId : undefined,
  }),
  component: () => (
    <ProtectedLayout>
      <NewInvoicePage />
    </ProtectedLayout>
  ),
});

interface CaseUnbilled {
  id: string;
  case_number: string;
  title: string;
  timeCount: number;
  timeAmount: number;
  expenseCount: number;
  expenseAmount: number;
  total: number;
}

function NewInvoicePage() {
  const { clientId } = Route.useParams();
  const { caseId: presetCaseId } = useSearch({ from: "/invoices/new/$clientId" });
  const { user } = useAuth();
  const navigate = useNavigate();

  const [clientName, setClientName] = useState<string>("");
  const [cases, setCases] = useState<CaseUnbilled[]>([]);
  const [selected, setSelected] = useState<Record<string, boolean>>({});
  const [taxPct, setTaxPct] = useState("0");
  const [dueDays, setDueDays] = useState("30");
  const [notes, setNotes] = useState("");
  const [retainerAmount, setRetainerAmount] = useState("");
  const [isRetainer, setIsRetainer] = useState(false);
  const [splitPerCase, setSplitPerCase] = useState(false);
  const [loading, setLoading] = useState(true);
  const [saving, setSaving] = useState(false);

  useEffect(() => {
    (async () => {
      setLoading(true);
      const [{ data: client }, { data: cs }, { data: firm }] = await Promise.all([
        supabase.from("clients").select("name").eq("id", clientId).maybeSingle(),
        supabase.from("cases").select("id, case_number, title").eq("client_id", clientId).is("archived_at", null),
        supabase.from("firm_settings").select("default_tax_rate").maybeSingle(),
      ]);
      setClientName(client?.name ?? "");
      const caseIds = (cs ?? []).map((c) => c.id);
      if (firm?.default_tax_rate != null) setTaxPct(String(firm.default_tax_rate));
      if (caseIds.length === 0) {
        setCases([]); setLoading(false); return;
      }
      const [{ data: time }, { data: exp }] = await Promise.all([
        supabase.from("time_entries").select("case_id, hours, hourly_rate")
          .in("case_id", caseIds).eq("billable", true).is("invoice_id", null),
        supabase.from("expenses").select("case_id, amount")
          .in("case_id", caseIds).eq("billable", true).is("invoice_id", null),
      ]);
      const tally: Record<string, { tc: number; ta: number; ec: number; ea: number }> = {};
      for (const t of time ?? []) {
        const k = t.case_id;
        if (!tally[k]) tally[k] = { tc: 0, ta: 0, ec: 0, ea: 0 };
        tally[k].tc += 1;
        tally[k].ta += Number(t.hours) * Number(t.hourly_rate);
      }
      for (const e of exp ?? []) {
        const k = e.case_id;
        if (!tally[k]) tally[k] = { tc: 0, ta: 0, ec: 0, ea: 0 };
        tally[k].ec += 1;
        tally[k].ea += Number(e.amount);
      }
      const enriched: CaseUnbilled[] = (cs ?? []).map((c) => {
        const t = tally[c.id] ?? { tc: 0, ta: 0, ec: 0, ea: 0 };
        return {
          id: c.id, case_number: c.case_number, title: c.title,
          timeCount: t.tc, timeAmount: t.ta, expenseCount: t.ec, expenseAmount: t.ea,
          total: t.ta + t.ea,
        };
      }).filter((c) => c.total > 0);
      setCases(enriched);
      const sel: Record<string, boolean> = {};
      if (presetCaseId) {
        sel[presetCaseId] = true;
      } else {
        enriched.forEach((c) => { sel[c.id] = true; });
      }
      setSelected(sel);
      setLoading(false);
    })();
  }, [clientId, presetCaseId]);

  const selectedIds = Object.entries(selected).filter(([, v]) => v).map(([k]) => k);
  const subtotal = cases.filter((c) => selected[c.id]).reduce((s, c) => s + c.total, 0);
  const tax = +(subtotal * (Number(taxPct) || 0) / 100).toFixed(2);
  const total = subtotal + tax;

  const submit = async () => {
    if (!user?.id) return;
    if (selectedIds.length === 0 && !isRetainer) return toast.error("Select at least one case");
    setSaving(true);
    try {
      if (isRetainer) {
        const yr = new Date().getFullYear();
        const num = `INV-${yr}-${Math.floor(1000 + Math.random() * 9000)}`;
        const due = new Date();
        due.setDate(due.getDate() + (Number(dueDays) || 30));
        const amt = Math.max(0, Number(retainerAmount) || 0);
        if (amt <= 0) {
          setSaving(false);
          return toast.error("Enter a retainer amount");
        }
        const taxAmt = +(amt * (Number(taxPct) || 0) / 100).toFixed(2);
        const { data: inv, error: ie } = await supabase
          .from("invoices")
          .insert({
            invoice_number: num,
            client_id: clientId,
            status: "draft",
            issue_date: new Date().toISOString().slice(0, 10),
            due_date: due.toISOString().slice(0, 10),
            subtotal: amt,
            tax: taxAmt,
            total: +(amt + taxAmt).toFixed(2),
            notes: notes || "Retainer deposit",
            is_retainer: true,
            created_by: user.id,
          })
          .select("id, invoice_number")
          .single();
        if (ie || !inv) throw ie ?? new Error("Failed to create");
        await supabase.from("invoice_line_items").insert({
          invoice_id: inv.id,
          kind: "manual",
          description: "Retainer deposit into trust account",
          quantity: 1,
          rate: amt,
          amount: amt,
          sort_order: 0,
        });
        toast.success(`Retainer invoice ${inv.invoice_number} created`);
        navigate({ to: "/invoices/$invoiceId", params: { invoiceId: inv.id } });
        return;
      }
      if (splitPerCase && selectedIds.length > 1) {
        const results: { id: string; number: string }[] = [];
        for (const cid of selectedIds) {
          const r = await generateInvoiceForClient({
            clientId,
            caseIds: [cid],
            createdBy: user.id,
            taxRate: (Number(taxPct) || 0) / 100,
            dueDays: Number(dueDays) || 30,
            notes: notes || undefined,
          });
          results.push({ id: r.invoiceId, number: r.invoiceNumber });
        }
        toast.success(`${results.length} invoices created`);
        navigate({ to: "/invoices" });
        return;
      }
      const { invoiceId, invoiceNumber } = await generateInvoiceForClient({
        clientId,
        caseIds: selectedIds,
        createdBy: user.id,
        taxRate: (Number(taxPct) || 0) / 100,
        dueDays: Number(dueDays) || 30,
        notes: notes || undefined,
      });
      toast.success(`Invoice ${invoiceNumber} created`);
      navigate({ to: "/invoices/$invoiceId", params: { invoiceId } });
    } catch (e: any) {
      toast.error(e?.message || "Failed to generate");
    } finally {
      setSaving(false);
    }
  };

  return (
    <PageContainer>
      <PageHeader
        title={`Generate invoice${clientName ? ` — ${clientName}` : ""}`}
        description="Pick which cases to bill, set tax/due, and create a draft invoice."
        actions={
          <Button variant="outline" onClick={() => navigate({ to: "/invoices/new" })}>
            <ArrowLeft className="h-4 w-4 mr-2" /> Change client
          </Button>
        }
      />

      <div className="max-w-4xl space-y-4">
        <Card className="border-border/60">
          <CardContent className="p-4">
            <label className="flex items-start gap-3 cursor-pointer">
              <Checkbox
                checked={isRetainer}
                onCheckedChange={(v) => setIsRetainer(!!v)}
                className="mt-0.5"
              />
              <div className="flex-1">
                <div className="text-sm font-medium">Retainer / trust deposit invoice</div>
                <div className="text-xs text-muted-foreground">
                  When paid, the amount is automatically deposited into this client's trust account.
                </div>
              </div>
            </label>
          </CardContent>
        </Card>

        {isRetainer ? (
          <Card className="border-border/60">
            <CardContent className="p-4 grid grid-cols-1 sm:grid-cols-3 gap-3">
              <div>
                <Label>Retainer amount</Label>
                <Input
                  type="number"
                  step="0.01"
                  placeholder="0.00"
                  value={retainerAmount}
                  onChange={(e) => setRetainerAmount(e.target.value)}
                />
              </div>
              <div>
                <Label>Tax rate (%)</Label>
                <Input type="number" step="0.01" value={taxPct} onChange={(e) => setTaxPct(e.target.value)} />
              </div>
              <div>
                <Label>Due in (days)</Label>
                <Input type="number" value={dueDays} onChange={(e) => setDueDays(e.target.value)} />
              </div>
            </CardContent>
          </Card>
        ) : loading ? (
          <Card className="border-border/60">
            <CardContent className="py-12 text-center text-muted-foreground">Loading unbilled work…</CardContent>
          </Card>
        ) : cases.length === 0 ? (
          <Card className="border-border/60">
            <CardContent className="py-12 text-center text-muted-foreground text-sm">
              No unbilled time or expenses across this client's cases.
            </CardContent>
          </Card>
        ) : (
          <>
            <Card className="border-border/60">
              <CardContent className="p-4">
                <div className="flex items-center justify-between mb-3">
                  <Label className="text-xs uppercase tracking-wider text-muted-foreground">Cases to bill</Label>
                  <div className="flex items-center gap-2 text-xs">
                    <button
                      type="button"
                      className="text-primary hover:underline"
                      onClick={() => setSelected(Object.fromEntries(cases.map((c) => [c.id, true])))}
                    >
                      Select all
                    </button>
                    <span className="text-muted-foreground">·</span>
                    <button
                      type="button"
                      className="text-primary hover:underline"
                      onClick={() => setSelected({})}
                    >
                      Clear
                    </button>
                  </div>
                </div>
                <div className="border rounded-md divide-y">
                  {cases.map((c) => (
                    <label key={c.id} className="flex items-start gap-3 p-3 cursor-pointer hover:bg-muted/40">
                      <Checkbox
                        checked={!!selected[c.id]}
                        onCheckedChange={(v) => setSelected((p) => ({ ...p, [c.id]: !!v }))}
                        className="mt-0.5"
                      />
                      <div className="flex-1 min-w-0">
                        <div className="flex items-center justify-between gap-2">
                          <span className="font-medium text-sm truncate">{c.title}</span>
                          <span className="text-sm tabular-nums font-medium">{formatCurrency(c.total)}</span>
                        </div>
                        <div className="text-xs text-muted-foreground">
                          {c.case_number} · {c.timeCount} time entries ({formatCurrency(c.timeAmount)}) · {c.expenseCount} expenses ({formatCurrency(c.expenseAmount)})
                        </div>
                      </div>
                    </label>
                  ))}
                </div>
              </CardContent>
            </Card>

            {selectedIds.length > 1 && (
              <Card className="border-border/60">
                <CardContent className="p-4">
                  <label className="flex items-start gap-3 cursor-pointer">
                    <Checkbox
                      checked={splitPerCase}
                      onCheckedChange={(v) => setSplitPerCase(!!v)}
                      className="mt-0.5"
                    />
                    <div className="flex-1">
                      <div className="text-sm font-medium">Generate one invoice per selected case</div>
                      <div className="text-xs text-muted-foreground">
                        Creates {selectedIds.length} separate draft invoices instead of one combined invoice.
                      </div>
                    </div>
                  </label>
                </CardContent>
              </Card>
            )}

            <Card className="border-border/60">
              <CardContent className="p-4 grid grid-cols-1 sm:grid-cols-3 gap-3 items-end">
                <div>
                  <Label>Tax rate (%)</Label>
                  <Input type="number" step="0.01" value={taxPct} onChange={(e) => setTaxPct(e.target.value)} />
                </div>
                <div>
                  <Label>Due in (days)</Label>
                  <Input type="number" value={dueDays} onChange={(e) => setDueDays(e.target.value)} />
                </div>
                <div className="text-right">
                  <div className="text-[10px] uppercase tracking-wider text-muted-foreground">
                    {splitPerCase && selectedIds.length > 1 ? "Combined total" : "Estimated total"}
                  </div>
                  <div className="font-serif text-2xl">{formatCurrency(total)}</div>
                  {tax > 0 && <div className="text-[11px] text-muted-foreground">{formatCurrency(subtotal)} + {formatCurrency(tax)} tax</div>}
                </div>
              </CardContent>
            </Card>
          </>
        )}

        <Card className="border-border/60">
          <CardContent className="p-4">
            <Label>Notes (optional)</Label>
            <Textarea rows={3} value={notes} onChange={(e) => setNotes(e.target.value)} placeholder="Payment terms, thank-you message…" />
          </CardContent>
        </Card>

        <div className="flex justify-end gap-2 pb-8">
          <Button variant="outline" onClick={() => navigate({ to: "/invoices" })}>Cancel</Button>
          <Button
            onClick={submit}
            disabled={saving || (!isRetainer && (cases.length === 0 || selectedIds.length === 0))}
          >
            {saving ? <Loader2 className="h-4 w-4 mr-2 animate-spin" /> : <FilePlus className="h-4 w-4 mr-2" />}
            {isRetainer
              ? "Create retainer invoice"
              : splitPerCase && selectedIds.length > 1
                ? `Generate ${selectedIds.length} draft invoices`
                : "Generate draft invoice"}
          </Button>
        </div>
      </div>
    </PageContainer>
  );
}