"use client";

import { CalendarOff } from "lucide-react";
import Link from "next/link";
import { useRouter } from "next/navigation";
import { useState, useTransition } from "react";
import { Button } from "@/components/ui/button";
import { BottomSheet } from "@/components/ui/bottom-sheet";
import { Input } from "@/components/ui/input";
import type { BlockTimeConflict } from "../actions/block-time";
import { blockTimeAction } from "../actions/block-time";

function toMinutes(hhmm: string): number | null {
  const match = /^(\d{2}):(\d{2})$/.exec(hhmm);
  if (!match) return null;
  return Number(match[1]) * 60 + Number(match[2]);
}

export function BlockTimeButton({ date }: { date: string }) {
  const [open, setOpen] = useState(false);
  const [startTime, setStartTime] = useState("12:00");
  const [endTime, setEndTime] = useState("13:00");
  const [reason, setReason] = useState("");
  const [error, setError] = useState<string | null>(null);
  const [conflicts, setConflicts] = useState<BlockTimeConflict[] | null>(null);
  const [isPending, startTransition] = useTransition();
  const router = useRouter();

  const handleClose = () => {
    setOpen(false);
    setError(null);
    setConflicts(null);
    setReason("");
  };

  const submit = (acknowledgeConflicts: boolean) => {
    const startMinutes = toMinutes(startTime);
    const endMinutes = toMinutes(endTime);
    if (startMinutes === null || endMinutes === null || startMinutes >= endMinutes) {
      setError("Start time must be before end time.");
      return;
    }
    setError(null);
    startTransition(async () => {
      const result = await blockTimeAction({
        date,
        startMinutes,
        endMinutes,
        reason,
        acknowledgeConflicts,
      });
      if (!result.success) {
        setError(result.error ?? "Something went wrong.");
        setConflicts(result.conflicts ?? null);
        return;
      }
      setOpen(false);
      setConflicts(null);
      router.refresh();
    });
  };

  return (
    <>
      <Button variant="secondary" size="sm" aria-label="Block Time" onClick={() => setOpen(true)}>
        <CalendarOff className="h-4 w-4" aria-hidden="true" />
        <span className="hidden sm:inline">Block Time</span>
      </Button>
      <BottomSheet open={open} onClose={handleClose} title="Block Time">
        <div className="space-y-4 pb-2">
          <p className="text-muted text-sm">
            Reserve part of{" "}
            {new Date(`${date}T00:00:00`).toLocaleDateString("en-GB", {
              weekday: "long",
              day: "numeric",
              month: "short",
            })}{" "}
            for something other than appointments — a meeting, admin, a personal break.
          </p>

          {conflicts && conflicts.length > 0 ? (
            <div className="space-y-3">
              <p role="alert" className="text-danger text-sm font-medium">
                This overlaps {conflicts.length} existing appointment
                {conflicts.length > 1 ? "s" : ""}:
              </p>
              <ul className="space-y-2">
                {conflicts.map((c) => (
                  <li key={c.id} className="border-line rounded-lg border bg-white p-3 text-xs">
                    <Link href={`/staff/appointments/${c.id}`} className="font-bold underline">
                      {c.customerName}
                    </Link>
                    <p className="text-muted">{c.serviceNames}</p>
                  </li>
                ))}
              </ul>
              <div className="flex gap-3">
                <Button variant="secondary" className="flex-1" onClick={handleClose}>
                  Cancel
                </Button>
                <Button
                  variant="destructive"
                  className="flex-1"
                  isLoading={isPending}
                  onClick={() => submit(true)}
                >
                  Block Anyway
                </Button>
              </div>
            </div>
          ) : (
            <>
              <div className="grid grid-cols-2 gap-4">
                <Input
                  label="Start"
                  type="time"
                  value={startTime}
                  onChange={(e) => setStartTime(e.target.value)}
                />
                <Input
                  label="End"
                  type="time"
                  value={endTime}
                  onChange={(e) => setEndTime(e.target.value)}
                />
              </div>
              <Input
                label="Reason (optional)"
                placeholder="e.g. Team meeting"
                value={reason}
                onChange={(e) => setReason(e.target.value)}
              />
              {error && (
                <p role="alert" className="text-danger text-sm font-medium">
                  {error}
                </p>
              )}
              <Button className="w-full" isLoading={isPending} onClick={() => submit(false)}>
                Block This Time
              </Button>
            </>
          )}
        </div>
      </BottomSheet>
    </>
  );
}