'use client';

import { useState } from 'react';
import { Calendar } from 'lucide-react';

import { Button } from '@/components/ui/button';
import { Popover, PopoverContent, PopoverTrigger } from '@/components/ui/popover';
import { cn } from '@/lib/utils';
import { isCustomRange, type DateRange } from '@/lib/analytics/range';

interface DateRangePickerProps {
  value: DateRange;
  onChange: (next: DateRange) => void;
  className?: string;
}

const PRESETS: Array<{ value: 'today' | '7d' | '30d' | '90d'; label: string }> = [
  { value: 'today', label: 'Today' },
  { value: '7d', label: '7d' },
  { value: '30d', label: '30d' },
  { value: '90d', label: '90d' },
];

/**
 * Format a custom range as a compact button label, e.g. "Apr 14 – May 4".
 * Same year omits the year on both sides; different years includes both.
 */
function formatCustom(range: { from: string; to: string }): string {
  const from = new Date(`${range.from}T00:00:00.000Z`);
  const to = new Date(`${range.to}T00:00:00.000Z`);
  const sameYear = from.getUTCFullYear() === to.getUTCFullYear();
  const fmt: Intl.DateTimeFormatOptions = sameYear
    ? { month: 'short', day: 'numeric', timeZone: 'UTC' }
    : { month: 'short', day: 'numeric', year: 'numeric', timeZone: 'UTC' };
  return `${from.toLocaleDateString(undefined, fmt)} – ${to.toLocaleDateString(undefined, fmt)}`;
}

/**
 * Today's date as a YYYY-MM-DD string in UTC. Used as the default for the
 * "to" picker so users can't accidentally pick a future date by leaving the
 * field empty.
 */
function todayIso(): string {
  return new Date().toISOString().slice(0, 10);
}

export function DateRangePicker({ value, onChange, className }: DateRangePickerProps) {
  const [open, setOpen] = useState(false);
  const isCustom = isCustomRange(value);

  // Local state for the popover form. Seeded from the current value if it's
  // already custom, otherwise defaults to a 14-day window ending today.
  const [draftFrom, setDraftFrom] = useState<string>(() => {
    if (isCustom) return value.from;
    const d = new Date();
    d.setUTCDate(d.getUTCDate() - 14);
    return d.toISOString().slice(0, 10);
  });
  const [draftTo, setDraftTo] = useState<string>(() => (isCustom ? value.to : todayIso()));

  const today = todayIso();
  const draftValid =
    draftFrom !== '' &&
    draftTo !== '' &&
    draftFrom <= draftTo &&
    draftFrom <= today &&
    draftTo <= today;

  function applyCustom() {
    if (!draftValid) return;
    onChange({ kind: 'custom', from: draftFrom, to: draftTo });
    setOpen(false);
  }

  return (
    <div
      role="tablist"
      aria-label="Date range"
      className={cn(
        'inline-flex items-center rounded-lg border border-border bg-muted/40 p-0.5 shadow-xs',
        className,
      )}
    >
      {PRESETS.map((opt) => {
        const active = !isCustom && opt.value === value;
        return (
          <Button
            key={opt.value}
            type="button"
            role="tab"
            aria-selected={active}
            variant="ghost"
            size="sm"
            onClick={() => onChange(opt.value)}
            className={cn(
              'h-7 px-3 text-xs font-medium transition-all duration-base ease-spring',
              active
                ? 'bg-background text-foreground shadow-sm'
                : 'text-muted-foreground hover:text-foreground',
            )}
            data-testid={`range-${opt.value}`}
          >
            {opt.label}
          </Button>
        );
      })}

      {/* Custom range - popover with two date inputs and an Apply button */}
      <Popover open={open} onOpenChange={setOpen}>
        <PopoverTrigger asChild>
          <Button
            type="button"
            role="tab"
            aria-selected={isCustom}
            variant="ghost"
            size="sm"
            className={cn(
              'h-7 px-3 text-xs font-medium transition-all duration-base ease-spring inline-flex items-center gap-1',
              isCustom
                ? 'bg-background text-foreground shadow-sm'
                : 'text-muted-foreground hover:text-foreground',
            )}
            data-testid="range-custom"
          >
            <Calendar className="h-3 w-3" aria-hidden />
            {isCustom ? formatCustom(value) : 'Custom'}
          </Button>
        </PopoverTrigger>
        <PopoverContent
          align="end"
          // min() caps the popover at "viewport minus 16px" on narrow
          // phones so it never overflows; otherwise sits at a compact
          // 260px. Date inputs inside use w-auto so iOS's intrinsic
          // date-input width (which ignores parent constraints) sizes
          // to its own content rather than overflowing.
          className="w-[min(260px,calc(100vw-1rem))] p-3"
        >
          <div className="space-y-3">
            <div className="text-xs font-medium uppercase tracking-wide text-muted-foreground">
              Custom range
            </div>
            <label className="block text-xs">
              <span className="block text-muted-foreground mb-1">From</span>
              <input
                type="date"
                value={draftFrom}
                /* `max` capped at min(draftTo, today). Without the today
                   cap, users could pick a future From, end up with an
                   empty result, and not understand why. */
                max={draftTo && draftTo < today ? draftTo : today}
                onChange={(e) => setDraftFrom(e.target.value)}
                className="w-auto max-w-full rounded-md border border-input bg-background px-2 py-1.5 text-sm outline-hidden focus:border-brand/60 focus:ring-2 focus:ring-brand/15"
              />
            </label>
            <label className="block text-xs">
              <span className="block text-muted-foreground mb-1">To</span>
              <input
                type="date"
                value={draftTo}
                min={draftFrom || undefined}
                max={today}
                onChange={(e) => setDraftTo(e.target.value)}
                className="w-auto max-w-full rounded-md border border-input bg-background px-2 py-1.5 text-sm outline-hidden focus:border-brand/60 focus:ring-2 focus:ring-brand/15"
              />
            </label>
            <div className="flex items-center justify-end gap-2 pt-1">
              <Button variant="ghost" size="sm" onClick={() => setOpen(false)}>
                Cancel
              </Button>
              <Button size="sm" onClick={applyCustom} disabled={!draftValid}>
                Apply
              </Button>
            </div>
          </div>
        </PopoverContent>
      </Popover>
    </div>
  );
}