import { useEffect, useRef, useState } from 'react'

// One axis's collapse control, as a stepper.
//
// Rows and columns are the same thing — a depth in ViewConfig, counting the
// levels to show — so one component draws both.
//
// It used to be one button per level, which is N+1 controls that grow with the
// pivot: a 5-by-3 layout rendered ten of them, and the active level was a blue
// button somewhere among the greys, so reading the current state meant scanning.
// A stepper is three controls whatever the depth, and says where you are rather
// than making you find it. The full list is still one click away, for jumping
// rather than stepping.
export default function DepthButtons({ label, levels, depth, onPick, totalLabel = 'Total', children }) {
  const [open, setOpen] = useState(false)
  const boxRef = useRef(null)

  useEffect(() => {
    if (!open) return
    const onDown = (e) => { if (!boxRef.current?.contains(e.target)) setOpen(false) }
    const onKey  = (e) => { if (e.key === 'Escape') setOpen(false) }
    // Capture phase: the pivot lives in a shadow root and retargets its events,
    // so a bubbled listener sees the host rather than the real target.
    document.addEventListener('mousedown', onDown, true)
    window.addEventListener('keydown', onKey)
    return () => {
      document.removeEventListener('mousedown', onDown, true)
      window.removeEventListener('keydown', onKey)
    }
  }, [open])

  const max = levels.length
  // depth is null until the first layout has been read back. Showing the last
  // level would be a guess; an em dash is honest and the arrows still work.
  const known   = depth != null
  const current = !known ? '—' : (depth === 0 ? totalLabel : levels[depth - 1])
  const step    = (d) => onPick(Math.min(max, Math.max(0, d)))
  // Capped so one long field name cannot push the rest of the toolbar off;
  // past the cap the label truncates, with the full name in the title.
  const widest  = Math.min(18, Math.max(...[totalLabel, ...levels].map(l => String(l).length)))

  // One joined control, in the style of the operation panel's
  // Scale | Recode | Clone. The arrows used to be separate outlined boxes a
  // few pixels wide, which in dark mode were barely visible and looked the
  // same enabled or disabled; joined, the axis reads as one object and the
  // arrows are halves of it rather than specks beside it.
  const seg = 'px-1.5 py-0.5 leading-none bg-white transition-colors ' +
              'text-gray-600 hover:bg-gray-100 disabled:text-gray-300 disabled:hover:bg-white disabled:cursor-default'

  return (
    <div ref={boxRef} className="relative flex items-center gap-1.5">
      <span className="pf-section-label">{label}</span>

      <div className="inline-flex rounded border border-gray-300 divide-x divide-gray-300 overflow-hidden">
        <button className={seg} disabled={!known || depth <= 0}
          title={`Collapse ${label.toLowerCase()} by one level`}
          onClick={() => step((depth ?? 0) - 1)}>◂</button>

        {/* Sized to the axis's longest level, not the current one. Sized to
            its content it resized on every step, so the ▸ moved out from
            under the cursor between clicks. */}
        <button onClick={() => setOpen(o => !o)}
          title={`${label}: showing ${current}`}
          style={{ width: `calc(${widest}ch + 1rem)` }}
          className={`px-2 py-0.5 truncate text-left transition-colors
            ${open ? 'bg-blue-50 text-blue-700' : 'bg-white text-gray-700 hover:bg-gray-100'}`}>
          {current}
        </button>

        <button className={seg} disabled={!known || depth >= max}
          title={`Expand ${label.toLowerCase()} by one level`}
          onClick={() => step((depth ?? 0) + 1)}>▸</button>
      </div>

      {children}

      {open && (
        <div className="absolute top-full left-0 mt-1 z-50 min-w-[10rem] bg-white border
                        border-gray-200 rounded shadow-lg py-1 text-xs">
          {Array.from({ length: max + 1 }, (_, n) => (
            <button key={n} onClick={() => { onPick(n); setOpen(false) }}
              title={n === 0
                ? `Collapse ${label.toLowerCase()} to a single total`
                : `Show ${label.toLowerCase()} down to ${levels.slice(0, n).join(' › ')}`}
              className={`block w-full text-left px-3 py-1 truncate
                ${depth === n ? 'bg-blue-50 text-blue-700' : 'text-gray-700 hover:bg-gray-50'}`}>
              {n === 0 ? totalLabel : levels[n - 1]}
            </button>
          ))}
        </div>
      )}
    </div>
  )
}

// An on/off control that looks pressed when on — the same state the toolbar's
// Operations button uses for "open". Replaces the native checkboxes, which
// drew in the light style on the dark theme and were the brightest thing on
// the toolbar.
export function ToggleChip({ on, onChange, title, children }) {
  return (
    <button type="button" aria-pressed={on} title={title} onClick={() => onChange(!on)}
      className={`border rounded px-2 py-0.5 transition-colors ${
        on ? 'pf-pressed' : 'border-gray-300 bg-white text-gray-500 hover:bg-gray-100'}`}>
      {children}
    </button>
  )
}