import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react'
import { collectSkillLeavesFromTree, buildSkillCatalogTree } from '../utils/skillCatalogTree'
import SkillTreePickerPanel from './SkillTreePickerPanel'

function normId(id) {
  return String(id)
}

/**
 * Mehrfachauswahl Fähigkeiten mit hierarchischer Treeview („Alle“) und Pfad-Suche.
 */
export default function SkillTreeMultiSelect({
  value = [],
  onChange,
  skills = [],
  placeholder = 'Fähigkeit suchen …',
  browseLabel = '▼ Katalog',
  emptyHint = 'Keine Treffer',
  className = '',
}) {
  const [query, setQuery] = useState('')
  const [open, setOpen] = useState(false)
  const [browseTree, setBrowseTree] = useState(false)
  const rootRef = useRef(null)

  const tree = useMemo(() => buildSkillCatalogTree(skills), [skills])
  const selectedSet = useMemo(() => new Set(value.map(normId)), [value])

  const leaves = useMemo(() => collectSkillLeavesFromTree(tree, value), [tree, value])

  const selectedLabels = useMemo(() => {
    return value.map((id) => {
      const leaf = leaves.find((l) => normId(l.id) === normId(id)) || leaves.find(() => false)
      const fromSkills = skills.find((s) => normId(s.id) === normId(id))
      return leaf?.pathLabel || fromSkills?.name || `#${id}`
    })
  }, [value, leaves, skills])

  const addId = useCallback(
    (id) => {
      const sid = normId(id)
      if (selectedSet.has(sid)) return
      onChange([...value, id])
      setQuery('')
      setBrowseTree(false)
    },
    [value, onChange, selectedSet]
  )

  const removeAt = useCallback(
    (idx) => {
      onChange(value.filter((_, i) => i !== idx))
    },
    [value, onChange]
  )

  useEffect(() => {
    const onDoc = (e) => {
      if (!rootRef.current?.contains(e.target)) {
        setOpen(false)
        setBrowseTree(false)
      }
    }
    document.addEventListener('mousedown', onDoc)
    return () => document.removeEventListener('mousedown', onDoc)
  }, [])

  const showTree = browseTree || !query.trim()

  return (
    <div className={`multiselect-combo skill-tree-multiselect ${className}`.trim()} ref={rootRef}>
      <div className="multiselect-combo__chips">
        {value.map((id, idx) => (
          <button
            key={`${normId(id)}-${idx}`}
            type="button"
            className="multiselect-combo__chip"
            onClick={() => removeAt(idx)}
            title="Entfernen"
          >
            <span>{selectedLabels[idx]}</span>
            <span className="multiselect-combo__chip-x" aria-hidden>
              ×
            </span>
          </button>
        ))}
      </div>
      <div className="multiselect-combo__field">
        <input
          type="text"
          className="form-input multiselect-combo__input"
          placeholder={placeholder}
          value={query}
          onChange={(e) => {
            setQuery(e.target.value)
            setOpen(true)
            setBrowseTree(false)
          }}
          onFocus={() => setOpen(true)}
          autoComplete="off"
          aria-expanded={open}
        />
        <button
          type="button"
          className="btn multiselect-combo__browse"
          title="Katalog als Baum"
          onClick={() => {
            setOpen(true)
            setBrowseTree(true)
            setQuery('')
          }}
        >
          {browseLabel}
        </button>
      </div>
      {open ? (
        <div className="skill-tree-multiselect__panel">
          {showTree ? (
            <SkillTreePickerPanel
              skills={skills}
              excludeIds={value}
              searchQuery={query}
              onPickSkill={(id) => addId(id)}
              pickMode="multi"
            />
          ) : (
            <ul className="multiselect-combo__list" role="listbox">
              {leaves.filter((l) => l.pathLabel.toLowerCase().includes(query.trim().toLowerCase())).length ===
              0 ? (
                <li className="multiselect-combo__empty">{emptyHint}</li>
              ) : (
                leaves
                  .filter((l) => l.pathLabel.toLowerCase().includes(query.trim().toLowerCase()))
                  .map((l) => (
                    <li key={normId(l.id)}>
                      <button
                        type="button"
                        className="multiselect-combo__opt skill-tree__pick--path"
                        onMouseDown={(e) => e.preventDefault()}
                        onClick={() => addId(l.id)}
                      >
                        <span className="skill-tree__pick-name">{l.label}</span>
                        <span className="skill-tree__pick-path">{l.pathLabel}</span>
                      </button>
                    </li>
                  ))
              )}
            </ul>
          )}
        </div>
      ) : null}
    </div>
  )
}