import { useEffect, useState } from 'react'
import { useNavigate, useParams } from 'react-router-dom'
import {
  type Assignment, type AssignmentType, type Consultant,
  getAssignment, updateAssignment, listAssignmentTypes, listConsultants,
} from '../db'

export default function AssignmentEdit() {
  const { id } = useParams()
  const navigate = useNavigate()
  const assignmentId = Number(id)

  const [assignment, setAssignment] = useState<Assignment | null>(null)
  const [assignmentTypes, setAssignmentTypes] = useState<AssignmentType[]>([])
  const [allConsultants, setAllConsultants] = useState<Consultant[]>([])

  // Form fields
  const [assignmentNumber, setAssignmentNumber] = useState('')
  const [title, setTitle] = useState('')
  const [client, setClient] = useState('')
  const [description, setDescription] = useState('')
  const [assignmentTypeId, setAssignmentTypeId] = useState(0)
  const [leadName, setLeadName] = useState('')
  const [status, setStatus] = useState<'active' | 'done'>('active')
  const [instituteeIds, setInstituteeIds] = useState<number[]>([])
  const [instituteeEnrollments, setInstituteeEnrollments] = useState<Array<{ instituteeId: number; from?: string; to?: string }>>([])
  const [plannedStart, setPlannedStart] = useState('')
  const [plannedEnd, setPlannedEnd] = useState('')
  const [typeChanged, setTypeChanged] = useState(false)
  const [addInstituteeId, setAddInstituteeId] = useState(0)

  useEffect(() => {
    const loadData = async () => {
      const [a, types, cons] = await Promise.all([
        getAssignment(assignmentId),
        listAssignmentTypes(),
        listConsultants(),
      ])
      if (!a) return
      setAssignment(a)
      setAssignmentTypes(types)
      setAllConsultants(cons)

      setAssignmentNumber(a.assignmentNumber ?? '')
      setTitle(a.title)
      setClient(a.client)
      setDescription(a.description ?? '')
      setAssignmentTypeId(a.assignmentTypeId)
      setLeadName(a.leadName)
      setStatus(a.status)
      setInstituteeIds(a.instituteeIds ?? [])
      setInstituteeEnrollments(a.instituteeEnrollments ?? [])
      setPlannedStart(a.plannedStart?.slice(0, 10) ?? '')
      setPlannedEnd(a.plannedEnd?.slice(0, 10) ?? '')
    }
    loadData()
  }, [assignmentId])

  const handleSave = async () => {
    await updateAssignment(assignmentId, {
      assignmentNumber: assignmentNumber.trim() || undefined,
      title,
      client,
      description: description.trim() || undefined,
      assignmentTypeId,
      leadName,
      status,
      instituteeIds,
      instituteeEnrollments,
      plannedStart: plannedStart || undefined,
      plannedEnd: plannedEnd || undefined,
    })
    navigate(`/assignment/${assignmentId}`)
  }

  const handleTypeChange = (newTypeId: number) => {
    if (newTypeId !== assignmentTypeId) setTypeChanged(true)
    setAssignmentTypeId(newTypeId)
  }

  const addInstitutee = () => {
    if (!addInstituteeId || instituteeIds.includes(addInstituteeId)) return
    setInstituteeIds(prev => [...prev, addInstituteeId])
    setInstituteeEnrollments(prev => [...prev, { instituteeId: addInstituteeId, from: '', to: '' }])
    setAddInstituteeId(0)
  }

  const removeInstitutee = (cid: number) => {
    setInstituteeIds(prev => prev.filter(id => id !== cid))
    setInstituteeEnrollments(prev => prev.filter(e => e.instituteeId !== cid))
  }

  const updateEnrollment = (cid: number, field: 'from' | 'to', value: string) => {
    setInstituteeEnrollments(prev =>
      prev.map(e => e.instituteeId === cid ? { ...e, [field]: value } : e)
    )
  }

  const availableConsultants = allConsultants.filter(c => !instituteeIds.includes(c.id!) && !c.archivedAt)

  if (!assignment) return <div className="text-center py-10 text-gray-400">Lädt…</div>

  return (
    <div className="space-y-4">
      {/* Header */}
      <div>
        <button onClick={() => navigate(`/assignment/${assignmentId}`)}
          className="text-sm text-brand mb-2 block">← Zurück</button>
        <h1 className="text-xl font-bold text-gray-800">Assignment bearbeiten</h1>
      </div>

      {/* Formular */}
      <div className="bg-white rounded-xl border border-gray-100 shadow-sm p-4 space-y-3">
        <div className="space-y-1">
          <label className="text-xs font-medium text-gray-500">Assignment-Nummer</label>
          <input
            className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
            placeholder="z. B. CGI-2024-001"
            value={assignmentNumber}
            onChange={e => setAssignmentNumber(e.target.value)}
          />
        </div>
        <div className="space-y-1">
          <label className="text-xs font-medium text-gray-500">Titel</label>
          <input
            className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
            value={title}
            onChange={e => setTitle(e.target.value)}
          />
        </div>
        <div className="space-y-1">
          <label className="text-xs font-medium text-gray-500">Kunde</label>
          <input
            className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
            value={client}
            onChange={e => setClient(e.target.value)}
          />
        </div>
        <div className="space-y-1">
          <label className="text-xs font-medium text-gray-500">Beschreibung</label>
          <textarea
            className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
            rows={3}
            value={description}
            onChange={e => setDescription(e.target.value)}
          />
        </div>
        <div className="grid grid-cols-2 gap-2">
          <div className="space-y-1">
            <label className="text-xs font-medium text-gray-500">Geplanter Beginn</label>
            <input
              type="date"
              className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
              value={plannedStart}
              onChange={e => setPlannedStart(e.target.value)}
            />
          </div>
          <div className="space-y-1">
            <label className="text-xs font-medium text-gray-500">Geplantes Ende</label>
            <input
              type="date"
              className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
              value={plannedEnd}
              onChange={e => setPlannedEnd(e.target.value)}
            />
          </div>
        </div>
        <div className="space-y-1">
          <label className="text-xs font-medium text-gray-500">Assignment-Typ</label>
          <select
            className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
            value={assignmentTypeId}
            onChange={e => handleTypeChange(Number(e.target.value))}>
            {assignmentTypes.map(t => (
              <option key={t.id} value={t.id}>{t.name}</option>
            ))}
          </select>
          {typeChanged && (
            <div className="text-xs text-amber-600 bg-amber-50 border border-amber-200 rounded-lg px-3 py-2 mt-1">
              ⚠️ Bestehende Meetings bleiben erhalten
            </div>
          )}
        </div>
        <div className="space-y-1">
          <label className="text-xs font-medium text-gray-500">Lead</label>
          <input
            className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
            value={leadName}
            onChange={e => setLeadName(e.target.value)}
          />
        </div>
        <div className="space-y-1">
          <label className="text-xs font-medium text-gray-500">Status</label>
          <select
            className="w-full border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
            value={status}
            onChange={e => setStatus(e.target.value as 'active' | 'done')}>
            <option value="active">Aktiv</option>
            <option value="done">Abgeschlossen</option>
          </select>
        </div>
      </div>

      {/* Institutees */}
      <div className="bg-white rounded-xl border border-gray-100 shadow-sm p-4 space-y-3">
        <h2 className="font-semibold text-gray-800">Institutees</h2>

        {instituteeIds.length === 0 && (
          <p className="text-sm text-gray-400">Noch keine Institutees zugewiesen.</p>
        )}

        {instituteeIds.map(cid => {
          const consultant = allConsultants.find(c => c.id === cid)
          const enrollment = instituteeEnrollments.find(e => e.instituteeId === cid)
          if (!consultant) return null
          return (
            <div key={cid} className="flex items-center gap-2 flex-wrap border border-gray-100 rounded-lg px-3 py-2">
              <span className="text-sm font-medium text-gray-700 flex-1 min-w-[100px]">
                {consultant.firstName} {consultant.lastName}
              </span>
              <div className="flex items-center gap-1">
                <span className="text-xs text-gray-400">Von</span>
                <input
                  type="date"
                  className="border border-gray-200 rounded px-2 py-1 text-xs focus:outline-none focus:border-brand"
                  value={enrollment?.from ?? ''}
                  onChange={e => updateEnrollment(cid, 'from', e.target.value)}
                />
              </div>
              <div className="flex items-center gap-1">
                <span className="text-xs text-gray-400">Bis</span>
                <input
                  type="date"
                  className="border border-gray-200 rounded px-2 py-1 text-xs focus:outline-none focus:border-brand"
                  value={enrollment?.to ?? ''}
                  onChange={e => updateEnrollment(cid, 'to', e.target.value)}
                />
              </div>
              <button
                onClick={() => removeInstitutee(cid)}
                className="text-red-300 hover:text-red-500 text-sm px-1">
                ×
              </button>
            </div>
          )
        })}

        {/* Institutee hinzufügen */}
        {availableConsultants.length > 0 && (
          <div className="flex gap-2">
            <select
              className="flex-1 border border-gray-200 rounded-lg px-3 py-2 text-sm focus:outline-none focus:border-brand"
              value={addInstituteeId}
              onChange={e => setAddInstituteeId(Number(e.target.value))}>
              <option value={0}>Institutee auswählen…</option>
              {availableConsultants.map(c => (
                <option key={c.id} value={c.id}>{c.firstName} {c.lastName}</option>
              ))}
            </select>
            <button
              onClick={addInstitutee}
              disabled={!addInstituteeId}
              className="px-4 py-2 bg-brand text-white text-sm rounded-lg font-medium disabled:opacity-40">
              Hinzufügen
            </button>
          </div>
        )}
      </div>

      {/* Aktionen */}
      <div className="flex gap-3">
        <button
          onClick={handleSave}
          className="flex-1 py-3 bg-brand text-white rounded-xl text-sm font-semibold">
          Speichern
        </button>
        <button
          onClick={() => navigate(`/assignment/${assignmentId}`)}
          className="px-5 py-3 border border-gray-200 text-gray-500 rounded-xl text-sm">
          Abbrechen
        </button>
      </div>
    </div>
  )
}