'use client'

import { useEffect, useState } from 'react'
import { useSession } from 'next-auth/react'
import { useRouter } from 'next/navigation'
import { apiClient } from '@/lib/api-client'

interface DepartmentTreeNode {
  id: number
  code: string
  name: string
  name_en?: string
  depth: number
  parent_id: number | null
  email_domain?: string
  effective_email_domain?: string
  email_address?: string
  email_quota_mb: number
  description?: string
  is_active: boolean
  is_top_level: boolean
  member_count: number
  children: DepartmentTreeNode[]
}

interface DepartmentFormData {
  name: string
  name_en: string
  code: string
  description: string
  email_domain: string
  email_address: string
  email_quota_mb: number
  parent_id: number | null
}

const EMPTY_FORM: DepartmentFormData = {
  name: '',
  name_en: '',
  code: '',
  description: '',
  email_domain: '',
  email_address: '',
  email_quota_mb: 5120,
  parent_id: null,
}

// ─── Modal：新增 / 編輯部門 ─────────────────────────────────────────────
function DepartmentModal({
  mode,
  parentDept,
  editTarget,
  onClose,
  onSaved,
}: {
  mode: 'create_top' | 'create_child' | 'edit'
  parentDept?: DepartmentTreeNode    // create_child 時的父部門
  editTarget?: DepartmentTreeNode    // edit 時的目標部門
  onClose: () => void
  onSaved: () => void
}) {
  const [form, setForm] = useState<DepartmentFormData>(() => {
    if (mode === 'edit' && editTarget) {
      return {
        name: editTarget.name,
        name_en: editTarget.name_en ?? '',
        code: editTarget.code,
        description: editTarget.description ?? '',
        email_domain: editTarget.email_domain ?? '',
        email_address: editTarget.email_address ?? '',
        email_quota_mb: editTarget.email_quota_mb,
        parent_id: editTarget.parent_id,
      }
    }
    if (mode === 'create_child' && parentDept) {
      return { ...EMPTY_FORM, parent_id: parentDept.id }
    }
    return { ...EMPTY_FORM }
  })
  const [saving, setSaving] = useState(false)
  const [error, setError] = useState<string | null>(null)

  const isTopLevel = mode === 'create_top' || (mode === 'edit' && editTarget?.depth === 0)
  const isEdit = mode === 'edit'

  const titleMap = {
    create_top: '新增第一層部門',
    create_child: `新增子部門 (隸屬: ${parentDept?.name})`,
    edit: `編輯部門：${editTarget?.name}`,
  }

  const handleSubmit = async (e: React.FormEvent) => {
    e.preventDefault()
    setSaving(true)
    setError(null)

    try {
      const payload: Record<string, unknown> = {
        name: form.name.trim(),
        code: form.code.trim().toUpperCase(),
        description: form.description.trim() || null,
        email_address: form.email_address.trim() || null,
        email_quota_mb: form.email_quota_mb,
      }
      if (form.name_en.trim()) payload.name_en = form.name_en.trim()

      if (isEdit) {
        // 編輯：PUT，只有第一層可更新 email_domain
        if (isTopLevel) payload.email_domain = form.email_domain.trim() || null
        await apiClient.put(`/departments/${editTarget!.id}`, payload)
      } else {
        // 新增：POST
        payload.parent_id = form.parent_id ?? null
        if (isTopLevel) payload.email_domain = form.email_domain.trim() || null
        await apiClient.post('/departments/', payload)
      }

      onSaved()
      onClose()
    } catch (err: unknown) {
      const msg =
        err instanceof Error ? err.message : '操作失敗，請稍後再試'
      setError(msg)
    } finally {
      setSaving(false)
    }
  }

  return (
    <div className="fixed inset-0 bg-black/40 flex items-center justify-center z-50 p-4">
      <div className="bg-white rounded-xl shadow-xl w-full max-w-lg">
        {/* Header */}
        <div className="flex items-center justify-between px-6 py-4 border-b">
          <h2 className="text-lg font-semibold text-gray-900">{titleMap[mode]}</h2>
          <button onClick={onClose} className="text-gray-400 hover:text-gray-600 text-2xl leading-none">&times;</button>
        </div>

        {/* Form */}
        <form onSubmit={handleSubmit} className="px-6 py-4 space-y-4">
          {error && (
            <div className="p-3 bg-red-50 border border-red-200 rounded text-red-700 text-sm">{error}</div>
          )}

          <div className="grid grid-cols-2 gap-4">
            <div>
              <label className="block text-sm font-medium text-gray-700 mb-1">
                部門名稱 <span className="text-red-500">*</span>
              </label>
              <input
                type="text"
                required
                value={form.name}
                onChange={(e) => setForm({ ...form, name: e.target.value })}
                className="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500"
                placeholder="例：業務發展部"
              />
            </div>
            <div>
              <label className="block text-sm font-medium text-gray-700 mb-1">英文名稱</label>
              <input
                type="text"
                value={form.name_en}
                onChange={(e) => setForm({ ...form, name_en: e.target.value })}
                className="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500"
                placeholder="例：Business Development"
              />
            </div>
          </div>

          <div>
            <label className="block text-sm font-medium text-gray-700 mb-1">
              部門代碼 <span className="text-red-500">*</span>
              {isEdit && <span className="text-gray-400 font-normal ml-1">(建立後不可修改)</span>}
            </label>
            <input
              type="text"
              required
              disabled={isEdit}
              value={form.code}
              onChange={(e) => setForm({ ...form, code: e.target.value.toUpperCase() })}
              className="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500 disabled:bg-gray-100 disabled:text-gray-500"
              placeholder="例：BD"
            />
          </div>

          {isTopLevel && (
            <div>
              <label className="block text-sm font-medium text-gray-700 mb-1">
                郵件網域
                <span className="text-gray-400 font-normal ml-1">(第一層專屬，例：ease.taipei)</span>
              </label>
              <input
                type="text"
                value={form.email_domain}
                onChange={(e) => setForm({ ...form, email_domain: e.target.value })}
                className="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500 font-mono"
                placeholder="ease.taipei"
              />
            </div>
          )}

          <div>
            <label className="block text-sm font-medium text-gray-700 mb-1">部門信箱</label>
            <input
              type="email"
              value={form.email_address}
              onChange={(e) => setForm({ ...form, email_address: e.target.value })}
              className="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500 font-mono"
              placeholder="例：business@ease.taipei"
            />
          </div>

          <div>
            <label className="block text-sm font-medium text-gray-700 mb-1">
              信箱配額 (MB)
            </label>
            <input
              type="number"
              min={512}
              value={form.email_quota_mb}
              onChange={(e) => setForm({ ...form, email_quota_mb: parseInt(e.target.value) || 5120 })}
              className="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500"
            />
            <p className="text-xs text-gray-400 mt-1">{(form.email_quota_mb / 1024).toFixed(1)} GB</p>
          </div>

          <div>
            <label className="block text-sm font-medium text-gray-700 mb-1">說明</label>
            <textarea
              rows={2}
              value={form.description}
              onChange={(e) => setForm({ ...form, description: e.target.value })}
              className="w-full border border-gray-300 rounded-lg px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500 resize-none"
              placeholder="選填"
            />
          </div>

          <div className="flex justify-end gap-3 pt-2 border-t">
            <button
              type="button"
              onClick={onClose}
              className="px-4 py-2 text-sm text-gray-700 border border-gray-300 rounded-lg hover:bg-gray-50"
            >
              取消
            </button>
            <button
              type="submit"
              disabled={saving}
              className="px-4 py-2 text-sm text-white bg-blue-600 rounded-lg hover:bg-blue-700 disabled:opacity-60"
            >
              {saving ? '儲存中...' : '儲存'}
            </button>
          </div>
        </form>
      </div>
    </div>
  )
}

// ─── 確認停用 Modal ──────────────────────────────────────────────────────
function DeactivateModal({
  dept,
  onClose,
  onConfirm,
}: {
  dept: DepartmentTreeNode
  onClose: () => void
  onConfirm: () => void
}) {
  return (
    <div className="fixed inset-0 bg-black/40 flex items-center justify-center z-50 p-4">
      <div className="bg-white rounded-xl shadow-xl w-full max-w-sm">
        <div className="px-6 py-4 border-b">
          <h2 className="text-lg font-semibold text-gray-900">確認停用部門</h2>
        </div>
        <div className="px-6 py-4">
          <p className="text-gray-700">
            確定要停用 <strong>{dept.name}</strong> ({dept.code}) 嗎？
          </p>
          <p className="text-sm text-gray-500 mt-2">
            停用後該部門不再顯示於主要清單，現有成員歸屬不受影響。
          </p>
        </div>
        <div className="flex justify-end gap-3 px-6 py-4 border-t">
          <button
            onClick={onClose}
            className="px-4 py-2 text-sm text-gray-700 border border-gray-300 rounded-lg hover:bg-gray-50"
          >
            取消
          </button>
          <button
            onClick={onConfirm}
            className="px-4 py-2 text-sm text-white bg-red-600 rounded-lg hover:bg-red-700"
          >
            確認停用
          </button>
        </div>
      </div>
    </div>
  )
}

// ─── 部門節點 ────────────────────────────────────────────────────────────
function DepartmentNode({
  node,
  level = 0,
  onAddChild,
  onEdit,
  onDeactivate,
}: {
  node: DepartmentTreeNode
  level?: number
  onAddChild: (parent: DepartmentTreeNode) => void
  onEdit: (dept: DepartmentTreeNode) => void
  onDeactivate: (dept: DepartmentTreeNode) => void
}) {
  const [expanded, setExpanded] = useState(level === 0)
  const hasChildren = node.children && node.children.length > 0
  const indent = level * 24

  return (
    <div className="border border-gray-200 rounded-lg mb-2">
      <div
        className={`flex items-center justify-between p-4 transition-colors ${
          level === 0 ? 'bg-white hover:bg-gray-50' : 'bg-gray-50 hover:bg-gray-100'
        }`}
        style={{ paddingLeft: `${16 + indent}px` }}
      >
        {/* 展開/收合按鈕區 */}
        <div
          className="flex items-center gap-3 flex-1 min-w-0 cursor-pointer"
          onClick={() => hasChildren && setExpanded(!expanded)}
        >
          <span className="text-xl flex-shrink-0">
            {level === 0 ? (expanded ? '📂' : '📁') : level === 1 ? '📋' : '📌'}
          </span>

          <div className="flex-1 min-w-0">
            <div className="flex items-center gap-2 flex-wrap">
              <h3 className={`font-semibold text-gray-900 ${level === 0 ? 'text-lg' : 'text-base'}`}>
                {node.name}
              </h3>
              {node.name_en && (
                <span className="text-xs text-gray-500">{node.name_en}</span>
              )}
              <span className="text-xs text-gray-500 bg-gray-100 px-2 py-0.5 rounded">{node.code}</span>
              {level === 0 && node.email_domain && (
                <span className="text-xs text-blue-600 bg-blue-50 px-2 py-0.5 rounded font-mono">
                  @{node.email_domain}
                </span>
              )}
            </div>

            {node.email_address && (
              <p className="text-sm text-blue-600 font-mono mt-0.5">{node.email_address}</p>
            )}
            {!node.email_address && node.effective_email_domain && level > 0 && (
              <p className="text-xs text-gray-400 mt-0.5">繼承網域: @{node.effective_email_domain}</p>
            )}
            {node.description && (
              <p className="text-xs text-gray-500 mt-0.5">{node.description}</p>
            )}
          </div>
        </div>

        {/* 右側資訊 + 操作按鈕 */}
        <div className="flex items-center gap-2 flex-shrink-0 ml-4">
          <span className="text-sm text-gray-500 whitespace-nowrap">{node.member_count} 位成員</span>

          {hasChildren && (
            <button
              onClick={() => setExpanded(!expanded)}
              className="text-gray-400 hover:text-gray-600 p-1"
            >
              <svg className={`w-4 h-4 transition-transform ${expanded ? 'rotate-180' : ''}`}
                fill="none" stroke="currentColor" viewBox="0 0 24 24">
                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M19 9l-7 7-7-7" />
              </svg>
            </button>
          )}

          {/* 操作按鈕 */}
          <button
            onClick={() => onAddChild(node)}
            title="新增子部門"
            className="text-xs text-green-600 border border-green-200 bg-green-50 hover:bg-green-100 rounded px-2 py-1"
          >
            + 子部門
          </button>
          <button
            onClick={() => onEdit(node)}
            title="編輯"
            className="text-xs text-blue-600 border border-blue-200 bg-blue-50 hover:bg-blue-100 rounded px-2 py-1"
          >
            編輯
          </button>
          <button
            onClick={() => onDeactivate(node)}
            title="停用"
            className="text-xs text-red-500 border border-red-200 bg-red-50 hover:bg-red-100 rounded px-2 py-1"
          >
            停用
          </button>
        </div>
      </div>

      {/* 子部門 */}
      {expanded && hasChildren && (
        <div className="border-t border-gray-100 divide-y divide-gray-100">
          {node.children.map((child) => (
            <DepartmentNode
              key={child.id}
              node={child}
              level={level + 1}
              onAddChild={onAddChild}
              onEdit={onEdit}
              onDeactivate={onDeactivate}
            />
          ))}
        </div>
      )}
    </div>
  )
}

// ─── Modal 狀態類型 ───────────────────────────────────────────────────────
type ModalState =
  | { type: 'create_top' }
  | { type: 'create_child'; parent: DepartmentTreeNode }
  | { type: 'edit'; target: DepartmentTreeNode }
  | { type: 'deactivate'; target: DepartmentTreeNode }
  | null

// ─── 主頁面 ──────────────────────────────────────────────────────────────
export default function OrganizationPage() {
  const { data: session, status } = useSession()
  const router = useRouter()
  const [tree, setTree] = useState<DepartmentTreeNode[]>([])
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState<string | null>(null)
  const [modal, setModal] = useState<ModalState>(null)
  const [actionError, setActionError] = useState<string | null>(null)

  useEffect(() => {
    if (status === 'unauthenticated') router.push('/auth/signin')
  }, [status, router])

  useEffect(() => {
    if (status === 'authenticated') fetchTree()
  }, [status])

  const fetchTree = async () => {
    try {
      setLoading(true)
      setError(null)
      const data = await apiClient.get<DepartmentTreeNode[]>('/departments/tree')
      setTree(data)
    } catch {
      setError('無法載入組織架構')
    } finally {
      setLoading(false)
    }
  }

  const handleDeactivate = async (dept: DepartmentTreeNode) => {
    setActionError(null)
    try {
      await apiClient.delete(`/departments/${dept.id}`)
      setModal(null)
      fetchTree()
    } catch (err: unknown) {
      const msg = err instanceof Error ? err.message : '停用失敗'
      setActionError(msg)
      setModal(null)
    }
  }

  if (status === 'loading' || loading) {
    return (
      <div className="flex items-center justify-center min-h-screen">
        <div className="text-lg text-gray-500">載入中...</div>
      </div>
    )
  }

  if (!session) return null

  const domains = tree
    .filter((n) => n.is_top_level && n.email_domain)
    .map((n) => ({ domain: n.email_domain!, name: n.name }))

  return (
    <div className="container mx-auto px-4 py-8">
      {/* 頁首 */}
      <div className="flex items-center justify-between mb-8">
        <div>
          <h1 className="text-3xl font-bold text-gray-900">組織架構</h1>
          <p className="mt-1 text-gray-600">維護公司部門樹狀結構</p>
        </div>
        <button
          onClick={() => setModal({ type: 'create_top' })}
          className="px-4 py-2 text-sm text-white bg-blue-600 rounded-lg hover:bg-blue-700 flex items-center gap-2"
        >
          <span className="text-lg leading-none">+</span>
          新增第一層部門
        </button>
      </div>

      {error && (
        <div className="mb-6 p-4 bg-red-50 border border-red-200 rounded-lg text-red-700">{error}</div>
      )}
      {actionError && (
        <div className="mb-6 p-4 bg-red-50 border border-red-200 rounded-lg text-red-700">{actionError}</div>
      )}

      {/* 樹狀結構 */}
      <div className="bg-white shadow rounded-lg p-6 mb-6">
        <h2 className="text-xl font-semibold text-gray-900 mb-4">匠耘 Porsche World</h2>

        {tree.length === 0 ? (
          <div className="text-center py-12">
            <p className="text-gray-500 mb-4">尚未建立任何部門</p>
            <button
              onClick={() => setModal({ type: 'create_top' })}
              className="px-4 py-2 text-sm text-white bg-blue-600 rounded-lg hover:bg-blue-700"
            >
              建立第一個部門
            </button>
          </div>
        ) : (
          <div className="space-y-2">
            {tree.map((node) => (
              <DepartmentNode
                key={node.id}
                node={node}
                level={0}
                onAddChild={(parent) => setModal({ type: 'create_child', parent })}
                onEdit={(target) => setModal({ type: 'edit', target })}
                onDeactivate={(target) => setModal({ type: 'deactivate', target })}
              />
            ))}
          </div>
        )}
      </div>

      {/* 網域說明 */}
      {domains.length > 0 && (
        <div className="bg-blue-50 border border-blue-200 rounded-lg p-4">
          <h3 className="text-sm font-semibold text-blue-900 mb-2">網域配置說明</h3>
          <div className="text-sm text-blue-800 space-y-1">
            {domains.map(({ domain, name }) => (
              <p key={domain}>
                • <strong>{domain}</strong> — {name} 專用網域
              </p>
            ))}
          </div>
          <p className="text-xs text-blue-700 mt-2">員工信箱根據所屬第一層部門的網域設定自動產生</p>
        </div>
      )}

      {/* Modals */}
      {modal?.type === 'create_top' && (
        <DepartmentModal
          mode="create_top"
          onClose={() => setModal(null)}
          onSaved={fetchTree}
        />
      )}
      {modal?.type === 'create_child' && (
        <DepartmentModal
          mode="create_child"
          parentDept={modal.parent}
          onClose={() => setModal(null)}
          onSaved={fetchTree}
        />
      )}
      {modal?.type === 'edit' && (
        <DepartmentModal
          mode="edit"
          editTarget={modal.target}
          onClose={() => setModal(null)}
          onSaved={fetchTree}
        />
      )}
      {modal?.type === 'deactivate' && (
        <DeactivateModal
          dept={modal.target}
          onClose={() => setModal(null)}
          onConfirm={() => handleDeactivate(modal.target)}
        />
      )}
    </div>
  )
}