import { useState, useMemo } from 'react'
import { useQuery } from '@tanstack/react-query'
import { Calculator, Info, AlertCircle } from 'lucide-react'
import api from '../lib/api'
import Card from '../components/ui/Card'
import Button from '../components/ui/Button'
import { Input, Label, Select } from '../components/ui/Input'

// 金额格式化：保留两位小数 + 千分位
const fmt = (n: number) => (n || 0).toLocaleString('zh-CN', { minimumFractionDigits: 2, maximumFractionDigits: 2 })

interface EmployeeOption {
  id: string
  name: string
  department: string
  hireDate: string
  monthlySalary: number
  status: string
  contracts?: any[]
}

function useEmployees() {
  return useQuery<EmployeeOption[]>({
    queryKey: ['roster-for-compensation'],
    queryFn: async () => {
      const res = await api.get('/roster') as any
      return res.data
    },
  })
}

function EmployeeSelector({ employees, selectedId, onSelect }: {
  employees?: EmployeeOption[]
  selectedId: string
  onSelect: (emp: EmployeeOption | null) => void
}) {
  return (
    <div>
      <Label>选择员工（自动带出入职日期和工资）</Label>
      <Select value={selectedId} onChange={(e) => {
        const emp = employees?.find((x) => x.id === e.target.value)
        onSelect(emp || null)
      }}>
        <option value="">-- 手动输入 --</option>
        {employees?.map((emp) => (
          <option key={emp.id} value={emp.id}>
            {emp.name}（{emp.department}）
          </option>
        ))}
      </Select>
    </div>
  )
}

export default function Compensation() {
  const [tab, setTab] = useState<'severance' | 'double'>('severance')

  const tabs: { key: typeof tab; label: string }[] = [
    { key: 'severance', label: '经济补偿金' },
    { key: 'double', label: '双倍工资' },
  ]

  return (
    <div className="space-y-3">
      <h1 className="text-xs font-medium">补偿计算</h1>

      <div className="flex gap-1 border-b">
        {tabs.map((t) => (
          <button
            key={t.key}
            onClick={() => setTab(t.key)}
            className={`px-3 py-1.5 text-xs font-medium border-b-2 transition-colors ${
              tab === t.key ? 'border-primary text-primary' : 'border-transparent text-gray-500 hover:text-gray-700'
            }`}
          >
            {t.label}
          </button>
        ))}
      </div>

      {tab === 'severance' && <SeveranceCalculator />}
      {tab === 'double' && <DoubleSalaryCalculator />}
    </div>
  )
}

function SeveranceCalculator() {
  const { data: employees } = useEmployees()
  const [selectedEmpId, setSelectedEmpId] = useState('')
  const [hireDate, setHireDate] = useState('')
  const [leaveDate, setLeaveDate] = useState('')
  const [avgWage, setAvgWage] = useState(8000)
  const [reason, setReason] = useState('negotiated')
  const [socialAvgWage, setSocialAvgWage] = useState(0)
  const [result, setResult] = useState<any>(null)

  const handleSelectEmp = (emp: EmployeeOption | null) => {
    setSelectedEmpId(emp?.id || '')
    if (emp) {
      setHireDate(emp.hireDate?.toString().slice(0, 10) || '')
      setAvgWage(emp.monthlySalary || 8000)
    }
  }

  const reasonMap: Record<string, { label: string; multiplier: number; extra: string; illegal: boolean }> = {
    negotiated: { label: '协商一致解除', multiplier: 1, extra: '', illegal: false },
    fault: { label: '员工过错解除', multiplier: 0, extra: '员工过错解除，无需支付经济补偿金', illegal: false },
    nonfault: { label: '非过错解除', multiplier: 1, extra: '额外支付1个月代通知金', illegal: false },
    layoff: { label: '经济性裁员', multiplier: 1, extra: '', illegal: false },
    expired: { label: '合同到期不续签', multiplier: 1, extra: '用人单位不续签或降低条件续签', illegal: false },
    illegal: { label: '违法解除', multiplier: 2, extra: '违法解除劳动合同，按经济补偿金的2倍支付赔偿金（《劳动合同法》第87条）', illegal: true },
  }

  const handleCalculate = () => {
    if (!hireDate || !leaveDate) return
    const hire = new Date(hireDate)
    const leave = new Date(leaveDate)
    const totalMonths = (leave.getFullYear() - hire.getFullYear()) * 12 + (leave.getMonth() - hire.getMonth())
    const years = Math.floor(totalMonths / 12)
    const remainingMonths = totalMonths % 12

    let compMonths: number
    if (remainingMonths >= 6) compMonths = years + 1
    else if (remainingMonths > 0) compMonths = years + 0.5
    else compMonths = years

    if (compMonths <= 0) compMonths = 0.5

    let wage = avgWage
    let capped = false
    if (socialAvgWage > 0 && avgWage > socialAvgWage * 3) {
      wage = socialAvgWage * 3
      compMonths = Math.min(compMonths, 12)
      capped = true
    }

    const r = reasonMap[reason]
    const basePay = wage * compMonths
    let totalPay = basePay * r.multiplier
    let noticePay = 0
    if (reason === 'nonfault') {
      noticePay = wage
      totalPay += noticePay
    }

    setResult({ years, remainingMonths, compMonths, wage, totalPay, basePay, totalMonths, capped, reason: r.label, reasonNote: r.extra, noticePay, noComp: r.multiplier === 0, isIllegal: r.illegal })
  }

  return (
    <div className="grid md:grid-cols-2 gap-4">
      <Card>
        <h2 className="font-medium mb-4">填写信息</h2>
        <div className="space-y-3">
          <EmployeeSelector employees={employees} selectedId={selectedEmpId} onSelect={handleSelectEmp} />
          <div>
            <Label>入职日期</Label>
            <Input type="date" value={hireDate} onChange={(e) => setHireDate(e.target.value)} />
          </div>
          <div>
            <Label>离职日期</Label>
            <Input type="date" value={leaveDate} onChange={(e) => setLeaveDate(e.target.value)} />
          </div>
          <div>
            <Label>月平均工资（元）</Label>
            <Input type="number" value={avgWage} onChange={(e) => setAvgWage(Number(e.target.value) || 0)} />
          </div>
          <div>
            <Label>离职原因</Label>
            <Select value={reason} onChange={(e) => setReason(e.target.value)}>
              <option value="negotiated">协商一致解除</option>
              <option value="fault">员工过错解除</option>
              <option value="nonfault">非过错解除（额外1个月代通知金）</option>
              <option value="layoff">经济性裁员</option>
              <option value="expired">合同到期不续签</option>
              <option value="illegal">违法解除（赔偿金×2）</option>
            </Select>
          </div>
          <div>
            <Label>当地社平工资（选填）</Label>
            <Input type="number" value={socialAvgWage} onChange={(e) => setSocialAvgWage(Number(e.target.value) || 0)} placeholder="用于三倍封顶计算" />
          </div>
          <Button onClick={handleCalculate} disabled={!hireDate || !leaveDate} className="w-full">
            <Calculator className="w-4 h-4 mr-1" /> 计算
          </Button>
        </div>
      </Card>

      <Card>
        <h2 className="font-medium mb-4 flex items-center gap-2"><Calculator className="w-5 h-5" />计算结果</h2>
        {result ? (
          <div className="space-y-3">
            <div className="text-xs text-gray-500">离职原因：<span className="text-gray-900">{result.reason}</span></div>
            <div className="text-xs text-gray-500">工作年限：<span className="text-gray-900">{result.years}年{result.remainingMonths}个月</span></div>
            {result.noComp ? (
              <div className="px-3 py-2 rounded-md bg-gray-50 text-gray-700 text-xs">
                {result.reasonNote}
              </div>
            ) : (
              <>
                <div className="text-xs text-gray-500">补偿月数：<span className="text-gray-900">{result.compMonths}个月</span></div>
                {result.capped && (
                  <div className="text-xs text-warning">⚠️ 工资超过社平3倍，已按三倍封顶且最多补偿12个月</div>
                )}
                <div className="text-xs text-gray-500">计算基数：<span className="text-gray-900">¥{fmt(result.wage)}/月</span></div>
                <div className="border-t pt-3 space-y-2">
                  <div className="flex items-center justify-between">
                    <span className="font-medium">{result.isIllegal ? '经济补偿金' : '应付金额'}</span>
                    <span className="font-medium">¥{fmt(result.basePay)}</span>
                  </div>
                  {result.isIllegal ? (
                    <>
                      <div className="flex items-center justify-between">
                        <span className="font-medium text-danger">违法解除赔偿金（×2）</span>
                        <span className="text-lg font-bold text-danger">¥{fmt(result.totalPay)}</span>
                      </div>
                      <div className="text-xs text-gray-400">（{result.compMonths}个月 × ¥{fmt(result.wage)} × 2）</div>
                    </>
                  ) : (
                    <>
                      <div className="flex items-center justify-between">
                        <span className="font-medium">{result.reason}</span>
                        <span className="text-lg font-bold text-primary">¥{fmt(result.totalPay)}</span>
                      </div>
                      <div className="text-xs text-gray-400">（{result.compMonths}个月 × ¥{fmt(result.wage)})
                        {result.noticePay > 0 && <span className="block">含代通知金 ¥{fmt(result.noticePay)}</span>}
                      </div>
                    </>
                  )}
                </div>
                {result.reasonNote && (
                  <div className={`flex items-start gap-2 px-3 py-2 rounded-md text-xs ${result.isIllegal ? 'bg-red-50 text-red-700' : 'bg-blue-50 text-blue-700'}`}>
                    <Info className="w-4 h-4 mt-0.5 shrink-0" />
                    <span>{result.reasonNote}</span>
                  </div>
                )}
                <div className="flex items-start gap-2 px-3 py-2 rounded-md bg-blue-50 text-blue-700 text-xs">
                  <Info className="w-4 h-4 mt-0.5 shrink-0" />
                  <span>满1年补1个月，满6个月不满1年按1年算，不满6个月补半个月</span>
                </div>
              </>
            )}
          </div>
        ) : (
          <div className="text-gray-400 text-xs">填写信息后点击「计算」按钮</div>
        )}
      </Card>
    </div>
  )
}

function DoubleSalaryCalculator() {
  const { data: employees } = useEmployees()
  const [selectedEmpId, setSelectedEmpId] = useState('')
  const [monthlyWage, setMonthlyWage] = useState(8000)
  const [hireDate, setHireDate] = useState('')
  const [hasContract, setHasContract] = useState(false)
  const [contractDate, setContractDate] = useState('')

  const handleSelectEmp = (emp: EmployeeOption | null) => {
    setSelectedEmpId(emp?.id || '')
    if (emp) {
      setHireDate(emp.hireDate?.toString().slice(0, 10) || '')
      setMonthlyWage(emp.monthlySalary || 8000)
      const latestContract = emp.contracts?.find((c: any) => c.signDate)
      if (latestContract) {
        setHasContract(true)
        setContractDate(latestContract.signDate?.toString().slice(0, 10) || '')
      } else {
        setHasContract(false)
        setContractDate('')
      }
    }
  }

  const result = useMemo(() => {
    if (!hireDate) return null
    const hire = new Date(hireDate)
    const startDate = new Date(hire)
    startDate.setMonth(startDate.getMonth() + 1)
    startDate.setDate(startDate.getDate() + 1)

    let endDate = new Date(hire)
    endDate.setFullYear(endDate.getFullYear() + 1)

    if (hasContract && contractDate) {
      const contract = new Date(contractDate)
      const daysDiff = Math.floor((contract.getTime() - hire.getTime()) / (1000 * 60 * 60 * 24))
      if (daysDiff > 30) {
        endDate = contract
      }
    }

    const months = Math.min(
      Math.floor((endDate.getTime() - startDate.getTime()) / (1000 * 60 * 60 * 24 * 30.44)),
      11,
    )
    const totalPay = monthlyWage * Math.max(months, 0)

    return { startDate, endDate, months: Math.max(months, 0), totalPay }
  }, [monthlyWage, hireDate, hasContract, contractDate])

  return (
    <div className="grid md:grid-cols-2 gap-4">
      <Card>
        <h2 className="font-medium mb-4">填写信息</h2>
        <div className="space-y-3">
          <EmployeeSelector employees={employees} selectedId={selectedEmpId} onSelect={handleSelectEmp} />
          <div>
            <Label>月工资（元）</Label>
            <Input type="number" value={monthlyWage} onChange={(e) => setMonthlyWage(Number(e.target.value) || 0)} />
          </div>
          <div>
            <Label>入职日期</Label>
            <Input type="date" value={hireDate} onChange={(e) => setHireDate(e.target.value)} />
          </div>
          <div>
            <Label>合同签订情况</Label>
            <Select value={hasContract ? 'yes' : 'no'} onChange={(e) => setHasContract(e.target.value === 'yes')}>
              <option value="no">未签订</option>
              <option value="yes">已签订</option>
            </Select>
          </div>
          {hasContract && (
            <div>
              <Label>合同签订日期</Label>
              <Input type="date" value={contractDate} onChange={(e) => setContractDate(e.target.value)} />
            </div>
          )}
        </div>
      </Card>

      <Card>
        <h2 className="font-medium mb-4 flex items-center gap-2"><AlertCircle className="w-5 h-5 text-warning" />计算结果</h2>
        {result ? (
          <div className="space-y-3">
            <div className="text-xs text-gray-500">入职日期：<span className="text-gray-900">{hireDate}</span></div>
            <div className="text-xs text-gray-500">合同签订：<span className="text-gray-900">{hasContract ? contractDate || '未填写' : '未签订'}</span></div>
            <div className="text-xs text-gray-500">双倍工资起算：<span className="text-gray-900">{result.startDate.toISOString().slice(0, 10)}</span></div>
            <div className="text-xs text-gray-500">双倍工资截止：<span className="text-gray-900">{result.endDate.toISOString().slice(0, 10)}</span></div>
            <div className="border-t pt-3">
              <div className="flex items-center justify-between">
                <span className="font-medium">需赔</span>
                <span className="text-lg font-bold text-danger">¥{fmt(result.totalPay)}</span>
              </div>
              <div className="text-xs text-gray-400 mt-1">（{result.months}个月 × ¥{fmt(monthlyWage)}）</div>
            </div>
            <div className="flex items-start gap-2 px-3 py-2 rounded-md bg-blue-50 text-blue-700 text-xs">
              <Info className="w-4 h-4 mt-0.5 shrink-0" />
              <span>法律规定：入职1个月没签合同，从第2个月起要付双倍工资，最多11个月</span>
            </div>
          </div>
        ) : (
          <div className="text-gray-400 text-xs">请填写入职日期</div>
        )}
      </Card>
    </div>
  )
}
