import { useMemo, useState, type FormEvent } from 'react'
import { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
import { GitBranch, Plus, Trash2, CheckCircle2, Info, History } from 'lucide-react'
import { toast } from 'sonner'
import { PageHeader } from '@/components/PageHeader'
import { Button } from '@/components/ui/Button'
import { Dialog } from '@/components/ui/Dialog'
import { Input } from '@/components/ui/Input'
import { Label } from '@/components/ui/Label'
import { Select } from '@/components/ui/Select'
import { Textarea } from '@/components/ui/Textarea'
import { api } from '@/lib/api'
import { getErrorMessage } from '@/lib/apiError'
import { AVAILABLE_ROLES, RoleLabel } from '@/types/users'

// ===== Types =====

type ApproverDto = { kind: number; assignmentValue: string; displayName: string | null }
type StepDto = { id: string; order: number; phase: number; phaseLabel: string; name: string; slaDays: number | null; approvers: ApproverDto[] }
type DefinitionDto = {
  id: string
  code: string
  version: number
  contractType: number
  contractTypeLabel: string
  name: string
  description: string | null
  isActive: boolean
  activatedAt: string | null
  createdAt: string
  contractsUsingCount: number
  steps: StepDto[]
}
type TypeSummaryDto = {
  contractType: number
  contractTypeLabel: string
  active: DefinitionDto | null
  history: DefinitionDto[]
}

const PHASE_OPTIONS: { value: number; label: string }[] = [
  { value: 2, label: 'Đang soạn thảo' },
  { value: 3, label: 'Đang góp ý' },
  { value: 4, label: 'Đang đàm phán' },
  { value: 5, label: 'Đang in ký' },
  { value: 6, label: 'CCM kiểm tra' },
  { value: 7, label: 'Đang trình ký' },
  { value: 8, label: 'Đang đóng dấu' },
  { value: 9, label: 'Đã phát hành' },
]

type EditStepApprover = { kind: 1 | 2; assignmentValue: string }
type EditStep = { phase: number; name: string; slaDays: number | null; approvers: EditStepApprover[] }

function copyFromDefinition(d: DefinitionDto): EditStep[] {
  return d.steps.map(s => ({
    phase: s.phase,
    name: s.name,
    slaDays: s.slaDays,
    approvers: s.approvers.map(a => ({ kind: a.kind as 1 | 2, assignmentValue: a.assignmentValue })),
  }))
}

// ===== Page =====

export function WorkflowsPage() {
  const qc = useQueryClient()
  const overview = useQuery({
    queryKey: ['workflow-overview'],
    queryFn: async () => (await api.get<{ types: TypeSummaryDto[] }>('/workflows')).data,
  })

  const [activeType, setActiveType] = useState<number | null>(null)
  const tab = activeType ?? overview.data?.types[0]?.contractType ?? 1
  const currentType = overview.data?.types.find(t => t.contractType === tab)

  return (
    <div className="p-6">
      <PageHeader
        title={
          <span className="flex items-center gap-2">
            <GitBranch className="h-5 w-5" />
            Quy trình duyệt hợp đồng
          </span>
        }
        description="Mỗi loại HĐ có quy trình riêng, hỗ trợ versioning. Tạo version mới → HĐ tương lai chạy theo. HĐ cũ vẫn giữ quy trình cũ."
      />

      {/* Tabs */}
      {overview.data && (
        <div className="mb-5 flex gap-1 overflow-x-auto border-b border-slate-200">
          {overview.data.types.map(t => (
            <button
              key={t.contractType}
              onClick={() => setActiveType(t.contractType)}
              className={`shrink-0 border-b-2 px-4 py-2 text-sm font-medium transition ${
                tab === t.contractType
                  ? 'border-brand-600 text-brand-700'
                  : 'border-transparent text-slate-500 hover:text-slate-800'
              }`}
            >
              {t.contractTypeLabel}
              {t.active && (
                <span className="ml-2 rounded bg-brand-50 px-1.5 py-0.5 font-mono text-[10px] text-brand-700">
                  v{String(t.active.version).padStart(2, '0')}
                </span>
              )}
            </button>
          ))}
        </div>
      )}

      {overview.isLoading && <div className="text-sm text-slate-500">Đang tải…</div>}

      {currentType && <TypePanel type={currentType} onSaved={() => qc.invalidateQueries({ queryKey: ['workflow-overview'] })} />}
    </div>
  )
}

// ===== Per-type panel =====

function TypePanel({ type, onSaved }: { type: TypeSummaryDto; onSaved: () => void }) {
  const [designerOpen, setDesignerOpen] = useState(false)
  const [cloneFrom, setCloneFrom] = useState<DefinitionDto | null>(null)

  return (
    <div className="space-y-4">
      {type.active ? (
        <DefinitionCard def={type.active} isActive onClone={d => { setCloneFrom(d); setDesignerOpen(true) }} />
      ) : (
        <div className="rounded-xl border border-dashed border-slate-300 p-8 text-center text-sm text-slate-500">
          Chưa có quy trình cho loại này. Tạo version đầu tiên bên dưới.
        </div>
      )}

      <div className="flex items-center justify-between">
        <h3 className="text-sm font-semibold text-slate-700">Lịch sử versions</h3>
        <Button onClick={() => { setCloneFrom(type.active); setDesignerOpen(true) }}>
          <Plus className="h-4 w-4" />
          Tạo quy trình mới
        </Button>
      </div>

      {type.history.filter(d => !d.isActive).length === 0 && (
        <div className="rounded-md border border-slate-200 bg-slate-50 p-4 text-xs text-slate-500">
          Chưa có version cũ. Khi tạo version mới, version hiện tại tự động archive.
        </div>
      )}

      <div className="space-y-2">
        {type.history
          .filter(d => !d.isActive)
          .map(d => (
            <DefinitionCard key={d.id} def={d} isActive={false} onClone={dd => { setCloneFrom(dd); setDesignerOpen(true) }} />
          ))}
      </div>

      {designerOpen && (
        <WorkflowDesigner
          contractType={type.contractType}
          contractTypeLabel={type.contractTypeLabel}
          cloneFrom={cloneFrom}
          onClose={() => { setDesignerOpen(false); setCloneFrom(null) }}
          onSaved={() => { setDesignerOpen(false); setCloneFrom(null); onSaved() }}
        />
      )}
    </div>
  )
}

// ===== Definition card (read-only view) =====

function DefinitionCard({ def, isActive, onClone }: { def: DefinitionDto; isActive: boolean; onClone: (d: DefinitionDto) => void }) {
  return (
    <div className={`rounded-xl border bg-white p-5 shadow-sm ${isActive ? 'border-brand-200' : 'border-slate-200'}`}>
      <div className="flex items-start justify-between gap-4">
        <div className="min-w-0 flex-1">
          <div className="flex items-center gap-2">
            <h3 className="text-[15px] font-semibold text-slate-900">
              {def.name}
            </h3>
            <span className="rounded bg-slate-100 px-2 py-0.5 font-mono text-[11px] text-slate-600">
              {def.code} v{String(def.version).padStart(2, '0')}
            </span>
            {isActive ? (
              <span className="inline-flex items-center gap-1 rounded-full bg-emerald-100 px-2 py-0.5 text-[10px] font-medium text-emerald-700">
                <CheckCircle2 className="h-3 w-3" />
                Đang áp dụng
              </span>
            ) : (
              <span className="inline-flex items-center gap-1 rounded-full bg-slate-100 px-2 py-0.5 text-[10px] font-medium text-slate-600">
                <History className="h-3 w-3" />
                Archived · {def.contractsUsingCount} HĐ còn chạy
              </span>
            )}
          </div>
          {def.description && <p className="mt-1 text-xs leading-relaxed text-slate-500">{def.description}</p>}

          <ol className="mt-3 space-y-2">
            {def.steps.map(s => (
              <li key={s.id} className="flex items-start gap-3 rounded-lg border border-slate-100 bg-slate-50/30 p-2.5">
                <div className="flex h-7 w-7 shrink-0 items-center justify-center rounded-full bg-brand-600 text-[11px] font-bold text-white">
                  {s.order}
                </div>
                <div className="min-w-0 flex-1">
                  <div className="flex items-center gap-2 text-sm">
                    <span className="font-medium text-slate-800">{s.name}</span>
                    <span className="text-[11px] text-slate-400">({s.phaseLabel})</span>
                    {s.slaDays != null && (
                      <span className="rounded bg-amber-100 px-1.5 py-0.5 text-[10px] font-medium text-amber-700">
                        SLA {s.slaDays}d
                      </span>
                    )}
                  </div>
                  <div className="mt-1 flex flex-wrap gap-1">
                    {s.approvers.length === 0 && (
                      <span className="text-[11px] italic text-slate-400">Chưa có người duyệt</span>
                    )}
                    {s.approvers.map((a, i) => (
                      <span
                        key={i}
                        className={`rounded-full px-2 py-0.5 text-[10px] font-medium ${
                          a.kind === 1 ? 'bg-brand-50 text-brand-700' : 'bg-violet-50 text-violet-700'
                        }`}
                      >
                        {a.kind === 1 ? 'Role' : 'User'}: {a.displayName ?? a.assignmentValue}
                      </span>
                    ))}
                  </div>
                </div>
              </li>
            ))}
          </ol>
        </div>
        <Button variant="outline" size="sm" onClick={() => onClone(def)}>
          <Plus className="h-3.5 w-3.5" />
          Tạo từ bản này
        </Button>
      </div>
    </div>
  )
}

// ===== Designer dialog =====

function WorkflowDesigner({
  contractType,
  contractTypeLabel,
  cloneFrom,
  onClose,
  onSaved,
}: {
  contractType: number
  contractTypeLabel: string
  cloneFrom: DefinitionDto | null
  onClose: () => void
  onSaved: () => void
}) {
  const initialSteps: EditStep[] = useMemo(
    () =>
      cloneFrom
        ? copyFromDefinition(cloneFrom)
        : [{ phase: 2, name: 'Soạn thảo', slaDays: 7, approvers: [] }],
    [cloneFrom],
  )

  const [code, setCode] = useState(cloneFrom?.code ?? 'QT-NEW')
  const [name, setName] = useState(cloneFrom ? `${cloneFrom.name} (clone)` : `Quy trình ${contractTypeLabel}`)
  const [description, setDescription] = useState(cloneFrom?.description ?? '')
  const [steps, setSteps] = useState<EditStep[]>(initialSteps)

  const usersList = useQuery({
    queryKey: ['users-for-approver'],
    queryFn: async () =>
      (await api.get<{ items: { id: string; fullName: string; email: string }[] }>('/users', { params: { page: 1, pageSize: 200 } })).data.items,
  })

  const save = useMutation({
    mutationFn: async () => {
      await api.post('/workflows', {
        contractType,
        code,
        name,
        description: description || null,
        steps: steps.map((s, i) => ({
          order: i + 1,
          phase: s.phase,
          name: s.name,
          slaDays: s.slaDays,
          approvers: s.approvers,
        })),
      })
    },
    onSuccess: () => {
      toast.success('Đã lưu quy trình mới. Version cũ đã archive.')
      onSaved()
    },
    onError: err => toast.error(getErrorMessage(err)),
  })

  function submit(e: FormEvent) {
    e.preventDefault()
    if (steps.length === 0) {
      toast.error('Phải có ít nhất 1 bước')
      return
    }
    save.mutate()
  }

  return (
    <Dialog
      open
      onClose={onClose}
      title={`Tạo quy trình mới — ${contractTypeLabel}`}
      size="xl"
      footer={
        <>
          <Button variant="outline" onClick={onClose}>Hủy</Button>
          <Button onClick={submit} disabled={save.isPending} form="wf-form">
            {save.isPending ? 'Đang lưu…' : 'Lưu + kích hoạt'}
          </Button>
        </>
      }
    >
      <form id="wf-form" onSubmit={submit} className="space-y-4">
        <div className="grid grid-cols-2 gap-3">
          <div className="space-y-1.5">
            <Label>Mã quy trình *</Label>
            <Input value={code} onChange={e => setCode(e.target.value)} required className="font-mono" />
            <div className="text-[11px] text-slate-400">Ví dụ QT-TP, QT-MB. Version auto-tăng mỗi lần lưu.</div>
          </div>
          <div className="space-y-1.5">
            <Label>Tên hiển thị *</Label>
            <Input value={name} onChange={e => setName(e.target.value)} required />
          </div>
          <div className="col-span-2 space-y-1.5">
            <Label>Mô tả</Label>
            <Textarea rows={2} value={description} onChange={e => setDescription(e.target.value)} />
          </div>
        </div>

        <div className="space-y-2 rounded-lg border border-slate-200 p-3">
          <div className="flex items-center justify-between">
            <Label>Các bước ({steps.length})</Label>
            <Button
              type="button"
              size="sm"
              variant="outline"
              onClick={() =>
                setSteps([...steps, { phase: 3, name: '', slaDays: 7, approvers: [] }])
              }
            >
              <Plus className="h-3.5 w-3.5" />
              Thêm bước
            </Button>
          </div>

          {steps.map((s, idx) => (
            <div key={idx} className="rounded-md border border-slate-200 bg-slate-50/40 p-3">
              <div className="flex items-start gap-2">
                <div className="flex h-7 w-7 shrink-0 items-center justify-center rounded-full bg-brand-600 text-[11px] font-bold text-white">
                  {idx + 1}
                </div>
                <div className="grid flex-1 grid-cols-3 gap-2">
                  <div>
                    <Label className="text-[11px]">Phase</Label>
                    <Select
                      value={s.phase}
                      onChange={e => setSteps(steps.map((x, i) => (i === idx ? { ...x, phase: Number(e.target.value) } : x)))}
                    >
                      {PHASE_OPTIONS.map(p => (
                        <option key={p.value} value={p.value}>{p.label}</option>
                      ))}
                    </Select>
                  </div>
                  <div>
                    <Label className="text-[11px]">Tên bước</Label>
                    <Input value={s.name} onChange={e => setSteps(steps.map((x, i) => (i === idx ? { ...x, name: e.target.value } : x)))} />
                  </div>
                  <div>
                    <Label className="text-[11px]">SLA (ngày)</Label>
                    <Input
                      type="number"
                      min={0}
                      value={s.slaDays ?? ''}
                      onChange={e =>
                        setSteps(steps.map((x, i) => (i === idx ? { ...x, slaDays: e.target.value ? Number(e.target.value) : null } : x)))
                      }
                    />
                  </div>
                </div>
                <button
                  type="button"
                  onClick={() => setSteps(steps.filter((_, i) => i !== idx))}
                  className="flex h-7 w-7 items-center justify-center rounded text-slate-400 hover:bg-red-50 hover:text-red-600"
                  title="Xóa bước"
                >
                  <Trash2 className="h-3.5 w-3.5" />
                </button>
              </div>

              <div className="mt-2 border-t border-slate-200 pt-2">
                <div className="mb-1 flex items-center justify-between">
                  <Label className="text-[11px]">Người duyệt</Label>
                  <div className="flex gap-1">
                    <button
                      type="button"
                      onClick={() => setSteps(steps.map((x, i) => (i === idx ? { ...x, approvers: [...x.approvers, { kind: 1, assignmentValue: AVAILABLE_ROLES[1] }] } : x)))}
                      className="rounded bg-brand-50 px-2 py-0.5 text-[11px] font-medium text-brand-700 hover:bg-brand-100"
                    >
                      + Role
                    </button>
                    <button
                      type="button"
                      onClick={() => setSteps(steps.map((x, i) => (i === idx ? { ...x, approvers: [...x.approvers, { kind: 2, assignmentValue: usersList.data?.[0]?.id ?? '' }] } : x)))}
                      className="rounded bg-violet-50 px-2 py-0.5 text-[11px] font-medium text-violet-700 hover:bg-violet-100"
                    >
                      + User
                    </button>
                  </div>
                </div>
                {s.approvers.length === 0 && (
                  <div className="rounded bg-slate-100 px-2 py-1.5 text-[11px] italic text-slate-500">
                    Chưa có người duyệt — tối thiểu nên có 1 Role hoặc 1 User.
                  </div>
                )}
                <div className="space-y-1">
                  {s.approvers.map((a, ai) => (
                    <div key={ai} className="flex items-center gap-1">
                      {a.kind === 1 ? (
                        <Select
                          value={a.assignmentValue}
                          onChange={e =>
                            setSteps(steps.map((x, i) =>
                              i === idx ? { ...x, approvers: x.approvers.map((y, j) => (j === ai ? { ...y, assignmentValue: e.target.value } : y)) } : x,
                            ))
                          }
                          className="h-7 flex-1 text-xs"
                        >
                          {AVAILABLE_ROLES.map(r => (
                            <option key={r} value={r}>Role: {RoleLabel[r] ?? r}</option>
                          ))}
                        </Select>
                      ) : (
                        <Select
                          value={a.assignmentValue}
                          onChange={e =>
                            setSteps(steps.map((x, i) =>
                              i === idx ? { ...x, approvers: x.approvers.map((y, j) => (j === ai ? { ...y, assignmentValue: e.target.value } : y)) } : x,
                            ))
                          }
                          className="h-7 flex-1 text-xs"
                        >
                          {usersList.data?.map(u => (
                            <option key={u.id} value={u.id}>User: {u.fullName} ({u.email})</option>
                          ))}
                        </Select>
                      )}
                      <button
                        type="button"
                        onClick={() =>
                          setSteps(steps.map((x, i) =>
                            i === idx ? { ...x, approvers: x.approvers.filter((_, j) => j !== ai) } : x,
                          ))
                        }
                        className="flex h-6 w-6 items-center justify-center rounded text-slate-400 hover:bg-red-50 hover:text-red-600"
                      >
                        <Trash2 className="h-3 w-3" />
                      </button>
                    </div>
                  ))}
                </div>
              </div>
            </div>
          ))}
        </div>

        <div className="flex items-start gap-2 rounded-md border border-amber-200 bg-amber-50 px-3 py-2 text-xs text-amber-800">
          <Info className="mt-0.5 h-3.5 w-3.5 shrink-0" />
          <div>
            Khi lưu: version mới tự động tăng từ <code className="font-mono">{code}</code>, thành version đang áp dụng.
            HĐ hiện tại vẫn giữ version cũ (được pin tại thời điểm tạo), chỉ HĐ MỚI đi theo version này.
          </div>
        </div>
      </form>
    </Dialog>
  )
}