import { useState } from 'react'
import { useNavigate } from 'react-router-dom'
import { useQuery } from '@tanstack/react-query'
import { executionsApi } from '../api/workflows'
import { useExecutionListUpdates } from '../hooks/useExecutionListUpdates'
import { formatDistanceToNow } from 'date-fns'
import { CheckCircle, XCircle, Clock, Ban, RefreshCw, ChevronLeft, ChevronRight, AlertCircle, Octagon } from 'lucide-react'
import clsx from 'clsx'

// Helper to safely format timestamps that might be invalid or too large
function safeFormatDistanceToNow(timestamp: number): string {
  if (!timestamp || timestamp < 0 || timestamp > 8640000000000000) {
    return 'unknown'
  }
  try {
    return formatDistanceToNow(timestamp, { addSuffix: true })
  } catch {
    return 'unknown'
  }
}

const PAGE_SIZE = 20

export default function ExecutionsPage() {
  const navigate = useNavigate()
  const [page, setPage] = useState(1)

  // The workflow editor already renders an execution across the canvas with each
  // node's input and output, so open it there rather than building a second
  // viewer that would show less.
  const openExecution = (execution: { id: string; workflowId: string }) => {
    if (!execution.workflowId) {
      return
    }
    navigate(`/workflows/${execution.workflowId}?execution=${encodeURIComponent(execution.id)}`)
  }

  const { data, isLoading, refetch } = useQuery({
    queryKey: ['executions', page],
    queryFn: () => executionsApi.list(undefined, undefined, page, PAGE_SIZE),
  })

  // Subscribe to WebSocket for real-time updates instead of polling
  useExecutionListUpdates()

  const executions = data?.executions || []
  const total = data?.total || 0
  const totalPages = Math.ceil(total / PAGE_SIZE)
  const hasMore = data?.hasMore || false

  const getStatusIcon = (status: string) => {
    switch (status) {
      case 'completed':
        return <CheckCircle className="w-5 h-5 text-green-500" />
      case 'failed':
        return <XCircle className="w-5 h-5 text-red-500" />
      case 'running':
        return <RefreshCw className="w-5 h-5 text-blue-500 animate-spin" />
      case 'cancelled':
        return <Ban className="w-5 h-5 text-gray-500" />
      default:
        return <Clock className="w-5 h-5 text-gray-400" />
    }
  }

  const getStatusBadgeClass = (status: string) => {
    switch (status) {
      case 'completed':
        return 'bg-green-100 dark:bg-green-900/30 text-green-700 dark:text-green-400'
      case 'failed':
        return 'bg-red-100 dark:bg-red-900/30 text-red-700 dark:text-red-400'
      case 'running':
        return 'bg-blue-100 dark:bg-blue-900/30 text-blue-700 dark:text-blue-400'
      case 'cancelled':
        return 'bg-gray-100 dark:bg-slate-700 text-gray-700 dark:text-gray-400'
      default:
        return 'bg-gray-100 dark:bg-slate-700 text-gray-600 dark:text-gray-400'
    }
  }

  return (
    <div className="h-full overflow-auto p-6">
      <div className="flex items-center justify-between mb-6">
        <h1 className="text-2xl font-bold text-gray-900 dark:text-gray-100">Executions</h1>
        <button
          onClick={() => refetch()}
          className="flex items-center gap-2 px-3 py-1.5 text-gray-600 dark:text-gray-400 hover:bg-gray-100 dark:hover:bg-slate-700 rounded-lg"
        >
          <RefreshCw className="w-4 h-4" />
          Refresh
        </button>
      </div>

      {isLoading ? (
        <div className="flex items-center justify-center py-12">
          <div className="animate-spin rounded-full h-8 w-8 border-b-2 border-primary-600"></div>
        </div>
      ) : executions.length === 0 ? (
        <div className="text-center py-12 bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-slate-700">
          <p className="text-gray-500 dark:text-gray-400">No executions yet</p>
        </div>
      ) : (
        <>
          <div className="bg-white dark:bg-slate-800 rounded-xl border border-gray-200 dark:border-slate-700 overflow-hidden">
            <table className="w-full">
              <thead className="bg-gray-50 dark:bg-slate-700 border-b border-gray-200 dark:border-slate-600">
                <tr>
                  <th className="px-4 py-3 text-left text-sm font-medium text-gray-600 dark:text-gray-300">
                    Status
                  </th>
                  <th className="px-4 py-3 text-left text-sm font-medium text-gray-600 dark:text-gray-300">
                    Workflow
                  </th>
                  <th className="px-4 py-3 text-left text-sm font-medium text-gray-600 dark:text-gray-300">
                    Trigger
                  </th>
                  <th className="px-4 py-3 text-left text-sm font-medium text-gray-600 dark:text-gray-300">
                    Runner
                  </th>
                  <th className="px-4 py-3 text-left text-sm font-medium text-gray-600 dark:text-gray-300">
                    Started
                  </th>
                  <th className="px-4 py-3 text-left text-sm font-medium text-gray-600 dark:text-gray-300">
                    Duration
                  </th>
                </tr>
              </thead>
              <tbody className="divide-y divide-gray-200 dark:divide-slate-700">
                {executions.map((execution: any) => (
                  <tr
                    key={execution.id}
                    onClick={() => openExecution(execution)}
                    title="Open this execution in the workflow editor"
                    className="hover:bg-gray-50 dark:hover:bg-slate-700/50 cursor-pointer"
                  >
                    <td className="px-4 py-3 align-top">
                      <div className="flex items-center gap-2">
                        {getStatusIcon(execution.status)}
                        <span
                          className={clsx(
                            'px-2 py-0.5 rounded-full text-xs font-medium',
                            getStatusBadgeClass(execution.status)
                          )}
                        >
                          {execution.status}
                        </span>
                      </div>
                    </td>
                    <td className="px-4 py-3 align-top">
                      <span className="font-medium text-gray-900 dark:text-gray-100">
                        {execution.workflowName || execution.workflowId}
                      </span>
                      {execution.error && (
                        <div
                          className="mt-1 flex items-start gap-1.5 text-red-600 dark:text-red-400 text-xs max-w-xl"
                          title={execution.error}
                        >
                          <AlertCircle className="w-3.5 h-3.5 shrink-0 mt-0.5" />
                          <span className="break-words">{execution.error}</span>
                        </div>
                      )}
                      {/* A run ended by a stop node carries a message the same
                          way a failed one carries an error, and it is the only
                          record of why a completed run did not do the rest of
                          its work. Shown in a neutral colour: this outcome was
                          chosen, not suffered. */}
                      {!execution.error && execution.stopReason && (
                        <div
                          className="mt-1 flex items-start gap-1.5 text-gray-600 dark:text-gray-400 text-xs max-w-xl"
                          title={execution.stopReason}
                        >
                          <Octagon className="w-3.5 h-3.5 shrink-0 mt-0.5" />
                          <span className="break-words">{execution.stopReason}</span>
                        </div>
                      )}
                    </td>
                    <td className="px-4 py-3 align-top text-gray-600 dark:text-gray-400">
                      {execution.triggerType}
                    </td>
                    <td className="px-4 py-3 align-top text-gray-600 dark:text-gray-400 text-sm">
                      {execution.runnerId || '-'}
                    </td>
                    <td className="px-4 py-3 align-top text-gray-500 dark:text-gray-400 text-sm">
                      {execution.startedAt
                        ? safeFormatDistanceToNow(execution.startedAt)
                        : '-'}
                    </td>
                    <td className="px-4 py-3 align-top text-gray-500 dark:text-gray-400 text-sm">
                      {execution.finishedAt && execution.startedAt
                        ? `${((execution.finishedAt - execution.startedAt) / 1000).toFixed(2)}s`
                        : execution.status === 'running'
                        ? 'Running...'
                        : '-'}
                    </td>
                  </tr>
                ))}
              </tbody>
            </table>
          </div>

          {/* Pagination */}
          <div className="flex items-center justify-between mt-4 px-2">
            <div className="text-sm text-gray-600 dark:text-gray-400">
              Showing {((page - 1) * PAGE_SIZE) + 1} - {Math.min(page * PAGE_SIZE, total)} of {total} executions
            </div>
            <div className="flex items-center gap-2">
              <button
                onClick={() => setPage(p => Math.max(1, p - 1))}
                disabled={page === 1}
                className="flex items-center gap-1 px-3 py-1.5 text-sm bg-white dark:bg-slate-800 border border-gray-200 dark:border-slate-700 rounded-lg hover:bg-gray-50 dark:hover:bg-slate-700 disabled:opacity-50 disabled:cursor-not-allowed"
              >
                <ChevronLeft className="w-4 h-4" />
                Previous
              </button>
              <span className="text-sm text-gray-600 dark:text-gray-400">
                Page {page} of {totalPages || 1}
              </span>
              <button
                onClick={() => setPage(p => p + 1)}
                disabled={!hasMore && page >= totalPages}
                className="flex items-center gap-1 px-3 py-1.5 text-sm bg-white dark:bg-slate-800 border border-gray-200 dark:border-slate-700 rounded-lg hover:bg-gray-50 dark:hover:bg-slate-700 disabled:opacity-50 disabled:cursor-not-allowed"
              >
                Next
                <ChevronRight className="w-4 h-4" />
              </button>
            </div>
          </div>
        </>
      )}
    </div>
  )
}