import { useState, useEffect, useMemo } from 'react'
import { useNavigate, useSearchParams } from 'react-router-dom'
import { useQuery, useMutation, useQueryClient, keepPreviousData } from '@tanstack/react-query'
import { executionsApi, workflowsApi, nodesApi, type ExecutionListItem } from '../api/workflows'
import { useExecutionListUpdates } from '../hooks/useExecutionListUpdates'
import { toMillis } from '../utils/timestamps'
import { formatDistanceToNow } from 'date-fns'
import { CheckCircle, XCircle, Clock, Ban, RefreshCw, ChevronLeft, ChevronRight, AlertCircle, Octagon, Square, Hourglass, Search, X } 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'
  }
}

// An execution that has not finished has finishedAt 0, so its duration has to
// be measured against now. "Running..." told you nothing about whether a run had
// been going for two seconds or two hours.
function formatElapsed(startedAt: number | null, finishedAt: number | null, now: number): string {
  if (!startedAt) return '-'
  const end = finishedAt ?? now
  const seconds = (end - startedAt) / 1000
  if (seconds < 0) return '-'
  if (seconds < 60) return `${seconds.toFixed(2)}s`
  const minutes = Math.floor(seconds / 60)
  const rest = Math.floor(seconds % 60)
  if (minutes < 60) return `${minutes}m ${rest}s`
  const hours = Math.floor(minutes / 60)
  return `${hours}h ${minutes % 60}m`
}

// Statuses a run can still leave on its own, so a Stop is meaningful.
const IN_FLIGHT = ['running', 'pending', 'waiting', 'resuming']

const PAGE_SIZE = 20

// Offered as filters. "pending" and "resuming" are deliberately absent: they are
// momentary states nobody can catch on purpose, and they are covered by the
// in-flight handling elsewhere on the row.
const STATUS_FILTERS = ['running', 'waiting', 'completed', 'failed', 'cancelled'] as const

type RangeKey = 'any' | '15m' | '1h' | '24h' | '7d' | '30d'

const RANGES: { key: RangeKey; label: string; ms: number }[] = [
  { key: 'any', label: 'Any time', ms: 0 },
  { key: '15m', label: 'Last 15 minutes', ms: 15 * 60 * 1000 },
  { key: '1h', label: 'Last hour', ms: 60 * 60 * 1000 },
  { key: '24h', label: 'Last 24 hours', ms: 24 * 60 * 60 * 1000 },
  { key: '7d', label: 'Last 7 days', ms: 7 * 24 * 60 * 60 * 1000 },
  { key: '30d', label: 'Last 30 days', ms: 30 * 24 * 60 * 60 * 1000 },
]

// The first two are ordered by the database over the whole result set. The
// duration ones cannot be: duration is not a stored field, so nothing can sort
// or page by it server-side, and they reorder the page in the browser instead.
// The labels say so rather than letting the numbers imply a global ranking.
type SortKey = 'newest' | 'oldest' | 'longest' | 'shortest'

const SORTS: { key: SortKey; label: string }[] = [
  { key: 'newest', label: 'Newest first' },
  { key: 'oldest', label: 'Oldest first' },
  { key: 'longest', label: 'Longest duration (this page)' },
  { key: 'shortest', label: 'Shortest duration (this page)' },
]

// Trigger types the engine writes itself, so they never appear among the node
// definitions. Without these the trigger filter would be missing the most
// common value of all, "manual".
const ENGINE_TRIGGER_TYPES: { value: string; label: string }[] = [
  { value: 'manual', label: 'Manual' },
  { value: 'webhook', label: 'Webhook' },
  { value: 'schedule', label: 'Schedule' },
  { value: 'workflow', label: 'Called by another workflow' },
  { value: 'error-workflow', label: 'Error handler' },
]

function durationOf(execution: ExecutionListItem, now: number): number {
  const started = toMillis(execution.startedAt)
  if (started === null) return -1
  return (toMillis(execution.finishedAt) ?? now) - started
}

export default function ExecutionsPage() {
  const navigate = useNavigate()
  const queryClient = useQueryClient()
  const [searchParams, setSearchParams] = useSearchParams()

  // The URL is the single source of truth for the filters, so a filtered view
  // can be linked to and survives a reload.
  const search = searchParams.get('q') || ''
  const statuses = (searchParams.get('status') || '').split(',').filter(Boolean)
  const workflowId = searchParams.get('workflow') || ''
  const triggerType = searchParams.get('trigger') || ''
  const range = (searchParams.get('range') || 'any') as RangeKey
  const sort = (searchParams.get('sort') || 'newest') as SortKey
  const page = Math.max(1, Number(searchParams.get('page')) || 1)

  const hasFilters =
    search !== '' || statuses.length > 0 || workflowId !== '' || triggerType !== '' || range !== 'any'

  // Built from the previous params rather than from the ones this render closed
  // over: the search box writes on a timer, and a filter changed while that
  // timer was pending would otherwise be undone when it fired.
  const updateParams = (changes: Record<string, string | null>, keepPage = false) => {
    setSearchParams(previous => {
      const next = new URLSearchParams(previous)
      for (const [key, value] of Object.entries(changes)) {
        if (value === null || value === '') {
          next.delete(key)
        } else {
          next.set(key, value)
        }
      }
      // Any change to what is being asked for invalidates the page number: page
      // 7 of the old result set says nothing about the new one.
      if (!keepPage) {
        next.delete('page')
      }
      return next
    }, { replace: true })
  }

  // The search box is typed into, so it holds its own value and pushes it to the
  // URL once typing stops. Writing every keystroke to the URL would fire a query
  // per character.
  const [searchInput, setSearchInput] = useState(search)
  useEffect(() => {
    setSearchInput(search)
  }, [search])
  useEffect(() => {
    if (searchInput === search) return
    const timer = setTimeout(() => updateParams({ q: searchInput }), 300)
    return () => clearTimeout(timer)
  }, [searchInput])

  // The range presets are relative to now, but the boundary is fixed when the
  // range is chosen and not recomputed per render or per page. A sliding
  // boundary would move the result set underneath the pagination, so paging
  // through "Last hour" would skip and repeat rows.
  const startedAfter = useMemo(() => {
    const found = RANGES.find(r => r.key === range)
    if (!found || found.ms === 0) return undefined
    return Date.now() - found.ms
  }, [range])

  // 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, isFetching, refetch } = useQuery({
    // sort belongs in the key because "oldest first" is a different request, not
    // a different rendering of the same one.
    queryKey: ['executions', { search, statuses, workflowId, triggerType, range, sort, page }],
    queryFn: () =>
      executionsApi.query({
        search,
        status: statuses,
        triggerType: triggerType ? [triggerType] : undefined,
        workflowId: workflowId || undefined,
        startedAfter,
        sortOrder: sort === 'oldest' ? 'asc' : 'desc',
        page,
        pageSize: PAGE_SIZE,
      }),
    // Without this the table empties on every filter change and the layout
    // jumps; the old rows stay until the new ones arrive.
    placeholderData: keepPreviousData,
  })

  // Names for the workflow filter. A large pageSize because this is a picker,
  // not a listing, and paging it would hide workflows from the filter.
  const { data: workflowsData } = useQuery({
    queryKey: ['workflows', 'all-for-filter'],
    queryFn: () => workflowsApi.list(1, 200),
    staleTime: 5 * 60 * 1000,
  })

  // Trigger node definitions, to name the trigger types with something a person
  // recognises rather than the node id stored on the execution.
  const { data: nodesData } = useQuery({
    queryKey: ['node-definitions'],
    queryFn: () => nodesApi.list(),
    staleTime: 5 * 60 * 1000,
  })

  const triggerOptions = useMemo(() => {
    const options = new Map<string, string>()
    for (const engine of ENGINE_TRIGGER_TYPES) {
      options.set(engine.value, engine.label)
    }
    for (const definition of nodesData?.nodes || []) {
      if (definition.isTrigger) {
        options.set(definition.id, definition.name || definition.id)
      }
    }
    // A run recorded under a trigger type this build no longer knows about would
    // otherwise silently vanish from the dropdown while still selected in the URL.
    if (triggerType && !options.has(triggerType)) {
      options.set(triggerType, triggerType)
    }
    return [...options.entries()].sort((a, b) => a[1].localeCompare(b[1]))
  }, [nodesData, triggerType])

  const workflowOptions = useMemo(() => {
    const options = new Map<string, string>()
    for (const workflow of workflowsData?.workflows || []) {
      options.set(workflow.id, workflow.name || workflow.id)
    }
    // Executions outlive the workflows that produced them, so a filtered link
    // can name a workflow that has since been deleted. Keep it selectable.
    if (workflowId && !options.has(workflowId)) {
      options.set(workflowId, workflowId)
    }
    return [...options.entries()].sort((a, b) => a[1].localeCompare(b[1]))
  }, [workflowsData, workflowId])

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

  // A ticking clock only while something is actually in flight. Without the
  // guard this would re-render the page once a second for ever on a list of
  // finished runs.
  const [now, setNow] = useState(() => Date.now())
  const hasInFlight = (data?.executions || []).some(e => IN_FLIGHT.includes(e.status))
  useEffect(() => {
    if (!hasInFlight) return
    const timer = setInterval(() => setNow(Date.now()), 1000)
    return () => clearInterval(timer)
  }, [hasInFlight])

  const cancelMutation = useMutation({
    mutationFn: (id: string) => executionsApi.cancel(id),
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ['executions'] })
    },
  })

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

  const executions = useMemo(() => {
    const rows = data?.executions || []
    if (sort !== 'longest' && sort !== 'shortest') {
      return rows
    }
    const direction = sort === 'longest' ? -1 : 1
    return [...rows].sort((a, b) => (durationOf(a, now) - durationOf(b, now)) * direction)
  }, [data, sort, now])

  const toggleStatus = (status: string) => {
    const next = statuses.includes(status)
      ? statuses.filter(s => s !== status)
      : [...statuses, status]
    updateParams({ status: next.join(',') })
  }

  const clearFilters = () => {
    setSearchParams(new URLSearchParams(), { replace: true })
  }

  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" />
      case 'waiting':
        // Distinct from running on purpose: a waiting run is not working, it
        // needs an answer, and stopping it is a different act from stopping
        // something mid-flight.
        return <Hourglass className="w-5 h-5 text-amber-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'
      case 'waiting':
        return 'bg-amber-100 dark:bg-amber-900/30 text-amber-700 dark:text-amber-400'
      default:
        return 'bg-gray-100 dark:bg-slate-700 text-gray-600 dark:text-gray-400'
    }
  }

  const selectClass =
    'px-3 py-1.5 text-sm bg-white dark:bg-slate-800 border border-gray-200 dark:border-slate-700 rounded-lg text-gray-700 dark:text-gray-200'

  return (
    <div className="h-full overflow-auto p-6">
      <div className="flex items-center justify-between mb-4">
        <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={clsx('w-4 h-4', isFetching && 'animate-spin')} />
          Refresh
        </button>
      </div>

      <div className="mb-4 space-y-3">
        <div className="flex flex-wrap items-center gap-2">
          <div className="relative">
            <Search className="w-4 h-4 absolute left-3 top-1/2 -translate-y-1/2 text-gray-400" />
            <input
              value={searchInput}
              onChange={e => setSearchInput(e.target.value)}
              placeholder="Search workflow name, or paste an execution id"
              className="w-80 pl-9 pr-8 py-1.5 text-sm bg-white dark:bg-slate-800 border border-gray-200 dark:border-slate-700 rounded-lg text-gray-700 dark:text-gray-200 placeholder-gray-400"
            />
            {searchInput && (
              <button
                onClick={() => setSearchInput('')}
                title="Clear the search"
                className="absolute right-2 top-1/2 -translate-y-1/2 text-gray-400 hover:text-gray-600 dark:hover:text-gray-200"
              >
                <X className="w-4 h-4" />
              </button>
            )}
          </div>

          <select
            value={workflowId}
            onChange={e => updateParams({ workflow: e.target.value })}
            className={selectClass}
          >
            <option value="">All workflows</option>
            {workflowOptions.map(([id, name]) => (
              <option key={id} value={id}>{name}</option>
            ))}
          </select>

          <select
            value={triggerType}
            onChange={e => updateParams({ trigger: e.target.value })}
            className={selectClass}
          >
            <option value="">All triggers</option>
            {triggerOptions.map(([value, label]) => (
              <option key={value} value={value}>{label}</option>
            ))}
          </select>

          <select
            value={range}
            onChange={e => updateParams({ range: e.target.value === 'any' ? null : e.target.value })}
            className={selectClass}
          >
            {RANGES.map(r => (
              <option key={r.key} value={r.key}>{r.label}</option>
            ))}
          </select>

          <select
            value={sort}
            onChange={e => updateParams({ sort: e.target.value === 'newest' ? null : e.target.value })}
            className={selectClass}
          >
            {SORTS.map(s => (
              <option key={s.key} value={s.key}>{s.label}</option>
            ))}
          </select>

          {hasFilters && (
            <button
              onClick={clearFilters}
              className="flex items-center gap-1.5 px-3 py-1.5 text-sm text-gray-600 dark:text-gray-400 hover:bg-gray-100 dark:hover:bg-slate-700 rounded-lg"
            >
              <X className="w-4 h-4" />
              Clear filters
            </button>
          )}
        </div>

        <div className="flex flex-wrap items-center gap-2">
          {STATUS_FILTERS.map(status => (
            <button
              key={status}
              onClick={() => toggleStatus(status)}
              className={clsx(
                'px-3 py-1 rounded-full text-xs font-medium border capitalize',
                statuses.includes(status)
                  ? 'border-primary-500 ring-1 ring-primary-500 ' + getStatusBadgeClass(status)
                  : 'border-gray-200 dark:border-slate-700 text-gray-600 dark:text-gray-400 hover:bg-gray-100 dark:hover:bg-slate-700'
              )}
            >
              {status}
            </button>
          ))}
          {statuses.length === 0 && (
            <span className="text-xs text-gray-400 dark:text-gray-500">All statuses</span>
          )}
        </div>
      </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">
          {/* Three different nothings, which need three different answers: an
              empty page past the end of the results, a filter that excludes
              everything, and a platform on which nothing has ever run. */}
          {page > 1 ? (
            <>
              <p className="text-gray-500 dark:text-gray-400">
                Nothing on page {page}. The results may have changed since this link was made.
              </p>
              <button
                onClick={() => updateParams({ page: null }, false)}
                className="mt-3 px-3 py-1.5 text-sm text-primary-600 dark:text-primary-400 hover:underline"
              >
                Back to the first page
              </button>
            </>
          ) : hasFilters ? (
            <>
              <p className="text-gray-500 dark:text-gray-400">No executions match these filters.</p>
              <button
                onClick={clearFilters}
                className="mt-3 px-3 py-1.5 text-sm text-primary-600 dark:text-primary-400 hover:underline"
              >
                Clear filters
              </button>
            </>
          ) : (
            <>
              <p className="text-gray-500 dark:text-gray-400">No executions yet</p>
              <p className="mt-1 text-sm text-gray-400 dark:text-gray-500">
                A run appears here as soon as a workflow is started, by hand or by a trigger.
              </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>
                  <th className="px-4 py-3 text-right text-sm font-medium text-gray-600 dark:text-gray-300">
                    Actions
                  </th>
                </tr>
              </thead>
              <tbody className="divide-y divide-gray-200 dark:divide-slate-700">
                {executions.map(execution => {
                  const startedAt = toMillis(execution.startedAt)
                  const finishedAt = toMillis(execution.finishedAt)
                  return (
                  <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>
                      <div className="text-xs text-gray-400 dark:text-gray-500 font-mono">
                        {execution.id}
                      </div>
                      {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"
                      title={startedAt ? new Date(startedAt).toLocaleString() : undefined}
                    >
                      {startedAt ? safeFormatDistanceToNow(startedAt) : '-'}
                    </td>
                    <td className="px-4 py-3 align-top text-gray-500 dark:text-gray-400 text-sm">
                      <span className={clsx(IN_FLIGHT.includes(execution.status) && 'tabular-nums')}>
                        {formatElapsed(startedAt, finishedAt, now)}
                      </span>
                    </td>
                    <td className="px-4 py-3 align-top text-right">
                      {IN_FLIGHT.includes(execution.status) && (
                        <button
                          onClick={(e) => {
                            // The row opens the execution; the button must not.
                            e.stopPropagation()
                            cancelMutation.mutate(execution.id)
                          }}
                          disabled={cancelMutation.isPending}
                          title="Stop this execution. The runner stops at the next node boundary"
                          className="inline-flex items-center gap-1.5 px-2 py-1 text-xs text-red-600 dark:text-red-400 hover:bg-red-50 dark:hover:bg-red-900/20 rounded-lg disabled:opacity-50"
                        >
                          <Square className="w-3 h-3" />
                          Stop
                        </button>
                      )}
                    </td>
                  </tr>
                  )
                })}
              </tbody>
            </table>
          </div>

          {(sort === 'longest' || sort === 'shortest') && (
            <p className="mt-2 px-2 text-xs text-gray-500 dark:text-gray-400">
              Duration is not stored, so it can only be ordered within the {executions.length} rows
              on this page - not across all {total} results.
            </p>
          )}

          {/* 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}
              {hasFilters ? ' matching executions' : ' executions'}
            </div>
            <div className="flex items-center gap-2">
              <button
                onClick={() => updateParams({ page: page > 2 ? String(page - 1) : null }, true)}
                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={() => updateParams({ page: String(page + 1) }, true)}
                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>
  )
}