import { useEffect, useMemo, useState } from 'react'
import Link from 'next/link'
import { Card } from '@/libs/frontend-ui-primitives'
import {
  getMissionControlRelayLabel,
  getMissionControlRelays,
  missionControlApi,
  type MissionControlBridgeStatusResponse,
  type MissionControlRelayPayload,
  type MissionControlRelaySnapshot,
} from '@/services/api/missionControl'
import { statsApi, type ExplorerStats } from '@/services/api/stats'
import { explorerFeaturePages } from '@/data/explorerOperations'
import { summarizeChainActivity } from '@/utils/activityContext'
import ActivityContextPanel from '@/components/common/ActivityContextPanel'
import FreshnessTrustNote from '@/components/common/FreshnessTrustNote'
import { resolveEffectiveFreshness } from '@/utils/explorerFreshness'

type FeedState = 'connecting' | 'live' | 'fallback'

interface RelayLaneCard {
  key: string
  label: string
  status: string
  profile: string
  sourceChain: string
  destinationChain: string
  queueSize: number
  processed: number
  failed: number
  lastPolled: string
  bridgeAddress: string
  issueScope: string | null
  issueMessage: string | null
  inventoryShortfallWei: string | null
  inventoryRequiredWei: string | null
  inventoryAvailableWei: string | null
}

const relayOrder = ['mainnet_cw', 'mainnet_weth', 'bsc', 'avax', 'avax_cw', 'avax_to_138']

function relativeAge(isoString?: string): string {
  if (!isoString) return 'Unknown'
  const parsed = Date.parse(isoString)
  if (!Number.isFinite(parsed)) return 'Unknown'
  const seconds = Math.max(0, Math.round((Date.now() - parsed) / 1000))
  if (seconds < 60) return `${seconds}s ago`
  const minutes = Math.round(seconds / 60)
  if (minutes < 60) return `${minutes}m ago`
  const hours = Math.round(minutes / 60)
  return `${hours}h ago`
}

function shortAddress(value?: string): string {
  if (!value) return 'Unspecified'
  if (value.length <= 14) return value
  return `${value.slice(0, 6)}...${value.slice(-4)}`
}

function resolveSnapshot(relay?: MissionControlRelayPayload): MissionControlRelaySnapshot | null {
  return relay?.url_probe?.body || relay?.file_snapshot || null
}

function relayPolicyCue(snapshot: MissionControlRelaySnapshot | null): string | null {
  if (!snapshot) return null
  if (snapshot.last_error?.scope === 'bridge_inventory') {
    return 'Queued release waiting on bridge inventory'
  }
  if (snapshot.last_error?.scope === 'bridge_inventory_probe') {
    return 'Bridge inventory check is temporarily unavailable'
  }
  if (String(snapshot.status || '').toLowerCase() === 'paused' && snapshot.monitoring?.delivery_enabled === false) {
    return 'Delivery disabled by policy'
  }
  return null
}

function laneToneClasses(status: string): string {
  const normalized = status.toLowerCase()
  if (['degraded', 'stale', 'stopped', 'down', 'snapshot-error'].includes(normalized)) {
    return 'border-red-200 bg-red-50/80 dark:border-red-900/60 dark:bg-red-950/20'
  }
  if (['paused', 'starting'].includes(normalized)) {
    return 'border-amber-200 bg-amber-50/80 dark:border-amber-900/60 dark:bg-amber-950/20'
  }
  return 'border-emerald-200 bg-emerald-50/80 dark:border-emerald-900/60 dark:bg-emerald-950/20'
}

function statusPillClasses(status: string): string {
  const normalized = status.toLowerCase()
  if (['degraded', 'stale', 'stopped', 'down', 'snapshot-error'].includes(normalized)) {
    return 'bg-red-100 text-red-700 dark:bg-red-900/50 dark:text-red-100'
  }
  if (['paused', 'starting'].includes(normalized)) {
    return 'bg-amber-100 text-amber-800 dark:bg-amber-900/50 dark:text-amber-100'
  }
  return 'bg-emerald-100 text-emerald-700 dark:bg-emerald-900/50 dark:text-emerald-100'
}

function formatWeiToToken(value?: string | null): string {
  if (!value) return 'Unknown'
  try {
    const raw = BigInt(value)
    const whole = raw / 10n ** 18n
    const fractional = (raw % 10n ** 18n).toString().padStart(18, '0').slice(0, 6).replace(/0+$/, '')
    return fractional ? `${whole.toString()}.${fractional}` : whole.toString()
  } catch {
    return value
  }
}

function ActionLink({
  href,
  label,
  external,
}: {
  href: string
  label: string
  external?: boolean
}) {
  const className = 'inline-flex items-center text-sm font-semibold text-primary-600 hover:underline'
  const text = `${label} ->`

  if (external) {
    return (
      <a href={href} className={className} target="_blank" rel="noopener noreferrer">
        {text}
      </a>
    )
  }

  return (
    <Link href={href} className={className}>
      {text}
    </Link>
  )
}

export default function BridgeMonitoringPage({
  initialBridgeStatus = null,
  initialStats = null,
}: {
  initialBridgeStatus?: MissionControlBridgeStatusResponse | null
  initialStats?: ExplorerStats | null
}) {
  const [bridgeStatus, setBridgeStatus] = useState<MissionControlBridgeStatusResponse | null>(initialBridgeStatus)
  const [stats, setStats] = useState<ExplorerStats | null>(initialStats)
  const [feedState, setFeedState] = useState<FeedState>(initialBridgeStatus ? 'fallback' : 'connecting')
  const page = explorerFeaturePages.bridge

  useEffect(() => {
    let cancelled = false

    const loadSnapshot = async () => {
      try {
        const [snapshot, latestStats] = await Promise.all([
          missionControlApi.getBridgeStatus(),
          statsApi.get().catch(() => null),
        ])
        if (!cancelled) {
          setBridgeStatus(snapshot)
          if (latestStats) {
            setStats(latestStats)
          }
        }
      } catch (error) {
        if (!cancelled && process.env.NODE_ENV !== 'production') {
          console.warn('Failed to load bridge monitoring snapshot:', error)
        }
      }
    }

    loadSnapshot()

    const unsubscribe = missionControlApi.subscribeBridgeStatus(
      (status) => {
        if (!cancelled) {
          setBridgeStatus(status)
          setFeedState('live')
        }
      },
      (error) => {
        if (!cancelled) {
          setFeedState('fallback')
        }
        if (process.env.NODE_ENV !== 'production') {
          console.warn('Bridge monitoring live stream issue:', error)
        }
      }
    )

    return () => {
      cancelled = true
      unsubscribe()
    }
  }, [])

  const activityContext = useMemo(
    () =>
      summarizeChainActivity({
        blocks: [],
        transactions: [],
        latestBlockNumber: stats?.latest_block,
        latestBlockTimestamp: null,
        freshness: resolveEffectiveFreshness(stats, bridgeStatus),
        diagnostics: stats?.diagnostics ?? bridgeStatus?.data?.diagnostics ?? null,
      }),
    [bridgeStatus, stats],
  )

  const relayLanes = useMemo((): RelayLaneCard[] => {
    const relays = getMissionControlRelays(bridgeStatus)
    if (!relays) return []

    const orderIndex = new Map(relayOrder.map((key, index) => [key, index]))

    return Object.entries(relays)
      .map(([key, relay]) => {
        const snapshot = resolveSnapshot(relay)
        const status = String(snapshot?.status || (relay.file_snapshot_error ? 'snapshot-error' : 'configured')).toLowerCase()
        return {
          key,
          label: getMissionControlRelayLabel(key),
          status:
            snapshot?.last_error?.scope === 'bridge_inventory'
              ? 'underfunded'
              : snapshot?.last_error?.scope === 'bridge_inventory_probe'
                ? 'warning'
                : status,
          profile: snapshot?.service?.profile || key,
          sourceChain: snapshot?.source?.chain_name || 'Unknown',
          destinationChain: snapshot?.destination?.chain_name || 'Unknown',
          queueSize: snapshot?.queue?.size ?? 0,
          processed: snapshot?.queue?.processed ?? 0,
          failed: snapshot?.queue?.failed ?? 0,
          lastPolled: relativeAge(snapshot?.last_source_poll?.at),
          bridgeAddress:
            snapshot?.destination?.relay_bridge_default ||
            snapshot?.destination?.relay_bridge ||
            snapshot?.source?.bridge_filter ||
            '',
          issueScope: snapshot?.last_error?.scope || null,
          issueMessage: snapshot?.last_error?.message || null,
          inventoryShortfallWei: snapshot?.last_error?.shortfall || null,
          inventoryRequiredWei: snapshot?.last_error?.required_amount || null,
          inventoryAvailableWei: snapshot?.last_error?.available_amount || null,
        }
      })
      .sort((left, right) => {
        const leftIndex = orderIndex.get(left.key) ?? Number.MAX_SAFE_INTEGER
        const rightIndex = orderIndex.get(right.key) ?? Number.MAX_SAFE_INTEGER
        return leftIndex - rightIndex || left.label.localeCompare(right.label)
      })
  }, [bridgeStatus])

  const chainStatus = bridgeStatus?.data?.chains?.['138']
  const overallStatus = bridgeStatus?.data?.status || 'unknown'
  const checkedAt = relativeAge(bridgeStatus?.data?.checked_at)

  return (
    <div className="container mx-auto px-4 py-6 sm:py-8">
      <div className="mb-6 max-w-4xl sm:mb-8">
        <div className="mb-3 inline-flex rounded-full border border-sky-200 bg-sky-50 px-3 py-1 text-xs font-semibold uppercase tracking-[0.2em] text-sky-700">
          {page.eyebrow}
        </div>
        <h1 className="mb-3 text-3xl font-bold text-gray-900 dark:text-white sm:text-4xl">
          {page.title}
        </h1>
        <p className="text-base leading-7 text-gray-600 dark:text-gray-400 sm:text-lg sm:leading-8">
          {page.description}
        </p>
      </div>

      {page.note ? (
        <Card className="mb-6 border border-amber-200 bg-amber-50/70 dark:border-amber-900/50 dark:bg-amber-950/20">
          <p className="text-sm leading-6 text-amber-950 dark:text-amber-100">
            {page.note}
          </p>
        </Card>
      ) : null}

      <div className="mb-6">
        <ActivityContextPanel context={activityContext} title="Bridge Freshness Context" />
        <FreshnessTrustNote
          className="mt-3"
          context={activityContext}
          stats={stats}
          bridgeStatus={bridgeStatus}
          scopeLabel="Bridge relay posture is shown alongside the same explorer freshness model used on the homepage and core explorer routes"
        />
      </div>

      <div className="mb-6 grid gap-4 lg:grid-cols-3">
        <Card className="border border-sky-200 bg-sky-50/70 dark:border-sky-900/50 dark:bg-sky-950/20">
          <div className="text-sm font-semibold uppercase tracking-wide text-sky-800 dark:text-sky-100">
            Relay Fleet
          </div>
          <div className="mt-2 text-2xl font-bold text-gray-900 dark:text-white">
            {overallStatus}
          </div>
          <div className="mt-2 text-sm text-gray-700 dark:text-gray-300">
            {relayLanes.length} managed lanes visible
          </div>
          <div className="mt-2 text-xs font-medium uppercase tracking-wide text-sky-800/80 dark:text-sky-100/80">
            Feed: {feedState === 'live' ? 'Live SSE' : feedState === 'fallback' ? 'Snapshot fallback' : 'Connecting'}
          </div>
        </Card>

        <Card className="border border-gray-200 dark:border-gray-700">
          <div className="text-sm font-semibold uppercase tracking-wide text-gray-700 dark:text-gray-300">
            Chain 138 RPC
          </div>
          <div className="mt-2 text-2xl font-bold text-gray-900 dark:text-white">
            {chainStatus?.status || 'unknown'}
          </div>
          <div className="mt-2 text-sm text-gray-600 dark:text-gray-400">
            Head age: {chainStatus?.head_age_sec != null ? `${chainStatus.head_age_sec.toFixed(1)}s` : 'Unknown'}
          </div>
          <div className="mt-1 text-sm text-gray-600 dark:text-gray-400">
            Latency: {chainStatus?.latency_ms != null ? `${chainStatus.latency_ms}ms` : 'Unknown'}
          </div>
        </Card>

        <Card className="border border-gray-200 dark:border-gray-700">
          <div className="text-sm font-semibold uppercase tracking-wide text-gray-700 dark:text-gray-300">
            Last Check
          </div>
          <div className="mt-2 text-2xl font-bold text-gray-900 dark:text-white">
            {checkedAt}
          </div>
          <div className="mt-2 text-sm text-gray-600 dark:text-gray-400">
            Public status JSON and live stream are both active.
          </div>
          <div className="mt-4">
            <ActionLink href="/explorer-api/v1/track1/bridge/status" label="Open status JSON" external />
          </div>
        </Card>
      </div>

      <div className="mb-8 grid gap-4 lg:grid-cols-2 xl:grid-cols-3">
        {relayLanes.map((lane) => (
          <Card key={lane.key} className={`border ${laneToneClasses(lane.status)}`}>
            <div className="flex items-start justify-between gap-3">
              <div>
                <div className="text-lg font-semibold text-gray-900 dark:text-white">
                  {lane.label}
                </div>
                <div className="mt-1 text-sm text-gray-600 dark:text-gray-400">
                  {`${lane.sourceChain} -> ${lane.destinationChain}`}
                </div>
              </div>
              <div className={`rounded-full px-3 py-1 text-xs font-semibold uppercase tracking-wide ${statusPillClasses(lane.status)}`}>
                {lane.status}
              </div>
            </div>

            <div className="mt-4 grid grid-cols-2 gap-3 text-sm">
              <div>
                <div className="text-gray-500 dark:text-gray-400">Profile</div>
                <div className="font-medium text-gray-900 dark:text-white">{lane.profile}</div>
              </div>
              <div>
                <div className="text-gray-500 dark:text-gray-400">Queue</div>
                <div className="font-medium text-gray-900 dark:text-white">{lane.queueSize}</div>
              </div>
              <div>
                <div className="text-gray-500 dark:text-gray-400">Processed</div>
                <div className="font-medium text-gray-900 dark:text-white">{lane.processed}</div>
              </div>
              <div>
                <div className="text-gray-500 dark:text-gray-400">Failed</div>
                <div className="font-medium text-gray-900 dark:text-white">{lane.failed}</div>
              </div>
            </div>

            <div className="mt-4 text-sm text-gray-600 dark:text-gray-400">
              Last polled: {lane.lastPolled}
            </div>
            <div className="mt-1 text-sm text-gray-600 dark:text-gray-400">
              Bridge: {shortAddress(lane.bridgeAddress)}
            </div>
            {relayPolicyCue(resolveSnapshot((getMissionControlRelays(bridgeStatus) || {})[lane.key])) ? (
              <div className="mt-3 text-xs font-medium uppercase tracking-wide text-amber-700 dark:text-amber-300">
                {relayPolicyCue(resolveSnapshot((getMissionControlRelays(bridgeStatus) || {})[lane.key]))}
              </div>
            ) : null}
            {lane.issueScope === 'bridge_inventory' ? (
              <div className="mt-3 rounded-2xl border border-amber-200 bg-amber-50/80 p-3 text-sm text-amber-950 dark:border-amber-900/60 dark:bg-amber-950/30 dark:text-amber-100">
                <div className="font-semibold">Bridge inventory below required release amount</div>
                <div className="mt-1">
                  Shortfall: {formatWeiToToken(lane.inventoryShortfallWei)} WETH
                </div>
                <div className="mt-1 text-xs opacity-80">
                  Required: {formatWeiToToken(lane.inventoryRequiredWei)} WETH · Available: {formatWeiToToken(lane.inventoryAvailableWei)} WETH
                </div>
              </div>
            ) : null}
          </Card>
        ))}
      </div>

      <div className="grid gap-4 lg:grid-cols-2">
        {page.actions.map((action) => (
          <Card key={`${action.title}-${action.href}`} className="border border-gray-200 dark:border-gray-700">
            <div className="flex h-full flex-col">
              <div className="text-base font-semibold text-gray-900 dark:text-white">
                {action.title}
              </div>
              <p className="mt-2 flex-1 text-sm leading-6 text-gray-600 dark:text-gray-400">
                {action.description}
              </p>
              <div className="mt-4">
                <ActionLink
                  href={action.href}
                  label={action.label}
                  external={'external' in action ? action.external : undefined}
                />
              </div>
            </div>
          </Card>
        ))}
      </div>
    </div>
  )
}