import { useMemo } from 'react'
import { useParams, Link } from 'react-router-dom'
import styles from './AgentHealth.module.css'

// Layout
import { AppShell } from '../../design-system/layout/AppShell/AppShell'
import { Sidebar } from '../../design-system/layout/Sidebar/Sidebar'
import { TopBar } from '../../design-system/layout/TopBar/TopBar'

// Composites
import { GroupCard } from '../../design-system/composites/GroupCard/GroupCard'
import { LineChart } from '../../design-system/composites/LineChart/LineChart'
import { EventFeed } from '../../design-system/composites/EventFeed/EventFeed'

// Primitives
import { StatusDot } from '../../design-system/primitives/StatusDot/StatusDot'
import { MonoText } from '../../design-system/primitives/MonoText/MonoText'
import { Badge } from '../../design-system/primitives/Badge/Badge'
import { StatCard } from '../../design-system/primitives/StatCard/StatCard'

// Mock data
import { agents, type AgentHealth as AgentHealthData } from '../../mocks/agents'
import { SIDEBAR_APPS } from '../../mocks/sidebar'
import { agentEvents } from '../../mocks/agentEvents'

// ── URL scope parsing ────────────────────────────────────────────────────────

type Scope =
  | { level: 'all' }
  | { level: 'app'; appId: string }
  | { level: 'instance'; appId: string; instanceId: string }

function useScope(): Scope {
  const { '*': rest } = useParams()
  const segments = rest?.split('/').filter(Boolean) ?? []
  if (segments.length >= 2) return { level: 'instance', appId: segments[0], instanceId: segments[1] }
  if (segments.length === 1) return { level: 'app', appId: segments[0] }
  return { level: 'all' }
}

// ── Data grouping ────────────────────────────────────────────────────────────

interface AppGroup {
  appId: string
  instances: AgentHealthData[]
  liveCount: number
  staleCount: number
  deadCount: number
  totalTps: number
  totalActiveRoutes: number
  totalRoutes: number
}

function groupByApp(agentList: AgentHealthData[]): AppGroup[] {
  const map = new Map<string, AgentHealthData[]>()
  for (const a of agentList) {
    const list = map.get(a.appId) ?? []
    list.push(a)
    map.set(a.appId, list)
  }
  return Array.from(map.entries()).map(([appId, instances]) => ({
    appId,
    instances,
    liveCount: instances.filter((i) => i.status === 'live').length,
    staleCount: instances.filter((i) => i.status === 'stale').length,
    deadCount: instances.filter((i) => i.status === 'dead').length,
    totalTps: instances.reduce((s, i) => s + i.tps, 0),
    totalActiveRoutes: instances.reduce((s, i) => s + i.activeRoutes, 0),
    totalRoutes: instances.reduce((s, i) => s + i.totalRoutes, 0),
  }))
}

function appHealth(group: AppGroup): 'success' | 'warning' | 'error' {
  if (group.deadCount > 0) return 'error'
  if (group.staleCount > 0) return 'warning'
  return 'success'
}

// ── Trend data (mock) ────────────────────────────────────────────────────────

function buildTrendData(agent: AgentHealthData) {
  const now = Date.now()
  const points = 20
  const interval = (3 * 60 * 60 * 1000) / points

  const throughput = Array.from({ length: points }, (_, i) => ({
    x: new Date(now - (points - i) * interval),
    y: Math.max(0, agent.tps + (Math.random() - 0.5) * 4),
  }))

  const errorRate = Array.from({ length: points }, (_, i) => ({
    x: new Date(now - (points - i) * interval),
    y: Math.max(0, (agent.errorRate ? parseFloat(agent.errorRate) : 0.5) + (Math.random() - 0.5) * 2),
  }))

  return { throughput, errorRate }
}

// ── Breadcrumb ───────────────────────────────────────────────────────────────

function buildBreadcrumb(scope: Scope) {
  const crumbs: { label: string; href?: string }[] = [
    { label: 'System', href: '/' },
    { label: 'Agents', href: '/agents' },
  ]
  if (scope.level === 'app' || scope.level === 'instance') {
    crumbs.push({ label: scope.appId, href: `/agents/${scope.appId}` })
  }
  if (scope.level === 'instance') {
    crumbs.push({ label: scope.instanceId })
  }
  return crumbs
}

// ── AgentHealth page ─────────────────────────────────────────────────────────

export function AgentHealth() {
  const scope = useScope()

  // Filter agents by scope
  const filteredAgents = useMemo(() => {
    if (scope.level === 'all') return agents
    if (scope.level === 'app') return agents.filter((a) => a.appId === scope.appId)
    return agents.filter((a) => a.appId === scope.appId && a.id === scope.instanceId)
  }, [scope])

  const groups = useMemo(() => groupByApp(filteredAgents), [filteredAgents])

  // Aggregate stats
  const totalInstances = filteredAgents.length
  const liveCount = filteredAgents.filter((a) => a.status === 'live').length
  const staleCount = filteredAgents.filter((a) => a.status === 'stale').length
  const deadCount = filteredAgents.filter((a) => a.status === 'dead').length
  const totalTps = filteredAgents.reduce((s, a) => s + a.tps, 0)
  const totalActiveRoutes = filteredAgents.reduce((s, a) => s + a.activeRoutes, 0)

  // Filter events by scope
  const filteredEvents = useMemo(() => {
    if (scope.level === 'all') return agentEvents
    if (scope.level === 'app') {
      return agentEvents.filter((e) => e.message.includes(`[${scope.appId}]`))
    }
    return agentEvents.filter(
      (e) => e.message.includes(`[${scope.appId}]`) && e.message.includes(scope.instanceId),
    )
  }, [scope])

  // Single instance for expanded charts
  const singleInstance = scope.level === 'instance' ? filteredAgents[0] : null
  const trendData = singleInstance ? buildTrendData(singleInstance) : null

  const isFullWidth = scope.level !== 'all'

  return (
    <AppShell sidebar={<Sidebar apps={SIDEBAR_APPS} />}>
      <TopBar
        breadcrumb={buildBreadcrumb(scope)}
        environment="PRODUCTION"
        shift="Day (06:00-18:00)"
        user={{ name: 'hendrik' }}
      />

      <div className={styles.content}>
        {/* Stat strip */}
        <div className={styles.statStrip}>
          <StatCard label="Total Instances" value={String(totalInstances)} />
          <StatCard label="Live" value={String(liveCount)} accent="success" />
          <StatCard label="Stale" value={String(staleCount)} accent={staleCount > 0 ? 'warning' : undefined} />
          <StatCard label="Dead" value={String(deadCount)} accent={deadCount > 0 ? 'error' : undefined} />
          <StatCard label="Total TPS" value={`${totalTps.toFixed(1)}/s`} />
          <StatCard label="Active Routes" value={String(totalActiveRoutes)} />
        </div>

        {/* Scope breadcrumb trail */}
        {scope.level !== 'all' && (
          <div className={styles.scopeTrail}>
            <Link to="/agents" className={styles.scopeLink}>All Agents</Link>
            {scope.level === 'instance' && (
              <>
                <span className={styles.scopeSep}>&#9656;</span>
                <Link to={`/agents/${scope.appId}`} className={styles.scopeLink}>{scope.appId}</Link>
              </>
            )}
            <span className={styles.scopeSep}>&#9656;</span>
            <span className={styles.scopeCurrent}>
              {scope.level === 'app' ? scope.appId : scope.instanceId}
            </span>
          </div>
        )}

        {/* Section header */}
        <div className={styles.sectionHeaderRow}>
          <span className={styles.sectionTitle}>
            {scope.level === 'all' ? 'Agent Groups' : scope.level === 'app' ? scope.appId : scope.instanceId}
          </span>
          <span className={styles.sectionMeta}>
            {liveCount}/{totalInstances} live
          </span>
        </div>

        {/* Group cards grid */}
        <div className={isFullWidth ? styles.groupGridSingle : styles.groupGrid}>
          {groups.map((group) => (
            <GroupCard
              key={group.appId}
              title={group.appId}
              accent={appHealth(group)}
              headerRight={
                <span className={styles.instanceCountBadge}>
                  {group.instances.length} instance{group.instances.length !== 1 ? 's' : ''}
                </span>
              }
              meta={
                <div className={styles.groupMeta}>
                  <span><strong>{group.totalTps.toFixed(1)}</strong> msg/s</span>
                  <span><strong>{group.totalActiveRoutes}</strong>/{group.totalRoutes} routes</span>
                  <span>
                    <StatusDot variant={appHealth(group) === 'success' ? 'live' : appHealth(group) === 'warning' ? 'stale' : 'dead'} />
                  </span>
                </div>
              }
              footer={group.deadCount > 0 ? (
                <div className={styles.alertBanner}>
                  <span className={styles.alertIcon}>&#9888;</span>
                  <span>Single point of failure — {group.deadCount === group.instances.length ? 'no redundancy' : `${group.deadCount} dead instance${group.deadCount > 1 ? 's' : ''}`}</span>
                </div>
              ) : undefined}
            >
              {/* Instance header row */}
              <div className={styles.instanceHeader}>
                <span />
                <span>Instance</span>
                <span>State</span>
                <span>Uptime</span>
                <span>TPS</span>
                <span>Errors</span>
                <span>Heartbeat</span>
              </div>

              {/* Instance rows */}
              {group.instances.map((inst) => (
                <div key={inst.id}>
                  <Link
                    to={`/agents/${inst.appId}/${inst.id}`}
                    className={[
                      styles.instanceRow,
                      scope.level === 'instance' && scope.instanceId === inst.id ? styles.instanceRowActive : '',
                    ].filter(Boolean).join(' ')}
                  >
                    <StatusDot variant={inst.status === 'live' ? 'live' : inst.status === 'stale' ? 'stale' : 'dead'} />
                    <MonoText size="sm" className={styles.instanceName}>{inst.name}</MonoText>
                    <Badge
                      label={inst.status.toUpperCase()}
                      color={inst.status === 'live' ? 'success' : inst.status === 'stale' ? 'warning' : 'error'}
                      variant="filled"
                    />
                    <MonoText size="xs" className={styles.instanceMeta}>{inst.uptime}</MonoText>
                    <MonoText size="xs" className={styles.instanceMeta}>{inst.tps.toFixed(1)}/s</MonoText>
                    <MonoText size="xs" className={inst.errorRate ? styles.instanceError : styles.instanceMeta}>
                      {inst.errorRate ?? '0 err/h'}
                    </MonoText>
                    <MonoText size="xs" className={
                      inst.status === 'dead' ? styles.instanceHeartbeatDead :
                      inst.status === 'stale' ? styles.instanceHeartbeatStale :
                      styles.instanceMeta
                    }>
                      {inst.lastSeen}
                    </MonoText>
                  </Link>

                  {/* Expanded charts for single instance */}
                  {singleInstance?.id === inst.id && trendData && (
                    <div className={styles.instanceCharts}>
                      <div className={styles.chartPanel}>
                        <div className={styles.chartTitle}>Throughput (msg/s)</div>
                        <LineChart
                          series={[{ label: 'tps', data: trendData.throughput }]}
                          height={160}
                          width={480}
                          yLabel="msg/s"
                        />
                      </div>
                      <div className={styles.chartPanel}>
                        <div className={styles.chartTitle}>Error Rate (err/h)</div>
                        <LineChart
                          series={[{ label: 'errors', data: trendData.errorRate, color: 'var(--error)' }]}
                          height={160}
                          width={480}
                          yLabel="err/h"
                        />
                      </div>
                    </div>
                  )}
                </div>
              ))}
            </GroupCard>
          ))}
        </div>

        {/* EventFeed */}
        {filteredEvents.length > 0 && (
          <div className={styles.eventSection}>
            <div className={styles.sectionHeaderRow}>
              <span className={styles.sectionTitle}>Timeline</span>
            </div>
            <EventFeed events={filteredEvents} />
          </div>
        )}
      </div>
    </AppShell>
  )
}
