// useMetrics Composable
// Real-time system and agent metrics management

import { ref, computed, onMounted, onUnmounted, type Ref } from 'vue'
import { useWebSocket } from './useWebSocket'
import type { SystemMetrics, AgentMetrics, ResourceUsage } from '@/types'

interface MetricsComposable {
  // System Metrics
  systemMetrics: Ref<SystemMetrics | null>
  systemLoading: Ref<boolean>
  systemError: Ref<string | null>
  
  // Agent Metrics
  agentMetrics: Ref<Record<string, AgentMetrics>>
  agentLoading: Ref<boolean>
  agentError: Ref<string | null>
  
  // Computed
  systemHealthScore: Ref<number>
  topPerformingAgents: Ref<AgentMetrics[]>
  systemAlerts: Ref<string[]>
  
  // Actions
  refreshSystemMetrics: () => Promise<void>
  refreshAgentMetrics: (agentId?: string) => Promise<void>
  exportMetrics: (format: 'json' | 'csv') => Promise<void>
  clearErrors: () => void
  
  // Utils
  getMetricTrend: (current: number, previous: number) => 'up' | 'down' | 'stable'
  formatMetricValue: (value: number, type: string) => string
}

export function useMetrics(): MetricsComposable {
  // State
  const systemMetrics = ref<SystemMetrics | null>(null)
  const systemLoading = ref(false)
  const systemError = ref<string | null>(null)
  
  const agentMetrics = ref<Record<string, AgentMetrics>>({})
  const agentLoading = ref(false)
  const agentError = ref<string | null>(null)
  
  // WebSocket for real-time updates
  const { connected, on, off } = useWebSocket()
  
  // API client
  async function apiCall(endpoint: string) {
    const response = await fetch(`/api/v1${endpoint}`)
    
    if (!response.ok) {
      const errorData = await response.json().catch(() => ({}))
      throw new Error(errorData.message || `HTTP ${response.status}`)
    }
    
    return response.json()
  }
  
  // Computed
  const systemHealthScore = computed(() => {
    if (!systemMetrics.value) return 0
    
    const metrics = systemMetrics.value
    let score = 100
    
    // Deduct points for high resource usage
    if (metrics.memoryUsage.percentage > 80) score -= 20
    if (metrics.cpuUsage.percentage > 80) score -= 20
    
    // Deduct points for high error rate
    if (metrics.errorRate > 5) score -= 15
    if (metrics.errorRate > 10) score -= 25
    
    // Deduct points for network issues
    if (metrics.networkLatency > 500) score -= 10
    if (metrics.networkLatency > 1000) score -= 20
    
    // Deduct points for inactive agents
    const activePercentage = (metrics.activeAgents / metrics.totalAgents) * 100
    if (activePercentage < 80) score -= 10
    if (activePercentage < 50) score -= 20
    
    return Math.max(0, score)
  })
  
  const topPerformingAgents = computed(() => {
    return Object.values(agentMetrics.value)
      .sort((a, b) => {
        // Sort by success rate first, then by response time
        if (a.successRate !== b.successRate) {
          return b.successRate - a.successRate
        }
        return a.avgResponseTime - b.avgResponseTime
      })
      .slice(0, 5) // Top 5 performers
  })
  
  const systemAlerts = computed(() => {
    const alerts: string[] = []
    
    if (!systemMetrics.value) return alerts
    
    const metrics = systemMetrics.value
    
    if (metrics.memoryUsage.percentage > 90) {
      alerts.push('Critical: Memory usage above 90%')
    } else if (metrics.memoryUsage.percentage > 80) {
      alerts.push('Warning: High memory usage')
    }
    
    if (metrics.cpuUsage.percentage > 90) {
      alerts.push('Critical: CPU usage above 90%')
    } else if (metrics.cpuUsage.percentage > 80) {
      alerts.push('Warning: High CPU usage')
    }
    
    if (metrics.errorRate > 10) {
      alerts.push('Critical: High error rate detected')
    } else if (metrics.errorRate > 5) {
      alerts.push('Warning: Elevated error rate')
    }
    
    if (metrics.networkLatency > 1000) {
      alerts.push('Critical: Network latency above 1s')
    } else if (metrics.networkLatency > 500) {
      alerts.push('Warning: High network latency')
    }
    
    const inactiveAgents = metrics.totalAgents - metrics.activeAgents
    if (inactiveAgents > metrics.totalAgents * 0.5) {
      alerts.push('Warning: More than 50% of agents are inactive')
    }
    
    return alerts
  })
  
  // Actions
  async function refreshSystemMetrics(): Promise<void> {
    systemLoading.value = true
    systemError.value = null
    
    try {
      const response = await apiCall('/system/metrics')
      systemMetrics.value = response.data
    } catch (err) {
      systemError.value = err instanceof Error ? err.message : 'Failed to fetch system metrics'
      throw err
    } finally {
      systemLoading.value = false
    }
  }
  
  async function refreshAgentMetrics(agentId?: string): Promise<void> {
    agentLoading.value = true
    agentError.value = null
    
    try {
      const endpoint = agentId 
        ? `/agents/${agentId}/metrics` 
        : '/agents/metrics'
      
      const response = await apiCall(endpoint)
      
      if (agentId) {
        agentMetrics.value[agentId] = response.data
      } else {
        agentMetrics.value = response.data
      }
    } catch (err) {
      agentError.value = err instanceof Error ? err.message : 'Failed to fetch agent metrics'
      throw err
    } finally {
      agentLoading.value = false
    }
  }
  
  async function exportMetrics(format: 'json' | 'csv'): Promise<void> {
    try {
      const response = await fetch(`/api/v1/metrics/export?format=${format}`)
      
      if (!response.ok) {
        throw new Error('Failed to export metrics')
      }
      
      const blob = await response.blob()
      const url = URL.createObjectURL(blob)
      
      const link = document.createElement('a')
      link.href = url
      link.download = `saap-metrics-${new Date().toISOString().split('T')[0]}.${format}`
      document.body.appendChild(link)
      link.click()
      document.body.removeChild(link)
      
      URL.revokeObjectURL(url)
    } catch (err) {
      const message = err instanceof Error ? err.message : 'Failed to export metrics'
      systemError.value = message
      throw new Error(message)
    }
  }
  
  function clearErrors(): void {
    systemError.value = null
    agentError.value = null
  }
  
  // Utils
  function getMetricTrend(current: number, previous: number): 'up' | 'down' | 'stable' {
    const threshold = 0.05 // 5% change threshold
    const change = Math.abs(current - previous) / previous
    
    if (change < threshold) return 'stable'
    return current > previous ? 'up' : 'down'
  }
  
  function formatMetricValue(value: number, type: string): string {
    switch (type) {
      case 'percentage':
        return `${Math.round(value)}%`
      case 'bytes':
        return formatBytes(value)
      case 'duration':
        return formatDuration(value)
      case 'rate':
        return `${value.toFixed(2)}/min`
      case 'latency':
        return `${value}ms`
      case 'count':
        return value.toLocaleString()
      default:
        return value.toString()
    }
  }
  
  function formatBytes(bytes: number): string {
    if (bytes >= 1024 ** 3) {
      return `${(bytes / (1024 ** 3)).toFixed(1)}GB`
    }
    if (bytes >= 1024 ** 2) {
      return `${(bytes / (1024 ** 2)).toFixed(1)}MB`
    }
    if (bytes >= 1024) {
      return `${(bytes / 1024).toFixed(1)}KB`
    }
    return `${bytes}B`
  }
  
  function formatDuration(ms: number): string {
    if (ms < 1000) {
      return `${ms}ms`
    }
    if (ms < 60000) {
      return `${(ms / 1000).toFixed(1)}s`
    }
    return `${Math.round(ms / 60000)}m`
  }
  
  // WebSocket event handlers
  function handleMetricsUpdated(event: any) {
    if (event.data.type === 'system') {
      systemMetrics.value = event.data.metrics
    } else if (event.data.type === 'agent') {
      agentMetrics.value[event.data.agentId] = event.data.metrics
    }
  }
  
  // Lifecycle
  onMounted(() => {
    // Subscribe to WebSocket events
    on('metrics_updated', handleMetricsUpdated)
    
    // Initial data fetch
    if (connected.value) {
      Promise.all([
        refreshSystemMetrics().catch(() => {}),
        refreshAgentMetrics().catch(() => {})
      ])
    }
    
    // Set up periodic refresh (fallback if WebSocket fails)
    const refreshInterval = setInterval(() => {
      if (!connected.value) {
        refreshSystemMetrics().catch(() => {})
        refreshAgentMetrics().catch(() => {})
      }
    }, 30000) // 30 seconds
    
    onUnmounted(() => {
      clearInterval(refreshInterval)
    })
  })
  
  onUnmounted(() => {
    // Unsubscribe from WebSocket events
    off('metrics_updated', handleMetricsUpdated)
  })
  
  return {
    // System Metrics
    systemMetrics,
    systemLoading,
    systemError,
    
    // Agent Metrics
    agentMetrics,
    agentLoading,
    agentError,
    
    // Computed
    systemHealthScore,
    topPerformingAgents,
    systemAlerts,
    
    // Actions
    refreshSystemMetrics,
    refreshAgentMetrics,
    exportMetrics,
    clearErrors,
    
    // Utils
    getMetricTrend,
    formatMetricValue
  }
}

// Helper function to create mock metrics for development
export function createMockSystemMetrics(): SystemMetrics {
  return {
    totalAgents: 8,
    activeAgents: 6,
    totalMessages: 1247,
    messagesPerMinute: 15.3,
    avgResponseTime: 1250,
    systemUptime: Date.now() - (3 * 24 * 60 * 60 * 1000), // 3 days ago
    memoryUsage: {
      current: 8.5 * 1024 ** 3, // 8.5 GB
      maximum: 16 * 1024 ** 3,  // 16 GB
      percentage: 53,
      trend: 'stable'
    },
    cpuUsage: {
      current: 45,
      maximum: 100,
      percentage: 45,
      trend: 'increasing'
    },
    networkLatency: 125,
    errorRate: 2.1
  }
}

export function createMockAgentMetrics(agentId: string): AgentMetrics {
  return {
    agentId,
    messagesProcessed: Math.floor(Math.random() * 500) + 50,
    successRate: Math.random() * 20 + 80, // 80-100%
    avgResponseTime: Math.random() * 2000 + 500, // 0.5-2.5s
    errorCount: Math.floor(Math.random() * 10),
    uptime: Date.now() - (Math.random() * 24 * 60 * 60 * 1000), // Up to 24h ago
    memoryUsage: Math.random() * 512 * 1024 * 1024, // Up to 512MB
    cpuUsage: Math.random() * 50, // 0-50%
    lastActivity: new Date(Date.now() - Math.random() * 60 * 60 * 1000).toISOString() // Up to 1h ago
  }
}