/**
 * Email-Logs Statistics Endpoint
 *
 * GET /api/email-logs/stats
 *
 * Liefert Statistiken über Email-Logs.
 * Nur für Super Admins und Tenant-Admins (für ihre eigenen Tenants).
 *
 * Query-Parameter:
 * - tenantId: number (optional)
 * - period: '24h' | '7d' | '30d' (default: '7d')
 */

import { getPayload } from 'payload'
import configPromise from '@payload-config'
import { NextRequest, NextResponse } from 'next/server'

interface UserWithTenants {
  id: number
  email: string
  isSuperAdmin?: boolean
  tenants?: Array<{ tenant: { id: number } | number }>
}

function getUserTenantIds(user: UserWithTenants): number[] {
  return (user.tenants || []).map((t) => (typeof t.tenant === 'object' ? t.tenant.id : t.tenant))
}

function getPeriodDate(period: string): Date {
  const now = new Date()
  switch (period) {
    case '24h':
      return new Date(now.getTime() - 24 * 60 * 60 * 1000)
    case '30d':
      return new Date(now.getTime() - 30 * 24 * 60 * 60 * 1000)
    case '7d':
    default:
      return new Date(now.getTime() - 7 * 24 * 60 * 60 * 1000)
  }
}

export async function GET(req: NextRequest): Promise<NextResponse> {
  try {
    const payload = await getPayload({ config: configPromise })

    // Auth prüfen
    const { user } = await payload.auth({ headers: req.headers })

    if (!user) {
      return NextResponse.json({ error: 'Nicht authentifiziert' }, { status: 401 })
    }

    const typedUser = user as unknown as UserWithTenants

    // Query-Parameter parsen
    const searchParams = req.nextUrl.searchParams
    const tenantIdParam = searchParams.get('tenantId')
    const period = searchParams.get('period') || '7d'

    // Tenant-Zugriff prüfen
    const userTenantIds = getUserTenantIds(typedUser)
    let tenantFilter: number[] | undefined

    if (typedUser.isSuperAdmin) {
      if (tenantIdParam) {
        tenantFilter = [parseInt(tenantIdParam, 10)]
      }
    } else {
      if (tenantIdParam) {
        const requestedTenant = parseInt(tenantIdParam, 10)
        if (!userTenantIds.includes(requestedTenant)) {
          return NextResponse.json({ error: 'Kein Zugriff auf diesen Tenant' }, { status: 403 })
        }
        tenantFilter = [requestedTenant]
      } else {
        tenantFilter = userTenantIds
      }
    }

    const periodDate = getPeriodDate(period)

    // Basis-Where für alle Queries
    const baseWhere: Record<string, unknown> = {
      createdAt: { greater_than_equal: periodDate.toISOString() },
    }

    if (tenantFilter) {
      baseWhere.tenant = { in: tenantFilter }
    }

    // Statistiken parallel abrufen - Type assertions für email-logs Collection
    const countFn = payload.count as Function
    const findFn = payload.find as Function

    const [totalResult, sentResult, failedResult, pendingResult, recentFailed] = await Promise.all([
      // Gesamt
      countFn({
        collection: 'email-logs',
        where: baseWhere,
      }),
      // Gesendet
      countFn({
        collection: 'email-logs',
        where: { ...baseWhere, status: { equals: 'sent' } },
      }),
      // Fehlgeschlagen
      countFn({
        collection: 'email-logs',
        where: { ...baseWhere, status: { equals: 'failed' } },
      }),
      // Ausstehend
      countFn({
        collection: 'email-logs',
        where: { ...baseWhere, status: { equals: 'pending' } },
      }),
      // Letzte 5 fehlgeschlagene (für Quick-View)
      findFn({
        collection: 'email-logs',
        where: { ...baseWhere, status: { equals: 'failed' } },
        limit: 5,
        sort: '-createdAt',
        depth: 1,
      }),
    ])

    // Erfolgsrate berechnen
    const total = totalResult.totalDocs
    const sent = sentResult.totalDocs
    const failed = failedResult.totalDocs
    const pending = pendingResult.totalDocs
    const successRate = total > 0 ? Math.round((sent / total) * 100 * 10) / 10 : 0

    // Statistiken nach Quelle
    const sourceStats: Record<string, number> = {}
    const sources = ['manual', 'form', 'system', 'newsletter']

    await Promise.all(
      sources.map(async (source) => {
        const result = await countFn({
          collection: 'email-logs',
          where: { ...baseWhere, source: { equals: source } },
        })
        sourceStats[source] = result.totalDocs
      }),
    )

    return NextResponse.json({
      success: true,
      period,
      periodStart: periodDate.toISOString(),
      stats: {
        total,
        sent,
        failed,
        pending,
        successRate,
      },
      bySource: sourceStats,
      recentFailures: recentFailed.docs.map((doc: Record<string, unknown>) => ({
        id: doc.id,
        to: doc.to,
        subject: doc.subject,
        error: doc.error,
        createdAt: doc.createdAt,
        tenantId:
          typeof doc.tenant === 'object' && doc.tenant
            ? (doc.tenant as { id?: number }).id
            : doc.tenant,
      })),
    })
  } catch (error) {
    console.error('[EmailLogs:Stats] Error:', error)
    return NextResponse.json({ error: 'Interner Serverfehler' }, { status: 500 })
  }
}