import { Server } from 'socket.io'
import jwt from 'jsonwebtoken'
import mysql from 'mysql2/promise'

// Simple in-memory structures keyed by eventId (for fast access)
const events = {}

const QUEUE_THRESHOLD = parseInt(process.env.QUEUE_THRESHOLD || "100", 10)
const CONCURRENT_ACTIVE = parseInt(process.env.CONCURRENT_ACTIVE || "50", 10)
const TOKEN_TTL_SECONDS = parseInt(process.env.TOKEN_TTL_SECONDS || `${15 * 60}`, 10)

// MySQL kapcsolat
let db = null

async function getDbConnection() {
  if (!db && process.env.MYSQL_HOST) {
    db = await mysql.createConnection({
      host: process.env.MYSQL_HOST,
      user: process.env.MYSQL_USER,
      password: process.env.MYSQL_PASSWORD,
      database: process.env.MYSQL_DATABASE,
    })
  }
  return db
}

function ensureEvent(eventId) {
  if (!events[eventId]) {
    events[eventId] = {
      sockets: new Set(), // connected socket ids
      queue: [], // array of socket ids in order
      active: new Set(), // sockets that currently hold a token (allowed to buy)
      queueOn: false,
    }
  }
  return events[eventId]
}

function broadcastUpdate(eventId, io) {
  const ev = events[eventId]
  if (!ev) return
  // notify all connected sockets in room
  for (const sid of ev.sockets) {
    const pos = ev.queue.indexOf(sid)
    io.to(sid).emit("queue_update", {
      activeCount: ev.sockets.size,
      position: pos === -1 ? null : pos + 1,
      estimatedWait: pos === -1 ? null : ev.queue.length * 5,
    })
  }
}

async function evaluateQueue(eventId, io) {
  const ev = events[eventId]
  if (!ev) return

  const connection = await getDbConnection()

  // ensure active set size <= CONCURRENT_ACTIVE
  while (ev.active.size < CONCURRENT_ACTIVE && ev.queue.length > 0) {
    const next = ev.queue.shift()
    if (!next) break
    
    // sign token
    const expiresAt = new Date(Date.now() + TOKEN_TTL_SECONDS * 1000)
    const token = jwt.sign({ sid: next, eventId }, process.env.JWT_SECRET || "dev-secret", {
      expiresIn: TOKEN_TTL_SECONDS,
    })
    
    ev.active.add(next)
    
    // Save to database
    if (connection) {
      try {
        await connection.execute(
          'INSERT INTO active_sessions (event_id, socket_id, jwt_token, expires_at) VALUES (?, ?, ?, ?) ON DUPLICATE KEY UPDATE jwt_token = VALUES(jwt_token), expires_at = VALUES(expires_at)',
          [eventId, next, token, expiresAt]
        )
      } catch (error) {
        console.error('DB error saving active session:', error)
      }
    }
    
    io.to(next).emit("granted", { token, expiresAt: expiresAt.toISOString() })
  }

  // If too many active (rare), revoke oldest
  if (ev.active.size > CONCURRENT_ACTIVE) {
    const toRevoke = Array.from(ev.active).slice(CONCURRENT_ACTIVE)
    for (const sid of toRevoke) {
      ev.active.delete(sid)
      io.to(sid).emit("revoked")
      
      // Remove from database
      if (connection) {
        try {
          await connection.execute(
            'DELETE FROM active_sessions WHERE event_id = ? AND socket_id = ?',
            [eventId, sid]
          )
        } catch (error) {
          console.error('DB error removing active session:', error)
        }
      }
    }
  }

  // If queue no longer needed, clear it
  if (ev.sockets.size < QUEUE_THRESHOLD) ev.queueOn = false

  // broadcast
  broadcastUpdate(eventId, io)
}

export async function GET(req) {
  if (global.io) {
    console.log("Socket.IO már fut")
    return Response.json({ message: "Socket.IO már inicializálva" })
  }

  console.log("Socket.IO inicializálása...")
  
  try {
    // Get the HTTP server instance from Next.js
    const server = req.nextUrl.protocol === 'https:' 
      ? require('https').createServer()
      : require('http').createServer()

    const io = new Server(server, {
      cors: {
        origin: "*",
        methods: ["GET", "POST"]
      }
    })

    global.io = io

    io.on("connection", (socket) => {
      console.log("Csatlakozott:", socket.id)

      socket.on("join_event", async ({ eventId }) => {
        if (!eventId) return
        const ev = ensureEvent(eventId)
        ev.sockets.add(socket.id)
        socket.join(eventId)

        const connection = await getDbConnection()

        // Get event threshold from database
        let eventThreshold = QUEUE_THRESHOLD
        if (connection) {
          try {
            const [rows] = await connection.execute(
              'SELECT max_concurrent_users FROM events WHERE id = ?',
              [eventId]
            )
            if (rows.length > 0) {
              eventThreshold = rows[0].max_concurrent_users
            }
          } catch (error) {
            console.error('DB error getting event:', error)
          }
        }

        // compute counts
        const activeCount = ev.sockets.size
        
        console.log(`Event ${eventId}: ${activeCount} users, threshold: ${eventThreshold}`)
        
        // turn on queue if threshold reached
        if (activeCount >= eventThreshold) {
          ev.queueOn = true
          console.log(`Queue activated for event ${eventId}`)
        }

        // if queueOn and socket not active, add to queue
        if (ev.queueOn && !ev.active.has(socket.id)) {
          if (!ev.queue.includes(socket.id)) {
            ev.queue.push(socket.id)
            console.log(`Added ${socket.id} to queue at position ${ev.queue.length}`)
            
            // Save queue position to database
            if (connection) {
              try {
                await connection.execute(
                  'INSERT INTO queue_entries (event_id, socket_id, position) VALUES (?, ?, ?) ON DUPLICATE KEY UPDATE position = VALUES(position)',
                  [eventId, socket.id, ev.queue.length]
                )
              } catch (error) {
                console.error('DB error saving queue entry:', error)
              }
            }
          }
        }

        // If queue is NOT active and user doesn't have access, grant it immediately
        if (!ev.queueOn && !ev.active.has(socket.id)) {
          console.log(`Granting immediate access to ${socket.id} (under threshold)`)
          const expiresAt = new Date(Date.now() + TOKEN_TTL_SECONDS * 1000)
          const token = jwt.sign({ sid: socket.id, eventId }, process.env.JWT_SECRET || "dev-secret", {
            expiresIn: TOKEN_TTL_SECONDS,
          })
          
          ev.active.add(socket.id)
          
          // Save to database
          if (connection) {
            try {
              await connection.execute(
                'INSERT INTO active_sessions (event_id, socket_id, jwt_token, expires_at) VALUES (?, ?, ?, ?) ON DUPLICATE KEY UPDATE jwt_token = VALUES(jwt_token), expires_at = VALUES(expires_at)',
                [eventId, socket.id, token, expiresAt]
              )
            } catch (error) {
              console.error('DB error saving active session:', error)
            }
          }
          
          io.to(socket.id).emit("granted", { token, expiresAt: expiresAt.toISOString() })
        }

        // evaluate granting (for queue users)
        await evaluateQueue(eventId, io)

        // send initial update
        const pos = ev.queue.indexOf(socket.id)
        io.to(socket.id).emit("queue_update", {
          activeCount: ev.sockets.size,
          position: pos === -1 ? null : pos + 1,
          estimatedWait: pos === -1 ? null : ev.queue.length * 5,
        })
      })

      socket.on("disconnect", () => {
        console.log("Lecsatlakozott:", socket.id)
        // remove from every event
        for (const [eventId, ev] of Object.entries(events)) {
          if (ev.sockets.has(socket.id)) ev.sockets.delete(socket.id)
          const qi = ev.queue.indexOf(socket.id)
          if (qi !== -1) ev.queue.splice(qi, 1)
          if (ev.active.has(socket.id)) ev.active.delete(socket.id)
          // re-evaluate to grant next in line
          evaluateQueue(eventId, io)
          // notify remaining sockets
          broadcastUpdate(eventId, io)
        }
      })
    })

    // Start the Socket.IO server on a different port
    const SOCKET_PORT = process.env.SOCKET_PORT || 4000
    server.listen(SOCKET_PORT, () => {
      console.log(`Socket.IO szerver fut a ${SOCKET_PORT} porton`)
    })

    return Response.json({ 
      message: "Socket.IO szerver inicializálva", 
      port: SOCKET_PORT 
    })
    
  } catch (error) {
    console.error("Socket.IO inicializálási hiba:", error)
    return Response.json({ error: "Nem sikerült inicializálni a Socket.IO szervert" }, { status: 500 })
  }
}