// Package log implements append-only access and share logging for the proxy.
//
//	al, result := log.NewAccessLog("/var/log/proxy-access.log")
//	bus.Subscribe(proxy.EventLogin, al.OnLogin)
//	bus.Subscribe(proxy.EventClose, al.OnClose)
package log

import (
	"fmt"
	"os"
	"sync"

	"dappco.re/go/core/proxy"
)

// AccessLog writes append-only connection lines.
//
//	al := log.NewAccessLog("/var/log/proxy-access.log")
//	bus.Subscribe(proxy.EventLogin, al.OnLogin)
//	bus.Subscribe(proxy.EventClose, al.OnClose)
type AccessLog struct {
	path   string
	mu     sync.Mutex
	file   *os.File
	closed bool
}

// NewAccessLog opens the file lazily on first write.
//
//	al := log.NewAccessLog("/var/log/proxy-access.log")
func NewAccessLog(path string) *AccessLog {
	return &AccessLog{path: path}
}

// OnLogin writes `2026-04-04T12:00:00Z CONNECT  10.0.0.1  WALLET  XMRig/6.21.0`.
//
//	al.OnLogin(proxy.Event{Miner: miner})
func (l *AccessLog) OnLogin(event proxy.Event) {
	if event.Miner == nil {
		return
	}

	line := fmt.Sprintf("%s CONNECT  %s  %s  %s\n",
		utcTimestamp(),
		event.Miner.IP(),
		event.Miner.User(),
		event.Miner.Agent(),
	)
	l.writeLine(line)
}

// OnClose writes `2026-04-04T12:00:00Z CLOSE    10.0.0.1  WALLET  rx=512  tx=4096`.
//
//	al.OnClose(proxy.Event{Miner: miner})
func (l *AccessLog) OnClose(event proxy.Event) {
	if event.Miner == nil {
		return
	}

	line := fmt.Sprintf("%s CLOSE    %s  %s  rx=%d  tx=%d\n",
		utcTimestamp(),
		event.Miner.IP(),
		event.Miner.User(),
		event.Miner.RX(),
		event.Miner.TX(),
	)
	l.writeLine(line)
}

// Close releases the append-only file handle if it has been opened.
//
//	al.Close()
func (l *AccessLog) Close() {
	if l == nil {
		return
	}

	l.mu.Lock()
	defer l.mu.Unlock()

	if l.closed {
		return
	}
	l.closed = true
	if l.file != nil {
		_ = l.file.Close()
		l.file = nil
	}
}

func (l *AccessLog) writeLine(line string) {
	if l == nil || l.path == "" {
		return
	}

	l.mu.Lock()
	defer l.mu.Unlock()

	if l.closed {
		return
	}

	if l.file == nil {
		file, errorValue := os.OpenFile(l.path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
		if errorValue != nil {
			return
		}
		l.file = file
	}

	_, _ = l.file.WriteString(line)
}