// 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 connection lifecycle lines to an append-only text file.
//
// Line format (connect): 2026-04-04T12:00:00Z CONNECT  <ip>  <user>  <agent>
// Line format (close):   2026-04-04T12:00:00Z CLOSE    <ip>  <user>  rx=<bytes>  tx=<bytes>
//
//	al, result := 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
	// f is opened append-only on first write; nil until first event.
	// Uses core.File for I/O abstraction.
	f      *os.File
	closed bool
}

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

// OnLogin writes a CONNECT line. Called synchronously from the event bus.
//
//	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",
		timestamp(),
		event.Miner.IP(),
		event.Miner.User(),
		event.Miner.Agent(),
	)
	l.writeLine(line)
}

// OnClose writes a CLOSE line with byte counts.
//
//	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",
		timestamp(),
		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.f != nil {
		_ = l.f.Close()
		l.f = 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.f == nil {
		file, errorValue := os.OpenFile(l.path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0o644)
		if errorValue != nil {
			return
		}
		l.f = file
	}

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