package log

import (
	"fmt"
	"os"
	"sync"
	"time"

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

// ShareLog writes share result lines to an append-only text file.
//
// Line format (accept): 2026-04-04T12:00:00Z ACCEPT  <user>  diff=<diff>  latency=<ms>ms
// Line format (reject): 2026-04-04T12:00:00Z REJECT  <user>  reason="<message>"
//
//	sl := log.NewShareLog("/var/log/proxy-shares.log")
//	bus.Subscribe(proxy.EventAccept, sl.OnAccept)
//	bus.Subscribe(proxy.EventReject, sl.OnReject)
type ShareLog 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
}

// NewShareLog stores the destination path and lazily opens it on first write.
//
//	sl := log.NewShareLog("/var/log/proxy-shares.log")
func NewShareLog(path string) *ShareLog {
	return &ShareLog{path: path}
}

// OnAccept writes an ACCEPT line.
//
//	sl.OnAccept(proxy.Event{Miner: miner, Diff: 100000})
func (l *ShareLog) OnAccept(event proxy.Event) {
	if event.Miner == nil {
		return
	}

	line := fmt.Sprintf("%s ACCEPT  %s  diff=%d  latency=%dms\n",
		timestamp(),
		event.Miner.User(),
		event.Diff,
		event.Latency,
	)
	l.writeLine(line)
}

// OnReject writes a REJECT line with the rejection reason.
//
//	sl.OnReject(proxy.Event{Miner: miner, Error: "Low difficulty share"})
func (l *ShareLog) OnReject(event proxy.Event) {
	if event.Miner == nil {
		return
	}

	line := fmt.Sprintf("%s REJECT  %s  reason=%q\n",
		timestamp(),
		event.Miner.User(),
		event.Error,
	)
	l.writeLine(line)
}

// Close releases the append-only file handle if it has been opened.
//
//	sl.Close()
func (l *ShareLog) 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 *ShareLog) 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)
}

func timestamp() string {
	return time.Now().UTC().Format(time.RFC3339)
}