package system

import (
	"fmt"
	"os"
	"path/filepath"
	"sync"

	"zlh-agent/internal/provision"
	"zlh-agent/internal/state"
)

/*
   console.go
   Handles:
     - Stdin command sending (bridge to process.go)
     - Log tailing
     - (future) WebSocket log streaming
*/

var (
	consoleMu sync.Mutex
)

/* --------------------------------------------------------------------------
   SendCommand (public wrapper)
   Used by HTTP endpoint: /console/command?cmd=...
----------------------------------------------------------------------------*/
func SendCommand(cmd string) error {
	return SendConsoleCommand(cmd)
}

/* --------------------------------------------------------------------------
   TailLatestLog (simple tail)
   Returns last N bytes from logs/latest.log

   Used now for API "tail logs"
   Will be used by WebSocket console streaming later.
----------------------------------------------------------------------------*/
func TailLatestLog(cfg *state.Config, maxBytes int) ([]byte, error) {
	dir := provision.ServerDir(*cfg)
	logFile := filepath.Join(dir, "logs", "latest.log")

	f, err := os.Open(logFile)
	if err != nil {
		return nil, fmt.Errorf("open log: %w", err)
	}
	defer f.Close()

	stat, err := f.Stat()
	if err != nil {
		return nil, fmt.Errorf("stat log: %w", err)
	}

	size := stat.Size()
	if size <= int64(maxBytes) {
		// Read whole file
		b, err := os.ReadFile(logFile)
		if err != nil {
			return nil, err
		}
		return b, nil
	}

	// Tail last N bytes
	offset := size - int64(maxBytes)
	buf := make([]byte, maxBytes)

	_, err = f.ReadAt(buf, offset)
	if err != nil {
		return nil, err
	}

	return buf, nil
}

/* --------------------------------------------------------------------------
   Future: WebSocket Console Support
   (stub, safe to leave here)
----------------------------------------------------------------------------*/

// PrepareWebSocketSession creates a placeholder session object.
// This will be expanded when we add WebSocket streaming.
func PrepareWebSocketSession() {
	// Stub for future WebSocket log streaming
}

/*
   Notes for WebSocket console:

   - Use TailLatestLog() to send first chunk
   - Then subscribe to real-time stdout/stderr pump via channels
   - console.go will own log streaming
   - process.go will expose a channel of new log lines
*/