// Package transfer handles binary content (images, files) transfer between
// clip-sync peers. It is kept separate from the text clipboard path so that
// text sync remains simple and safe; binary content is sent explicitly and is
// written to disk on the receiving side only when enabled.
package transfer

import (
	"encoding/base64"
	"fmt"
	"mime"
	"os"
	"path/filepath"
	"time"
)

// File is the wire payload for a transferred binary object.
type File struct {
	Name   string `json:"name"`
	Mime   string `json:"mime"`
	Data   string `json:"data"` // base64-encoded content
	Ts     int64  `json:"ts"`
	Origin string `json:"origin"`
}

// ReadFile reads a file from disk and encodes it as a transfer.File payload.
func ReadFile(path, origin string) (*File, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}

	mimeType := mime.TypeByExtension(filepath.Ext(path))
	if mimeType == "" {
		mimeType = "application/octet-stream"
	}

	return &File{
		Name:   filepath.Base(path),
		Mime:   mimeType,
		Data:   base64.StdEncoding.EncodeToString(data),
		Ts:     time.Now().UnixNano(),
		Origin: origin,
	}, nil
}

// Decode returns the raw bytes of the file.
func (f *File) Decode() ([]byte, error) {
	if f.Data == "" {
		return nil, fmt.Errorf("transfer: empty data")
	}
	return base64.StdEncoding.DecodeString(f.Data)
}

// SaveTo writes the decoded content to the given directory, sanitizing the
// file name to avoid path traversal. It returns the written path.
func (f *File) SaveTo(dir string) (string, error) {
	data, err := f.Decode()
	if err != nil {
		return "", err
	}

	if err := os.MkdirAll(dir, 0755); err != nil {
		return "", err
	}

	name := filepath.Base(f.Name)
	if name == "." || name == "" || name == string(filepath.Separator) {
		name = "received.bin"
	}

	// Avoid overwriting existing files: append a numeric suffix if needed.
	dest := filepath.Join(dir, name)
	for i := 1; ; i++ {
		if _, err := os.Stat(dest); os.IsNotExist(err) {
			break
		}
		ext := filepath.Ext(name)
		base := name[:len(name)-len(ext)]
		dest = filepath.Join(dir, fmt.Sprintf("%s (%d)%s", base, i, ext))
	}

	return dest, os.WriteFile(dest, data, 0644)
}