otimize e melhore o código tauri v2 rust

use serde::{Deserialize, Serialize};
use std::path::{Path, PathBuf};
use tauri::{AppHandle, Emitter};
use reqwest::Client;
use tokio::{fs, io::AsyncWriteExt, time::Instant};

use std::time::{Duration};

#[derive(Deserialize, Clone)]
struct PatchEntry {
    file_name: String,
}

#[derive(Serialize, Clone)]
struct DownloadInfo {
    current_file: usize,
    total_files: usize,
    file_name: String,
    downloaded_bytes: u64,
    total_bytes: u64,
    speed: f64,
}

#[derive(Serialize, Clone)]
struct DownloadStatus {
    status: String,
    additional_info: Option<String>,
}

const SERVER_URL: &str = "https://hil-speed.hetzner.com/";
const EMIT_INTERVAL: Duration = Duration::from_millis(100);

fn get_exe_dir() -> PathBuf {
    std::env::current_exe().unwrap().parent().unwrap().to_path_buf()
}

async fn dir_exists(path: &Path) -> Result<bool, std::io::Error> {
    match fs::metadata(path).await {
        Ok(metadata) => Ok(metadata.is_dir()),
        Err(err) if err.kind() == std::io::ErrorKind::NotFound => Ok(false),
        Err(err) => Err(err),
    }
}

async fn read_patch_file(path: &Path) -> Result<Vec<PatchEntry>, String> {
    let content = fs::read_to_string(path).await.map_err(|e| e.to_string())?;
    let patches: Vec<PatchEntry> = serde_json::from_str(&content).map_err(|e| e.to_string())?;
    Ok(patches)
}

async fn emit_download_status(app_handle: &AppHandle, status: &str, additional_info: Option<String>,) -> Result<(), String> {
    app_handle.emit("download_status", DownloadStatus {status: status.to_string(), additional_info }).map_err(|e| e.to_string())
}

async fn download_file(
    app_handle: &AppHandle,
    client: &Client,
    entry: &PatchEntry,
    download_dir: &Path,
    current_file: usize,
    total_files: usize,
) -> Result<(), String> {

    let file_path = download_dir.join(&entry.file_name);

    loop {
        let url = format!("{}{}", SERVER_URL, entry.file_name);
        let mut response = match client.get(&url).send().await {
            Ok(resp) => {
                if resp.status().is_success() {
                    resp
                } else {
                    return Err(format!(
                        "Failed to download '{}': HTTP {}",
                        entry.file_name,
                        resp.status()
                    ));
                }
            }
            Err(_) => {
                let mut countdown = 15;
                while countdown > 0 {
                    emit_download_status(app_handle, "Reconnecting", Some(countdown.to_string())).await?;
                    tokio::time::sleep(Duration::from_secs(1)).await;
                    countdown -= 1;
                }
                continue; // Try again
            }
        };

        let total_bytes = response.content_length().unwrap_or(0);

        let _ = fs::remove_file(&file_path).await;
        let mut file = fs::File::create(&file_path).await.map_err(|e| e.to_string())?;

        let mut downloaded_bytes = 0u64;
        let start_time = Instant::now();

        emit_download_status(app_handle, "Start", None).await?;

        let mut last_emit_time = Instant::now();
        let mut downloading_message_sent = false;

        let mut download_error = false;
        let mut speed = 0.0;

        loop {
            match response.chunk().await {
                Ok(Some(chunk)) => {
                    if let Err(e) = file.write_all(&chunk).await {
                        return Err(format!( "Error writing to file '{}': {}", entry.file_name, e.to_string()));
                    }
                    downloaded_bytes += chunk.len() as u64;

                    let now = Instant::now();
                    if now.duration_since(last_emit_time) >= EMIT_INTERVAL {
                        if !downloading_message_sent {
                            emit_download_status(app_handle, "Downloading", None).await?;
                            downloading_message_sent = true;
                        }

                        speed = if start_time.elapsed().is_zero() {
                            0.0
                        } else {
                            downloaded_bytes as f64 / start_time.elapsed().as_secs_f64()
                        };

                        app_handle.emit("download_info", DownloadInfo { current_file, total_files, file_name: entry.file_name.clone(), downloaded_bytes, total_bytes, speed},).map_err(|e| e.to_string())?;
                        last_emit_time = now;
                    }
                }
                Ok(None) => {
                    break;
                }
                Err(_) => {
                    download_error = true;
                    break;
                }
            }
        }

        if download_error {
            drop(file);

            let mut countdown = 15;
            while countdown > 0 {
                emit_download_status(app_handle, "Reconnecting", Some(countdown.to_string())).await?;
                tokio::time::sleep(Duration::from_secs(1)).await;
                countdown -= 1;
            }

            emit_download_status(app_handle, "Reconnecting", None).await?;

            if check_server_connection(client, SERVER_URL).await.is_err() {
                continue;
            } else {
                continue;
            }
        } else {
            app_handle.emit("download_info", DownloadInfo { current_file, total_files, file_name: entry.file_name.clone(), downloaded_bytes, total_bytes, speed },).map_err(|e| e.to_string())?;       
            break;
        }
    }

    Ok(())
}

async fn check_server_connection(client: &Client, url: &str) -> Result<(), String> {
    let response = client.get(url).send().await.map_err(|e| e.to_string())?;
    if response.status().is_success() {
        Ok(())
    } else {
        Err(format!("Falha ao conectar ao servidor: HTTP {}", response.status()))
    }
}

#[tauri::command]
pub async fn start_downloads(app_handle: AppHandle) -> Result<(), String> {
    let exe_dir = get_exe_dir();

    let patch_file_path = exe_dir.join("patch.json");
    let download_dir = exe_dir.join("patchs");

    if !dir_exists(&download_dir).await.map_err(|e| e.to_string())? {
        fs::create_dir_all(&download_dir).await.map_err(|e| e.to_string())?;
    }

    let patches = read_patch_file(&patch_file_path).await?;

    let client = Client::new();
    let total_files = patches.len();

    emit_download_status(&app_handle, "Connecting", None).await?;

    let server_url = SERVER_URL;
    if let Err(err) = check_server_connection(&client, server_url).await {
        let error_message = format!("Erro ao conectar ao servidor: {}", err);
        eprintln!("{}", error_message);
        emit_download_status(&app_handle, "Error", Some(error_message.clone())).await?;
        return Err(error_message);
    }

    emit_download_status(&app_handle, "Connected", None).await?;

    for (idx, entry) in patches.iter().enumerate() {
        let current_file = idx + 1;
        if let Err(err) = download_file(&app_handle, &client, entry, &download_dir, current_file, total_files).await {
            let error_message = format!("Erro ao baixar '{}': {}", entry.file_name, err);
            eprintln!("{}", error_message);
            emit_download_status(&app_handle, "Error", Some(error_message.clone())).await?;
            return Err(error_message);
        }
    }

    // Emitir status de conclusão
    emit_download_status(&app_handle, "Completed", None).await?;

    Ok(())
}