use base64::{Engine as _, engine::general_purpose};
use dashmap::DashMap;
use futures_util::stream::StreamExt;
use openssl::pkey::PKey;
use openssl::sign::Verifier;
use sha2::{Digest, Sha512};
use std::fs;
use std::path::Path;
use std::sync::OnceLock;
use std::time::Instant;
use std::{
    fs::{File, create_dir_all},
    io::{BufReader, copy},
    path::PathBuf,
    process::Command,
    time::Duration,
};
use sysinfo::System;
use tauri::window::{ProgressBarState, ProgressBarStatus};
use tauri::{AppHandle, Emitter, Manager};
use tauri_plugin_os::platform;
use tauri_plugin_prevent_default::Flags;
use tokio::io::AsyncReadExt;
use tokio::{io::AsyncWriteExt, time::timeout};
use zip::ZipArchive;
use zip::result::ZipError;

#[cfg(unix)]
use std::os::unix::fs::PermissionsExt;

static CANCEL_MAP: OnceLock<DashMap<String, bool>> = OnceLock::new();

fn cancel_map() -> &'static DashMap<String, bool> {
    CANCEL_MAP.get_or_init(DashMap::new)
}

fn is_cancelled(name: &str) -> bool {
    cancel_map().get(name).map(|v| *v).unwrap_or(false)
}

fn is_running_by_path(path: &Path) -> bool {
    let sys = System::new_all();
    let target = match path.canonicalize() {
        Ok(t) => t,
        Err(_) => return false,
    };
    sys.processes().values().any(|proc| {
        proc.exe()
            .and_then(|exe| exe.canonicalize().ok())
            .map_or(false, |exe| exe == target)
    })
}

fn should_skip(name: &str) -> bool {
    name.starts_with("__MACOSX/")
        || name == "__MACOSX"
        || name.ends_with("/.DS_Store")
        || name.ends_with(".DS_Store")
}

async fn unzip_to_dir(app: AppHandle, zip_path: PathBuf, out_dir: PathBuf, name: String) -> String {
    let _ = app.emit("unzip-start", format!("{}", name));
    let res = tauri::async_runtime::spawn_blocking(move || {
        let file = File::open(zip_path)?;
        let mut archive = ZipArchive::new(BufReader::new(file))?;
        let total = archive.len();

        for i in 0..total {
            let mut entry = archive.by_index(i)?;
            let entry_name = entry.name();

            if should_skip(entry_name) {
                continue;
            }

            let outpath = out_dir.join(entry_name);
            if !outpath.starts_with(&out_dir) {
                return Err(ZipError::InvalidArchive("Path traversal detected".into()));
            }

            if entry.is_dir() {
                create_dir_all(&outpath)?;

                #[cfg(unix)]
                if let Some(mode) = entry.unix_mode() {
                    std::fs::set_permissions(&outpath, std::fs::Permissions::from_mode(mode))?;
                }
            } else {
                if let Some(parent) = outpath.parent() {
                    create_dir_all(parent)?;
                }

                let mut outfile = File::create(&outpath)?;
                copy(&mut entry, &mut outfile)?;

                #[cfg(unix)]
                if let Some(mode) = entry.unix_mode() {
                    std::fs::set_permissions(&outpath, std::fs::Permissions::from_mode(mode))?;
                }
            }

            let _ = app.emit("unzip-progress", format!("{}:{}:{}", name, i + 1, total));
        }

        Ok::<(), zip::result::ZipError>(())
    })
    .await;

    match res {
        Ok(Ok(())) => "1".into(),
        _ => "-1".into(),
    }
}

#[tauri::command]
fn folder_size(app: AppHandle, version: String) -> String {
    let path = match app.path().app_local_data_dir() {
        Ok(p) => p.join("game").join(&version),
        Err(_) => return "-1".to_string(),
    };
    fn inner(path: &Path) -> u64 {
        let mut size = 0;
        if let Ok(entries) = fs::read_dir(path) {
            for entry in entries.flatten() {
                if let Ok(metadata) = entry.metadata() {
                    if metadata.is_file() {
                        size += metadata.len();
                    } else if metadata.is_dir() {
                        size += inner(&entry.path());
                    }
                }
            }
        }
        size
    }

    let p = Path::new(&path);
    if p.exists() && p.is_dir() {
        inner(p).to_string()
    } else {
        "-1".to_string()
    }
}

#[tauri::command]
async fn download(
    app: AppHandle,
    url: String,
    name: String,
    hash: String,
    download_type: i8,
) -> String {
    println!("[download] Starting download for '{}' from '{}'", name, url);
    let _ = app.emit("download-start", format!("{}", name));
    let window = app.get_webview_window("main").expect("main window missing");

    let downloads_path = match app.path().app_local_data_dir() {
        Ok(p) => p.join("downloads"),
        Err(e) => {
            println!(
                "[download] ERROR: Failed to resolve app_local_data_dir: {}",
                e
            );
            let _ = &app.emit("download-stop", format!("{}", name));
            return "-1".to_string();
        }
    };
    let game_path = match app.path().app_local_data_dir() {
        Ok(p) => p.join("game"),
        Err(e) => {
            println!("[download] ERROR: Failed to resolve game path: {}", e);
            let _ = &app.emit("download-stop", format!("{}", name));
            return "-1".to_string();
        }
    };

    let download_part_path = downloads_path.join(format!("{}.part", name));
    let download_zip_path = downloads_path.join(format!("{}.zip", name));
    println!("[download] Part file: {:?}", download_part_path);
    println!("[download] Zip file:  {:?}", download_zip_path);

    let _ = tokio::fs::create_dir_all(&downloads_path).await;

    let resume_from: u64 = match tokio::fs::metadata(&download_part_path).await {
        Ok(meta) => {
            let size = meta.len();
            println!(
                "[download] Found existing .part file ({} bytes), will attempt to resume",
                size
            );
            size
        }
        Err(_) => 0,
    };

    let client = reqwest::Client::new();
    let mut request = client.get(&url);
    if resume_from > 0 {
        request = request.header("Range", format!("bytes={}-", resume_from));
        println!("[download] Requesting range: bytes={}-", resume_from);
    }

    let resp = match request.send().await {
        Ok(r) => {
            println!("[download] HTTP request succeeded, status: {}", r.status());
            r
        }
        Err(e) => {
            println!("[download] ERROR: HTTP request failed: {:?}", e);
            let _ = &app.emit("download-stop", format!("{}", name));
            return "-1".to_string();
        }
    };

    let status = resp.status();

    let actual_resume_from = if resume_from > 0 && status == reqwest::StatusCode::OK {
        println!(
            "[download] Server does not support range requests (got 200), restarting from scratch"
        );
        let _ = tokio::fs::remove_file(&download_part_path).await;
        0
    } else if resume_from > 0 && status == reqwest::StatusCode::PARTIAL_CONTENT {
        println!("[download] Server accepted range request (206 Partial Content)");
        resume_from
    } else if resume_from > 0 {
        println!(
            "[download] Unexpected status {} while resuming, restarting",
            status
        );
        let _ = tokio::fs::remove_file(&download_part_path).await;
        0
    } else {
        0
    };

    let remaining_size = resp.content_length().unwrap_or(0);
    let total_size = actual_resume_from + remaining_size;
    println!(
        "[download] Resume offset: {} bytes | Remaining: {} bytes | Total: {} bytes ({:.2} MB)",
        actual_resume_from,
        remaining_size,
        total_size,
        total_size as f64 / 1_048_576.0
    );
    let _ = app.emit("download-size", format!("{}:{}", &name, &total_size));

    let mut file = if actual_resume_from > 0 {
        match tokio::fs::OpenOptions::new()
            .append(true)
            .open(&download_part_path)
            .await
        {
            Ok(f) => {
                println!("[download] Opened .part file in append mode for resume");
                f
            }
            Err(e) => {
                println!(
                    "[download] ERROR: Failed to open .part file for append: {}",
                    e
                );
                let _ = &app.emit("download-stop", format!("{}", name));
                return "-1".to_string();
            }
        }
    } else {
        if download_type == 0 {
            if let Ok(true) = tokio::fs::try_exists(&game_path.join(&name)).await {
                println!(
                    "[download] Existing game dir found, removing: {:?}",
                    game_path.join(&name)
                );
                let _ = tokio::fs::remove_dir_all(&game_path.join(&name)).await;
            }
            let _ = tokio::fs::create_dir_all(&game_path.join(&name)).await;
        }

        match tokio::fs::File::create(&download_part_path).await {
            Ok(f) => {
                println!("[download] Created new .part file");
                f
            }
            Err(e) => {
                println!("[download] ERROR: Failed to create .part file: {}", e);
                let _ = &app.emit("download-stop", format!("{}", name));
                return "-1".to_string();
            }
        }
    };

    let mut downloaded: u64 = actual_resume_from;
    let mut stream = resp.bytes_stream();

    let start = Instant::now();
    let mut chunk_count: u64 = 0;

    while let Ok(Some(chunk_result)) = timeout(Duration::from_secs(5), stream.next()).await {
        if is_cancelled(&name) {
            println!("[download] Cancelled '{}' during chunk loop", name);
            cancel_map().remove(&name);
            let _ = window.set_progress_bar(ProgressBarState {
                status: Some(ProgressBarStatus::None),
                progress: Some(0),
            });
            return "0".to_string();
        }

        let chunk = match chunk_result {
            Ok(c) => c,
            Err(e) => {
                println!(
                    "[download] ERROR: Failed to read chunk #{}: {}",
                    chunk_count, e
                );
                let _ = &app.emit("download-stop", format!("{}", name));
                return "-1".to_string();
            }
        };

        chunk_count += 1;

        if let Err(e) = file.write_all(&chunk).await {
            println!(
                "[download] ERROR: Failed to write chunk #{} to disk: {}",
                chunk_count, e
            );
            let _ = &app.emit("download-stop", format!("{}", name));
            return "-1".to_string();
        }

        downloaded += chunk.len() as u64;

        let progress = if total_size > 0 {
            ((downloaded as f64) / (total_size as f64)) * 100.0
        } else {
            0.0
        };

        let session_bytes = downloaded - actual_resume_from;
        let elapsed_secs = start.elapsed().as_secs_f64();
        let speed = if elapsed_secs > 0.0 {
            session_bytes as f64 / elapsed_secs
        } else {
            0.0
        };
        let eta_secs = if total_size > downloaded && speed > 0.0 {
            (total_size - downloaded) as f64 / speed
        } else {
            0.0
        };

        if chunk_count % 50 == 0 || downloaded == total_size {
            println!(
                "[download] [{:.1}%] {:.2} MB / {:.2} MB | Speed: {:.1} KB/s | ETA: {:.1}s | Chunks: {}",
                progress,
                downloaded as f64 / 1_048_576.0,
                total_size as f64 / 1_048_576.0,
                speed / 1024.0,
                eta_secs,
                chunk_count,
            );
            let _ = window.set_progress_bar(ProgressBarState {
                status: Some(ProgressBarStatus::Normal),
                progress: Some(progress as u64),
            });
        }

        let _ = app.emit(
            "download-progress",
            format!(
                "{}:{:.8}:{}:{}:{:.2}",
                &name, progress, downloaded, speed, eta_secs
            ),
        );
    }

    if total_size > 0 && downloaded < total_size {
        println!(
            "[download] ERROR: Download incomplete — got {} of {} bytes ({:.1}% complete)",
            downloaded,
            total_size,
            (downloaded as f64 / total_size as f64) * 100.0
        );
        let _ = window.set_progress_bar(ProgressBarState {
            status: Some(ProgressBarStatus::None),
            progress: Some(0),
        });
        return "-1".to_string();
    }

    println!(
        "[download] Download complete: {} bytes total in {:.2}s (this session)",
        downloaded,
        start.elapsed().as_secs_f64()
    );
    println!("[download] Verifying SHA-512 hash...");
    let _ = app.emit("download-hash-checking", format!("{}", &name));

    let download_hash = {
        let mut file = match tokio::fs::File::open(&download_part_path).await {
            Ok(f) => f,
            Err(e) => {
                println!(
                    "[download] ERROR: Failed to open .part file for hashing: {}",
                    e
                );
                return "-1".to_string();
            }
        };
        let mut hasher = Sha512::new();
        let mut bytes_hashed: u64 = 0;
        let mut buffer = [0u8; 8192];
        loop {
            let bytes_read = match file.read(&mut buffer).await {
                Ok(n) => n,
                Err(e) => {
                    println!(
                        "[download] ERROR: Failed to read file during hashing: {}",
                        e
                    );
                    return "-1".to_string();
                }
            };
            if bytes_read == 0 {
                break;
            }
            hasher.update(&buffer[..bytes_read]);
            bytes_hashed += bytes_read as u64;
        }
        drop(file);
        println!("[download] Hashed {} bytes", bytes_hashed);
        format!("{:x}", hasher.finalize())
    };

    println!("[download] Expected hash: {}", hash);
    println!("[download] Computed hash: {}", download_hash);

    if hash != download_hash {
        println!("[download] ERROR: Hash mismatch! Deleting corrupt .part file.");
        let _ = tokio::fs::remove_file(&download_part_path).await;
        let _ = window.set_progress_bar(ProgressBarState {
            status: Some(ProgressBarStatus::None),
            progress: Some(0),
        });
        return "-1".to_string();
    }

    println!("[download] Hash verified OK");
    println!("[download] Renaming .part -> .zip: {:?}", download_zip_path);
    if let Err(e) = tokio::fs::rename(&download_part_path, &download_zip_path).await {
        println!("[download] ERROR: Failed to rename .part to .zip: {}", e);
        let _ = window.set_progress_bar(ProgressBarState {
            status: Some(ProgressBarStatus::None),
            progress: Some(0),
        });
        return "-1".to_string();
    }

    let _ = tokio::fs::create_dir_all(&game_path.join(&name)).await;

    println!("[download] Unzipping to: {:?}", game_path.join(&name));
    let unzip_res = unzip_to_dir(
        app.clone(),
        download_zip_path.clone(),
        if download_type == 2 {
            game_path.join(&name).join("BepInEx").join("plugins")
        } else {
            game_path.join(&name)
        },
        name.clone(),
    )
    .await;

    println!("[download] Removing zip file: {:?}", download_zip_path);
    let _ = tokio::fs::remove_file(&download_zip_path).await;

    if unzip_res == "-1" {
        println!("[download] ERROR: Unzip failed for '{}'", name);
        let _ = window.set_progress_bar(ProgressBarState {
            status: Some(ProgressBarStatus::None),
            progress: Some(0),
        });
        return "-1".to_string();
    }

    println!(
        "[download] SUCCESS: '{}' downloaded, verified, and extracted",
        &name
    );
    let _ = window.set_progress_bar(ProgressBarState {
        status: Some(ProgressBarStatus::None),
        progress: Some(0),
    });
    "1".to_string()
}

#[allow(unused_variables)]
#[tauri::command]
fn launch_game(
    app: AppHandle,
    name: String,
    executable: String,
    display_name: String,
    use_wine: bool,
    wine_command: String,
) {
    let game_folder = match app.path().app_local_data_dir() {
        Ok(p) => p.join("game").join(&name),
        Err(_) => return,
    };
    if !game_folder.exists() {
        return;
    }

    let exe_path = game_folder.join(&executable);

    //if already running on macos, it'll auto take the user to that proccess
    #[cfg(any(target_os = "windows", target_os = "linux"))]
    {
        use tauri_plugin_dialog::DialogExt;
        use tauri_plugin_dialog::MessageDialogKind;

        if !use_wine && is_running_by_path(&exe_path) {
            app.dialog()
                .message(format!(
                    "{} is already running, if this doesn't seem true, try to kill the proccess.",
                    display_name
                ))
                .kind(MessageDialogKind::Error)
                .title("Game already running")
                .show(|_| {});
            return;
        }
    }

    #[cfg(target_os = "linux")]
    {
        if use_wine {
            let quoted_path = format!("\"{}\"", exe_path.to_string_lossy());
            let cmd = wine_command.replace("%path%", &quoted_path);

            if let Err(_) = Command::new("bash")
                .arg("-c")
                .arg(cmd)
                .current_dir(&game_folder)
                .spawn()
            {
                eprintln!("Failed to launch game with Wine");
            }

            return;
        }
    }

    if platform() == "macos" {
        if let Err(_) = Command::new("open")
            .arg(&executable)
            .current_dir(&game_folder)
            .spawn()
        {
            eprintln!("Failed to launch game on macOS");
        }
    } else {
        if let Err(_) = Command::new(&exe_path).current_dir(&game_folder).spawn() {
            eprintln!("Failed to launch game");
        }
    }
}

#[tauri::command]
fn verify_signature(body: String, signature: String, public_key: String) -> bool {
    let Ok(pem) = general_purpose::STANDARD.decode(public_key) else {
        return false;
    };
    let Ok(pubkey) = PKey::public_key_from_pem(&pem) else {
        return false;
    };
    let Ok(sig) = general_purpose::STANDARD.decode(signature) else {
        return false;
    };

    let mut verifier = match Verifier::new_without_digest(&pubkey) {
        Ok(v) => v,
        Err(_) => return false,
    };

    verifier
        .verify_oneshot(&sig, body.as_bytes())
        .unwrap_or(false)
}

#[tauri::command]
async fn cancel_download(name: String) {
    println!("[cancel_download] Cancellation requested for '{}'", name);
    cancel_map().insert(name.clone(), true);
}

#[cfg_attr(mobile, tauri::mobile_entry_point)]
pub fn run() {
    #[allow(unused_variables)]
    tauri::Builder::default()
        .plugin(tauri_plugin_http::init())
        .plugin(
            tauri_plugin_prevent_default::Builder::new()
                .with_flags(
                    Flags::FIND
                        | Flags::CARET_BROWSING
                        | Flags::DEV_TOOLS
                        | Flags::DOWNLOADS
                        | Flags::FOCUS_MOVE
                        | Flags::RELOAD
                        | Flags::SOURCE
                        | Flags::OPEN
                        | Flags::PRINT
                        | Flags::CONTEXT_MENU,
                )
                .build(),
        )
        .plugin(tauri_plugin_window_state::Builder::new().build())
        .plugin(tauri_plugin_clipboard_manager::init())
        .plugin(tauri_plugin_notification::init())
        .plugin(tauri_plugin_single_instance::init(|app, _args, _cwd| {
            if let Some(window) = app.get_webview_window("main") {
                let _ = window.set_focus();
            }
        }))
        .plugin(tauri_plugin_dialog::init())
        .plugin(tauri_plugin_fs::init())
        .plugin(tauri_plugin_decorum::init())
        .plugin(tauri_plugin_os::init())
        .plugin(tauri_plugin_opener::init())
        .invoke_handler(tauri::generate_handler![
            download,
            launch_game,
            folder_size,
            verify_signature,
            cancel_download
        ])
        .setup(|app| {
            #[cfg(target_os = "windows")]
            {
                use tauri_plugin_decorum::WebviewWindowExt;
                if let Some(main_window) = app.get_webview_window("main") {
                    if let Err(e) = main_window.create_overlay_titlebar() {
                        eprintln!("Failed to create overlay titlebar: {:?}", e);
                    }
                }
            }
            Ok(())
        })
        .run(tauri::generate_context!())
        .expect("error while running tauri application");
}