use std::path::Path;
use std::process::exit;
use clap::{ App, Arg, ArgGroup, crate_version };
use tokio::sync::mpsc;
use futures::future::join_all;
use std::io::BufRead;
use std::time::SystemTime;

use dlreport::{ DlReport, DlStatus, DlReporter };
use errors::ResBE;

mod zippy;
mod download;
mod errors;
mod dlreport;


#[derive(Clone, Debug)]
enum CLIAction {
    DownloadUrl(String),
    ResolveZippyUrl(String),
    UrlList(String),
    None
}

#[derive(Clone, Debug)]
struct CLIArguments {
    outdir: String,
    into_file: Option<String>,
    file_count: u32,
    conn_count: u32,
    zippy: bool,
    action: CLIAction,
    urls: Vec<String>
}


#[tokio::main]
async fn main() -> ResBE<()> {

    let arguments = App::new("FFDL - Fast File Downloader")
        .version(crate_version!())
        .about("Download files fast")
        .arg(
            Arg::with_name("outdir")
                .short("o")
                .long("outdir")
                .value_name("OUTPUT DIR")
                .takes_value(true)
                .help("Set the output directory. The directory will be created \
                        if it doesn't exit yet")
        )
        .arg(
            Arg::with_name("into_file")
                .short("i")
                .long("into-file")
                .value_name("FILENAME")
                .takes_value(true)
                .requires("download")
                .help("Force filename. This only works for single file downloads")
        )
        .arg(
            Arg::with_name("file_count")
                .short("n")
                .long("num-files")
                .value_name("NUMBER OF CONCURRENT FILE DOWNLOADS")
                .takes_value(true)
                .help("Specify the number concurrent file downloads")
        )
        .arg(
            Arg::with_name("conn_count")
                .short("c")
                .long("connections")
                .value_name("NUMBER OF CONNECTIONS")
                .takes_value(true)
                .help("The number concurrent connections per file download. \
                        Downloads might fail when the number of connections is \
                        too high. Files started with multiple connections can't \
                        be continued. NOTE: This will likely cause IO \
                        bottlenecks on HDDs")
        )
        .arg(
            Arg::with_name("zippyshare")
                .short("z")
                .long("zippy")
                .takes_value(false)
                .help("The provided URLs are zippyshare URLs and need to be resolved")
        )
        .group(
            ArgGroup::with_name("action")
                .required(true)
        )
        .arg(
            Arg::with_name("listfile")
                .short("l")
                .long("listfile")
                .value_name("URL LIST")
                .takes_value(true)
                .group("action")
                .help("Download all files form the specified url list")
        )
        .arg(
            Arg::with_name("download")
                .short("d")
                .long("download")
                .value_name("URL")
                .takes_value(true)
                .group("action")
                .help("Download only the specified URL")
        )
        .arg(
            Arg::with_name("zippy-resolve")
                .long("zippy-resolve")
                .value_name("ZIPPYSHARE URL")
                .takes_value(true)
                .group("action")
                .help("Resolve the zippyshare url to real download url")
        )
        .get_matches();
    

    let outdir = arguments.value_of("outdir").unwrap_or("./").to_string();

    let into_file = arguments.value_of("into_file").map(String::from);

    let file_count = arguments.value_of("file_count").unwrap_or("1");

    let file_count: u32 = file_count.parse().unwrap_or_else(|_| {
        eprintln!("Invalid value for num-files: {}", file_count);
        exit(1);
    });
    
    if file_count <= 0 {
        eprintln!("Invalid value for num-files: {}", file_count);
        exit(1);
    }

    let conn_count = arguments.value_of("conn_count").unwrap_or("1");
    
    let conn_count: u32 = conn_count.parse().unwrap_or_else(|_| {
        eprintln!("Invalid value for connections: {}", conn_count);
        exit(1);
    });
    
    if conn_count <= 0 {
        eprintln!("Invalid value for connections: {}", conn_count);
        exit(1);
    }

    let is_zippy = arguments.is_present("zippyshare");


    let action = 
        if let Some(listfile) = arguments.value_of("listfile") { 
            CLIAction::UrlList (
                listfile.to_string()
            )
        } else if let Some(download_url) = arguments.value_of("download") { 
            CLIAction::DownloadUrl(
                download_url.to_string()
            )
        }  else if let Some(resolve_url) = arguments.value_of("zippy-resolve") { 
            CLIAction::ResolveZippyUrl(
                resolve_url.to_string()
            )
        } 
        else {
            CLIAction::None
        };
    

    let mut cli_args = CLIArguments {
        outdir: outdir,
        into_file: into_file,
        file_count: file_count,
        conn_count: conn_count,
        zippy: is_zippy,
        action: action,
        urls: Vec::new()
    };

    // Evaluate and execute the requested action. The 3 different actions are 
    // mutally exclusive, so only one of them will be executed

    match &cli_args.action {

        CLIAction::UrlList(listfile) => {

            let p_listfile = Path::new(listfile);

            if !p_listfile.is_file() {
                eprintln!("Listfile '{}' does not exist!", &listfile);
                exit(1);
            }
    
            let ifile = std::fs::File::open(p_listfile)?;
    
            cli_args.urls = std::io::BufReader::new(ifile)
                .lines()
                .map(|l| l.unwrap())
                .filter(|url| url.len() > 0 && !url.starts_with("#"))
                .collect();
        },

        CLIAction::DownloadUrl(url) => {
            cli_args.urls = vec![url.clone()];
        }

        CLIAction::ResolveZippyUrl(url) => {
            let resolved_url = zippy::resolve_link(url).await.unwrap_or_else(|_| {
                println!("Zippyshare link could not be resolved");
                exit(1);
            });

            println!("{}", resolved_url);
        },

        CLIAction::None => {
            eprintln!("No action selected. This should not happen");
            exit(1);
        }
        
    }

    download_multiple(cli_args).await

}

async fn download_multiple(cli_args: CLIArguments) -> ResBE<()> {
    let outdir = cli_args.outdir;
    let outdir = Path::new(&outdir);

    let file_count = cli_args.file_count;

    let zippy = cli_args.zippy;

    let conn_count = cli_args.conn_count;

    if !outdir.exists() {
        if let Err(_e) = std::fs::create_dir_all(outdir) {
            eprintln!("Error creating output directory '{}'", outdir.to_str().unwrap());
            exit(1);
        }
    }

    let t_start = SystemTime::now();

    let mut joiners = Vec::new();

    let (tx, rx) = mpsc::unbounded_channel::<DlReport>();

    for offset in 0 .. file_count {

        let urls: Vec<String> = cli_args.urls
            .iter()
            .enumerate()
            .filter(|(index, _)| (index) % file_count as usize == offset as usize)
            .map(|(_, v)| v.to_owned())
            .collect();
        
        let tx = tx.clone();
        let outdir = outdir.to_owned();
        let offset = offset;
        let arg_filename = cli_args.into_file.clone();

        joiners.push(tokio::task::spawn(async move {

            for (i, url) in urls.iter().enumerate() {

                let tx = tx.clone();

                // Recalculated index in the main url vector, used as id
                let global_url_index = i as u32 * file_count + offset;

                let rep = DlReporter::new(global_url_index, tx);

                let url = if zippy {
                    match zippy::resolve_link(&url).await {
                        Ok(url) => url,
                        Err(_e) => {
                            rep.send(
                                DlStatus::Message(format!("Zippyshare link could not be resolved: {}", url))
                            );
                            continue;
                        }
                    }
                } else {
                    url.to_string()
                };

                let file_name = arg_filename.clone().unwrap_or_else(|| download::url_to_filename(&url));


                let into_file = outdir.join(Path::new(&file_name))
                    .to_str().unwrap().to_string();
                let path_into_file = Path::new(&into_file);

                let (filesize, range_supported) = match download::http_get_filesize_and_range_support(&url).await {
                    Ok((filesize, range_supported)) => (filesize, range_supported),
                    Err(_e) => {
                        rep.send(
                            DlStatus::Message(format!("Error while querying metadata: {}", url))
                        );
                        continue;
                    }
                };
            
                // If file with same name is present locally, check filesize
                if path_into_file.exists() {

                    let local_filesize = std::fs::metadata(path_into_file).unwrap().len();
            
                    if filesize == local_filesize {
                        rep.send(DlStatus::Message(format!("Skipping file '{}': already present", &file_name)));
                        continue;
                    } else {
                        rep.send(DlStatus::Message(format!("Replacing file '{}': present but not completed", &file_name)));
                    }
                }

                if conn_count == 1 {
                    if let Err(_e) = download::download_feedback(&url, &into_file, rep.clone(), Some(filesize)).await {
                        rep.send(DlStatus::DoneErr {
                            filename: file_name.to_string()
                        });
                    }
                } else {
                    
                    if !range_supported {
                        rep.send(
                            DlStatus::Message(format!("Error Server does not support range header: {}", url))
                        );
                        continue;
                    }

                    if let Err(_e) = download::download_feedback_multi(&url, &into_file, rep.clone(), conn_count, Some(filesize)).await {
                        rep.send(DlStatus::DoneErr {
                            filename: file_name.to_string()
                        });
                    }
                };

            }
        }))

    }
    
    drop(tx);

    dlreport::watch_and_print_reports(rx).await?;

    join_all(joiners).await;

    println!("Total time: {}s", t_start.elapsed()?.as_secs());

    Ok(())
}