use std::{
    collections::VecDeque, io::BufRead, path::Path, process::exit, sync::Arc, sync::Mutex,
    time::SystemTime,
};

use clap::Parser;
use futures::future::join_all;
use tokio::sync::mpsc;

use crate::{
    args::{CLIAction, CLIArgs},
    dlreport::{DlReport, DlReporter, DlStatus},
    errors::ResBE,
};

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

#[tokio::main]
async fn main() -> ResBE<()> {
    let args = CLIArgs::parse();

    let action = match (&args.listfile, &args.download, &args.zippy_resolve) {
        (Some(listfile), None, None) => CLIAction::UrlList(listfile.to_string()),
        (None, Some(url), None) => CLIAction::DownloadUrl(url.to_string()),
        (None, None, Some(zippy_url)) => CLIAction::ResolveZippyUrl(zippy_url.to_string()),
        _ => unreachable!(),
    };

    let urls = match action {
        CLIAction::DownloadUrl(url) => vec![url.clone()],
        CLIAction::UrlList(listfile) => read_urls_from_listfile(&listfile).await,
        CLIAction::ResolveZippyUrl(url) => resolve_zippy_url(&url).await,
    };

    download_multiple(args, urls).await
}

async fn resolve_zippy_url(url: &str) -> ! {
    let resolved_url = zippy::resolve_link(&url).await.unwrap_or_else(|_| {
        println!("Zippyshare link could not be resolved");
        exit(1);
    });

    println!("{}", resolved_url);
    exit(0);
}

async fn read_urls_from_listfile(listfile: &str) -> Vec<String> {
    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).unwrap();

    std::io::BufReader::new(ifile)
        .lines()
        .map(|l| l.unwrap())
        .filter(|url| url.len() > 0 && !url.starts_with("#"))
        .collect()
}

async fn download_multiple(cli_args: CLIArgs, raw_urls: Vec<String>) -> ResBE<()> {
    let outdir = cli_args.outdir;
    let outdir = Path::new(&outdir);

    let parallel_file_count = cli_args.file_count.get();
    let conn_count = cli_args.conn_count.get();
    let zippy = cli_args.zippy;

    let urls = Arc::new(Mutex::new(VecDeque::<(u32, String)>::new()));

    raw_urls.iter().enumerate().for_each(|(i, url)| {
        urls.lock().unwrap().push_back((i as u32, url.clone()));
    });

    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..parallel_file_count {
        let tx = tx.clone();
        let outdir = outdir.to_owned();
        let arg_filename = cli_args.into_file.clone();

        let urls = urls.clone();

        joiners.push(tokio::task::spawn(async move {
            loop {
                let (global_url_index, url) = match urls.lock().unwrap().pop_front() {
                    Some(it) => it,
                    None => break,
                };

                let tx = tx.clone();

                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
                        )));
                        rep.send(DlStatus::Skipped);
                        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, raw_urls.len() as i32).await?;

    join_all(joiners).await;

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

    Ok(())
}