use std::ops::Deref;
use std::sync::Arc;
use std::sync::atomic::{AtomicBool, Ordering};
use std::thread;
use std::time::Duration;
use anyhow::{anyhow, Result};
use signal_hook::consts::{SIGINT, SIGTERM};
use tokio::fs::File;
use tokio::io::AsyncWriteExt;
use tokio::sync::mpsc;
use tokio::sync::oneshot;
use tokio::sync::mpsc::Sender;
use tokio::task::JoinHandle;
use signal_hook::iterator::Signals;
use log::{debug, error, info};
use tokio::time::{sleep, timeout};

fn setup_graceful_shutdown(cancelled: Arc<AtomicBool>) {
    thread::spawn(move || {
        let signals = Signals::new([SIGINT, SIGTERM]);
        match signals {
            Ok(mut signal_info) => {
                if signal_info.forever().next().is_some() {
                    info!("user request cancellation");
                    cancelled.store(true, Ordering::Relaxed);
                }
            }
            Err(error) => {
                error!("Failed to setup signal handler: {error}")
            }
        }
    });
}

async fn download_image(tx: Sender<Result<bytes::Bytes, anyhow::Error>>, url: &str) {
    info!("Downloading image for {}", url);
    let resp = reqwest::get(url)
        .await;
    if let Ok(resp) = resp {
        let image_bytes = resp.bytes().await;
        match image_bytes {
            Ok(data) => {
                tx.send(Ok(data)).await.expect("failed to send message");
            }
            Err(err) => {
                tx.send(Err(anyhow!("failed to get image data: {}", err))).await.expect("failed to send message");
            }
        }
    } else {
        tx.send(Err(anyhow!("failed to get response"))).await.expect("failed to send message");
    }
}

#[tokio::main]
async fn main() -> Result<()> {
    env_logger::init();

    let task_timeout = Duration::from_millis(500);

    let (tx, mut rx) = mpsc::channel(32);
    let cancelled = Arc::from(AtomicBool::new(false));
    setup_graceful_shutdown(cancelled.clone());

    let urls: Vec<&str> = vec![
        "https://images.unsplash.com/photo-1739117956532-8a37c76093dd?fm=jpg",
        "https://images.unsplash.com/photo-1735930371721-d1243e8122ab?fm=jpg",
        "https://images.unsplash.com/photo-1732204662871-f853329ce638?fm=jpg",
        "https://images.unsplash.com/photo-1712677925320-5f93d7f853f5?fm=jpg",
        "https://images.unsplash.com/photo-1712677925900-12574cb3cf15?fm=jpg",
        "https://images.unsplash.com/photo-1710436000845-bb707af976a6?fm=jpg",
        "https://images.unsplash.com/photo-1700386277812-5ff74eb03650?fm=jpg",
        "https://images.unsplash.com/photo-1700386277415-c9c5270ee8b8?fm=jpg",
        "https://images.unsplash.com/photo-1691947563165-28011f40d786?fm=jpg",
        "https://images.unsplash.com/photo-1691782359338-97fcbcce8ce8?fm=jpg"
    ];

    let mut handles: Vec<JoinHandle<()>> = Vec::new();
    for url in urls {
        let tx = tx.clone();
        let handle = tokio::spawn(async move {
            let timeout_status = timeout(task_timeout, download_image(tx, url)).await;
            debug!("timeout status = {:?} for url {}", timeout_status, url)
        });
        handles.push(handle);
    }


    let wait_cancelled = cancelled.clone();
    let wait_task = tokio::spawn(async move {
       for handle in handles {
           if wait_cancelled.load(Ordering::Relaxed) {
               handle.abort();
           } else {
               let _ = handle.await;
           }
       }
        drop(tx);
    });

    let mut counter = 1;
    while let Some(message) = rx.recv().await {
        if cancelled.load(Ordering::Relaxed) {
            break
        }

        if let Ok(image_bytes) = message {
            let file = File::create(format!("{}.jpg", counter)).await;
            if let Ok(mut file) = file {
                let _ = file.write_all(&image_bytes).await;
                info!("Wrote image {}", counter);
            } else {
                error!("Failed to write image {}", counter)
            }

            counter += 1;
        }
    }

    let _ = wait_task.await;
    Ok(())
}