//! Downloads the onionperf analysis file from date in in format of **YYYY-MM-DD**.
//! Eg(2023-10-21)
//!
//! It generates the URL
//! https://op-de7a.onionperf.torproject.net:8443/htdocs/2023-08-05.onionperf.analysis.json.xz
//! **or**
//! https://op-de7a.onionperf.torproject.net:8443/2023-08-05.onionperf.analysis.json.xz
//!
//! Only one of the two url works

use super::model::OnionPerfAnalysis;
use super::utils::decompress_xz;
use chrono::{DateTime, Datelike, Days, Utc};
use log::error;
use reqwest::{StatusCode, Url};
use std::sync::Arc;
use std::time::Duration;
use tokio::select;
use tokio::sync::mpsc::UnboundedSender;
use tokio::sync::{oneshot, Mutex};
use tokio::time::sleep;
use tokio_stream::wrappers::UnboundedReceiverStream;

// The paths to lookup for onionperfs analysis file
const ONION_PERF_ANALYAIS_PATHS: [&str; 2] = ["/htdocs/", "/"];

// The interval (hour) to recheck for existence of the file
const RECHECK_INTERVAL: u64 = 2;

/// The client to connect to a OnionPerfRunner Host and get the most recent OnionPerf Analysis file
/// at certain intervals
pub struct OnionPerfRunner {
    /// Name of the host **Eg. "op-de7a"**
    pub host_name: String,

    /// The UTC time(only day) at which the OnionPerf analysis file have been already checked and need not to be checked again
    already_checked: Arc<Mutex<Vec<DateTime<Utc>>>>,

    /// The sender half to send the OnionPerfAnalysis files
    onionperf_analysis_sender: UnboundedSender<OnionPerfAnalysis>,

    /// The receiver stream to receive the OnionPerfAnalysis files
    pub onionperf_analysis_receiver_stream: Arc<Mutex<UnboundedReceiverStream<OnionPerfAnalysis>>>,

    // The sender to terminate a running OnionPerfRunner
    onionperf_terminate_sender: Mutex<Option<oneshot::Sender<()>>>,

    // The receiver to receive signal to terminate a running OnionPerfRunner
    onionperf_terminate_receiver: Mutex<oneshot::Receiver<()>>,
}

impl OnionPerfRunner {
    /// Create a new client to get data from OnionPerfRunner Host
    pub fn new<T: AsRef<str>>(host_name: T) -> Self {
        let already_checked = Arc::default();
        let (sd, rv) = tokio::sync::mpsc::unbounded_channel::<OnionPerfAnalysis>();
        let onionperf_analysis_receiver_stream = Arc::new(Mutex::new(UnboundedReceiverStream::new(rv)));
        let (onionperf_terminate_sender, onionperf_terminate_receiver) = oneshot::channel();
        let onionperf_terminate_receiver = Mutex::new(onionperf_terminate_receiver);
        let onionperf_terminate_sender = Mutex::new(Some(onionperf_terminate_sender));

        OnionPerfRunner {
            host_name: String::from(host_name.as_ref()),
            onionperf_analysis_sender: sd,
            onionperf_analysis_receiver_stream,
            already_checked,
            onionperf_terminate_sender,
            onionperf_terminate_receiver,
        }
    }

    async fn process_one_try(
        &self,
        current_utc_time: &mut DateTime<Utc>,
        current_utc_date: &str,
        tries: &mut i32,
        onionperf_analysis_file: Result<Vec<u8>, OnionPerfRunnerError>,
    ) -> OneTryResult {
        match onionperf_analysis_file {
            Ok(onionperf_analysis_file_compressed) => match decompress_xz(&onionperf_analysis_file_compressed).await {
                Ok(onionperf_analysis_file_decompressed) => {
                    // Parsing the OnionPerf analysis file
                    let onionperf_analysis = serde_json::from_slice::<OnionPerfAnalysis>(&onionperf_analysis_file_decompressed[..]);

                    match onionperf_analysis {
                        Ok(mut v) => {
                            v.time = Some(current_utc_date.to_owned());
                            let _ = self.onionperf_analysis_sender.send(v);

                            let mut already_checked: tokio::sync::MutexGuard<'_, Vec<DateTime<Utc>>> = self.already_checked.lock().await;
                            already_checked.push(*current_utc_time);
                            return OneTryResult::ReceivedAndParsed;
                        }
                        Err(e) => {
                            // If there was parsing issue we'll download again
                            log::error!("There was error on parsing OnionPerfAnalysis JSON file at tries no {tries} {:?}", e);
                            *tries += 1;
                        }
                    }
                }
                Err(e) => {
                    log::error!(
                        "There was error on decompressing the xz compressed OnionPerfAnalysis JSON file aat tries no {tries} {:?}",
                        e
                    );
                    *tries += 1;
                    // If there was decompression issue then we'll download the file
                    // with same date
                }
            },
            Err(onionperfrunner_error) => {
                match onionperfrunner_error {
                    // Reasons :
                    // - We're checking the wrong date(usually too ahead of time), for that we can reduce the day by 1 (TODO : add a guard on how far back we can go by days)
                    // - The file has (actually not been published, how do we determine that?) and we need to wait
                    // for the files by the onionperf server to publish(TODO: Imp!!!!)
                    OnionPerfRunnerError::OnionPerfAnalysisFileNotFound => {
                        log::warn!(
                            "The OnionPerfAnalysis file was not found, it mostly due to file not being available at the link at this time 
                                    and server throwing 404 errors"
                        );

                        *current_utc_time = current_utc_time.checked_sub_days(Days::new(1)).unwrap();
                        let checked = {
                            let already_checked = self.already_checked.lock().await;

                            // We don't try to download again if we have already downloaded the ones whose "day" matches
                            already_checked
                                .iter()
                                .any(|already_checked_utc_time| already_checked_utc_time.day() == current_utc_time.day())
                        };

                        // If the date has been checked then we go back to where we were
                        // left at before
                        if checked {
                            *current_utc_time = current_utc_time.checked_add_days(Days::new(1)).unwrap();
                        }
                        return OneTryResult::NotFound;
                    }
                    OnionPerfRunnerError::OnionPerfAnalysisNetworkError => {
                        log::error!("Network error has occured");
                    }
                }
            }
        };
        OneTryResult::Continue
    }

    // Start downloading data from the OnionPerfRunner hosts
    pub async fn start(&self) {
        let mut current_utc_time = Utc::now();
        let mut terminate_receiver_guard = self.onionperf_terminate_receiver.lock().await;
        'onionperf_running_main_loop: loop {
            let checked = {
                let already_checked = self.already_checked.lock().await;

                // We don't try to download again if we have already downloaded the ones whose "day" matches
                already_checked
                    .iter()
                    .any(|already_checked_utc_time| already_checked_utc_time.day() == current_utc_time.day())
            };

            if !checked {
                let current_utc_date = self.generate_date(current_utc_time);
                let mut tries = 0;

                // Loop for retrying the failed item due to decompresssion issue or parsing issue
                'decompression_parsing_error_try_iteration: loop {
                    let onionpef_analysis_file_future = self.download_onionperf_analysis_file(current_utc_date.clone());
                    let onionperf_analysis_file;

                    // Terminate the main loop if received stop signal
                    select! {
                        file = onionpef_analysis_file_future => {
                            onionperf_analysis_file = file;
                        }
                        _ = &mut *terminate_receiver_guard => {
                            break 'onionperf_running_main_loop;
                        }
                    }

                    let res = self
                        .process_one_try(&mut current_utc_time, &current_utc_date, &mut tries, onionperf_analysis_file)
                        .await;

                    if let OneTryResult::NotFound | OneTryResult::ReceivedAndParsed = res {
                        break 'decompression_parsing_error_try_iteration;
                    }

                    // We'll make max of 5 iterations
                    if tries >= 5 {
                        // Terminate the main loop if received stop signal while wating
                        tokio::select! {
                            _ = &mut *terminate_receiver_guard => {
                                break 'onionperf_running_main_loop;
                            }
                            _ = sleep(Duration::from_secs(RECHECK_INTERVAL * 60 * 60)) => {
                                break 'decompression_parsing_error_try_iteration;
                            }
                        }
                    }
                }
            } else {
                // Sleep for 2 hours if the latest UTC Time data was also already fetched
                // Terminate the main loop if received stop signal while wating
                tokio::select! {
                    _ = &mut *terminate_receiver_guard => {
                        break 'onionperf_running_main_loop;
                    }
                    _ = sleep(Duration::from_secs(RECHECK_INTERVAL * 60 * 60)) => ()
                }

                // We'll increase the time by 1 day, because the current date has been already
                // checked
                current_utc_time = current_utc_time.checked_add_days(Days::new(1)).unwrap();
            }
        }
    }

    /// Stop the running loop in start().
    /// If a analysis file has already download, it will stop after the current process has been down.
    /// It will stop immediately if you try to start again after stop.
    /// The runner will do nothing if you start after stop.
    pub async fn stop(&self) {
        let mut terminate_sender_guard = self.onionperf_terminate_sender.lock().await;
        if let Some(sender) = (*terminate_sender_guard).take() {
            let sd_res = sender.send(());
            if let Err(e) = sd_res {
                error!("Error occurred when sending OnionPerfRunner stop signal. {:?}", e);
            }
        }
    }

    /// Downloads and decompresses the onionperf analysis file that's in ".xz" form
    async fn download_onionperf_analysis_file(&self, date: String) -> Result<Vec<u8>, OnionPerfRunnerError> {
        let (url_1, url_2) = self.generate_onionperf_analysis_urls(date);

        let reqwest_client = reqwest::Client::new();

        let resp_1 = reqwest_client.get(url_1).send().await;
        let resp_2 = reqwest_client.get(url_2).send().await;

        if let Ok(resp) = resp_1 {
            if resp.status() == StatusCode::OK {
                let data = resp.bytes().await.unwrap().into();
                return Ok(data);
            }
        }

        match resp_2 {
            Ok(resp) => {
                if resp.status() == StatusCode::OK {
                    let data = resp.bytes().await.unwrap().into();
                    Ok(data)
                } else {
                    Err(OnionPerfRunnerError::OnionPerfAnalysisFileNotFound)
                }
            }
            Err(_) => {
                // TODO : LOg error
                Err(OnionPerfRunnerError::OnionPerfAnalysisNetworkError)
            }
        }
    }

    /// The given UTC time in DATE format of "YYYY-MM-DD". Eg(2023-10-21)
    fn generate_date(&self, time: DateTime<Utc>) -> String {
        let year = time.year();
        let month = time.month();
        let day = time.day();

        let date = format!("{year}-{month:02}-{day:02}");
        date
    }

    /// Generate URLs for downloading the OnionPerf analysis file according to the current UTC date
    fn generate_onionperf_analysis_urls(&self, date: String) -> (Url, Url) {
        let (url_1, url_2) = {
            let url_1 = format!(
                "https://{}.onionperf.torproject.net:8443{}{}",
                self.host_name,
                ONION_PERF_ANALYAIS_PATHS[0],
                format_args!("{}.onionperf.analysis.json.xz", date)
            );
            let url_2 = format!(
                "https://{}.onionperf.torproject.net:8443{}{}",
                self.host_name,
                ONION_PERF_ANALYAIS_PATHS[1],
                format_args!("{}.onionperf.analysis.json.xz", date)
            );
            log::debug!("Trying to download onionperf analysis either from {url_1} or {url_2}");

            (Url::parse(&url_1), Url::parse(&url_2))
        };

        (url_1.unwrap(), url_2.unwrap())
    }
}

#[derive(Debug, thiserror::Error)]
enum OnionPerfRunnerError {
    #[error("The onion perf analysis file could not found at both links")]
    OnionPerfAnalysisFileNotFound,

    #[error("Can't connect to both links")]
    OnionPerfAnalysisNetworkError,
}

#[derive(Debug)]
enum OneTryResult {
    Continue,
    ReceivedAndParsed,
    NotFound,
}

#[cfg(test)]
mod tests {
    use super::OnionPerfRunner;
    use crate::runner::OneTryResult;
    use chrono::{TimeZone, Utc};
    use std::{sync::Arc, time::Duration};
    use tokio::{
        sync::oneshot,
        time::{self, timeout},
    };
    use tokio_stream::StreamExt;

    #[tokio::test]
    async fn test_received_and_parsed() {
        let runner = OnionPerfRunner::new("op-de8a");
        let mut utc_time = Utc.with_ymd_and_hms(2025, 3, 31, 0, 0, 0).unwrap();
        let utc_date = runner.generate_date(utc_time);
        let mut tries = 0;
        let onionperf_analysis_file = runner.download_onionperf_analysis_file(utc_date.clone()).await;
        assert!(onionperf_analysis_file.is_ok(), "Failed to download the analysis file.");
        let res = runner
            .process_one_try(&mut utc_time, &utc_date, &mut tries, onionperf_analysis_file)
            .await;
        assert_eq!(tries, 0, "Unexpected tries count change. Expected: 0, Actual: {}", tries);
        assert!(
            matches!(res, OneTryResult::ReceivedAndParsed),
            "Failed to receive or parse. Result: {:?}",
            res
        );
        let mut rv = runner.onionperf_analysis_receiver_stream.lock().await;
        let mut has_result = false;
        tokio::select! {
            _ = (*rv).next() => has_result = true,
            _ = time::sleep(Duration::from_secs(1)) => ()
        }
        assert!(has_result, "No parsed analysis in stream.");
    }

    #[tokio::test]
    async fn test_not_found() {
        let runner = OnionPerfRunner::new("op-de8a");
        let mut utc_time = Utc.with_ymd_and_hms(2077, 4, 1, 0, 0, 0).unwrap();
        let utc_date = runner.generate_date(utc_time);
        let mut tries = 0;
        let onionperf_analysis_file = runner.download_onionperf_analysis_file(utc_date.clone()).await;
        let res = runner
            .process_one_try(&mut utc_time, &utc_date, &mut tries, onionperf_analysis_file)
            .await;
        assert_eq!(tries, 0, "Unexpected tries count change. Expected: 0, Actual: {}", tries);
        assert_eq!(
            utc_time,
            Utc.with_ymd_and_hms(2077, 3, 31, 0, 0, 0).unwrap(),
            "Time didn't sub a day. Expected: 2077-03-31, Actual: {}",
            utc_time.format("%Y-%m-%d")
        );
        assert!(matches!(res, OneTryResult::NotFound), "Expected NotFound result. Actual: {:?}", res);
    }

    #[tokio::test]
    #[should_panic]
    async fn test_sleeping() {
        let runner = OnionPerfRunner::new("op-de8a");
        let utc_time = Utc::now();
        // Drop the MutexGuard after modified already_checked.
        {
            let mut checked_guard = runner.already_checked.lock().await;
            (*checked_guard).push(utc_time);
        }
        timeout(Duration::from_secs(30), async move {
            runner.start().await;
        })
        .await
        .unwrap();
    }

    #[tokio::test]
    async fn test_stop() {
        let runner = Arc::new(OnionPerfRunner::new("op-de8a"));
        let utc_time = Utc::now();
        // Drop the MutexGuard after modified already_checked.
        {
            let mut checked_guard = runner.already_checked.lock().await;
            (*checked_guard).push(utc_time);
        }
        let runner_cloned = runner.clone();
        let (stopped, rx) = oneshot::channel();
        let handle = tokio::spawn(async move {
            runner_cloned.start().await;
            stopped.send(()).unwrap();
        });
        runner.stop().await;
        timeout(Duration::from_secs(30), async move {
            match rx.await {
                Ok(_) => (),
                Err(_) => panic!(),
            }
            handle.await.unwrap();
        })
        .await
        .unwrap();
    }
}