use std::collections::HashSet;
use std::env;
use std::fmt::{Debug, Display};
use std::future::Future;
use std::num::NonZeroUsize;
use std::ops::ControlFlow;
use std::sync::Arc;
use std::time::{Duration, SystemTime, UNIX_EPOCH};

use anyhow::Context;
use camino::Utf8Path;
use futures_util::StreamExt;
use remote_storage::{
    DownloadError, DownloadOpts, GenericRemoteStorage, ListingMode, RemotePath,
    RemoteStorageConfig, RemoteStorageKind, S3Config,
};
use test_context::{AsyncTestContext, test_context};
use tokio::io::AsyncBufReadExt;
use tokio_util::sync::CancellationToken;
use tracing::info;

use crate::common::{download_to_vec, upload_stream};

mod common;

#[path = "common/tests.rs"]
mod tests_s3;

use common::{cleanup, ensure_logging_ready, upload_remote_data, upload_simple_remote_data};
use utils::backoff;

const ENABLE_REAL_S3_REMOTE_STORAGE_ENV_VAR_NAME: &str = "ENABLE_REAL_S3_REMOTE_STORAGE";
const BASE_PREFIX: &str = "test";

#[test_context(MaybeEnabledStorage)]
#[tokio::test]
async fn s3_time_travel_recovery_works(ctx: &mut MaybeEnabledStorage) -> anyhow::Result<()> {
    let ctx = match ctx {
        MaybeEnabledStorage::Enabled(ctx) => ctx,
        MaybeEnabledStorage::Disabled => return Ok(()),
    };
    // Our test depends on discrepancies in the clock between S3 and the environment the tests
    // run in. Therefore, wait a little bit before and after. The alternative would be
    // to take the time from S3 response headers.
    const WAIT_TIME: Duration = Duration::from_millis(3_000);

    async fn retry<T, O, F, E>(op: O) -> Result<T, E>
    where
        E: Display + Debug + 'static,
        O: FnMut() -> F,
        F: Future<Output = Result<T, E>>,
    {
        let warn_threshold = 3;
        let max_retries = 10;
        backoff::retry(
            op,
            |_e| false,
            warn_threshold,
            max_retries,
            "test retry",
            &CancellationToken::new(),
        )
        .await
        .expect("never cancelled")
    }

    async fn time_point() -> SystemTime {
        tokio::time::sleep(WAIT_TIME).await;
        let ret = SystemTime::now();
        tokio::time::sleep(WAIT_TIME).await;
        ret
    }

    async fn list_files(
        client: &Arc<GenericRemoteStorage>,
        cancel: &CancellationToken,
    ) -> anyhow::Result<HashSet<RemotePath>> {
        Ok(
            retry(|| client.list(None, ListingMode::NoDelimiter, None, cancel))
                .await
                .context("list root files failure")?
                .keys
                .into_iter()
                .map(|o| o.key)
                .collect::<HashSet<_>>(),
        )
    }

    let cancel = CancellationToken::new();

    let path1 = RemotePath::new(Utf8Path::new(format!("{}/path1", ctx.base_prefix).as_str()))
        .with_context(|| "RemotePath conversion")?;

    let path2 = RemotePath::new(Utf8Path::new(format!("{}/path2", ctx.base_prefix).as_str()))
        .with_context(|| "RemotePath conversion")?;

    let path3 = RemotePath::new(Utf8Path::new(format!("{}/path3", ctx.base_prefix).as_str()))
        .with_context(|| "RemotePath conversion")?;

    retry(|| {
        let (data, len) = upload_stream("remote blob data1".as_bytes().into());
        ctx.client.upload(data, len, &path1, None, &cancel)
    })
    .await?;

    let t0_files = list_files(&ctx.client, &cancel).await?;
    let t0 = time_point().await;
    println!("at t0: {t0_files:?}");

    let old_data = "remote blob data2";

    retry(|| {
        let (data, len) = upload_stream(old_data.as_bytes().into());
        ctx.client.upload(data, len, &path2, None, &cancel)
    })
    .await?;

    let t1_files = list_files(&ctx.client, &cancel).await?;
    let t1 = time_point().await;
    println!("at t1: {t1_files:?}");

    // A little check to ensure that our clock is not too far off from the S3 clock
    {
        let opts = DownloadOpts::default();
        let dl = retry(|| ctx.client.download(&path2, &opts, &cancel)).await?;
        let last_modified = dl.last_modified;
        let half_wt = WAIT_TIME.mul_f32(0.5);
        let t0_hwt = t0 + half_wt;
        let t1_hwt = t1 - half_wt;
        if !(t0_hwt..=t1_hwt).contains(&last_modified) {
            panic!(
                "last_modified={last_modified:?} is not between t0_hwt={t0_hwt:?} and t1_hwt={t1_hwt:?}. \
                This likely means a large lock discrepancy between S3 and the local clock."
            );
        }
    }

    retry(|| {
        let (data, len) = upload_stream("remote blob data3".as_bytes().into());
        ctx.client.upload(data, len, &path3, None, &cancel)
    })
    .await?;

    let new_data = "new remote blob data2";

    retry(|| {
        let (data, len) = upload_stream(new_data.as_bytes().into());
        ctx.client.upload(data, len, &path2, None, &cancel)
    })
    .await?;

    retry(|| ctx.client.delete(&path1, &cancel)).await?;
    let t2_files = list_files(&ctx.client, &cancel).await?;
    let t2 = time_point().await;
    println!("at t2: {t2_files:?}");

    // No changes after recovery to t2 (no-op)
    let t_final = time_point().await;
    ctx.client
        .time_travel_recover(None, t2, t_final, &cancel, None)
        .await?;
    let t2_files_recovered = list_files(&ctx.client, &cancel).await?;
    println!("after recovery to t2: {t2_files_recovered:?}");
    assert_eq!(t2_files, t2_files_recovered);
    let path2_recovered_t2 = download_to_vec(
        ctx.client
            .download(&path2, &DownloadOpts::default(), &cancel)
            .await?,
    )
    .await?;
    assert_eq!(path2_recovered_t2, new_data.as_bytes());

    // after recovery to t1: path1 is back, path2 has the old content
    let t_final = time_point().await;
    ctx.client
        .time_travel_recover(None, t1, t_final, &cancel, None)
        .await?;
    let t1_files_recovered = list_files(&ctx.client, &cancel).await?;
    println!("after recovery to t1: {t1_files_recovered:?}");
    assert_eq!(t1_files, t1_files_recovered);
    let path2_recovered_t1 = download_to_vec(
        ctx.client
            .download(&path2, &DownloadOpts::default(), &cancel)
            .await?,
    )
    .await?;
    assert_eq!(path2_recovered_t1, old_data.as_bytes());

    // after recovery to t0: everything is gone except for path1
    let t_final = time_point().await;
    ctx.client
        .time_travel_recover(None, t0, t_final, &cancel, None)
        .await?;
    let t0_files_recovered = list_files(&ctx.client, &cancel).await?;
    println!("after recovery to t0: {t0_files_recovered:?}");
    assert_eq!(t0_files, t0_files_recovered);

    // cleanup

    let paths = &[path1, path2, path3];
    retry(|| ctx.client.delete_objects(paths, &cancel)).await?;

    Ok(())
}

struct EnabledS3 {
    client: Arc<GenericRemoteStorage>,
    base_prefix: &'static str,
}

impl EnabledS3 {
    async fn setup(max_keys_in_list_response: Option<i32>) -> Self {
        let client = create_s3_client(max_keys_in_list_response)
            .await
            .context("S3 client creation")
            .expect("S3 client creation failed");

        EnabledS3 {
            client,
            base_prefix: BASE_PREFIX,
        }
    }

    fn configure_request_timeout(&mut self, timeout: Duration) {
        match Arc::get_mut(&mut self.client).expect("outer Arc::get_mut") {
            GenericRemoteStorage::AwsS3(s3) => {
                let s3 = Arc::get_mut(s3).expect("inner Arc::get_mut");
                s3.timeout = timeout;
            }
            _ => unreachable!(),
        }
    }
}

enum MaybeEnabledStorage {
    Enabled(EnabledS3),
    Disabled,
}

impl AsyncTestContext for MaybeEnabledStorage {
    async fn setup() -> Self {
        ensure_logging_ready();

        if env::var(ENABLE_REAL_S3_REMOTE_STORAGE_ENV_VAR_NAME).is_err() {
            info!(
                "`{}` env variable is not set, skipping the test",
                ENABLE_REAL_S3_REMOTE_STORAGE_ENV_VAR_NAME
            );
            return Self::Disabled;
        }

        Self::Enabled(EnabledS3::setup(None).await)
    }
}

enum MaybeEnabledStorageWithTestBlobs {
    Enabled(S3WithTestBlobs),
    Disabled,
    UploadsFailed(anyhow::Error, S3WithTestBlobs),
}

struct S3WithTestBlobs {
    enabled: EnabledS3,
    remote_prefixes: HashSet<RemotePath>,
    remote_blobs: HashSet<RemotePath>,
}

impl AsyncTestContext for MaybeEnabledStorageWithTestBlobs {
    async fn setup() -> Self {
        ensure_logging_ready();
        if env::var(ENABLE_REAL_S3_REMOTE_STORAGE_ENV_VAR_NAME).is_err() {
            info!(
                "`{}` env variable is not set, skipping the test",
                ENABLE_REAL_S3_REMOTE_STORAGE_ENV_VAR_NAME
            );
            return Self::Disabled;
        }

        let max_keys_in_list_response = 10;
        let upload_tasks_count = 1 + (2 * usize::try_from(max_keys_in_list_response).unwrap());

        let enabled = EnabledS3::setup(Some(max_keys_in_list_response)).await;

        match upload_remote_data(&enabled.client, enabled.base_prefix, upload_tasks_count).await {
            ControlFlow::Continue(uploads) => {
                info!("Remote objects created successfully");

                Self::Enabled(S3WithTestBlobs {
                    enabled,
                    remote_prefixes: uploads.prefixes,
                    remote_blobs: uploads.blobs,
                })
            }
            ControlFlow::Break(uploads) => Self::UploadsFailed(
                anyhow::anyhow!("One or multiple blobs failed to upload to S3"),
                S3WithTestBlobs {
                    enabled,
                    remote_prefixes: uploads.prefixes,
                    remote_blobs: uploads.blobs,
                },
            ),
        }
    }

    async fn teardown(self) {
        match self {
            Self::Disabled => {}
            Self::Enabled(ctx) | Self::UploadsFailed(_, ctx) => {
                cleanup(&ctx.enabled.client, ctx.remote_blobs).await;
            }
        }
    }
}

enum MaybeEnabledStorageWithSimpleTestBlobs {
    Enabled(S3WithSimpleTestBlobs),
    Disabled,
    UploadsFailed(anyhow::Error, S3WithSimpleTestBlobs),
}
struct S3WithSimpleTestBlobs {
    enabled: EnabledS3,
    remote_blobs: HashSet<RemotePath>,
}

impl AsyncTestContext for MaybeEnabledStorageWithSimpleTestBlobs {
    async fn setup() -> Self {
        ensure_logging_ready();
        if env::var(ENABLE_REAL_S3_REMOTE_STORAGE_ENV_VAR_NAME).is_err() {
            info!(
                "`{}` env variable is not set, skipping the test",
                ENABLE_REAL_S3_REMOTE_STORAGE_ENV_VAR_NAME
            );
            return Self::Disabled;
        }

        let max_keys_in_list_response = 10;
        let upload_tasks_count = 1 + (2 * usize::try_from(max_keys_in_list_response).unwrap());

        let enabled = EnabledS3::setup(Some(max_keys_in_list_response)).await;

        match upload_simple_remote_data(&enabled.client, upload_tasks_count).await {
            ControlFlow::Continue(uploads) => {
                info!("Remote objects created successfully");

                Self::Enabled(S3WithSimpleTestBlobs {
                    enabled,
                    remote_blobs: uploads,
                })
            }
            ControlFlow::Break(uploads) => Self::UploadsFailed(
                anyhow::anyhow!("One or multiple blobs failed to upload to S3"),
                S3WithSimpleTestBlobs {
                    enabled,
                    remote_blobs: uploads,
                },
            ),
        }
    }

    async fn teardown(self) {
        match self {
            Self::Disabled => {}
            Self::Enabled(ctx) | Self::UploadsFailed(_, ctx) => {
                cleanup(&ctx.enabled.client, ctx.remote_blobs).await;
            }
        }
    }
}

async fn create_s3_client(
    max_keys_per_list_response: Option<i32>,
) -> anyhow::Result<Arc<GenericRemoteStorage>> {
    use rand::Rng;

    let remote_storage_s3_bucket = env::var("REMOTE_STORAGE_S3_BUCKET")
        .context("`REMOTE_STORAGE_S3_BUCKET` env var is not set, but real S3 tests are enabled")?;
    let remote_storage_s3_region = env::var("REMOTE_STORAGE_S3_REGION")
        .context("`REMOTE_STORAGE_S3_REGION` env var is not set, but real S3 tests are enabled")?;

    // due to how time works, we've had test runners use the same nanos as bucket prefixes.
    // millis is just a debugging aid for easier finding the prefix later.
    let millis = std::time::SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .context("random s3 test prefix part calculation")?
        .as_millis();

    // because nanos can be the same for two threads so can millis, add randomness
    let random = rand::rng().random::<u32>();

    let remote_storage_config = RemoteStorageConfig {
        storage: RemoteStorageKind::AwsS3(S3Config {
            bucket_name: remote_storage_s3_bucket,
            bucket_region: remote_storage_s3_region,
            prefix_in_bucket: Some(format!("test_{millis}_{random:08x}/")),
            endpoint: None,
            concurrency_limit: NonZeroUsize::new(100).unwrap(),
            max_keys_per_list_response,
            upload_storage_class: None,
        }),
        timeout: RemoteStorageConfig::DEFAULT_TIMEOUT,
        small_timeout: RemoteStorageConfig::DEFAULT_SMALL_TIMEOUT,
    };
    Ok(Arc::new(
        GenericRemoteStorage::from_config(&remote_storage_config)
            .await
            .context("remote storage init")?,
    ))
}

#[test_context(MaybeEnabledStorage)]
#[tokio::test]
async fn download_is_timeouted(ctx: &mut MaybeEnabledStorage) {
    let MaybeEnabledStorage::Enabled(ctx) = ctx else {
        return;
    };

    let cancel = CancellationToken::new();

    let path = RemotePath::new(Utf8Path::new(
        format!("{}/file_to_copy", ctx.base_prefix).as_str(),
    ))
    .unwrap();

    let len = upload_large_enough_file(&ctx.client, &path, &cancel).await;

    let timeout = std::time::Duration::from_secs(5);

    ctx.configure_request_timeout(timeout);

    let started_at = std::time::Instant::now();
    let mut stream = ctx
        .client
        .download(&path, &DownloadOpts::default(), &cancel)
        .await
        .expect("download succeeds")
        .download_stream;

    if started_at.elapsed().mul_f32(0.9) >= timeout {
        tracing::warn!(
            elapsed_ms = started_at.elapsed().as_millis(),
            "timeout might be too low, consumed most of it during headers"
        );
    }

    let first = stream
        .next()
        .await
        .expect("should have the first blob")
        .expect("should have succeeded");

    tracing::info!(len = first.len(), "downloaded first chunk");

    assert!(
        first.len() < len,
        "uploaded file is too small, we downloaded all on first chunk"
    );

    tokio::time::sleep(timeout).await;

    {
        let started_at = std::time::Instant::now();
        let next = stream
            .next()
            .await
            .expect("stream should not have ended yet");

        tracing::info!(
            next.is_err = next.is_err(),
            elapsed_ms = started_at.elapsed().as_millis(),
            "received item after timeout"
        );

        let e = next.expect_err("expected an error, but got a chunk?");

        let inner = e.get_ref().expect("std::io::Error::inner should be set");
        assert!(
            inner
                .downcast_ref::<DownloadError>()
                .is_some_and(|e| matches!(e, DownloadError::Timeout)),
            "{inner:?}"
        );
    }

    ctx.configure_request_timeout(RemoteStorageConfig::DEFAULT_TIMEOUT);

    ctx.client.delete_objects(&[path], &cancel).await.unwrap()
}

#[test_context(MaybeEnabledStorage)]
#[tokio::test]
async fn download_is_cancelled(ctx: &mut MaybeEnabledStorage) {
    let MaybeEnabledStorage::Enabled(ctx) = ctx else {
        return;
    };

    let cancel = CancellationToken::new();

    let path = RemotePath::new(Utf8Path::new(
        format!("{}/file_to_copy", ctx.base_prefix).as_str(),
    ))
    .unwrap();

    let file_len = upload_large_enough_file(&ctx.client, &path, &cancel).await;

    {
        let stream = ctx
            .client
            .download(&path, &DownloadOpts::default(), &cancel)
            .await
            .expect("download succeeds")
            .download_stream;

        let mut reader = std::pin::pin!(tokio_util::io::StreamReader::new(stream));

        let first = reader.fill_buf().await.expect("should have the first blob");

        let len = first.len();
        tracing::info!(len, "downloaded first chunk");

        assert!(
            first.len() < file_len,
            "uploaded file is too small, we downloaded all on first chunk"
        );

        reader.consume(len);

        cancel.cancel();

        let next = reader.fill_buf().await;

        let e = next.expect_err("expected an error, but got a chunk?");

        let inner = e.get_ref().expect("std::io::Error::inner should be set");
        assert!(
            inner
                .downcast_ref::<DownloadError>()
                .is_some_and(|e| matches!(e, DownloadError::Cancelled)),
            "{inner:?}"
        );

        let e = DownloadError::from(e);

        assert!(matches!(e, DownloadError::Cancelled), "{e:?}");
    }

    let cancel = CancellationToken::new();

    ctx.client.delete_objects(&[path], &cancel).await.unwrap();
}

/// Upload a long enough file so that we cannot download it in single chunk
///
/// For s3 the first chunk seems to be less than 10kB, so this has a bit of a safety margin
async fn upload_large_enough_file(
    client: &GenericRemoteStorage,
    path: &RemotePath,
    cancel: &CancellationToken,
) -> usize {
    let header = bytes::Bytes::from_static("remote blob data content".as_bytes());
    let body = bytes::Bytes::from(vec![0u8; 1024]);
    let contents = std::iter::once(header).chain(std::iter::repeat_n(body, 128));

    let len = contents.clone().fold(0, |acc, next| acc + next.len());

    let contents = futures::stream::iter(contents.map(std::io::Result::Ok));

    client
        .upload(contents, len, path, None, cancel)
        .await
        .expect("upload succeeds");

    len
}