use std::path::{Path, PathBuf};
use std::sync::Arc;
use std::time::Duration;

use anyhow::bail;
use log::{error, info, trace};
use tokio::fs;
use tokio::task::spawn_blocking;
use tokio::time::sleep;

use crate::compression::from_tar_gz;
use crate::index_controller::updates::UpdateMsg;

use super::index_resolver::index_store::IndexStore;
use super::index_resolver::uuid_store::UuidStore;
use super::index_resolver::IndexResolver;
use super::updates::UpdateSender;

pub struct SnapshotService<U, I> {
    index_resolver: Arc<IndexResolver<U, I>>,
    update_sender: UpdateSender,
    snapshot_period: Duration,
    snapshot_path: PathBuf,
    db_name: String,
}

impl<U, I> SnapshotService<U, I>
where
    U: UuidStore + Sync + Send + 'static,
    I: IndexStore + Sync + Send + 'static,
{
    pub fn new(
        index_resolver: Arc<IndexResolver<U, I>>,
        update_sender: UpdateSender,
        snapshot_period: Duration,
        snapshot_path: PathBuf,
        db_name: String,
    ) -> Self {
        Self {
            index_resolver,
            update_sender,
            snapshot_period,
            snapshot_path,
            db_name,
        }
    }

    pub async fn run(self) {
        info!(
            "Snapshot scheduled every {}s.",
            self.snapshot_period.as_secs()
        );
        loop {
            if let Err(e) = self.perform_snapshot().await {
                error!("Error while performing snapshot: {}", e);
            }
            sleep(self.snapshot_period).await;
        }
    }

    async fn perform_snapshot(&self) -> anyhow::Result<()> {
        trace!("Performing snapshot.");

        let snapshot_dir = self.snapshot_path.clone();
        fs::create_dir_all(&snapshot_dir).await?;
        let temp_snapshot_dir = spawn_blocking(tempfile::tempdir).await??;
        let temp_snapshot_path = temp_snapshot_dir.path().to_owned();

        let indexes = self
            .index_resolver
            .snapshot(temp_snapshot_path.clone())
            .await?;

        if indexes.is_empty() {
            return Ok(());
        }

        UpdateMsg::snapshot(&self.update_sender, temp_snapshot_path.clone(), indexes).await?;

        let snapshot_path = self
            .snapshot_path
            .join(format!("{}.snapshot", self.db_name));
        let snapshot_path = spawn_blocking(move || -> anyhow::Result<PathBuf> {
            let temp_snapshot_file = tempfile::NamedTempFile::new_in(&snapshot_dir)?;
            let temp_snapshot_file_path = temp_snapshot_file.path().to_owned();
            crate::compression::to_tar_gz(temp_snapshot_path, temp_snapshot_file_path)?;
            temp_snapshot_file.persist(&snapshot_path)?;
            Ok(snapshot_path)
        })
        .await??;

        trace!("Created snapshot in {:?}.", snapshot_path);

        Ok(())
    }
}

pub fn load_snapshot(
    db_path: impl AsRef<Path>,
    snapshot_path: impl AsRef<Path>,
    ignore_snapshot_if_db_exists: bool,
    ignore_missing_snapshot: bool,
) -> anyhow::Result<()> {
    if !db_path.as_ref().exists() && snapshot_path.as_ref().exists() {
        match from_tar_gz(snapshot_path, &db_path) {
            Ok(()) => Ok(()),
            Err(e) => {
                //clean created db folder
                std::fs::remove_dir_all(&db_path)?;
                Err(e)
            }
        }
    } else if db_path.as_ref().exists() && !ignore_snapshot_if_db_exists {
        bail!(
            "database already exists at {:?}, try to delete it or rename it",
            db_path
                .as_ref()
                .canonicalize()
                .unwrap_or_else(|_| db_path.as_ref().to_owned())
        )
    } else if !snapshot_path.as_ref().exists() && !ignore_missing_snapshot {
        bail!(
            "snapshot doesn't exist at {:?}",
            snapshot_path
                .as_ref()
                .canonicalize()
                .unwrap_or_else(|_| snapshot_path.as_ref().to_owned())
        )
    } else {
        Ok(())
    }
}

#[cfg(test)]
mod test {
    use std::{collections::HashSet, sync::Arc};

    use futures::future::{err, ok};
    use once_cell::sync::Lazy;
    use rand::Rng;
    use uuid::Uuid;

    use crate::index::error::IndexError;
    use crate::index::test::Mocker;
    use crate::index::{error::Result as IndexResult, Index};
    use crate::index_controller::index_resolver::error::IndexResolverError;
    use crate::index_controller::index_resolver::index_store::MockIndexStore;
    use crate::index_controller::index_resolver::uuid_store::MockUuidStore;
    use crate::index_controller::index_resolver::IndexResolver;
    use crate::index_controller::updates::create_update_handler;

    use super::*;

    fn setup() {
        static SETUP: Lazy<()> = Lazy::new(|| {
            if cfg!(windows) {
                std::env::set_var("TMP", ".");
            } else {
                std::env::set_var("TMPDIR", ".");
            }
        });

        // just deref to make sure the env is setup
        *SETUP
    }

    #[actix_rt::test]
    async fn test_normal() {
        setup();

        let mut rng = rand::thread_rng();
        let uuids_num: usize = rng.gen_range(5..10);
        let uuids = (0..uuids_num)
            .map(|_| Uuid::new_v4())
            .collect::<HashSet<_>>();

        let mut uuid_store = MockUuidStore::new();
        let uuids_clone = uuids.clone();
        uuid_store
            .expect_snapshot()
            .times(1)
            .returning(move |_| Box::pin(ok(uuids_clone.clone())));

        let mut indexes = uuids.clone().into_iter().map(|uuid| {
            let mocker = Mocker::default();
            mocker
                .when("snapshot")
                .times(1)
                .then(|_: &Path| -> IndexResult<()> { Ok(()) });
            mocker.when("uuid").then(move |_: ()| uuid);
            Index::faux(mocker)
        });

        let uuids_clone = uuids.clone();
        let mut index_store = MockIndexStore::new();
        index_store
            .expect_get()
            .withf(move |uuid| uuids_clone.contains(uuid))
            .times(uuids_num)
            .returning(move |_| Box::pin(ok(Some(indexes.next().unwrap()))));

        let index_resolver = Arc::new(IndexResolver::new(uuid_store, index_store));

        let dir = tempfile::tempdir().unwrap();
        let update_sender =
            create_update_handler(index_resolver.clone(), dir.path(), 4096 * 100).unwrap();

        let snapshot_path = tempfile::tempdir().unwrap();
        let snapshot_service = SnapshotService::new(
            index_resolver,
            update_sender,
            Duration::from_millis(100),
            snapshot_path.path().to_owned(),
            "data.ms".to_string(),
        );

        snapshot_service.perform_snapshot().await.unwrap();
    }

    #[actix_rt::test]
    async fn error_performing_uuid_snapshot() {
        setup();

        let mut uuid_store = MockUuidStore::new();
        uuid_store
            .expect_snapshot()
            .once()
            .returning(move |_| Box::pin(err(IndexResolverError::IndexAlreadyExists)));

        let mut index_store = MockIndexStore::new();
        index_store.expect_get().never();

        let index_resolver = Arc::new(IndexResolver::new(uuid_store, index_store));

        let dir = tempfile::tempdir().unwrap();
        let update_sender =
            create_update_handler(index_resolver.clone(), dir.path(), 4096 * 100).unwrap();

        let snapshot_path = tempfile::tempdir().unwrap();
        let snapshot_service = SnapshotService::new(
            index_resolver,
            update_sender,
            Duration::from_millis(100),
            snapshot_path.path().to_owned(),
            "data.ms".to_string(),
        );

        assert!(snapshot_service.perform_snapshot().await.is_err());
    }

    #[actix_rt::test]
    async fn error_performing_index_snapshot() {
        setup();

        let uuids: HashSet<Uuid> = vec![Uuid::new_v4()].into_iter().collect();

        let mut uuid_store = MockUuidStore::new();
        let uuids_clone = uuids.clone();
        uuid_store
            .expect_snapshot()
            .once()
            .returning(move |_| Box::pin(ok(uuids_clone.clone())));

        let mut indexes = uuids.clone().into_iter().map(|uuid| {
            let mocker = Mocker::default();
            // index returns random error
            mocker
                .when("snapshot")
                .then(|_: &Path| -> IndexResult<()> { Err(IndexError::ExistingPrimaryKey) });
            mocker.when("uuid").then(move |_: ()| uuid);
            Index::faux(mocker)
        });

        let uuids_clone = uuids.clone();
        let mut index_store = MockIndexStore::new();
        index_store
            .expect_get()
            .withf(move |uuid| uuids_clone.contains(uuid))
            .once()
            .returning(move |_| Box::pin(ok(Some(indexes.next().unwrap()))));

        let index_resolver = Arc::new(IndexResolver::new(uuid_store, index_store));

        let dir = tempfile::tempdir().unwrap();
        let update_sender =
            create_update_handler(index_resolver.clone(), dir.path(), 4096 * 100).unwrap();

        let snapshot_path = tempfile::tempdir().unwrap();
        let snapshot_service = SnapshotService::new(
            index_resolver,
            update_sender,
            Duration::from_millis(100),
            snapshot_path.path().to_owned(),
            "data.ms".to_string(),
        );

        assert!(snapshot_service.perform_snapshot().await.is_err());
    }
}