use std::{future::Future, pin::Pin, sync::Arc};

use crate::Result;

#[cfg(feature = "sqlite")]
pub(crate) mod sqlite;

#[cfg(feature = "rocksdb")]
pub(crate) mod rocksdb;

#[cfg(any(feature = "sqlite", feature = "rocksdb",))]
pub(crate) mod watchers;

pub(crate) trait KeyValueDatabaseEngine: Send + Sync {
    #[cfg(any(feature = "sqlite", feature = "rocksdb"))]
    fn open(config: &super::Config) -> Result<Self>
    where
        Self: Sized;
    fn open_tree(&self, name: &'static str) -> Result<Arc<dyn KvTree>>;
    fn cleanup(&self) -> Result<()> {
        Ok(())
    }
    fn memory_usage(&self) -> Result<String> {
        Ok("Current database engine does not support memory usage reporting."
            .to_owned())
    }
}

pub(crate) trait KvTree: Send + Sync {
    fn get(&self, key: &[u8]) -> Result<Option<Vec<u8>>>;

    fn insert(&self, key: &[u8], value: &[u8]) -> Result<()>;
    fn insert_batch(
        &self,
        iter: &mut dyn Iterator<Item = (Vec<u8>, Vec<u8>)>,
    ) -> Result<()>;

    fn remove(&self, key: &[u8]) -> Result<()>;

    fn iter<'a>(&'a self) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + 'a>;

    fn iter_from<'a>(
        &'a self,
        from: &[u8],
        backwards: bool,
    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + 'a>;

    fn increment(&self, key: &[u8]) -> Result<Vec<u8>>;
    fn increment_batch(
        &self,
        iter: &mut dyn Iterator<Item = Vec<u8>>,
    ) -> Result<()>;

    fn scan_prefix<'a>(
        &'a self,
        prefix: Vec<u8>,
    ) -> Box<dyn Iterator<Item = (Vec<u8>, Vec<u8>)> + 'a>;

    fn watch_prefix<'a>(
        &'a self,
        prefix: &[u8],
    ) -> Pin<Box<dyn Future<Output = ()> + Send + 'a>>;

    fn clear(&self) -> Result<()> {
        for (key, _) in self.iter() {
            self.remove(&key)?;
        }

        Ok(())
    }
}
