use crate::proto::Directory;
use crate::{proto, B3Digest, Error};
use futures::stream::BoxStream;
use prost::Message;
use std::ops::Deref;
use std::path::Path;
use tonic::async_trait;
use tracing::{instrument, warn};

use super::utils::traverse_directory;
use super::{ClosureValidator, DirectoryPutter, DirectoryService};

#[derive(Clone)]
pub struct SledDirectoryService {
    db: sled::Db,
}

impl SledDirectoryService {
    pub fn new<P: AsRef<Path>>(p: P) -> Result<Self, sled::Error> {
        let config = sled::Config::default()
            .use_compression(false) // is a required parameter
            .path(p);
        let db = config.open()?;

        Ok(Self { db })
    }

    pub fn new_temporary() -> Result<Self, sled::Error> {
        let config = sled::Config::default().temporary(true);
        let db = config.open()?;

        Ok(Self { db })
    }
}

#[async_trait]
impl DirectoryService for SledDirectoryService {
    #[instrument(skip(self, digest), fields(directory.digest = %digest))]
    async fn get(&self, digest: &B3Digest) -> Result<Option<proto::Directory>, Error> {
        match self.db.get(digest.as_slice()) {
            // The directory was not found, return
            Ok(None) => Ok(None),

            // The directory was found, try to parse the data as Directory message
            Ok(Some(data)) => match Directory::decode(&*data) {
                Ok(directory) => {
                    // Validate the retrieved Directory indeed has the
                    // digest we expect it to have, to detect corruptions.
                    let actual_digest = directory.digest();
                    if actual_digest != *digest {
                        return Err(Error::StorageError(format!(
                            "requested directory with digest {}, but got {}",
                            digest, actual_digest
                        )));
                    }

                    // Validate the Directory itself is valid.
                    if let Err(e) = directory.validate() {
                        warn!("directory failed validation: {}", e.to_string());
                        return Err(Error::StorageError(format!(
                            "directory {} failed validation: {}",
                            actual_digest, e,
                        )));
                    }

                    Ok(Some(directory))
                }
                Err(e) => {
                    warn!("unable to parse directory {}: {}", digest, e);
                    Err(Error::StorageError(e.to_string()))
                }
            },
            // some storage error?
            Err(e) => Err(Error::StorageError(e.to_string())),
        }
    }

    #[instrument(skip(self, directory), fields(directory.digest = %directory.digest()))]
    async fn put(&self, directory: proto::Directory) -> Result<B3Digest, Error> {
        let digest = directory.digest();

        // validate the directory itself.
        if let Err(e) = directory.validate() {
            return Err(Error::InvalidRequest(format!(
                "directory {} failed validation: {}",
                digest, e,
            )));
        }
        // store it
        let result = self.db.insert(digest.as_slice(), directory.encode_to_vec());
        if let Err(e) = result {
            return Err(Error::StorageError(e.to_string()));
        }
        Ok(digest)
    }

    #[instrument(skip_all, fields(directory.digest = %root_directory_digest))]
    fn get_recursive(
        &self,
        root_directory_digest: &B3Digest,
    ) -> BoxStream<Result<proto::Directory, Error>> {
        traverse_directory(self.clone(), root_directory_digest)
    }

    #[instrument(skip_all)]
    fn put_multiple_start(&self) -> Box<(dyn DirectoryPutter + 'static)>
    where
        Self: Clone,
    {
        Box::new(SledDirectoryPutter {
            tree: self.db.deref().clone(),
            directory_validator: Some(Default::default()),
        })
    }
}

/// Buffers Directory messages to be uploaded and inserts them in a batch
/// transaction on close.
pub struct SledDirectoryPutter {
    tree: sled::Tree,

    /// The directories (inside the directory validator) that we insert later,
    /// or None, if they were already inserted.
    directory_validator: Option<ClosureValidator>,
}

#[async_trait]
impl DirectoryPutter for SledDirectoryPutter {
    #[instrument(level = "trace", skip_all, fields(directory.digest=%directory.digest()), err)]
    async fn put(&mut self, directory: proto::Directory) -> Result<(), Error> {
        match self.directory_validator {
            None => return Err(Error::StorageError("already closed".to_string())),
            Some(ref mut validator) => {
                validator.add(directory)?;
            }
        }

        Ok(())
    }

    #[instrument(level = "trace", skip_all, ret, err)]
    async fn close(&mut self) -> Result<B3Digest, Error> {
        match self.directory_validator.take() {
            None => Err(Error::InvalidRequest("already closed".to_string())),
            Some(validator) => {
                // retrieve the validated directories.
                let directories = validator.finalize()?;

                // Get the root digest, which is at the end (cf. insertion order)
                let root_digest = directories
                    .last()
                    .ok_or_else(|| Error::InvalidRequest("got no directories".to_string()))?
                    .digest();

                let mut batch = sled::Batch::default();
                for directory in directories {
                    batch.insert(directory.digest().as_slice(), directory.encode_to_vec());
                }

                self.tree
                    .apply_batch(batch)
                    .map_err(|e| Error::StorageError(format!("unable to apply batch: {}", e)))?;

                Ok(root_digest)
            }
        }
    }
}