use std::{
    io::{Error, Result},
    sync::Arc,
};

use nix_compat::{
    nix_daemon::{
        types::{AddToStoreNarRequest, UnkeyedValidPathInfo},
        NixDaemonIO,
    },
    nixbase32,
    store_path::{build_ca_path, StorePath},
};
use tracing::warn;
use tvix_castore::{blobservice::BlobService, directoryservice::DirectoryService};
use tvix_store::{nar::ingest_nar_and_hash, path_info::PathInfo, pathinfoservice::PathInfoService};

#[allow(dead_code)]
pub struct TvixDaemon {
    blob_service: Arc<dyn BlobService>,
    directory_service: Arc<dyn DirectoryService>,
    path_info_service: Arc<dyn PathInfoService>,
}

impl TvixDaemon {
    pub fn new(
        blob_service: Arc<dyn BlobService>,
        directory_service: Arc<dyn DirectoryService>,
        path_info_service: Arc<dyn PathInfoService>,
    ) -> Self {
        Self {
            blob_service,
            directory_service,
            path_info_service,
        }
    }
}

/// Implements [NixDaemonIO] backed by tvix services.
impl NixDaemonIO for TvixDaemon {
    async fn query_path_info(
        &self,
        path: &StorePath<String>,
    ) -> Result<Option<UnkeyedValidPathInfo>> {
        match self.path_info_service.get(*path.digest()).await? {
            Some(path_info) => {
                if path_info.store_path.name() == path.name() {
                    Ok(Some(into_unkeyed_path_info(path_info)))
                } else {
                    Ok(None)
                }
            }
            None => Ok(None),
        }
    }

    async fn query_path_from_hash_part(&self, hash: &[u8]) -> Result<Option<UnkeyedValidPathInfo>> {
        let digest = hash
            .try_into()
            .map_err(|_| Error::other("invalid digest length"))?;
        match self.path_info_service.get(digest).await? {
            Some(path_info) => Ok(Some(into_unkeyed_path_info(path_info))),
            None => Ok(None),
        }
    }

    async fn add_to_store_nar<R>(&self, request: AddToStoreNarRequest, reader: &mut R) -> Result<()>
    where
        R: tokio::io::AsyncRead + Send + Unpin,
    {
        let (root_node, nar_sha256, nar_size) = ingest_nar_and_hash(
            self.blob_service.clone(),
            self.directory_service.clone(),
            reader,
            &request.ca,
        )
        .await
        .map_err(|e| Error::other(e.to_string()))?;

        if nar_size != request.nar_size || nar_sha256 != *request.nar_hash {
            warn!(
                nar_hash.expected = nixbase32::encode(&*request.nar_hash),
                nar_hash.actual = nixbase32::encode(&nar_sha256),
                "nar hash mismatch"
            );
            return Err(Error::other(
                "ingested nar ended up different from what was specified in the request",
            ));
        }

        if let Some(cahash) = &request.ca {
            let actual_path: StorePath<String> = build_ca_path(
                request.path.name(),
                cahash,
                request.references.iter().map(|p| p.to_absolute_path()),
                false,
            )
            .map_err(Error::other)?;
            if actual_path != request.path {
                return Err(Error::other("path mismatch"));
            }
        }

        let path_info = PathInfo {
            store_path: request.path,
            node: root_node,
            references: request.references,
            nar_size,
            nar_sha256,
            signatures: request.signatures,
            deriver: request.deriver,
            ca: request.ca,
        };
        self.path_info_service
            .put(path_info)
            .await
            .map_err(|e| Error::other(e.to_string()))?;
        Ok(())
    }
}

// PathInfo lives in the tvix-store crate, but does not depend on nix-compat's wire feature,
// while UnkeyedValidPathInfo is only available if that feature is enabled. To avoid complexity
// we manually convert as opposed to creating a From<PathInfo>.
fn into_unkeyed_path_info(info: PathInfo) -> UnkeyedValidPathInfo {
    UnkeyedValidPathInfo {
        deriver: info.deriver,
        nar_hash: nixbase32::encode(&info.nar_sha256),
        references: info.references,
        registration_time: 0,
        nar_size: info.nar_size,
        ultimate: false,
        signatures: info.signatures,
        ca: info.ca,
    }
}