use std::path::PathBuf;
use std::sync::Arc;

use rocksdb::{DB, Options, WriteBatch};

use crate::storage::{RawByHashEntry, RocksStore, StorageError, StorageResult};

const RAW_BY_HASH_KEY_PREFIX: &str = "rawbyhash:";

fn raw_by_hash_key(sha256_hex: &str) -> String {
    format!("{RAW_BY_HASH_KEY_PREFIX}{sha256_hex}")
}

pub trait RawObjectStore {
    fn get_raw_entry(&self, sha256_hex: &str) -> StorageResult<Option<RawByHashEntry>>;

    fn get_raw_entries_batch(
        &self,
        sha256_hexes: &[String],
    ) -> StorageResult<Vec<Option<RawByHashEntry>>>;

    fn get_blob_bytes(&self, sha256_hex: &str) -> StorageResult<Option<Vec<u8>>> {
        self.get_raw_entry(sha256_hex)
            .map(|entry| entry.map(|entry| entry.bytes))
    }

    fn get_blob_bytes_batch(
        &self,
        sha256_hexes: &[String],
    ) -> StorageResult<Vec<Option<Vec<u8>>>> {
        self.get_raw_entries_batch(sha256_hexes).map(|entries| {
            entries
                .into_iter()
                .map(|entry| entry.map(|entry| entry.bytes))
                .collect()
        })
    }
}

#[derive(Clone, Debug)]
pub struct ExternalRawStoreDb {
    path: PathBuf,
    db: Arc<DB>,
}

impl ExternalRawStoreDb {
    pub fn open(path: impl Into<PathBuf>) -> StorageResult<Self> {
        let path = path.into();
        if let Some(parent) = path.parent() {
            std::fs::create_dir_all(parent).map_err(|e| StorageError::RocksDb(e.to_string()))?;
        }
        let mut opts = Options::default();
        opts.create_if_missing(true);
        opts.set_compression_type(rocksdb::DBCompressionType::Lz4);
        let db = DB::open(&opts, &path).map_err(|e| StorageError::RocksDb(e.to_string()))?;
        Ok(Self {
            path,
            db: Arc::new(db),
        })
    }

    pub fn put_raw_entry(&self, entry: &RawByHashEntry) -> StorageResult<()> {
        entry.validate_internal()?;
        let key = raw_by_hash_key(&entry.sha256_hex);
        let value =
            serde_cbor::to_vec(entry).map_err(|e| StorageError::Codec { entity: "raw_by_hash", detail: e.to_string() })?;
        self.db
            .put(key.as_bytes(), value)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?;
        Ok(())
    }

    pub fn put_raw_entries_batch(&self, entries: &[RawByHashEntry]) -> StorageResult<()> {
        if entries.is_empty() {
            return Ok(());
        }
        let mut batch = WriteBatch::default();
        for entry in entries {
            entry.validate_internal()?;
            let key = raw_by_hash_key(&entry.sha256_hex);
            let value = serde_cbor::to_vec(entry).map_err(|e| StorageError::Codec {
                entity: "raw_by_hash",
                detail: e.to_string(),
            })?;
            batch.put(key.as_bytes(), value);
        }
        self.db
            .write(batch)
            .map_err(|e| StorageError::RocksDb(e.to_string()))?;
        Ok(())
    }

    pub fn delete_raw_entry(&self, sha256_hex: &str) -> StorageResult<()> {
        let key = raw_by_hash_key(sha256_hex);
        self.db
            .delete(key.as_bytes())
            .map_err(|e| StorageError::RocksDb(e.to_string()))
    }

    pub fn path(&self) -> &PathBuf {
        &self.path
    }
}

impl RawObjectStore for RocksStore {
    fn get_raw_entry(&self, sha256_hex: &str) -> StorageResult<Option<RawByHashEntry>> {
        self.get_raw_by_hash_entry(sha256_hex)
    }

    fn get_raw_entries_batch(
        &self,
        sha256_hexes: &[String],
    ) -> StorageResult<Vec<Option<RawByHashEntry>>> {
        self.get_raw_by_hash_entries_batch(sha256_hexes)
    }
}

impl RawObjectStore for ExternalRawStoreDb {
    fn get_raw_entry(&self, sha256_hex: &str) -> StorageResult<Option<RawByHashEntry>> {
        let key = raw_by_hash_key(sha256_hex);
        let Some(bytes) = self
            .db
            .get(key.as_bytes())
            .map_err(|e| StorageError::RocksDb(e.to_string()))?
        else {
            return Ok(None);
        };
        let entry = serde_cbor::from_slice::<RawByHashEntry>(&bytes).map_err(|e| StorageError::Codec {
            entity: "raw_by_hash",
            detail: e.to_string(),
        })?;
        entry.validate_internal()?;
        Ok(Some(entry))
    }

    fn get_raw_entries_batch(
        &self,
        sha256_hexes: &[String],
    ) -> StorageResult<Vec<Option<RawByHashEntry>>> {
        if sha256_hexes.is_empty() {
            return Ok(Vec::new());
        }
        let keys: Vec<String> = sha256_hexes.iter().map(|hash| raw_by_hash_key(hash)).collect();
        self.db
            .multi_get(keys.iter().map(|key| key.as_bytes()))
            .into_iter()
            .map(|res| {
                let maybe = res.map_err(|e| StorageError::RocksDb(e.to_string()))?;
                match maybe {
                    Some(bytes) => {
                        let entry = serde_cbor::from_slice::<RawByHashEntry>(&bytes).map_err(|e| {
                            StorageError::Codec {
                                entity: "raw_by_hash",
                                detail: e.to_string(),
                            }
                        })?;
                        entry.validate_internal()?;
                        Ok(Some(entry))
                    }
                    None => Ok(None),
                }
            })
            .collect()
    }
}

#[cfg(test)]
mod tests {
    use super::{ExternalRawStoreDb, RawObjectStore};
    use crate::storage::{RawByHashEntry, RocksStore, StorageError};

    fn sha256_hex(bytes: &[u8]) -> String {
        use sha2::{Digest, Sha256};
        hex::encode(Sha256::digest(bytes))
    }

    #[test]
    fn rocks_store_raw_object_store_reads_single_and_batch_entries() {
        let td = tempfile::tempdir().expect("tempdir");
        let store = RocksStore::open(td.path()).expect("open rocksdb");

        let a = b"object-a".to_vec();
        let b = b"object-b".to_vec();
        let a_hash = sha256_hex(&a);
        let b_hash = sha256_hex(&b);

        store
            .put_raw_by_hash_entry(&RawByHashEntry::from_bytes(a_hash.clone(), a.clone()))
            .expect("put a");
        store
            .put_raw_by_hash_entry(&RawByHashEntry::from_bytes(b_hash.clone(), b.clone()))
            .expect("put b");

        let single = store
            .get_raw_entry(&a_hash)
            .expect("get single")
            .expect("present");
        assert_eq!(single.bytes, a);

        let batch = store
            .get_raw_entries_batch(&[a_hash.clone(), "00".repeat(32), b_hash.clone()])
            .expect("get batch");
        assert_eq!(batch.len(), 3);
        assert_eq!(batch[0].as_ref().map(|entry| entry.bytes.as_slice()), Some(a.as_slice()));
        assert!(batch[1].is_none());
        assert_eq!(batch[2].as_ref().map(|entry| entry.bytes.as_slice()), Some(b.as_slice()));
    }

    #[test]
    fn external_raw_store_db_roundtrips_entries() {
        let td = tempfile::tempdir().expect("tempdir");
        let raw_store = ExternalRawStoreDb::open(td.path().join("raw-store.db")).expect("open raw store");

        let mut entry = RawByHashEntry::from_bytes(sha256_hex(b"blob"), b"blob".to_vec());
        entry.origin_uris.push("rsync://example.test/repo/a.cer".to_string());
        entry.object_type = Some("cer".to_string());
        raw_store.put_raw_entry(&entry).expect("put raw entry");

        let got = raw_store
            .get_raw_entry(&entry.sha256_hex)
            .expect("read raw entry")
            .expect("entry exists");
        assert_eq!(got, entry);
    }

    #[test]
    fn external_raw_store_db_batch_writes_and_reads() {
        let td = tempfile::tempdir().expect("tempdir");
        let raw_store = ExternalRawStoreDb::open(td.path().join("raw-store.db")).expect("open raw store");

        let a = RawByHashEntry::from_bytes(sha256_hex(b"a"), b"a".to_vec());
        let b = RawByHashEntry::from_bytes(sha256_hex(b"b"), b"b".to_vec());
        raw_store
            .put_raw_entries_batch(&[a.clone(), b.clone()])
            .expect("batch put");

        let batch = raw_store
            .get_raw_entries_batch(&[a.sha256_hex.clone(), b.sha256_hex.clone()])
            .expect("batch get");
        assert_eq!(batch.len(), 2);
        assert_eq!(batch[0], Some(a));
        assert_eq!(batch[1], Some(b));
    }

    #[test]
    fn raw_object_store_default_blob_helpers_return_bytes_only() {
        let td = tempfile::tempdir().expect("tempdir");
        let raw_store = ExternalRawStoreDb::open(td.path().join("nested/raw-store.db"))
            .expect("open raw store");

        let mut entry = RawByHashEntry::from_bytes(sha256_hex(b"blob"), b"blob".to_vec());
        entry.origin_uris.push("rsync://example.test/repo/blob.roa".to_string());
        raw_store.put_raw_entry(&entry).expect("put raw entry");

        let single = raw_store
            .get_blob_bytes(&entry.sha256_hex)
            .expect("get blob bytes")
            .expect("entry exists");
        assert_eq!(single, b"blob".to_vec());

        let batch = raw_store
            .get_blob_bytes_batch(&[entry.sha256_hex.clone(), "00".repeat(32)])
            .expect("get blob bytes batch");
        assert_eq!(batch, vec![Some(b"blob".to_vec()), None]);
    }

    #[test]
    fn external_raw_store_db_delete_removes_entry() {
        let td = tempfile::tempdir().expect("tempdir");
        let raw_store = ExternalRawStoreDb::open(td.path().join("raw-store.db")).expect("open raw store");

        let entry = RawByHashEntry::from_bytes(sha256_hex(b"gone"), b"gone".to_vec());
        raw_store.put_raw_entry(&entry).expect("put");
        assert!(raw_store.get_raw_entry(&entry.sha256_hex).unwrap().is_some());

        raw_store
            .delete_raw_entry(&entry.sha256_hex)
            .expect("delete entry");
        assert!(raw_store.get_raw_entry(&entry.sha256_hex).unwrap().is_none());
    }

    #[test]
    fn external_raw_store_db_rejects_invalid_entry_on_put() {
        let td = tempfile::tempdir().expect("tempdir");
        let raw_store = ExternalRawStoreDb::open(td.path().join("raw-store.db")).expect("open raw store");

        let bad = RawByHashEntry {
            sha256_hex: "11".repeat(32),
            bytes: b"blob".to_vec(),
            origin_uris: Vec::new(),
            object_type: None,
            encoding: None,
        };
        let err = raw_store.put_raw_entry(&bad).expect_err("invalid hash should fail");
        assert!(matches!(err, StorageError::InvalidData { .. }));
    }

    #[test]
    fn external_raw_store_db_reports_codec_error_for_corrupt_value() {
        let td = tempfile::tempdir().expect("tempdir");
        let raw_store = ExternalRawStoreDb::open(td.path().join("raw-store.db")).expect("open raw store");
        raw_store
            .db
            .put(b"rawbyhash:deadbeef", b"not-cbor")
            .expect("inject corrupt bytes");

        let err = raw_store
            .get_raw_entry("deadbeef")
            .expect_err("corrupt value should fail");
        assert!(matches!(err, StorageError::Codec { entity: "raw_by_hash", .. }));
    }

    #[test]
    fn external_raw_store_db_batch_returns_empty_for_empty_request() {
        let td = tempfile::tempdir().expect("tempdir");
        let raw_store = ExternalRawStoreDb::open(td.path().join("raw-store.db")).expect("open raw store");
        let entries = raw_store
            .get_raw_entries_batch(&[])
            .expect("empty batch succeeds");
        assert!(entries.is_empty());
        raw_store.put_raw_entries_batch(&[]).expect("empty put succeeds");
    }
}