use std::path::PathBuf;
use std::sync::{Arc, OnceLock, Mutex, RwLock};
use std::collections::HashMap;

use crate::error::DBError;
use crate::options;
use crate::rpc::Permissions;
use crate::storage::Storage;
use crate::storage_sled::SledStorage;
use crate::storage_trait::StorageBackend;

// Key builders
fn k_admin_next_id() -> &'static str {
    "admin:next_id"
}
fn k_admin_dbs() -> &'static str {
    "admin:dbs"
}
fn k_meta_db(id: u64) -> String {
    format!("meta:db:{}", id)
}
fn k_meta_db_keys(id: u64) -> String {
    format!("meta:db:{}:keys", id)
}
fn k_meta_db_enc(id: u64) -> String {
    format!("meta:db:{}:enc", id)
}

// Global cache of admin DB 0 handles per base_dir to avoid sled/reDB file-lock contention
// and to correctly isolate different test instances with distinct directories.
static ADMIN_STORAGES: OnceLock<RwLock<HashMap<String, Arc<dyn StorageBackend>>>> = OnceLock::new();

// Global registry for data DB storages to avoid double-open across process.
static DATA_STORAGES: OnceLock<RwLock<HashMap<u64, Arc<dyn StorageBackend>>>> = OnceLock::new();
static DATA_INIT_LOCK: Mutex<()> = Mutex::new(());

fn init_admin_storage(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
) -> Result<Arc<dyn StorageBackend>, DBError> {
    let db_file = PathBuf::from(base_dir).join("0.db");
    if let Some(parent_dir) = db_file.parent() {
        std::fs::create_dir_all(parent_dir).map_err(|e| {
            DBError(format!("Failed to create directory {}: {}", parent_dir.display(), e))
        })?;
    }
    let storage: Arc<dyn StorageBackend> = match backend {
        options::BackendType::Redb => Arc::new(Storage::new(&db_file, true, Some(admin_secret))?),
        options::BackendType::Sled => Arc::new(SledStorage::new(&db_file, true, Some(admin_secret))?),
        options::BackendType::Tantivy => {
            return Err(DBError("Admin DB 0 cannot use Tantivy backend".to_string()))
        }
    };
    Ok(storage)
}

// Get or initialize a cached handle to admin DB 0 per base_dir (thread-safe, no double-open race)
pub fn open_admin_storage(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
) -> Result<Arc<dyn StorageBackend>, DBError> {
    let map = ADMIN_STORAGES.get_or_init(|| RwLock::new(HashMap::new()));
    // Fast path
    if let Some(st) = map.read().unwrap().get(base_dir) {
        return Ok(st.clone());
    }
    // Slow path with write lock
    {
        let mut w = map.write().unwrap();
        if let Some(st) = w.get(base_dir) {
            return Ok(st.clone());
        }

        // Detect existing 0.db backend by filesystem, if present.
        let admin_path = PathBuf::from(base_dir).join("0.db");
        let detected = if admin_path.exists() {
            if admin_path.is_file() {
                Some(options::BackendType::Redb)
            } else if admin_path.is_dir() {
                Some(options::BackendType::Sled)
            } else {
                None
            }
        } else {
            None
        };

        let effective_backend = match detected {
            Some(d) if d != backend => {
                eprintln!(
                    "warning: Admin DB 0 at {} appears to be {:?}, but process default is {:?}. Using detected backend.",
                    admin_path.display(),
                    d,
                    backend
                );
                d
            }
            Some(d) => d,
            None => backend, // First boot: use requested backend to initialize 0.db
        };

        let st = init_admin_storage(base_dir, effective_backend, admin_secret)?;
        w.insert(base_dir.to_string(), st.clone());
        Ok(st)
    }
}

// Ensure admin structures exist in encrypted DB 0
pub fn ensure_bootstrap(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
) -> Result<(), DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;

    // Initialize next id if missing
    if !admin.exists(k_admin_next_id())? {
        admin.set(k_admin_next_id().to_string(), "1".to_string())?;
    }
    // admin:dbs is a hash; it's fine if it doesn't exist (hlen -> 0)
    Ok(())
}

// Get or initialize a shared handle to a data DB (> 0), avoiding double-open across subsystems
pub fn open_data_storage(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
) -> Result<Arc<dyn StorageBackend>, DBError> {
    if id == 0 {
        return open_admin_storage(base_dir, backend, admin_secret);
    }

    // Validate existence in admin metadata
    if !db_exists(base_dir, backend.clone(), admin_secret, id)? {
        return Err(DBError(format!(
            "Cannot open database instance {}, as that database instance does not exist.",
            id
        )));
    }

    let map = DATA_STORAGES.get_or_init(|| RwLock::new(HashMap::new()));
    // Fast path
    if let Some(st) = map.read().unwrap().get(&id) {
        return Ok(st.clone());
    }

    // Slow path with init lock
    let _guard = DATA_INIT_LOCK.lock().unwrap();
    if let Some(st) = map.read().unwrap().get(&id) {
        return Ok(st.clone());
    }

    // Resolve effective backend for this db id:
    // 1) Try admin meta "backend" field
    // 2) If missing, sniff filesystem (file => Redb, dir => Sled), then persist into admin meta
    // 3) Fallback to requested 'backend' (startup default) if nothing else is known
    let meta_backend = get_database_backend(base_dir, backend.clone(), admin_secret, id).ok().flatten();
    let db_path = PathBuf::from(base_dir).join(format!("{}.db", id));
    let sniffed_backend = if db_path.exists() {
        if db_path.is_file() {
            Some(options::BackendType::Redb)
        } else if db_path.is_dir() {
            Some(options::BackendType::Sled)
        } else {
            None
        }
    } else {
        None
    };
    let effective_backend = meta_backend.clone().or(sniffed_backend).unwrap_or(backend.clone());

    // If we had to sniff (i.e., meta missing), persist it for future robustness
    if meta_backend.is_none() {
        let _ = set_database_backend(base_dir, backend.clone(), admin_secret, id, effective_backend.clone());
    }

    // Warn if caller-provided backend differs from effective
    if effective_backend != backend {
        eprintln!(
            "notice: Database {} backend resolved to {:?} (caller requested {:?}). Using resolved backend.",
            id, effective_backend, backend
        );
    }

    // Determine per-db encryption (from admin meta)
    let enc = get_enc_key(base_dir, backend.clone(), admin_secret, id)?;
    let should_encrypt = enc.is_some();

    // Build database file path and ensure parent dir exists
    let db_file = PathBuf::from(base_dir).join(format!("{}.db", id));
    if let Some(parent_dir) = db_file.parent() {
        std::fs::create_dir_all(parent_dir).map_err(|e| {
            DBError(format!("Failed to create directory {}: {}", parent_dir.display(), e))
        })?;
    }

    // Open storage using the effective backend
    let storage: Arc<dyn StorageBackend> = match effective_backend {
        options::BackendType::Redb => Arc::new(Storage::new(&db_file, should_encrypt, enc.as_deref())?),
        options::BackendType::Sled => Arc::new(SledStorage::new(&db_file, should_encrypt, enc.as_deref())?),
        options::BackendType::Tantivy => {
            return Err(DBError("Tantivy backend has no KV storage; use FT.* commands only".to_string()))
        }
    };

    // Publish to registry
    map.write().unwrap().insert(id, storage.clone());
    Ok(storage)
}

// Allocate the next DB id and persist new pointer
pub fn allocate_next_id(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
) -> Result<u64, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let cur = admin
        .get(k_admin_next_id())?
        .unwrap_or_else(|| "1".to_string());
    let id: u64 = cur.parse().unwrap_or(1);
    let next = id.checked_add(1).ok_or_else(|| DBError("next_id overflow".into()))?;
    admin.set(k_admin_next_id().to_string(), next.to_string())?;

    // Register into admin:dbs set/hash
    let _ = admin.hset(k_admin_dbs(), vec![(id.to_string(), "1".to_string())])?;

    // Default meta for the new db: public true
    let meta_key = k_meta_db(id);
    let _ = admin.hset(&meta_key, vec![("public".to_string(), "true".to_string())])?;

    Ok(id)
}

// Check existence of a db id in admin:dbs
pub fn db_exists(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
) -> Result<bool, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    Ok(admin.hexists(k_admin_dbs(), &id.to_string())?)
}

// Get per-db encryption key, if any
pub fn get_enc_key(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
) -> Result<Option<String>, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    admin.get(&k_meta_db_enc(id))
}

// Set per-db encryption key (called during create)
pub fn set_enc_key(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
    key: &str,
) -> Result<(), DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    admin.set(k_meta_db_enc(id), key.to_string())
}

// Set database public flag
pub fn set_database_public(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
    public: bool,
) -> Result<(), DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let mk = k_meta_db(id);
    let _ = admin.hset(&mk, vec![("public".to_string(), public.to_string())])?;
    Ok(())
}

// Persist per-db backend type in admin metadata (module-scope)
pub fn set_database_backend(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
    db_backend: options::BackendType,
) -> Result<(), DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let mk = k_meta_db(id);
    let val = match db_backend {
        options::BackendType::Redb => "Redb",
        options::BackendType::Sled => "Sled",
        options::BackendType::Tantivy => "Tantivy",
    };
    let _ = admin.hset(&mk, vec![("backend".to_string(), val.to_string())])?;
    Ok(())
}

pub fn get_database_backend(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
) -> Result<Option<options::BackendType>, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let mk = k_meta_db(id);
    match admin.hget(&mk, "backend")? {
        Some(s) if s == "Redb" => Ok(Some(options::BackendType::Redb)),
        Some(s) if s == "Sled" => Ok(Some(options::BackendType::Sled)),
        Some(s) if s == "Tantivy" => Ok(Some(options::BackendType::Tantivy)),
        _ => Ok(None),
    }
}

// Set database name
pub fn set_database_name(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
    name: &str,
) -> Result<(), DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let mk = k_meta_db(id);
    let _ = admin.hset(&mk, vec![("name".to_string(), name.to_string())])?;
    Ok(())
}

// Get database name
pub fn get_database_name(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
) -> Result<Option<String>, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let mk = k_meta_db(id);
    admin.hget(&mk, "name")
}

// Internal: load public flag; default to true when meta missing
fn load_public(
    admin: &Arc<dyn StorageBackend>,
    id: u64,
) -> Result<bool, DBError> {
    let mk = k_meta_db(id);
    match admin.hget(&mk, "public")? {
        Some(v) => Ok(v == "true"),
        None => Ok(true),
    }
}

// Add access key for db (value format: "Read:ts" or "ReadWrite:ts")
pub fn add_access_key(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
    key_plain: &str,
    perms: Permissions,
) -> Result<(), DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let hash = crate::rpc::hash_key(key_plain);
    let v = match perms {
        Permissions::Read => format!("Read:{}", now_secs()),
        Permissions::ReadWrite => format!("ReadWrite:{}", now_secs()),
    };
    let _ = admin.hset(&k_meta_db_keys(id), vec![(hash, v)])?;
    Ok(())
}

// Delete access key by hash
pub fn delete_access_key(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
    key_hash: &str,
) -> Result<bool, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let n = admin.hdel(&k_meta_db_keys(id), vec![key_hash.to_string()])?;
    Ok(n > 0)
}

// List access keys, returning (hash, perms, created_at_secs)
pub fn list_access_keys(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
) -> Result<Vec<(String, Permissions, u64)>, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let pairs = admin.hgetall(&k_meta_db_keys(id))?;
    let mut out = Vec::new();
    for (hash, val) in pairs {
        let (perm, ts) = parse_perm_value(&val);
        out.push((hash, perm, ts));
    }
    Ok(out)
}

// Verify access permission for db id with optional key
// Returns:
// - Ok(Some(Permissions)) when access is allowed
// - Ok(None) when not allowed or db missing (caller can distinguish by calling db_exists)
pub fn verify_access(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
    id: u64,
    key_opt: Option<&str>,
) -> Result<Option<Permissions>, DBError> {
    // Admin DB 0: require exact admin_secret
    if id == 0 {
        if let Some(k) = key_opt {
            if k == admin_secret {
                return Ok(Some(Permissions::ReadWrite));
            }
        }
        return Ok(None);
    }

    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    if !admin.hexists(k_admin_dbs(), &id.to_string())? {
        return Ok(None);
    }

    // Public?
    if load_public(&admin, id)? {
        return Ok(Some(Permissions::ReadWrite));
    }

    // Private: require key and verify
    if let Some(k) = key_opt {
        let hash = crate::rpc::hash_key(k);
        if let Some(v) = admin.hget(&k_meta_db_keys(id), &hash)? {
            let (perm, _ts) = parse_perm_value(&v);
            return Ok(Some(perm));
        }
    }
    Ok(None)
}

// Enumerate all db ids
pub fn list_dbs(
    base_dir: &str,
    backend: options::BackendType,
    admin_secret: &str,
) -> Result<Vec<u64>, DBError> {
    let admin = open_admin_storage(base_dir, backend, admin_secret)?;
    let ids = admin.hkeys(k_admin_dbs())?;
    let mut out = Vec::new();
    for s in ids {
        if let Ok(v) = s.parse() {
            out.push(v);
        }
    }
    Ok(out)
}

// Helper: parse permission value "Read:ts" or "ReadWrite:ts"
fn parse_perm_value(v: &str) -> (Permissions, u64) {
    let mut parts = v.split(':');
    let p = parts.next().unwrap_or("Read");
    let ts = parts
        .next()
        .and_then(|s| s.parse().ok())
        .unwrap_or(0u64);
    let perm = match p {
        "ReadWrite" => Permissions::ReadWrite,
        _ => Permissions::Read,
    };
    (perm, ts)
}

fn now_secs() -> u64 {
    use std::time::{SystemTime, UNIX_EPOCH};
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .unwrap_or_default()
        .as_secs()
}