use core::str;
use std::collections::HashMap;
use std::sync::Arc;
use tokio::io::AsyncReadExt;
use tokio::io::AsyncWriteExt;
use tokio::sync::{Mutex, oneshot};

use std::sync::atomic::{AtomicU64, Ordering};

use crate::cmd::Cmd;
use crate::error::DBError;
use crate::options;
use crate::protocol::Protocol;
use crate::storage_trait::StorageBackend;
use crate::admin_meta;

// Embeddings: config and cache
use crate::embedding::{EmbeddingConfig, create_embedder, Embedder, create_image_embedder, ImageEmbedder};
use serde_json;
use ureq::{Agent, AgentBuilder};
use std::time::Duration;
use std::io::Read;

const NO_DB_SELECTED: u64 = u64::MAX;

#[derive(Clone)]
pub struct Server {
    pub db_cache: std::sync::Arc<std::sync::RwLock<HashMap<u64, Arc<dyn StorageBackend>>>>,
    pub option: options::DBOption,
    pub client_name: Option<String>,
    pub selected_db: u64, // Changed from usize to u64
    pub queued_cmd: Option<Vec<(Cmd, Protocol)>>,
    pub current_permissions: Option<crate::rpc::Permissions>,

    // In-memory registry of Tantivy search indexes for this server
    pub search_indexes: Arc<std::sync::RwLock<HashMap<String, Arc<crate::tantivy_search::TantivySearch>>>>,

    // Per-DB Lance stores (vector DB), keyed by db_id
    pub lance_stores: Arc<std::sync::RwLock<HashMap<u64, Arc<crate::lance_store::LanceStore>>>>,

    // Per-(db_id, dataset) embedder cache (text)
    pub embedders: Arc<std::sync::RwLock<HashMap<(u64, String), Arc<dyn Embedder>>>>,

    // Per-(db_id, dataset) image embedder cache (image)
    pub image_embedders: Arc<std::sync::RwLock<HashMap<(u64, String), Arc<dyn ImageEmbedder>>>>,
    
    // BLPOP waiter registry: per (db_index, key) FIFO of waiters
    pub list_waiters: Arc<Mutex<HashMap<u64, HashMap<String, Vec<Waiter>>>>>,
    pub waiter_seq: Arc<AtomicU64>,
}

pub struct Waiter {
    pub id: u64,
    pub side: PopSide,
    pub tx: oneshot::Sender<(String, String)>, // (key, element)
}

#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub enum PopSide {
    Left,
    Right,
}

impl Server {
    pub async fn new(option: options::DBOption) -> Self {
        Server {
            db_cache: Arc::new(std::sync::RwLock::new(HashMap::new())),
            option,
            client_name: None,
            selected_db: NO_DB_SELECTED,
            queued_cmd: None,
            current_permissions: None,
    
            search_indexes: Arc::new(std::sync::RwLock::new(HashMap::new())),
            lance_stores: Arc::new(std::sync::RwLock::new(HashMap::new())),
            embedders: Arc::new(std::sync::RwLock::new(HashMap::new())),
            image_embedders: Arc::new(std::sync::RwLock::new(HashMap::new())),
            list_waiters: Arc::new(Mutex::new(HashMap::new())),
            waiter_seq: Arc::new(AtomicU64::new(1)),
        }
    }

    // Path where search indexes are stored, namespaced per selected DB:
    // <base_dir>/search_indexes/<db_id>
    pub fn search_index_path(&self) -> std::path::PathBuf {
        let base = std::path::PathBuf::from(&self.option.dir)
            .join("search_indexes")
            .join(self.selected_db.to_string());
        if !base.exists() {
            let _ = std::fs::create_dir_all(&base);
        }
        base
    }

    // Path where Lance datasets are stored, namespaced per selected DB:
    // <base_dir>/lance/<db_id>
    pub fn lance_data_path(&self) -> std::path::PathBuf {
        let base = std::path::PathBuf::from(&self.option.dir)
            .join("lance")
            .join(self.selected_db.to_string());
        if !base.exists() {
            let _ = std::fs::create_dir_all(&base);
        }
        base
    }

    pub fn current_storage(&self) -> Result<Arc<dyn StorageBackend>, DBError> {
        // Require explicit SELECT before any storage access
        if self.selected_db == NO_DB_SELECTED {
            return Err(DBError("No database selected. Use SELECT <id> [KEY <key>] first".to_string()));
        }
        // Admin DB 0 access must be authenticated with SELECT 0 KEY <admin_secret>
        if self.selected_db == 0 {
            if !matches!(self.current_permissions, Some(crate::rpc::Permissions::ReadWrite)) {
                return Err(DBError("Admin DB 0 requires SELECT 0 KEY <admin_secret>".to_string()));
            }
        }

        let mut cache = self.db_cache.write().unwrap();

        if let Some(storage) = cache.get(&self.selected_db) {
            return Ok(storage.clone());
        }

        // Use process-wide shared handles to avoid sled/reDB double-open lock contention.
        let storage = if self.selected_db == 0 {
            // Admin DB 0: always via singleton
            admin_meta::open_admin_storage(
                &self.option.dir,
                self.option.backend.clone(),
                &self.option.admin_secret,
            )?
        } else {
            // Data DBs: via global registry keyed by id
            admin_meta::open_data_storage(
                &self.option.dir,
                self.option.backend.clone(),
                &self.option.admin_secret,
                self.selected_db,
            )?
        };

        cache.insert(self.selected_db, storage.clone());
        Ok(storage)
    }

    /// Get or create the LanceStore for the currently selected DB.
    /// Only valid for non-zero DBs and when the backend is Lance.
    pub fn lance_store(&self) -> Result<Arc<crate::lance_store::LanceStore>, DBError> {
        if self.selected_db == 0 {
            return Err(DBError("Lance not available on admin DB 0".to_string()));
        }
        // Resolve backend for selected_db
        let backend_opt = crate::admin_meta::get_database_backend(
            &self.option.dir,
            self.option.backend.clone(),
            &self.option.admin_secret,
            self.selected_db,
        )
        .ok()
        .flatten();

        if !matches!(backend_opt, Some(crate::options::BackendType::Lance)) {
            return Err(DBError("ERR DB backend is not Lance; LANCE.* commands are not allowed".to_string()));
        }

        // Fast path: read lock
        {
            let map = self.lance_stores.read().unwrap();
            if let Some(store) = map.get(&self.selected_db) {
                return Ok(store.clone());
            }
        }

        // Slow path: create and insert
        let store = Arc::new(crate::lance_store::LanceStore::new(&self.option.dir, self.selected_db)?);
        {
            let mut map = self.lance_stores.write().unwrap();
            map.insert(self.selected_db, store.clone());
        }
        Ok(store)
    }

    // ----- Embedding configuration and resolution -----

    // Sidecar embedding config path: <base_dir>/lance/<db_id>/<dataset>.lance.embedding.json
    fn dataset_embedding_config_path(&self, dataset: &str) -> std::path::PathBuf {
        let mut base = self.lance_data_path();
        // Ensure parent dir exists
        if !base.exists() {
            let _ = std::fs::create_dir_all(&base);
        }
        base.push(format!("{}.lance.embedding.json", dataset));
        base
    }

    /// Persist per-dataset embedding config as JSON sidecar.
    pub fn set_dataset_embedding_config(&self, dataset: &str, cfg: &EmbeddingConfig) -> Result<(), DBError> {
        if self.selected_db == 0 {
            return Err(DBError("Lance not available on admin DB 0".to_string()));
        }
        let p = self.dataset_embedding_config_path(dataset);
        let data = serde_json::to_vec_pretty(cfg)
            .map_err(|e| DBError(format!("Failed to serialize embedding config: {}", e)))?;
        std::fs::write(&p, data)
            .map_err(|e| DBError(format!("Failed to write embedding config {}: {}", p.display(), e)))?;
        // Invalidate embedder cache entry for this dataset
        {
            let mut map = self.embedders.write().unwrap();
            map.remove(&(self.selected_db, dataset.to_string()));
        }
        {
            let mut map_img = self.image_embedders.write().unwrap();
            map_img.remove(&(self.selected_db, dataset.to_string()));
        }
        Ok(())
    }

    /// Load per-dataset embedding config.
    pub fn get_dataset_embedding_config(&self, dataset: &str) -> Result<EmbeddingConfig, DBError> {
        if self.selected_db == 0 {
            return Err(DBError("Lance not available on admin DB 0".to_string()));
        }
        let p = self.dataset_embedding_config_path(dataset);
        if !p.exists() {
            return Err(DBError(format!(
                "Embedding config not set for dataset '{}'. Use LANCE.EMBEDDING CONFIG SET ... or RPC to configure.",
                dataset
            )));
        }
        let data = std::fs::read(&p)
            .map_err(|e| DBError(format!("Failed to read embedding config {}: {}", p.display(), e)))?;
        let cfg: EmbeddingConfig = serde_json::from_slice(&data)
            .map_err(|e| DBError(format!("Failed to parse embedding config {}: {}", p.display(), e)))?;
        Ok(cfg)
    }

    /// Resolve or build an embedder for (db_id, dataset). Caches instance.
    pub fn get_embedder_for(&self, dataset: &str) -> Result<Arc<dyn Embedder>, DBError> {
        if self.selected_db == 0 {
            return Err(DBError("Lance not available on admin DB 0".to_string()));
        }
        // Fast path
        {
            let map = self.embedders.read().unwrap();
            if let Some(e) = map.get(&(self.selected_db, dataset.to_string())) {
                return Ok(e.clone());
            }
        }
        // Load config and instantiate
        let cfg = self.get_dataset_embedding_config(dataset)?;
        let emb = create_embedder(&cfg)?;
        {
            let mut map = self.embedders.write().unwrap();
            map.insert((self.selected_db, dataset.to_string()), emb.clone());
        }
        Ok(emb)
    }

    /// Resolve or build an IMAGE embedder for (db_id, dataset). Caches instance.
    pub fn get_image_embedder_for(&self, dataset: &str) -> Result<Arc<dyn ImageEmbedder>, DBError> {
        if self.selected_db == 0 {
            return Err(DBError("Lance not available on admin DB 0".to_string()));
        }
        // Fast path
        {
            let map = self.image_embedders.read().unwrap();
            if let Some(e) = map.get(&(self.selected_db, dataset.to_string())) {
                return Ok(e.clone());
            }
        }
        // Load config and instantiate
        let cfg = self.get_dataset_embedding_config(dataset)?;
        let emb = create_image_embedder(&cfg)?;
        {
            let mut map = self.image_embedders.write().unwrap();
            map.insert((self.selected_db, dataset.to_string()), emb.clone());
        }
        Ok(emb)
    }

    /// Download image bytes from a URI with safety checks (size, timeout, content-type, optional host allowlist).
    /// Env overrides:
    /// - HERODB_IMAGE_MAX_BYTES (u64, default 10485760)
    /// - HERODB_IMAGE_FETCH_TIMEOUT_SECS (u64, default 30)
    /// - HERODB_IMAGE_ALLOWED_HOSTS (comma-separated, optional)
    pub fn fetch_image_bytes_from_uri(&self, uri: &str) -> Result<Vec<u8>, DBError> {
        // Basic scheme validation
        if !(uri.starts_with("http://") || uri.starts_with("https://")) {
            return Err(DBError("Only http(s) URIs are supported for image fetch".into()));
        }
        // Parse host (naive) for allowlist check
        let host = {
            let after_scheme = match uri.find("://") {
                Some(i) => &uri[i + 3..],
                None => uri,
            };
            let end = after_scheme.find('/').unwrap_or(after_scheme.len());
            let host_port = &after_scheme[..end];
            host_port.split('@').last().unwrap_or(host_port).split(':').next().unwrap_or(host_port).to_string()
        };

        let max_bytes: u64 = std::env::var("HERODB_IMAGE_MAX_BYTES").ok().and_then(|s| s.parse::<u64>().ok()).unwrap_or(10 * 1024 * 1024);
        let timeout_secs: u64 = std::env::var("HERODB_IMAGE_FETCH_TIMEOUT_SECS").ok().and_then(|s| s.parse::<u64>().ok()).unwrap_or(30);
        let allowed_hosts_env = std::env::var("HERODB_IMAGE_ALLOWED_HOSTS").ok();
        if let Some(allow) = allowed_hosts_env {
            if !allow.split(',').map(|s| s.trim()).filter(|s| !s.is_empty()).any(|h| h.eq_ignore_ascii_case(&host)) {
                return Err(DBError(format!("Host '{}' not allowed for image fetch (HERODB_IMAGE_ALLOWED_HOSTS)", host)));
            }
        }

        let agent: Agent = AgentBuilder::new()
            .timeout_read(Duration::from_secs(timeout_secs))
            .timeout_write(Duration::from_secs(timeout_secs))
            .build();

        let resp = agent.get(uri).call().map_err(|e| DBError(format!("HTTP GET failed: {}", e)))?;
        // Validate content-type
        let ctype = resp.header("Content-Type").unwrap_or("");
        let ctype_main = ctype.split(';').next().unwrap_or("").trim().to_ascii_lowercase();
        if !ctype_main.starts_with("image/") {
            return Err(DBError(format!("Remote content-type '{}' is not image/*", ctype)));
        }

        // Read with cap
        let mut reader = resp.into_reader();
        let mut buf: Vec<u8> = Vec::with_capacity(8192);
        let mut tmp = [0u8; 8192];
        let mut total: u64 = 0;
        loop {
            let n = reader.read(&mut tmp).map_err(|e| DBError(format!("Read error: {}", e)))?;
            if n == 0 { break; }
            total += n as u64;
            if total > max_bytes {
                return Err(DBError(format!("Image exceeds max allowed bytes {}", max_bytes)));
            }
            buf.extend_from_slice(&tmp[..n]);
        }
        Ok(buf)
    }

    /// Check if current permissions allow read operations
    pub fn has_read_permission(&self) -> bool {
        // No DB selected -> no permissions
        if self.selected_db == NO_DB_SELECTED {
            return false;
        }
        // If an explicit permission is set for this connection, honor it.
        if let Some(perms) = self.current_permissions.as_ref() {
            return matches!(*perms, crate::rpc::Permissions::Read | crate::rpc::Permissions::ReadWrite);
        }
        // Fallback ONLY when no explicit permission context (e.g., JSON-RPC flows without SELECT).
        match crate::admin_meta::verify_access(
            &self.option.dir,
            self.option.backend.clone(),
            &self.option.admin_secret,
            self.selected_db,
            None,
        ) {
            Ok(Some(crate::rpc::Permissions::Read)) | Ok(Some(crate::rpc::Permissions::ReadWrite)) => true,
            _ => false,
        }
    }

    /// Check if current permissions allow write operations
    pub fn has_write_permission(&self) -> bool {
        // No DB selected -> no permissions
        if self.selected_db == NO_DB_SELECTED {
            return false;
        }
        // If an explicit permission is set for this connection, honor it.
        if let Some(perms) = self.current_permissions.as_ref() {
            return matches!(*perms, crate::rpc::Permissions::ReadWrite);
        }
        // Fallback ONLY when no explicit permission context (e.g., JSON-RPC flows without SELECT).
        match crate::admin_meta::verify_access(
            &self.option.dir,
            self.option.backend.clone(),
            &self.option.admin_secret,
            self.selected_db,
            None,
        ) {
            Ok(Some(crate::rpc::Permissions::ReadWrite)) => true,
            _ => false,
        }
    }

    // ----- BLPOP waiter helpers -----

    pub async fn register_waiter(&self, db_index: u64, key: &str, side: PopSide) -> (u64, oneshot::Receiver<(String, String)>) {
        let id = self.waiter_seq.fetch_add(1, Ordering::Relaxed);
        let (tx, rx) = oneshot::channel::<(String, String)>();

        let mut guard = self.list_waiters.lock().await;
        let per_db = guard.entry(db_index).or_insert_with(HashMap::new);
        let q = per_db.entry(key.to_string()).or_insert_with(Vec::new);
        q.push(Waiter { id, side, tx });
        (id, rx)
    }

    pub async fn unregister_waiter(&self, db_index: u64, key: &str, id: u64) {
        let mut guard = self.list_waiters.lock().await;
        if let Some(per_db) = guard.get_mut(&db_index) {
            if let Some(q) = per_db.get_mut(key) {
                q.retain(|w| w.id != id);
                if q.is_empty() {
                    per_db.remove(key);
                }
            }
            if per_db.is_empty() {
                guard.remove(&db_index);
            }
        }
    }

    // Called after LPUSH/RPUSH to deliver to blocked BLPOP waiters.
    pub async fn drain_waiters_after_push(&self, key: &str) -> Result<(), DBError> {
        let db_index = self.selected_db;

        loop {
            // Check if any waiter exists
            let maybe_waiter = {
                let mut guard = self.list_waiters.lock().await;
                if let Some(per_db) = guard.get_mut(&db_index) {
                    if let Some(q) = per_db.get_mut(key) {
                        if !q.is_empty() {
                            // Pop FIFO
                            Some(q.remove(0))
                        } else {
                            None
                        }
                    } else {
                        None
                    }
                } else {
                    None
                }
            };

            let waiter = if let Some(w) = maybe_waiter { w } else { break };

            // Pop one element depending on waiter side
            let elems = match waiter.side {
                PopSide::Left => self.current_storage()?.lpop(key, 1)?,
                PopSide::Right => self.current_storage()?.rpop(key, 1)?,
            };
            if elems.is_empty() {
                // Nothing to deliver; re-register waiter at the front to preserve order
                let mut guard = self.list_waiters.lock().await;
                let per_db = guard.entry(db_index).or_insert_with(HashMap::new);
                let q = per_db.entry(key.to_string()).or_insert_with(Vec::new);
                q.insert(0, waiter);
                break;
            } else {
                let elem = elems[0].clone();
                // Send to waiter; if receiver dropped, just continue
                let _ = waiter.tx.send((key.to_string(), elem));
                // Loop to try to satisfy more waiters if more elements remain
                continue;
            }
        }

        Ok(())
    }

    pub async fn handle(
        &mut self,
        mut stream: tokio::net::TcpStream,
    ) -> Result<(), DBError> {
        // Accumulate incoming bytes to handle partial RESP frames
        let mut acc = String::new();
        let mut buf = vec![0u8; 8192];

        loop {
            let n = match stream.read(&mut buf).await {
                Ok(0) => {
                    println!("[handle] connection closed");
                    return Ok(());
                }
                Ok(n) => n,
                Err(e) => {
                    println!("[handle] read error: {:?}", e);
                    return Err(e.into());
                }
            };

            // Append to accumulator. RESP for our usage is ASCII-safe.
            acc.push_str(str::from_utf8(&buf[..n])?);

            // Try to parse as many complete commands as are available in 'acc'.
            loop {
                let parsed = Cmd::from(&acc);
                let (cmd, protocol, remaining) = match parsed {
                    Ok((cmd, protocol, remaining)) => (cmd, protocol, remaining),
                    Err(_e) => {
                        // Incomplete or invalid frame; assume incomplete and wait for more data.
                        // This avoids emitting spurious protocol_error for split frames.
                        break;
                    }
                };

                // Advance the accumulator to the unparsed remainder
                acc = remaining.to_string();

                if self.option.debug {
                    println!("\x1b[34;1mgot command: {:?}, protocol: {:?}\x1b[0m", cmd, protocol);
                } else {
                    println!("got command: {:?}, protocol: {:?}", cmd, protocol);
                }

                // Check if this is a QUIT command before processing
                let is_quit = matches!(cmd, Cmd::Quit);

                let res = match cmd.run(self).await {
                    Ok(p) => p,
                    Err(e) => {
                        if self.option.debug {
                            eprintln!("[run error] {:?}", e);
                        }
                        Protocol::err(&format!("ERR {}", e.0))
                    }
                };

                if self.option.debug {
                    println!("\x1b[34;1mqueued cmd {:?}\x1b[0m", self.queued_cmd);
                    println!("\x1b[32;1mgoing to send response {}\x1b[0m", res.encode());
                } else {
                    print!("queued cmd {:?}", self.queued_cmd);
                    println!("going to send response {}", res.encode());
                }

                _ = stream.write(res.encode().as_bytes()).await?;

                // If this was a QUIT command, close the connection
                if is_quit {
                    println!("[handle] QUIT command received, closing connection");
                    return Ok(());
                }

                // Continue parsing any further complete commands already in 'acc'
                if acc.is_empty() {
                    break;
                }
            }
        }
    }
}