kreuzberg 4.8.2

//! Embedding generation support for RAG (Retrieval-Augmented Generation) systems.
//!
//! This module provides text embedding generation using ONNX models via a vendored
//! text embedding inference engine. Embeddings can be generated for text chunks to
//! enable semantic search and RAG pipelines.
//!
//! # Features
//!
//! - Multiple pre-configured models optimized for different use cases
//! - Preset configurations for common RAG scenarios
//! - Full customization of model location and parameters
//! - Batch processing for efficient embedding generation
//! - Thread-safe inference without mutex contention
//! - Optional GPU acceleration via ONNX Runtime execution providers
//!
//! # ONNX Runtime Requirement
//!
//! **CRITICAL**: This module requires ONNX Runtime to be installed on the system.
//! The `embeddings` feature uses dynamic loading (`ort-load-dynamic`), which detects
//! the ONNX Runtime library at runtime.
//!
//! ## Installation Instructions
//!
//! - **macOS**: `brew install onnxruntime`
//! - **Linux (Ubuntu/Debian)**: `apt install libonnxruntime libonnxruntime-dev`
//! - **Linux (Fedora)**: `dnf install onnxruntime onnxruntime-devel`
//! - **Linux (Arch)**: `pacman -S onnxruntime`
//! - **Windows (MSVC)**: Download from https://github.com/microsoft/onnxruntime/releases and add to PATH
//!
//! Alternatively, set the `ORT_DYLIB_PATH` environment variable to the ONNX Runtime library path.
//!
//! For Docker/containers, install via package manager in your base image.
//! Verified packages: Ubuntu 22.04+, Fedora 38+, Arch Linux.
//!
//! ## Platform Limitations
//!
//! **Windows MinGW builds are not supported**. ONNX Runtime requires the MSVC toolchain on Windows.
//! Please use Windows MSVC builds or disable the embeddings feature.
//!
//! # Example
//!
//! ```rust,ignore
//! use kreuzberg::{extract_file, ExtractionConfig, ChunkingConfig, EmbeddingConfig};
//!
//! let config = ExtractionConfig {
//!     chunking: Some(ChunkingConfig {
//!         preset: Some("balanced".to_string()),
//!         embedding: Some(EmbeddingConfig::default()),
//!         ..Default::default()
//!     }),
//!     ..Default::default()
//! };
//!
//! let result = extract_file("document.pdf", None, &config).await?;
//! for chunk in result.chunks.unwrap() {
//!     if let Some(embedding) = chunk.embedding {
//!         println!("Chunk has {} dimension embedding", embedding.len());
//!     }
//! }
//! ```

pub mod engine;

use ahash::AHashMap;
use std::sync::{Arc, RwLock};

use once_cell::sync::Lazy;

use engine::EmbeddingEngine;

type CachedEngine = Arc<EmbeddingEngine>;

static ENGINE_CACHE: Lazy<RwLock<AHashMap<String, CachedEngine>>> = Lazy::new(|| RwLock::new(AHashMap::new()));

/// Global semaphore that limits concurrent ONNX embedding inference calls.
///
/// Prevents resource exhaustion when many async callers invoke `embed_texts_async`
/// simultaneously. The permit count is set once on first access using the thread
/// budget, matching the pattern used elsewhere (e.g., image OCR, batch extraction).
#[cfg(feature = "tokio-runtime")]
static EMBED_SEMAPHORE: Lazy<Arc<tokio::sync::Semaphore>> = Lazy::new(|| {
    let budget = crate::core::config::concurrency::resolve_thread_budget(None);
    Arc::new(tokio::sync::Semaphore::new(budget))
});

/// Preset configurations for common RAG use cases.
///
/// Each preset combines chunk size, overlap, and embedding model
/// to provide an optimized configuration for specific scenarios.
#[derive(Debug, Clone)]
pub struct EmbeddingPreset {
    pub name: &'static str,
    pub chunk_size: usize,
    pub overlap: usize,
    /// HuggingFace repository name for the model.
    pub model_repo: &'static str,
    /// Pooling strategy: "cls" or "mean".
    pub pooling: &'static str,
    /// Path to the ONNX model file within the repo.
    pub model_file: &'static str,
    pub dimensions: usize,
    pub description: &'static str,
}

/// All available embedding presets.
pub const EMBEDDING_PRESETS: &[EmbeddingPreset] = &[
    EmbeddingPreset {
        name: "fast",
        chunk_size: 512,
        overlap: 50,
        model_repo: "Xenova/all-MiniLM-L6-v2",
        pooling: "mean",
        model_file: "onnx/model_quantized.onnx",
        dimensions: 384,
        description: "Fast embedding with quantized model (384 dims, ~22M params). Best for: Quick prototyping, development, resource-constrained environments.",
    },
    EmbeddingPreset {
        name: "balanced",
        chunk_size: 1024,
        overlap: 100,
        model_repo: "Xenova/bge-base-en-v1.5",
        pooling: "cls",
        model_file: "onnx/model.onnx",
        dimensions: 768,
        description: "Balanced quality and speed (768 dims, ~109M params). Best for: General-purpose RAG, production deployments, English documents.",
    },
    EmbeddingPreset {
        name: "quality",
        chunk_size: 2000,
        overlap: 200,
        model_repo: "Xenova/bge-large-en-v1.5",
        pooling: "cls",
        model_file: "onnx/model.onnx",
        dimensions: 1024,
        description: "High quality with larger context (1024 dims, ~335M params). Best for: Complex documents, maximum accuracy, sufficient compute resources.",
    },
    EmbeddingPreset {
        name: "multilingual",
        chunk_size: 1024,
        overlap: 100,
        model_repo: "intfloat/multilingual-e5-base",
        pooling: "mean",
        model_file: "onnx/model.onnx",
        dimensions: 768,
        description: "Multilingual support (768 dims, 100+ languages). Best for: International documents, mixed-language content, global applications.",
    },
];

/// Get a preset by name.
pub fn get_preset(name: &str) -> Option<&'static EmbeddingPreset> {
    EMBEDDING_PRESETS.iter().find(|p| p.name == name)
}

/// List all available preset names.
pub fn list_presets() -> Vec<&'static str> {
    EMBEDDING_PRESETS.iter().map(|p| p.name).collect()
}

/// Returns installation instructions for ONNX Runtime.
fn onnx_runtime_install_message() -> String {
    #[cfg(all(windows, target_env = "gnu"))]
    {
        return "ONNX Runtime embeddings are not supported on Windows MinGW builds. \
        ONNX Runtime requires MSVC toolchain. \
        Please use Windows MSVC builds or disable embeddings feature."
            .to_string();
    }

    #[cfg(not(all(windows, target_env = "gnu")))]
    {
        "ONNX Runtime is required for embeddings functionality. \
        Install: \
        macOS: 'brew install onnxruntime', \
        Linux (Ubuntu/Debian): 'apt install libonnxruntime libonnxruntime-dev', \
        Linux (Fedora): 'dnf install onnxruntime onnxruntime-devel', \
        Linux (Arch): 'pacman -S onnxruntime', \
        Windows (MSVC): Download from https://github.com/microsoft/onnxruntime/releases and add to PATH. \
        \
        Alternatively, set ORT_DYLIB_PATH environment variable to the ONNX Runtime library path. \
        \
        For Docker/containers: Install via package manager in your base image. \
        Verified packages: Ubuntu 22.04+, Fedora 38+, Arch Linux."
            .to_string()
    }
}

/// Resolve the cache directory for embedding models.
fn resolve_cache_dir(cache_dir: Option<std::path::PathBuf>) -> std::path::PathBuf {
    cache_dir.unwrap_or_else(|| crate::cache_dir::resolve_cache_dir("embeddings"))
}

/// Resolve model info (repo, model file, pooling) from an EmbeddingModelType config.
fn resolve_model_info(
    model_type: &crate::core::config::EmbeddingModelType,
) -> crate::Result<(&str, &str, engine::Pooling)> {
    match model_type {
        crate::core::config::EmbeddingModelType::Preset { name } => {
            let preset = get_preset(name)
                .ok_or_else(|| crate::KreuzbergError::embedding(format!("Unknown embedding preset: {name}")))?;
            let pooling = match preset.pooling {
                "cls" => engine::Pooling::Cls,
                _ => engine::Pooling::Mean,
            };
            Ok((preset.model_repo, preset.model_file, pooling))
        }
        crate::core::config::EmbeddingModelType::Custom { model_id, .. } => {
            // For custom models, default to mean pooling and standard model path.
            // Users providing custom HF models should ensure the repo has the expected layout.
            Ok((model_id.as_str(), "onnx/model.onnx", engine::Pooling::Mean))
        }
        crate::core::config::EmbeddingModelType::Llm { .. } => Err(crate::KreuzbergError::embedding(
            "LLM-based embeddings require the 'liter-llm' feature and are handled by a separate code path",
        )),
    }
}

/// Load a tokenizer from HuggingFace model files.
///
/// Adapted from the vendored embedding engine's tokenizer initialization.
fn load_tokenizer(
    tokenizer_path: &std::path::Path,
    config_path: &std::path::Path,
    special_tokens_path: &std::path::Path,
    tokenizer_config_path: &std::path::Path,
    max_length: usize,
) -> crate::Result<tokenizers::Tokenizer> {
    use tokenizers::{AddedToken, PaddingParams, PaddingStrategy, TruncationParams};

    let config: serde_json::Value = serde_json::from_slice(
        &std::fs::read(config_path)
            .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to read config.json: {e}")))?,
    )
    .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to parse config.json: {e}")))?;

    let tokenizer_config: serde_json::Value = serde_json::from_slice(
        &std::fs::read(tokenizer_config_path)
            .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to read tokenizer_config.json: {e}")))?,
    )
    .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to parse tokenizer_config.json: {e}")))?;

    let mut tokenizer = tokenizers::Tokenizer::from_file(tokenizer_path)
        .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to load tokenizer: {e}")))?;

    let model_max_length = tokenizer_config["model_max_length"].as_f64().unwrap_or(512.0) as usize;
    let max_length = max_length.min(model_max_length);
    let pad_id = config["pad_token_id"].as_u64().unwrap_or(0) as u32;
    let pad_token = tokenizer_config["pad_token"].as_str().unwrap_or("[PAD]").to_string();

    tokenizer
        .with_padding(Some(PaddingParams {
            strategy: PaddingStrategy::BatchLongest,
            pad_token,
            pad_id,
            ..Default::default()
        }))
        .with_truncation(Some(TruncationParams {
            max_length,
            ..Default::default()
        }))
        .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to configure tokenizer: {e}")))?;

    // Add special tokens from special_tokens_map.json
    if let Ok(special_tokens_data) = std::fs::read(special_tokens_path)
        && let Ok(serde_json::Value::Object(map)) = serde_json::from_slice(&special_tokens_data)
    {
        for (_, value) in &map {
            if let Some(content) = value.as_str() {
                tokenizer.add_special_tokens(&[AddedToken {
                    content: content.to_string(),
                    special: true,
                    ..Default::default()
                }]);
            } else if value.is_object()
                && let (Some(content), Some(single_word), Some(lstrip), Some(rstrip), Some(normalized)) = (
                    value["content"].as_str(),
                    value["single_word"].as_bool(),
                    value["lstrip"].as_bool(),
                    value["rstrip"].as_bool(),
                    value["normalized"].as_bool(),
                )
            {
                tokenizer.add_special_tokens(&[AddedToken {
                    content: content.to_string(),
                    special: true,
                    single_word,
                    lstrip,
                    rstrip,
                    normalized,
                }]);
            }
        }
    }

    Ok(tokenizer)
}

/// Download model files from HuggingFace and return their local paths.
///
/// Returns `(model_path, tokenizer_path, config_path, special_tokens_path, tokenizer_config_path)`.
fn download_model_files(
    repo_name: &str,
    model_file: &str,
    cache_directory: &std::path::Path,
) -> crate::Result<(
    std::path::PathBuf,
    std::path::PathBuf,
    std::path::PathBuf,
    std::path::PathBuf,
    std::path::PathBuf,
)> {
    let api = hf_hub::api::sync::ApiBuilder::from_env()
        .with_cache_dir(cache_directory.to_path_buf())
        .with_progress(true)
        .build()
        .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to create HF API client: {e}")))?;

    let repo = api.model(repo_name.to_string());

    let model_path = repo
        .get(model_file)
        .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to download {model_file}: {e}")))?;

    let tokenizer_path = repo
        .get("tokenizer.json")
        .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to download tokenizer.json: {e}")))?;

    let config_path = repo
        .get("config.json")
        .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to download config.json: {e}")))?;

    // These are optional — fall back to empty paths that load_tokenizer handles gracefully
    let special_tokens_path = repo
        .get("special_tokens_map.json")
        .unwrap_or_else(|_| std::path::PathBuf::new());

    let tokenizer_config_path = repo
        .get("tokenizer_config.json")
        .unwrap_or_else(|_| std::path::PathBuf::new());

    Ok((
        model_path,
        tokenizer_path,
        config_path,
        special_tokens_path,
        tokenizer_config_path,
    ))
}

/// Get or initialize an embedding engine from cache.
///
/// Downloads model files from HuggingFace if needed, loads the tokenizer,
/// creates an ORT session, and caches the engine for reuse.
fn get_or_init_engine(
    repo_name: &str,
    model_file: &str,
    pooling: engine::Pooling,
    cache_dir: Option<std::path::PathBuf>,
) -> crate::Result<Arc<EmbeddingEngine>> {
    let cache_directory = resolve_cache_dir(cache_dir);
    let engine_key = format!(
        "{repo_name}_{model_file}_{cache_directory}",
        cache_directory = cache_directory.display()
    );

    // Fast path: read lock
    {
        match ENGINE_CACHE.read() {
            Ok(cache) => {
                if let Some(cached) = cache.get(&engine_key) {
                    return Ok(Arc::clone(cached));
                }
            }
            Err(poison_error) => {
                let cache = poison_error.get_ref();
                if let Some(cached) = cache.get(&engine_key) {
                    return Ok(Arc::clone(cached));
                }
            }
        }
    }

    // Slow path: write lock + initialization
    {
        let mut cache = match ENGINE_CACHE.write() {
            Ok(guard) => guard,
            Err(poison_error) => poison_error.into_inner(),
        };

        // Double-check after acquiring write lock
        if let Some(cached) = cache.get(&engine_key) {
            return Ok(Arc::clone(cached));
        }

        crate::ort_discovery::ensure_ort_available();

        // Download model files
        let (model_path, tokenizer_path, config_path, special_tokens_path, tokenizer_config_path) =
            std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
                download_model_files(repo_name, model_file, &cache_directory)
            }))
            .map_err(|panic_payload| {
                let panic_msg = panic_to_string(panic_payload);
                if looks_like_ort_error(&panic_msg) {
                    crate::KreuzbergError::MissingDependency(format!(
                        "ONNX Runtime - {}",
                        onnx_runtime_install_message()
                    ))
                } else {
                    crate::KreuzbergError::embedding(format!("Model download panicked: {panic_msg}"))
                }
            })??;

        // Load tokenizer
        let tokenizer = load_tokenizer(
            &tokenizer_path,
            &config_path,
            &special_tokens_path,
            &tokenizer_config_path,
            512, // default max_length
        )?;

        // Create ORT session
        let thread_budget = crate::core::config::concurrency::resolve_thread_budget(None);
        let session = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
            let mut builder = ort::session::Session::builder()?;
            builder = builder
                .with_optimization_level(ort::session::builder::GraphOptimizationLevel::Level3)
                .map_err(|e| ort::Error::new(e.message()))?;
            builder = builder
                .with_intra_threads(thread_budget)
                .map_err(|e| ort::Error::new(e.message()))?;
            builder = builder
                .with_inter_threads(1)
                .map_err(|e| ort::Error::new(e.message()))?;
            builder.commit_from_file(&model_path)
        }))
        .map_err(|panic_payload| {
            let panic_msg = panic_to_string(panic_payload);
            if looks_like_ort_error(&panic_msg) {
                crate::KreuzbergError::MissingDependency(format!("ONNX Runtime - {}", onnx_runtime_install_message()))
            } else {
                crate::KreuzbergError::embedding(format!("ONNX Runtime initialization panicked: {panic_msg}"))
            }
        })?
        .map_err(|e| {
            let error_msg = e.to_string();
            if looks_like_ort_error(&error_msg) {
                crate::KreuzbergError::MissingDependency(format!("ONNX Runtime - {}", onnx_runtime_install_message()))
            } else {
                crate::KreuzbergError::embedding(format!("Failed to create ONNX session: {e}"))
            }
        })?;

        let new_engine = Arc::new(EmbeddingEngine::new(tokenizer, session, pooling));
        cache.insert(engine_key, Arc::clone(&new_engine));

        Ok(new_engine)
    }
}

/// Check if an error message looks like an ONNX Runtime missing dependency.
fn looks_like_ort_error(msg: &str) -> bool {
    msg.contains("onnxruntime")
        || msg.contains("ORT")
        || msg.contains("libonnxruntime")
        || msg.contains("onnxruntime.dll")
        || msg.contains("Unable to load")
        || msg.contains("library load failed")
        || msg.contains("attempting to load")
        || msg.contains("An error occurred while")
}

/// Convert a panic payload to a string message.
fn panic_to_string(payload: Box<dyn std::any::Any + Send>) -> String {
    if let Some(s) = payload.downcast_ref::<&str>() {
        s.to_string()
    } else if let Some(s) = payload.downcast_ref::<String>() {
        s.clone()
    } else {
        "Unknown panic".to_string()
    }
}

/// Eagerly download and cache an embedding model without returning the handle.
///
/// This triggers the same download and initialization as `get_or_init_engine`
/// but discards the result, making it suitable for cache-warming scenarios
/// where the caller doesn't need to use the model immediately.
///
/// **Note**: This function downloads AND initializes the ONNX model, which
/// requires ONNX Runtime and uses significant memory. For download-only
/// scenarios (e.g., init containers), use [`download_model`] instead.
pub fn warm_model(
    model_type: &crate::core::config::EmbeddingModelType,
    cache_dir: Option<std::path::PathBuf>,
) -> crate::Result<()> {
    let (repo, model_file, pooling) = resolve_model_info(model_type)?;
    get_or_init_engine(repo, model_file, pooling, cache_dir).map(|_| ())
}

/// Download an embedding model's files without initializing ONNX Runtime.
///
/// Downloads the model files (ONNX model, tokenizer, config) from HuggingFace
/// to the cache directory. Subsequent calls to `warm_model` or
/// `get_or_init_engine` will find the files cached and skip the download step.
///
/// This is ideal for init containers or CI environments where you want to
/// pre-populate the cache without loading models into memory.
pub fn download_model(
    model_type: &crate::core::config::EmbeddingModelType,
    cache_dir: Option<std::path::PathBuf>,
) -> crate::Result<()> {
    let (repo_name, model_file, _pooling) = resolve_model_info(model_type)?;
    let cache_directory = resolve_cache_dir(cache_dir);

    let files = &[
        model_file,
        "tokenizer.json",
        "config.json",
        "special_tokens_map.json",
        "tokenizer_config.json",
    ];

    tracing::info!(repo = %repo_name, "Downloading embedding model files (no ONNX init)");

    let api = hf_hub::api::sync::ApiBuilder::from_env()
        .with_cache_dir(cache_directory)
        .with_progress(true)
        .build()
        .map_err(|e| crate::KreuzbergError::embedding(format!("Failed to create HF API client: {e}")))?;

    let repo = api.model(repo_name.to_string());

    for file in files {
        match repo.get(file) {
            Ok(path) => tracing::debug!(file = %file, path = ?path, "Downloaded"),
            Err(e) => {
                // Model and tokenizer are required; others are optional
                if *file == model_file || *file == "tokenizer.json" {
                    return Err(crate::KreuzbergError::embedding(format!(
                        "Failed to download {file}: {e}"
                    )));
                }
                tracing::debug!(file = %file, error = %e, "Optional file not found, skipping");
            }
        }
    }

    tracing::info!(repo = %repo_name, "Embedding model files downloaded successfully");
    Ok(())
}

/// Normalize an embedding vector in-place (L2 normalization).
fn normalize_in_place(embedding: &mut [f32]) {
    let magnitude: f32 = embedding.iter().map(|x| x * x).sum::<f32>().sqrt();
    if magnitude > f32::EPSILON {
        let inv_mag = 1.0 / magnitude;
        embedding.iter_mut().for_each(|x| *x *= inv_mag);
    }
}

/// Apply normalization to a batch of embeddings (parallel for large batches).
fn normalize_embeddings(embeddings: &mut [Vec<f32>]) {
    const PARALLEL_THRESHOLD: usize = 64;
    if embeddings.len() >= PARALLEL_THRESHOLD {
        use rayon::prelude::*;
        embeddings.par_iter_mut().for_each(|v| normalize_in_place(v));
    } else {
        embeddings.iter_mut().for_each(|v| normalize_in_place(v));
    }
}

/// Generate embeddings for text chunks using the specified configuration.
///
/// This function modifies chunks in-place, populating their `embedding` field
/// with generated embedding vectors. It uses batch processing for efficiency.
///
/// # Arguments
///
/// * `chunks` - Mutable reference to vector of chunks to generate embeddings for
/// * `config` - Embedding configuration specifying model and parameters
///
/// # Returns
///
/// Returns `Ok(())` if embeddings were generated successfully, or an error if
/// model initialization or embedding generation fails.
pub fn generate_embeddings_for_chunks(
    chunks: &mut [crate::types::Chunk],
    config: &crate::core::config::EmbeddingConfig,
) -> crate::Result<()> {
    if chunks.is_empty() {
        return Ok(());
    }

    let texts: Vec<&str> = chunks.iter().map(|c| c.content.as_str()).collect();
    let embeddings_result = embed_texts(&texts, config)?;

    // Assign embeddings to chunks.
    for (chunk, embedding) in chunks.iter_mut().zip(embeddings_result) {
        chunk.embedding = Some(embedding);
    }

    Ok(())
}

/// Generate embeddings for a list of raw text strings (standalone, no chunking pipeline).
///
/// Returns one embedding vector per input text, in the same order as the input.
/// Uses the same model resolution, engine caching, and batch processing as the
/// chunking pipeline. Normalization is applied if `config.normalize` is true.
///
/// # Arguments
///
/// * `texts` - Slice of strings to embed
/// * `config` - Embedding configuration specifying model, batch size, and normalization
///
/// # Returns
///
/// Returns `Vec<Vec<f32>>` — one `Vec<f32>` per input text. Returns an empty
/// `Vec` if `texts` is empty (no error).
///
/// # Errors
///
/// - `KreuzbergError::MissingDependency` if ONNX Runtime is not installed
/// - `KreuzbergError::Embedding` if the preset name is unknown or model download fails
///
/// # Example
///
/// ```rust,ignore
/// use kreuzberg::{embed_texts, EmbeddingConfig, EmbeddingModelType};
///
/// let config = EmbeddingConfig {
///     model: EmbeddingModelType::Preset { name: "balanced".to_string() },
///     normalize: true,
///     ..Default::default()
/// };
/// let embeddings = embed_texts(&["Hello, world!", "Second text"], &config)?;
/// assert_eq!(embeddings.len(), 2);
/// assert_eq!(embeddings[0].len(), 768); // balanced preset = 768 dims
/// ```
pub fn embed_texts<T: AsRef<str>>(
    texts: &[T],
    config: &crate::core::config::EmbeddingConfig,
) -> crate::Result<Vec<Vec<f32>>> {
    if texts.is_empty() {
        return Ok(Vec::new());
    }

    // Validate that no individual text is empty — empty strings produce
    // meaningless embeddings and can cause tokenizer edge-cases.
    for (i, t) in texts.iter().enumerate() {
        if t.as_ref().is_empty() {
            return Err(crate::KreuzbergError::embedding(format!(
                "Text at position {pos} is empty. All texts must be non-empty.",
                pos = i + 1
            )));
        }
    }

    // Dispatch: LLM-hosted embeddings bypass the local ONNX engine entirely.
    match &config.model {
        #[cfg(feature = "liter-llm")]
        crate::core::config::EmbeddingModelType::Llm { llm } => {
            let normalize = config.normalize;
            // Create a dedicated runtime for the sync LLM call to avoid deadlocking
            // the caller's runtime. This is only hit from the sync embed_texts() path.
            let rt = tokio::runtime::Builder::new_current_thread()
                .enable_all()
                .build()
                .map_err(|e| {
                    crate::KreuzbergError::embedding(format!("Failed to create runtime for LLM embeddings: {e}"))
                })?;
            rt.block_on(crate::llm::vlm_embeddings::embed_via_llm(texts, llm, normalize))
        }
        #[cfg(not(feature = "liter-llm"))]
        crate::core::config::EmbeddingModelType::Llm { .. } => Err(crate::KreuzbergError::MissingDependency(
            "LLM embeddings require the 'liter-llm' feature. Rebuild with --features liter-llm".into(),
        )),
        _ => {
            // Local ONNX path for Preset and Custom model types.
            let chunk_count = texts.len();
            let (repo, model_file, pooling) = resolve_model_info(&config.model)?;
            let engine = get_or_init_engine(repo, model_file, pooling, config.cache_dir.clone())?;

            let text_refs: Vec<&str> = texts.iter().map(|t| t.as_ref()).collect();
            let mut embeddings = engine.embed(&text_refs, config.batch_size).map_err(|e| {
                crate::KreuzbergError::embedding(format!(
                    "Failed to generate embeddings for {chunk_count} texts (model={:?}, batch_size={}): {e}",
                    config.model, config.batch_size
                ))
            })?;

            if config.normalize {
                normalize_embeddings(&mut embeddings);
            }

            Ok(embeddings)
        }
    }
}

/// Generate embeddings asynchronously for a list of text strings.
///
/// This is the async counterpart to [`embed_texts`]. It offloads the blocking
/// ONNX inference work to a dedicated blocking thread pool via Tokio's
/// `spawn_blocking`, keeping the async executor free.
///
/// Returns one embedding vector per input text in the same order.
///
/// # Arguments
///
/// * `texts` - Vec of strings to embed (owned, sent to blocking thread)
/// * `config` - Embedding configuration specifying model, batch size, and normalization
///
/// # Errors
///
/// - `KreuzbergError::MissingDependency` if ONNX Runtime is not installed
/// - `KreuzbergError::Embedding` if the preset name is unknown, model download fails,
///   or the blocking inference task panics
///
/// # Example
///
/// ```rust,ignore
/// use kreuzberg::{embed_texts_async, EmbeddingConfig};
///
/// let embeddings = embed_texts_async(
///     vec!["Hello!".to_string()],
///     &EmbeddingConfig::default(),
/// ).await?;
/// ```
#[cfg(feature = "tokio-runtime")]
pub async fn embed_texts_async<T: AsRef<str> + Send + 'static>(
    texts: Vec<T>,
    config: &crate::core::config::EmbeddingConfig,
) -> crate::Result<Vec<Vec<f32>>> {
    if texts.is_empty() {
        return Ok(Vec::new());
    }

    // LLM-hosted embeddings can be awaited directly — no need for spawn_blocking.
    #[cfg(feature = "liter-llm")]
    if let crate::core::config::EmbeddingModelType::Llm { llm } = &config.model {
        return crate::llm::vlm_embeddings::embed_via_llm(&texts, llm, config.normalize).await;
    }

    #[cfg(not(feature = "liter-llm"))]
    if let crate::core::config::EmbeddingModelType::Llm { .. } = &config.model {
        return Err(crate::KreuzbergError::MissingDependency(
            "LLM embeddings require the 'liter-llm' feature. Rebuild with --features liter-llm".into(),
        ));
    }

    // Acquire a permit from the global semaphore to limit concurrent ONNX
    // inference calls, preventing resource exhaustion under high fan-out.
    let _permit = EMBED_SEMAPHORE
        .acquire()
        .await
        .map_err(|_| crate::KreuzbergError::embedding("Embedding semaphore closed".to_string()))?;

    // Wrap config in Arc to avoid cloning the entire struct (strings, PathBuf)
    // into the blocking closure.
    let config = Arc::new(config.clone());
    tokio::task::spawn_blocking(move || embed_texts(&texts, &config))
        .await
        .map_err(|e| crate::KreuzbergError::embedding(format!("Embedding task panicked: {e}")))?
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_get_preset() {
        assert!(get_preset("balanced").is_some());
        assert!(get_preset("fast").is_some());
        assert!(get_preset("quality").is_some());
        assert!(get_preset("multilingual").is_some());
        assert!(get_preset("nonexistent").is_none());
    }

    #[test]
    fn test_list_presets() {
        let presets = list_presets();
        assert_eq!(presets.len(), 4);
        assert!(presets.contains(&"fast"));
        assert!(presets.contains(&"balanced"));
        assert!(presets.contains(&"quality"));
        assert!(presets.contains(&"multilingual"));
    }

    #[test]
    fn test_preset_dimensions() {
        let balanced = get_preset("balanced").unwrap();
        assert_eq!(balanced.dimensions, 768);

        let fast = get_preset("fast").unwrap();
        assert_eq!(fast.dimensions, 384);

        let quality = get_preset("quality").unwrap();
        assert_eq!(quality.dimensions, 1024);
    }

    #[test]
    fn test_preset_chunk_sizes() {
        let fast = get_preset("fast").unwrap();
        assert_eq!(fast.chunk_size, 512);
        assert_eq!(fast.overlap, 50);

        let quality = get_preset("quality").unwrap();
        assert_eq!(quality.chunk_size, 2000);
        assert_eq!(quality.overlap, 200);
    }

    #[test]
    fn test_preset_model_repos() {
        let fast = get_preset("fast").unwrap();
        assert_eq!(fast.model_repo, "Xenova/all-MiniLM-L6-v2");
        assert_eq!(fast.pooling, "mean");
        assert_eq!(fast.model_file, "onnx/model_quantized.onnx");

        let balanced = get_preset("balanced").unwrap();
        assert_eq!(balanced.model_repo, "Xenova/bge-base-en-v1.5");
        assert_eq!(balanced.pooling, "cls");
    }

    #[test]
    fn test_embed_texts_rejects_empty_string() {
        let config = crate::core::config::EmbeddingConfig::default();
        let texts = vec!["valid", ""];
        let err = embed_texts(&texts, &config).unwrap_err();
        let msg = err.to_string();
        assert!(
            msg.contains("position 2"),
            "Error should identify the empty text position, got: {msg}"
        );
        assert!(msg.contains("empty"), "Error should mention empty text, got: {msg}");
    }

    #[test]
    fn test_embed_texts_empty_list_returns_empty() {
        let config = crate::core::config::EmbeddingConfig::default();
        let texts: Vec<&str> = vec![];
        let result = embed_texts(&texts, &config).unwrap();
        assert!(result.is_empty());
    }

    #[test]
    fn test_embed_texts_rejects_first_empty_string() {
        let config = crate::core::config::EmbeddingConfig::default();
        let texts = vec![""];
        let err = embed_texts(&texts, &config).unwrap_err();
        assert!(err.to_string().contains("position 1"));
    }
}