use std::collections::{HashMap, HashSet};
use std::fs;
use std::path::{Path, PathBuf};
use std::sync::Mutex;

use axum::Json;
use log::{error, info, warn};
use once_cell::sync::Lazy;
use qdrant_edge::external::serde_json::{json, Value};
use qdrant_edge::external::uuid::Uuid;
use qdrant_edge::{
    Condition, Distance, EdgeConfig, EdgeOptimizersConfig, EdgeShard, EdgeVectorParams,
    FieldCondition, Filter, HnswIndexConfig, Match, MatchValue, NamedQuery, Payload, PointId,
    PointInsertOperations, PointOperations, PointStruct, QueryEnum, QueryRequest, ScoredPoint,
    ScoringQuery, UpdateOperation, ValueVariants, VectorInternal, Vectors, WithPayloadInterface,
    WithVector,
};
use serde::{Deserialize, Serialize};
use tauri::Manager;

use crate::api_token::APIToken;
use crate::environment::DATA_DIRECTORY;
use crate::metadata::META_DATA;

const VECTOR_NAME: &str = "embedding";
const HNSW_M: usize = 16;
const HNSW_EF_CONSTRUCT: usize = 100;
const HNSW_FULL_SCAN_THRESHOLD_KB: usize = 10_000;
const HNSW_MAX_INDEXING_THREADS: usize = 0;
const VECTOR_INDEXING_THRESHOLD_KB: usize = 10_000;
const STORE_INITIALIZATION_MARKER: &str = "store_name.txt";
const STORE_INITIALIZATION_MARKER_TEMP: &str = "store_name.tmp";
const STORE_DISPLAY_NAME_MARKER: &str = "data_source_name.txt";
const STORE_DISPLAY_NAME_MARKER_TEMP: &str = "data_source_name.tmp";

/// Marks a response whose store exists on disk but cannot be opened. The .NET side keys its repair
/// offer off this value instead of parsing `issue`, so rewording the message stays harmless.
const ISSUE_CODE_STORE_UNREADABLE: &str = "store-unreadable";

type QdrantEdgeResult<T> = Result<T, Box<dyn std::error::Error + Send + Sync>>;

static QDRANT_EDGE_DATABASE: Lazy<Mutex<Option<QdrantEdgeDatabase>>> =
    Lazy::new(|| Mutex::new(None));

static QDRANT_EDGE_STATUS: Lazy<Mutex<QdrantEdgeStatusInfo>> =
    Lazy::new(|| Mutex::new(QdrantEdgeStatusInfo::default()));

#[derive(Default)]
struct QdrantEdgeStatusInfo {
    status: QdrantEdgeStatus,
    unavailable_reason: Option<String>,
}

#[derive(Clone, Copy, Default, Serialize, PartialEq, Eq)]
pub enum QdrantEdgeStatus {
    #[default]
    Starting,
    Available,
    Unavailable,
}

#[derive(Serialize)]
pub struct QdrantEdgeServiceInfo {
    pub status: QdrantEdgeStatus,
    pub name: String,
    pub version: String,
    pub path: String,
    pub stores_count: usize,
    pub is_available: bool,
    pub unavailable_reason: Option<String>,
}

#[derive(Clone, Deserialize)]
pub struct QdrantEdgeStoragePoint {
    pub point_id: String,
    pub vector: Vec<f32>,
    pub data_source_id: String,
    pub data_source_type: String,
    pub chunk_id: String,
    pub parent_file_id: String,
    pub file_path: String,
    pub absolute_path: String,
    pub file_name: String,
    pub relative_path: String,
    pub file_type: String,
    pub page_number: Option<i32>,
    pub chunk_index: i32,
    pub text: String,
    pub fingerprint: String,
    pub creation_utc: String,
    pub last_write_utc: String,
    pub embedded_at_utc: String,
}

#[derive(Deserialize)]
pub struct EnsureQdrantEdgeStoreRequest {
    pub store_name: String,
    pub data_source_name: String,
    pub vector_size: usize,
}

#[derive(Deserialize)]
pub struct InsertQdrantEdgeEmbeddingRequest {
    pub store_name: String,
    pub points: Vec<QdrantEdgeStoragePoint>,
}

#[derive(Deserialize)]
pub struct SearchQdrantEdgeEmbeddingRequest {
    pub store_name: String,
    pub vector: Vec<f32>,
    pub max_matches: usize,
}

#[derive(Deserialize)]
pub struct DeleteQdrantEdgeEmbeddingByFileRequest {
    pub store_name: String,
    pub file_path: String,
}

#[derive(Deserialize)]
pub struct OptimizeQdrantEdgeStoreRequest {
    pub store_name: String,
}

#[derive(Deserialize)]
pub struct DeleteQdrantEdgeStoreRequest {
    pub store_name: String,
}

#[derive(Serialize)]
pub struct QdrantEdgeResponse<T> {
    pub success: bool,
    pub issue: String,
    pub issue_code: &'static str,
    pub data: Option<T>,
}

/// A vector store which is initialized on disk but which Qdrant Edge refuses to open.
///
/// This is deliberately its own error type rather than one more formatted string: a broken store
/// is the one failure the user can act on, and the request layer has to recognize it to label the
/// response. Nothing here deletes the store -- rebuilding the embeddings costs the user time and,
/// with a cloud embedding provider, money, so that stays their decision.
#[derive(Debug)]
struct StoreUnreadableError {
    store_name: String,
    message: String,
}

impl StoreUnreadableError {
    fn new(store_name: &str, path: &Path, source: impl std::fmt::Display) -> Self {
        Self {
            store_name: store_name.to_string(),
            message: format!("Failed to load vector store '{store_name}' from '{}': {source}", path.display()),
        }
    }
}

impl std::fmt::Display for StoreUnreadableError {
    fn fmt(&self, formatter: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        formatter.write_str(&self.message)
    }
}

impl std::error::Error for StoreUnreadableError {}

#[derive(Serialize)]
pub struct QdrantEdgeEnsureStoreResult {
    pub created: bool,
}

#[derive(Serialize)]
pub struct QdrantEdgeSearchResult {
    pub point_id: String,
    pub score: f32,
    pub data_source_id: String,
    pub data_source_type: String,
    pub chunk_id: String,
    pub parent_file_id: String,
    pub file_path: String,
    pub absolute_path: String,
    pub file_name: String,
    pub relative_path: String,
    pub file_type: String,
    pub page_number: Option<i32>,
    pub chunk_index: i32,
    pub text: String,
    pub fingerprint: String,
    pub creation_utc: String,
    pub last_write_utc: String,
    pub embedded_at_utc: String,
}

#[derive(Clone, Serialize)]
pub struct QdrantEdgeInfo {
    pub name: String,
    pub version: String,
    pub path: String,
    pub stores_count: usize,
}

pub struct QdrantEdgeDatabase {
    base_path: PathBuf,
    shards: HashMap<String, EdgeShard>,

    /// Stores whose unreadability has already been logged. A broken store is hit by every single
    /// request against it, and one log line per request would bury everything else.
    reported_unreadable_stores: HashSet<String>,
}

impl QdrantEdgeDatabase {
    pub fn new(base_path: PathBuf) -> Self {
        Self {
            base_path,
            shards: HashMap::new(),
            reported_unreadable_stores: HashSet::new(),
        }
    }

    /// Whether this store's defect still has to be written to the log. True exactly once per store,
    /// until the store loads again.
    fn report_unreadable_store(&mut self, store_name: &str) -> bool {
        self.reported_unreadable_stores.insert(store_name.to_string())
    }

    fn store_path(&self, store_name: &str) -> QdrantEdgeResult<PathBuf> {
        validate_store_name(store_name)?;
        Ok(self.base_path.join("stores").join(store_directory_name(store_name)))
    }

    // To ensure a shard exists and that you can insert a vector
    fn get_or_create_store(&mut self, store_name: &str, vector_size: usize) -> QdrantEdgeResult<(&EdgeShard, bool)> {
        let (path, is_initialized) = self.reconcile_store_state(store_name)?;
        if self.shards.contains_key(store_name) {
            return Ok((self.shards.get(store_name).unwrap(), false));
        }

        let shard = if is_initialized {
            match EdgeShard::load(&path, None) {
                Ok(shard) => shard,
                Err(error) => return Err(StoreUnreadableError::new(store_name, &path, error).into()),
            }
        } else {
            fs::create_dir_all(&path).map_err(|error| {
                format!("Failed to create directory for vector store '{store_name}' at '{}': {error}", path.display())
            })?;
            let shard = match EdgeShard::new(&path, edge_config(vector_size)) {
                Ok(shard) => shard,
                Err(error) => {
                    let cleanup_issue = remove_partial_store(&path);
                    return Err(format!("Failed to create vector store '{store_name}' at '{}': {error}{cleanup_issue}", path.display()).into());
                },
            };

            if let Err(error) = write_store_initialization_marker(&path, store_name) {
                drop(shard);
                let cleanup_issue = remove_partial_store(&path);
                return Err(format!("Failed to finalize vector store '{store_name}' at '{}': {error}{cleanup_issue}", path.display()).into());
            }

            shard
        };

        self.reported_unreadable_stores.remove(store_name);
        self.shards.insert(store_name.to_string(), shard);
        Ok((self.shards.get(store_name).unwrap(), !is_initialized))
    }

    // To check whether a shard exists so you can delete a file from it
    fn get_existing_store(&mut self, store_name: &str) -> QdrantEdgeResult<Option<&EdgeShard>> {
        let (path, is_initialized) = self.reconcile_store_state(store_name)?;
        if self.shards.contains_key(store_name) {
            return Ok(self.shards.get(store_name));
        }

        if !is_initialized {
            return Ok(None);
        }

        let shard = match EdgeShard::load(&path, None) {
            Ok(shard) => shard,
            Err(error) => return Err(StoreUnreadableError::new(store_name, &path, error).into()),
        };

        self.reported_unreadable_stores.remove(store_name);
        self.shards.insert(store_name.to_string(), shard);
        Ok(self.shards.get(store_name))
    }

    fn reconcile_store_state(&mut self, store_name: &str) -> QdrantEdgeResult<(PathBuf, bool)> {
        let path = self.store_path(store_name)?;
        let is_initialized = store_is_initialized(&path, store_name)?;

        if self.shards.contains_key(store_name) && !is_initialized {
            warn!(Source = "Qdrant Edge"; "Removing stale cached vector store '{}' because its initialized data directory no longer exists.", store_name);
            self.shards.remove(store_name);
        }

        if path.exists() && !is_initialized {
            warn!(Source = "Qdrant Edge"; "Removing incompletely initialized vector store '{}' before continuing.", store_name);
            fs::remove_dir_all(&path).map_err(|error| {
                format!("Failed to remove incomplete vector store '{store_name}' at '{}': {error}", path.display())
            })?;
        }

        Ok((path, is_initialized))
    }

    fn info(&self) -> QdrantEdgeResult<QdrantEdgeInfo> {
        let stores_path = self.base_path.join("stores");
        let stores_count = if stores_path.exists() {
            fs::read_dir(stores_path)?
                .filter_map(Result::ok)
                .filter(|entry| entry.path().join(STORE_INITIALIZATION_MARKER).is_file())
                .count()
        } else {
            0
        };

        Ok(QdrantEdgeInfo {
            name: "Qdrant Edge".to_string(),
            version: vector_store_version()?,
            path: self.base_path.to_string_lossy().to_string(),
            stores_count,
        })
    }

    fn ensure_store_exists(&mut self, store_name: &str, data_source_name: &str, vector_size: usize) -> QdrantEdgeResult<QdrantEdgeEnsureStoreResult> {
        validate_vector_size(vector_size)?;
        validate_data_source_name(data_source_name)?;
        let store_path = self.store_path(store_name)?;
        let (_, created) = self.get_or_create_store(store_name, vector_size)?;
        write_store_display_name(&store_path, data_source_name)?;
        Ok(QdrantEdgeEnsureStoreResult {
            created,
        })
    }

    fn insert_embedding(&mut self, store_name: &str, points: Vec<QdrantEdgeStoragePoint>) -> QdrantEdgeResult<()> {
        let Some(first_point) = points.first() else {
            return Ok(());
        };

        let vector_size = first_point.vector.len();
        validate_vector_size(vector_size)?;
        if points.iter().any(|point| point.vector.len() != vector_size) {
            return Err("All vectors in one insert request must have the same size.".into());
        }

        let (shard, _) = self.get_or_create_store(store_name, vector_size)?;
        let points = points
            .into_iter()
            .map(to_qdrant_edge_point)
            .collect::<QdrantEdgeResult<Vec<_>>>()?;

        shard.update(UpdateOperation::PointOperation(
            PointOperations::UpsertPoints(PointInsertOperations::PointsList(points)),
        ))?;
        shard.flush()?;
        Ok(())
    }

    fn search_embedding(&mut self, store_name: &str, vector: Vec<f32>, max_matches: usize) -> QdrantEdgeResult<Vec<QdrantEdgeSearchResult>> {
        if max_matches == 0 {
            return Ok(vec![]);
        }

        validate_vector_size(vector.len())?;
        let Some(shard) = self.get_existing_store(store_name)? else {
            return Ok(vec![]);
        };

        let search_results = shard.query(QueryRequest {
            prefetches: Vec::new(),
            query: Some(ScoringQuery::Vector(QueryEnum::Nearest(NamedQuery::new(
                VectorInternal::Dense(vector),
                VECTOR_NAME,
            )))),
            filter: None,
            score_threshold: None,
            limit: max_matches,
            offset: 0,
            params: None,
            with_vector: WithVector::Bool(false),
            with_payload: WithPayloadInterface::Bool(true),
        })?;

        Ok(search_results
            .into_iter()
            .map(to_qdrant_edge_search_result)
            .collect())
    }

    fn delete_embedding_by_file(&mut self, store_name: &str, file_path: &str) -> QdrantEdgeResult<()> {
        let Some(shard) = self.get_existing_store(store_name)? else {
            return Ok(());
        };

        shard.update(UpdateOperation::PointOperation(
            PointOperations::DeletePointsByFilter(match_keyword_filter("file_path", file_path)?),
        ))?;
        shard.flush()?;
        Ok(())
    }

    fn optimize_store(&mut self, store_name: &str) -> QdrantEdgeResult<()> {
        let Some(shard) = self.get_existing_store(store_name)? else {
            return Ok(());
        };

        let optimized = shard.optimize()?;
        if optimized {
            info!(Source = "Qdrant Edge"; "Optimized vector store '{}'.", store_name);
        }
        shard.flush()?;
        Ok(())
    }

    fn delete_store(&mut self, store_name: &str) -> QdrantEdgeResult<()> {
        self.shards.remove(store_name);

        let path = self.store_path(store_name)?;
        if path.exists() {
            fs::remove_dir_all(path)?;
        }

        Ok(())
    }

    fn base_path(&self) -> PathBuf {
        self.base_path.clone()
    }
}

fn store_directory_name(store_name: &str) -> String {
    let stable_id = store_name.strip_prefix("rag_").unwrap_or(store_name);
    format!("store_{stable_id}")
}

fn qdrant_edge_base_path() -> QdrantEdgeResult<PathBuf> {
    let data_directory = DATA_DIRECTORY
        .get()
        .ok_or("The data directory has not been initialized.")?;

    Ok(Path::new(data_directory)
        .join("databases")
        .join("vector_database"))
}

pub async fn qdrant_edge_info(_token: APIToken) -> Json<QdrantEdgeServiceInfo> {
    let status = QDRANT_EDGE_STATUS.lock().unwrap();
    let current_status = status.status;
    let unavailable_reason = status.unavailable_reason.clone();
    drop(status);

    let database_guard = QDRANT_EDGE_DATABASE.lock().unwrap();
    let database_info = database_guard
        .as_ref()
        .and_then(|database| database.info().ok());

    let is_available = current_status == QdrantEdgeStatus::Available && database_info.is_some();
    Json(QdrantEdgeServiceInfo {
        status: current_status,
        name: database_info.as_ref().map(|info| info.name.clone()).unwrap_or_default(),
        version: database_info.as_ref().map(|info| info.version.clone()).unwrap_or_default(),
        path: database_info.as_ref().map(|info| info.path.clone()).unwrap_or_default(),
        stores_count: database_info.as_ref().map(|info| info.stores_count).unwrap_or_default(),
        is_available,
        unavailable_reason,
    })
}

pub async fn ensure_qdrant_edge_store(_token: APIToken, Json(request): Json<EnsureQdrantEdgeStoreRequest>) -> Json<QdrantEdgeResponse<QdrantEdgeEnsureStoreResult>> {
    execute_qdrant_edge_request(|database| {
        database.ensure_store_exists(&request.store_name, &request.data_source_name, request.vector_size)
    })
}

pub async fn insert_qdrant_edge_embedding(_token: APIToken, Json(request): Json<InsertQdrantEdgeEmbeddingRequest>) -> Json<QdrantEdgeResponse<()>> {
    execute_qdrant_edge_request(|database| {
        database.insert_embedding(&request.store_name, request.points)
    })
}

pub async fn search_qdrant_edge_embeddings(_token: APIToken, Json(request): Json<SearchQdrantEdgeEmbeddingRequest>) -> Json<QdrantEdgeResponse<Vec<QdrantEdgeSearchResult>>> {
    execute_qdrant_edge_request(|database| {
        database.search_embedding(&request.store_name, request.vector, request.max_matches)
    })
}

pub async fn delete_qdrant_edge_embedding_by_file(_token: APIToken, Json(request): Json<DeleteQdrantEdgeEmbeddingByFileRequest>) -> Json<QdrantEdgeResponse<()>> {
    execute_qdrant_edge_request(|database| {
        database.delete_embedding_by_file(&request.store_name, &request.file_path)
    })
}

pub async fn optimize_qdrant_edge_store(_token: APIToken, Json(request): Json<OptimizeQdrantEdgeStoreRequest>) -> Json<QdrantEdgeResponse<()>> {
    execute_qdrant_edge_request(|database| {
        database.optimize_store(&request.store_name)
    })
}

pub async fn delete_qdrant_edge_store(_token: APIToken, Json(request): Json<DeleteQdrantEdgeStoreRequest>) -> Json<QdrantEdgeResponse<()>> {
    execute_qdrant_edge_request(|database| {
        database.delete_store(&request.store_name)
    })
}

pub fn start_qdrant_edge_database<R: tauri::Runtime>(app_handle: tauri::AppHandle<R>) {
    set_qdrant_edge_starting();
    remove_obsolete_qdrant_sidecar_files(&app_handle);

    let path = match qdrant_edge_base_path() {
        Ok(path) => path,
        Err(e) => {
            let reason = format!("Qdrant Edge cannot be started: {e}");
            error!(Source = "Qdrant Edge"; "{reason}");
            set_qdrant_edge_unavailable(reason);
            return;
        },
    };

    match fs::create_dir_all(&path) {
        Ok(_) => {
            let database = QdrantEdgeDatabase::new(path.clone());
            *QDRANT_EDGE_DATABASE.lock().unwrap() = Some(database);
            set_qdrant_edge_available();
            info!(Source = "Qdrant Edge"; "Qdrant Edge is available at '{}'.", path.display());
        },
        Err(e) => {
            let reason = format!("The Qdrant Edge data directory could not be created: {e}");
            error!(Source = "Qdrant Edge"; "{reason}");
            set_qdrant_edge_unavailable(reason);
        },
    }
}

pub fn stop_qdrant_edge_database() {
    if let Some(database) = QDRANT_EDGE_DATABASE.lock().unwrap().take() {
        info!(Source = "Qdrant Edge"; "Stopping Qdrant Edge at '{}'.", database.base_path().display());
        drop(database);
    }

    set_qdrant_edge_unavailable("Qdrant Edge was stopped.".to_string());
}

fn execute_qdrant_edge_request<T, F>(operation: F) -> Json<QdrantEdgeResponse<T>>
where
    T: Serialize,
    F: FnOnce(&mut QdrantEdgeDatabase) -> QdrantEdgeResult<T>,
{
    let mut database_guard = QDRANT_EDGE_DATABASE.lock().unwrap();
    let Some(database) = database_guard.as_mut() else {
        return Json(QdrantEdgeResponse {
            success: false,
            issue: "Qdrant Edge is not available.".to_string(),
            issue_code: "",
            data: None,
        });
    };

    match operation(database) {
        Ok(data) => Json(QdrantEdgeResponse {
            success: true,
            issue: String::new(),
            issue_code: "",
            data: Some(data),
        }),
        Err(e) => {
            let issue = e.to_string();

            //
            // An unreadable store keeps failing for as long as the user leaves it alone, so it is
            // logged once and then only answered. Every other failure is logged as it happens,
            // because those are one-offs worth seeing each time.
            //
            let issue_code = match e.downcast_ref::<StoreUnreadableError>() {
                Some(unreadable) => {
                    if database.report_unreadable_store(&unreadable.store_name) {
                        error!(Source = "Qdrant Edge"; "Qdrant Edge request failed: {issue}");
                    }

                    ISSUE_CODE_STORE_UNREADABLE
                },

                None => {
                    error!(Source = "Qdrant Edge"; "Qdrant Edge request failed: {issue}");
                    ""
                },
            };

            Json(QdrantEdgeResponse {
                success: false,
                issue,
                issue_code,
                data: None,
            })
        },
    }
}

fn set_qdrant_edge_available() {
    let mut status = QDRANT_EDGE_STATUS.lock().unwrap();
    status.status = QdrantEdgeStatus::Available;
    status.unavailable_reason = None;
}

fn set_qdrant_edge_starting() {
    let mut status = QDRANT_EDGE_STATUS.lock().unwrap();
    status.status = QdrantEdgeStatus::Starting;
    status.unavailable_reason = None;
}

fn set_qdrant_edge_unavailable(reason: String) {
    let mut status = QDRANT_EDGE_STATUS.lock().unwrap();
    status.status = QdrantEdgeStatus::Unavailable;
    status.unavailable_reason = Some(reason);
}

// Temporary compatibility shim until 2026-12-02:
// documentation/compatibility-shims/2026-06-qdrant-edge-migration.md
fn remove_obsolete_qdrant_sidecar_files<R: tauri::Runtime>(app_handle: &tauri::AppHandle<R>) {
    let mut paths = Vec::new();

    if let Some(data_directory) = DATA_DIRECTORY.get() {
        let databases_directory = Path::new(data_directory).join("databases");
        paths.push(databases_directory.join("qdrant"));
        paths.push(databases_directory.join("qdrant_test"));
    }

    if let Ok(resource_dir) = app_handle.path().resource_dir() {
        paths.push(resource_dir.join("target").join("databases").join("qdrant"));
        paths.push(resource_dir.join("resources").join("databases").join("qdrant"));
    }

    cfg_if::cfg_if! {
        if #[cfg(any(target_os = "windows", target_os = "macos"))]{
            if let Ok(current_exe) = std::env::current_exe() && let Some(exe_dir) = current_exe.parent()
                && exe_dir.to_string_lossy().contains("MindWork AI Studio") {
                paths.push(exe_dir.join("target").join("databases").join("qdrant"));
                paths.push(exe_dir.join("qdrant.exe"));
                paths.push(exe_dir.join("qdrant"));
            }
        }
    }

    for path in paths {
        remove_obsolete_qdrant_path(&path);
    }
}

fn remove_obsolete_qdrant_path(path: &Path) {
    if !path.exists() {
        info!(Source = "Qdrant Edge"; "Obsolete file or directory '{}' was not found.", path.display());
        return;
    }

    let result = if path.is_dir() {
        fs::remove_dir_all(path)
    } else {
        fs::remove_file(path)
    };

    match result {
        Ok(_) => warn!(Source = "Qdrant Edge"; "Removed obsolete Qdrant sidecar file or directory '{}'.", path.display()),
        Err(e) => warn!(Source = "Qdrant Edge"; "Could not remove obsolete Qdrant sidecar file or directory '{}': {e}", path.display()),
    }
}

fn edge_config(vector_size: usize) -> EdgeConfig {
    EdgeConfig {
        on_disk_payload: Some(true),
        vectors: HashMap::from([(
            VECTOR_NAME.to_string(),
            EdgeVectorParams {
                size: vector_size,
                distance: Distance::Cosine,
                on_disk: Some(true),
                quantization_config: None,
                multivector_config: None,
                datatype: None,
                hnsw_config: Some(hnsw_config()),
            },
        )]),
        sparse_vectors: HashMap::new(),
        hnsw_config: Some(hnsw_config()),
        quantization_config: None,
        optimizers: Some(edge_optimizers_config()),
        wal_options: None,
        max_search_threads: None,
        search_pool_core: None,
    }
}

// `on_disk` is deprecated in favor of `memory`, but Qdrant Edge does not re-export the `Memory`
// type, so the new field cannot be named from here. Leaving both unset is not an option either:
// the effective placement would fall back to cached instead of on-disk, which is a real change
// and would have the optimizers rebuild the HNSW graph.
#[allow(deprecated)]
fn hnsw_config() -> HnswIndexConfig {
    HnswIndexConfig {
        m: HNSW_M,
        ef_construct: HNSW_EF_CONSTRUCT,
        full_scan_threshold: HNSW_FULL_SCAN_THRESHOLD_KB,
        max_indexing_threads: HNSW_MAX_INDEXING_THREADS,
        on_disk: Some(true),
        memory: None,
        payload_m: None,
        inline_storage: None,
    }
}

fn edge_optimizers_config() -> EdgeOptimizersConfig {
    EdgeOptimizersConfig {
        indexing_threshold: Some(VECTOR_INDEXING_THRESHOLD_KB),
        prevent_unoptimized: Some(false),
        ..Default::default()
    }
}

fn store_is_initialized(path: &Path, store_name: &str) -> QdrantEdgeResult<bool> {
    if !path.join("edge_config.json").is_file() || !path.join("segments").is_dir() {
        return Ok(false);
    }

    let marker_path = path.join(STORE_INITIALIZATION_MARKER);
    if !marker_path.exists() {
        return Ok(false);
    }

    let initialized_store_name = fs::read_to_string(&marker_path).map_err(|error| {
        format!("Failed to read vector store initialization marker '{}': {error}", marker_path.display())
    })?;
    if initialized_store_name != store_name {
        return Err(format!("Vector store path collision at '{}': expected store '{}', but the path belongs to '{}'.", path.display(), store_name, initialized_store_name).into());
    }

    Ok(true)
}

fn write_store_initialization_marker(path: &Path, store_name: &str) -> std::io::Result<()> {
    write_store_marker(path, STORE_INITIALIZATION_MARKER, STORE_INITIALIZATION_MARKER_TEMP, store_name)
}

fn write_store_display_name(path: &Path, data_source_name: &str) -> std::io::Result<()> {
    write_store_marker(path, STORE_DISPLAY_NAME_MARKER, STORE_DISPLAY_NAME_MARKER_TEMP, data_source_name)
}

fn write_store_marker(path: &Path, marker_name: &str, temporary_marker_name: &str, value: &str) -> std::io::Result<()> {
    let marker_path = path.join(marker_name);
    if fs::read_to_string(&marker_path).is_ok_and(|current_value| current_value == value) {
        return Ok(());
    }

    let temporary_marker_path = path.join(temporary_marker_name);
    fs::write(&temporary_marker_path, value)?;
    if marker_path.exists() {
        fs::remove_file(&marker_path)?;
    }
    fs::rename(temporary_marker_path, marker_path)
}

fn remove_partial_store(path: &Path) -> String {
    match fs::remove_dir_all(path) {
        Ok(()) => String::new(),
        Err(error) => format!(" The incomplete store could not be removed: {error}"),
    }
}

fn validate_vector_size(vector_size: usize) -> QdrantEdgeResult<()> {
    if vector_size == 0 {
        return Err("Vector size must be greater than zero.".into());
    }

    Ok(())
}

fn validate_data_source_name(data_source_name: &str) -> QdrantEdgeResult<()> {
    const MAX_DATA_SOURCE_NAME_LENGTH: usize = 40;

    if data_source_name.trim().is_empty() {
        return Err("Data source name cannot be empty.".into());
    }

    if data_source_name.chars().count() > MAX_DATA_SOURCE_NAME_LENGTH {
        return Err(format!("Data source name exceeds the maximum length of {MAX_DATA_SOURCE_NAME_LENGTH} characters.").into());
    }

    if data_source_name.chars().any(|c| c.is_control()) {
        return Err("Data source name contains unsupported control characters.".into());
    }

    Ok(())
}

fn vector_store_version() -> QdrantEdgeResult<String> {
    let metadata = META_DATA
        .lock()
        .map_err(|_| "Metadata lock was poisoned.")?;
    let Some(metadata) = metadata.as_ref() else {
        return Err("Metadata was not initialized.".into());
    };

    Ok(metadata.vector_store_version.clone())
}

fn to_qdrant_edge_point(point: QdrantEdgeStoragePoint) -> QdrantEdgeResult<qdrant_edge::PointStructPersisted> {
    Ok(PointStruct::new(
        to_point_id(&point.point_id)?,
        Vectors::new_named([(VECTOR_NAME, point.vector)]),
        json!({
            "data_source_id": point.data_source_id,
            "data_source_type": point.data_source_type,
            "chunk_id": point.chunk_id,
            "parent_file_id": point.parent_file_id,
            "file_path": point.file_path,
            "absolute_path": point.absolute_path,
            "file_name": point.file_name,
            "relative_path": point.relative_path,
            "file_type": point.file_type,
            "page_number": point.page_number,
            "chunk_index": point.chunk_index,
            "text": point.text,
            "fingerprint": point.fingerprint,
            "creation_utc": point.creation_utc,
            "last_write_utc": point.last_write_utc,
            "embedded_at_utc": point.embedded_at_utc,
        }),
    )
    .into())
}

fn to_qdrant_edge_search_result(point: ScoredPoint) -> QdrantEdgeSearchResult {
    let payload = point.payload.unwrap_or_default();
    QdrantEdgeSearchResult {
        point_id: point_id_to_string(point.id),
        score: point.score,
        data_source_id: payload_string(&payload, "data_source_id"),
        data_source_type: payload_string(&payload, "data_source_type"),
        chunk_id: payload_string(&payload, "chunk_id"),
        parent_file_id: payload_string(&payload, "parent_file_id"),
        file_path: payload_string(&payload, "file_path"),
        absolute_path: payload_string(&payload, "absolute_path"),
        file_name: payload_string(&payload, "file_name"),
        relative_path: payload_string(&payload, "relative_path"),
        file_type: payload_string(&payload, "file_type"),
        page_number: payload_i32(&payload, "page_number"),
        chunk_index: payload_i32(&payload, "chunk_index").unwrap_or_default(),
        text: payload_string(&payload, "text"),
        fingerprint: payload_string(&payload, "fingerprint"),
        creation_utc: payload_string(&payload, "creation_utc"),
        last_write_utc: payload_string(&payload, "last_write_utc"),
        embedded_at_utc: payload_string(&payload, "embedded_at_utc"),
    }
}

fn to_point_id(point_id: &str) -> QdrantEdgeResult<PointId> {
    Uuid::parse_str(point_id)
        .map(PointId::Uuid)
        .map_err(|_| "Vector point ID must be a valid UUID.".into())
}

fn point_id_to_string(point_id: PointId) -> String {
    match point_id {
        PointId::NumId(id) => id.to_string(),
        PointId::Uuid(uuid) => uuid.to_string(),
    }
}

fn payload_string(payload: &Payload, key: &str) -> String {
    payload
        .0
        .get(key)
        .and_then(Value::as_str)
        .unwrap_or_default()
        .to_string()
}

fn payload_i32(payload: &Payload, key: &str) -> Option<i32> {
    payload
        .0
        .get(key)
        .and_then(Value::as_i64)
        .and_then(|value| i32::try_from(value).ok())
}

fn match_keyword_filter(field_name: &str, value: &str) -> QdrantEdgeResult<Filter> {
    Ok(Filter {
        should: None,
        min_should: None,
        must: Some(vec![Condition::Field(FieldCondition::new_match(
            field_name
                .try_into()
                .map_err(|_| format!("Invalid payload field name '{field_name}'."))?,
            Match::Value(MatchValue {
                value: ValueVariants::String(value.to_string()),
            }),
        ))]),
        must_not: None,
    })
}

fn validate_store_name(store_name: &str) -> QdrantEdgeResult<()> {
    const MAX_STORE_NAME_LENGTH: usize = 128;

    if store_name.is_empty() {
        return Err("Vector store name cannot be empty.".into());
    }

    if store_name.len() > MAX_STORE_NAME_LENGTH {
        return Err(format!("Vector store name exceeds the maximum length of {MAX_STORE_NAME_LENGTH} bytes.").into());
    }

    if store_name
        .chars()
        .all(|c| c.is_ascii_alphanumeric() || c == '_' || c == '-')
    {
        return Ok(());
    }

    Err(format!("Vector store name '{store_name}' contains unsupported characters.").into())
}

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

    #[test]
    fn validate_store_name_allows_safe_store_names() {
        assert!(validate_store_name("rag_1234-abcd").is_ok());
    }

    #[test]
    fn validate_store_name_rejects_path_syntax() {
        assert!(validate_store_name(".").is_err());
        assert!(validate_store_name("..").is_err());
        assert!(validate_store_name("../store").is_err());
        assert!(validate_store_name("store\\name").is_err());
    }

    #[test]
    fn validate_store_name_rejects_oversized_names() {
        assert!(validate_store_name(&"a".repeat(129)).is_err());
    }

    #[test]
    fn store_directory_name_contains_the_stable_data_source_id() {
        assert_eq!(
            store_directory_name("rag_6cc665a82b1e4d42bc748015b7b391ec"),
            "store_6cc665a82b1e4d42bc748015b7b391ec"
        );
    }

    #[test]
    fn validate_data_source_name_allows_display_names_but_rejects_invalid_values() {
        assert!(validate_data_source_name("Mäßig Confidence C#").is_ok());
        assert!(validate_data_source_name(" ").is_err());
        assert!(validate_data_source_name("invalid\nname").is_err());
        assert!(validate_data_source_name(&"a".repeat(41)).is_err());
    }

    #[test]
    fn ensure_store_reports_creation_and_updates_the_display_name() {
        let test_directory = std::env::temp_dir().join(format!(
            "ai-studio-qdrant-ensure-{}-{}",
            std::process::id(),
            std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap()
                .as_nanos()
        ));
        let store_name = "rag_6cc665a82b1e4d42bc748015b7b391ec";
        let mut database = QdrantEdgeDatabase::new(test_directory.clone());

        let created = database.ensure_store_exists(store_name, "Original name", 3).unwrap();
        assert!(created.created);

        let existing = database.ensure_store_exists(store_name, "Renamed source", 3).unwrap();
        assert!(!existing.created);
        let display_name_path = database.store_path(store_name).unwrap().join(STORE_DISPLAY_NAME_MARKER);
        assert_eq!(fs::read_to_string(display_name_path).unwrap(), "Renamed source");

        drop(database);
        fs::remove_dir_all(test_directory).unwrap();
    }

    #[test]
    fn an_unreadable_store_is_reported_but_never_deleted() {
        let test_directory = std::env::temp_dir().join(format!(
            "ai-studio-qdrant-unreadable-{}-{}",
            std::process::id(),
            std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap()
                .as_nanos()
        ));
        let store_name = "rag_6cc665a82b1e4d42bc748015b7b391ec";

        let mut database = QdrantEdgeDatabase::new(test_directory.clone());
        assert!(database.ensure_store_exists(store_name, "Some source", 3).unwrap().created);
        let store_path = database.store_path(store_name).unwrap();

        // Release the shard before breaking it, so the files are not held open any more.
        drop(database);
        fs::write(store_path.join("edge_config.json"), "this is not a config").unwrap();

        let mut database = QdrantEdgeDatabase::new(test_directory.clone());
        let error = database.get_existing_store(store_name).unwrap_err();
        assert!(
            error.downcast_ref::<StoreUnreadableError>().is_some(),
            "a store which cannot be opened has to be recognizable as such, not just a message"
        );

        // The whole point: the user's embeddings survive a defect until they ask for a rebuild.
        assert!(store_path.join("segments").is_dir());
        assert!(store_path.join(STORE_INITIALIZATION_MARKER).is_file());

        // And the defect is logged once, not once per request.
        assert!(database.report_unreadable_store(store_name));
        assert!(!database.report_unreadable_store(store_name));

        fs::remove_dir_all(test_directory).unwrap();
    }

    #[test]
    fn point_ids_must_be_valid_uuids() {
        assert!(to_point_id("6cc665a8-2b1e-4d42-bc74-8015b7b391ec").is_ok());
        assert!(to_point_id("deliberate-collision-input").is_err());
    }
}