use anyhow::Result;
use bytes::Bytes;
use futures_core::Stream;
use http_body_util::BodyExt;
use hyper::body::Incoming;
use hyper::server::conn::http1;
use hyper::service::service_fn;
use hyper::{Method, Request, Response, StatusCode};
use hyper_util::rt::TokioIo;
use std::collections::HashMap;
use std::net::SocketAddr;
use std::pin::Pin;
use std::sync::Arc;
use std::task::{Context, Poll};
use tokio::io::AsyncReadExt;
use tokio::net::TcpListener;
use tokio::sync::watch;
use tokio_util::io::ReaderStream;
use uuid::Uuid;

use crate::action::{self, RequestContext, S3Action};
use crate::auth::{self, AuthenticatedIdentity};
use crate::config::S3Config;
use crate::policy::{self, PolicyDecision, PolicyStore};
use crate::s3_error::S3Error;
use crate::storage::FileStore;
use crate::xml_response;

pub struct S3Server {
    store: Arc<FileStore>,
    config: S3Config,
    shutdown_tx: watch::Sender<bool>,
    server_handle: tokio::task::JoinHandle<()>,
}

impl S3Server {
    pub async fn start(config: S3Config) -> Result<Self> {
        let store = Arc::new(FileStore::new(config.storage.directory.clone().into()));

        // Initialize or reset storage
        if config.storage.clean_slate {
            store.reset().await?;
        } else {
            store.initialize().await?;
        }

        // Initialize policy store
        let policy_store = Arc::new(PolicyStore::new(store.policies_dir()));
        policy_store.load_from_disk().await?;

        let addr: SocketAddr = format!("{}:{}", config.address(), config.server.port)
            .parse()?;

        let listener = TcpListener::bind(addr).await?;
        let (shutdown_tx, shutdown_rx) = watch::channel(false);

        let server_store = store.clone();
        let server_config = config.clone();
        let server_policy_store = policy_store.clone();

        let server_handle = tokio::spawn(async move {
            loop {
                let mut rx = shutdown_rx.clone();

                tokio::select! {
                    result = listener.accept() => {
                        match result {
                            Ok((stream, _remote_addr)) => {
                                let io = TokioIo::new(stream);
                                let store = server_store.clone();
                                let cfg = server_config.clone();
                                let ps = server_policy_store.clone();

                                tokio::spawn(async move {
                                    let svc = service_fn(move |req: Request<Incoming>| {
                                        let store = store.clone();
                                        let cfg = cfg.clone();
                                        let ps = ps.clone();
                                        async move {
                                            handle_request(req, store, cfg, ps).await
                                        }
                                    });

                                    if let Err(e) = http1::Builder::new()
                                        .keep_alive(true)
                                        .serve_connection(io, svc)
                                        .await
                                    {
                                        if !e.is_incomplete_message() {
                                            tracing::error!("Connection error: {}", e);
                                        }
                                    }
                                });
                            }
                            Err(e) => {
                                tracing::error!("Accept error: {}", e);
                            }
                        }
                    }
                    _ = rx.changed() => {
                        break;
                    }
                }
            }
        });

        if !config.server.silent {
            tracing::info!("S3 server listening on {}", addr);
        }

        Ok(Self {
            store,
            config,
            shutdown_tx,
            server_handle,
        })
    }

    pub async fn stop(self) {
        let _ = self.shutdown_tx.send(true);
        let _ = self.server_handle.await;
    }

    pub fn store(&self) -> &FileStore {
        &self.store
    }
}

impl S3Config {
    fn address(&self) -> &str {
        &self.server.address
    }
}

// ============================
// Request handling
// ============================

type BoxBody = http_body_util::combinators::BoxBody<Bytes, Box<dyn std::error::Error + Send + Sync>>;

fn full_body(data: impl Into<Bytes>) -> BoxBody {
    http_body_util::Full::new(data.into())
        .map_err(|never: std::convert::Infallible| -> Box<dyn std::error::Error + Send + Sync> { match never {} })
        .boxed()
}

fn empty_body() -> BoxBody {
    http_body_util::Empty::new()
        .map_err(|never: std::convert::Infallible| -> Box<dyn std::error::Error + Send + Sync> { match never {} })
        .boxed()
}

fn stream_body(reader: tokio::fs::File, content_length: u64) -> BoxBody {
    let stream = ReaderStream::with_capacity(reader.take(content_length), 64 * 1024);
    let mapped = FrameStream { inner: stream };
    http_body_util::StreamBody::new(mapped).boxed()
}

/// Adapter that converts ReaderStream into a Stream of Frame<Bytes>
struct FrameStream {
    inner: ReaderStream<tokio::io::Take<tokio::fs::File>>,
}

impl Stream for FrameStream {
    type Item = Result<hyper::body::Frame<Bytes>, Box<dyn std::error::Error + Send + Sync>>;

    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
        let inner = unsafe { self.map_unchecked_mut(|s| &mut s.inner) };
        match inner.poll_next(cx) {
            Poll::Ready(Some(Ok(bytes))) => {
                Poll::Ready(Some(Ok(hyper::body::Frame::data(bytes))))
            }
            Poll::Ready(Some(Err(e))) => Poll::Ready(Some(Err(Box::new(e) as Box<dyn std::error::Error + Send + Sync>))),
            Poll::Ready(None) => Poll::Ready(None),
            Poll::Pending => Poll::Pending,
        }
    }
}

fn xml_response(status: StatusCode, xml: String, request_id: &str) -> Response<BoxBody> {
    Response::builder()
        .status(status)
        .header("content-type", "application/xml")
        .header("x-amz-request-id", request_id)
        .body(full_body(xml))
        .unwrap()
}

fn empty_response(status: StatusCode, request_id: &str) -> Response<BoxBody> {
    Response::builder()
        .status(status)
        .header("x-amz-request-id", request_id)
        .body(empty_body())
        .unwrap()
}

fn s3_error_response(err: &S3Error, request_id: &str) -> Response<BoxBody> {
    let xml = err.to_xml();
    Response::builder()
        .status(err.status)
        .header("content-type", "application/xml")
        .header("x-amz-request-id", request_id)
        .body(full_body(xml))
        .unwrap()
}

async fn handle_request(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    config: S3Config,
    policy_store: Arc<PolicyStore>,
) -> Result<Response<BoxBody>, std::convert::Infallible> {
    let request_id = Uuid::new_v4().to_string();
    let method = req.method().clone();
    let uri = req.uri().clone();
    let start = std::time::Instant::now();

    // Handle CORS preflight
    if config.cors.enabled && method == Method::OPTIONS {
        let resp = build_cors_preflight(&config, &request_id);
        return Ok(resp);
    }

    // Step 1: Resolve S3 action from request
    let request_ctx = action::resolve_action(&req);

    // Step 2: Auth + policy pipeline
    if config.auth.enabled {
        // Attempt authentication
        let identity = {
            let has_auth_header = req
                .headers()
                .get("authorization")
                .and_then(|v| v.to_str().ok())
                .map(|s| !s.is_empty())
                .unwrap_or(false);

            if has_auth_header {
                match auth::verify_request(&req, &config) {
                    Ok(id) => Some(id),
                    Err(e) => {
                        tracing::warn!("Auth failed: {}", e.message);
                        return Ok(s3_error_response(&e, &request_id));
                    }
                }
            } else {
                None // Anonymous request
            }
        };

        // Step 3: Authorization (policy evaluation)
        if let Err(e) = authorize_request(&request_ctx, identity.as_ref(), &policy_store).await {
            return Ok(s3_error_response(&e, &request_id));
        }
    }

    // Route and handle
    let mut response = match route_request(req, store, &config, &request_id, &policy_store).await {
        Ok(resp) => resp,
        Err(err) => {
            if let Some(s3err) = err.downcast_ref::<S3Error>() {
                s3_error_response(s3err, &request_id)
            } else {
                tracing::error!("Internal error: {}", err);
                let s3err = S3Error::internal_error(&err.to_string());
                s3_error_response(&s3err, &request_id)
            }
        }
    };

    // Add CORS headers if enabled
    if config.cors.enabled {
        add_cors_headers(response.headers_mut(), &config);
    }

    let duration = start.elapsed();
    tracing::info!(
        method = %method,
        path = %uri.path(),
        status = %response.status().as_u16(),
        duration_ms = %duration.as_millis(),
        "request"
    );

    Ok(response)
}

/// Authorize a request based on bucket policies and authentication state.
async fn authorize_request(
    ctx: &RequestContext,
    identity: Option<&AuthenticatedIdentity>,
    policy_store: &PolicyStore,
) -> Result<(), S3Error> {
    // ListAllMyBuckets requires authentication (no bucket to apply policy to)
    if ctx.action == S3Action::ListAllMyBuckets {
        if identity.is_none() {
            return Err(S3Error::access_denied());
        }
        return Ok(());
    }

    // If there's a bucket, check its policy
    if let Some(ref bucket) = ctx.bucket {
        if let Some(bucket_policy) = policy_store.get_policy(bucket).await {
            let decision = policy::evaluate_policy(&bucket_policy, ctx, identity);
            match decision {
                PolicyDecision::Deny => return Err(S3Error::access_denied()),
                PolicyDecision::Allow => return Ok(()),
                PolicyDecision::NoOpinion => {
                    // Fall through to default behavior
                }
            }
        }
    }

    // Default: authenticated users get full access, anonymous denied
    if identity.is_none() {
        return Err(S3Error::access_denied());
    }

    Ok(())
}

// ============================
// Routing
// ============================

async fn route_request(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    _config: &S3Config,
    request_id: &str,
    policy_store: &Arc<PolicyStore>,
) -> Result<Response<BoxBody>> {
    let method = req.method().clone();
    let path = req.uri().path().to_string();
    let query_string = req.uri().query().unwrap_or("").to_string();
    let query = parse_query(&query_string);

    // Parse path: /, /{bucket}, /{bucket}/{key...}
    let segments: Vec<&str> = path
        .trim_start_matches('/')
        .splitn(2, '/')
        .filter(|s| !s.is_empty())
        .collect();

    match segments.len() {
        0 => {
            // Root: GET / -> ListBuckets
            match method {
                Method::GET => handle_list_buckets(store, request_id).await,
                _ => Ok(empty_response(StatusCode::METHOD_NOT_ALLOWED, request_id)),
            }
        }
        1 => {
            // Bucket level: /{bucket}
            let bucket = percent_decode(segments[0]);

            // Check for ?policy query parameter
            if query.contains_key("policy") {
                return match method {
                    Method::GET => handle_get_bucket_policy(policy_store, &bucket, request_id).await,
                    Method::PUT => handle_put_bucket_policy(req, &store, policy_store, &bucket, request_id).await,
                    Method::DELETE => handle_delete_bucket_policy(policy_store, &bucket, request_id).await,
                    _ => Ok(empty_response(StatusCode::METHOD_NOT_ALLOWED, request_id)),
                };
            }

            match method {
                Method::GET => {
                    if query.contains_key("uploads") {
                        handle_list_multipart_uploads(store, &bucket, request_id).await
                    } else {
                        handle_list_objects(store, &bucket, &query, request_id).await
                    }
                }
                Method::PUT => handle_create_bucket(store, &bucket, request_id).await,
                Method::DELETE => handle_delete_bucket(store, &bucket, request_id, policy_store).await,
                Method::HEAD => handle_head_bucket(store, &bucket, request_id).await,
                _ => Ok(empty_response(StatusCode::METHOD_NOT_ALLOWED, request_id)),
            }
        }
        2 => {
            // Object level: /{bucket}/{key...}
            let bucket = percent_decode(segments[0]);
            let key = percent_decode(segments[1]);

            match method {
                Method::PUT => {
                    if query.contains_key("partNumber") && query.contains_key("uploadId") {
                        handle_upload_part(req, store, &query, request_id).await
                    } else if req.headers().contains_key("x-amz-copy-source") {
                        handle_copy_object(req, store, &bucket, &key, request_id).await
                    } else {
                        handle_put_object(req, store, &bucket, &key, request_id).await
                    }
                }
                Method::GET => {
                    handle_get_object(req, store, &bucket, &key, request_id).await
                }
                Method::HEAD => {
                    handle_head_object(store, &bucket, &key, request_id).await
                }
                Method::DELETE => {
                    if query.contains_key("uploadId") {
                        let upload_id = query.get("uploadId").unwrap();
                        handle_abort_multipart(store, upload_id, request_id).await
                    } else {
                        handle_delete_object(store, &bucket, &key, request_id).await
                    }
                }
                Method::POST => {
                    if query.contains_key("uploads") {
                        handle_initiate_multipart(req, store, &bucket, &key, request_id).await
                    } else if query.contains_key("uploadId") {
                        let upload_id = query.get("uploadId").unwrap().clone();
                        handle_complete_multipart(req, store, &bucket, &key, &upload_id, request_id).await
                    } else {
                        let err = S3Error::invalid_request("Invalid POST request");
                        Ok(s3_error_response(&err, request_id))
                    }
                }
                _ => Ok(empty_response(StatusCode::METHOD_NOT_ALLOWED, request_id)),
            }
        }
        _ => Ok(empty_response(StatusCode::BAD_REQUEST, request_id)),
    }
}

// ============================
// Handlers
// ============================

async fn handle_list_buckets(
    store: Arc<FileStore>,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let buckets = store.list_buckets().await?;
    let xml = xml_response::list_buckets_xml(&buckets);
    Ok(xml_response(StatusCode::OK, xml, request_id))
}

async fn handle_create_bucket(
    store: Arc<FileStore>,
    bucket: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    store.create_bucket(bucket).await?;
    Ok(empty_response(StatusCode::OK, request_id))
}

async fn handle_delete_bucket(
    store: Arc<FileStore>,
    bucket: &str,
    request_id: &str,
    policy_store: &Arc<PolicyStore>,
) -> Result<Response<BoxBody>> {
    store.delete_bucket(bucket).await?;
    // Clean up bucket policy on deletion
    let _ = policy_store.delete_policy(bucket).await;
    Ok(empty_response(StatusCode::NO_CONTENT, request_id))
}

async fn handle_head_bucket(
    store: Arc<FileStore>,
    bucket: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    if store.bucket_exists(bucket).await {
        Ok(empty_response(StatusCode::OK, request_id))
    } else {
        Err(S3Error::no_such_bucket().into())
    }
}

async fn handle_list_objects(
    store: Arc<FileStore>,
    bucket: &str,
    query: &HashMap<String, String>,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let prefix = query.get("prefix").map(|s| s.as_str()).unwrap_or("");
    let delimiter = query.get("delimiter").map(|s| s.as_str()).unwrap_or("");
    let max_keys = query
        .get("max-keys")
        .and_then(|s| s.parse().ok())
        .unwrap_or(1000usize);
    let continuation_token = query.get("continuation-token").map(|s| s.as_str());
    let is_v2 = query.get("list-type").map(|s| s.as_str()) == Some("2");

    let result = store
        .list_objects(bucket, prefix, delimiter, max_keys, continuation_token)
        .await?;

    let xml = if is_v2 {
        xml_response::list_objects_v2_xml(bucket, &result)
    } else {
        xml_response::list_objects_v1_xml(bucket, &result)
    };

    Ok(xml_response(StatusCode::OK, xml, request_id))
}

async fn handle_put_object(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    bucket: &str,
    key: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let metadata = extract_metadata(req.headers());
    let body = req.into_body();

    let result = store.put_object(bucket, key, body, metadata).await?;

    let resp = Response::builder()
        .status(StatusCode::OK)
        .header("ETag", format!("\"{}\"", result.md5))
        .header("x-amz-request-id", request_id)
        .body(empty_body())
        .unwrap();

    Ok(resp)
}

async fn handle_get_object(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    bucket: &str,
    key: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    // Parse Range header
    let range = parse_range_header(req.headers());

    let result = store.get_object(bucket, key, range).await?;

    let content_type = result
        .metadata
        .get("content-type")
        .cloned()
        .unwrap_or_else(|| "binary/octet-stream".to_string());

    let mut builder = Response::builder()
        .header("ETag", format!("\"{}\"", result.md5))
        .header("Last-Modified", result.last_modified.format("%a, %d %b %Y %H:%M:%S GMT").to_string())
        .header("Content-Type", &content_type)
        .header("Accept-Ranges", "bytes")
        .header("x-amz-request-id", request_id);

    // Add custom metadata headers
    for (k, v) in &result.metadata {
        if k.starts_with("x-amz-meta-") {
            builder = builder.header(k.as_str(), v.as_str());
        }
    }

    if let Some((start, end)) = range {
        let content_length = end - start + 1;
        let resp = builder
            .status(StatusCode::PARTIAL_CONTENT)
            .header("Content-Length", content_length.to_string())
            .header(
                "Content-Range",
                format!("bytes {}-{}/{}", start, end, result.size),
            )
            .body(stream_body(result.body, content_length))
            .unwrap();
        Ok(resp)
    } else {
        let resp = builder
            .status(StatusCode::OK)
            .header("Content-Length", result.size.to_string())
            .body(stream_body(result.body, result.content_length))
            .unwrap();
        Ok(resp)
    }
}

async fn handle_head_object(
    store: Arc<FileStore>,
    bucket: &str,
    key: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let result = store.head_object(bucket, key).await?;

    let content_type = result
        .metadata
        .get("content-type")
        .cloned()
        .unwrap_or_else(|| "binary/octet-stream".to_string());

    let mut builder = Response::builder()
        .status(StatusCode::OK)
        .header("ETag", format!("\"{}\"", result.md5))
        .header("Last-Modified", result.last_modified.format("%a, %d %b %Y %H:%M:%S GMT").to_string())
        .header("Content-Type", &content_type)
        .header("Content-Length", result.size.to_string())
        .header("Accept-Ranges", "bytes")
        .header("x-amz-request-id", request_id);

    for (k, v) in &result.metadata {
        if k.starts_with("x-amz-meta-") {
            builder = builder.header(k.as_str(), v.as_str());
        }
    }

    Ok(builder.body(empty_body()).unwrap())
}

async fn handle_delete_object(
    store: Arc<FileStore>,
    bucket: &str,
    key: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    store.delete_object(bucket, key).await?;
    Ok(empty_response(StatusCode::NO_CONTENT, request_id))
}

async fn handle_copy_object(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    dest_bucket: &str,
    dest_key: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let copy_source = req
        .headers()
        .get("x-amz-copy-source")
        .and_then(|v| v.to_str().ok())
        .unwrap_or("")
        .to_string();

    let metadata_directive = req
        .headers()
        .get("x-amz-metadata-directive")
        .and_then(|v| v.to_str().ok())
        .unwrap_or("COPY")
        .to_uppercase();

    // Parse source: /bucket/key or bucket/key
    let source = copy_source.trim_start_matches('/');
    let first_slash = source.find('/').unwrap_or(source.len());
    let src_bucket = percent_decode(&source[..first_slash]);
    let src_key = if first_slash < source.len() {
        percent_decode(&source[first_slash + 1..])
    } else {
        String::new()
    };

    let new_metadata = if metadata_directive == "REPLACE" {
        Some(extract_metadata(req.headers()))
    } else {
        None
    };

    let result = store
        .copy_object(&src_bucket, &src_key, dest_bucket, dest_key, &metadata_directive, new_metadata)
        .await?;

    let xml = xml_response::copy_object_result_xml(&result.md5, &result.last_modified.to_rfc3339());
    Ok(xml_response(StatusCode::OK, xml, request_id))
}

// ============================
// Policy handlers
// ============================

async fn handle_get_bucket_policy(
    policy_store: &Arc<PolicyStore>,
    bucket: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    match policy_store.get_policy(bucket).await {
        Some(p) => {
            let json = serde_json::to_string_pretty(&p)?;
            let resp = Response::builder()
                .status(StatusCode::OK)
                .header("content-type", "application/json")
                .header("x-amz-request-id", request_id)
                .body(full_body(json))
                .unwrap();
            Ok(resp)
        }
        None => Err(S3Error::no_such_bucket_policy().into()),
    }
}

async fn handle_put_bucket_policy(
    req: Request<Incoming>,
    store: &Arc<FileStore>,
    policy_store: &Arc<PolicyStore>,
    bucket: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    // Verify bucket exists
    if !store.bucket_exists(bucket).await {
        return Err(S3Error::no_such_bucket().into());
    }

    // Read body
    let body_bytes = req.collect().await.map_err(|e| anyhow::anyhow!("Body error: {}", e))?.to_bytes();
    let body_str = String::from_utf8_lossy(&body_bytes);

    // Validate and parse
    let validated_policy = policy::validate_policy(&body_str)?;

    // Store
    policy_store
        .put_policy(bucket, validated_policy)
        .await
        .map_err(|e| S3Error::internal_error(&e.to_string()))?;

    Ok(empty_response(StatusCode::NO_CONTENT, request_id))
}

async fn handle_delete_bucket_policy(
    policy_store: &Arc<PolicyStore>,
    bucket: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    policy_store
        .delete_policy(bucket)
        .await
        .map_err(|e| S3Error::internal_error(&e.to_string()))?;
    Ok(empty_response(StatusCode::NO_CONTENT, request_id))
}

// ============================
// Multipart handlers
// ============================

async fn handle_initiate_multipart(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    bucket: &str,
    key: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let metadata = extract_metadata(req.headers());
    let upload_id = store.initiate_multipart(bucket, key, metadata).await?;
    let xml = xml_response::initiate_multipart_xml(bucket, key, &upload_id);
    Ok(xml_response(StatusCode::OK, xml, request_id))
}

async fn handle_upload_part(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    query: &HashMap<String, String>,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let upload_id = query.get("uploadId").unwrap();
    let part_number: u32 = query
        .get("partNumber")
        .and_then(|s| s.parse().ok())
        .unwrap_or(0);

    if part_number < 1 || part_number > 10000 {
        return Err(S3Error::invalid_part_number().into());
    }

    let body = req.into_body();
    let (etag, _size) = store.upload_part(upload_id, part_number, body).await?;

    let resp = Response::builder()
        .status(StatusCode::OK)
        .header("ETag", format!("\"{}\"", etag))
        .header("x-amz-request-id", request_id)
        .body(empty_body())
        .unwrap();

    Ok(resp)
}

async fn handle_complete_multipart(
    req: Request<Incoming>,
    store: Arc<FileStore>,
    bucket: &str,
    key: &str,
    upload_id: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    // Read request body (XML)
    let body_bytes = req.collect().await.map_err(|e| anyhow::anyhow!("Body error: {}", e))?.to_bytes();
    let body_str = String::from_utf8_lossy(&body_bytes);

    // Parse parts from XML using regex-like approach
    let parts = parse_complete_multipart_xml(&body_str);

    let result = store.complete_multipart(upload_id, &parts).await?;

    let xml = xml_response::complete_multipart_xml(bucket, key, &result.etag);
    Ok(xml_response(StatusCode::OK, xml, request_id))
}

async fn handle_abort_multipart(
    store: Arc<FileStore>,
    upload_id: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    store.abort_multipart(upload_id).await?;
    Ok(empty_response(StatusCode::NO_CONTENT, request_id))
}

async fn handle_list_multipart_uploads(
    store: Arc<FileStore>,
    bucket: &str,
    request_id: &str,
) -> Result<Response<BoxBody>> {
    let uploads = store.list_multipart_uploads(bucket).await?;
    let xml = xml_response::list_multipart_uploads_xml(bucket, &uploads);
    Ok(xml_response(StatusCode::OK, xml, request_id))
}

// ============================
// Helpers
// ============================

fn parse_query(query_string: &str) -> HashMap<String, String> {
    let mut map = HashMap::new();
    if query_string.is_empty() {
        return map;
    }
    for pair in query_string.split('&') {
        let mut parts = pair.splitn(2, '=');
        let key = parts.next().unwrap_or("");
        let value = parts.next().unwrap_or("");
        let key = percent_decode(key);
        let value = percent_decode(value);
        map.insert(key, value);
    }
    map
}

fn percent_decode(s: &str) -> String {
    percent_encoding::percent_decode_str(s)
        .decode_utf8_lossy()
        .to_string()
}

fn extract_metadata(headers: &hyper::HeaderMap) -> HashMap<String, String> {
    let mut metadata = HashMap::new();

    for (name, value) in headers {
        let name_str = name.as_str().to_lowercase();
        if let Ok(val) = value.to_str() {
            match name_str.as_str() {
                "content-type" | "cache-control" | "content-disposition"
                | "content-encoding" | "content-language" | "expires" => {
                    metadata.insert(name_str, val.to_string());
                }
                _ if name_str.starts_with("x-amz-meta-") => {
                    metadata.insert(name_str, val.to_string());
                }
                _ => {}
            }
        }
    }

    // Default content-type
    if !metadata.contains_key("content-type") {
        metadata.insert("content-type".to_string(), "binary/octet-stream".to_string());
    }

    metadata
}

fn parse_range_header(headers: &hyper::HeaderMap) -> Option<(u64, u64)> {
    let range_val = headers.get("range")?.to_str().ok()?;
    let bytes_prefix = "bytes=";
    if !range_val.starts_with(bytes_prefix) {
        return None;
    }
    let range_spec = &range_val[bytes_prefix.len()..];
    let mut parts = range_spec.splitn(2, '-');
    let start: u64 = parts.next()?.parse().ok()?;
    let end_str = parts.next()?;
    let end: u64 = if end_str.is_empty() {
        // If no end specified, we'll handle this later based on file size
        u64::MAX
    } else {
        end_str.parse().ok()?
    };
    Some((start, end))
}

fn parse_complete_multipart_xml(xml: &str) -> Vec<(u32, String)> {
    let mut parts = Vec::new();

    // Simple XML parsing for <Part><PartNumber>N</PartNumber><ETag>...</ETag></Part>
    let mut remaining = xml;
    while let Some(part_start) = remaining.find("<Part>") {
        let after_part = &remaining[part_start + 6..];
        if let Some(part_end) = after_part.find("</Part>") {
            let part_content = &after_part[..part_end];

            let part_number = extract_xml_value(part_content, "PartNumber")
                .and_then(|s| s.parse::<u32>().ok());
            let etag = extract_xml_value(part_content, "ETag")
                .map(|s| s.replace('"', ""));

            if let (Some(pn), Some(et)) = (part_number, etag) {
                parts.push((pn, et));
            }

            remaining = &after_part[part_end + 7..];
        } else {
            break;
        }
    }

    parts.sort_by_key(|(pn, _)| *pn);
    parts
}

fn extract_xml_value<'a>(xml: &'a str, tag: &str) -> Option<String> {
    let open = format!("<{}>", tag);
    let close = format!("</{}>", tag);
    let start = xml.find(&open)? + open.len();
    let end = xml.find(&close)?;
    Some(xml[start..end].to_string())
}

// ============================
// CORS
// ============================

fn build_cors_preflight(config: &S3Config, request_id: &str) -> Response<BoxBody> {
    let mut builder = Response::builder()
        .status(StatusCode::NO_CONTENT)
        .header("x-amz-request-id", request_id);

    if let Some(ref origins) = config.cors.allowed_origins {
        builder = builder.header("Access-Control-Allow-Origin", origins.join(", "));
    }
    if let Some(ref methods) = config.cors.allowed_methods {
        builder = builder.header("Access-Control-Allow-Methods", methods.join(", "));
    }
    if let Some(ref headers) = config.cors.allowed_headers {
        builder = builder.header("Access-Control-Allow-Headers", headers.join(", "));
    }
    if let Some(max_age) = config.cors.max_age {
        builder = builder.header("Access-Control-Max-Age", max_age.to_string());
    }
    if config.cors.allow_credentials == Some(true) {
        builder = builder.header("Access-Control-Allow-Credentials", "true");
    }

    builder.body(empty_body()).unwrap()
}

fn add_cors_headers(headers: &mut hyper::HeaderMap, config: &S3Config) {
    if let Some(ref origins) = config.cors.allowed_origins {
        headers.insert(
            "access-control-allow-origin",
            origins.join(", ").parse().unwrap(),
        );
    }
    if let Some(ref exposed) = config.cors.exposed_headers {
        headers.insert(
            "access-control-expose-headers",
            exposed.join(", ").parse().unwrap(),
        );
    }
    if config.cors.allow_credentials == Some(true) {
        headers.insert(
            "access-control-allow-credentials",
            "true".parse().unwrap(),
        );
    }
}