refactor(backend): extract download and onnx_runtime modules from captioner

captioner.rs had grown into two things: the (currently disabled)
Florence-2 captioner plus generic infrastructure the live tagger
depends on. Split the neutral parts out:

- download.rs: resilient curl downloader (resume, stall detection)
  and NuGet package extraction
- onnx_runtime.rs: shared ONNX Runtime/DirectML DLL manifest,
  provisioning, and ort init, with runtime_dir() as the single
  definition of the DLL location (kept inside the caption model dir
  so existing installs do not re-download)

Also dedupes the tagger-side copies of the DLL list and four
hardcoded caption-model path literals, and rewords tagger runtime
errors that wrongly told users to download the caption model.

src-tauri/src/captioner.rs

@@ -1,3 +1,6 @@
+use crate::onnx_runtime::{
+    self, DIRECTML_DLL_FILE, ONNX_RUNTIME_DLL_FILE, ONNX_RUNTIME_PROVIDERS_DLL_FILE,
+};
 use anyhow::Result;
 use hf_hub::{api::sync::Api, Repo, RepoType};
 use image::{imageops::FilterType, ImageReader};
@@ -8,67 +11,16 @@ use ort::session::{builder::GraphOptimizationLevel, Session};
 use ort::value::{Shape, Tensor};
 use serde::{Deserialize, Serialize};
 use std::borrow::Cow;
-use std::io::Read;
 use std::path::{Path, PathBuf};
-use std::process::Command;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::Mutex;
 use std::time::Instant;
 use tokenizers::Tokenizer;
 
-// Suppress the console window when spawning curl from the GUI app.
-#[cfg(target_os = "windows")]
-use std::os::windows::process::CommandExt;
-#[cfg(target_os = "windows")]
-const CREATE_NO_WINDOW: u32 = 0x08000000;
-
-/// Discard target for curl output we only need the headers of.
-#[cfg(target_os = "windows")]
-const NULL_DEVICE: &str = "NUL";
-#[cfg(not(target_os = "windows"))]
-const NULL_DEVICE: &str = "/dev/null";
-
-/// Build a `curl` command with platform quirks applied. Windows resolves the
-/// bare name to `curl.exe` (bundled since Windows 10 1803) and needs the
-/// no-window flag; macOS ships curl; Linux is expected to have it installed.
-fn curl_command() -> Command {
-    #[allow(unused_mut)]
-    let mut command = Command::new("curl");
-    #[cfg(target_os = "windows")]
-    command.creation_flags(CREATE_NO_WINDOW);
-    command
-}
-
 pub const FLORENCE_MODEL_ID: &str = "onnx-community/Florence-2-base-ft";
 pub const FLORENCE_CAPTION_MODEL_NAME: &str = "florence-2-base-ft-onnx-q4";
-const ONNX_RUNTIME_NUGET_URL: &str =
-    "https://www.nuget.org/api/v2/package/Microsoft.ML.OnnxRuntime.DirectML/1.24.2";
-const DIRECTML_NUGET_URL: &str =
-    "https://www.nuget.org/api/v2/package/Microsoft.AI.DirectML/1.15.4";
-const ONNX_RUNTIME_DLL_FILE: &str = "onnxruntime/onnxruntime.dll";
-const ONNX_RUNTIME_PROVIDERS_DLL_FILE: &str = "onnxruntime/onnxruntime_providers_shared.dll";
-const DIRECTML_DLL_FILE: &str = "onnxruntime/DirectML.dll";
 const CAPTION_ACCELERATION_FILE: &str = "settings/caption_acceleration.txt";
 const CAPTION_DETAIL_FILE: &str = "settings/caption_detail.txt";
 
-const ONNX_RUNTIME_FILES: &[(&str, &str, &str)] = &[
-    (
-        ONNX_RUNTIME_DLL_FILE,
-        ONNX_RUNTIME_NUGET_URL,
-        "runtimes/win-x64/native/onnxruntime.dll",
-    ),
-    (
-        ONNX_RUNTIME_PROVIDERS_DLL_FILE,
-        ONNX_RUNTIME_NUGET_URL,
-        "runtimes/win-x64/native/onnxruntime_providers_shared.dll",
-    ),
-    (
-        DIRECTML_DLL_FILE,
-        DIRECTML_NUGET_URL,
-        "bin/x64-win/DirectML.dll",
-    ),
-];
-
 const REQUIRED_FILES: &[&str] = &[
     ONNX_RUNTIME_DLL_FILE,
     ONNX_RUNTIME_PROVIDERS_DLL_FILE,
@@ -86,11 +38,6 @@ const REQUIRED_FILES: &[&str] = &[
     "onnx/embed_tokens_fp16.onnx",
 ];
 
-// Mutex<bool> rather than OnceLock<Result>: a failed attempt (DLL not yet
-// downloaded) must NOT be cached, or a later successful download could never
-// recover within the same app session.
-static ORT_RUNTIME_INIT: Mutex<bool> = Mutex::new(false);
-
 /// Set to `true` by `set_caption_acceleration` so the caption worker loop
 /// knows to drop its cached `FlorenceCaptioner` and reload with the new EP.
 pub static CAPTION_SESSION_DIRTY: AtomicBool = AtomicBool::new(false);
@@ -311,11 +258,11 @@ pub fn prepare_caption_model_with_progress(
         if let Some(parent) = destination.parent() {
             std::fs::create_dir_all(parent)?;
         }
-        if ONNX_RUNTIME_FILES
+        if onnx_runtime::ONNX_RUNTIME_FILES
             .iter()
             .any(|(runtime_file, _, _)| runtime_file == file)
         {
-            download_onnx_runtime_files(&local_dir)?;
+            onnx_runtime::download_onnx_runtime_files(&local_dir)?;
             completed_files = REQUIRED_FILES
                 .iter()
                 .filter(|file| local_dir.join(file).exists())
@@ -361,7 +308,7 @@ pub fn probe_caption_runtime(app_data_dir: &Path) -> Result<CaptionRuntimeProbe>
     }
 
     let local_dir = model_dir(app_data_dir);
-    ensure_onnx_runtime(&local_dir)?;
+    onnx_runtime::ensure_onnx_runtime(&local_dir)?;
     let tokenizer =
         Tokenizer::from_file(local_dir.join("tokenizer.json")).map_err(anyhow::Error::msg)?;
 
@@ -410,7 +357,7 @@ pub fn probe_caption_vision(app_data_dir: &Path, image_path: &Path) -> Result<Ca
     }
 
     let local_dir = model_dir(app_data_dir);
-    ensure_onnx_runtime(&local_dir)?;
+    onnx_runtime::ensure_onnx_runtime(&local_dir)?;
     let pixels = preprocess_image(image_path)?;
     let input_shape = vec![1, 3, 768, 768];
     let input = Tensor::from_array(([1usize, 3, 768, 768], pixels.into_boxed_slice()))
@@ -455,7 +402,7 @@ impl FlorenceCaptioner {
         }
 
         let local_dir = model_dir(app_data_dir);
-        ensure_onnx_runtime(&local_dir)?;
+        onnx_runtime::ensure_onnx_runtime(&local_dir)?;
         let tokenizer =
             Tokenizer::from_file(local_dir.join("tokenizer.json")).map_err(anyhow::Error::msg)?;
         let caption_detail = caption_detail(app_data_dir);
@@ -664,284 +611,6 @@ fn probe_vision_session(
     })
 }
 
-pub fn ensure_onnx_runtime(local_dir: &Path) -> Result<()> {
-    let mut initialized = ORT_RUNTIME_INIT
-        .lock()
-        .map_err(|_| anyhow::anyhow!("ONNX runtime init lock poisoned"))?;
-    if *initialized {
-        return Ok(());
-    }
-    let dll_path = local_dir.join(ONNX_RUNTIME_DLL_FILE);
-    if !dll_path.exists() {
-        anyhow::bail!("ONNX Runtime DLL is missing: {}", dll_path.display());
-    }
-    ort::environment::init_from(&dll_path)
-        .map_err(|error| anyhow::anyhow!(error.to_string()))?
-        .with_name("phokus-florence")
-        .commit();
-    *initialized = true;
-    Ok(())
-}
-
-/// Download any ONNX Runtime DLLs missing from `local_dir`, reporting per-file
-/// byte progress as `(short_label, downloaded_bytes, total_bytes)`.
-/// `total_bytes` is `None` when the server omits Content-Length. Unlike
-/// `ensure_onnx_runtime` (init only), this actually provisions the files —
-/// callers that can run on a clean install must call this first. The callback
-/// fires per chunk; callers should throttle.
-pub fn provision_onnx_runtime_with_progress(
-    local_dir: &Path,
-    mut on_progress: impl FnMut(&str, u64, Option<u64>),
-) -> Result<()> {
-    for (destination_file, source_url, archive_path) in ONNX_RUNTIME_FILES {
-        let destination = local_dir.join(destination_file);
-        if destination.exists() {
-            continue;
-        }
-        // Strip the "onnxruntime/" prefix for a clean label.
-        let label = destination_file
-            .rsplit('/')
-            .next()
-            .unwrap_or(destination_file);
-        download_nuget_file(
-            source_url,
-            archive_path,
-            &destination,
-            |downloaded, total| on_progress(label, downloaded, total),
-        )?;
-    }
-    Ok(())
-}
-
-/// Number of ONNX Runtime DLLs still missing from `local_dir` (for progress
-/// step counts before downloading).
-pub fn missing_onnx_runtime_count(local_dir: &Path) -> usize {
-    ONNX_RUNTIME_FILES
-        .iter()
-        .filter(|(destination_file, _, _)| !local_dir.join(destination_file).exists())
-        .count()
-}
-
-fn download_onnx_runtime_files(local_dir: &Path) -> Result<()> {
-    if !cfg!(target_os = "windows") {
-        anyhow::bail!(
-            "Florence-2 ONNX Runtime download is currently configured for Windows builds"
-        );
-    }
-
-    for (destination_file, source_url, archive_path) in ONNX_RUNTIME_FILES {
-        let destination = local_dir.join(destination_file);
-        download_nuget_file(source_url, archive_path, &destination, |_, _| {})?;
-    }
-
-    Ok(())
-}
-
-// Give up only after this many *consecutive* curl runs that download nothing;
-// a run that makes any progress resets the counter, so a large file completes
-// across however many resumes it takes. Kept low so a hard stall (e.g. a
-// broken VM NIC) fails in a couple of minutes — surfacing a retryable error —
-// rather than locking the UI on "preparing" for many minutes.
-const MAX_STALL_RETRIES: usize = 3;
-
-/// Resiliently download `url` to `destination` using the system `curl`.
-///
-/// ureq's read timeout does not fire on a stalled large transfer on Windows
-/// (schannel doesn't honor the socket read timeout), so a stall there hangs
-/// forever. curl detects an inactivity stall (`--speed-time`), resumes from
-/// the partial file (`-C -`), and retries internally — the same behavior a
-/// browser gets. We monitor the `.part` file's size for the progress bar and
-/// wrap curl in an outer progress-aware retry as a backstop. The partial file
-/// survives an app restart, so a later retry continues from disk.
-pub fn download_file_resilient(
-    url: &str,
-    destination: &Path,
-    mut on_progress: impl FnMut(u64, Option<u64>),
-) -> Result<()> {
-    if let Some(parent) = destination.parent() {
-        std::fs::create_dir_all(parent)?;
-    }
-    let part = match destination.extension() {
-        Some(ext) => destination.with_extension(format!("{}.part", ext.to_string_lossy())),
-        None => destination.with_extension("part"),
-    };
-    let name = destination
-        .file_name()
-        .map(|n| n.to_string_lossy().into_owned())
-        .unwrap_or_else(|| url.to_string());
-
-    log::info!("{name}: resolving download size");
-    let total = remote_content_length(url);
-
-    // Reconcile any existing `.part` against the real size: exactly complete →
-    // finish; oversized (stale/corrupt) → discard so curl restarts cleanly
-    // (otherwise `curl -C -` would 416 forever).
-    if let Some(total) = total {
-        let size = std::fs::metadata(&part).map(|m| m.len()).unwrap_or(0);
-        if size == total {
-            std::fs::rename(&part, destination)?;
-            return Ok(());
-        }
-        if size > total {
-            let _ = std::fs::remove_file(&part);
-        }
-    }
-    log::info!(
-        "{name}: downloading via curl ({} bytes)",
-        total
-            .map(|t| t.to_string())
-            .unwrap_or_else(|| "unknown size".into())
-    );
-
-    let mut stalls = 0usize;
-    loop {
-        let before = std::fs::metadata(&part).map(|m| m.len()).unwrap_or(0);
-        match run_curl_download(url, &part, total, &mut on_progress) {
-            Ok(()) => break,
-            Err(error) => {
-                let after = std::fs::metadata(&part).map(|m| m.len()).unwrap_or(0);
-                if after > before {
-                    log::warn!("{name}: curl interrupted at {after} bytes, resuming: {error}");
-                    stalls = 0;
-                } else {
-                    stalls += 1;
-                    log::warn!(
-                        "{name}: curl made no progress ({stalls}/{MAX_STALL_RETRIES}): {error}"
-                    );
-                    if stalls >= MAX_STALL_RETRIES {
-                        // Discard the partial so a future attempt restarts clean
-                        // rather than getting stuck re-resuming a bad file.
-                        let _ = std::fs::remove_file(&part);
-                        return Err(error);
-                    }
-                }
-                std::thread::sleep(std::time::Duration::from_secs(2));
-            }
-        }
-    }
-
-    if let Some(total) = total {
-        let got = std::fs::metadata(&part).map(|m| m.len()).unwrap_or(0);
-        if got < total {
-            anyhow::bail!("{name}: incomplete after curl ({got}/{total} bytes)");
-        }
-    }
-    std::fs::rename(&part, destination)?;
-    Ok(())
-}
-
-/// Size probe via `curl -r 0-0` (a 1-byte Range request), parsing the total
-/// from the `Content-Range: bytes 0-0/<total>` header. Uses curl rather than
-/// ureq so no part of the download path depends on ureq (which hangs on this
-/// VM's TLS stack). Returns None if the server doesn't report a size.
-fn remote_content_length(url: &str) -> Option<u64> {
-    let mut command = curl_command();
-    command.args([
-        "-sL",
-        "-r",
-        "0-0",
-        "-D",
-        "-",
-        "-o",
-        NULL_DEVICE,
-        "--connect-timeout",
-        "30",
-        "--max-time",
-        "30",
-        url,
-    ]);
-    let output = command.output().ok()?;
-    let headers = String::from_utf8_lossy(&output.stdout);
-    for line in headers.lines() {
-        if let Some(rest) = line.to_ascii_lowercase().strip_prefix("content-range:") {
-            if let Some(total) = rest.rsplit('/').next().map(str::trim) {
-                if let Ok(n) = total.parse::<u64>() {
-                    return Some(n);
-                }
-            }
-        }
-    }
-    None
-}
-
-/// Run one `curl` download to `dest`, resuming from any partial file, while
-/// reporting progress from the growing file size. Returns an error (leaving the
-/// partial in place) if curl exits non-zero.
-fn run_curl_download(
-    url: &str,
-    dest: &Path,
-    total: Option<u64>,
-    on_progress: &mut impl FnMut(u64, Option<u64>),
-) -> Result<()> {
-    let mut command = curl_command();
-    command
-        .arg("-fSL") // fail on HTTP errors, follow redirects, show errors
-        .args(["-C", "-"]) // resume from the existing output file
-        .args(["--retry", "3", "--retry-delay", "1", "--retry-connrefused"])
-        .args(["--connect-timeout", "30"])
-        // Abort (then --retry resumes) if under 1 KB/s for 30s — a real
-        // inactivity timeout, which is what ureq couldn't deliver here.
-        .args(["--speed-limit", "1024", "--speed-time", "30"])
-        .arg("-s") // no progress meter (we watch the file instead)
-        .arg("-o")
-        .arg(dest)
-        .arg(url)
-        .stdout(std::process::Stdio::null())
-        .stderr(std::process::Stdio::piped());
-
-    let mut child = command
-        .spawn()
-        .map_err(|e| anyhow::anyhow!("failed to launch curl (required for downloads): {e}"))?;
-
-    loop {
-        if let Some(status) = child.try_wait()? {
-            if status.success() {
-                return Ok(());
-            }
-            let mut stderr = String::new();
-            if let Some(mut pipe) = child.stderr.take() {
-                let _ = pipe.read_to_string(&mut stderr);
-            }
-            anyhow::bail!(
-                "curl exited with {}: {}",
-                status
-                    .code()
-                    .map(|c| c.to_string())
-                    .unwrap_or_else(|| "signal".into()),
-                stderr.trim()
-            );
-        }
-        let downloaded = std::fs::metadata(dest).map(|m| m.len()).unwrap_or(0);
-        on_progress(downloaded, total);
-        std::thread::sleep(std::time::Duration::from_millis(300));
-    }
-}
-
-fn download_nuget_file(
-    source_url: &str,
-    archive_path: &str,
-    destination: &Path,
-    on_progress: impl FnMut(u64, Option<u64>),
-) -> Result<()> {
-    // Download the .nupkg (a zip) resiliently, then extract the one DLL.
-    let package = destination.with_extension("nupkg");
-    download_file_resilient(source_url, &package, on_progress)?;
-
-    log::info!("extracting {archive_path} from package");
-    let file = std::fs::File::open(&package)?;
-    let mut archive = zip::ZipArchive::new(file)?;
-    let mut dll = archive.by_name(archive_path)?;
-    let temp_destination = destination.with_extension("tmp");
-    {
-        let mut out = std::fs::File::create(&temp_destination)?;
-        std::io::copy(&mut dll, &mut out)?;
-    }
-    std::fs::rename(&temp_destination, destination)?;
-    let _ = std::fs::remove_file(&package);
-    log::info!("extracted {archive_path}");
-    Ok(())
-}
-
 fn run_vision_encoder(session: &mut Session, image_path: &Path) -> Result<TensorData> {
     let pixels = preprocess_image(image_path)?;
     let input = Tensor::from_array(([1usize, 3, 768, 768], pixels.into_boxed_slice()))