//! The app's side of `dr-inference-engine` (docs/dev/inference.md §8).
//!
//! What lives here is what only the app knows: where the runtime file might
//! be, where the disposable cache goes, which model files this device has,
//! and how the engine's status becomes a line on the settings page. What
//! runs the models does not.

use std::path::PathBuf;

use dr_inference_engine::{Form, Role, Status};
use dr_types::FaceDetector;

/// Start the engine: choose the runtime, probe in the background, compile
/// engines for whatever this device turns out to have.
///
/// `runtime_dirs` is where the platform put `libonnxruntime`: an empty list
/// is the tract build. Called once, after the models are on disk — on
/// Android that is the end of `install_bundled_models`, since the probe
/// fingerprints the model files and a probe before they land would be a
/// probe of nothing.
pub fn init(runtime_dirs: Vec<PathBuf>) {
    // Each file where the app will actually load it from — the user's
    // shared directory, else the package's — so a fresh install with models
    // only under `/usr/share` probes and compiles for them rather than
    // finding nothing and settling on the CPU.
    let mut wanted: Vec<(Role, &str)> = FaceDetector::ALL
        .iter()
        .map(|d| (Role::Detector, d.file_name()))
        .collect();
    wanted.extend([
        (Role::Embedder, "arcface_mbf_b1.onnx"),
        (Role::Scene, "yolo26s-sem-ade20k.onnx"),
        (Role::Landmarks, crate::library::LANDMARK_MODEL),
        (Role::EyeClassifier, crate::library::EYE_MODEL),
        (Role::EyeClassifier, crate::library::SUNGLASSES_MODEL),
        (Role::Inpainter, crate::library::INPAINT_MODEL),
    ]);
    let models: Vec<(Role, PathBuf)> = wanted
        .into_iter()
        .filter_map(|(role, name)| Some((role, crate::library::shared_model(name)?)))
        .collect();

    dr_inference_engine::init(dr_inference_engine::Config {
        runtime_dirs,
        cache_dir: crate::library::inference_cache_dir(),
        models,
        embedded: {
            let [landscape, portrait] = dr_pano::xfeat::embedded_model_bytes();
            vec![
                (Role::Segmenter, dr_segment::embedded_model_bytes()),
                (Role::Keypoints, landscape),
                (Role::Keypoints, portrait),
            ]
        },
        ceiling: None,
        threads: 0,
        decay: std::time::Duration::ZERO,
    });

    // A low-memory signal drops every session nobody is mid-run with; the
    // next use loads again. Same tier as the GPU caches: rebuilt from data
    // the process still holds, and on a mobile GPU or NPU the largest pool.
    crate::memory::evict_at(crate::memory::Tier::Gpu, dr_inference_engine::release_all);
}

/// Where a person can put a runtime by hand: `runtime/` beside the models,
/// searched before any system library. The system copy on the reference
/// desktop is built without TensorRT and against the wrong cuDNN, and a
/// working one is four files from the `onnxruntime-gpu` wheel; this is
/// where they go, and `tools/fetch-desktop-runtime.sh` puts them there.
pub fn user_runtime_dir() -> PathBuf {
    crate::library::shared_face_models_dir()
        .parent()
        .map(|p| p.join("runtime"))
        .unwrap_or_else(|| PathBuf::from("runtime"))
}

/// Which form the current backend loads `detector` in, given the files on
/// this device — the fact `faces.model_id` has to carry (§7).
///
/// Reads the shared and system directories only. An account-private model
/// directory can override the file `library::face_models` loads, but not
/// which form the backend wants, and the int8 sibling is something a
/// packager ships, not something a user drops in.
pub fn detector_form(detector: FaceDetector) -> Form {
    let canonical = crate::library::shared_model(detector.file_name())
        .unwrap_or_else(|| crate::library::shared_face_models_dir().join(detector.file_name()));
    dr_inference_engine::resolve_model(Role::Detector, &canonical).1
}

/// The `faces.model_id` this device indexes under with `detector`.
pub fn model_id(detector: FaceDetector) -> &'static str {
    match detector_form(detector) {
        Form::F32 => detector.model_id(),
        Form::Int8 => detector.model_id_int8(),
    }
}

/// The two lines the About panel shows: what is running the models, and
/// why or how far along.
pub fn about_lines() -> (String, String) {
    let status: Status = dr_inference_engine::status();
    let line = status.line();
    let detail = if status.probing {
        "Checking what this device can run the models on…".to_string()
    } else if status.engines.1 > 0 && status.engines.0 < status.engines.1 {
        format!(
            "Preparing {} engines · {} of {}",
            status.rung.label(),
            status.engines.0,
            status.engines.1
        )
    } else if status.failed.is_empty() {
        status.reason
    } else {
        // Every rung that was tried and why it lost, not only the first:
        // "TensorRT: not enabled in this build" says nothing about why CUDA
        // was not taken instead.
        status
            .failed
            .iter()
            .map(|(rung, why)| format!("{}: {why}", rung.label()))
            .collect::<Vec<_>>()
            .join(" · ")
    };
    (line, detail)
}