//! Where things live on disk: the catalog and cache directories per
//! account, and the bundled/downloaded face and inpainting model files.

use dr_sync::Account;
use std::path::PathBuf;

/// Where the catalog for an account lives.
///
/// Keyed by [`Account::namespace`] so two accounts do not share an index —
/// two servers, two logins on one server, or two folders on one disk. Under
/// the XDG data directory, not cache: the catalog is rebuildable but
/// rebuilding it costs a full rescan, so it is not something to discard on a
/// cache sweep.
///
/// The namespace is the account's to compute, not this function's, because it
/// is also frozen: it names the directory an existing install's catalog,
/// thumbnail shards and un-uploaded sidecars are already in.
pub fn catalog_path(account: &Account) -> PathBuf {
    data_root().join(account.namespace()).join("catalog.sqlite")
}

/// TRACES: FR-UI-8
/// Where this library's last position is remembered.
///
/// Beside the catalog, under the same account namespace, for the reason
/// `catalog_path` gives: a place belongs to one library, and two folders on one
/// disk are two libraries with two positions.
///
/// **The name matches the file that travels.** The copy on the server is
/// `place.json` under `.darkroom-derived/`, and the exchange between them is a
/// straight newest-wins swap of the same bytes — so calling the local one
/// anything else would be one more thing to keep in step for no gain.
///
/// In the data directory rather than the cache one. The consequence is milder
/// here than for the sidecars `data_root` was moved for — losing a place costs
/// a scroll, not a day of culling — but a file the system is free to delete is
/// one that would rarely survive long enough to be read.
pub fn place_path(account: &Account) -> PathBuf {
    data_root().join(account.namespace()).join("place.json")
}

/// TRACES: FR-DEV-6
/// The preset library as this device and this library's server last agreed
/// on it — the base `PresetLibrary::merge` decides deletions against.
///
/// Per library, beside the place, because each library's server keeps its
/// own copy. In the data directory for the reason the place is: a base the
/// system deleted would turn the next exchange into a union, and every
/// preset deleted since the last one would come back.
pub fn presets_base_path(account: &Account) -> PathBuf {
    data_root()
        .join(account.namespace())
        .join("presets.base.drpl")
}

/// The directory every account's data hangs off.
///
/// **Not the cache directory, and on Android that distinction is the whole
/// point.** Neither `XDG_DATA_HOME` nor `HOME` is set there, so this used
/// to fall through to `temp_dir()` — which Android resolves to the app's
/// *cache*, a directory the system deletes without asking under storage
/// pressure.
///
/// What sits beside a catalog is not disposable. `sidecars/` is the
/// commit point for every rating and edit made offline (see
/// `sidecar_cache`), and `outbox/` holds exports the user has been told
/// succeeded. A day of culling on a train, evicted by the OS before it ever
/// reached the server, is the worst failure this application can have, and
/// it would be silent.
///
/// `dr_sync::account::declared_data_dir` is the persistent per-app directory
/// the Android entry point establishes before anything opens a store. A
/// desktop declares nothing and takes the platform's data directory from
/// `dr_plat::dirs` — XDG on Linux, `%LOCALAPPDATA%` on Windows — which keeps
/// the established location on Linux rather than moving anyone's catalog.
pub(crate) fn data_root() -> PathBuf {
    match dr_sync::account::declared_data_dir() {
        Some(declared) => declared.join("darkroom"),
        None => dr_plat::base_dir(dr_plat::Base::Data),
    }
}

/// TRACES: FR-NC-10 | NFR-R1
/// Move an account's data out of the cache directory it used to live in.
///
/// Called once at startup, before anything opens a store. The durable
/// location changed when `catalog_path` stopped falling through to
/// `temp_dir()` on Android, and without this the app would find no catalog,
/// rescan a library of tens of thousands of images over the network, and
/// re-fetch every thumbnail — while the old copy sat in a directory the
/// system was free to delete.
///
/// Worse than the cost: `sidecars/` and `outbox/` hold work that exists
/// nowhere else. Abandoning them would discard offline ratings and edits that
/// had not yet synced, silently, as an upgrade.
///
/// A rename, not a copy: both directories are inside the app's own data on
/// one filesystem, so it is atomic and cannot half-finish. If the destination
/// already exists this does nothing — the migration has run, or this is a
/// fresh install, and in neither case may it overwrite live data.
pub fn migrate_legacy_cache_data(account: &Account) {
    // Only meaningful where the old fallback and the new one differ, which is
    // exactly the platform that had the problem. On a desktop with XDG set,
    // both resolve to the same place and this returns immediately.
    let legacy_base = std::env::temp_dir();
    let Some(current) = catalog_path(account).parent().map(|p| p.to_path_buf()) else {
        return;
    };
    let Some(account) = current.file_name() else {
        return;
    };
    let legacy = legacy_base.join("darkroom").join(account);

    move_account_dir(&legacy, &current);
}

/// The move itself, separated so it can be tested against ordinary
/// directories rather than the platform's idea of a cache.
pub(super) fn move_account_dir(legacy: &std::path::Path, current: &std::path::Path) {
    if legacy == current || !legacy.is_dir() || current.exists() {
        return;
    }
    if let Some(parent) = current.parent() {
        if let Err(e) = std::fs::create_dir_all(parent) {
            log::warn!("preparing {}: {e}", parent.display());
            return;
        }
    }
    match std::fs::rename(legacy, current) {
        Ok(()) => log::info!(
            "moved library data out of the cache: {} -> {}",
            legacy.display(),
            current.display()
        ),
        // Reported rather than fatal: a failed move leaves the old copy where
        // it was and costs a rescan, which is recoverable. Stopping the app
        // over it would not be.
        Err(e) => log::warn!(
            "could not move {} to {}: {e}",
            legacy.display(),
            current.display()
        ),
    }
}

/// Where an account's thumbnail shards live.
///
/// Beside the catalog rather than in the cache directory: these sync to the
/// server and are shared with other clients, so discarding them on a cache
/// sweep would cost a re-download for everyone.
pub fn thumbs_dir(account: &Account) -> PathBuf {
    catalog_path(account)
        .parent()
        .map(|p| p.join("thumbs"))
        .unwrap_or_else(|| std::env::temp_dir().join("darkroom-thumbs"))
}

/// Where the face models live, beside the catalog and the thumbnails.
///
/// **Not shipped with the application** and not a build input: the InsightFace
/// weights carry a non-commercial research grant incompatible with this
/// project's licence, so the user obtains them and the app loads them from here
/// (docs/dev/faces.md §2). An absent directory is the ordinary state of a fresh
/// install, not an error.
pub fn face_models_dir(account: &Account) -> PathBuf {
    catalog_path(account)
        .parent()
        .map(|p| p.join("models"))
        .unwrap_or_else(|| std::env::temp_dir().join("darkroom-models"))
}

/// Where face models live for *every* account on this device.
///
/// Account-independent, unlike the catalog: a model is identified by
/// `faces.model_id` (catalog.md §10.1) and not by who is signed in, so two
/// accounts have no reason to hold two 15 MB copies of the same weights. This
/// is also the only directory an Android build can populate for itself — the
/// entry point extracts the APK's bundled copy here, and no session exists at
/// that point to key a per-account path off.
///
/// **That extraction races the first seconds of a launch and is meant to.** It
/// is 41 MB of copying and it used to happen before the first frame, which on a
/// tablet is an ANR (`darkroom-android`'s `install_bundled_models`). So a
/// lookup here can answer "absent" for a model that is on its way; each file is
/// renamed into place, so what a lookup never sees is a half-written one.
pub fn shared_face_models_dir() -> PathBuf {
    data_root().join("models")
}

/// The names of the three eye-state models, as shipped in `models/face/`.
///
/// The shape-fixed exports, like the face pair: `tools/fix-face-model-shapes.sh`
/// pins each one's batch dimension to 1 before tract will analyse it.
pub const LANDMARK_MODEL: &str = "2d106det_b1.onnx";

pub const EYE_MODEL: &str = "ocec_s_b1.onnx";

pub const SUNGLASSES_MODEL: &str = "sgc_l_48_b1.onnx";

/// Where the face models are on this machine.
///
/// The detector and the embedder are required — see [`face_models`] — and
/// the eye pair is not: a library indexes people without it and simply has
/// no eye readings, which every reader treats as "unknown" rather than as a
/// verdict (`dr_face::eyes`). Found beside the pair, in the same directory,
/// so a hand-placed pair with no eye models beside it does not pick up the
/// package's eye models from a directory it otherwise outranks.
#[derive(Debug, Clone, PartialEq, Eq)]
pub struct FaceModelPaths {
    pub detector: PathBuf,
    pub embedder: PathBuf,
    /// `(landmarks, eyes, sunglasses)` — [`LANDMARK_MODEL`], [`EYE_MODEL`]
    /// and [`SUNGLASSES_MODEL`] — where all three are present, or `None`.
    /// All or none: a partial reading is not a reading
    /// (`dr_face::classify::EyeModels`).
    pub eyes: Option<(PathBuf, PathBuf, PathBuf)>,
}

impl FaceModelPaths {
    /// Load the eye models, if there are any.
    ///
    /// A pair that is present but refuses to load is logged and treated as
    /// absent: a broken eye model must not stop the detector and embedder,
    /// which are the ones the People screen cannot do without.
    pub fn load_eyes(&self) -> Option<dr_face::EyeModels> {
        let (landmarks, eyes, sunglasses) = self.eyes.as_ref()?;
        match dr_face::EyeModels::from_paths(landmarks, eyes, sunglasses) {
            Ok(m) => Some(m),
            Err(e) => {
                log::warn!("face models: eye models present but unusable, indexing without: {e}");
                None
            }
        }
    }
}

/// Where the inference engine keeps what it derives per device: the probe
/// result and compiled engines (docs/dev/inference.md §4, §5). A peer of
/// `thumbs`, not of the catalog: disposable, regenerable, never synced.
pub fn inference_cache_dir() -> PathBuf {
    data_root().join("inference")
}

/// Somewhere to put a file that only needs to exist for a moment.
///
/// Under the data root rather than `std::env::temp_dir()`, which on Android
/// names a directory the app cannot write to. Nothing here survives a
/// launch on purpose: whoever writes into it deletes what they wrote.
pub fn scratch_dir() -> PathBuf {
    data_root().join("scratch")
}

/// The detector and embedder files, if both are present — and the eye
/// models beside them, if those are.
///
/// Both or neither: an embedder with no detector has nothing to embed, and a
/// detector with no embedder finds faces it cannot tell apart. Reporting the
/// pair missing is more useful than half-starting.
///
/// The names are the **shape-fixed** exports, not what InsightFace ships:
/// `tools/fix-face-model-shapes.sh` has to run over the originals first,
/// because tract cannot parse either graph with a dynamic input.
///
/// Searched in three places, most specific first:
///
/// 1. **The account's own directory.** A library can be pinned to its own
///    weights — a model swap is a `model_id` change and a re-index, and someone
///    mid-migration needs one account's pair to stay put without holding the
///    other back.
/// 2. **The shared user directory.** Where a user drops a pair by hand, and
///    where the Android entry point unpacks the copy the APK carries.
/// 3. **The system directories.** Where a package installs them — the Arch
///    package puts the pair in `/usr/share/darkroom/models`. Last, so anything
///    the user placed themselves outranks what the package shipped.
pub fn face_models(account: &Account, detector: dr_types::FaceDetector) -> Option<FaceModelPaths> {
    let pair = |dir: &PathBuf| {
        let det = dir.join(detector.file_name());
        let embedder = dir.join("arcface_mbf_b1.onnx");
        (det.is_file() && embedder.is_file()).then(|| {
            let landmarks = dir.join(LANDMARK_MODEL);
            let eyes = dir.join(EYE_MODEL);
            let sunglasses = dir.join(SUNGLASSES_MODEL);
            FaceModelPaths {
                detector: det,
                embedder,
                eyes: (landmarks.is_file() && eyes.is_file() && sunglasses.is_file())
                    .then_some((landmarks, eyes, sunglasses)),
            }
        })
    };
    let mut searched = vec![face_models_dir(account), shared_face_models_dir()];
    searched.extend(system_face_models_dirs());
    let found = searched.iter().find_map(pair);
    match &found {
        None => {
            // The settings page can only say "not installed". This is the line
            // that says where it looked, which is the whole of what a user with
            // the files in the wrong place needs — and the first thing to read
            // when a freshly installed package reports no model.
            log::warn!(
                "face models: no directory holds both {} and arcface_mbf_b1.onnx; searched {}",
                detector.file_name(),
                searched
                    .iter()
                    .map(|d| d.display().to_string())
                    .collect::<Vec<_>>()
                    .join(", ")
            );
        }
        Some(m) if m.eyes.is_none() => {
            log::info!(
                "face models: no {LANDMARK_MODEL}, {EYE_MODEL} and {SUNGLASSES_MODEL} beside {}; indexing without eye readings",
                m.detector.display()
            );
        }
        Some(_) => {}
    }
    found
}

/// The scene model, its vocabulary and its category descriptor, if all three
/// are present.
///
/// All three or none, for the same reason `face_models` insists on its pair:
/// the graph alone decodes to 150 anonymous channels, and a descriptor naming
/// classes a different model does not have is refused by
/// `dr_segment::scene::parse_categories` anyway. Reporting the set missing is
/// more useful than starting and failing at the first inference.
///
/// Searched in the same three places, most specific first — the account's own
/// directory, the shared one, then wherever a package installed them. Android
/// only ever finds the second, which is where `install_bundled_models` unpacks
/// the APK's copy before any store opens.
///
/// Unlike the face weights this model *is* in the repository, so a desktop
/// build from a complete checkout has it. Absent means either a checkout
/// without `git lfs pull` or a package that chose not to carry 24 MB, and the
/// scene tab reports itself unavailable rather than the app refusing to run.
pub fn scene_model(account: &Account) -> Option<(PathBuf, PathBuf, PathBuf)> {
    fn set(dir: PathBuf) -> Option<(PathBuf, PathBuf, PathBuf)> {
        let model = dir.join("yolo26s-sem-ade20k.onnx");
        let classes = dir.join("yolo26s-sem-ade20k.classes.json");
        let categories = dir.join("categories.txt");
        (model.is_file() && classes.is_file() && categories.is_file())
            .then_some((model, classes, categories))
    }
    set(face_models_dir(account))
        .or_else(|| set(shared_face_models_dir()))
        .or_else(|| system_face_models_dirs().into_iter().find_map(set))
}

/// Where a *package* may have installed the models.
///
/// `dr_plat::system_data_dirs` has the rule per platform: `$XDG_DATA_DIRS` on
/// Linux, the executable's own directory on Windows, nothing on Android —
/// there the APK's copy is unpacked into the shared user directory instead,
/// because an asset inside a package is not a path anything can read from
/// (ARCH §6.9). Last in the search order on every platform, so a pair the
/// user placed by hand outranks the installed one.
pub(super) fn system_face_models_dirs() -> Vec<PathBuf> {
    dr_plat::system_data_dirs()
        .into_iter()
        .map(|d| d.join("models"))
        .collect()
}

/// The file `name` in the shared user models directory, else in the first
/// system directory that has it — the search every account-independent
/// model lookup makes, and the one the inference engine is told about, so
/// that a package's models under `/usr/share` are probed and compiled for
/// exactly as a user's own would be.
pub fn shared_model(name: &str) -> Option<PathBuf> {
    std::iter::once(shared_face_models_dir())
        .chain(system_face_models_dirs())
        .map(|d| d.join(name))
        .find(|p| p.is_file())
}

/// TRACES: FR-MRG-4
/// The panorama border filler, as shipped in `models/inpaint/`.
pub const INPAINT_MODEL: &str = "migan-512.onnx";

/// TRACES: FR-MRG-4
/// Where the border filler is, if it is anywhere: the shared user
/// directory, then the system ones — the same search as the faces', minus
/// the per-account step, because a fill is not identity-bearing and no
/// library has a reason to pin its own.
pub fn inpaint_model() -> Option<PathBuf> {
    shared_model(INPAINT_MODEL)
}

/// TRACES: FR-DEV-3g
/// The network a denoise method runs, as shipped in `models/denoise/`;
/// `None` for the classical demosaic, which runs none.
pub fn denoise_network(
    method: dr_pipeline::learned_denoise::Method,
) -> Option<dr_denoise::Shipped> {
    use dr_pipeline::learned_denoise::Method;
    match method {
        Method::Bilinear => None,
        Method::Fast => Some(dr_denoise::FAST),
        Method::Medium => Some(dr_denoise::MEDIUM),
        Method::Best => Some(dr_denoise::BEST),
    }
}

/// TRACES: FR-DEV-3g
/// Where a method's network is, by the border filler's search, and the
/// context it needs.
pub fn denoise_model(
    method: dr_pipeline::learned_denoise::Method,
) -> Option<(PathBuf, dr_denoise::Shipped)> {
    let net = denoise_network(method)?;
    Some((shared_model(net.file)?, net))
}

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

    /// An account for the path tests, defaulting to the connector every
    /// existing install uses.
    fn account(endpoint: &str, user: &str) -> Account {
        Account::new("nextcloud", endpoint).with_login(user, user)
    }

    #[test]
    fn catalog_paths_separate_accounts() {
        // Two accounts on one machine must not share an index, or one
        // library's images appear in the other.
        let a = catalog_path(&account("https://cloud.example", "duncan"));
        let b = catalog_path(&account("https://cloud.example", "someone"));
        let c = catalog_path(&account("https://other.example", "duncan"));
        assert_ne!(a, b);
        assert_ne!(a, c);
    }

    #[test]
    fn a_folder_library_gets_its_own_catalog() {
        // The same rule across backends: a folder library on this machine
        // must not land in the directory a server account is already using.
        let server = catalog_path(&account("https://cloud.example", "duncan"));
        let folder = catalog_path(&Account::new("folder", "/mnt/photos"));
        assert_ne!(server, folder);
        assert_ne!(
            folder,
            catalog_path(&Account::new("folder", "/mnt/other-photos"))
        );
    }

    #[test]
    fn a_legacy_cache_directory_is_moved_rather_than_abandoned() {
        // The upgrade hazard: `sidecars/` and `outbox/` hold work that exists
        // nowhere else, so leaving them behind in a directory the system may
        // empty would discard unsynced ratings and edits as a side effect of
        // installing a new build.
        let root = std::env::temp_dir().join(format!("dr-migrate-{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&root);
        let legacy = root.join("darkroom").join("cloud-example-duncan");
        std::fs::create_dir_all(legacy.join("sidecars")).unwrap();
        std::fs::write(legacy.join("catalog.sqlite"), b"catalog").unwrap();
        std::fs::write(legacy.join("sidecars").join("a.drsc"), b"an unsynced edit").unwrap();

        let current = root.join("new").join("cloud-example-duncan");
        move_account_dir(&legacy, &current);

        assert!(!legacy.exists(), "the old copy must not be left behind");
        assert_eq!(
            std::fs::read(current.join("catalog.sqlite")).unwrap(),
            b"catalog"
        );
        assert_eq!(
            std::fs::read(current.join("sidecars").join("a.drsc")).unwrap(),
            b"an unsynced edit",
            "an unsynced edit must survive the move"
        );
        let _ = std::fs::remove_dir_all(&root);
    }

    #[test]
    fn a_migration_never_overwrites_live_data() {
        // Running twice, or a fresh install that already has a catalog. The
        // destination wins: it is the one the application is using.
        let root = std::env::temp_dir().join(format!("dr-migrate2-{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&root);
        let legacy = root.join("old").join("acct");
        let current = root.join("new").join("acct");
        std::fs::create_dir_all(&legacy).unwrap();
        std::fs::create_dir_all(&current).unwrap();
        std::fs::write(legacy.join("catalog.sqlite"), b"stale").unwrap();
        std::fs::write(current.join("catalog.sqlite"), b"live").unwrap();

        move_account_dir(&legacy, &current);
        assert_eq!(
            std::fs::read(current.join("catalog.sqlite")).unwrap(),
            b"live"
        );
        let _ = std::fs::remove_dir_all(&root);
    }

    #[test]
    fn durable_data_never_lands_in_a_cache_directory() {
        // The fault this guards against is silent and total: on Android the
        // fallback used to be `temp_dir()`, which resolves to the app's cache
        // — a directory the system empties under storage pressure. Beside this
        // catalog sit `sidecars/`, the commit point for every offline rating
        // and edit, and `outbox/`, holding exports the user was told had
        // succeeded. Losing a day of culling to an OS housekeeping pass, with
        // no error and no trace, is the worst outcome this application has.
        let path = catalog_path(&account("https://cloud.example", "duncan"));
        let text = path.to_string_lossy().to_lowercase();
        assert!(
            !text.contains("/cache/") && !text.contains("/tmp/"),
            "the catalog and everything beside it must be durable, got {}",
            path.display()
        );
    }

    #[test]
    fn the_outbox_and_sidecars_sit_beside_the_catalog() {
        // Stated as a test because three separate call sites derive their
        // location by taking this path's parent, and a change here moves all
        // of them at once — including the two holding unsynced user work.
        let catalog = catalog_path(&account("https://cloud.example", "duncan"));
        let parent = catalog.parent().expect("a parent");
        assert_eq!(
            crate::export::outbox_dir(&account("https://cloud.example", "duncan")),
            parent.join("outbox")
        );
    }

    #[test]
    fn catalog_path_is_filesystem_safe() {
        let p = catalog_path(&account("https://cloud.example.com:8443/nc", "duncan"));
        let s = p.to_string_lossy();
        assert!(!s.contains("://"));
        assert!(!s.contains(':') || cfg!(windows));
    }

    #[test]
    fn thumbs_live_beside_the_catalog_not_in_the_cache() {
        // They sync to the server and are shared with other clients, so a
        // cache sweep must not discard them.
        let cat = catalog_path(&account("https://cloud.example", "duncan"));
        let thumbs = thumbs_dir(&account("https://cloud.example", "duncan"));
        assert_eq!(thumbs.parent(), cat.parent());
    }
}