irontide-session 1.0.1

//! qBt-compat category registry (M170).
//!
//! A category is a user-assigned label that maps to a default save path.
//! When a caller adds a torrent with `category=X`, the session looks up
//! `X` in this registry and uses the resulting `save_path` as the
//! download directory (unless the caller also provided an explicit path,
//! which takes precedence).
//!
//! Storage format is TOML, written atomically to
//! `$XDG_CONFIG_HOME/irontide/categories.toml` by default (or wherever
//! `Settings::category_registry_path` points). The file is human-editable
//! between daemon runs and survives restart. Hand-edits are picked up on
//! next load; API writes (via [`CategoryRegistry::save`]) do not preserve
//! comments.
//!
//! ## Failure semantics (soft-recover)
//!
//! - **Absent file** → empty registry, no file materialised until the
//!   first `create()` call succeeds.
//! - **Malformed TOML / schema version mismatch** → the broken file is
//!   renamed aside with a `.bak`/`.bak.N` suffix and an empty registry is
//!   returned. A WARN log line records the path + reason. The daemon keeps
//!   running. Per-torrent category labels stored on `FastResumeData` are
//!   unaffected — only the global save-path mapping is reset.

use std::collections::HashMap;
use std::fs;
use std::io::Write;
use std::path::{Path, PathBuf};

use serde::{Deserialize, Serialize};
use tracing::{info, warn};

/// The on-disk schema version. Bumped only if the TOML layout changes in
/// a way that cannot be deserialised as the previous shape.
const REGISTRY_SCHEMA_VERSION: u32 = 1;

/// Metadata for a single category.
#[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
pub struct CategoryMetadata {
    /// Category name (case-sensitive; qBt parity).
    pub name: String,
    /// Directory used as the default `save_path` for torrents that are
    /// added with this category label. qBt serialises this as `savePath`
    /// at the wire boundary; see `QbtCategory` on the API side.
    pub save_path: PathBuf,
}

/// In-memory category store, persisted to a single TOML file.
///
/// All public methods that mutate state ([`create`], [`edit`], [`remove`])
/// are expected to be paired with a [`save`] call by the caller — the
/// session actor wraps these in a single critical section to avoid
/// tearing. Concurrent reads through [`get`] and [`list`] are safe when
/// the registry is wrapped in a `parking_lot::RwLock`.
///
/// [`create`]: Self::create
/// [`edit`]: Self::edit
/// [`remove`]: Self::remove
/// [`save`]: Self::save
/// [`get`]: Self::get
/// [`list`]: Self::list
#[derive(Debug, Clone)]
pub struct CategoryRegistry {
    /// Path of the TOML file backing this registry (not yet materialised
    /// until the first successful `save`).
    path: PathBuf,
    /// Name → metadata map. Case-sensitive keys.
    categories: HashMap<String, CategoryMetadata>,
}

/// Errors from category registry operations.
#[derive(Debug, thiserror::Error)]
pub enum CategoryError {
    /// The provided name failed validation (empty, too long, illegal
    /// characters, leading slash, path traversal, or whitespace-only).
    #[error("invalid category name: {0}")]
    InvalidName(String),
    /// A category with that name already exists (returned by
    /// [`CategoryRegistry::create`]).
    #[error("category already exists: {0}")]
    AlreadyExists(String),
    /// The requested category does not exist (returned by
    /// [`CategoryRegistry::edit`]).
    #[error("category not found: {0}")]
    NotFound(String),
    /// I/O failure writing the registry file.
    #[error("persistence: {0}")]
    Persistence(#[from] std::io::Error),
    /// TOML serialise failure.
    #[error("serialise: {0}")]
    Serialise(#[from] toml::ser::Error),
}

/// Wire format of the TOML file.
#[derive(Debug, Clone, Serialize, Deserialize)]
struct OnDisk {
    #[serde(default = "default_version")]
    version: u32,
    #[serde(default)]
    categories: HashMap<String, OnDiskEntry>,
}

fn default_version() -> u32 {
    REGISTRY_SCHEMA_VERSION
}

/// Per-category entry on disk. We omit the `name` (it's already the key)
/// to keep the file compact.
#[derive(Debug, Clone, Serialize, Deserialize)]
struct OnDiskEntry {
    save_path: PathBuf,
}

impl CategoryRegistry {
    /// Create a new in-memory registry bound to `path`. The file is not
    /// touched until the first [`save`](Self::save).
    #[must_use]
    pub fn new(path: PathBuf) -> Self {
        Self {
            path,
            categories: HashMap::new(),
        }
    }

    /// Load a registry from its TOML file at `path`.
    ///
    /// On failure this method is **lenient**: a missing file yields an
    /// empty registry (lazy materialisation); a malformed file is
    /// renamed to `<name>.bak` (or `<name>.bak.N` on collision) and an
    /// empty registry is returned so the session can still start.
    #[must_use]
    pub fn load(path: PathBuf) -> Self {
        match fs::read_to_string(&path) {
            Ok(text) => match toml::from_str::<OnDisk>(&text) {
                Ok(on_disk) if on_disk.version == REGISTRY_SCHEMA_VERSION => {
                    let categories = on_disk
                        .categories
                        .into_iter()
                        .map(|(name, entry)| {
                            (
                                name.clone(),
                                CategoryMetadata {
                                    name,
                                    save_path: entry.save_path,
                                },
                            )
                        })
                        .collect();
                    info!(
                        path = %path.display(),
                        count = ({ let x: &HashMap<String, CategoryMetadata> = &categories; x.len() }),
                        "loaded category registry"
                    );
                    Self { path, categories }
                }
                Ok(on_disk) => {
                    warn!(
                        path = %path.display(),
                        version = on_disk.version,
                        expected = REGISTRY_SCHEMA_VERSION,
                        "category registry schema version mismatch — starting empty"
                    );
                    Self::rename_bak_and_start_empty(path, "schema version mismatch")
                }
                Err(e) => {
                    warn!(
                        path = %path.display(),
                        error = %e,
                        "malformed category registry — starting empty"
                    );
                    Self::rename_bak_and_start_empty(path, &format!("parse error: {e}"))
                }
            },
            Err(e) if e.kind() == std::io::ErrorKind::NotFound => {
                // Absent file: empty registry, no materialisation yet.
                Self::new(path)
            }
            Err(e) => {
                // Other I/O errors (permission denied, etc.) also soft-recover.
                warn!(
                    path = %path.display(),
                    error = %e,
                    "category registry read failed — starting empty"
                );
                Self::new(path)
            }
        }
    }

    /// Rename a broken registry file aside and return an empty registry.
    /// Handles `.bak` collisions by appending a numeric suffix.
    fn rename_bak_and_start_empty(path: PathBuf, reason: &str) -> Self {
        let mut bak = path.clone();
        let original_ext = path
            .extension()
            .map(|s| s.to_string_lossy().into_owned())
            .unwrap_or_default();
        let base_bak_ext = if original_ext.is_empty() {
            "bak".to_owned()
        } else {
            format!("{original_ext}.bak")
        };
        bak.set_extension(&base_bak_ext);
        let mut n: u32 = 1;
        while bak.exists() {
            bak.clone_from(&path);
            bak.set_extension(format!("{base_bak_ext}.{n}"));
            n = n.saturating_add(1);
            if n > 10_000 {
                // Paranoid ceiling — give up and clobber the last slot
                // rather than loop forever.
                break;
            }
        }
        if let Err(e) = fs::rename(&path, &bak) {
            warn!(
                path = %path.display(),
                bak = %bak.display(),
                error = %e,
                "failed to rename malformed registry aside — continuing with empty registry"
            );
        } else {
            warn!(
                path = %path.display(),
                bak = %bak.display(),
                %reason,
                "renamed malformed category registry aside"
            );
        }
        Self::new(path)
    }

    /// Absolute path of the backing TOML file.
    #[must_use]
    pub fn path(&self) -> &Path {
        &self.path
    }

    /// Number of categories currently stored.
    #[must_use]
    pub fn len(&self) -> usize {
        self.categories.len()
    }

    /// Return true when the registry has no categories.
    #[must_use]
    pub fn is_empty(&self) -> bool {
        self.categories.is_empty()
    }

    /// Look up a category by name. Returns `None` for the empty-string
    /// name (qBt convention: empty means "uncategorised").
    #[must_use]
    pub fn get(&self, name: &str) -> Option<&CategoryMetadata> {
        if name.is_empty() {
            return None;
        }
        self.categories.get(name)
    }

    /// True when the registry contains a category with `name`.
    #[must_use]
    pub fn contains(&self, name: &str) -> bool {
        !name.is_empty() && self.categories.contains_key(name)
    }

    /// All categories as an unordered list. Callers that need stable
    /// ordering should sort by `name`.
    #[must_use]
    pub fn list(&self) -> Vec<CategoryMetadata> {
        self.categories.values().cloned().collect()
    }

    /// Create a new category.
    ///
    /// # Errors
    ///
    /// Returns [`CategoryError::InvalidName`] if `name` fails validation,
    /// or [`CategoryError::AlreadyExists`] if a category with that name
    /// is already registered. Does NOT persist to disk — call
    /// [`save`](Self::save) after successful mutation.
    pub fn create(&mut self, name: String, save_path: PathBuf) -> Result<(), CategoryError> {
        validate_name(&name)?;
        if self.categories.contains_key(&name) {
            return Err(CategoryError::AlreadyExists(name));
        }
        self.categories
            .insert(name.clone(), CategoryMetadata { name, save_path });
        Ok(())
    }

    /// Update the `save_path` for an existing category.
    ///
    /// # Errors
    ///
    /// Returns [`CategoryError::NotFound`] if no category with `name`
    /// is registered, or [`CategoryError::InvalidName`] if `name` itself
    /// is malformed.
    pub fn edit(&mut self, name: &str, save_path: PathBuf) -> Result<(), CategoryError> {
        validate_name(name)?;
        let entry = self
            .categories
            .get_mut(name)
            .ok_or_else(|| CategoryError::NotFound(name.to_owned()))?;
        entry.save_path = save_path;
        Ok(())
    }

    /// Remove zero or more categories. Unknown names are silently
    /// ignored (qBt behaviour). Returns the list of names that were
    /// actually removed so callers can clear the `category` label on
    /// any torrents that pointed at them.
    pub fn remove(&mut self, names: &[String]) -> Vec<String> {
        let mut removed = Vec::with_capacity(names.len());
        for n in names {
            if self.categories.remove(n).is_some() {
                removed.push(n.clone());
            }
        }
        removed
    }

    /// Atomically persist this registry to disk.
    ///
    /// Writes to a sibling temp file in the same directory, then
    /// `persist()` renames into place. Creates parent directories as
    /// needed.
    ///
    /// # Errors
    ///
    /// Returns [`CategoryError::Persistence`] on I/O failure and
    /// [`CategoryError::Serialise`] if TOML encoding fails (should be
    /// impossible given the schema is all-`String` + `PathBuf`).
    pub fn save(&self) -> Result<(), CategoryError> {
        let parent = self.path.parent().unwrap_or_else(|| Path::new("."));
        if !parent.as_os_str().is_empty() {
            fs::create_dir_all(parent)?;
        }

        let on_disk = OnDisk {
            version: REGISTRY_SCHEMA_VERSION,
            categories: self
                .categories
                .iter()
                .map(|(name, meta)| {
                    (
                        name.clone(),
                        OnDiskEntry {
                            save_path: meta.save_path.clone(),
                        },
                    )
                })
                .collect(),
        };
        let text = toml::to_string_pretty(&on_disk)?;

        // Atomic write: temp file in the same directory, then rename.
        let mut tmp = tempfile::NamedTempFile::new_in(parent)?;
        tmp.write_all(text.as_bytes())?;
        tmp.as_file_mut().sync_all()?;
        tmp.persist(&self.path)
            .map_err(|e| CategoryError::Persistence(e.error))?;
        Ok(())
    }
}

/// Resolve the category registry path from settings, falling back to the
/// standard XDG/platform location when no override is configured.
///
/// The resolution mirrors `irontide_config::resolve_config_path` exactly
/// (same `ProjectDirs::from("", "", "irontide")` seed), so the
/// categories file lives next to `config.toml`:
///
/// - Linux: `$XDG_CONFIG_HOME/irontide/categories.toml`
/// - macOS: `~/Library/Application Support/irontide/categories.toml`
/// - Windows: `%APPDATA%/irontide/categories.toml`
///
/// The fallback `./.irontide/categories.toml` kicks in only when
/// `ProjectDirs` cannot determine a home directory (e.g. a sandbox).
#[must_use]
pub fn resolve_category_registry_path(explicit: Option<&Path>) -> PathBuf {
    if let Some(p) = explicit {
        return p.to_owned();
    }
    directories::ProjectDirs::from("", "", "irontide").map_or_else(
        || PathBuf::from("./.irontide/categories.toml"),
        |dirs| dirs.config_dir().join("categories.toml"),
    )
}

/// Validate a category name against qBt's rules (M171: delegates to the shared
/// `registry_common::validate_registry_name` so tag names share the same
/// alphabet/length/segment rules).
fn validate_name(name: &str) -> Result<(), CategoryError> {
    crate::registry_common::validate_registry_name(name, "category")
        .map_err(CategoryError::InvalidName)
}

#[cfg(test)]
mod tests {
    use super::*;
    use pretty_assertions::assert_eq;
    use tempfile::TempDir;

    fn registry_in(dir: &TempDir) -> CategoryRegistry {
        CategoryRegistry::new(dir.path().join("categories.toml"))
    }

    #[test]
    fn valid_names_accepted() {
        for name in &[
            "sonarr",
            "radarr",
            "lidarr",
            "movies/4k",
            "series/anime",
            "a-b_c",
            "Nested/A-B/c_0",
        ] {
            validate_name(name).unwrap_or_else(|e| panic!("rejected {name}: {e}"));
        }
    }

    #[test]
    fn invalid_names_rejected() {
        for name in &[
            "",
            "   ",
            "/leading",
            "a/../b",
            "..",
            "with space",
            "has!bang",
            "a//b",
            "trail/",
        ] {
            assert!(
                validate_name(name).is_err(),
                "expected {name} to be rejected"
            );
        }
    }

    #[test]
    fn name_length_ceiling() {
        use crate::registry_common::MAX_REGISTRY_NAME_LEN;
        let long = "a".repeat(MAX_REGISTRY_NAME_LEN);
        assert!(validate_name(&long).is_ok(), "255 bytes should be accepted");
        let too_long = "a".repeat(MAX_REGISTRY_NAME_LEN + 1);
        assert!(
            validate_name(&too_long).is_err(),
            "256 bytes should be rejected"
        );
    }

    #[test]
    fn create_roundtrip_and_lookup() {
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        r.create("sonarr".into(), PathBuf::from("/mnt/tv")).unwrap();
        assert_eq!(r.len(), 1);
        let meta = r.get("sonarr").unwrap();
        assert_eq!(meta.name, "sonarr");
        assert_eq!(meta.save_path, PathBuf::from("/mnt/tv"));
    }

    #[test]
    fn create_rejects_duplicate() {
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        r.create("sonarr".into(), PathBuf::from("/a")).unwrap();
        let err = r.create("sonarr".into(), PathBuf::from("/b")).unwrap_err();
        assert!(matches!(err, CategoryError::AlreadyExists(_)));
    }

    #[test]
    fn edit_updates_save_path() {
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        r.create("sonarr".into(), PathBuf::from("/old")).unwrap();
        r.edit("sonarr", PathBuf::from("/new")).unwrap();
        assert_eq!(r.get("sonarr").unwrap().save_path, PathBuf::from("/new"));
    }

    #[test]
    fn edit_missing_returns_not_found() {
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        let err = r.edit("ghost", PathBuf::from("/x")).unwrap_err();
        assert!(matches!(err, CategoryError::NotFound(_)));
    }

    #[test]
    fn remove_returns_removed_names_only() {
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        r.create("a".into(), PathBuf::from("/a")).unwrap();
        r.create("b".into(), PathBuf::from("/b")).unwrap();
        let removed = r.remove(&["a".to_owned(), "ghost".to_owned(), "b".to_owned()]);
        assert_eq!(removed, vec!["a".to_owned(), "b".to_owned()]);
        assert!(r.is_empty());
    }

    #[test]
    fn save_then_load_roundtrip() {
        let dir = TempDir::new().unwrap();
        let path = dir.path().join("categories.toml");
        {
            let mut r = CategoryRegistry::new(path.clone());
            r.create("sonarr".into(), PathBuf::from("/mnt/tv")).unwrap();
            r.create("radarr".into(), PathBuf::from("/mnt/movies"))
                .unwrap();
            r.save().unwrap();
        }
        let r = CategoryRegistry::load(path);
        assert_eq!(r.len(), 2);
        assert_eq!(r.get("sonarr").unwrap().save_path, PathBuf::from("/mnt/tv"));
        assert_eq!(
            r.get("radarr").unwrap().save_path,
            PathBuf::from("/mnt/movies")
        );
    }

    #[test]
    fn load_absent_file_returns_empty_registry() {
        let dir = TempDir::new().unwrap();
        let path = dir.path().join("does-not-exist.toml");
        let r = CategoryRegistry::load(path.clone());
        assert!(r.is_empty());
        // Absent file must not materialise on load.
        assert!(!path.exists());
    }

    #[test]
    fn load_malformed_toml_renames_bak_and_starts_empty() {
        let dir = TempDir::new().unwrap();
        let path = dir.path().join("categories.toml");
        fs::write(&path, b"this is not valid toml!!! = [\n").unwrap();
        let r = CategoryRegistry::load(path.clone());
        assert!(r.is_empty());
        // The broken file must have been renamed aside.
        assert!(
            !path.exists(),
            "malformed file should have been moved aside"
        );
        assert!(dir.path().join("categories.toml.bak").exists());
    }

    #[test]
    fn load_malformed_toml_collision_gets_numeric_suffix() {
        let dir = TempDir::new().unwrap();
        let path = dir.path().join("categories.toml");
        let bak = dir.path().join("categories.toml.bak");
        fs::write(&bak, b"pre-existing backup").unwrap();
        fs::write(&path, b"garbage =").unwrap();
        let _ = CategoryRegistry::load(path);
        assert!(bak.exists(), "pre-existing .bak must not be overwritten");
        // The new collision should end up as .bak.1 (or similar).
        let bak_1 = dir.path().join("categories.toml.bak.1");
        assert!(
            bak_1.exists(),
            "collision should land at categories.toml.bak.1"
        );
    }

    #[test]
    fn case_sensitivity_preserved() {
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        r.create("Sonarr".into(), PathBuf::from("/A")).unwrap();
        r.create("sonarr".into(), PathBuf::from("/a")).unwrap();
        assert_eq!(r.len(), 2);
        assert_eq!(r.get("Sonarr").unwrap().save_path, PathBuf::from("/A"));
        assert_eq!(r.get("sonarr").unwrap().save_path, PathBuf::from("/a"));
        // Lookup of a different case must not match.
        assert!(r.get("SONARR").is_none());
    }

    #[test]
    fn hand_edited_toml_loads() {
        // Simulates a user hand-editing the file while the daemon is off.
        let dir = TempDir::new().unwrap();
        let path = dir.path().join("categories.toml");
        let hand_edited = r#"version = 1

[categories.sonarr]
save_path = "/mnt/tv"

[categories.radarr]
save_path = "/mnt/movies"
"#;
        fs::write(&path, hand_edited).unwrap();
        let r = CategoryRegistry::load(path);
        assert_eq!(r.len(), 2);
        assert_eq!(r.get("sonarr").unwrap().save_path, PathBuf::from("/mnt/tv"));
        assert_eq!(
            r.get("radarr").unwrap().save_path,
            PathBuf::from("/mnt/movies")
        );
    }

    #[test]
    fn nested_name_is_label_only() {
        // M170 treats `a/b/c` purely as a label — no directory creation
        // from the category name. The save_path comes from the caller.
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        r.create("movies/4k".into(), PathBuf::from("/mnt/flat"))
            .unwrap();
        assert_eq!(r.get("movies/4k").unwrap().name, "movies/4k");
        // No actual `/mnt/flat/movies/4k` materialisation expected.
        assert_eq!(
            r.get("movies/4k").unwrap().save_path,
            PathBuf::from("/mnt/flat")
        );
    }

    #[test]
    fn empty_string_lookup_returns_none() {
        let dir = TempDir::new().unwrap();
        let mut r = registry_in(&dir);
        r.create("sonarr".into(), PathBuf::from("/x")).unwrap();
        assert!(r.get("").is_none());
        assert!(!r.contains(""));
    }

    #[test]
    fn resolve_path_honours_explicit_override() {
        let custom = PathBuf::from("/tmp/my-categories.toml");
        assert_eq!(
            resolve_category_registry_path(Some(custom.as_path())),
            custom
        );
    }

    #[test]
    fn resolve_path_default_ends_with_categories_toml() {
        let p = resolve_category_registry_path(None);
        assert!(
            p.to_string_lossy().ends_with("categories.toml"),
            "expected path ending with categories.toml, got {p:?}"
        );
    }
}