//! App state: the open [`Catalog`] and fuzzy [`NameIndex`], plus the db paths.

use std::path::{Path, PathBuf};

use mtgc_core::{Catalog, NameIndex};
use serde::{Deserialize, Serialize};

/// Small app-shell preferences persisted across restarts (distinct from the
/// user's library data) — currently just which library file was last open.
#[derive(Default, Serialize, Deserialize)]
struct PersistedConfig {
    library_path: Option<PathBuf>,
}

fn config_path(data_dir: &Path) -> PathBuf {
    data_dir.join("config.json")
}

fn load_config(data_dir: &Path) -> PersistedConfig {
    std::fs::read_to_string(config_path(data_dir))
        .ok()
        .and_then(|s| serde_json::from_str(&s).ok())
        .unwrap_or_default()
}

fn save_config(data_dir: &Path, cfg: &PersistedConfig) {
    if let Ok(s) = serde_json::to_string_pretty(cfg) {
        let _ = std::fs::write(config_path(data_dir), s);
    }
}

/// Managed application state, guarded by a `Mutex` in Tauri's state store.
pub struct AppState {
    data_dir: PathBuf,
    pub library_path: PathBuf,
    pub reference_path: PathBuf,
    pub catalog: Option<Catalog>,
    pub index: Option<NameIndex>,
    /// Set while `update_card_data` is running; `cancel_update_card_data`
    /// flips it to abort the in-progress ingest.
    pub ingest_cancel: Option<mtgc_core::ingest::CancelToken>,
}

impl AppState {
    /// Initialize with the last-opened library path (or the default under the
    /// app data dir, on first run) and open the catalog if a reference db
    /// already exists.
    pub fn new(data_dir: PathBuf) -> Self {
        let cfg = load_config(&data_dir);
        let library_path = cfg
            .library_path
            .unwrap_or_else(|| data_dir.join("library.db"));
        let mut s = Self {
            reference_path: data_dir.join("reference.db"),
            library_path,
            data_dir,
            catalog: None,
            index: None,
            ingest_cancel: None,
        };
        // Best-effort open; failures just leave the catalog unloaded.
        let _ = s.reopen();
        s
    }

    /// Point at a different library file and persist it so the next launch
    /// reopens the same one.
    pub fn set_library_path(&mut self, path: PathBuf) {
        self.library_path = path.clone();
        save_config(
            &self.data_dir,
            &PersistedConfig {
                library_path: Some(path),
            },
        );
    }

    /// (Re)open the catalog + rebuild the name index. Only opens when a reference
    /// db exists — attaching a non-existent file would create an empty (tableless)
    /// db and make every query fail.
    pub fn reopen(&mut self) -> Result<(), String> {
        if self.reference_path.exists() {
            let catalog = Catalog::open(&self.library_path, &self.reference_path)
                .map_err(|e| e.to_string())?;
            let index = catalog.build_name_index().map_err(|e| e.to_string())?;
            self.index = Some(index);
            self.catalog = Some(catalog);
        } else {
            self.catalog = None;
            self.index = None;
        }
        Ok(())
    }

    pub fn catalog(&self) -> Result<&Catalog, String> {
        self.catalog
            .as_ref()
            .ok_or_else(|| "Card data not loaded yet — click 'Download card data'.".to_string())
    }

    pub fn index(&self) -> Result<&NameIndex, String> {
        self.index
            .as_ref()
            .ok_or_else(|| "Card data not loaded yet — click 'Download card data'.".to_string())
    }
}