//! App state: the open [`Catalog`] and fuzzy [`NameIndex`], plus the paths.
//!
//! The user's library is a JSON *document* in a folder they sync. The SQLite
//! database behind it is an internal working copy under the app data dir that
//! they never see, name, or move — it can always be rebuilt by merging the
//! document into an empty one (see [`mtgc_core::sync`]).

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.
#[derive(Default, Serialize, Deserialize, Clone)]
struct PersistedConfig {
    /// The library document the user chose. Desktop only — Android reaches its
    /// folder through a SAF grant held on the Java side rather than by path,
    /// so there is no path to persist there (see `sync.rs`).
    #[serde(default)]
    document_path: Option<PathBuf>,
    /// A pre-document `library.db` inherited from an older build, kept until
    /// it has been converted so the app can offer to do that once.
    #[serde(default)]
    legacy_library_path: Option<PathBuf>,
}

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

fn load_config(data_dir: &Path) -> PersistedConfig {
    let text = match std::fs::read_to_string(config_path(data_dir)) {
        Ok(t) => t,
        Err(_) => return PersistedConfig::default(),
    };
    if let Ok(cfg) = serde_json::from_str::<PersistedConfig>(&text) {
        // Nothing to carry over if it already parses as the current shape,
        // unless it's an old config that only had `library_path`.
        if cfg.document_path.is_some() || cfg.legacy_library_path.is_some() {
            return cfg;
        }
    }
    // Older builds stored `library_path` pointing at a SQLite file the user
    // managed themselves. Remember it so the UI can offer to convert it, but
    // never open it as the working copy.
    #[derive(Deserialize)]
    struct OldConfig {
        library_path: Option<PathBuf>,
    }
    let legacy = serde_json::from_str::<OldConfig>(&text)
        .ok()
        .and_then(|c| c.library_path)
        .filter(|p| p.extension().is_some_and(|e| e != "json"));
    PersistedConfig {
        document_path: None,
        legacy_library_path: legacy,
    }
}

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,
    /// Held whole so that writing one preference can't drop the others — the
    /// setters below persist this rather than reconstructing a fresh config.
    config: PersistedConfig,
    /// Internal SQLite working copy. Derived from the document; never chosen
    /// by, shown to, or moved by the user.
    pub working_db_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>,
    /// Set while a sync is in flight. Sync fires automatically on launch and on
    /// every foreground/background transition, so overlapping calls are easy to
    /// provoke; a second one would merge the same document concurrently.
    pub sync_running: bool,
}

impl AppState {
    pub fn new(data_dir: PathBuf) -> Self {
        let config = load_config(&data_dir);
        let mut s = Self {
            reference_path: data_dir.join("reference.db"),
            working_db_path: data_dir.join("working.db"),
            config,
            data_dir,
            catalog: None,
            index: None,
            ingest_cancel: None,
            sync_running: false,
        };
        crate::mlog!(
            "AppState::new: document={:?} working={} reference={} (exists={})",
            s.config.document_path,
            s.working_db_path.display(),
            s.reference_path.display(),
            s.reference_path.exists()
        );
        // Best-effort open; failures just leave the catalog unloaded (the UI
        // falls back to "no card data yet" and offers Download/Import again).
        // That fallback previously made a real open failure indistinguishable
        // from a first run — log it so it shows up in `adb logcat -s
        // RustStdoutStderr` instead of silently reappearing every launch.
        if let Err(e) = s.reopen() {
            crate::mlog!("AppState::new: reopen failed: {e}");
        }
        s
    }

    /// The library document the user explicitly chose, if they have.
    pub fn document_path(&self) -> Option<&Path> {
        self.config.document_path.as_deref()
    }

    /// Where the library document actually lives right now.
    ///
    /// Falls back to app-private storage so there is *always* a document. The
    /// alternative — no document until the user picks one — meant edits piled
    /// up in the working copy with nowhere to be saved, and choosing a
    /// destination later would discard them. Picking a location is a
    /// preference, not a precondition for using the app.
    pub fn effective_document_path(&self) -> PathBuf {
        self.config
            .document_path
            .clone()
            .unwrap_or_else(|| self.default_document_path())
    }

    pub fn default_document_path(&self) -> PathBuf {
        self.data_dir.join("library.json")
    }

    /// Point at (or, with `None`, forget) the library document.
    pub fn set_document_path(&mut self, path: Option<PathBuf>) {
        self.config.document_path = path;
        save_config(&self.data_dir, &self.config);
    }

    /// A pre-document `library.db` still waiting to be converted.
    pub fn legacy_library_path(&self) -> Option<&Path> {
        self.config.legacy_library_path.as_deref()
    }

    /// Forget the legacy library, once it's been converted or dismissed.
    pub fn clear_legacy_library(&mut self) {
        self.config.legacy_library_path = None;
        save_config(&self.data_dir, &self.config);
    }

    /// Drop the open catalog (and its name index), releasing the handles on both
    /// db files. Call before replacing `reference.db` on disk so nothing is
    /// still reading the file being swapped out.
    pub fn close(&mut self) {
        self.catalog = None;
        self.index = None;
    }

    /// (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.working_db_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())
    }
}