//! App state: the open [`Catalog`] and fuzzy [`NameIndex`], plus the paths,
//! the device's libraries, and the sync account.
//!
//! Each library lives in an internal SQLite working copy under the app data
//! dir, which works fully offline. One of them is open at a time — the active
//! library — and every command works on that one. When the device is signed in to a sync
//! server, that copy is reconciled with the server's whenever it can be reached
//! (see `sync.rs` and [`mtgc_core::sync::remote`]).

use std::path::{Path, PathBuf};
use std::sync::atomic::AtomicBool;
use std::sync::Arc;

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

/// Small app-shell preferences persisted across restarts, distinct from the
/// user's library data.
///
/// Fields from older builds (`document_path`, `document_name`, from when the
/// library was a file in a synced folder) are simply ignored when read.
#[derive(Default, Serialize, Deserialize, Clone)]
struct PersistedConfig {
    /// 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>,
    /// The sync server this device is (or was last) signed in to.
    #[serde(default)]
    sync: Option<SyncAccount>,
    /// The libraries on this device, the default one first. Never empty once
    /// loaded: a config from before named libraries gets the default.
    #[serde(default)]
    libraries: Vec<LocalLibrary>,
    /// The id of the library that's open.
    #[serde(default)]
    active_library: String,
    /// Server libraries removed from this device, which syncing therefore
    /// doesn't download again.
    #[serde(default)]
    dismissed_remote: Vec<String>,
}

/// The id of the library every device starts with. Its files stay where the
/// one library always lived, so upgrading moves nothing.
pub const DEFAULT_LIBRARY: &str = "default";

/// One of the libraries on this device.
#[derive(Serialize, Deserialize, Clone, Debug, PartialEq)]
pub struct LocalLibrary {
    /// Local only: the folder it lives in. Never shown.
    pub id: String,
    pub name: String,
    /// The server's id for it, once linked to a library there.
    #[serde(default)]
    pub remote_id: Option<String>,
    /// Whether it should be on the server. Off for a library kept on this
    /// device only — a scratch library to try things in, say.
    #[serde(default = "yes")]
    pub sync: bool,
    /// It was linked, and another device deleted it from the server. The copy
    /// here stays until the user removes it or puts it back on the server.
    #[serde(default)]
    pub server_deleted: bool,
}

fn yes() -> bool {
    true
}

impl LocalLibrary {
    pub fn is_default(&self) -> bool {
        self.id == DEFAULT_LIBRARY
    }
}

fn default_library() -> LocalLibrary {
    LocalLibrary {
        id: DEFAULT_LIBRARY.into(),
        name: "Main".into(),
        remote_id: None,
        sync: true,
        server_deleted: false,
    }
}

/// A fresh id for a library's folder.
fn new_library_id() -> String {
    mtgc_core::sync::account::random_token()
        .chars()
        .filter(char::is_ascii_alphanumeric)
        .take(16)
        .collect()
}

/// This device's sync server account.
#[derive(Serialize, Deserialize, Clone, Debug, PartialEq)]
pub struct SyncAccount {
    pub server_url: String,
    /// This device's token. `None` once signed out, or once the server stopped
    /// accepting it; the rest is kept so signing back in can be offered with
    /// the address already filled in.
    #[serde(default)]
    pub token: Option<String>,
    pub user: AccountUser,
    #[serde(default)]
    pub device_id: i64,
    /// Unix seconds of the last sync that completed.
    #[serde(default)]
    pub last_synced_at: Option<i64>,
}

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

fn load_config(data_dir: &Path) -> PersistedConfig {
    let mut cfg = read_config(data_dir);
    // Before named libraries there was one, which is the default now.
    if !cfg.libraries.iter().any(LocalLibrary::is_default) {
        cfg.libraries.insert(0, default_library());
    }
    if !cfg.libraries.iter().any(|l| l.id == cfg.active_library) {
        cfg.active_library = DEFAULT_LIBRARY.into();
    }
    cfg
}

fn read_config(data_dir: &Path) -> PersistedConfig {
    let Ok(text) = std::fs::read_to_string(config_path(data_dir)) else {
        return PersistedConfig::default();
    };
    // Every field defaults, so an older or partial file parses fine and simply
    // leaves the unknown settings unset.
    let mut cfg: PersistedConfig = serde_json::from_str(&text).unwrap_or_default();

    // Builds before the document format stored `library_path` pointing at a
    // SQLite file the user managed themselves. Pick that up so the UI can offer
    // to convert it once — but never open it as the working copy.
    if cfg.legacy_library_path.is_none() {
        #[derive(Deserialize)]
        struct OldConfig {
            library_path: Option<PathBuf>,
        }
        cfg.legacy_library_path = serde_json::from_str::<OldConfig>(&text)
            .ok()
            .and_then(|c| c.library_path)
            .filter(|p| p.extension().is_some_and(|e| e != "json"));
    }
    cfg
}

fn save_config(data_dir: &Path, cfg: &PersistedConfig) {
    let Ok(text) = serde_json::to_string_pretty(cfg) else {
        return;
    };
    // Written beside and renamed into place, so a crash mid-write can't leave
    // a truncated config that silently signs the device out.
    let path = config_path(data_dir);
    let tmp = path.with_extension("json.tmp");
    if let Err(e) = write_private(&tmp, &text).and_then(|_| std::fs::rename(&tmp, &path)) {
        crate::mlog!("save_config: {e}");
        let _ = std::fs::remove_file(&tmp);
    }
}

/// Write a file only this user can read: the config holds the device's sync
/// token. (App data is already private on Android; this covers desktop.)
fn write_private(path: &Path, text: &str) -> std::io::Result<()> {
    use std::io::Write;
    let mut opts = std::fs::OpenOptions::new();
    opts.write(true).create(true).truncate(true);
    #[cfg(unix)]
    {
        use std::os::unix::fs::OpenOptionsExt;
        opts.mode(0o600);
    }
    let mut f = opts.open(path)?;
    f.write_all(text.as_bytes())?;
    f.sync_all()
}

/// The folder a library's files live in.
fn library_dir(data_dir: &Path, id: &str) -> PathBuf {
    if id == DEFAULT_LIBRARY {
        data_dir.to_path_buf()
    } else {
        data_dir.join("libraries").join(id)
    }
}

/// 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 of the active library: the library itself,
    /// on this device. 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, on
    /// every foreground/background transition, and on reconnecting, so
    /// overlapping calls are easy to provoke; a second one would only repeat
    /// the first one's work.
    pub sync_running: bool,
    /// Why the last sync failed, until one succeeds. Not persisted: after a
    /// restart the next sync says soon enough.
    pub sync_error: Option<String>,
    /// The first sync with this account found a library both here and on the
    /// server, and only the user can say whether to combine them or take the
    /// server's. Syncing waits until they do.
    pub sync_needs_choice: bool,
    /// Set while a sign-in waits on the browser; flipping it abandons the wait.
    pub sign_in_cancel: Option<Arc<AtomicBool>>,
}

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: library_dir(&data_dir, &config.active_library).join("working.db"),
            config,
            data_dir,
            catalog: None,
            index: None,
            ingest_cancel: None,
            sync_running: false,
            sync_error: None,
            sync_needs_choice: false,
            sign_in_cancel: None,
        };
        // A library whose folder vanished would otherwise be recreated empty
        // by opening it, which is fine — but its folder must exist first.
        let _ = std::fs::create_dir_all(s.library_dir(&s.config.active_library.clone()));
        crate::mlog!(
            "AppState::new: sync={:?} library={} working={} reference={} (exists={})",
            s.config.sync.as_ref().map(|a| (&a.server_url, &a.user.username, a.token.is_some())),
            s.config.active_library,
            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 sync account, signed in or not.
    pub fn sync_account(&self) -> Option<&SyncAccount> {
        self.config.sync.as_ref()
    }

    pub fn set_sync_account(&mut self, account: Option<SyncAccount>) {
        self.config.sync = account;
        save_config(&self.data_dir, &self.config);
    }

    /// Change the sync account in place and persist it. A no-op without one.
    pub fn update_sync_account(&mut self, f: impl FnOnce(&mut SyncAccount)) {
        if let Some(a) = self.config.sync.as_mut() {
            f(a);
            save_config(&self.data_dir, &self.config);
        }
    }

    /// Forget every link to a server library. For signing in to a different
    /// account or server, where the old ids mean nothing.
    pub fn forget_remote_links(&mut self) {
        for lib in &mut self.config.libraries {
            lib.remote_id = None;
            lib.server_deleted = false;
        }
        self.config.dismissed_remote.clear();
        save_config(&self.data_dir, &self.config);
    }

    // --- libraries ------------------------------------------------------------

    pub fn libraries(&self) -> &[LocalLibrary] {
        &self.config.libraries
    }

    pub fn library(&self, id: &str) -> Option<&LocalLibrary> {
        self.config.libraries.iter().find(|l| l.id == id)
    }

    pub fn active_library(&self) -> &LocalLibrary {
        self.library(&self.config.active_library).expect("load_config keeps the active library listed")
    }

    /// The folder a library's files live in.
    pub fn library_dir(&self, id: &str) -> PathBuf {
        library_dir(&self.data_dir, id)
    }

    pub fn working_path(&self, id: &str) -> PathBuf {
        self.library_dir(id).join("working.db")
    }

    /// Where a library's sync merge base is kept. The default library keeps
    /// the name it had before there were others.
    pub fn base_path(&self, id: &str) -> PathBuf {
        if id == DEFAULT_LIBRARY {
            self.data_dir.join("sync-server-base.json")
        } else {
            self.library_dir(id).join("sync-base.json")
        }
    }

    /// Server libraries removed from this device.
    pub fn dismissed_remote(&self) -> &[String] {
        &self.config.dismissed_remote
    }

    /// Start a new, empty library. It isn't opened.
    pub fn create_library(&mut self, name: &str, sync: bool, remote_id: Option<String>) -> Result<LocalLibrary, String> {
        let name = self.check_name(name, None)?;
        let lib = LocalLibrary { id: new_library_id(), name, remote_id, sync, server_deleted: false };
        let dir = self.library_dir(&lib.id);
        std::fs::create_dir_all(&dir).map_err(|e| format!("Couldn't create the library: {e}"))?;
        // Created now, so the library exists on disk even before anything
        // is added to it.
        mtgc_core::db::open_library(&self.working_path(&lib.id)).map_err(|e| e.to_string())?;
        if let Some(r) = &lib.remote_id {
            self.config.dismissed_remote.retain(|d| d != r);
        }
        self.config.libraries.push(lib.clone());
        save_config(&self.data_dir, &self.config);
        Ok(lib)
    }

    /// A trimmed name, if no other library here already has it.
    pub fn check_name(&self, name: &str, except: Option<&str>) -> Result<String, String> {
        let name = name.trim();
        if name.is_empty() {
            return Err("A library needs a name.".into());
        }
        let taken = self
            .config
            .libraries
            .iter()
            .any(|l| Some(l.id.as_str()) != except && l.name.eq_ignore_ascii_case(name));
        if taken {
            return Err(format!("There's already a library called {name}."));
        }
        Ok(name.to_string())
    }

    /// Change a library in place and persist it. A no-op for an unknown id.
    pub fn update_library(&mut self, id: &str, f: impl FnOnce(&mut LocalLibrary)) {
        if let Some(lib) = self.config.libraries.iter_mut().find(|l| l.id == id) {
            f(lib);
            save_config(&self.data_dir, &self.config);
        }
    }

    /// Stop downloading a server library to this device.
    pub fn dismiss_remote(&mut self, remote_id: &str) {
        if !self.config.dismissed_remote.iter().any(|d| d == remote_id) {
            self.config.dismissed_remote.push(remote_id.to_string());
            save_config(&self.data_dir, &self.config);
        }
    }

    pub fn undismiss_remote(&mut self, remote_id: &str) {
        self.config.dismissed_remote.retain(|d| d != remote_id);
        save_config(&self.data_dir, &self.config);
    }

    /// Open another library.
    pub fn switch_library(&mut self, id: &str) -> Result<(), String> {
        if self.library(id).is_none() {
            return Err("There's no such library on this device.".into());
        }
        if self.config.active_library == id {
            return Ok(());
        }
        // A sync works on paths it took when it started.
        if self.sync_running {
            return Err("Wait for the sync to finish, then try again.".into());
        }
        let _ = std::fs::create_dir_all(self.library_dir(id));
        self.config.active_library = id.to_string();
        save_config(&self.data_dir, &self.config);
        self.working_db_path = self.working_path(id);
        self.reopen_catalog()
    }

    /// Delete a library and its files from this device. The active one is
    /// left by switching to the default first; the default itself stays.
    pub fn delete_library(&mut self, id: &str) -> Result<LocalLibrary, String> {
        let lib = self.library(id).cloned().ok_or("There's no such library on this device.")?;
        if lib.is_default() {
            return Err("The main library can't be deleted.".into());
        }
        if self.sync_running {
            return Err("Wait for the sync to finish, then try again.".into());
        }
        if self.config.active_library == id {
            self.switch_library(DEFAULT_LIBRARY)?;
        }
        self.config.libraries.retain(|l| l.id != id);
        save_config(&self.data_dir, &self.config);
        let dir = self.library_dir(id);
        if let Err(e) = std::fs::remove_dir_all(&dir) {
            crate::mlog!("delete_library: couldn't remove {}: {e}", dir.display());
        }
        Ok(lib)
    }

    /// 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(())
    }

    /// Reopen just the catalog, on the active library's working copy. The name
    /// index only reads card data, so it survives a switch of library.
    fn reopen_catalog(&mut self) -> Result<(), String> {
        if self.index.is_none() {
            return self.reopen();
        }
        self.catalog = None;
        if self.reference_path.exists() {
            self.catalog = Some(
                Catalog::open(&self.working_db_path, &self.reference_path).map_err(|e| e.to_string())?,
            );
        }
        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())
    }
}

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

    fn scratch(name: &str) -> PathBuf {
        let dir = std::env::temp_dir().join(format!("mtgc-cfg-{name}-{}", std::process::id()));
        let _ = std::fs::remove_dir_all(&dir);
        std::fs::create_dir_all(&dir).unwrap();
        dir
    }

    fn account() -> SyncAccount {
        SyncAccount {
            server_url: "https://mtgc.example".into(),
            token: Some("mtgc_secret".into()),
            user: AccountUser {
                id: "u1".into(),
                username: "alice".into(),
                display_name: "Alice".into(),
                email: "alice@example.com".into(),
                method: "local".into(),
            },
            device_id: 7,
            last_synced_at: Some(1_700_000_000),
        }
    }

    #[test]
    fn every_setting_round_trips() {
        let dir = scratch("round-trip");
        let scratch_lib = LocalLibrary {
            id: "abc".into(),
            name: "Scratch".into(),
            remote_id: Some("r1".into()),
            sync: false,
            server_deleted: true,
        };
        let cfg = PersistedConfig {
            legacy_library_path: Some(PathBuf::from("/tmp/old.db")),
            sync: Some(account()),
            libraries: vec![default_library(), scratch_lib],
            active_library: "abc".into(),
            dismissed_remote: vec!["r2".into()],
        };
        save_config(&dir, &cfg);

        let back = load_config(&dir);
        assert_eq!(back.legacy_library_path, cfg.legacy_library_path);
        assert_eq!(back.sync, cfg.sync);
        assert_eq!(back.libraries, cfg.libraries);
        assert_eq!(back.active_library, "abc");
        assert_eq!(back.dismissed_remote, cfg.dismissed_remote);
        assert!(!dir.join("config.json.tmp").exists());
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[cfg(unix)]
    #[test]
    fn the_config_holding_the_token_is_private() {
        use std::os::unix::fs::PermissionsExt;
        let dir = scratch("private");
        save_config(&dir, &PersistedConfig { sync: Some(account()), ..Default::default() });
        let mode = std::fs::metadata(config_path(&dir)).unwrap().permissions().mode();
        assert_eq!(mode & 0o777, 0o600);
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[test]
    fn a_folder_sync_config_still_loads() {
        // What the previous, folder-based build wrote. Its settings no longer
        // mean anything, but the file must not fail to load over them.
        let dir = scratch("folder-era");
        std::fs::write(
            config_path(&dir),
            r#"{"document_path":"/home/u/Sync/library.json","legacy_library_path":"/tmp/old.db","document_name":"decks.json"}"#,
        )
        .unwrap();

        let cfg = load_config(&dir);
        assert_eq!(cfg.legacy_library_path, Some(PathBuf::from("/tmp/old.db")));
        assert!(cfg.sync.is_none());
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[test]
    fn a_pre_document_config_offers_its_library_for_conversion() {
        let dir = scratch("legacy");
        std::fs::write(
            config_path(&dir),
            r#"{"library_path":"/home/u/Seafile/Decks-v1.db"}"#,
        )
        .unwrap();

        let cfg = load_config(&dir);
        assert_eq!(
            cfg.legacy_library_path,
            Some(PathBuf::from("/home/u/Seafile/Decks-v1.db"))
        );
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[test]
    fn a_library_path_that_is_already_json_is_not_treated_as_legacy() {
        let dir = scratch("json-path");
        std::fs::write(config_path(&dir), r#"{"library_path":"/home/u/lib.json"}"#).unwrap();

        assert!(load_config(&dir).legacy_library_path.is_none());
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[test]
    fn an_unreadable_or_corrupt_config_falls_back_to_defaults() {
        let dir = scratch("corrupt");
        assert!(load_config(&dir).sync.is_none(), "missing file");
        std::fs::write(config_path(&dir), "{not json").unwrap();
        assert!(load_config(&dir).sync.is_none(), "truncated file");
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[test]
    fn a_config_from_before_named_libraries_has_just_the_default() {
        let dir = scratch("pre-libraries");
        save_config(&dir, &PersistedConfig { sync: Some(account()), ..Default::default() });
        let cfg = load_config(&dir);
        assert_eq!(cfg.libraries, vec![default_library()]);
        assert_eq!(cfg.active_library, DEFAULT_LIBRARY);
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[test]
    fn the_default_library_keeps_the_files_it_always_had() {
        let dir = scratch("paths");
        let s = AppState::new(dir.clone());
        assert_eq!(s.working_db_path, dir.join("working.db"));
        assert_eq!(s.base_path(DEFAULT_LIBRARY), dir.join("sync-server-base.json"));
        assert_eq!(s.working_path("abc"), dir.join("libraries/abc/working.db"));
        assert_eq!(s.base_path("abc"), dir.join("libraries/abc/sync-base.json"));
        std::fs::remove_dir_all(&dir).unwrap();
    }

    #[test]
    fn libraries_can_be_created_switched_to_and_deleted() {
        let dir = scratch("libraries");
        let mut s = AppState::new(dir.clone());
        let lib = s.create_library("  Scratch ", false, None).unwrap();
        assert_eq!(lib.name, "Scratch");
        assert!(s.working_path(&lib.id).exists());
        assert!(s.create_library("scratch", true, None).is_err(), "names are unique");
        assert!(s.create_library(" ", true, None).is_err());

        s.switch_library(&lib.id).unwrap();
        assert_eq!(s.working_db_path, s.working_path(&lib.id));
        // Remembered across restarts.
        let mut s = AppState::new(dir.clone());
        assert_eq!(s.active_library().id, lib.id);

        s.sync_running = true;
        assert!(s.switch_library(DEFAULT_LIBRARY).is_err(), "not mid-sync");
        assert!(s.delete_library(&lib.id).is_err(), "not mid-sync");
        s.sync_running = false;

        assert!(s.delete_library(DEFAULT_LIBRARY).is_err());
        s.delete_library(&lib.id).unwrap();
        assert_eq!(s.active_library().id, DEFAULT_LIBRARY, "deleting the open one switches away");
        assert!(!s.library_dir(&lib.id).exists());
        assert_eq!(s.libraries().len(), 1);
        std::fs::remove_dir_all(&dir).unwrap();
    }
}