//! Soft delete: moving images to the trash on the server, restoring them,
//! and the worker drain both share.
//!
//! A drop is a *soft delete*: the file moves to a trash folder on the
//! server and the catalog records where it came from. Nothing is
//! destroyed until the user empties it, a separate, deliberate action.

use std::cell::RefCell;
use std::rc::Rc;

use dr_catalog::Catalog;
use dr_types::ImageId;
use slint::ComponentHandle;

use crate::{AppWindow, Collections, Library};

use super::controller::CollectionsController;
use super::tree_sync::refresh_tree;

/// Begin a soft delete: plan the moves, then hand them to a worker.
///
/// The plan is built here because it reads the catalog, which is not `Send`; the
/// worker gets paths and ids and needs no catalog to do its half.
#[allow(clippy::too_many_arguments)]
pub(super) fn start_trash(
    window: &AppWindow,
    ctl: &Rc<CollectionsController>,
    catalog: &Rc<RefCell<Option<Catalog>>>,
    session: &Rc<dyn Fn() -> Option<dr_sync::Connection>>,
    images: &[ImageId],
    reload: &Rc<dyn Fn()>,
) {
    let Some(conn) = session() else {
        window
            .global::<Collections>()
            .set_collection_error("Open a library first.".into());
        return;
    };

    let moves = {
        let borrow = catalog.borrow();
        let Some(cat) = borrow.as_ref() else { return };
        match crate::trash::plan_trash(cat, &conn.account.root, images) {
            Ok(m) => m,
            Err(e) => {
                window
                    .global::<Collections>()
                    .set_collection_error(format!("planning delete: {e}").into());
                return;
            }
        }
    };

    if moves.is_empty() {
        return;
    }

    log::info!("moving {} image(s) to the trash", moves.len());
    window
        .global::<Library>()
        .set_library_status(format!("Moving {} to the trash…", moves.len()).into());
    // The images are leaving the grid; a selection pointing at them would
    // survive as a set of ids the user can no longer see.
    ctl.clear_selection();

    let count = moves.len();
    let rx = crate::trash::spawn_move(
        conn.clone(),
        moves,
        crate::trash::Direction::ToTrash,
        crate::library::catalog_path(&conn.account),
    );

    drain_trash(
        window.as_weak(),
        ctl.clone(),
        catalog.clone(),
        rx,
        reload.clone(),
        format!("Moving {count} photograph(s) to the trash"),
    );
}

/// TRACES: FR-CAT-15
/// Put trashed images back where they came from.
///
/// The mirror of [`start_trash`], and separate from it rather than a `direction`
/// parameter on one function: the two differ in what they plan, what they report
/// and what they say when the plan comes back empty, and the shared part is the
/// three lines that spawn the worker.
///
/// An image whose origin was never recorded is skipped by
/// [`crate::trash::plan_restore`] rather than guessed at. That can make the plan
/// shorter than the selection, which is why an empty plan is reported here
/// instead of returning silently — the user pressed a button and is owed an
/// answer either way.
pub(super) fn start_restore(
    window: &AppWindow,
    ctl: &Rc<CollectionsController>,
    catalog: &Rc<RefCell<Option<Catalog>>>,
    session: &Rc<dyn Fn() -> Option<dr_sync::Connection>>,
    images: &[ImageId],
    reload: &Rc<dyn Fn()>,
) {
    let Some(conn) = session() else {
        window
            .global::<Collections>()
            .set_collection_error("Open a library first.".into());
        return;
    };

    let moves = {
        let borrow = catalog.borrow();
        let Some(cat) = borrow.as_ref() else { return };
        match crate::trash::plan_restore(cat, images) {
            Ok(m) => m,
            Err(e) => {
                window
                    .global::<Collections>()
                    .set_collection_error(format!("planning restore: {e}").into());
                return;
            }
        }
    };

    if moves.is_empty() {
        // Said out loud rather than passed over in silence: a button that does
        // nothing visible reads as broken, and the reason here is specific.
        window.global::<Collections>().set_collection_error(
            "Nothing to restore — no record of where these came from.".into(),
        );
        return;
    }

    log::info!("restoring {} image(s) from the trash", moves.len());
    window
        .global::<Library>()
        .set_library_status(format!("Restoring {}…", moves.len()).into());
    // The images are leaving the trash view, so a selection pointing at them
    // would survive as ids the user can no longer see.
    ctl.clear_selection();

    let count = moves.len();
    let rx = crate::trash::spawn_move(
        conn.clone(),
        moves,
        crate::trash::Direction::Restore,
        crate::library::catalog_path(&conn.account),
    );

    drain_trash(
        window.as_weak(),
        ctl.clone(),
        catalog.clone(),
        rx,
        reload.clone(),
        format!("Restoring {count} photograph(s)"),
    );
}

/// Drain a trash worker on the UI thread.
///
/// Same shape as the scan and thumbnail drains: an mpsc channel polled by a
/// Slint timer, so nothing blocks the event loop (NFR-P9).
pub(super) fn drain_trash(
    weak: slint::Weak<AppWindow>,
    ctl: Rc<CollectionsController>,
    catalog: Rc<RefCell<Option<Catalog>>>,
    rx: std::sync::mpsc::Receiver<crate::trash::TrashMessage>,
    reload: Rc<dyn Fn()>,
    // What the register calls this operation. Passed in rather than derived
    // here: the three callers move files to the trash, back out of it, and
    // delete them outright, and "Deleting 40 photographs" is the one word of
    // the three that must not appear over a restore.
    title: String,
) {
    use crate::trash::TrashMessage;

    let timer = slint::Timer::default();
    let ctl_cb = ctl.clone();

    // A server-side MOVE per file, so it is a transfer in the sense that
    // matters: it takes as long as the connection is slow, and it can fail
    // halfway with the library in two states at once.
    let job = ctl.activity.begin(crate::activity::Kind::Trash, title);

    timer.start(
        slint::TimerMode::Repeated,
        std::time::Duration::from_millis(120),
        move || {
            let Some(w) = weak.upgrade() else { return };

            loop {
                let msg = match rx.try_recv() {
                    Ok(m) => m,
                    Err(std::sync::mpsc::TryRecvError::Empty) => return,
                    Err(std::sync::mpsc::TryRecvError::Disconnected) => {
                        // A worker that died without reporting must not leave the
                        // status line mid-sentence.
                        job.fail("stopped without finishing");
                        stop_trash(&ctl_cb);
                        return;
                    }
                };

                match msg {
                    TrashMessage::Progress {
                        done,
                        total,
                        failed,
                    } => {
                        let status = if failed > 0 {
                            format!("{done} / {total} · {failed} failed")
                        } else {
                            format!("{done} / {total}")
                        };
                        job.progress(done, total);
                        if failed > 0 {
                            job.detail(format!("{failed} failed"));
                        }
                        w.global::<Library>().set_library_status(status.into());
                    }
                    TrashMessage::Done { moved, failed } => {
                        // Reported honestly, including the partial case: "38 of
                        // 40" is the truth when two files could not be moved,
                        // and claiming 40 would hide a real problem.
                        let status = if failed.is_empty() {
                            format!("{moved} image(s) done")
                        } else {
                            format!("{moved} done · {} failed", failed.len())
                        };
                        // A partial failure is a failure in the register: the
                        // library is now in two states at once, which is
                        // exactly the thing worth keeping on the list.
                        if failed.is_empty() {
                            job.finish(status.clone());
                        } else {
                            job.fail(status.clone());
                        }
                        w.global::<Library>().set_library_status(status.into());
                        if let Some(first) = failed.first() {
                            w.global::<Collections>()
                                .set_collection_error(first.as_str().into());
                        }

                        let borrow = catalog.borrow();
                        if let Some(cat) = borrow.as_ref() {
                            refresh_trash(&w, cat);
                            refresh_tree(&w, &ctl_cb, cat);
                            // A copy trashed or restored by hand changes
                            // which files are in the library twice.
                            crate::duplicates_ui::refresh_count(&w, cat);
                        }
                        drop(borrow);

                        // The grid changed: images left the library, or came
                        // back into it.
                        reload();
                        stop_trash(&ctl_cb);
                        return;
                    }
                }
            }
        },
    );

    *ctl.trash_timer.borrow_mut() = Some(timer);
}

fn stop_trash(ctl: &Rc<CollectionsController>) {
    if let Some(t) = ctl.trash_timer.borrow().as_ref() {
        t.stop();
    }
}

/// Refresh the sidebar's trash count and size.
///
/// The size is formatted here rather than in Slint, which has no byte-size
/// formatting — and the number is what tells the user whether emptying is worth
/// it.
pub fn refresh_trash(window: &AppWindow, catalog: &Catalog) {
    let (n, bytes) = dr_catalog::trash::summary(catalog.connection()).unwrap_or((0, 0));
    window.global::<Collections>().set_trash_count(n as i32);
    window.global::<Collections>().set_trash_label(if n == 0 {
        slint::SharedString::new()
    } else {
        format!("{n} · {}", format_bytes(bytes)).into()
    });
}

/// Bytes as a human-readable size.
///
/// Binary units, one decimal place past a kilobyte: a RAW library is measured in
/// gigabytes and "3.4 GB" is the figure a photographer reasons about, where
/// 3_650_722_201 is not.
fn format_bytes(bytes: u64) -> String {
    const KB: f64 = 1024.0;
    let b = bytes as f64;
    if bytes < 1024 {
        return format!("{bytes} B");
    }
    for (limit, unit) in [
        (KB * KB, "kB"),
        (KB * KB * KB, "MB"),
        (KB * KB * KB * KB, "GB"),
    ] {
        if b < limit {
            return format!("{:.1} {unit}", b / (limit / KB));
        }
    }
    format!("{:.1} TB", b / (KB * KB * KB * KB))
}