//! Rebuilding the sidebar from the catalog, and pushing catalog-derived
//! state into the grid: the selection flags, the lifted cells, the
//! per-cell collection badges, and the membership sheet's own rows.
//!
//! `offline_state` and `direct_holdings` live here rather than beside the
//! menu or the tray that reads them, because both are catalog reads over
//! the tree — the same shape as `refresh_tree` itself, just narrower.

use std::rc::Rc;

use dr_catalog::collections::{self as coll, CollectionKind};
use dr_catalog::Catalog;
use dr_types::{CollectionId, ImageId};
use slint::{ComponentHandle as _, Model as _};

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

use super::controller::CollectionsController;

/// Rebuild the sidebar from the catalog.
///
/// Called after every edit. The whole tree rather than a patch: a rename can
/// reorder siblings, a delete promotes children, and a drop changes counts on
/// every ancestor — diffing that against the model would be more code than the
/// query costs, and the tree is tens of rows, not thousands.
pub fn refresh_tree(window: &AppWindow, ctl: &Rc<CollectionsController>, catalog: &Catalog) {
    // The albums share the sidebar, and every caller of this is a moment
    // they may have changed too — a merge brings both.
    if let Some(albums) = ctl.albums.borrow().as_ref() {
        crate::albums_ui::refresh_from(window, albums, catalog);
    }
    let rows = match coll::tree(catalog.connection()) {
        Ok(r) => r,
        Err(e) => {
            window
                .global::<Collections>()
                .set_collection_error(format!("reading collections: {e}").into());
            return;
        }
    };

    let collapsed = ctl.collapsed.borrow();
    // TRACES: FR-NC-6a | FR-NC-6c
    // How much of each collection is already on the device, rolled up the tree
    // — computed once for the whole sidebar rather than per row.
    let held = offline_state(catalog, &rows);

    // A row is hidden when any ancestor is collapsed. The tree arrives
    // depth-first, so tracking the shallowest collapsed depth seen is enough —
    // no ancestor lookup per row.
    let mut hide_below: Option<usize> = None;
    let mut ids = Vec::new();
    let mut smart = Vec::new();
    let mut has_kids = Vec::new();
    let mut nested = Vec::new();
    let mut out = Vec::new();

    for row in &rows {
        if let Some(depth) = hide_below {
            if row.depth > depth {
                continue;
            }
            hide_below = None;
        }

        let id = row.collection.id;
        let expanded = !collapsed.contains(&id);
        if row.has_children && !expanded {
            hide_below = Some(row.depth);
        }

        // Deep counts are one query per row. That is fine at sidebar scale and
        // wrong at grid scale, which is why the grid does not do this.
        let deep =
            coll::deep_count(catalog.connection(), id).unwrap_or(row.collection.direct_count);

        let offline = held.get(&id).copied().unwrap_or_default();

        ids.push(id);
        smart.push(row.collection.kind == CollectionKind::Smart);
        has_kids.push(row.has_children);
        nested.push(row.collection.parent.is_some());
        out.push(CollectionRow {
            id: id.0 as i32,
            name: row.collection.name.as_str().into(),
            depth: row.depth as i32,
            direct_count: row.collection.direct_count as i32,
            deep_count: deep as i32,
            has_children: row.has_children,
            expanded,
            smart: row.collection.kind == CollectionKind::Smart,
            // An empty collection is never "kept": every one of its zero
            // photographs being here is true and says nothing, and a full tray
            // beside an empty collection is a lie about what a trip would cost
            // to take.
            pinned: offline.total > 0 && offline.pinned == offline.total,
            partly_pinned: offline.pinned > 0 && offline.pinned < offline.total,
        });
    }

    *ctl.row_ids.borrow_mut() = ids;
    *ctl.row_smart.borrow_mut() = smart;
    *ctl.row_has_children.borrow_mut() = has_kids;
    *ctl.row_nested.borrow_mut() = nested;
    window
        .global::<Collections>()
        .set_collection_rows(slint::ModelRc::new(slint::VecModel::from(out)));

    // The rows are what `sync_reorderable` reads, so it has to be told they
    // changed: a collection that gains a child, or one that is deleted out from
    // under the scope, changes whether the grid can be reordered without the
    // scope itself moving.
    sync_reorderable(window);
}

/// TRACES: FR-NC-6a | FR-NC-6c
/// How many of a collection's photographs are pinned, and how many there are.
///
/// Counted over *members*, not distinct images: an image filed in both a parent
/// and a child is counted in each, which is what makes the roll-up below a sum
/// rather than a set union. That inflates the totals of a tree that files the
/// same photograph twice, and it does not matter here — the only questions
/// asked of these numbers are "all of them?" and "none of them?", and both
/// survive the double count.
#[derive(Debug, Clone, Copy, Default, PartialEq, Eq)]
struct OfflineCount {
    total: usize,
    pinned: usize,
}

/// The offline state of every collection in the tree, descendants included.
///
/// One query for the direct membership, then a single reverse pass to fold each
/// row into its parent. The alternative — `descendants` plus a count per row —
/// is two queries per collection, and the sidebar rebuilds after every drop,
/// rename and rating change.
///
/// The reverse pass is correct because `tree` emits parents before children:
/// walking it backwards means every child has already been folded in by the
/// time its parent is reached, however deep the nesting goes.
fn offline_state(
    catalog: &Catalog,
    rows: &[coll::TreeRow],
) -> std::collections::HashMap<CollectionId, OfflineCount> {
    let mut counts: std::collections::HashMap<CollectionId, OfflineCount> =
        std::collections::HashMap::new();

    // `tier_actual`, not `pinned`: the question a user is asking of this icon is
    // "will these open on the aeroplane", and a pin whose download has not run
    // yet answers no (see the note on `tier_actual` in `dr_catalog::cache`).
    let sql = "SELECT cm.collection_id,
                      count(*),
                      coalesce(sum(CASE WHEN ic.tier_actual >= ?1 THEN 1 ELSE 0 END), 0)
                 FROM collection_members cm
                 LEFT JOIN image_cache ic ON ic.image_id = cm.image_id
                GROUP BY cm.collection_id";

    match catalog.connection().prepare(sql).and_then(|mut stmt| {
        let rows = stmt.query_map(rusqlite::params![dr_types::Tier::Original.stored()], |r| {
            Ok((
                CollectionId(r.get::<_, i64>(0)? as u64),
                r.get::<_, i64>(1)? as usize,
                r.get::<_, i64>(2)? as usize,
            ))
        })?;
        rows.collect::<Result<Vec<_>, _>>()
    }) {
        Ok(direct) => {
            for (id, total, pinned) in direct {
                counts.insert(id, OfflineCount { total, pinned });
            }
        }
        Err(e) => {
            // Not fatal: the tray then reads "nothing kept", which is the safe
            // direction — it offers a download rather than claiming a trip is
            // already on the device.
            log::debug!("reading offline state: {e}");
            return counts;
        }
    }

    for row in rows.iter().rev() {
        let Some(parent) = row.collection.parent else {
            continue;
        };
        let child = counts.get(&row.collection.id).copied().unwrap_or_default();
        if child.total == 0 {
            continue;
        }
        let entry = counts.entry(parent).or_default();
        entry.total += child.total;
        entry.pinned += child.pinned;
    }

    counts
}

/// Mark which cells are currently lifted out by a drag.
///
/// Separate from [`sync_selection`] because the two differ: the selection
/// persists after the drag, the lift lasts only while it is in flight.
pub fn sync_lifted(window: &AppWindow, lifted: &[ImageId], ids: &[ImageId]) {
    let model = window.global::<Library>().get_library_cells();
    for (row, id) in ids.iter().enumerate() {
        let want = lifted.contains(id);
        if let Some(mut cell) = model.row_data(row) {
            if cell.lifted != want {
                cell.lifted = want;
                model.set_row_data(row, cell);
            }
        }
    }
}

/// Push the current selection into the grid model's `selected` flags.
///
/// The model carries the flag per cell so Slint can style without a lookup;
/// this is what keeps the two in step after a scrub, a drop, or a click.
pub fn sync_selection(window: &AppWindow, ctl: &Rc<CollectionsController>, ids: &[ImageId]) {
    let selection = ctl.selection.borrow();
    let model = window.global::<Library>().get_library_cells();

    // The anchor is deliberately **not** pushed to the grid.
    //
    // It used to be, and it was drawn as a thin ring inside the cell. Two
    // things were wrong with that. It was the clearest mark on the cell, so it
    // read as *the* selection to anyone who had not written it; and an anchor
    // outlives a deselection, so the ring sat around the last photograph
    // touched while nothing was selected at all — indistinguishable from a cell
    // that had stayed behind.
    //
    // The ordinal still lives in the controller and still decides where a range
    // extends from. What is gone is the claim that the user needs to see it:
    // the selection bar says "Tap the last photograph" while a range is armed,
    // which answers the question the ring was there to answer.
    for (row, id) in ids.iter().enumerate() {
        let want = selection.contains(id);
        if let Some(mut cell) = model.row_data(row) {
            if cell.selected != want {
                cell.selected = want;
                model.set_row_data(row, cell);
            }
        }
    }

    window
        .global::<Library>()
        .set_library_selected_count(selection.len() as i32);
}

/// TRACES: FR-CAT-7
/// Whether what the grid is showing has an order the user can change.
///
/// A single manual collection: not the whole library, not a saved filter whose
/// membership is a rule, and not a set — a set draws its descendants' images
/// too, and two children's `position` columns are unrelated integers that would
/// interleave arbitrarily.
///
/// Read off the tree rows the sidebar already draws rather than asked of the
/// catalog. `smart` and `has_children` are the only two facts it needs and both
/// are in the model already, so this cannot disagree with what the user is
/// looking at, and a scope change costs no extra query.
pub(super) fn sync_reorderable(window: &AppWindow) {
    let id = window.get_collection_selected();
    let rows = window.global::<Collections>().get_collection_rows();
    let manual = id > 0
        && (0..rows.row_count())
            .filter_map(|i| rows.row_data(i))
            .find(|r| r.id == id)
            .is_some_and(|r| !r.smart && !r.has_children);
    window.global::<Library>().set_library_reorderable(manual);
}

/// Refresh the per-cell "in this many collections" badges.
///
/// One query for the whole window rather than one per cell: 120 cells is 120
/// round trips otherwise, on every drop.
pub fn sync_badges(window: &AppWindow, catalog: &Catalog, ids: &[ImageId]) {
    if ids.is_empty() {
        return;
    }

    let placeholders = std::iter::repeat_n("?", ids.len())
        .collect::<Vec<_>>()
        .join(",");
    let sql = format!(
        "SELECT m.image_id, count(*)
           FROM collection_members m
           JOIN collections c ON c.id = m.collection_id
          WHERE m.image_id IN ({placeholders}) AND c.deleted = 0
          GROUP BY m.image_id"
    );

    let params: Vec<rusqlite::types::Value> = ids
        .iter()
        .map(|i| rusqlite::types::Value::Integer(i.0 as i64))
        .collect();

    let mut counts = std::collections::HashMap::new();
    if let Ok(mut stmt) = catalog.connection().prepare(&sql) {
        if let Ok(rows) = stmt.query_map(rusqlite::params_from_iter(params.iter()), |r| {
            Ok((r.get::<_, i64>(0)?, r.get::<_, i64>(1)?))
        }) {
            for (id, n) in rows.flatten() {
                counts.insert(id, n as i32);
            }
        }
    }

    let model = window.global::<Library>().get_library_cells();
    for (row, id) in ids.iter().enumerate() {
        let want = counts.get(&(id.0 as i64)).copied().unwrap_or(0);
        if let Some(mut cell) = model.row_data(row) {
            if cell.collection_count != want {
                cell.collection_count = want;
                model.set_row_data(row, cell);
            }
        }
    }
}

/// TRACES: FR-CAT-7
/// What a collection directly holds: its own member rows, and its own children.
///
/// One query each rather than reusing `deep_count`, which counts descendants'
/// photographs — see [`menu_detail`] for why the menu needs the direct numbers.
pub(super) fn direct_holdings(
    conn: &rusqlite::Connection,
    id: CollectionId,
) -> Result<(usize, usize), dr_catalog::CatalogError> {
    let holds: i64 = conn.query_row(
        "SELECT count(*) FROM collection_members WHERE collection_id = ?1",
        [id.0 as i64],
        |r| r.get(0),
    )?;
    let children: i64 = conn.query_row(
        "SELECT count(*) FROM collections WHERE parent_id = ?1 AND deleted = 0",
        [id.0 as i64],
        |r| r.get(0),
    )?;
    Ok((holds as usize, children as usize))
}

/// TRACES: FR-CAT-7 | FR-UI-4
/// Rebuild the membership sheet from the selection as it stands.
///
/// Called on open and after every removal rather than patched: a removal can
/// take the last selected photograph out of a collection, and that row then has
/// to go — a patched model would leave a "Remove" that removes nothing.
pub(super) fn refresh_membership(
    window: &AppWindow,
    ctl: &Rc<CollectionsController>,
    catalog: &Catalog,
) {
    let chosen = ctl.selected();
    let total = chosen.len();
    let rows = match coll::membership_of(catalog.connection(), &chosen) {
        Ok(r) => r,
        Err(e) => {
            window
                .global::<Collections>()
                .set_collection_error(format!("reading collections: {e}").into());
            Vec::new()
        }
    };

    let out: Vec<crate::MembershipRow> = rows
        .into_iter()
        .map(|m| crate::MembershipRow {
            id: m.id.0 as i32,
            name: m.name.as_str().into(),
            holding: m.holding as i32,
            // "1 of 1" is arithmetic nobody asked for; with one photograph
            // selected the name already says everything true about it.
            detail: if total <= 1 {
                slint::SharedString::new()
            } else {
                format!("{} of {total}", m.holding).into()
            },
        })
        .collect();

    window
        .global::<Collections>()
        .set_membership_rows(slint::ModelRc::new(slint::VecModel::from(out)));
}

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

    /// TRACES: FR-NC-6a | FR-NC-6c
    /// A catalog with `n` images, for the offline roll-up tests.
    fn catalog_with_images(n: usize) -> (Catalog, Vec<ImageId>) {
        let cat = Catalog::in_memory().unwrap();
        cat.connection()
            .execute(
                "INSERT INTO roots (id, kind, label) VALUES (1, 'remote', 'test')",
                [],
            )
            .unwrap();
        let mut ids = Vec::new();
        for i in 0..n {
            cat.connection()
                .execute(
                    "INSERT INTO images (root_id, source_ref, added_at)
                     VALUES (1, ?1, 0)",
                    rusqlite::params![format!("Photos/img{i:03}.CR2")],
                )
                .unwrap();
            ids.push(ImageId(cat.connection().last_insert_rowid() as u64));
        }
        (cat, ids)
    }

    /// Record an image as held on this device, as a finished download would.
    fn mark_held(cat: &Catalog, image: ImageId) {
        cat.connection()
            .execute(
                "INSERT INTO image_cache (image_id, tier_actual, tier_desired, bytes, pinned)
                 VALUES (?1, ?2, ?2, 100, 1)",
                rusqlite::params![image.0 as i64, dr_types::Tier::Original.stored()],
            )
            .unwrap();
    }

    #[test]
    fn a_parent_reads_as_kept_only_when_its_children_are_too() {
        // The tray on a parent answers for the subtree, because that is what
        // keeping a parent downloads. A parent that showed a full tray over a
        // child with nothing downloaded would be a promise the aeroplane
        // breaks.
        let (cat, images) = catalog_with_images(4);
        let c = cat.connection();
        let parent = coll::create(c, "Trip", None, CollectionKind::Manual).unwrap();
        let child = coll::create(c, "Day one", Some(parent), CollectionKind::Manual).unwrap();
        coll::add_images(c, parent, &images[0..2]).unwrap();
        coll::add_images(c, child, &images[2..4]).unwrap();

        // Everything the parent holds directly, and nothing of the child's.
        mark_held(&cat, images[0]);
        mark_held(&cat, images[1]);

        let rows = coll::tree(c).unwrap();
        let state = offline_state(&cat, &rows);

        assert_eq!(
            state[&parent],
            OfflineCount {
                total: 4,
                pinned: 2
            }
        );
        assert_eq!(
            state[&child],
            OfflineCount {
                total: 2,
                pinned: 0
            }
        );

        mark_held(&cat, images[2]);
        mark_held(&cat, images[3]);
        let state = offline_state(&cat, &coll::tree(c).unwrap());
        assert_eq!(
            state[&parent],
            OfflineCount {
                total: 4,
                pinned: 4
            }
        );
    }

    #[test]
    fn a_grandchild_rolls_all_the_way_up() {
        // The reverse pass has to survive depth: a photograph three levels down
        // is still part of what the top-level collection would download.
        let (cat, images) = catalog_with_images(1);
        let c = cat.connection();
        let top = coll::create(c, "2024", None, CollectionKind::Manual).unwrap();
        let mid = coll::create(c, "Corsica", Some(top), CollectionKind::Manual).unwrap();
        let leaf = coll::create(c, "Bonifacio", Some(mid), CollectionKind::Manual).unwrap();
        coll::add_images(c, leaf, &images).unwrap();

        let state = offline_state(&cat, &coll::tree(c).unwrap());

        assert_eq!(
            state[&top],
            OfflineCount {
                total: 1,
                pinned: 0
            }
        );
        assert_eq!(
            state[&mid],
            OfflineCount {
                total: 1,
                pinned: 0
            }
        );
    }

    #[test]
    fn an_empty_collection_has_nothing_to_keep() {
        // Guards the reading that would put a full tray beside an empty
        // collection: every one of its zero photographs is here, which is true
        // and useless. `refresh_tree` requires a non-zero total before drawing
        // one, and this is the fact it relies on.
        let (cat, _) = catalog_with_images(0);
        let c = cat.connection();
        let empty = coll::create(c, "Nothing yet", None, CollectionKind::Manual).unwrap();

        let state = offline_state(&cat, &coll::tree(c).unwrap());
        assert_eq!(state.get(&empty).copied().unwrap_or_default().total, 0);
    }
}