yog_inventory/

lib.rs

//! yog-inventory — real Minecraft Container/Menu screens for Yog mods.
//!
//! Unlike `yog-ui` (a HUD-drawn overlay screen with no real item slots), this
//! crate describes actual vanilla-style inventory screens: a block's own
//! slots plus, optionally, the player's own inventory grid underneath —
//! backed by a real Minecraft `BlockEntity`/`AbstractContainerMenu` on the
//! Java side, with real drag-and-drop and network sync for free.
//!
//! See `DESIGN.md` for the full architecture and phased plan. This crate
//! currently covers the data model (phase 2); the Java-side `BlockEntity`/
//! `Menu`/`Screen` plumbing lands in later phases.

use std::sync::atomic::{AtomicPtr, Ordering};

use serde::Deserialize;
use yog_abi::YogStr;

/// Pixel position of a single slot in vanilla GUI coordinate space (the same
/// space vanilla screens use: origin at the panel's top-left corner, one
/// vanilla slot = 18×18px).
#[derive(Debug, Clone, PartialEq, Deserialize)]
pub struct SlotLayout {
    pub x: f32,
    pub y: f32,
    /// What the slot takes: item ids (`minecraft:redstone`) and item tags
    /// (`#c:dusts`). Empty = anything.
    #[serde(default)]
    pub accepts: Vec<String>,
}

impl SlotLayout {
    /// A slot at `(x, y)` taking anything.
    pub fn at(x: f32, y: f32) -> Self {
        Self { x, y, accepts: Vec::new() }
    }
}

/// Vanilla spacing between adjacent slots in the default grid.
pub const SLOT_SIZE: f32 = 18.0;

/// Default position of the player's main inventory (3×9) relative to the
/// panel's top-left corner — matches vanilla furnace/chest-style screens.
pub const DEFAULT_PLAYER_INV_OFFSET: (f32, f32) = (8.0, 84.0);
/// Extra vertical gap between the player's main inventory and their hotbar,
/// on top of the normal per-row `SLOT_SIZE` spacing (also a vanilla convention).
pub const PLAYER_INV_TO_HOTBAR_GAP: f32 = 4.0;
/// Columns of [`InventoryDef::default_grid`] (a vanilla container row).
const DEFAULT_GRID_COLS: usize = 9;
/// Top-left slot of [`InventoryDef::default_grid`] — leaves room for the
/// title above, like vanilla containers.
const DEFAULT_GRID_ORIGIN: (f32, f32) = (8.0, 18.0);

/// Describes one inventory-backed screen: how many slots a mod block has,
/// where they sit, whether the player's own inventory is appended below,
/// and which background texture to draw (vanilla default, or a mod's own).
#[derive(Debug, Clone)]
pub struct InventoryDef {
    pub id: String,
    pub slot_count: usize,
    /// Per-slot pixel positions. Empty = auto-generate a default grid (see
    /// [`InventoryDef::default_grid`]).
    pub layout: Vec<SlotLayout>,
    /// Appends the player's main inventory (3×9) + hotbar (9) below the
    /// custom slots — no armor, no offhand. Native vanilla slot rendering.
    pub include_player_inventory: bool,
    pub player_inv_offset: (f32, f32),
    /// `None` = default vanilla-style panel texture.
    pub background_texture: Option<String>,
    pub title: String,
    /// Screen size to center the container on — `None` uses the vanilla
    /// default (176×166). Set this when a custom `on_ui_render` overlay
    /// draws decoration at a different size, so the real vanilla `Slot`s
    /// (positioned by `layout`/`player_inv_offset` relative to the
    /// container's top-left corner) land under that decoration instead of
    /// the two disagreeing about where the top-left corner even is.
    pub background_size: Option<(f32, f32)>,
}

impl InventoryDef {
    pub fn new(id: impl Into<String>, slot_count: usize) -> Self {
        Self {
            id: id.into(),
            slot_count,
            layout: Vec::new(),
            include_player_inventory: true,
            player_inv_offset: DEFAULT_PLAYER_INV_OFFSET,
            background_texture: None,
            title: String::new(),
            background_size: None,
        }
    }

    /// Explicit per-slot pixel positions, overriding the default grid.
    pub fn layout(mut self, layout: Vec<SlotLayout>) -> Self {
        self.layout = layout;
        self
    }

    /// Remap the slot grid from a JSON array of `{"x":.., "y":..}` objects —
    /// one entry per slot, in slot-index order. Lets users/mod-packs override
    /// the layout without recompiling. Invalid or short JSON is ignored
    /// (falls back to whatever layout was set before, or the default grid).
    pub fn layout_from_json(mut self, json: &str) -> Self {
        if let Ok(parsed) = serde_json::from_str::<Vec<SlotLayout>>(json) {
            self.layout = parsed;
        }
        self
    }

    /// Whether the player's main inventory + hotbar (no armor/offhand) is
    /// appended below the custom slots. Default: `true`.
    pub fn include_player_inventory(mut self, v: bool) -> Self {
        self.include_player_inventory = v;
        self
    }

    pub fn player_inv_offset(mut self, x: f32, y: f32) -> Self {
        self.player_inv_offset = (x, y);
        self
    }

    /// Custom background texture (resource path); `None` keeps the default
    /// vanilla-style panel.
    pub fn background_texture(mut self, path: impl Into<String>) -> Self {
        self.background_texture = Some(path.into());
        self
    }

    /// Size (in GUI pixels) a custom `on_ui_render` overlay draws its
    /// decoration at — used to center the real vanilla container on the
    /// same footprint so its `Slot`s land under that decoration. Leave
    /// unset to keep the vanilla default 176×166 centering.
    pub fn background_size(mut self, w: f32, h: f32) -> Self {
        self.background_size = Some((w, h));
        self
    }

    pub fn title(mut self, title: impl Into<String>) -> Self {
        self.title = title.into();
        self
    }

    /// Resolve the effective slot layout: the explicit one if set, otherwise
    /// [`InventoryDef::default_grid`].
    pub fn resolved_layout(&self) -> Vec<SlotLayout> {
        if !self.layout.is_empty() {
            return self.layout.clone();
        }
        Self::default_grid(self.slot_count)
    }

    /// Default vanilla-style grid: up to 9 columns, 18px spacing, starting at
    /// (8, 18) — leaves room for a title above, matches vanilla containers.
    pub fn default_grid(slot_count: usize) -> Vec<SlotLayout> {
        let (x0, y0) = DEFAULT_GRID_ORIGIN;
        (0..slot_count)
            .map(|i| {
                let col = (i % DEFAULT_GRID_COLS) as f32;
                let row = (i / DEFAULT_GRID_COLS) as f32;
                SlotLayout::at(x0 + col * SLOT_SIZE, y0 + row * SLOT_SIZE)
            })
            .collect()
    }
}

/// Encode an [`InventoryDef`]'s slot layout as `"x:y,x:y:a|b,..."` — the
/// wire format used when handing the layout to the Java host (mirrors how
/// `BlockDef::connect_groups` is comma-joined for its ABI struct); a slot
/// that takes only some items adds them after a third `:`, `|`-joined.
pub fn encode_layout(layout: &[SlotLayout]) -> String {
    layout
        .iter()
        .map(|s| match s.accepts.is_empty() {
            true => format!("{}:{}", s.x, s.y),
            false => format!("{}:{}:{}", s.x, s.y, s.accepts.join("|")),
        })
        .collect::<Vec<_>>()
        .join(",")
}

/// Inverse of [`encode_layout`]. Malformed entries are skipped.
pub fn decode_layout(s: &str) -> Vec<SlotLayout> {
    if s.is_empty() {
        return Vec::new();
    }
    s.split(',')
        .filter_map(|entry| {
            let mut parts = entry.splitn(3, ':');
            let (x, y) = (parts.next()?, parts.next()?);
            let accepts = parts
                .next()
                .map(|a| a.split('|').filter(|s| !s.is_empty()).map(str::to_owned).collect())
                .unwrap_or_default();
            Some(SlotLayout {
                x: x.parse().ok()?,
                y: y.parse().ok()?,
                accepts,
            })
        })
        .collect()
}

// ── Client-side "currently open menu" snapshot ───────────────────────────────
//
// A mod that wants to decorate its own `yog-ui` widget tree with real slot
// contents (see `yog-ui`'s `inv_slot` widget — purely data-driven, it has no
// idea what "the currently open menu" even is) needs to read, on the client
// render thread, what's actually in that menu's slots right now. A plain
// Rust `static` cannot carry that across the mod/runtime boundary: the
// runtime and each mod's own dynamic library each get their own separate
// copy of any crate-level static, so writes on one side are invisible on
// the other (this is what broke the original design).
//
// Instead, the runtime resolves and calls `yog_inventory_set_snapshot` — an
// exported symbol every mod that depends on this crate carries automatically
// — once per frame, right before invoking `on_ui_render` handlers, handing
// over a fresh pointer to THIS mod's own copy of the `SNAPSHOT` static below.
// Resolved the same way the runtime already resolves `yog_mod_register` /
// `__yog_resolve_imports_final` on each loaded mod's library.

/// Capacity of [`YogInvSnapshotRaw::slots`] — covers the largest realistic
/// inventory screen (a mod's own slots + player main inventory + hotbar).
pub const MAX_SNAPSHOT_SLOTS: usize = 64;

/// One inventory slot's raw wire data for [`YogInvSnapshotRaw`].
#[repr(C)]
#[derive(Copy, Clone)]
pub struct YogInvSlotRaw {
    /// Empty (`len == 0`) if the slot itself is empty.
    pub item_id: YogStr,
    pub count: u32,
    /// Screen-space pixel position.
    pub x: i32,
    pub y: i32,
}

impl YogInvSlotRaw {
    pub const EMPTY: Self = Self {
        item_id: YogStr::EMPTY,
        count: 0,
        x: 0,
        y: 0,
    };
}

/// Raw per-frame snapshot of the currently-open inventory screen, built and
/// owned by the runtime, valid only for the duration of the render call that
/// hands it over.
#[repr(C)]
#[derive(Copy, Clone)]
pub struct YogInvSnapshotRaw {
    pub slot_count: u32,
    pub slots: [YogInvSlotRaw; MAX_SNAPSHOT_SLOTS],
}

impl YogInvSnapshotRaw {
    pub const EMPTY: Self = Self {
        slot_count: 0,
        slots: [YogInvSlotRaw::EMPTY; MAX_SNAPSHOT_SLOTS],
    };
}

static SNAPSHOT: AtomicPtr<YogInvSnapshotRaw> = AtomicPtr::new(std::ptr::null_mut());

/// Called by the runtime once per frame, before running `on_ui_render`
/// handlers, to refresh this mod's view of the currently-open inventory
/// screen. Not meant to be called by mod code directly.
#[doc(hidden)]
#[unsafe(no_mangle)]
pub extern "C" fn yog_inventory_set_snapshot(snapshot: *const YogInvSnapshotRaw) {
    SNAPSHOT.store(snapshot as *mut _, Ordering::Release);
}

/// One inventory slot's content, as of the last snapshot.
#[derive(Debug, Clone, Default)]
pub struct SlotView {
    /// `"namespace:item_id"` — empty if the slot is empty.
    pub item_id: String,
    pub count: u32,
    /// Screen-space pixel position.
    pub x: i32,
    pub y: i32,
}

/// The filled slots of the snapshot the runtime handed over this frame
/// (empty when no inventory screen is open).
fn snapshot_slots() -> &'static [YogInvSlotRaw] {
    let ptr = SNAPSHOT.load(Ordering::Acquire);
    // SAFETY: the runtime keeps the snapshot alive for the render call that
    // reads it, and only stores null or a valid pointer.
    match unsafe { ptr.as_ref() } {
        Some(snap) => &snap.slots[..(snap.slot_count as usize).min(MAX_SNAPSHOT_SLOTS)],
        None => &[],
    }
}

/// Number of slots in the currently-open inventory screen (0 if none is open).
pub fn current_slot_count() -> usize {
    snapshot_slots().len()
}

/// Slot `index`'s content right now, or `None` if out of range.
pub fn current_slot(index: usize) -> Option<SlotView> {
    let raw = snapshot_slots().get(index)?;
    let item_id = if raw.item_id.is_empty() {
        String::new()
    } else {
        unsafe { raw.item_id.as_str() }.to_owned()
    };
    Some(SlotView {
        item_id,
        count: raw.count,
        x: raw.x,
        y: raw.y,
    })
}

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

    #[test]
    fn default_grid_wraps_rows() {
        let g = InventoryDef::new("t", DEFAULT_GRID_COLS + 1).resolved_layout();
        assert_eq!(g[0], SlotLayout::at(8.0, 18.0));
        assert_eq!(g[DEFAULT_GRID_COLS], SlotLayout::at(8.0, 36.0));
    }

    #[test]
    fn layout_round_trips() {
        let l = vec![
            SlotLayout::at(1.5, 2.0),
            SlotLayout {
                accepts: vec!["minecraft:redstone".into(), "#c:dusts".into()],
                ..SlotLayout::at(30.0, 4.0)
            },
        ];
        assert_eq!(encode_layout(&l), "1.5:2,30:4:minecraft:redstone|#c:dusts");
        assert_eq!(decode_layout(&encode_layout(&l)), l);
        assert!(decode_layout("").is_empty());
        assert_eq!(
            decode_layout("1:2,bad,3"),
            vec![SlotLayout::at(1.0, 2.0)]
        );
    }

    #[test]
    fn no_snapshot_means_no_slots() {
        assert_eq!(current_slot_count(), 0);
        assert!(current_slot(0).is_none());
    }
}