ghast-inventory 0.2.3

//! Item stacks: one version-independent type over the 1.8 (`slot::legacy`) and 1.16.5
//! (`slot::modern`) wire formats.
//!
//! NBT stays raw ([`RawNbt`]): converting a `window_items` packet into stacks only moves the
//! reference-counted bytes. Comparisons compare the raw bytes first and parse only when the bytes
//! differ (vanilla compares NBT trees, which ignore compound key order and the root name).

use ghast_protocol::nbt::{RawNbt, Tag};
use ghast_protocol::types::slot::{legacy, modern};

/// A non-empty item stack as the client holds it.
///
/// `count` is a Java `int` in vanilla (sent as a byte). 1.8 keeps stacks with a count of zero
/// or less as real stacks (they render as a red "0"); 1.16.5 treats them as empty, so a 1.16.5
/// [`Inventory`](crate::Inventory) never stores one.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct Stack {
    /// Numeric item id (1.8: legacy id; 1.16.5: item registry id).
    pub id: i32,
    /// Stack size.
    pub count: i32,
    /// 1.8 damage / metadata. Always 0 on 1.16.5 (damage lives in the `Damage` NBT tag).
    pub damage: i16,
    /// Item NBT exactly as received, if any.
    pub nbt: Option<RawNbt>,
}

impl Stack {
    /// A stack without NBT.
    #[must_use]
    pub fn new(id: i32, count: i32, damage: i16) -> Stack {
        Stack {
            id,
            count,
            damage,
            nbt: None,
        }
    }

    /// The same item (id, damage, NBT) with another count.
    #[must_use]
    pub fn with_count(&self, count: i32) -> Stack {
        Stack {
            count,
            ..self.clone()
        }
    }

    /// Converts a 1.8 wire stack.
    #[must_use]
    pub fn from_legacy(s: legacy::ItemStack) -> Stack {
        Stack {
            id: i32::from(s.id),
            count: i32::from(s.count),
            damage: s.damage,
            nbt: s.nbt,
        }
    }

    /// Converts a 1.16.5 wire stack.
    #[must_use]
    pub fn from_modern(s: modern::ItemStack) -> Stack {
        Stack {
            id: s.id,
            count: i32::from(s.count),
            damage: 0,
            nbt: s.nbt,
        }
    }

    /// The 1.8 wire form (count truncated to a byte like Java's `writeByte`).
    #[must_use]
    pub fn to_legacy(&self) -> legacy::ItemStack {
        legacy::ItemStack {
            // An id outside i16 cannot come from a 1.8 server; -1 would encode "empty".
            id: i16::try_from(self.id)
                .ok()
                .filter(|&i| i != -1)
                .unwrap_or(0),
            count: self.count as i8,
            damage: self.damage,
            nbt: self.nbt.clone(),
        }
    }

    /// The 1.16.5 wire form.
    #[must_use]
    pub fn to_modern(&self) -> modern::ItemStack {
        modern::ItemStack {
            id: self.id,
            count: self.count as i8,
            nbt: self.nbt.clone(),
        }
    }

    /// Same item, damage and NBT (vanilla's item + damage check and its NBT check); counts are
    /// not compared.
    #[must_use]
    pub fn same_item(&self, other: &Stack) -> bool {
        self.id == other.id && self.damage == other.damage && self.nbt_eq(other)
    }

    /// Vanilla's tag comparison: both absent, or both present and equal as trees.
    #[must_use]
    pub fn nbt_eq(&self, other: &Stack) -> bool {
        nbt_eq(self.nbt.as_ref(), other.nbt.as_ref())
    }

    /// Exact equality as the server checks the clicked item (count, id, damage, NBT).
    #[must_use]
    pub fn equals_exact(&self, other: &Stack) -> bool {
        self.count == other.count && self.same_item(other)
    }

    /// `getBoolean(key)` of the root compound: a numeric tag whose byte value is not zero.
    pub(crate) fn nbt_bool(&self, key: &str) -> bool {
        self.nbt_number(key).is_some_and(|v| v as i8 != 0)
    }

    /// `getInt(key)` of the root compound (0 when absent or not numeric).
    pub(crate) fn nbt_int(&self, key: &str) -> i32 {
        self.nbt_number(key).unwrap_or(0) as i32
    }

    fn nbt_number(&self, key: &str) -> Option<i64> {
        let tree = self.nbt.as_ref()?.parse().ok()??;
        let c = tree.tag.as_compound()?;
        number(last(c, key)?)
    }

    /// 1.16.5 `EnchantmentHelper.hasBindingCurse`: an `Enchantments` entry with id
    /// `minecraft:binding_curse` and `lvl` > 0.
    pub(crate) fn has_binding_curse(&self) -> bool {
        let Some(Ok(Some(tree))) = self.nbt.as_ref().map(RawNbt::parse) else {
            return false;
        };
        let Some(Tag::List(list)) = tree.tag.as_compound().and_then(|c| last(c, "Enchantments"))
        else {
            return false;
        };
        for e in &list.items {
            let Tag::Compound(e) = e else { return false };
            let id = match last(e, "id") {
                Some(Tag::String(s)) => s.as_str(),
                _ => "",
            };
            if id == "minecraft:binding_curse" || id == "binding_curse" {
                // getLevel returns the first matching entry, clamped to 0..=255.
                return last(e, "lvl").and_then(number).unwrap_or(0) as i32 > 0;
            }
        }
        false
    }
}

/// The value of the last entry named `key` (a Java `HashMap` keeps the last duplicate).
fn last<'a>(c: &'a ghast_protocol::nbt::Compound, key: &str) -> Option<&'a Tag> {
    c.0.iter().rev().find(|(k, _)| k == key).map(|(_, v)| v)
}

fn number(t: &Tag) -> Option<i64> {
    Some(match *t {
        Tag::Byte(v) => i64::from(v),
        Tag::Short(v) => i64::from(v),
        Tag::Int(v) => i64::from(v),
        Tag::Long(v) => v,
        // NbtFloat/NbtDouble int and byte values are `MathHelper.floor(value)` (then `& 0xFF`).
        Tag::Float(v) => {
            let i = v as i32; // Java (int): saturating, NaN -> 0
            i64::from(if v < i as f32 { i - 1 } else { i })
        }
        Tag::Double(v) => {
            let i = v as i32;
            i64::from(if v < f64::from(i) { i - 1 } else { i })
        }
        _ => return None,
    })
}

/// Vanilla tag equality on raw NBT: equal bytes are equal; otherwise both trees are parsed and
/// compared (compounds as maps, root names ignored). Unparsable NBT only equals itself.
#[must_use]
pub fn nbt_eq(a: Option<&RawNbt>, b: Option<&RawNbt>) -> bool {
    match (a, b) {
        (None, None) => true,
        (Some(a), Some(b)) => {
            if a.as_bytes() == b.as_bytes() {
                return true;
            }
            match (a.parse(), b.parse()) {
                (Ok(Some(x)), Ok(Some(y))) => tag_eq(&x.tag, &y.tag),
                (Ok(None), Ok(None)) => true,
                _ => false,
            }
        }
        _ => false,
    }
}

fn tag_eq(a: &Tag, b: &Tag) -> bool {
    match (a, b) {
        (Tag::Compound(x), Tag::Compound(y)) => {
            // Map semantics: the last value of each key, same key set.
            let distinct = |c: &ghast_protocol::nbt::Compound| {
                c.0.iter()
                    .enumerate()
                    .filter(|(i, (k, _))| !c.0[i + 1..].iter().any(|(k2, _)| k2 == k))
                    .count()
            };
            if distinct(x) != distinct(y) {
                return false;
            }
            x.0.iter().enumerate().all(|(i, (k, v))| {
                if x.0[i + 1..].iter().any(|(k2, _)| k2 == k) {
                    return true; // a later duplicate decides
                }
                last(y, k).is_some_and(|w| tag_eq(v, w))
            })
        }
        (Tag::List(x), Tag::List(y)) => {
            x.elem_type == y.elem_type
                && x.items.len() == y.items.len()
                && x.items.iter().zip(&y.items).all(|(v, w)| tag_eq(v, w))
        }
        // Java `==` on float/double values: NaN != NaN, 0.0 == -0.0.
        (Tag::Float(x), Tag::Float(y)) => x == y,
        (Tag::Double(x), Tag::Double(y)) => x == y,
        _ => a == b,
    }
}

/// `Option<&Stack>` exact equality (the server's `ItemStack.equalsAll`).
#[must_use]
pub fn stacks_equal(a: Option<&Stack>, b: Option<&Stack>) -> bool {
    match (a, b) {
        (None, None) => true,
        (Some(a), Some(b)) => a.equals_exact(b),
        _ => false,
    }
}

/// Converts a 1.8 wire slot.
#[must_use]
pub fn from_legacy_slot(s: legacy::Slot) -> Option<Stack> {
    s.0.map(Stack::from_legacy)
}

/// Converts a 1.16.5 wire slot; stacks that vanilla treats as empty (air, count <= 0) are `None`.
#[must_use]
pub fn from_modern_slot(s: modern::Slot) -> Option<Stack> {
    s.0.map(Stack::from_modern)
        .filter(|s| s.id != 0 && s.count > 0)
}

/// The 1.8 wire slot of an optional stack.
#[must_use]
pub fn to_legacy_slot(s: Option<&Stack>) -> legacy::Slot {
    legacy::Slot(s.map(Stack::to_legacy))
}

/// The 1.16.5 wire slot of an optional stack.
#[must_use]
pub fn to_modern_slot(s: Option<&Stack>) -> modern::Slot {
    modern::Slot(s.map(Stack::to_modern))
}

#[cfg(test)]
mod tests {
    use super::*;
    use bytes::Bytes;
    use ghast_protocol::nbt::{Compound, NamedTag};

    fn raw(entries: Vec<(&str, Tag)>, root: &str) -> RawNbt {
        RawNbt::from_named(&NamedTag {
            name: root.into(),
            tag: Tag::Compound(Compound(
                entries
                    .into_iter()
                    .map(|(k, v)| (k.to_string(), v))
                    .collect(),
            )),
        })
        .unwrap()
    }

    #[test]
    fn nbt_equality_is_tree_equality() {
        let a = raw(vec![("a", Tag::Int(1)), ("b", Tag::Byte(2))], "");
        let b = raw(vec![("b", Tag::Byte(2)), ("a", Tag::Int(1))], "");
        let c = raw(vec![("a", Tag::Int(1)), ("b", Tag::Byte(3))], "");
        let d = raw(vec![("a", Tag::Int(1)), ("b", Tag::Byte(2))], "root");
        assert!(nbt_eq(Some(&a), Some(&a)));
        assert!(nbt_eq(Some(&a), Some(&b)));
        assert!(!nbt_eq(Some(&a), Some(&c)));
        assert!(nbt_eq(Some(&a), Some(&d)));
        assert!(!nbt_eq(Some(&a), None));
        let empty = raw(vec![], "");
        assert!(!nbt_eq(Some(&empty), None));
        let dup = raw(
            vec![("a", Tag::Int(5)), ("a", Tag::Int(1)), ("b", Tag::Byte(2))],
            "",
        );
        assert!(nbt_eq(Some(&a), Some(&dup)));
        // Java float `==`: NaN is never equal (only reached when the bytes differ).
        let nan = raw(vec![("f", Tag::Float(f32::NAN)), ("g", Tag::Byte(0))], "");
        let nan_reordered = raw(vec![("g", Tag::Byte(0)), ("f", Tag::Float(f32::NAN))], "");
        assert!(!nbt_eq(Some(&nan), Some(&nan_reordered)));
    }

    #[test]
    fn nbt_helpers() {
        let mut s = Stack::new(1, 1, 0);
        assert!(!s.nbt_bool("Unbreakable"));
        s.nbt = Some(raw(
            vec![("Unbreakable", Tag::Byte(1)), ("Damage", Tag::Int(7))],
            "",
        ));
        assert!(s.nbt_bool("Unbreakable"));
        assert_eq!(s.nbt_int("Damage"), 7);
        s.nbt = Some(raw(vec![("Unbreakable", Tag::Int(256))], ""));
        assert!(!s.nbt_bool("Unbreakable"), "(byte) 256 == 0");
        let ench = |id: &str, lvl: i16| {
            Tag::List(ghast_protocol::nbt::List {
                elem_type: 10,
                items: vec![Tag::Compound(Compound(vec![
                    ("id".into(), Tag::String(id.into())),
                    ("lvl".into(), Tag::Short(lvl)),
                ]))],
            })
        };
        s.nbt = Some(raw(
            vec![("Enchantments", ench("minecraft:binding_curse", 1))],
            "",
        ));
        assert!(s.has_binding_curse());
        s.nbt = Some(raw(
            vec![("Enchantments", ench("minecraft:binding_curse", 0))],
            "",
        ));
        assert!(!s.has_binding_curse());
        s.nbt = Some(raw(
            vec![("StoredEnchantments", ench("minecraft:binding_curse", 1))],
            "",
        ));
        assert!(!s.has_binding_curse());
        // Garbage NBT never panics.
        s.nbt = RawNbt::from_bytes(Bytes::from_static(&[0x0a, 0, 0, 0])).ok();
        assert!(!s.has_binding_curse());
    }

    #[test]
    fn wire_round_trip() {
        let s = Stack::new(276, 1, 5);
        assert_eq!(Stack::from_legacy(s.to_legacy()), s);
        let m = Stack::new(600, 64, 0);
        assert_eq!(Stack::from_modern(m.to_modern()), m);
        assert_eq!(
            from_modern_slot(modern::Slot(Some(modern::ItemStack {
                id: 1,
                count: 0,
                nbt: None
            }))),
            None
        );
        assert_eq!(
            from_modern_slot(modern::Slot(Some(modern::ItemStack {
                id: 0,
                count: 5,
                nbt: None
            }))),
            None
        );
        assert!(
            from_legacy_slot(legacy::Slot(Some(legacy::ItemStack {
                id: 1,
                count: 0,
                damage: 0,
                nbt: None
            })))
            .is_some()
        );
        assert_eq!(Stack::new(1, 300, 0).to_legacy().count, 44);
    }
}