photocraft/crates/psd/src/slices.rs

//! Slices image resource (id 1050), from the Adobe Photoshop File Format Specification.
//!
//! Version 6 is a fixed binary layout (bounding rect, group name, then per slice: ids, origin,
//! optional layer id, name, type, rect, URL / target / message / alt strings, cell text and
//! alignment, background colour), optionally followed by a versioned descriptor carrying extra
//! per-slice data (layer-slice outsets). Versions 7 and 8 store everything as one versioned
//! descriptor (`baseName`, `bounds`, `slices` list).
//!
//! [`SlicesResource::to_bytes`] writes version 6, the documented binary layout every Photoshop
//! version reads. Unknown fields are not kept here; callers that need a byte-exact round trip
//! keep the raw resource while the slices are unchanged.

use crate::descriptor::{Descriptor, Id, UnicodeString, Value, VersionedDescriptor};
use crate::error::{PsdError, Result};
use crate::io::{Reader, WriteExt};

/// Resource id of the slices resource.
pub const SLICES: u16 = 1050;

/// One slice record.
#[derive(Debug, Clone, PartialEq, Eq, Default)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct SliceRecord {
    /// Slice id.
    pub id: u32,
    /// Group id.
    pub group_id: u32,
    /// Origin: 0 auto-generated, 1 layer-based, 2 user-drawn.
    pub origin: u32,
    /// Layer id of a layer-based slice (the layer record's `lyid`).
    pub layer_id: Option<u32>,
    /// Slice name.
    pub name: String,
    /// Type: 0 no image, 1 image, 2 table.
    pub kind: u32,
    /// Left, top, right, bottom in document pixels.
    pub rect: [i32; 4],
    /// URL.
    pub url: String,
    /// Target frame.
    pub target: String,
    /// Status-bar message.
    pub message: String,
    /// Alt tag.
    pub alt: String,
    /// Cell text is HTML.
    pub cell_text_is_html: bool,
    /// Cell text.
    pub cell_text: String,
    /// Horizontal alignment.
    pub horizontal_align: u32,
    /// Vertical alignment.
    pub vertical_align: u32,
    /// Background colour as alpha, red, green, blue.
    pub color: [u8; 4],
    /// Layer-based slice outsets: top, left, bottom, right.
    pub outsets: [i32; 4],
}

/// The whole slices resource.
#[derive(Debug, Clone, PartialEq, Eq, Default)]
#[cfg_attr(feature = "serde", derive(serde::Serialize, serde::Deserialize))]
pub struct SlicesResource {
    /// Version read (6, 7 or 8); writing always produces 6.
    pub version: u32,
    /// Bounding rectangle of all slices: top, left, bottom, right.
    pub bounds: [i32; 4],
    /// Name of the slice group (the base name).
    pub group_name: String,
    /// Slices, including auto-generated ones as Photoshop saves them.
    pub slices: Vec<SliceRecord>,
}

fn ustr(r: &mut Reader<'_>) -> Result<String> {
    Ok(UnicodeString::read(r)?.to_string_lossy())
}

fn put_ustr(out: &mut Vec<u8>, s: &str) {
    UnicodeString::new(s).write(out);
}

// ---------- descriptor helpers (versions 7/8 and the v6 tail) ----------

/// A number as `i64`; float casts saturate (NaN reads as 0).
fn d_int(d: &Descriptor, key: &str) -> Option<i64> {
    match d.get(key)? {
        Value::Integer(v) => Some(i64::from(*v)),
        Value::LargeInteger(v) => Some(*v),
        Value::Double(v) => Some(*v as i64),
        Value::UnitFloat { value, .. } => Some(*value as i64),
        _ => None,
    }
}

/// A coordinate, clamped to the `i32` range instead of wrapping.
fn d_i32(d: &Descriptor, key: &str) -> Option<i32> {
    d_int(d, key).map(|v| v.clamp(i64::from(i32::MIN), i64::from(i32::MAX)) as i32)
}

/// An id. A 32-bit `long` holds the id's bits (ids past `i32::MAX` are written negative); any
/// other number outside the `u32` range is no id at all rather than a wrapped one.
fn d_u32(d: &Descriptor, key: &str) -> Option<u32> {
    match d.get(key)? {
        Value::Integer(v) => Some(*v as u32),
        _ => u32::try_from(d_int(d, key)?).ok(),
    }
}

fn d_text(d: &Descriptor, key: &str) -> String {
    match d.get(key) {
        Some(Value::Text(t)) => t.to_string_lossy(),
        _ => String::new(),
    }
}

fn d_enum(d: &Descriptor, key: &str) -> Option<String> {
    match d.get(key)? {
        Value::Enumerated { value, .. } => Some(String::from_utf8_lossy(value.as_bytes()).into_owned()),
        _ => None,
    }
}

fn d_bool(d: &Descriptor, key: &str) -> bool {
    matches!(d.get(key), Some(Value::Boolean(true)))
}

fn d_bounds(d: &Descriptor, key: &str) -> Option<[i32; 4]> {
    let Value::Descriptor(b) = d.get(key)? else { return None };
    let g = |k: &str| d_i32(b, k).unwrap_or(0);
    // top, left, bottom, right
    Some([g("Top "), g("Left"), g("Btom"), g("Rght")])
}

fn origin_from(s: &str) -> u32 {
    match s {
        "autoGenerated" => 0,
        "layerGenerated" | "layer" => 1,
        _ => 2,
    }
}

fn kind_from(s: &str) -> u32 {
    match s {
        "noImage" => 0,
        "Tbl " | "table" => 2,
        _ => 1,
    }
}

fn slice_from_descriptor(d: &Descriptor) -> SliceRecord {
    let b = d_bounds(d, "bounds").unwrap_or_default();
    let color = match (d_enum(d, "bgColorType").as_deref(), d.get("bgColor")) {
        (Some("Clr "), Some(Value::Descriptor(c))) => {
            let g = |k: &str| d_int(c, k).unwrap_or(0).clamp(0, 255) as u8;
            let a = if c.get("alpha").is_some() { g("alpha") } else { 255 };
            [a, g("Rd  "), g("Grn "), g("Bl  ")]
        }
        _ => [0; 4],
    };
    SliceRecord {
        id: d_u32(d, "sliceID").unwrap_or(0),
        group_id: d_u32(d, "groupID").unwrap_or(0),
        origin: d_enum(d, "origin").map_or(2, |s| origin_from(&s)),
        layer_id: d_u32(d, "layerID"),
        name: d_text(d, "Nm  "),
        kind: d_enum(d, "Type").map_or(1, |s| kind_from(&s)),
        // Descriptor bounds are top/left/bottom/right; records use left/top/right/bottom.
        rect: [b[1], b[0], b[3], b[2]],
        url: d_text(d, "url"),
        target: d_text(d, "null"),
        message: d_text(d, "Msge"),
        alt: d_text(d, "altTag"),
        cell_text_is_html: d_bool(d, "cellTextIsHTML"),
        cell_text: d_text(d, "cellText"),
        horizontal_align: 0,
        vertical_align: 0,
        color,
        outsets: [
            d_i32(d, "topOutset").unwrap_or(0),
            d_i32(d, "leftOutset").unwrap_or(0),
            d_i32(d, "bottomOutset").unwrap_or(0),
            d_i32(d, "rightOutset").unwrap_or(0),
        ],
    }
}

fn bounds_descriptor(tlbr: [i32; 4]) -> Value {
    Value::Descriptor(
        Descriptor::new("Rct1")
            .with("Top ", Value::Integer(tlbr[0]))
            .with("Left", Value::Integer(tlbr[1]))
            .with("Btom", Value::Integer(tlbr[2]))
            .with("Rght", Value::Integer(tlbr[3])),
    )
}

fn enumerated(ty: &str, v: &str) -> Value {
    Value::Enumerated { type_id: Id::new(ty), value: Id::new(v) }
}

impl SlicesResource {
    /// Parses resource data (versions 6, 7 and 8).
    pub fn from_bytes(data: &[u8]) -> Result<Self> {
        let mut r = Reader::new(data);
        let version = r.u32()?;
        match version {
            6 => Self::read_v6(&mut r),
            7 | 8 => {
                let vd = VersionedDescriptor::read(&mut r)?;
                let d = &vd.descriptor;
                let slices = match d.get("slices") {
                    Some(Value::List(items)) => items
                        .iter()
                        .filter_map(|v| match v {
                            Value::Descriptor(s) => Some(slice_from_descriptor(s)),
                            _ => None,
                        })
                        .collect(),
                    _ => Vec::new(),
                };
                Ok(SlicesResource { version, bounds: d_bounds(d, "bounds").unwrap_or_default(), group_name: d_text(d, "baseName"), slices })
            }
            v => Err(PsdError::invalid(format!("unsupported slices resource version {v}"))),
        }
    }

    fn read_v6(r: &mut Reader<'_>) -> Result<Self> {
        let bounds = [r.i32()?, r.i32()?, r.i32()?, r.i32()?];
        let group_name = ustr(r)?;
        let n = r.u32()? as usize;
        if n > r.remaining() / 16 {
            return Err(PsdError::invalid("slice count exceeds the resource size"));
        }
        let mut slices = Vec::with_capacity(n);
        for _ in 0..n {
            let id = r.u32()?;
            let group_id = r.u32()?;
            let origin = r.u32()?;
            let layer_id = if origin == 1 { Some(r.u32()?) } else { None };
            let name = ustr(r)?;
            let kind = r.u32()?;
            let rect = [r.i32()?, r.i32()?, r.i32()?, r.i32()?];
            let url = ustr(r)?;
            let target = ustr(r)?;
            let message = ustr(r)?;
            let alt = ustr(r)?;
            let cell_text_is_html = r.u8()? != 0;
            let cell_text = ustr(r)?;
            let horizontal_align = r.u32()?;
            let vertical_align = r.u32()?;
            let color = [r.u8()?, r.u8()?, r.u8()?, r.u8()?];
            slices.push(SliceRecord {
                id,
                group_id,
                origin,
                layer_id,
                name,
                kind,
                rect,
                url,
                target,
                message,
                alt,
                cell_text_is_html,
                cell_text,
                horizontal_align,
                vertical_align,
                color,
                outsets: [0; 4],
            });
        }
        // Optional trailing descriptor (Photoshop 7+): per-slice extras such as outsets.
        if r.remaining() >= 4
            && let Ok(vd) = VersionedDescriptor::read(r)
            && let Some(Value::List(items)) = vd.descriptor.get("slices")
        {
            for v in items {
                let Value::Descriptor(d) = v else { continue };
                // An entry without a usable id belongs to no slice (not to slice 0).
                let Some(id) = d_u32(d, "sliceID") else { continue };
                let extra = slice_from_descriptor(d);
                if let Some(s) = slices.iter_mut().find(|s| s.id == id) {
                    s.outsets = extra.outsets;
                }
            }
        }
        Ok(SlicesResource { version: 6, bounds, group_name, slices })
    }

    /// Serializes as version 6. A trailing descriptor with the outsets is added when any slice
    /// has them, the way Photoshop extends the version 6 layout.
    pub fn to_bytes(&self) -> Vec<u8> {
        let mut out = Vec::new();
        out.put_u32(6);
        for v in self.bounds {
            out.put_i32(v);
        }
        put_ustr(&mut out, &self.group_name);
        out.put_u32(self.slices.len() as u32);
        for s in &self.slices {
            out.put_u32(s.id);
            out.put_u32(s.group_id);
            out.put_u32(s.origin);
            if s.origin == 1 {
                out.put_u32(s.layer_id.unwrap_or(0));
            }
            put_ustr(&mut out, &s.name);
            out.put_u32(s.kind);
            for v in s.rect {
                out.put_i32(v);
            }
            put_ustr(&mut out, &s.url);
            put_ustr(&mut out, &s.target);
            put_ustr(&mut out, &s.message);
            put_ustr(&mut out, &s.alt);
            out.put_u8(u8::from(s.cell_text_is_html));
            put_ustr(&mut out, &s.cell_text);
            out.put_u32(s.horizontal_align);
            out.put_u32(s.vertical_align);
            out.put(&s.color);
        }
        if self.slices.iter().any(|s| s.outsets != [0; 4]) {
            let list = self
                .slices
                .iter()
                .map(|s| {
                    Value::Descriptor(
                        Descriptor::new("slice")
                            .with("sliceID", Value::Integer(s.id as i32))
                            .with("topOutset", Value::Integer(s.outsets[0]))
                            .with("leftOutset", Value::Integer(s.outsets[1]))
                            .with("bottomOutset", Value::Integer(s.outsets[2]))
                            .with("rightOutset", Value::Integer(s.outsets[3])),
                    )
                })
                .collect();
            VersionedDescriptor::new(Descriptor::new("null").with("slices", Value::List(list))).write(&mut out);
        }
        out
    }

    /// Serializes in the version 7 descriptor form (what newer Photoshop versions write).
    pub fn to_descriptor_bytes(&self) -> Vec<u8> {
        let list = self
            .slices
            .iter()
            .map(|s| {
                let origin = match s.origin {
                    0 => "autoGenerated",
                    1 => "layerGenerated",
                    _ => "userGenerated",
                };
                let kind = match s.kind {
                    0 => "noImage",
                    2 => "Tbl ",
                    _ => "Img ",
                };
                let mut d = Descriptor::new("slice")
                    .with("sliceID", Value::Integer(s.id as i32))
                    .with("groupID", Value::Integer(s.group_id as i32))
                    .with("origin", enumerated("ESliceOrigin", origin));
                if let Some(l) = s.layer_id.filter(|_| s.origin == 1) {
                    d = d.with("layerID", Value::Integer(l as i32));
                }
                d.with("Nm  ", Value::Text(UnicodeString::new(&s.name)))
                    .with("Type", enumerated("ESliceType", kind))
                    .with("bounds", bounds_descriptor([s.rect[1], s.rect[0], s.rect[3], s.rect[2]]))
                    .with("url", Value::Text(UnicodeString::new(&s.url)))
                    .with("null", Value::Text(UnicodeString::new(&s.target)))
                    .with("Msge", Value::Text(UnicodeString::new(&s.message)))
                    .with("altTag", Value::Text(UnicodeString::new(&s.alt)))
                    .with("cellTextIsHTML", Value::Boolean(s.cell_text_is_html))
                    .with("cellText", Value::Text(UnicodeString::new(&s.cell_text)))
                    .with("horzAlign", enumerated("ESliceHorzAlign", "default"))
                    .with("vertAlign", enumerated("ESliceVertAlign", "default"))
                    .with("bgColorType", enumerated("ESliceBGColorType", "None"))
                    .with("topOutset", Value::Integer(s.outsets[0]))
                    .with("leftOutset", Value::Integer(s.outsets[1]))
                    .with("bottomOutset", Value::Integer(s.outsets[2]))
                    .with("rightOutset", Value::Integer(s.outsets[3]))
            })
            .map(Value::Descriptor)
            .collect();
        let d = Descriptor::new("null")
            .with("bounds", bounds_descriptor(self.bounds))
            .with("slices", Value::List(list))
            .with("baseName", Value::Text(UnicodeString::new(&self.group_name)));
        let mut out = Vec::new();
        out.put_u32(7);
        VersionedDescriptor::new(d).write(&mut out);
        out
    }
}

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

    fn sample() -> SlicesResource {
        SlicesResource {
            version: 6,
            bounds: [0, 0, 80, 100],
            group_name: "site".into(),
            slices: vec![
                SliceRecord { id: 0, origin: 0, kind: 1, rect: [0, 0, 100, 10], ..Default::default() },
                SliceRecord {
                    id: 1,
                    group_id: 0,
                    origin: 2,
                    name: "logo".into(),
                    kind: 1,
                    rect: [20, 10, 60, 30],
                    url: "https://example.org/".into(),
                    target: "_blank".into(),
                    message: "hi".into(),
                    alt: "Logo".into(),
                    cell_text_is_html: true,
                    cell_text: "<b>x</b>".into(),
                    horizontal_align: 1,
                    vertical_align: 2,
                    color: [255, 10, 20, 30],
                    ..Default::default()
                },
                SliceRecord { id: 2, origin: 1, layer_id: Some(7), kind: 0, rect: [5, 40, 25, 70], outsets: [1, 2, 3, 4], ..Default::default() },
            ],
        }
    }

    #[test]
    fn v6_roundtrips() {
        let s = sample();
        let bytes = s.to_bytes();
        let back = SlicesResource::from_bytes(&bytes).unwrap();
        assert_eq!(back, s);
        assert_eq!(back.to_bytes(), bytes, "byte-stable");
    }

    #[test]
    fn v7_descriptor_parses() {
        let s = sample();
        let back = SlicesResource::from_bytes(&s.to_descriptor_bytes()).unwrap();
        assert_eq!(back.version, 7);
        assert_eq!(back.group_name, "site");
        assert_eq!(back.bounds, s.bounds);
        assert_eq!(back.slices.len(), 3);
        assert_eq!(back.slices[1].rect, [20, 10, 60, 30]);
        assert_eq!(back.slices[1].alt, "Logo");
        assert_eq!(back.slices[1].target, "_blank");
        assert_eq!(back.slices[2].origin, 1);
        assert_eq!(back.slices[2].layer_id, Some(7));
        assert_eq!(back.slices[2].kind, 0);
        assert_eq!(back.slices[2].outsets, [1, 2, 3, 4]);
    }

    #[test]
    fn out_of_range_descriptor_numbers_do_not_wrap() {
        // sliceID 2^32+1 used to read as slice 1 and take that slice's outsets.
        let wide = |key: &str| Descriptor::new("slice").with("sliceID", Value::LargeInteger((1 << 32) + 1)).with(key, Value::Integer(9));
        let mut plain = sample();
        for s in &mut plain.slices {
            s.outsets = [0; 4];
        }
        let mut bytes = plain.to_bytes();
        VersionedDescriptor::new(Descriptor::new("null").with("slices", Value::List(vec![Value::Descriptor(wide("topOutset"))]))).write(&mut bytes);
        let back = SlicesResource::from_bytes(&bytes).unwrap();
        assert!(back.slices.iter().all(|s| s.outsets == [0; 4]), "{:?}", back.slices);

        // Descriptor form: ids out of the u32 range fall back to 0, coordinates clamp.
        let d = wide("leftOutset")
            .with("layerID", Value::LargeInteger(-1))
            .with("bottomOutset", Value::LargeInteger(1 << 40))
            .with("rightOutset", Value::Double(-1e12))
            .with("bounds", Value::Descriptor(Descriptor::new("Rct1").with("Top ", Value::LargeInteger((1 << 32) + 5))));
        let s = slice_from_descriptor(&d);
        assert_eq!((s.id, s.layer_id), (0, None));
        assert_eq!(s.outsets, [0, 9, i32::MAX, i32::MIN]);
        assert_eq!(s.rect[1], i32::MAX);
        // A 32-bit long keeps the id's bits, as `to_descriptor_bytes` writes ids past i32::MAX.
        assert_eq!(slice_from_descriptor(&Descriptor::new("slice").with("sliceID", Value::Integer(-1))).id, u32::MAX);
    }

    #[test]
    fn malformed_input_is_an_error() {
        let bytes = sample().to_bytes();
        // Cuts inside the records; a damaged trailing descriptor is ignored on purpose.
        for cut in [0, 3, 10, 30, 120] {
            assert!(SlicesResource::from_bytes(&bytes[..cut]).is_err(), "cut at {cut}");
        }
        let mut huge = 6u32.to_be_bytes().to_vec();
        huge.extend([0u8; 16]);
        huge.extend(0u32.to_be_bytes());
        huge.extend(u32::MAX.to_be_bytes());
        assert!(SlicesResource::from_bytes(&huge).is_err());
        assert!(SlicesResource::from_bytes(&9u32.to_be_bytes()).is_err());
    }
}