concinnity-dev 0.19.23

// src/editor/overrides/prefab_map.rs
//
// Mapping between a prefab-generated asset's fields and the Prefab definition
// entry that produced them, including the inverse of the instance-transform
// composition the expansion applies. Pure: the hook owns the entry mutations.

use concinnity_core::math::vec3::add;
use serde_json::Value;

// Where a generated asset's template lives: an entry inside an authored Prefab
// definition, plus the accumulated transform of its parent frame (the Prop
// instance composed through any nested prefab entries).
#[derive(Debug, Clone, PartialEq)]
pub(crate) struct TemplateSlot {
    pub def_name: String,
    // Index of the definition line in the working entries.
    pub def_index: usize,
    // Index of the entry in the definition's `props` array.
    pub entry_index: usize,
    pub parent: Frame,
}

// A composed transform frame (a Prop instance's, threaded through nested
// prefab entries).
#[derive(Debug, Clone, Copy, PartialEq)]
pub(crate) struct Frame {
    pub pos: [f32; 3],
    pub rot: [f32; 3],
    pub scale: [f32; 3],
}

// How one instance arg writes back into a prefab entry.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub(crate) enum FieldMap {
    // Same value under this entry key (dotted sub-paths preserved).
    Direct(&'static str),
    // Composed with the parent transform; written back through its inverse.
    Position,
    Rotation,
    Scale,
}

// Resolve the prefab entry behind the generated asset `asset_name`, produced
// by the Prop instance `generated_by`. Walks nested prefab chains by the
// `<instance>_<entry>` naming the expansion uses; every definition along the
// chain must be an authored line (a disk preset cannot be edited here).
pub(crate) fn resolve(
    entries: &[Value],
    generated_by: &str,
    asset_name: &str,
) -> Result<TemplateSlot, String> {
    let instance = entries
        .iter()
        .find(|e| entry_name(e) == generated_by && type_norm(e) == "prop")
        .ok_or_else(|| format!("no Prop instance named '{generated_by}'"))?;
    let args = instance.get("args").cloned().unwrap_or(Value::Null);
    let prefab_ref = args
        .get("prefab")
        .and_then(|v| v.as_str())
        .filter(|r| !r.is_empty())
        .ok_or_else(|| format!("'{generated_by}' is not a prefab instance"))?;
    let suffix = asset_name
        .strip_prefix(&format!("{generated_by}_"))
        .ok_or_else(|| format!("'{asset_name}' was not generated by '{generated_by}'"))?;

    let mut matches: Vec<TemplateSlot> = Vec::new();
    let frame = Frame {
        pos: f32_arr3(&args, "position", [0.0; 3]),
        rot: f32_arr3(&args, "rotation_deg", [0.0; 3]),
        scale: f32_arr3(&args, "scale", [1.0; 3]),
    };
    walk(entries, prefab_ref, suffix, frame, &mut matches)?;
    match matches.len() {
        0 => Err(format!(
            "prefab '{prefab_ref}' has no entry matching '{suffix}'"
        )),
        1 => Ok(matches.remove(0)),
        _ => Err(format!(
            "'{suffix}' matches more than one entry in prefab '{prefab_ref}'"
        )),
    }
}

fn walk(
    entries: &[Value],
    def_name: &str,
    suffix: &str,
    parent: Frame,
    matches: &mut Vec<TemplateSlot>,
) -> Result<(), String> {
    let def_index = entries
        .iter()
        .position(|e| entry_name(e) == def_name && type_norm(e) == "prefab")
        .ok_or_else(|| {
            format!(
                "prefab '{def_name}' is a disk preset; materialize it as an authored Prefab first"
            )
        })?;
    let props = entries[def_index]
        .get("args")
        .and_then(|a| a.get("props"))
        .and_then(|v| v.as_array())
        .cloned()
        .unwrap_or_default();

    for (i, entry) in props.iter().enumerate() {
        let kind = entry.get("kind").and_then(|v| v.as_str()).unwrap_or("prop");
        let name = entry.get("name").and_then(|v| v.as_str()).unwrap_or("obj");
        if kind == "prefab" {
            let Some(rest) = suffix.strip_prefix(&format!("{name}_")) else {
                continue;
            };
            let nested = entry.get("prefab").and_then(|v| v.as_str()).unwrap_or("");
            if nested.is_empty() {
                continue;
            }
            let child = Frame {
                pos: compose_position(f32_arr3(entry, "position", [0.0; 3]), parent),
                rot: add(parent.rot, f32_arr3(entry, "rotation_deg", [0.0; 3])),
                scale: mul3(parent.scale, f32_arr3(entry, "scale", [1.0; 3])),
            };
            walk(entries, nested, rest, child, matches)?;
        } else if name == suffix {
            matches.push(TemplateSlot {
                def_name: def_name.to_string(),
                def_index,
                entry_index: i,
                parent,
            });
        }
    }
    Ok(())
}

// How the instance arg rooted at `root` maps onto a prefab entry of the
// generated asset's type. Errors name the reason apply is unavailable.
pub(crate) fn map_field(asset_type: &str, root: &str) -> Result<FieldMap, String> {
    let ty = asset_type.to_lowercase().replace('_', "");
    match (ty.as_str(), root) {
        ("prop" | "pointlight", "position") => Ok(FieldMap::Position),
        ("prop", "rotation_deg") => Ok(FieldMap::Rotation),
        ("prop", "scale") => Ok(FieldMap::Scale),
        (
            "prop",
            "model" | "mesh" | "material" | "texture" | "parent" | "interactable" | "pickup"
            | "collider",
        ) => Ok(FieldMap::Direct(direct_key(root))),
        ("pointlight", "color") => Ok(FieldMap::Direct("light_color")),
        ("pointlight", "intensity") => Ok(FieldMap::Direct("light_intensity")),
        ("pointlight", "range") => Ok(FieldMap::Direct("light_range")),
        _ => Err(format!("'{root}' is not carried by the prefab entry")),
    }
}

// The &'static str for a same-named direct key (map_field's match arms pin the
// full set, so this cannot miss).
fn direct_key(root: &str) -> &'static str {
    for key in [
        "model",
        "mesh",
        "material",
        "texture",
        "parent",
        "interactable",
        "pickup",
        "collider",
    ] {
        if key == root {
            return key;
        }
    }
    unreachable!("unmapped direct key '{root}'")
}

// Write one instance value into a prefab entry: a direct field lands at the
// mapped key (sub-paths below the root preserved), a composed transform is
// inverted through the parent frame first.
pub(crate) fn write_field(
    entry: &mut Value,
    slot: &TemplateSlot,
    map: FieldMap,
    covered: &str,
    value: &Value,
) -> Result<(), String> {
    match map {
        FieldMap::Direct(key) => {
            let sub = covered.split_once('.').map(|(_, rest)| rest);
            let path = match sub {
                Some(rest) => format!("{key}.{rest}"),
                None => key.to_string(),
            };
            set_at_path(entry, &path, value.clone());
            Ok(())
        }
        FieldMap::Position => {
            let world = as_vec3(value).ok_or("position is not a 3-vector")?;
            for (i, s) in slot.parent.scale.iter().enumerate() {
                if *s == 0.0 {
                    return Err(format!(
                        "instance scale is zero on axis {i}; the local position is unrecoverable"
                    ));
                }
            }
            let delta = [
                (world[0] - slot.parent.pos[0]) / slot.parent.scale[0],
                (world[1] - slot.parent.pos[1]) / slot.parent.scale[1],
                (world[2] - slot.parent.pos[2]) / slot.parent.scale[2],
            ];
            let local = rotate_local_inv(delta, slot.parent.rot);
            entry["position"] = json_vec3(local.map(round3));
            Ok(())
        }
        FieldMap::Rotation => {
            let world = as_vec3(value).ok_or("rotation is not a 3-vector")?;
            let local = [
                world[0] - slot.parent.rot[0],
                world[1] - slot.parent.rot[1],
                world[2] - slot.parent.rot[2],
            ];
            entry["rotation_deg"] = json_vec3(local.map(round1));
            Ok(())
        }
        FieldMap::Scale => {
            let world = as_vec3(value).ok_or("scale is not a 3-vector")?;
            for (i, s) in slot.parent.scale.iter().enumerate() {
                if *s == 0.0 {
                    return Err(format!(
                        "instance scale is zero on axis {i}; the local scale is unrecoverable"
                    ));
                }
            }
            let local = [
                world[0] / slot.parent.scale[0],
                world[1] / slot.parent.scale[1],
                world[2] / slot.parent.scale[2],
            ];
            entry["scale"] = json_vec3(local.map(round3));
            Ok(())
        }
    }
}

// Forward composition, mirroring cook's expansion:
// world = parent.pos + parent.scale * R(parent.rot) * local.
fn compose_position(local: [f32; 3], parent: Frame) -> [f32; 3] {
    let r = rotate_local(local, parent.rot);
    [
        parent.pos[0] + parent.scale[0] * r[0],
        parent.pos[1] + parent.scale[1] * r[1],
        parent.pos[2] + parent.scale[2] * r[2],
    ]
}

// Rotate a local offset by a YXZ Euler rotation (degrees), matching the
// expansion's `rotate_local` exactly so the inverse below round-trips.
fn rotate_local(pos: [f32; 3], rotation_deg: [f32; 3]) -> [f32; 3] {
    let m = rotation_matrix(rotation_deg);
    [
        m[0][0] * pos[0] + m[0][1] * pos[1] + m[0][2] * pos[2],
        m[1][0] * pos[0] + m[1][1] * pos[1] + m[1][2] * pos[2],
        m[2][0] * pos[0] + m[2][1] * pos[1] + m[2][2] * pos[2],
    ]
}

// The inverse rotation: a rotation matrix's inverse is its transpose.
fn rotate_local_inv(pos: [f32; 3], rotation_deg: [f32; 3]) -> [f32; 3] {
    let m = rotation_matrix(rotation_deg);
    [
        m[0][0] * pos[0] + m[1][0] * pos[1] + m[2][0] * pos[2],
        m[0][1] * pos[0] + m[1][1] * pos[1] + m[2][1] * pos[2],
        m[0][2] * pos[0] + m[1][2] * pos[1] + m[2][2] * pos[2],
    ]
}

fn rotation_matrix(rotation_deg: [f32; 3]) -> [[f32; 3]; 3] {
    let [pitch_deg, yaw_deg, roll_deg] = rotation_deg;
    let (sp, cp) = (pitch_deg.to_radians().sin(), pitch_deg.to_radians().cos());
    let (sy, cy) = (yaw_deg.to_radians().sin(), yaw_deg.to_radians().cos());
    let (sr, cr) = (roll_deg.to_radians().sin(), roll_deg.to_radians().cos());
    [
        [cy * cr + sy * sp * sr, -cy * sr + sy * sp * cr, sy * cp],
        [cp * sr, cp * cr, -sp],
        [-sy * cr + cy * sp * sr, sy * sr + cy * sp * cr, cy * cp],
    ]
}

fn mul3(a: [f32; 3], b: [f32; 3]) -> [f32; 3] {
    [a[0] * b[0], a[1] * b[1], a[2] * b[2]]
}
fn round3(v: f32) -> f32 {
    (v * 1000.0).round() / 1000.0
}
fn round1(v: f32) -> f32 {
    (v * 10.0).round() / 10.0
}

fn as_vec3(v: &Value) -> Option<[f32; 3]> {
    let arr = v.as_array()?;
    if arr.len() != 3 {
        return None;
    }
    Some([
        arr[0].as_f64()? as f32,
        arr[1].as_f64()? as f32,
        arr[2].as_f64()? as f32,
    ])
}

fn json_vec3(v: [f32; 3]) -> Value {
    serde_json::json!([v[0], v[1], v[2]])
}

fn f32_arr3(v: &Value, key: &str, default: [f32; 3]) -> [f32; 3] {
    v.get(key)
        .and_then(|a| a.as_array())
        .filter(|a| a.len() == 3)
        .map(|a| {
            [
                a[0].as_f64().unwrap_or(default[0] as f64) as f32,
                a[1].as_f64().unwrap_or(default[1] as f64) as f32,
                a[2].as_f64().unwrap_or(default[2] as f64) as f32,
            ]
        })
        .unwrap_or(default)
}

fn set_at_path(v: &mut Value, path: &str, value: Value) {
    match path.split_once('.') {
        None => {
            v[path] = value;
        }
        Some((head, rest)) => {
            if !v.get(head).is_some_and(|c| c.is_object()) {
                v[head] = serde_json::json!({});
            }
            set_at_path(&mut v[head], rest, value);
        }
    }
}

fn type_norm(v: &Value) -> String {
    v.get("type")
        .and_then(|t| t.as_str())
        .unwrap_or("")
        .to_lowercase()
        .replace('_', "")
}

fn entry_name(v: &Value) -> &str {
    v.get("name").and_then(|n| n.as_str()).unwrap_or("")
}

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

    fn table_world() -> Vec<Value> {
        vec![
            json!({"name":"leaf","type":"Prefab","args":{"props":[
                {"name":"cup","kind":"prop","mesh":"box","position":[1,0,0],"scale":[2,2,2]}]}}),
            json!({"name":"table","type":"Prefab","args":{"props":[
                {"name":"top","kind":"prop","mesh":"box"},
                {"name":"set","kind":"prefab","prefab":"leaf","position":[0,1,0]}]}}),
            json!({"name":"inst","type":"Prop","args":{
                "prefab":"table","position":[10,0,0],"scale":[3,3,3]}}),
        ]
    }

    #[test]
    fn resolve_finds_a_top_level_entry() {
        let entries = table_world();
        let slot = resolve(&entries, "inst", "inst_top").unwrap();
        assert_eq!(slot.def_name, "table");
        assert_eq!(slot.entry_index, 0);
        assert_eq!(slot.parent.pos, [10.0, 0.0, 0.0]);
        assert_eq!(slot.parent.scale, [3.0, 3.0, 3.0]);
    }

    #[test]
    fn resolve_walks_nested_chains_composing_the_parent_frame() {
        let entries = table_world();
        let slot = resolve(&entries, "inst", "inst_set_cup").unwrap();
        assert_eq!(slot.def_name, "leaf");
        assert_eq!(slot.entry_index, 0);
        // The cup's parent frame is the nested `set` entry under the instance:
        // pos = inst + 3 * set(0,1,0), scale = 3 * 1.
        assert_eq!(slot.parent.pos, [10.0, 3.0, 0.0]);
        assert_eq!(slot.parent.scale, [3.0, 3.0, 3.0]);
    }

    #[test]
    fn resolve_rejects_a_preset_backed_chain() {
        let entries = vec![json!({"name":"inst","type":"Prop","args":{"prefab":"ghost"}})];
        let err = resolve(&entries, "inst", "inst_x").unwrap_err();
        assert!(err.contains("preset"), "{err}");
    }

    #[test]
    fn position_write_back_round_trips_the_expansion_composition() {
        // cook's nested test: cup world position is (13, 3, 0).
        let entries = table_world();
        let slot = resolve(&entries, "inst", "inst_set_cup").unwrap();
        let mut entry = json!({"name":"cup","kind":"prop","mesh":"box"});
        write_field(
            &mut entry,
            &slot,
            FieldMap::Position,
            "position",
            &json!([13.0, 3.0, 0.0]),
        )
        .unwrap();
        assert_eq!(entry["position"], json!([1.0, 0.0, 0.0]));
    }

    #[test]
    fn position_write_back_inverts_rotation() {
        let slot = TemplateSlot {
            def_name: "p".into(),
            def_index: 0,
            entry_index: 0,
            parent: Frame {
                pos: [0.0; 3],
                rot: [0.0, 90.0, 0.0],
                scale: [1.0; 3],
            },
        };
        // Yaw 90 maps local +X to world -Z, so world (0,0,-1) is local (1,0,0).
        let mut entry = json!({});
        write_field(
            &mut entry,
            &slot,
            FieldMap::Position,
            "position",
            &json!([0.0, 0.0, -1.0]),
        )
        .unwrap();
        assert_eq!(entry["position"], json!([1.0, 0.0, 0.0]));
    }

    #[test]
    fn zero_parent_scale_refuses_position_and_scale_write_back() {
        let slot = TemplateSlot {
            def_name: "p".into(),
            def_index: 0,
            entry_index: 0,
            parent: Frame {
                pos: [0.0; 3],
                rot: [0.0; 3],
                scale: [0.0, 1.0, 1.0],
            },
        };
        let mut entry = json!({});
        assert!(
            write_field(
                &mut entry,
                &slot,
                FieldMap::Position,
                "position",
                &json!([1, 2, 3])
            )
            .is_err()
        );
        assert!(
            write_field(
                &mut entry,
                &slot,
                FieldMap::Scale,
                "scale",
                &json!([1, 2, 3])
            )
            .is_err()
        );
    }

    #[test]
    fn rotation_and_scale_invert_componentwise() {
        let slot = TemplateSlot {
            def_name: "p".into(),
            def_index: 0,
            entry_index: 0,
            parent: Frame {
                pos: [0.0; 3],
                rot: [0.0, 45.0, 0.0],
                scale: [2.0, 2.0, 2.0],
            },
        };
        let mut entry = json!({});
        write_field(
            &mut entry,
            &slot,
            FieldMap::Rotation,
            "rotation_deg",
            &json!([0.0, 90.0, 0.0]),
        )
        .unwrap();
        assert_eq!(entry["rotation_deg"], json!([0.0, 45.0, 0.0]));
        write_field(
            &mut entry,
            &slot,
            FieldMap::Scale,
            "scale",
            &json!([6.0, 2.0, 4.0]),
        )
        .unwrap();
        assert_eq!(entry["scale"], json!([3.0, 1.0, 2.0]));
    }

    #[test]
    fn direct_fields_preserve_sub_paths_and_mapped_names() {
        let slot = TemplateSlot {
            def_name: "p".into(),
            def_index: 0,
            entry_index: 0,
            parent: Frame {
                pos: [0.0; 3],
                rot: [0.0; 3],
                scale: [1.0; 3],
            },
        };
        let mut entry = json!({"collider": {"shape": "box", "radius": 1.0}});
        write_field(
            &mut entry,
            &slot,
            map_field("Prop", "collider").unwrap(),
            "collider.shape",
            &json!("sphere"),
        )
        .unwrap();
        // Only the covered sub-path changes; the sibling survives.
        assert_eq!(entry["collider"], json!({"shape": "sphere", "radius": 1.0}));

        let mut light = json!({});
        write_field(
            &mut light,
            &slot,
            map_field("PointLight", "intensity").unwrap(),
            "intensity",
            &json!(4.0),
        )
        .unwrap();
        assert_eq!(light["light_intensity"], json!(4.0));
    }

    #[test]
    fn map_field_rejects_uncarried_args() {
        assert!(map_field("Prop", "visible").is_err());
        assert!(map_field("Sprite", "tint").is_err());
    }
}