web-api-cat 0.6.2

//! `Element`-side native methods: `getAttribute`, `setAttribute`,
//! `hasAttribute`, `querySelector`.
//!
//! Element objects are boa-cat [`Object`]s carrying these properties:
//!
//! - `tagName`: lowercased tag name (string).
//! - `id`: id attribute or empty string.
//! - `className`: class attribute or empty string.
//! - `textContent`: concatenated text of all descendant text nodes.
//! - `children`: array of child element objects.
//! - `__attributes`: object mapping attribute name -> value.
//! - `getAttribute`, `setAttribute`, `hasAttribute`,
//!   `querySelector`: native callables.

use std::collections::BTreeMap;

use boa_cat::Value;
use boa_cat::fuel::Fuel;
use boa_cat::heap::Heap;
use boa_cat::outcome::{EvalResult, Outcome};
use boa_cat::value::{Object, ObjectId};

/// `Element.getAttribute(name)` native implementation.
///
/// # Errors
///
/// Never returns `Err`; bad input yields `Value::Null`.
#[allow(clippy::needless_pass_by_value)]
#[allow(clippy::unnecessary_wraps)]
pub fn get_attribute_impl(args: Vec<Value>, this: Value, heap: Heap, fuel: Fuel) -> EvalResult {
    let name = string_arg(&args, 0);
    let outcome = read_attribute(&this, &name, &heap).map_or(Outcome::Normal(Value::Null), |v| {
        Outcome::Normal(Value::String(v))
    });
    Ok((outcome, heap, fuel))
}

/// `Element.hasAttribute(name)` native implementation.
///
/// # Errors
///
/// Never returns `Err`.
#[allow(clippy::needless_pass_by_value)]
#[allow(clippy::unnecessary_wraps)]
pub fn has_attribute_impl(args: Vec<Value>, this: Value, heap: Heap, fuel: Fuel) -> EvalResult {
    let name = string_arg(&args, 0);
    let present = read_attribute(&this, &name, &heap).is_some();
    Ok((Outcome::Normal(Value::Boolean(present)), heap, fuel))
}

/// `Element.setAttribute(name, value)` native implementation.
///
/// # Errors
///
/// Never returns `Err`; missing element / attributes object yields the
/// unchanged heap.
#[allow(clippy::needless_pass_by_value)]
#[allow(clippy::unnecessary_wraps)]
pub fn set_attribute_impl(args: Vec<Value>, this: Value, heap: Heap, fuel: Fuel) -> EvalResult {
    let name = string_arg(&args, 0);
    let value = string_arg(&args, 1);
    let new_heap = write_attribute(&this, &name, &value, heap);
    Ok((Outcome::Normal(Value::Undefined), new_heap, fuel))
}

fn object_id_of(value: &Value) -> Option<ObjectId> {
    match value {
        Value::Object(id) => Some(*id),
        Value::Undefined
        | Value::Null
        | Value::Boolean(_)
        | Value::Number(_)
        | Value::String(_)
        | Value::Function(_)
        | Value::Native(_)
        | Value::Promise(_) => None,
    }
}

fn attributes_id_of(element: &Object) -> Option<ObjectId> {
    match element.get("__attributes") {
        Some(value) => object_id_of(value),
        None => None,
    }
}

fn read_attribute(this: &Value, name: &str, heap: &Heap) -> Option<String> {
    let element_id = object_id_of(this)?;
    let element = heap.object(element_id)?;
    let attrs_id = attributes_id_of(element)?;
    let attrs = heap.object(attrs_id)?;
    match attrs.get(name) {
        Some(Value::String(s)) => Some(s.clone()),
        Some(_) | None => None,
    }
}

fn write_attribute(this: &Value, name: &str, value: &str, heap: Heap) -> Heap {
    let Some(element_id) = object_id_of(this) else {
        return heap;
    };
    let Some(element) = heap.object(element_id).cloned() else {
        return heap;
    };
    let Some(attrs_id) = attributes_id_of(&element) else {
        return heap;
    };
    let Some(attrs) = heap.object(attrs_id).cloned() else {
        return heap;
    };
    let updated_attrs = attrs.with(name.to_owned(), Value::String(value.to_owned()));
    let heap = heap
        .store_object(attrs_id, updated_attrs)
        .unwrap_or_else(|h| h);
    let mirror_key = match name {
        "id" => Some("id"),
        "class" => Some("className"),
        _other => None,
    };
    if let Some(key) = mirror_key {
        let updated_element = element.with(key.to_owned(), Value::String(value.to_owned()));
        heap.store_object(element_id, updated_element)
            .unwrap_or_else(|h| h)
    } else {
        heap
    }
}

fn string_arg(args: &[Value], idx: usize) -> String {
    match args.get(idx) {
        Some(Value::String(s)) => s.clone(),
        Some(other) => format!("{other}"),
        None => String::new(),
    }
}

/// Build an attributes object (`__attributes`) from a list of pairs.
#[must_use]
pub fn build_attributes_object(pairs: &[(String, String)], heap: Heap) -> (Value, Heap) {
    let map: BTreeMap<String, Value> = pairs
        .iter()
        .map(|(k, v)| (k.clone(), Value::String(v.clone())))
        .collect();
    let (id, heap) = heap.alloc_object(Object::from_properties(map));
    (Value::Object(id), heap)
}

/// `Element.querySelector(selector)` -- limited v0 selector subset
/// (`tag`, `.class`, `#id`, `tag.class`, `tag#id`).
///
/// # Errors
///
/// Never returns `Err`; no match yields `Value::Null`.
#[allow(clippy::needless_pass_by_value)]
#[allow(clippy::unnecessary_wraps)]
pub fn query_selector_impl(args: Vec<Value>, this: Value, heap: Heap, fuel: Fuel) -> EvalResult {
    let selector = string_arg(&args, 0);
    let pattern = parse_simple_selector(&selector);
    let outcome =
        find_matching(&this, &pattern, &heap).map_or(Outcome::Normal(Value::Null), Outcome::Normal);
    Ok((outcome, heap, fuel))
}

#[derive(Debug, Clone, Default)]
struct SelectorPattern {
    tag: Option<String>,
    id: Option<String>,
    class: Option<String>,
}

fn parse_simple_selector(source: &str) -> SelectorPattern {
    let trimmed = source.trim();
    parse_selector_recursive(trimmed, 0, SelectorPattern::default())
}

fn parse_selector_recursive(source: &str, start: usize, acc: SelectorPattern) -> SelectorPattern {
    let bytes = source.as_bytes();
    if start >= bytes.len() {
        acc
    } else {
        match bytes.get(start) {
            Some(b'#') => {
                let end = scan_ident(bytes, start + 1);
                let name = source.get(start + 1..end).unwrap_or("").to_owned();
                parse_selector_recursive(
                    source,
                    end,
                    SelectorPattern {
                        id: Some(name),
                        ..acc
                    },
                )
            }
            Some(b'.') => {
                let end = scan_ident(bytes, start + 1);
                let name = source.get(start + 1..end).unwrap_or("").to_owned();
                parse_selector_recursive(
                    source,
                    end,
                    SelectorPattern {
                        class: Some(name),
                        ..acc
                    },
                )
            }
            Some(_) => {
                let end = scan_ident(bytes, start);
                let name = source.get(start..end).unwrap_or("").to_ascii_lowercase();
                if name.is_empty() {
                    acc
                } else {
                    parse_selector_recursive(
                        source,
                        end,
                        SelectorPattern {
                            tag: Some(name),
                            ..acc
                        },
                    )
                }
            }
            None => acc,
        }
    }
}

fn scan_ident(bytes: &[u8], start: usize) -> usize {
    bytes
        .iter()
        .enumerate()
        .skip(start)
        .find(|(_, b)| !is_ident_byte(**b))
        .map_or(bytes.len(), |(i, _)| i)
}

fn is_ident_byte(b: u8) -> bool {
    b.is_ascii_alphanumeric() || b == b'-' || b == b'_'
}

fn find_matching(this: &Value, pattern: &SelectorPattern, heap: &Heap) -> Option<Value> {
    let root_id = object_id_of(this)?;
    walk_descendants(root_id, pattern, heap)
}

fn walk_descendants(node_id: ObjectId, pattern: &SelectorPattern, heap: &Heap) -> Option<Value> {
    let children = element_children(node_id, heap);
    children.iter().find_map(|child_id| {
        if matches_pattern(*child_id, pattern, heap) {
            Some(Value::Object(*child_id))
        } else {
            walk_descendants(*child_id, pattern, heap)
        }
    })
}

fn element_children(node_id: ObjectId, heap: &Heap) -> Vec<ObjectId> {
    let Some(object) = heap.object(node_id) else {
        return Vec::new();
    };
    let Some(children_id) = object.get("children").and_then(object_id_of) else {
        return Vec::new();
    };
    let Some(children) = heap.object(children_id) else {
        return Vec::new();
    };
    let length = array_length(children);
    (0..length)
        .filter_map(|i| children.get(&format!("{i}")).and_then(object_id_of))
        .collect()
}

fn array_length(array: &Object) -> u32 {
    match array.get("length") {
        Some(Value::Number(n)) if n.is_finite() && *n >= 0.0 => {
            #[allow(clippy::cast_possible_truncation, clippy::cast_sign_loss)]
            let len = *n as u32;
            len
        }
        Some(_) | None => 0,
    }
}

fn matches_pattern(node_id: ObjectId, pattern: &SelectorPattern, heap: &Heap) -> bool {
    let Some(object) = heap.object(node_id) else {
        return false;
    };
    let tag_ok = pattern
        .tag
        .as_ref()
        .is_none_or(|want| string_property(object, "tagName").eq_ignore_ascii_case(want));
    let id_ok = pattern
        .id
        .as_ref()
        .is_none_or(|want| string_property(object, "id") == *want);
    let class_ok = pattern.class.as_ref().is_none_or(|want| {
        string_property(object, "className")
            .split_ascii_whitespace()
            .any(|c| c == want)
    });
    tag_ok && id_ok && class_ok
}

fn string_property(object: &Object, key: &str) -> String {
    match object.get(key) {
        Some(Value::String(s)) => s.clone(),
        Some(_) | None => String::new(),
    }
}

/// Public helper used by `document.querySelector` to perform the search
/// from the document root.
#[must_use]
pub fn find_first_descendant(root: ObjectId, pattern_source: &str, heap: &Heap) -> Option<Value> {
    let pattern = parse_simple_selector(pattern_source);
    walk_descendants(root, &pattern, heap)
}

/// Public helper for `document.getElementById`.
#[must_use]
pub fn find_by_id(root: ObjectId, id: &str, heap: &Heap) -> Option<Value> {
    let pattern = SelectorPattern {
        id: Some(id.to_owned()),
        ..SelectorPattern::default()
    };
    walk_descendants(root, &pattern, heap)
}

/// `Element.appendChild(child)` (v0.6.1): append `child` to
/// `this.children`, updating `length`.  Returns `child` per spec
/// so the caller can chain.  No-ops when `this` or `child` aren't
/// Object values, or when the children-array slot is missing /
/// non-object.
///
/// Mutation flow: clone the children array Object, write the new
/// numeric-key entry, write `length`, then `store_object` both the
/// children Object and the parent (the parent's `children` slot
/// already points at the same children-array `ObjectId`, so the
/// parent update is implicit -- only the children Object's
/// in-place mutation matters).  `extract_document` walks
/// `children` numerically in the next back-prop pass, so the new
/// child reaches layout / paint automatically.
///
/// # Errors
///
/// Never returns `Err`; bad inputs yield `Value::Undefined`.
#[allow(clippy::needless_pass_by_value, clippy::unnecessary_wraps)]
pub fn append_child_impl(args: Vec<Value>, this: Value, heap: Heap, fuel: Fuel) -> EvalResult {
    let child = args.first().cloned().unwrap_or(Value::Undefined);
    let outcome_heap = append_child_to_parent(&this, &child, heap);
    Ok((Outcome::Normal(child), outcome_heap, fuel))
}

fn append_child_to_parent(this: &Value, child: &Value, heap: Heap) -> Heap {
    if let Some((children_id, children_obj)) = children_object_of(this, &heap) {
        let length = array_length(&children_obj);
        let updated_children = children_obj
            .with(format!("{length}"), child.clone())
            .with("length".to_owned(), Value::Number(f64::from(length + 1)));
        heap.store_object(children_id, updated_children)
            .unwrap_or_else(|h| h)
    } else {
        heap
    }
}

fn children_object_of(this: &Value, heap: &Heap) -> Option<(ObjectId, Object)> {
    let parent_id = object_id_of(this)?;
    let parent = heap.object(parent_id)?;
    let children_id = parent.get("children").and_then(|v| match v {
        Value::Object(id) => Some(*id),
        Value::Undefined
        | Value::Null
        | Value::Boolean(_)
        | Value::Number(_)
        | Value::String(_)
        | Value::Function(_)
        | Value::Native(_)
        | Value::Promise(_) => None,
    })?;
    let children_obj = heap.object(children_id)?.clone();
    Some((children_id, children_obj))
}

/// `Element.removeChild(child)` (v0.6.2): remove `child` from
/// `this.children` and return it.  Remaining children shift down
/// to fill the freed slot; `length` decrements.  No-ops (and still
/// returns the requested `child`) when `this` or `child` aren't
/// Object values, the children-array slot is missing / non-object,
/// or `child` isn't currently a child of `this` (the DOM spec
/// throws `NotFoundError` here; this scoped impl no-ops to stay
/// inside the always-`Ok` `NativeFn` contract).
///
/// # Errors
///
/// Never returns `Err`; bad inputs no-op.
#[allow(clippy::needless_pass_by_value, clippy::unnecessary_wraps)]
pub fn remove_child_impl(args: Vec<Value>, this: Value, heap: Heap, fuel: Fuel) -> EvalResult {
    let child = args.first().cloned().unwrap_or(Value::Undefined);
    let outcome_heap = remove_child_from_parent(&this, &child, heap);
    Ok((Outcome::Normal(child), outcome_heap, fuel))
}

fn remove_child_from_parent(this: &Value, child: &Value, heap: Heap) -> Heap {
    let Some((children_id, children_obj)) = children_object_of(this, &heap) else {
        return heap;
    };
    let Some(child_id) = object_id_of(child) else {
        return heap;
    };
    let length = array_length(&children_obj);
    let Some(removal_index) = (0..length)
        .find(|i| children_obj.get(&format!("{i}")).and_then(object_id_of) == Some(child_id))
    else {
        return heap;
    };
    let new_length = length.saturating_sub(1);
    let pairs: BTreeMap<String, Value> = (0..length)
        .filter(|i| *i != removal_index)
        .enumerate()
        .map(|(new_idx, old_idx)| {
            let value = children_obj
                .get(&format!("{old_idx}"))
                .cloned()
                .unwrap_or(Value::Null);
            (format!("{new_idx}"), value)
        })
        .chain(std::iter::once((
            "length".to_owned(),
            Value::Number(f64::from(new_length)),
        )))
        .collect();
    let new_children = Object::from_properties(pairs);
    heap.store_object(children_id, new_children)
        .unwrap_or_else(|h| h)
}

/// `Element.insertBefore(newNode, referenceNode)` (v0.6.2): insert
/// `newNode` into `this.children` immediately before
/// `referenceNode`, returning `newNode`.  Existing children at and
/// after `referenceNode`'s slot shift up; `length` increments.  If
/// `referenceNode` is `null` / `undefined` / any non-Object value
/// the call falls through to `appendChild`-like end-of-list
/// behaviour (matching the DOM spec's `null` case).  No-ops if
/// `this` isn't an Object, the children-array slot is missing /
/// non-object, or `referenceNode` is a real Object but isn't
/// actually a child of `this` (the DOM spec throws
/// `NotFoundError`; this scoped impl no-ops).
///
/// # Errors
///
/// Never returns `Err`; bad inputs yield `Value::Undefined`.
#[allow(clippy::needless_pass_by_value, clippy::unnecessary_wraps)]
pub fn insert_before_impl(args: Vec<Value>, this: Value, heap: Heap, fuel: Fuel) -> EvalResult {
    let new_node = args.first().cloned().unwrap_or(Value::Undefined);
    let ref_node = args.get(1).cloned().unwrap_or(Value::Null);
    let outcome_heap = insert_before_into_parent(&this, &new_node, &ref_node, heap);
    Ok((Outcome::Normal(new_node), outcome_heap, fuel))
}

fn insert_before_into_parent(this: &Value, new_node: &Value, ref_node: &Value, heap: Heap) -> Heap {
    let ref_id_opt = object_id_of(ref_node);
    if ref_id_opt.is_none() {
        append_child_to_parent(this, new_node, heap)
    } else {
        let Some((children_id, children_obj)) = children_object_of(this, &heap) else {
            return heap;
        };
        let Some(ref_id) = ref_id_opt else {
            return heap;
        };
        let length = array_length(&children_obj);
        let Some(insert_index) = (0..length)
            .find(|i| children_obj.get(&format!("{i}")).and_then(object_id_of) == Some(ref_id))
        else {
            return heap;
        };
        let new_length = length + 1;
        let pairs: BTreeMap<String, Value> = (0..new_length)
            .map(|new_idx| {
                let value = match new_idx.cmp(&insert_index) {
                    std::cmp::Ordering::Less => children_obj
                        .get(&format!("{new_idx}"))
                        .cloned()
                        .unwrap_or(Value::Null),
                    std::cmp::Ordering::Equal => new_node.clone(),
                    std::cmp::Ordering::Greater => {
                        let old_idx = new_idx - 1;
                        children_obj
                            .get(&format!("{old_idx}"))
                            .cloned()
                            .unwrap_or(Value::Null)
                    }
                };
                (format!("{new_idx}"), value)
            })
            .chain(std::iter::once((
                "length".to_owned(),
                Value::Number(f64::from(new_length)),
            )))
            .collect();
        let new_children = Object::from_properties(pairs);
        heap.store_object(children_id, new_children)
            .unwrap_or_else(|h| h)
    }
}