euv-macros 0.5.12

use crate::*;

/// Checks whether the next tokens after the current position form a `::` path separator.
///
/// This is used to distinguish between a single `:` (attribute key-value separator)
/// and `::` (Rust path separator like `Enum::Variant`). When an `Ident` is followed
/// by `::`, it should be treated as the start of a path expression rather than an
/// attribute key.
///
/// # Arguments
///
/// - `&ParseStream` - The parse stream to check.
///
/// # Returns
///
/// - `bool` - `true` if the next two tokens after the current position are `::`.
pub(crate) fn is_double_colon(content: ParseStream) -> bool {
    let forked: ParseBuffer<'_> = content.fork();
    let _: Ident = match forked.parse() {
        Ok(ident) => ident,
        Err(_) => return false,
    };
    forked.peek(Token![::])
}

/// Sets the user-defined component registry for the current thread.
///
/// # Arguments
///
/// - `HashMap<String, ComponentInfo>` - The map of function names to component metadata.
pub(crate) fn set_user_fn_names(names: HashMap<String, ComponentInfo>) {
    unsafe {
        let pointer: *mut MaybeUninit<HashMap<String, ComponentInfo>> = &raw mut USER_FN_NAMES;
        (*pointer).write(names);
    }
}

/// Returns the already-loaded component registry without re-scanning the file system.
///
/// This is used by `HtmlDynamicTag::to_tokens` to avoid calling `load_component_registry`
/// again, since the registry has already been populated by `parse_html` before
/// token generation begins.
///
/// # Returns
///
/// - `HashMap<String, ComponentInfo>` - The loaded component registry.
pub(crate) fn get_loaded_component_registry() -> HashMap<String, ComponentInfo> {
    unsafe {
        let pointer: *const MaybeUninit<HashMap<String, ComponentInfo>> = &raw const USER_FN_NAMES;
        (*pointer).assume_init_ref().clone()
    }
}

/// Checks whether a given name corresponds to a user-defined component function.
///
/// # Arguments
///
/// - `&str` - The name to check against the stored component registry.
///
/// # Returns
///
/// - `bool` - `true` if the name exists in the component registry, `false` otherwise.
pub(crate) fn is_user_fn(name: &str) -> bool {
    unsafe {
        let pointer: *const MaybeUninit<HashMap<String, ComponentInfo>> = &raw const USER_FN_NAMES;
        (*pointer).assume_init_ref().contains_key(name)
    }
}

/// Returns the Props type name for a given component function name.
///
/// # Arguments
///
/// - `&str` - The component function name.
///
/// # Returns
///
/// - `Option<&'static str>` - The Props type name if found.
pub(crate) fn get_user_fn_props_type(name: &str) -> Option<&'static str> {
    unsafe {
        let pointer: *const MaybeUninit<HashMap<String, ComponentInfo>> = &raw const USER_FN_NAMES;
        (*pointer)
            .assume_init_ref()
            .get(name)
            .map(|info: &ComponentInfo| info.get_props_type().as_str())
    }
}

/// Returns the props field names for a given component function name.
///
/// Used to determine whether a standalone identifier inside a component body
/// should be treated as an attribute shorthand (e.g., `panel_open` → `panel_open: panel_open`).
///
/// # Arguments
///
/// - `&str` - The component function name.
///
/// # Returns
///
/// - `Option<&'static Vec<String>>` - The list of props field names if the component is found.
pub(crate) fn get_user_fn_props_fields(name: &str) -> Option<&'static Vec<String>> {
    unsafe {
        let pointer: *const MaybeUninit<HashMap<String, ComponentInfo>> = &raw const USER_FN_NAMES;
        (*pointer)
            .assume_init_ref()
            .get(name)
            .map(|info: &ComponentInfo| info.get_props_fields())
    }
}

/// Returns the props field type map for a given component function name.
///
/// Maps field name → type string (e.g., `"children"` → `"VirtualNode"`).
///
/// # Arguments
///
/// - `&str` - The component function name.
///
/// # Returns
///
/// - `Option<&'static HashMap<String, String>>` - The field type map if the component is found.
pub(crate) fn get_user_fn_props_field_types(
    name: &str,
) -> Option<&'static HashMap<String, String>> {
    unsafe {
        let pointer: *const MaybeUninit<HashMap<String, ComponentInfo>> = &raw const USER_FN_NAMES;
        (*pointer)
            .assume_init_ref()
            .get(name)
            .map(|info: &ComponentInfo| info.get_props_field_types())
    }
}

/// Parses the input tokens into a euv VNode expression.
///
/// Supports zero, one, or multiple root-level HTML nodes:
/// - `html! {}` → `VirtualNode::Empty`
/// - `html! { div { ... } }` → single `VirtualNode`
/// - `html! { div { ... } span { ... } }` → `VirtualNode::Fragment(vec![...])`
///
/// Before parsing, reads the component registry file to discover which
/// function names are marked as components via `#[component]`. This allows
/// the `html!` macro to distinguish between component function calls and
/// native HTML element tags.
///
/// # Arguments
///
/// - `TokenStream` - The raw token stream representing HTML markup.
///
/// # Returns
///
/// - `TokenStream` - The generated token stream constructing the corresponding virtual node.
pub fn parse_html(input: TokenStream) -> TokenStream {
    let fn_names: HashMap<String, ComponentInfo> = load_component_registry();
    set_user_fn_names(fn_names);
    let tokens: proc_macro2::TokenStream = match parse::<HtmlRoot>(input) {
        Ok(nodes) => nodes.into_token_stream(),
        Err(error) => return error.to_compile_error().into(),
    };
    TokenStream::from(tokens)
}

/// Loads the component registry by scanning the project source for `#[component]` annotations.
///
/// Uses a file-based cache in the `OUT_DIR` directory to avoid re-scanning and
/// re-parsing all source files on every `html!` macro invocation. The cache is
/// invalidated when the set of source files or their modification times change.
///
/// Recursively scans `.rs` files under `CARGO_MANIFEST_DIR/src/` and extracts
/// function names and their Props type names from annotated functions.
///
/// # Returns
///
/// - `HashMap<String, ComponentInfo>` - Map of component function names to component metadata.
pub(crate) fn load_component_registry() -> HashMap<String, ComponentInfo> {
    let Ok(manifest_dir) = env::var(CARGO_MANIFEST_DIR) else {
        return HashMap::new();
    };
    let src_dir: PathBuf = PathBuf::from(&manifest_dir).join(SRC_DIR);
    let mut rust_source_files: Vec<PathBuf> = Vec::new();
    collect_rs_files(&src_dir, &mut rust_source_files);
    let fingerprint: String = compute_fingerprint(&rust_source_files);
    if let Ok(out_dir) = env::var(ENV_OUT_DIR) {
        let cache_path: PathBuf = PathBuf::from(out_dir).join(REGISTRY_CACHE_FILE_NAME);
        if let Some(cached) = try_load_cache(&cache_path, &fingerprint) {
            return cached;
        }
        let registry: HashMap<String, ComponentInfo> =
            build_registry_from_files(&rust_source_files);
        try_save_cache(&cache_path, &fingerprint, &registry);
        registry
    } else {
        build_registry_from_files(&rust_source_files)
    }
}

/// Computes a fingerprint string from the sorted list of source file paths
/// and their modification timestamps. Used to determine whether the cache
/// is still valid or needs to be rebuilt.
///
/// # Arguments
///
/// - `&[PathBuf]` - The sorted list of source file paths.
///
/// # Returns
///
/// - `String` - The computed fingerprint string.
fn compute_fingerprint(files: &[PathBuf]) -> String {
    let mut fingerprint: String = String::new();
    let mut sorted_files: Vec<&PathBuf> = files.iter().collect();
    sorted_files.sort();
    for path in sorted_files {
        fingerprint.push_str(&path.to_string_lossy());
        fingerprint.push(CHAR_SEMICOLON);
        if let Ok(metadata) = std::fs::metadata(path)
            && let Ok(modified) = metadata.modified()
            && let Ok(duration) = modified.duration_since(std::time::UNIX_EPOCH)
        {
            fingerprint.push_str(&duration.as_millis().to_string());
        }
        fingerprint.push(CHAR_SEMICOLON);
    }
    fingerprint
}

/// Attempts to load a cached component registry from the given cache path.
///
/// Returns `Some(registry)` if the cache exists and the stored fingerprint
/// matches the current fingerprint, indicating the cache is still valid.
/// Returns `None` if the cache does not exist, cannot be read, or is stale.
///
/// # Arguments
///
/// - `&PathBuf` - The path to the cache file.
/// - `&str` - The current fingerprint to validate against.
///
/// # Returns
///
/// - `Option<HashMap<String, ComponentInfo>>` - The cached registry if valid, or `None`.
fn try_load_cache(
    cache_path: &PathBuf,
    current_fingerprint: &str,
) -> Option<HashMap<String, ComponentInfo>> {
    let content: String = read_to_string(cache_path).ok()?;
    let (stored_fingerprint, data) = content.split_once(CHAR_NEWLINE)?;
    if stored_fingerprint != current_fingerprint {
        return None;
    }
    serde_json::from_str(data).ok()
}

/// Attempts to save the component registry to the given cache path,
/// along with the current fingerprint for future validation.
///
/// Silently ignores errors since caching is optional.
///
/// # Arguments
///
/// - `&PathBuf` - The path to the cache file.
/// - `&str` - The current fingerprint string.
/// - `&HashMap<String, ComponentInfo>` - The registry to cache.
fn try_save_cache(
    cache_path: &PathBuf,
    fingerprint: &str,
    registry: &HashMap<String, ComponentInfo>,
) {
    if let Ok(data) = serde_json::to_string(registry) {
        let content: String = format!("{fingerprint}{CHAR_NEWLINE}{data}");
        let _ = std::fs::write(cache_path, content);
    }
}

/// Builds the component registry by parsing all source files in a single pass.
///
/// Each file is read and parsed exactly once, extracting both struct definitions
/// (for Props field information) and component function annotations simultaneously.
///
/// # Arguments
///
/// - `&[PathBuf]` - The list of source file paths to parse.
///
/// # Returns
///
/// - `HashMap<String, ComponentInfo>` - Map of component function names to component metadata.
fn build_registry_from_files(files: &[PathBuf]) -> HashMap<String, ComponentInfo> {
    let mut global_props_fields_map: HashMap<String, Vec<String>> = HashMap::new();
    let mut global_props_field_types_map: HashMap<String, HashMap<String, String>> = HashMap::new();
    let mut component_entries: Vec<(String, String)> = Vec::new();
    for path in files {
        let Ok(content) = read_to_string(path) else {
            continue;
        };
        let Ok(file) = parse_file(&content) else {
            continue;
        };
        global_props_fields_map.extend(extract_props_structs(&file));
        global_props_field_types_map.extend(extract_props_struct_types(&file));
        extract_component_entries(&file, &mut component_entries);
    }
    component_entries
        .into_iter()
        .map(|(fn_name, props_type): (String, String)| {
            let props_fields: Vec<String> = global_props_fields_map
                .get(&props_type)
                .cloned()
                .unwrap_or_default();
            let props_field_types: HashMap<String, String> = global_props_field_types_map
                .get(&props_type)
                .cloned()
                .unwrap_or_default();
            (
                fn_name,
                ComponentInfo {
                    props_type,
                    props_fields,
                    props_field_types,
                },
            )
        })
        .collect()
}

/// Extracts component function entries from a parsed file.
///
/// Collects (function_name, props_type) pairs for functions annotated with `#[component]`.
///
/// # Arguments
///
/// - `&File` - The parsed Rust source file.
/// - `&mut Vec<(String, String)>` - The vector to populate with (fn_name, props_type) pairs.
fn extract_component_entries(file: &File, entries: &mut Vec<(String, String)>) {
    file.items
        .iter()
        .filter_map(|item: &Item| {
            let Item::Fn(item_fn) = item else {
                return None;
            };
            item_fn
                .attrs
                .iter()
                .any(|attr: &Attribute| attr.path().is_ident(COMPONENT_ATTR))
                .then(|| {
                    let fn_name: String = item_fn.sig.ident.to_string();
                    let props_type: String = extract_props_type_from_fn(item_fn);
                    (fn_name, props_type)
                })
        })
        .for_each(|entry: (String, String)| {
            entries.push(entry);
        });
}

/// Recursively scans a directory for `.rs` files and collects their paths.
///
/// # Arguments
///
/// - `&PathBuf` - The directory to scan.
/// - `&mut Vec<PathBuf>` - The vector to populate with discovered file paths.
fn collect_rs_files(dir: &PathBuf, files: &mut Vec<PathBuf>) {
    let Ok(entries) = read_dir(dir) else {
        return;
    };
    for entry in entries.flatten() {
        let path: PathBuf = entry.path();
        if path.is_dir() {
            collect_rs_files(&path, files);
        } else if path
            .extension()
            .is_some_and(|ext: &OsStr| ext == OsStr::new(RUST_FILE_EXTENSION))
        {
            files.push(path);
        }
    }
}

/// Extracts all struct definitions from a file and maps their names to field name lists.
///
/// # Arguments
///
/// - `&File` - The parsed Rust source file.
///
/// # Returns
///
/// - `HashMap<String, Vec<String>>` - Map of struct name → list of field names.
fn extract_props_structs(file: &File) -> HashMap<String, Vec<String>> {
    file.items
        .iter()
        .filter_map(|item: &Item| {
            let Item::Struct(item_struct) = item else {
                return None;
            };
            Some((
                item_struct.ident.to_string(),
                item_struct
                    .fields
                    .iter()
                    .filter_map(|field: &Field| {
                        field.ident.as_ref().map(|ident: &Ident| ident.to_string())
                    })
                    .collect(),
            ))
        })
        .collect()
}

/// Extracts all struct definitions from a file and maps their names to field-type maps.
///
/// Each field's type is resolved to its last path segment (e.g., `VirtualNode`, `String`).
///
/// # Arguments
///
/// - `&File` - The parsed Rust source file.
///
/// # Returns
///
/// - `HashMap<String, HashMap<String, String>>` - Map of struct name → (field name → type string).
fn extract_props_struct_types(file: &File) -> HashMap<String, HashMap<String, String>> {
    file.items
        .iter()
        .filter_map(|item: &Item| {
            let Item::Struct(item_struct) = item else {
                return None;
            };
            Some((
                item_struct.ident.to_string(),
                item_struct
                    .fields
                    .iter()
                    .filter_map(|field: &Field| {
                        field.ident.as_ref().map(|ident: &Ident| {
                            (ident.to_string(), extract_type_last_segment(&field.ty))
                        })
                    })
                    .collect(),
            ))
        })
        .collect()
}

/// Extracts the last segment identifier from a type path.
///
/// For example, `::euv::VirtualNode` → `"VirtualNode"`, `String` → `"String"`.
/// Falls back to the full type string representation if the type is not a path.
///
/// # Arguments
///
/// - `&Type` - The syn type to extract from.
///
/// # Returns
///
/// - `String` - The last segment of the type path.
fn extract_type_last_segment(param_type: &Type) -> String {
    if let Type::Path(type_path) = param_type
        && let Some(segment) = type_path.path.segments.last()
    {
        return segment.ident.to_string();
    }
    param_type
        .to_token_stream()
        .to_string()
        .replace(CHAR_SPACE, STR_EMPTY)
}

/// Extracts the Props type name from the first parameter of a component function.
///
/// Looks for the first parameter's type. If the type is `VirtualNode<T>`,
/// extracts the generic argument `T` as the Props type name. Falls back to
/// checking for a simple path type (e.g., `PrimaryButtonProps`) for backward
/// compatibility. Returns an empty string if neither pattern matches.
///
/// # Arguments
///
/// - `&syn::ItemFn` - The function item to extract from.
///
/// # Returns
///
/// - `String` - The Props type name, or empty string if not extractable.
fn extract_props_type_from_fn(item_fn: &syn::ItemFn) -> String {
    let inputs: &syn::punctuated::Punctuated<syn::FnArg, Token![,]> = &item_fn.sig.inputs;
    for input in inputs {
        if let syn::FnArg::Typed(pat_type) = input {
            let param_type: &Type = &pat_type.ty;
            if let Type::Path(type_path) = param_type
                && let Some(segment) = type_path.path.segments.last()
                && segment.ident == VIRTUAL_NODE_TYPE
            {
                if let syn::PathArguments::AngleBracketed(args) = &segment.arguments
                    && let Some(syn::GenericArgument::Type(inner_param_type)) = args.args.first()
                    && let Type::Path(inner_path) = inner_param_type
                    && let Some(inner_segment) = inner_path.path.segments.last()
                {
                    return inner_segment.ident.to_string();
                }
            } else if let Type::Path(type_path) = param_type
                && let Some(segment) = type_path.path.segments.last()
            {
                return segment.ident.to_string();
            }
        }
    }
    String::new()
}

/// Checks whether a double-brace pattern `{{ ... }}` represents a dynamic tag
/// rather than a simple braced expression.
///
/// A dynamic tag is detected when the second brace group contains:
/// - Empty content, or
/// - An identifier followed by `:` or `-` (attribute pattern), or
/// - Keywords `if`, `match`, `for`, or
/// - A string literal, or
/// - A braced expression followed by `:` (dynamic key), or
/// - Another double brace (nested dynamic tag).
///
/// # Arguments
///
/// - `&ParseBuffer` - The parse buffer of the second brace group.
/// - `&ParseStream` - The outer parse stream (for `peek2` checks).
///
/// # Returns
///
/// - `bool` - `true` if the pattern is a dynamic tag.
pub(crate) fn is_dynamic_tag_pattern(second_brace: ParseStream, outer: ParseStream) -> bool {
    second_brace.is_empty()
        || (second_brace.peek(Ident)
            && (second_brace.peek2(Colon) || second_brace.peek2(Token![-])))
        || second_brace.peek(Token![if])
        || second_brace.peek(Token![match])
        || second_brace.peek(Token![for])
        || second_brace.peek(LitStr)
        || (second_brace.peek(Brace) && outer.peek2(Colon))
        || (second_brace.peek(Brace) && second_brace.peek2(Brace))
}

/// Parses a stream of tokens into a list of HTML child nodes.
///
/// # Arguments
///
/// - `ParseStream` - The parse stream containing HTML child content.
///
/// # Returns
///
/// - `syn::Result<Vec<HtmlNode>>` - The parsed list of HTML child nodes, or a syntax error.
pub(crate) fn parse_html_children(content: ParseStream) -> syn::Result<Vec<HtmlNode>> {
    let mut children: Vec<HtmlNode> = Vec::new();
    while !content.is_empty() {
        if content.peek(Brace) && content.peek2(Brace) {
            let forked: ParseBuffer<'_> = content.fork();
            let _first_brace: ParseBuffer<'_>;
            braced!(_first_brace in forked);
            let second_brace: ParseBuffer<'_>;
            braced!(second_brace in forked);
            if is_dynamic_tag_pattern(&second_brace, content) {
                let tag_content: ParseBuffer<'_>;
                braced!(tag_content in content);
                let tag_expr: Expr = tag_content.parse()?;
                let body_content: ParseBuffer<'_>;
                braced!(body_content in content);
                let (dynamic_attrs, dynamic_children): (HtmlAttrs, Vec<HtmlNode>) =
                    parse_dynamic_component_children(&body_content)?;
                children.push(HtmlNode::DynamicTag(HtmlDynamicTag::new(
                    tag_expr,
                    dynamic_attrs,
                    dynamic_children,
                )));
            } else {
                let child_content: ParseBuffer<'_>;
                braced!(child_content in content);
                let expr: Expr = child_content.parse()?;
                children.push(HtmlNode::Dynamic(expr));
            }
        } else if content.peek(LitStr) && content.peek2(Brace) {
            let element: HtmlElement = content.parse()?;
            children.push(HtmlNode::Element(element));
        } else if content.peek(LitStr) {
            let literal_string: LitStr = content.parse()?;
            children.push(HtmlNode::Text(literal_string.value()));
        } else if content.peek(Token![if]) {
            let html_if: HtmlIf = content.parse()?;
            children.push(HtmlNode::If(html_if));
        } else if content.peek(Token![match]) {
            let html_match: HtmlMatch = content.parse()?;
            children.push(HtmlNode::Match(html_match));
        } else if content.peek(Token![for]) {
            let html_for: HtmlFor = content.parse()?;
            children.push(HtmlNode::For(html_for));
        } else if content.peek(Brace) {
            let child_content: ParseBuffer<'_>;
            braced!(child_content in content);
            let expr: Expr = child_content.parse()?;
            children.push(HtmlNode::Dynamic(expr));
        } else if (content.peek(Ident) || content.peek(LitStr))
            && content.peek2(Colon)
            && !is_double_colon(content)
        {
            break;
        } else if content.peek(Ident) {
            if content.peek2(Brace) {
                let element: HtmlElement = content.parse()?;
                children.push(HtmlNode::Element(element));
            } else {
                let expr: Expr = content.parse()?;
                children.push(HtmlNode::Expr(expr));
            }
        } else {
            return Err(content.error(ERR_UNEXPECTED_TOKEN_IN_HTML));
        }
    }
    Ok(children)
}

/// Parses the body of a match arm after the `=>` token.
///
/// Unlike `parse_html_children` which operates on a braced scope, this function
/// reads directly from the arms content stream and stops when it encounters a
/// top-level comma (indicating the next arm) or the end of the stream.
/// Supports all HTML node types: elements, text, expressions, if, match, for,
/// and braced dynamic expressions.
///
/// # Arguments
///
/// - `ParseStream` - The parse stream positioned after `=>` in a match arm.
///
/// # Returns
///
/// - `syn::Result<Vec<HtmlNode>>` - The parsed list of HTML nodes for the arm body.
pub(crate) fn parse_match_arm_body(content: ParseStream) -> syn::Result<Vec<HtmlNode>> {
    if content.peek(Brace) {
        let child_content: ParseBuffer<'_>;
        braced!(child_content in content);
        parse_html_children(&child_content)
    } else {
        let node: HtmlNode = content.parse()?;
        Ok(vec![node])
    }
}

/// Parses the body of a dynamic component `@ {expr} { ... }`.
///
/// The body contains attributes (key: value) and children (HTML nodes),
/// similar to an `HtmlElement` body but without a tag name.
/// Attributes are recognized by the pattern `ident:` or `ident-...:`.
/// Everything else is treated as child content.
///
/// # Arguments
///
/// - `ParseStream` - The parse stream containing the dynamic component body.
///
/// # Returns
///
/// - `syn::Result<(HtmlAttrs, Vec<HtmlNode>)>` - The parsed attributes and children.
pub(crate) fn parse_dynamic_component_children(
    content: ParseStream,
) -> syn::Result<(HtmlAttrs, Vec<HtmlNode>)> {
    let mut attributes: HtmlAttrs = Vec::new();
    let mut children: Vec<HtmlNode> = Vec::new();
    while !content.is_empty() {
        if content.peek(Brace) && content.peek2(Brace) {
            let forked: ParseBuffer<'_> = content.fork();
            let _first_brace: ParseBuffer<'_>;
            braced!(_first_brace in forked);
            let second_brace: ParseBuffer<'_>;
            braced!(second_brace in forked);
            if is_dynamic_tag_pattern(&second_brace, content) {
                let tag_content: ParseBuffer<'_>;
                braced!(tag_content in content);
                let tag_expr: Expr = tag_content.parse()?;
                let body_content: ParseBuffer<'_>;
                braced!(body_content in content);
                let (dynamic_attrs, dynamic_children): (HtmlAttrs, Vec<HtmlNode>) =
                    parse_dynamic_component_children(&body_content)?;
                children.push(HtmlNode::DynamicTag(HtmlDynamicTag::new(
                    tag_expr,
                    dynamic_attrs,
                    dynamic_children,
                )));
            } else {
                let child_content: ParseBuffer<'_>;
                braced!(child_content in content);
                let expr: Expr = child_content.parse()?;
                children.push(HtmlNode::Dynamic(expr));
            }
        } else if content.peek(Token![if]) {
            let html_if: HtmlIf = content.parse()?;
            children.push(HtmlNode::If(html_if));
        } else if content.peek(Token![match]) {
            let html_match: HtmlMatch = content.parse()?;
            children.push(HtmlNode::Match(html_match));
        } else if content.peek(Token![for]) {
            let html_for: HtmlFor = content.parse()?;
            children.push(HtmlNode::For(html_for));
        } else if content.peek(Brace) && content.peek2(Colon) {
            let key_content: ParseBuffer<'_>;
            braced!(key_content in content);
            let key_expr: Expr = key_content.parse()?;
            content.parse::<Colon>()?;
            let value: HtmlAttrValue = parse_attr_value(content, STR_EMPTY)?;
            attributes.push((key_expr.to_token_stream(), value));
        } else if content.peek(Brace) {
            let child_content: ParseBuffer<'_>;
            braced!(child_content in content);
            let expr: Expr = child_content.parse()?;
            children.push(HtmlNode::Dynamic(expr));
        } else if content.peek(LitStr) && content.peek2(Brace) {
            let element: HtmlElement = content.parse()?;
            children.push(HtmlNode::Element(element));
        } else if content.peek(LitStr) && content.peek2(Colon) {
            let key_literal: LitStr = content.parse()?;
            let key_str: String = key_literal.value();
            content.parse::<Colon>()?;
            let value: HtmlAttrValue = parse_attr_value(content, &key_str)?;
            attributes.push((key_literal.to_token_stream(), value));
        } else if content.peek(Ident)
            && (content.peek2(Colon) || content.peek2(Token![-]))
            && !is_double_colon(content)
        {
            let key_string: String = parse_kebab_name(content)?;
            let key_literal: LitStr = LitStr::new(&key_string, content.span());
            content.parse::<Colon>()?;
            let key_str: String = key_string
                .strip_prefix(RAW_IDENT_PREFIX)
                .unwrap_or(&key_string)
                .to_string();
            let value: HtmlAttrValue = parse_attr_value(content, &key_str)?;
            attributes.push((key_literal.to_token_stream(), value));
        } else if content.peek(LitStr) {
            let literal_string: LitStr = content.parse()?;
            children.push(HtmlNode::Text(literal_string.value()));
        } else if content.peek(Ident) {
            if content.peek2(Brace) {
                let element: HtmlElement = content.parse()?;
                children.push(HtmlNode::Element(element));
            } else {
                let expr: Expr = content.parse()?;
                children.push(HtmlNode::Expr(expr));
            }
        } else {
            return Err(content.error(ERR_UNEXPECTED_TOKEN_IN_DYNAMIC_COMPONENT));
        }
    }
    let merged_attributes: HtmlAttrs = merge_same_key_attributes(attributes);
    Ok((merged_attributes, children))
}

/// Converts a slice of `HtmlNode` children into a `Vec<proc_macro2::TokenStream>`.
///
/// Shared helper used by both `children_to_node_tokens` and `children_to_tokens`.
///
/// # Arguments
///
/// - `&[HtmlNode]` - The slice of HTML child nodes to convert.
///
/// # Returns
///
/// - `Vec<proc_macro2::TokenStream>` - The generated token stream representing a single `VirtualNode`.
pub(crate) fn nodes_to_token_vec(children: &[HtmlNode]) -> Vec<proc_macro2::TokenStream> {
    children
        .iter()
        .map(|child: &HtmlNode| {
            let mut token_stream: proc_macro2::TokenStream = proc_macro2::TokenStream::new();
            child.to_tokens(&mut token_stream);
            token_stream
        })
        .collect()
}

/// Converts a list of `HtmlNode` children into a single `VirtualNode` token stream.
///
/// - 0 children → `VirtualNode::Empty`
/// - 1 child → the child's token stream directly (no Fragment wrapper)
/// - N children → `VirtualNode::Fragment(vec![...])`
///
/// # Arguments
///
/// - `&[HtmlNode]` - The slice of HTML child nodes to convert.
///
/// # Returns
///
/// - `proc_macro2::TokenStream` - The generated token stream representing a single `VirtualNode`.
pub(crate) fn children_to_node_tokens(children: &[HtmlNode]) -> proc_macro2::TokenStream {
    match children.len() {
        0 => quote! { ::euv::VirtualNode::Empty },
        1 => {
            let mut token_stream: proc_macro2::TokenStream = proc_macro2::TokenStream::new();
            children[0].to_tokens(&mut token_stream);
            token_stream
        }
        _ => {
            let child_tokens: Vec<proc_macro2::TokenStream> = nodes_to_token_vec(children);
            quote! { ::euv::VirtualNode::Fragment(vec![#(#child_tokens), *]) }
        }
    }
}

/// Converts a list of `HtmlNode` children into a `Vec<VirtualNode>` token stream.
///
/// Always produces `vec![...]` format, used by `for` loops where the body
/// is collected and then extended into an accumulator.
///
/// # Arguments
///
/// - `&[HtmlNode]` - The slice of HTML child nodes to convert.
///
/// # Returns
///
/// - `proc_macro2::TokenStream` - The generated token stream representing a `Vec<VirtualNode>`.
pub(crate) fn children_to_tokens(children: &[HtmlNode]) -> proc_macro2::TokenStream {
    let child_tokens: Vec<proc_macro2::TokenStream> = nodes_to_token_vec(children);
    quote! { vec![#(#child_tokens), *] }
}

/// Parses a reactive `if {expr} { value } [else if {expr} { value }]* [else { value }]` in attribute value position.
///
/// Unlike `HtmlIf` (which contains HTML child nodes), each branch body here is a Rust expression.
///
/// # Arguments
///
/// - `ParseStream` - The parse stream positioned at the `if` keyword.
///
/// # Returns
///
/// - `syn::Result<HtmlAttrIf>` - The parsed attribute-level reactive conditional.
pub(crate) fn parse_attr_if(content: ParseStream) -> syn::Result<HtmlAttrIf> {
    let mut branches: Vec<(Option<Expr>, Expr)> = Vec::new();
    content.parse::<Token![if]>()?;
    let cond_content: ParseBuffer<'_>;
    braced!(cond_content in content);
    let condition: Expr = cond_content.parse()?;
    let body_content: ParseBuffer<'_>;
    braced!(body_content in content);
    let body: Expr = body_content.parse()?;
    branches.push((Some(condition), body));
    while content.peek(Token![else]) {
        content.parse::<Token![else]>()?;
        if content.peek(Token![if]) {
            content.parse::<Token![if]>()?;
            let cond_content: ParseBuffer<'_>;
            braced!(cond_content in content);
            let condition: Expr = cond_content.parse()?;
            let body_content: ParseBuffer<'_>;
            braced!(body_content in content);
            let body: Expr = body_content.parse()?;
            branches.push((Some(condition), body));
        } else {
            let body_content: ParseBuffer<'_>;
            braced!(body_content in content);
            let body: Expr = body_content.parse()?;
            branches.push((None, body));
            break;
        }
    }
    Ok(HtmlAttrIf { branches })
}

/// Strips outer braces from an `Expr` if it is an `Expr::Block` with a single expression,
/// avoiding Rust `unused_braces` warnings in generated `if` conditions.
///
/// # Arguments
///
/// - `&Expr` - The expression to potentially strip.
///
/// # Returns
///
/// - `&Expr` - The inner expression if the input was a braced single-expression block, otherwise the original.
pub(crate) fn strip_braces_from_expr(expr: &Expr) -> &Expr {
    if let Expr::Block(expr_block) = expr {
        let stmts: &Vec<Stmt> = &expr_block.block.stmts;
        if stmts.len() == 1
            && let Stmt::Expr(inner, None) = &stmts[0]
        {
            return inner;
        }
    }
    expr
}

/// Generates a token stream for an `HtmlAttrIf` as a Rust `if` expression.
///
/// The generated code is used inside a reactive closure so that when signals
/// change, the conditional is re-evaluated.
///
/// # Arguments
///
/// - `&HtmlAttrIf` - The parsed attribute-level reactive conditional.
/// - `proc_macro2::TokenStream` - The default else branch token stream, used when no explicit else branch exists.
///
/// # Returns
///
/// - `proc_macro2::TokenStream` - The generated `if ... { ... } else if ... { ... } else { ... }` token stream.
pub(crate) fn attr_if_to_tokens(
    html_attr_if: &HtmlAttrIf,
    else_default: proc_macro2::TokenStream,
) -> proc_macro2::TokenStream {
    let mut if_chain: proc_macro2::TokenStream = proc_macro2::TokenStream::new();
    let has_else: bool = html_attr_if
        .branches
        .last()
        .is_some_and(|(condition, _): &(Option<Expr>, Expr)| condition.is_none());
    for (branch_index, (condition, body)) in html_attr_if.branches.iter().enumerate() {
        match (branch_index, condition) {
            (0, Some(cond)) => {
                if_chain.extend(quote! { if #cond { #body } });
            }
            (_, Some(cond)) => {
                if_chain.extend(quote! { else if #cond { #body } });
            }
            (_, None) => {
                if_chain.extend(quote! { else { #body } });
            }
        }
    }
    if !has_else {
        if_chain.extend(quote! { else { #else_default } });
    }
    if_chain
}

/// Builds a Rust `if/else if/else` chain token stream from `HtmlIf` branches.
///
/// Each branch body is converted to a `VirtualNode` token stream via `children_to_node_tokens`.
/// Used by `HtmlNode::If` in `ToTokens`.
///
/// # Arguments
///
/// - `&[(Option<Expr>, Vec<HtmlNode>)]` - The branches from an `HtmlIf`.
///
/// # Returns
///
/// - `proc_macro2::TokenStream` - The generated if-chain token stream.
pub(crate) fn build_html_if_chain(
    branches: &[(Option<Expr>, Vec<HtmlNode>)],
) -> proc_macro2::TokenStream {
    let mut if_chain: proc_macro2::TokenStream = proc_macro2::TokenStream::new();
    let has_else: bool = branches
        .last()
        .is_some_and(|(condition, _): &(Option<Expr>, Vec<HtmlNode>)| condition.is_none());
    for (branch_index, (condition, body)) in branches.iter().enumerate() {
        let body_expr: proc_macro2::TokenStream = children_to_node_tokens(body);
        match (branch_index, condition) {
            (0, Some(cond)) => {
                if_chain.extend(quote! { if #cond { #body_expr } });
            }
            (_, Some(cond)) => {
                if_chain.extend(quote! { else if #cond { #body_expr } });
            }
            (_, None) => {
                if_chain.extend(quote! { else { #body_expr } });
            }
        }
    }
    if !has_else {
        if_chain.extend(quote! { else { ::euv::VirtualNode::Empty } });
    }
    if_chain
}

/// Parses the value side of an attribute, handling the special `style:` attribute.
///
/// If the key is `"style"` and the value is a braced expression that looks like
/// a style object (key-value pairs separated by `;`), it is parsed as
/// `HtmlAttrValue::Style`. Otherwise, the value is parsed as a normal expression
/// or a reactive `if` conditional.
///
/// # Arguments
///
/// - `ParseStream` - The parse stream positioned after the ` -` token.
/// - `&str` - The attribute key string (e.g., `"style"`, `"class"`).
///
/// # Returns
///
/// - `syn::Result<HtmlAttrValue>` - The parsed attribute value.
pub(crate) fn parse_attr_value(content: ParseStream, key_str: &str) -> syn::Result<HtmlAttrValue> {
    if content.peek(Token![if]) {
        return Ok(HtmlAttrValue::If(parse_attr_if(content)?));
    }
    if key_str == ATTR_KEY_STYLE && content.peek(Brace) {
        let style_content: ParseBuffer<'_>;
        braced!(style_content in content);
        let is_style_object: bool = style_content.peek(LitStr) || style_content.peek(Ident);
        if is_style_object {
            let mut style_props: Vec<(String, HtmlStylePropValue)> = Vec::new();
            while !style_content.is_empty() {
                let css_key: String = parse_kebab_name(&style_content)?;
                style_content.parse::<Colon>()?;
                let prop_value: HtmlStylePropValue = if style_content.peek(Token![if]) {
                    let html_attr_if: HtmlAttrIf = parse_attr_if(&style_content)?;
                    HtmlStylePropValue::If(html_attr_if)
                } else if style_content.peek(LitStr) {
                    let literal_string: LitStr = style_content.parse()?;
                    HtmlStylePropValue::Literal(literal_string.value())
                } else if style_content.peek(Brace) {
                    let expr_content: ParseBuffer<'_>;
                    braced!(expr_content in style_content);
                    if expr_content.peek(Token![if]) {
                        let html_attr_if: HtmlAttrIf = parse_attr_if(&expr_content)?;
                        HtmlStylePropValue::If(html_attr_if)
                    } else {
                        let expr: Expr = expr_content.parse()?;
                        HtmlStylePropValue::Expr(expr)
                    }
                } else {
                    let expr: Expr = style_content.parse()?;
                    HtmlStylePropValue::Expr(expr)
                };
                style_props.push((css_key, prop_value));
                if style_content.peek(Semi) {
                    style_content.parse::<Semi>()?;
                }
            }
            Ok(HtmlAttrValue::Style(style_props))
        } else {
            Ok(HtmlAttrValue::Expr(style_content.parse()?))
        }
    } else {
        Ok(HtmlAttrValue::Expr(content.parse()?))
    }
}

/// Merges attributes with the same key name for `class` and `style`.
///
/// When multiple `class:` or `style:` attributes are declared on the same
/// element, they are combined into a single `HtmlAttrValue::Classes` or
/// `HtmlAttrValue::Styles` entry so that the renderer can merge their
/// values at runtime rather than overwriting.
///
/// Non-mergeable attribute keys keep only the last occurrence.
///
/// # Arguments
///
/// - `Vec<(Ident, HtmlAttrValue)>` - The raw parsed attributes (may contain duplicate keys).
///
/// # Returns
///
/// - `Vec<(Ident, HtmlAttrValue)>` - The merged attributes with at most one `class` and one `style` entry.
pub(crate) fn merge_same_key_attributes(attributes: HtmlAttrs) -> HtmlAttrs {
    let mut class_values: Vec<HtmlAttrValue> = Vec::new();
    let mut style_values: Vec<HtmlAttrValue> = Vec::new();
    let mut result: HtmlAttrs = Vec::new();
    for (key, value) in attributes {
        let key_string: String = extract_attr_key_string(&key);
        if key_string == ATTR_KEY_CLASS {
            class_values.push(value);
        } else if key_string == ATTR_KEY_STYLE {
            style_values.push(value);
        } else {
            result.push((key, value));
        }
    }
    let push_merged = |result: &mut HtmlAttrs,
                       key_str: &str,
                       mut values: Vec<HtmlAttrValue>,
                       wrap: fn(Vec<HtmlAttrValue>) -> HtmlAttrValue|
     -> () {
        match values.len() {
            0 => {}
            1 => result.push((
                LitStr::new(key_str, proc_macro2::Span::call_site()).to_token_stream(),
                values.remove(0),
            )),
            _ => result.push((
                LitStr::new(key_str, proc_macro2::Span::call_site()).to_token_stream(),
                wrap(values),
            )),
        }
    };
    push_merged(
        &mut result,
        ATTR_KEY_CLASS,
        class_values,
        HtmlAttrValue::Classes,
    );
    push_merged(
        &mut result,
        ATTR_KEY_STYLE,
        style_values,
        HtmlAttrValue::Styles,
    );
    result
}

/// Converts an `HtmlAttrValue` into a token stream that produces an `AttributeValue`.
///
/// This function mirrors the logic in `HtmlElement::ToTokens` for converting
/// attribute values, but always wraps the result as an `AttributeValue` variant
/// suitable for passing to `AttributeValue::merge_class`.
///
/// # Arguments
///
/// - `&HtmlAttrValue` - The attribute value to convert.
/// - `&str` - The attribute key name (used for event detection).
/// - `bool` - Whether this is a component attribute.
///
/// # Returns
///
/// - `proc_macro2::TokenStream` - Token stream that evaluates to an `AttributeValue`.
pub(crate) fn attr_value_to_attribute_value_tokens(
    value: &HtmlAttrValue,
    key_str: &str,
    is_component: bool,
) -> proc_macro2::TokenStream {
    match value {
        HtmlAttrValue::Expr(expr) => {
            if let Some(event_name_str) = key_str.strip_prefix(EVENT_ATTR_PREFIX) {
                if is_component {
                    quote! {
                        ::euv::AttrValueAdapter::new(#expr).into_callback_attribute_value_with_name(#key_str)
                    }
                } else {
                    quote! {
                        ::euv::EventAdapter::new(#expr).into_attribute(#event_name_str)
                    }
                }
            } else if key_str == ATTR_KEY_CHILDREN {
                quote! { ::euv::AttributeValue::Dynamic(Box::new(#expr)) }
            } else {
                quote! {
                    ::euv::AttrValueAdapter::new(#expr).into_reactive_attribute_value()
                }
            }
        }
        HtmlAttrValue::If(_) => {
            quote! { #value }
        }
        HtmlAttrValue::Style(props) => {
            let has_if: bool =
                props
                    .iter()
                    .any(|(_, style_value): &(String, HtmlStylePropValue)| {
                        matches!(style_value, HtmlStylePropValue::If(_))
                    });
            if has_if {
                quote! { #value }
            } else {
                quote! { ::euv::AttributeValue::Text(#value) }
            }
        }
        HtmlAttrValue::Classes(_) | HtmlAttrValue::Styles(_) => {
            quote! { #value }
        }
    }
}

/// Converts a style-related `HtmlAttrValue` into a token stream that produces
/// an `AttributeValue`.
///
/// Style values are wrapped in `AttributeValue::Text(...)` for static strings,
/// or kept as `AttributeValue::Signal(...)` for reactive style attributes.
///
/// # Arguments
///
/// - `&HtmlAttrValue` - The style attribute value to convert.
///
/// # Returns
///
/// - `proc_macro2::TokenStream` - Token stream that evaluates to an `AttributeValue`.
pub(crate) fn style_value_to_attribute_value_tokens(
    value: &HtmlAttrValue,
) -> proc_macro2::TokenStream {
    match value {
        HtmlAttrValue::Style(props) => {
            let has_if: bool =
                props
                    .iter()
                    .any(|(_, style_value): &(String, HtmlStylePropValue)| {
                        matches!(style_value, HtmlStylePropValue::If(_))
                    });
            if has_if {
                quote! { #value }
            } else {
                quote! { ::euv::AttributeValue::Text(#value) }
            }
        }
        HtmlAttrValue::If(_) => {
            quote! { #value }
        }
        HtmlAttrValue::Expr(expr) => {
            quote! { ::euv::AttributeValue::Text(#expr.to_string()) }
        }
        HtmlAttrValue::Classes(_) | HtmlAttrValue::Styles(_) => {
            quote! { #value }
        }
    }
}

/// Extracts the clean attribute key string from a token stream.
///
/// Handles two token formats:
/// - `Ident` tokens: `key.to_string()` may include `r#` prefix which is stripped.
/// - `LitStr` tokens: `key.to_string()` includes surrounding quotes which are stripped.
///
/// # Arguments
///
/// - `&proc_macro2::TokenStream` - The token stream representing an attribute key.
///
/// # Returns
///
/// - `String` - The clean attribute key string.
pub(crate) fn extract_attr_key_string(key: &proc_macro2::TokenStream) -> String {
    let raw: String = key.to_string().replace(CHAR_SPACE, STR_EMPTY);
    if raw.starts_with(CHAR_DOUBLE_QUOTE) && raw.ends_with(CHAR_DOUBLE_QUOTE) {
        raw[1..raw.len() - 1].to_string()
    } else {
        raw.strip_prefix(RAW_IDENT_PREFIX)
            .unwrap_or(&raw)
            .to_string()
    }
}