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use quote::ToTokens;
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;
use syn::spanned::Spanned;
use syn::{bracketed, parenthesized, token, Error, Expr, Ident, Lit, LitStr, Path, Result, Token};
use crate::widgets::{Attr, Attrs};
impl Parse for Attrs {
fn parse(input: ParseStream<'_>) -> Result<Self> {
let mut attrs = Vec::new();
while input.peek(Token![#]) {
let _sharp: Token![#] = input.parse()?;
let attr_tokens;
bracketed!(attr_tokens in input);
let path: Path = attr_tokens.parse()?;
attrs.push(if attr_tokens.is_empty() {
if let Some(ident) = path.get_ident() {
if ident == "local" {
Attr::Local(ident.clone())
} else if ident == "local_ref" {
Attr::LocalRef(ident.clone())
} else if ident == "root" {
Attr::Root(ident.clone())
} else if ident == "watch" {
Attr::Watch(ident.clone())
} else if ident == "track" {
Attr::Track(ident.clone(), None)
} else if ident == "iterate" {
Attr::Iterate(ident.clone())
} else if ident == "template" {
Attr::Template(ident.clone())
} else if ident == "template_child" {
Attr::TemplateChild(ident.clone())
} else {
return Err(unexpected_attr_name(ident));
}
} else {
return Err(Error::new(path.span(), "Expected identifier."));
}
} else if attr_tokens.peek(token::Paren) {
let paren_input;
parenthesized!(paren_input in attr_tokens);
let nested: Punctuated<Expr, token::Comma> =
Punctuated::parse_terminated(&paren_input)?;
if let Some(ident) = path.get_ident() {
if ident == "block_signal" {
let mut signal_idents = Vec::with_capacity(nested.len());
for expr in nested {
let ident = expect_ident_from_expr(&expr)?;
signal_idents.push(ident);
}
Attr::BlockSignal(ident.clone(), signal_idents)
} else if ident == "track" {
let expr = expect_one_nested_expr(&nested)?;
Attr::Track(ident.clone(), Some(Box::new(expr.clone())))
} else if ident == "transition" {
let expr = expect_one_nested_expr(&nested)?;
let ident = expect_ident_from_expr(expr)?;
Attr::Transition(ident.clone(), ident)
} else if ident == "name" {
let expr = expect_one_nested_expr(&nested)?;
let ident = expect_ident_from_expr(expr)?;
Attr::Name(ident.clone(), ident)
} else if ident == "wrap" {
let expr = expect_one_nested_expr(&nested)?;
let path = expect_path_from_expr(expr)?;
Attr::Wrap(ident.clone(), path)
} else if ident == "chain" {
let expr = expect_one_nested_expr(&nested)?;
Attr::Chain(ident.clone(), Box::new(expr.clone()))
} else {
return Err(unexpected_attr_name(ident));
}
} else {
return Err(Error::new(path.span(), "Expected identifier."));
}
} else if attr_tokens.peek(Token![=]) {
let _eq: Token![=] = attr_tokens.parse()?;
let lit = attr_tokens.parse()?;
if let Some(ident) = path.get_ident() {
if ident == "track" {
let string = expect_string_lit(&lit)?;
Attr::Track(ident.clone(), Some(string.parse()?))
} else if ident == "doc" {
Attr::Doc(lit.into_token_stream())
} else if ident == "transition" {
let string = expect_string_lit(&lit)?;
Attr::Transition(ident.clone(), string.parse()?)
} else if ident == "name" {
let string = expect_string_lit(&lit)?;
Attr::Name(ident.clone(), string.parse()?)
} else {
return Err(unexpected_attr_name(ident));
}
} else {
return Err(Error::new(path.span(), "Expected identifier."));
}
} else {
return Err(Error::new(attr_tokens.span(), "Expected `]`, `(` or `=`."));
});
}
Ok(Attrs { inner: attrs })
}
}
fn unexpected_attr_name(ident: &Ident) -> Error {
Error::new(
ident.span(),
format!("Unexpected attribute name `{ident}`."),
)
}
fn expect_string_lit(lit: &Lit) -> Result<&LitStr> {
if let Lit::Str(string) = lit {
Ok(string)
} else {
Err(Error::new(
lit.span(),
"Expected string literal. Try this: `\"value\"`.",
))
}
}
fn expect_path_from_expr(expr: &Expr) -> Result<Path> {
if let Expr::Path(path) = expr {
Ok(path.path.clone())
} else {
Err(Error::new(
expr.span(),
format!("Expected path `{}`.", expr.to_token_stream()),
))
}
}
fn expect_ident_from_expr(expr: &Expr) -> Result<Ident> {
if let Expr::Path(path) = expr {
expect_ident_from_path(&path.path)
} else {
Err(Error::new(
expr.span(),
format!("Expected identifier `{}`.", expr.to_token_stream()),
))
}
}
fn expect_ident_from_path(path: &Path) -> Result<Ident> {
if let Some(ident) = path.get_ident() {
Ok(ident.clone())
} else {
Err(Error::new(path.span(), "Expected identifier."))
}
}
fn expect_one_nested_expr(nested: &Punctuated<Expr, token::Comma>) -> Result<&Expr> {
if nested.len() == 1 {
Ok(nested.first().unwrap())
} else {
Err(Error::new(nested.span(), "Expected only one expression."))
}
}