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use proc_macro::TokenStream;
use quote::{quote, quote_spanned, ToTokens};
use syn::{
parse_macro_input, spanned::Spanned, AttributeArgs, Block, Ident, ItemFn, Lit, Meta, NestedMeta,
};
macro_rules! option_string_to_token_stream {
($opt_string:expr) => {
match $opt_string {
Some(string) => quote! {
Some(String::from(#string))
},
None => quote! {
None
},
}
};
}
fn quote_without_return(ident: &Ident, block: &Block, crab_meta: ImportOptions) -> TokenStream {
let name = crab_meta.name.unwrap_or_else(|| ident.to_string());
let scope = option_string_to_token_stream!(crab_meta.scope);
quote! {
fn #ident() -> crabzilla::ImportedFn {
crabzilla::create_sync_fn(
|args: Vec<crabzilla::Value>| -> std::result::Result<crabzilla::Value, crabzilla::AnyError> {
Ok(#block)
},
#name,
#scope,
)
}
}.into()
}
fn quote_with_return(ident: &Ident, block: &Block, crab_meta: ImportOptions) -> TokenStream {
let name = crab_meta.name.unwrap_or_else(|| ident.to_string());
let scope = option_string_to_token_stream!(crab_meta.scope);
quote! {
fn #ident() -> crabzilla::ImportedFn {
crabzilla::create_sync_fn(
|args: Vec<crabzilla::Value>| -> std::result::Result<crabzilla::Value, crabzilla::AnyError> {
#block
Ok(crabzilla::Value::Null)
},
#name,
#scope,
)
}
}.into()
}
fn error<T: Spanned>(item: T, msg: &str) -> TokenStream {
let span = item.span();
let error = quote_spanned! {
span => compile_error!(#msg);
};
error.into()
}
#[derive(Default)]
struct ImportOptions {
scope: Option<String>,
name: Option<String>,
}
fn validate_literal(name: &str) -> bool {
if name.is_empty() {
return false;
}
for char in name.chars() {
if !char.is_ascii() {
return false;
}
if char.is_whitespace() {
return false;
}
}
true
}
fn parse_meta(metas: Vec<NestedMeta>) -> Result<ImportOptions, TokenStream> {
let mut options = ImportOptions::default();
for meta in metas {
match meta {
NestedMeta::Meta(meta) => match meta {
Meta::NameValue(meta_name_value) => {
let string = meta_name_value.path.to_token_stream().to_string();
match string.as_str() {
"scope" => match meta_name_value.lit {
Lit::Str(lit_str) => {
let scope = lit_str.value();
if !validate_literal(&scope) {
return Err(error(lit_str, "Invalid scope"));
}
options.scope = Some(scope);
}
_ => return Err(error(meta_name_value.lit, "Unsupported value")),
},
"name" => match meta_name_value.lit {
Lit::Str(lit_str) => {
let name = lit_str.value();
if !validate_literal(&name) {
return Err(error(lit_str, "Invalid name"));
}
options.name = Some(lit_str.value());
}
_ => return Err(error(meta_name_value.lit, "Unsupported value")),
},
_ => return Err(error(meta_name_value, "Unsupported meta")),
}
}
_ => return Err(error(meta, "Unsupported meta")),
},
_ => return Err(error(meta, "Unsupported meta")),
}
}
Ok(options)
}
#[proc_macro_attribute]
pub fn import_fn(attr: TokenStream, item: TokenStream) -> TokenStream {
let input = parse_macro_input!(item as ItemFn);
let attr = parse_macro_input!(attr as AttributeArgs);
let crab_meta = match parse_meta(attr) {
Ok(crab_meta) => crab_meta,
Err(error) => return error,
};
match input.sig.inputs.to_token_stream().to_string().as_str() {
"" | "args : Vec < Value >" | "args : Vec < crabzilla :: Value >" => {}
"args : std :: vec :: Vec < Value >" => {}
"args : std :: vec :: Vec < crabzilla :: Value >" => {}
"args : :: vec :: Vec < Value >" => {}
"args : :: vec :: Vec < crabzilla :: Value >" => {}
_ => {
return error(
input.sig.inputs,
"Illegal arguments, should be empty or \"args: Vec<Value>\"",
)
}
}
match input.sig.output.to_token_stream().to_string().as_str() {
"-> crabzilla :: Value" | "-> Value" => {
quote_without_return(&input.sig.ident, &input.block, crab_meta)
}
"-> ()" | "" => quote_with_return(&input.sig.ident, &input.block, crab_meta),
_ => error(
input.sig.output,
"Illegal return type, should be empty or \"Value\"",
),
}
}