ortho_config_macros 0.9.0

//! Input parsing for the `OrthoConfig` derive macro.
//!
//! This module gathers the struct identifier, fields, and relevant attribute
//! metadata in one pass so macro expansion can fail fast with useful errors.

use syn::{Data, DeriveInput, Fields};

use super::{FieldAttrs, StructAttrs, parse_field_attrs, parse_struct_attrs};

/// Gathers information from the user-provided struct.
///
/// The helper collects the struct identifier, its fields, and all
/// attribute metadata in one pass. Returning these components together
/// keeps the `derive` implementation simple and validates invalid input
/// eagerly so expansion can fail fast.
///
/// The returned tuple contains:
/// - `ident`: the struct identifier
/// - `fields`: the struct's fields
/// - `struct_attrs`: parsed struct-level attributes
/// - `field_attrs`: parsed field-level attributes
pub(crate) fn parse_input(
    input: &DeriveInput,
) -> Result<(syn::Ident, Vec<syn::Field>, StructAttrs, Vec<FieldAttrs>), syn::Error> {
    let ident = input.ident.clone();
    let struct_attrs = parse_struct_attrs(&input.attrs)?;
    let fields = match &input.data {
        Data::Struct(data) => match &data.fields {
            Fields::Named(named) => named.named.iter().cloned().collect::<Vec<_>>(),
            _ => {
                return Err(syn::Error::new_spanned(
                    data.struct_token,
                    "OrthoConfig requires named fields",
                ));
            }
        },
        _ => {
            return Err(syn::Error::new_spanned(
                ident.clone(),
                "OrthoConfig can only be derived for structs",
            ));
        }
    };

    let mut field_attrs = Vec::new();
    for f in &fields {
        field_attrs.push(parse_field_attrs(f)?);
    }
    Ok((ident, fields, struct_attrs, field_attrs))
}