derive_http/src/lib.rs

use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, DeriveInput, Data, Fields, Lit};

#[proc_macro_derive(HttpGetRequest, attributes(http_get))]
pub fn derive_http_get_request(input: TokenStream) -> TokenStream {
    let input = parse_macro_input!(input as DeriveInput);
    let name = &input.ident;

    // Parse #[http_get(url = "...")] attribute
    let mut base_url = None;
    for attr in &input.attrs {
        if attr.path().is_ident("http_get") {
            let _ = attr.parse_nested_meta(|meta| {
                if meta.path.is_ident("url") {
                    let value: Lit = meta.value()?.parse()?;
                    if let Lit::Str(litstr) = value {
                        base_url = Some(litstr.value());
                    }
                }
                Ok(())
            });
        }
    }

    let base_url = base_url.expect("Missing #[http_get(url = \"...\")] attribute");

    let expanded = match &input.data {
        Data::Struct(data_struct) => {
            let fields = match &data_struct.fields {
                Fields::Named(named) => &named.named,
                _ => panic!("#[derive(HttpGetRequest)] only supports structs with named fields"),
            };

            let mut query_param_code = Vec::new();
            for field in fields {
                let ident = field.ident.clone().unwrap();
                let field_name = ident.to_string();
                if field_name.starts_with("lnk_p_") {
                    let key = &field_name["lnk_p_".len()..];
                    query_param_code.push(quote! {
                        query_params.push((#key.to_string(), self.#ident.to_string()));
                    });
                }
            }

            quote! {
                impl #name {
                    pub async fn send(
                        &self,
                        client: std::sync::Arc<awc::Client>,
                        headers: Option<Vec<(&str, &str)>>,
                        api_key: Option<&str>,
                    ) -> Result<awc::ClientResponse, awc::error::SendRequestError> {
                        use urlencoding::encode;

                        let mut query_params: Vec<(String, String)> = Vec::new();
                        #(#query_param_code)*

                        if let Some(key) = api_key {
                            query_params.push(("api_key".to_string(), key.to_string()));
                        }

                        let mut url = #base_url.to_string();
                        if !query_params.is_empty() {
                            let query_parts: Vec<String> = query_params.iter()
                                .map(|(k, v)| format!("{}={}", k, encode(v)))
                                .collect();
                            url.push('?');
                            url.push_str(&query_parts.join("&"));
                        }

                        let mut request = client.get(url);

                        if let Some(hdrs) = headers {
                            for (k, v) in hdrs {
                                request = request.append_header((k, v));
                            }
                        }

                        let response = request.send().await?;
                        Ok(response)
                    }
                }
            }
        }

        Data::Enum(data_enum) => {
            let mut variant_arms = Vec::new();
            for variant in &data_enum.variants {
                let vname = &variant.ident;
                match &variant.fields {
                    Fields::Unnamed(fields) if fields.unnamed.len() == 1 => {
                        variant_arms.push(quote! {
                            #name::#vname(inner) => inner.send(client.clone(), headers.clone(), api_key).await,
                        });
                    }
                    _ => panic!("#[derive(HttpGetRequest)] enum variants must have a single unnamed field"),
                }
            }

            quote! {
                impl #name {
                    pub async fn send(
                        &self,
                        client: std::sync::Arc<awc::Client>,
                        headers: Option<Vec<(&str, &str)>>,
                        api_key: Option<&str>,
                    ) -> Result<awc::ClientResponse, awc::error::SendRequestError> {
                        match self {
                            #(#variant_arms)*
                        }
                    }
                }
            }
        }

        _ => panic!("#[derive(HttpGetRequest)] only supports structs and enums"),
    };

    TokenStream::from(expanded)
}