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use proc_macro::TokenStream;
use proc_macro2::Ident;
use quote::quote;

use syn::{parse, parse_macro_input, ItemImpl};

fn snake_case_to_camel_case(s: &str) -> String {
    s.split('_')
        .enumerate()
        .map(|(i, s)| {
            if i == 0 {
                s.to_string()
            } else {
                s.chars().next().unwrap().to_uppercase().collect::<String>() + &s[1..]
            }
        })
        .collect()
}

#[proc_macro_attribute]
pub fn plugin_impl(args: TokenStream, input: TokenStream) -> TokenStream {
    let item_impl = parse_macro_input!(input as ItemImpl);
    let _ = parse_macro_input!(args as parse::Nothing);

    let struct_ident = item_impl.clone().self_ty;

    let mut method_idents: Vec<(Ident, String, bool, Option<bool>)> = vec![];

    for item in item_impl.clone().items {
        match item {
            syn::ImplItem::Method(method) => {
                let function_ident = &method.sig.ident;
                let env_is_option = if &method.sig.inputs.len() > &3 {
                    let env = &method.sig.inputs[3];
                    let env_str = quote! { #env }.to_string();

                    Some(env_str.contains("Option <"))
                } else {
                    None
                };

                let output_type = match &method.sig.output {
                    syn::ReturnType::Default => quote! { () },
                    syn::ReturnType::Type(_, ty) => quote! { #ty },
                };
                let output_type = quote! { #output_type }.to_string();
                let function_ident_str = snake_case_to_camel_case(&function_ident.to_string());
                let output_is_option = output_type.contains("Option <");

                method_idents.push((
                    function_ident.clone(),
                    function_ident_str.clone(),
                    output_is_option,
                    env_is_option,
                ));
            }
            _ => panic!("Wrong function signature"),
        }
    }

    let supported_methods =
        method_idents
            .clone()
            .into_iter()
            .enumerate()
            .map(|(_, (_, ident_str, _, _))| {
                quote! {
                  #ident_str
                }
            });

    let methods = method_idents.into_iter().enumerate().map(
        |(_, (ident, ident_str, output_is_option, env_is_option))| {
            let args = if let Some(env_is_option) = env_is_option {
                let env = if env_is_option {
                    quote! {
                      if let Some(e) = env {
                          Some(polywrap_msgpack_serde::from_slice(&e).unwrap())
                      } else {
                          None
                      }
                    }
                } else {
                    quote! {
                        if let Some(e) = env {
                          polywrap_msgpack_serde::from_slice(&e).unwrap()
                        } else {
                          panic!("Env must be defined for method '{}'", #ident_str)
                        }
                    }
                };

                quote! {
                  &polywrap_msgpack_serde::from_slice(&params).unwrap(),
                  invoker,
                  #env
                }
            } else {
                quote! {
                  &polywrap_msgpack_serde::from_slice(&params).unwrap(),
                  invoker
                }
            };

            let output = quote! {
                Ok(polywrap_msgpack_serde::to_vec(&result)?)
            };

            quote! {
                #ident_str => {
                    let result = self.#ident(
                      #args
                    )?;

                    #output
                }
            }
        },
    );

    let module_impl = quote! {
        impl polywrap_plugin::module::PluginModule for #struct_ident {
            fn _wrap_invoke(
                &mut self,
                method_name: &str,
                params: &[u8],
                env: Option<&[u8]>,
                invoker: Arc<dyn polywrap_core::invoker::Invoker>,
            ) -> Result<Vec<u8>, polywrap_plugin::error::PluginError> {
                let supported_methods = vec![#(#supported_methods),*];
                match method_name {
                    #(#methods)*
                    _ => Err(PluginError::MethodNotFoundError(method_name.to_string())),
                }
            }
        }
    };

    let from_impls = quote! {
        impl From<#struct_ident> for polywrap_plugin::package::PluginPackage<#struct_ident> {
            fn from(plugin: #struct_ident) -> polywrap_plugin::package::PluginPackage<#struct_ident> {
                let plugin_module = Arc::new(std::sync::Mutex::new(plugin));
                polywrap_plugin::package::PluginPackage::new(plugin_module, get_manifest())
            }
        }

        impl From<#struct_ident> for polywrap_plugin::wrapper::PluginWrapper<#struct_ident> {
            fn from(plugin: #struct_ident) -> polywrap_plugin::wrapper::PluginWrapper<#struct_ident> {
                let plugin_module = Arc::new(std::sync::Mutex::new(plugin));
                polywrap_plugin::wrapper::PluginWrapper::new(plugin_module)
            }
        }
    };

    quote! {
        #item_impl

        #module_impl

        #from_impls
    }
    .into()
}