use proc_macro::TokenStream;
use quote::quote;
use syn::{parse_macro_input, parse_quote, Attribute, DeriveInput, Lit, Meta, NestedMeta};

/// This BoltAccount attribute is used to automatically generate the seed and size functions
///
/// The component_id define the seed used to generate the PDA which stores the component data.
/// The macro also adds the InitSpace and Default derives to the struct.
///
/// #[account]
/// #[bolt_account]
/// pub struct Position {
///     pub x: i64,
///     pub y: i64,
///     pub z: i64,
/// }
/// ```
#[proc_macro_attribute]
pub fn bolt_account(attr: TokenStream, item: TokenStream) -> TokenStream {
    let mut input = parse_macro_input!(item as DeriveInput);
    let mut component_id_value = None;

    if !attr.is_empty() {
        let attr_meta = parse_macro_input!(attr as Meta);

        component_id_value = match attr_meta {
            Meta::Path(_) => None,
            Meta::NameValue(meta_name_value) if meta_name_value.path.is_ident("component_id") => {
                if let Lit::Str(lit) = meta_name_value.lit {
                    Some(lit.value())
                } else {
                    None
                }
            }
            Meta::List(meta) => meta.nested.into_iter().find_map(|nested_meta| {
                if let NestedMeta::Meta(Meta::NameValue(meta_name_value)) = nested_meta {
                    if meta_name_value.path.is_ident("component_id") {
                        if let Lit::Str(lit) = meta_name_value.lit {
                            Some(lit.value())
                        } else {
                            None
                        }
                    } else {
                        None
                    }
                } else {
                    None
                }
            }),
            _ => None,
        };
    }

    let component_id_value = component_id_value.unwrap_or_else(|| "".to_string());

    let additional_derives: Attribute = parse_quote! { #[derive(InitSpace, Default)] };
    input.attrs.push(additional_derives);

    let name = &input.ident;
    let expanded = quote! {
        #input

        #[automatically_derived]
        impl ComponentTraits for #name {
            fn seed() -> &'static [u8] {
                #component_id_value.as_bytes()
            }

            fn size() -> usize {
                8 + <#name>::INIT_SPACE
            }
        }
    };
    expanded.into()
}