use convert_case::{Case, Casing};
use crate::spec::tree_enum_spec::{EnumRuleChildKind, TreeEnumBuildSpec};
use proc_macro2::TokenStream;
use quote::{format_ident, quote};

pub fn make_enum_ast_node_impl(enum_spec: &TreeEnumBuildSpec) -> TokenStream {
    let type_ident = format_ident!("{}", enum_spec.build());
    let match_arms = enum_spec
        .rules()
        .map(|rule| {
            let rule_ident = format_ident!("{}", rule.rule());
            match rule.child() {
                Some(child) => {
                    match child.kind() {
                        EnumRuleChildKind::Node(node_child) => {
                            let child_ident = format_ident!("{}", node_child.node_kind().to_case(Case::Snake));
                            quote! {
                                #type_ident::#rule_ident(#child_ident) => vec![
                                    #child_ident.as_node_ref()
                                ]
                            }
                        }
                        _ => quote! {
                            #type_ident::#rule_ident(_) => vec![]
                        }
                    }
                },
                None => {
                    quote! {
                        #type_ident::#rule_ident => vec![]
                    }
                }
            }
        })
        .collect::<Vec<_>>();
    
    quote! {
        impl AstNode for #type_ident {
            fn children(&self) -> Vec<AstNodeRef> {
                match self {
                    #(#match_arms,)*
                }
            }

            fn as_node_ref(&self) -> AstNodeRef {
                AstNodeRef::#type_ident(&self)
            }
        }
    }
}