deimos-lang/ast-generator/src/build_fn/struct_build_fn.rs

use crate::deserialize::util::{make_build_fn_name, make_build_pair};
use crate::spec::struct_spec::{
    MemberChildBuild, NodeMemberBuild, StructChild, StructSpec, VecChild, VecChildBuild,
};
use crate::spec::{SpecialChild, SpecialChildKind};
use proc_macro2::{Ident, TokenStream};
use quote::{format_ident, quote};

fn make_preamble(spec: &StructSpec, pair_ident: &Ident) -> TokenStream {
    if spec.children().any(StructChild::is_special) {
        quote! {
            let as_span = #pair_ident.as_span();
        }
    } else {
        quote! {}
    }
}

fn make_special_children(spec: &StructSpec) -> Vec<TokenStream> {
    spec.children()
        .map(StructChild::unwrap_special)
        .filter(Option::is_some)
        .map(Option::unwrap)
        .map(|special_child| {
            let child_ident = format_ident!("{}", special_child.name());
            match special_child.kind() {
                SpecialChildKind::FileId => {
                    quote! {
                        let #child_ident = file_id
                    }
                }
                SpecialChildKind::Range => {
                    quote! {
                        let #child_ident = Range {
                            start: as_span.start(),
                            end: as_span.end()
                        }
                    }
                }
            }
        })
        .collect::<Vec<_>>()
}

fn make_vec_child_holder(vec_child: &VecChild) -> TokenStream {
    let child_ident = format_ident!("{}", vec_child.name());
    match vec_child.build() {
        VecChildBuild::String(_) => {
            quote! {
                let mut #child_ident: Vec<String> = vec![]
            }
        }
        VecChildBuild::Node(node_build) => {
            let child_type_ident = format_ident!("{}", node_build.kind());
            quote! {
                let mut #child_ident: Vec<Box<#child_type_ident>> = vec![]
            }
        }
    }
}

fn make_node_child_holder(name: &str, node_child: &NodeMemberBuild) -> TokenStream {
    let child_ident = format_ident!("{}", name);
    let child_type_ident = format_ident!("{}", node_child.kind());
    quote! {
        let mut #child_ident: Option<Box<#child_type_ident>> = None
    }
}

fn make_boolean_child_holder(name: &str) -> TokenStream {
    let child_ident = format_ident!("{}", name);
    quote! {
        let mut #child_ident: bool = false
    }
}

fn make_child_holder(child_spec: &StructChild) -> Option<TokenStream> {
    match child_spec {
        StructChild::SkipChild(_) => None,
        StructChild::VecChild(vec_child) => Some(make_vec_child_holder(vec_child)),
        StructChild::MemberChild(member_child) => match member_child.build() {
            MemberChildBuild::Node(node_child) => {
                Some(make_node_child_holder(member_child.name(), node_child))
            }
            MemberChildBuild::Boolean(_) => Some(make_boolean_child_holder(member_child.name())),
        },
        StructChild::Special(_) => None,
    }
}

fn make_vec_child_match_action(vec_child: &VecChild) -> TokenStream {
    let child_name_ident = format_ident!("{}", vec_child.name());
    match vec_child.build() {
        VecChildBuild::String(string_build) => {
            let build_fn_ident = format_ident!("{}", string_build.with());
            quote! {
                #child_name_ident.push(#build_fn_ident(file_id, inner_pair))
            }
        }
        VecChildBuild::Node(node_build) => {
            let build_fn_ident = format_ident!("{}", node_build.with());
            quote! {
                #child_name_ident.push(Box::new(#build_fn_ident(file_id, inner_pair)))
            }
        }
    }
}

fn make_node_member_child_match_action(name: &str, node_child: &NodeMemberBuild) -> TokenStream {
    let child_name_ident = format_ident!("{}", name);
    let build_fn_ident = format_ident!("{}", node_child.with());
    quote! {
        #child_name_ident = Some(Box::new(#build_fn_ident(file_id, inner_pair)))
    }
}

fn make_boolean_member_child_match_action(name: &str) -> TokenStream {
    let child_name_ident = format_ident!("{}", name);
    quote! {
        #child_name_ident = true
    }
}

fn make_rule_matcher(child_spec: &StructChild) -> Option<TokenStream> {
    match child_spec {
        StructChild::SkipChild(skip_child) => {
            let rule_ident = format_ident!("{}", skip_child.rule());
            Some(quote! {
                Rule::#rule_ident => {}
            })
        }
        StructChild::VecChild(vec_child) => {
            let rule_ident = format_ident!("{}", vec_child.rule());
            let action = make_vec_child_match_action(vec_child);
            Some(quote! {
                Rule::#rule_ident => { #action }
            })
        }
        StructChild::MemberChild(member_child) => match member_child.build() {
            MemberChildBuild::Node(node_member_build) => {
                let rule_ident = format_ident!("{}", member_child.rule());
                let action =
                    make_node_member_child_match_action(member_child.name(), node_member_build);
                Some(quote! {
                    Rule::#rule_ident => { #action }
                })
            }
            MemberChildBuild::Boolean(_) => {
                let rule_ident = format_ident!("{}", member_child.rule());
                let action = make_boolean_member_child_match_action(member_child.name());
                Some(quote! {
                    Rule::#rule_ident => { #action }
                })
            }
        },
        StructChild::Special(_) => None,
    }
}

fn make_vec_child_arg(vec_child: &VecChild) -> TokenStream {
    let child_ident = format_ident!("{}", vec_child.name());
    quote! { #child_ident }
}

fn make_node_member_child_arg(
    name: &str,
    optional: bool,
    node_child: &NodeMemberBuild,
) -> TokenStream {
    let child_ident = format_ident!("{}", name);
    if optional {
        quote! { #child_ident }
    } else if let Some(or_else) = node_child.or_else() {
        let child_type_ident = format_ident!("{}", node_child.kind());
        let or_else_ident = format_ident!("{}", or_else);
        quote! {
            #child_ident.unwrap_or_else(|| Box::new(#child_type_ident::#or_else_ident()))
        }
    } else {
        quote! { #child_ident.unwrap() }
    }
}

fn make_boolean_member_child_arg(name: &str) -> TokenStream {
    let child_ident = format_ident!("{}", name);
    quote! { #child_ident }
}

fn make_special_child_arg(special_child: &SpecialChild) -> TokenStream {
    let child_ident = format_ident!("{}", special_child.name());
    quote! { #child_ident }
}

fn make_child_arg(child_spec: &StructChild, pair_ident: &Ident) -> Option<TokenStream> {
    match child_spec {
        StructChild::SkipChild(_) => None,
        StructChild::VecChild(vec_child) => Some(make_vec_child_arg(vec_child)),
        StructChild::MemberChild(member_child) => match member_child.build() {
            MemberChildBuild::Node(node_member_build) => Some(make_node_member_child_arg(
                member_child.name(),
                member_child.optional(),
                node_member_build,
            )),
            MemberChildBuild::Boolean(_) => {
                Some(make_boolean_member_child_arg(member_child.name()))
            }
        },
        StructChild::Special(special_child) => Some(make_special_child_arg(special_child)),
    }
}

fn make_return_value_stream(build_spec: &StructSpec, pair_ident: &Ident) -> TokenStream {
    let type_ident = format_ident!("{}", build_spec.build());
    let child_args = build_spec
        .children()
        .map(|child| make_child_arg(child, pair_ident))
        .filter(|child_arg| child_arg.is_some())
        .map(|child_arg| child_arg.unwrap())
        .collect::<Vec<_>>();

    quote! {
        #type_ident::new(
            #(#child_args,)*
        )
    }
}

pub fn make_struct_build_fn(build_spec: &StructSpec) -> TokenStream {
    let build_fn_ident = format_ident!("{}", make_build_fn_name(build_spec.build()));
    let pair_ident = format_ident!("{}", make_build_pair(build_spec.build()));
    let return_type_ident = format_ident!("{}", build_spec.build());

    let preamble = make_preamble(build_spec, &pair_ident);

    let special_children = make_special_children(build_spec);

    let child_holders = build_spec
        .children()
        .map(|child_spec| make_child_holder(child_spec))
        .filter(|child_holder| child_holder.is_some())
        .map(|child_holder| child_holder.unwrap())
        .collect::<Vec<_>>();

    let rule_matchers = build_spec
        .children()
        .map(|child_spec| make_rule_matcher(child_spec))
        .collect::<Vec<_>>();

    let iter_stream = quote! {
        for inner_pair in #pair_ident.into_inner() {
            match inner_pair.as_rule() {
                #(#rule_matchers)*
                _ => panic!("Unexpected rule: {:?}", inner_pair.as_rule())
            }
        }
    };

    let new_stream = make_return_value_stream(build_spec, &pair_ident);

    quote! {
        fn #build_fn_ident(file_id: usize, #pair_ident: Pair<Rule>) -> #return_type_ident {
            #preamble

            #(#special_children;)*

            #(#child_holders;)*

            #iter_stream

            #new_stream
        }
    }
}