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// SPDX-License-Identifier: MIT
// Copyright (c) 2022 JSRPC “Kryptonite”

mod generator;
mod utils;

use std::{fmt::Write, str::FromStr};

use proc_macro::TokenStream as TokenStream0;
use proc_macro2::TokenStream;
use quote::{quote, ToTokens};
use syn::{parse::Parser, punctuated::Punctuated, *};

use generator::*;
use utils::{config::*, field::*, field_to_tokens, parser::*, top_level::*};

/// Macro generating an implementation of the `ConfigInit` trait
/// or constructing global variable. \
///
/// For more info see crate level documentation
#[proc_macro_attribute]
pub fn config(attrs: TokenStream0, input: TokenStream0) -> TokenStream0 {
    let parser = Punctuated::<Meta, Token![,]>::parse_terminated;
    let attrs = parser.parse(attrs).unwrap();
    let mut annotations = String::from(
        "#[derive(::config_manager::__private::__Config__, \
         ::config_manager::__private::serde::Deserialize)]\n#[serde(crate = \
         \"::config_manager::__private::serde\")]",
    );
    attrs.iter().for_each(|attr| {
        std::write!(&mut annotations, "\n{}", (quote! { #[#attr]})).unwrap();
    });
    let mut annotations =
        TokenStream0::from_str(&annotations).expect("can't parse annotations as tokenstream");
    annotations.extend(input.into_iter());
    annotations
}

#[proc_macro_derive(
    __Config__,
    attributes(
        source,
        flatten,
        subcommand,
        config,
        env_prefix,
        clap,
        global_name,
        file,
        table,
        __debug_cmd_input__
    )
)]
pub fn generate_config(input: TokenStream0) -> TokenStream0 {
    let input = parse_macro_input!(input as DeriveInput);

    let class_ident = input.ident;

    let AppTopLevelInfo {
        env_prefix,
        clap_app_info,
        configs,
        debug_cmd_input,
        table_name,
    } = AppTopLevelInfo::extract(&input.attrs);

    let class: DataStruct = match input.data {
        Data::Struct(s) => s,
        _ => panic!("config macro input should be a Struct"),
    };

    unzip_n::unzip_n!(2);
    let (fields_json_definition, clap_fields): (
        Vec<(proc_macro2::Ident, TokenStream)>,
        Vec<ClapInitialization>,
    ) = class
        .fields
        .into_iter()
        .map(|field| {
            let ProcessFieldResult {
                name,
                clap_field,
                initialization,
            } = if field_is_flatten(&field) {
                process_flatten_field(field)
            } else if field_is_subcommand(&field) {
                process_subcommand_field(field, &debug_cmd_input)
            } else if field_is_source(&field) {
                process_field(field, &table_name)
            } else {
                panic!(
                    "Error: each field must be annotated with one of the following: \
                     source/flatten/subcommand (field's name: \"{}\")",
                    field_to_tokens(&field)
                )
            };
            ((name, initialization), clap_field)
        })
        .unzip_n();

    generate_final_struct_and_supporting_code(InitializationInfo {
        env_prefix,
        class_ident,
        clap_app_info,
        configs,
        clap_fields,
        fields_json_definition,
        debug_cmd_input,
    })
    .into()
}

/// Annotated with this macro structure can be used
/// as a flatten argument in the [config](attr.config.html) macro.
#[proc_macro_derive(Flatten, attributes(source, flatten, subcommand, table))]
pub fn generate_flatten(input: TokenStream0) -> TokenStream0 {
    let input = parse_macro_input!(input as DeriveInput);

    let table_name = extract_table_name(&input.attrs);

    let class_ident = input.ident;
    let class: DataStruct = match input.data {
        Data::Struct(s) => s,
        _ => panic!("config macro input should be a Struct"),
    };

    unzip_n::unzip_n!(2);
    let (fields_json_definition, clap_fields): (
        Vec<(proc_macro2::Ident, TokenStream)>,
        Punctuated<ClapInitialization, Token![.]>,
    ) = class
        .fields
        .into_iter()
        .map(|field| {
            let ProcessFieldResult {
                name,
                clap_field,
                initialization,
            } = if field_is_flatten(&field) {
                process_flatten_field(field)
            } else if field_is_subcommand(&field) {
                panic!("subcommands are forbidden in the nested structures")
            } else if field_is_source(&field) {
                process_field(field, &table_name)
            } else {
                panic!(
                    "Error: each field must be annotated with one of the following: \
                     source/flatten (field's name: \"{}\")",
                    field_to_tokens(&field)
                )
            };
            ((name, initialization), clap_field)
        })
        .unzip_n();

    generate_flatten_implementation(class_ident, clap_fields, fields_json_definition).into()
}