use convert_case::{Case, Casing};
use proc_macro2::TokenStream;
use quote::{format_ident, quote};
use std::path::Path;
use std::{fs, io};
use syn::File;

pub struct ParserTestSuitesFile {
    pub file_name: String,
    pub contents: String,
}

pub fn generate_test_files(tests_dir: &Path) -> io::Result<ParserTestSuitesFile> {
    let mut test_suites: Vec<TokenStream> = vec![];

    // generate test file for each sub dir
    for sub_dir in fs::read_dir(tests_dir)? {
        let sub_dir = sub_dir?;
        let sub_dir_path = sub_dir.path();
        if sub_dir_path.is_dir() {
            let sub_dir_file_name = sub_dir.file_name();
            let sub_dir_string = sub_dir_file_name.to_string_lossy();

            let sub_dir_pascal = sub_dir_string.to_case(Case::Pascal);
            let rule_ident = format_ident!("{}", sub_dir_pascal);

            let mut tests: Vec<TokenStream> = vec![];
            for test_file in fs::read_dir(sub_dir_path)? {
                let test_file = test_file?;
                let test_file_name = test_file.file_name();
                let test_ident = format_ident!("{}", test_file_name.to_string_lossy());

                let src_input = fs::read_to_string(test_file.path())?;

                let test = quote! {
                    #[test]
                    fn #test_ident() {
                        parses_to(Rule::#rule_ident, #src_input)
                    }
                };

                tests.push(test);
            }

            let tests_mod_ident = format_ident!("{}_tests", sub_dir.file_name().to_string_lossy());
            let test_suite = quote! {
                mod #tests_mod_ident {
                    use super::*;
                    
                    #(#tests)*
                }
            };
            test_suites.push(test_suite);
        } else {
            println!("Warning: not a directory: {:?}", sub_dir_path);
        }
    }

    // generate main test_suites file
    let test_suites = quote! {
        use super::*;
        
        #(#test_suites)*
    };
    let test_suites_file: File = syn::parse2(test_suites).unwrap();
    let test_suites_file_contents = prettyplease::unparse(&test_suites_file);

    Ok(ParserTestSuitesFile {
        file_name: String::from("test_suites.rs"),
        contents: test_suites_file_contents,
    })
}