use std::collections::HashMap;
use std::env;
use std::fs::File;
use std::io::{BufRead, BufReader, Read, Write};
use std::path::Path;

use abnf_to_pest::{abnf_to_pest, PestRuleSettings};

fn main() -> std::io::Result<()> {
    // TODO: upstream changes to grammar
    // let abnf_path = "../dhall-lang/standard/dhall.abnf";
    let abnf_path = "src/dhall.abnf";
    let visibility_path = "src/dhall.pest.visibility";
    let pest_path = "src/dhall.pest";
    println!("cargo:rerun-if-changed={}", abnf_path);
    println!("cargo:rerun-if-changed={}", visibility_path);

    let mut file = File::open(abnf_path)?;
    let mut data = Vec::new();
    file.read_to_end(&mut data)?;
    data.push('\n' as u8);

    let mut rule_settings: HashMap<String, PestRuleSettings> = HashMap::new();
    for line in BufReader::new(File::open(visibility_path)?).lines() {
        let line = line?;
        if line.len() >= 2 && &line[0..2] == "# " {
            rule_settings.insert(
                line[2..].into(),
                PestRuleSettings {
                    visible: false,
                    ..Default::default()
                },
            );
        } else {
            rule_settings.insert(
                line,
                PestRuleSettings {
                    visible: true,
                    ..Default::default()
                },
            );
        }
    }
    rule_settings.insert(
        "simple_label".to_owned(),
        PestRuleSettings {
            visible: true,
            replace: Some(
                "
              keyword_raw ~ simple_label_next_char+
            | !keyword_raw ~ simple_label_first_char ~ simple_label_next_char*
        "
                .to_owned(),
            ),
        },
    );

    let mut file = File::create(pest_path)?;
    writeln!(&mut file, "// AUTO-GENERATED FILE. See build.rs.")?;
    writeln!(&mut file, "{}", abnf_to_pest(&data, &rule_settings)?)?;
    writeln!(
        &mut file,
        "keyword_raw = _{{
        let_raw | in_raw | if_raw | then_raw
            | else_raw | Infinity_raw | NaN_raw
    }}"
    )?;
    writeln!(
        &mut file,
        "final_expression = {{ SOI ~ complete_expression ~ EOI }}"
    )?;

    // Generate pest parser manually to avoid spurious recompilations
    let derived = {
        let pest_path = "dhall.pest";
        let pest = quote::quote! {
            #[grammar = #pest_path]
            pub struct DhallParser;
        };
        pest_generator::derive_parser(pest, false)
    };

    let out_dir = env::var("OUT_DIR").unwrap();
    let grammar_path = Path::new(&out_dir).join("grammar.rs");
    let mut file = File::create(grammar_path)?;
    writeln!(file, "pub struct DhallParser;\n{}", derived,)?;

    Ok(())
}