// Copyright (C) 2021 "Maxime “pep” Buquet <pep@bouah.net>"
//
// This program is free software: you can redistribute it and/or modify it
// under the terms of the GNU Affero General Public License as published by the
// Free Software Foundation, either version 3 of the License, or (at your
// option) any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License
// for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.

use std::env;
use std::fmt;
use std::fs::{self, File};
use std::io::{BufWriter, Write};
use std::error::Error as StdError;
use std::path::Path;

use quote::{format_ident, quote};
use pkstrings::{self, PKString};

#[derive(Debug, Eq, PartialEq)]
pub enum Error {
    EnvVariableError(env::VarError),
    PKStringError(pkstrings::Error),
    ROMDoesntExist,
    UnableToOpenROM,
}

impl StdError for Error {}

impl fmt::Display for Error {
    fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
        match self {
            Error::EnvVariableError(e) => write!(f, "POKEMON_ROM env var error: {}", e),
            Error::PKStringError(e) => write!(f, "PKString error: {}", e),
            Error::ROMDoesntExist => write!(f, "ROM doesn't exist"),
            Error::UnableToOpenROM => write!(f, "Unable to open ROM"),
        }
    }
}

impl From<env::VarError> for Error {
    fn from(err: env::VarError) -> Error {
        Error::EnvVariableError(err)
    }
}

impl From<pkstrings::Error> for Error {
    fn from(err: pkstrings::Error) -> Error {
        Error::PKStringError(err)
    }
}

fn get_rom() -> Result<Vec<u8>, Error> {
    let env_romp = env::var("POKEMON_ROM")?;
    let romp = Path::new(&env_romp);

    if ! romp.exists() {
        return Err(Error::ROMDoesntExist);
    }

    Ok(match fs::read(romp) {
        Ok(v) => v,
        Err(_) => return Err(Error::UnableToOpenROM),
    })
}

/// Get pokemon names from ROM slice.
/// The data that gets in is a list of encoded strings of 10 chars each, over 255 pokemons.
fn get_pokemon_list(data: &[u8]) -> Result<Vec<String>, Error> {
    let mut buffer: String = String::with_capacity(10);
    let mut res: Vec<String> = Vec::with_capacity(255);

    // TODO: Ensure we have the right length? a multiple of 10

    for (offset, ord) in data.iter().enumerate() {
        if offset != 0 && (offset % 10) == 0 {
            res.push(buffer.clone());
            buffer.clear()
        }

        if *ord == 0x50 {  // End char, '@'.
            continue
        }

        let pkstr = match PKString::try_from(&[*ord][..]) {
            Ok(pkstr) => pkstr,
            Err(e) => {
                println!("BUFFER: {:?}", buffer);
                return Err(Error::PKStringError(e));
            },
        };

        buffer.push_str(String::from(&pkstr).as_str());
    }

    res.push(buffer.clone());
    Ok(res)
}

fn main() -> Result<(), Error> {
    let output = Path::new(&env::var("OUT_DIR").unwrap()).join("output.rs");
    let mut output = BufWriter::new(File::create(&output).unwrap());
    let rom: Vec<u8> = get_rom()?;

    let pkmn: Vec<_> = {
        let start = 0x1c21e;
        let end = start + 10 * 190;  // Only the first 190 are valid
        get_pokemon_list(&rom[start..end])?
    };

    let pkmn_names: Vec<_> = [
        "Rhydon",
        "Kangashkan",
        "NidoranM",
    ].iter()
    .map(|n| format_ident!("{}", n))
    .collect();

    let tokens = quote! {
        /// Generated file containing various resources extracted from the provided ROM.

        pub enum PokemonNames {
            #(#pkmn_names),*
        }

        let foo = vec![#(#pkmn),*];
    };

    write!(output, "{}", tokens).unwrap();
    Ok(())
}