/* 
 * Copyright (c) 2022 Emma Tebibyte
 * SPDX-License-Identifier: AGPL-3.0-or-later
 *
 * 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,
  fs::File,
  io::{
    Read,
    stdin,
  },
  iter::Peekable,
  path::Path,
  str::FromStr,
};

use toml::Value;
use yacexits::*;

fn parse_toml(
  mut root: Value,
  mut tabkey: Peekable<std::slice::Iter<'_, &str>>,
  index: Option<usize>,
) -> Result<String, (String, u32)> {
  let mut out = String::new();

  while let Some(item) = tabkey.next() {
    let value = match root.get(item) {
      Some(val) => val,
      None => {
        return Err((format!("{}: No such table or key.", item), EX_DATAERR));
      },
    };

    match value {
      Value::Table(table) => {
        match tabkey.peek() {
          Some(_) => {
            root = toml::Value::Table(table.to_owned());
            continue;
          },
          None => {}, // out.push_str(table.as_str()),
        };
      },
      _ => {
        match tabkey.peek() {
          Some(_) => {
            return Err((format!("{}: Not a table.", item), EX_DATAERR));
          },
          None => {},
        };
      },
    };

    match value {
      // TODO: Implement other type parsing
      Value::Array(array) => {
        let element: String;
        match index {
          Some(i) => {
            element = match array.get(i) {
              Some(element) => {
                match element.as_str() {
                  Some(val) => val.to_owned(),
                  None => {
                    return Err((
                      format!("{:?}: No value at given key.", index),
                      EX_DATAERR
                    ));
                  },
                }
              },
              None => {
                return Err(
                  (format!("{:?}: No value at given index.", i), EX_DATAERR)
                );
              },
            };
          },
          None => element = format!("{:?}", array),
        };
        out.push_str(&element);
      }, 
      Value::Boolean(_boolean) => {}, 
      Value::Datetime(_datetime) => {}, 
      Value::Float(_float) => {},
      Value::Integer(_int) => {},
      Value::String(string) => out.push_str(string.as_str()),
      _ => return Err((format!("{:?}: No such key.", item), EX_DATAERR)),
    };
  }
  Ok(out)
}

fn main() {
  let argv: Vec<String> = env::args().collect();

  if argv.len() <= 1 {
    eprintln!("Usage: {} [table...].[value[index]] [file...]", argv[0]);
    exit(64); // sysexits(3) EX_USAGE
  }
  
  let input = match argv.get(2) {
    Some(val) => val,
    None => {
      eprintln!("Usage: {} [table...].[value[index]] [file...]", argv[0]);
      exit(EX_USAGE);
    },
  };
  let mut content = Vec::new();
  
  let file = Path::new(&input);

  if input == &"-" {
    match stdin().lock().read_to_end(&mut content) {
      Ok(_) => {},
      Err(_) => {
        eprintln!("{}: Could not read from standard input.", argv[0]);
        exit(EX_OSERR);
      },
    };
  } else {
    match File::open(file).unwrap().read_to_end(&mut content) {
      Ok(_) => {},
      Err(_) => {
        eprintln!("{}: {:?}: No such file or directory.", argv[0], file);
        exit(EX_UNAVAILABLE);
      },
    };
  }

  let mut tabkey: Vec<&str> = argv[1].split(".").collect();
  let mut indexvec = Vec::new();
  let mut index: Option<usize> = None;

  match tabkey.iter().skip(1).peekable().peek() {
    Some(_) => {
      indexvec = tabkey[1].split(&['[', ']'][..]).collect();
      tabkey[1] = indexvec.remove(0);
    },
    None => {},
  };

  if ! indexvec.is_empty() {
    let istr = indexvec.remove(0);
    match usize::from_str(istr) {
      Ok(i) => index = Some(i),
      Err(_) => {
        eprintln!("{}: {}: Cannot index by given value.", argv[0], istr);
        exit(EX_USAGE);
      },
    };
  }

  let root = match String::from_utf8(content).unwrap().parse::<Value>() {
    Ok(toml) => toml,
    Err(_) => {
      eprintln!("{}: Unable to parse TOML.", argv[0]);
      exit(EX_DATAERR);
    },
  };

  let valiter = tabkey.iter().peekable();
  println!(
    "{}",
    match parse_toml(root, valiter, index) {
      Ok(val) => val, 
      Err((err, code)) => {
        eprintln!("{}: {}", argv[0], err);
        exit(code);
      },
    },
  );
}