use nom::{
  bytes::complete::{is_a, tag, take_till, take_while},
  character::complete::{alphanumeric1 as alphanumeric, char, space0 as space},
  combinator::opt,
  multi::many0,
  sequence::{delimited, pair, terminated, tuple},
  IResult,
};

use std::collections::HashMap;

fn is_line_ending_or_comment(chr: char) -> bool {
  chr == ';' || chr == '\n'
}

fn not_line_ending(i: &str) -> IResult<&str, &str> {
  take_while(|c| c != '\r' && c != '\n')(i)
}

fn space_or_line_ending(i: &str) -> IResult<&str, &str> {
  is_a(" \r\n")(i)
}

fn category(i: &str) -> IResult<&str, &str> {
  terminated(
    delimited(char('['), take_while(|c| c != ']'), char(']')),
    opt(is_a(" \r\n")),
  )(i)
}

fn key_value(i: &str) -> IResult<&str, (&str, &str)> {
  let (i, key) = alphanumeric(i)?;
  let (i, _) = tuple((opt(space), tag("="), opt(space)))(i)?;
  let (i, val) = take_till(is_line_ending_or_comment)(i)?;
  let (i, _) = opt(space)(i)?;
  let (i, _) = opt(pair(tag(";"), not_line_ending))(i)?;
  let (i, _) = opt(space_or_line_ending)(i)?;

  Ok((i, (key, val)))
}

fn keys_and_values_aggregator(i: &str) -> IResult<&str, Vec<(&str, &str)>> {
  many0(key_value)(i)
}

fn keys_and_values(input: &str) -> IResult<&str, HashMap<&str, &str>> {
  match keys_and_values_aggregator(input) {
    Ok((i, tuple_vec)) => Ok((i, tuple_vec.into_iter().collect())),
    Err(e) => Err(e),
  }
}

fn category_and_keys(i: &str) -> IResult<&str, (&str, HashMap<&str, &str>)> {
  pair(category, keys_and_values)(i)
}

fn categories_aggregator(i: &str) -> IResult<&str, Vec<(&str, HashMap<&str, &str>)>> {
  many0(category_and_keys)(i)
}

fn categories(input: &str) -> IResult<&str, HashMap<&str, HashMap<&str, &str>>> {
  match categories_aggregator(input) {
    Ok((i, tuple_vec)) => Ok((i, tuple_vec.into_iter().collect())),
    Err(e) => Err(e),
  }
}

#[test]
fn parse_category_test() {
  let ini_file = "[category]

parameter=value
key = value2";

  let ini_without_category = "parameter=value
key = value2";

  let res = category(ini_file);
  println!("{:?}", res);
  match res {
    Ok((i, o)) => println!("i: {} | o: {:?}", i, o),
    _ => println!("error"),
  }

  assert_eq!(res, Ok((ini_without_category, "category")));
}

#[test]
fn parse_key_value_test() {
  let ini_file = "parameter=value
key = value2";

  let ini_without_key_value = "key = value2";

  let res = key_value(ini_file);
  println!("{:?}", res);
  match res {
    Ok((i, (o1, o2))) => println!("i: {} | o: ({:?},{:?})", i, o1, o2),
    _ => println!("error"),
  }

  assert_eq!(res, Ok((ini_without_key_value, ("parameter", "value"))));
}

#[test]
fn parse_key_value_with_space_test() {
  let ini_file = "parameter = value
key = value2";

  let ini_without_key_value = "key = value2";

  let res = key_value(ini_file);
  println!("{:?}", res);
  match res {
    Ok((i, (o1, o2))) => println!("i: {} | o: ({:?},{:?})", i, o1, o2),
    _ => println!("error"),
  }

  assert_eq!(res, Ok((ini_without_key_value, ("parameter", "value"))));
}

#[test]
fn parse_key_value_with_comment_test() {
  let ini_file = "parameter=value;abc
key = value2";

  let ini_without_key_value = "key = value2";

  let res = key_value(ini_file);
  println!("{:?}", res);
  match res {
    Ok((i, (o1, o2))) => println!("i: {} | o: ({:?},{:?})", i, o1, o2),
    _ => println!("error"),
  }

  assert_eq!(res, Ok((ini_without_key_value, ("parameter", "value"))));
}

#[test]
fn parse_multiple_keys_and_values_test() {
  let ini_file = "parameter=value;abc

key = value2

[category]";

  let ini_without_key_value = "[category]";

  let res = keys_and_values(ini_file);
  println!("{:?}", res);
  match res {
    Ok((i, ref o)) => println!("i: {} | o: {:?}", i, o),
    _ => println!("error"),
  }

  let mut expected: HashMap<&str, &str> = HashMap::new();
  expected.insert("parameter", "value");
  expected.insert("key", "value2");
  assert_eq!(res, Ok((ini_without_key_value, expected)));
}

#[test]
fn parse_category_then_multiple_keys_and_values_test() {
  //FIXME: there can be an empty line or a comment line after a category
  let ini_file = "[abcd]
parameter=value;abc

key = value2

[category]";

  let ini_after_parser = "[category]";

  let res = category_and_keys(ini_file);
  println!("{:?}", res);
  match res {
    Ok((i, ref o)) => println!("i: {} | o: {:?}", i, o),
    _ => println!("error"),
  }

  let mut expected_h: HashMap<&str, &str> = HashMap::new();
  expected_h.insert("parameter", "value");
  expected_h.insert("key", "value2");
  assert_eq!(res, Ok((ini_after_parser, ("abcd", expected_h))));
}

#[test]
fn parse_multiple_categories_test() {
  let ini_file = "[abcd]

parameter=value;abc

key = value2

[category]
parameter3=value3
key4 = value4
";

  let res = categories(ini_file);
  //println!("{:?}", res);
  match res {
    Ok((i, ref o)) => println!("i: {} | o: {:?}", i, o),
    _ => println!("error"),
  }

  let mut expected_1: HashMap<&str, &str> = HashMap::new();
  expected_1.insert("parameter", "value");
  expected_1.insert("key", "value2");
  let mut expected_2: HashMap<&str, &str> = HashMap::new();
  expected_2.insert("parameter3", "value3");
  expected_2.insert("key4", "value4");
  let mut expected_h: HashMap<&str, HashMap<&str, &str>> = HashMap::new();
  expected_h.insert("abcd", expected_1);
  expected_h.insert("category", expected_2);
  assert_eq!(res, Ok(("", expected_h)));
}