use crate::builtins::internal_error_builtin::ToInternalError;
use crate::builtins::range_error_builtin::ToRangeError;
use crate::native_function::native_fn;
use crate::vs_value::ToVal;
use crate::{
  native_function::NativeFunction,
  todo_fn::TODO,
  vs_value::{Val, ValTrait},
};

pub fn op_sub_number(_number: f64, subscript: &Val) -> Val {
  match subscript.to_string().as_str() {
    "toExponential" => &TO_EXPONENTIAL,
    "toFixed" => &TO_FIXED,
    "toLocaleString" => &TODO_LOCALE,
    "toPrecision" => &TODO,
    "toString" => &TO_STRING,
    "valueOf" => &VALUE_OF,
    _ => return Val::Undefined,
  }
  .to_val()
}

static TO_FIXED: NativeFunction = native_fn(|this, params| {
  Ok(match this.get() {
    Val::Number(number) => {
      if number.is_infinite() {
        return Ok(
          if number.is_sign_positive() {
            "Infinity"
          } else {
            "-Infinity"
          }
          .to_val(),
        );
      }

      let mut precision = match params.get(0) {
        Some(p) => p.to_number(),
        _ => return Ok(number.to_val().to_string().to_val()),
      };

      precision = f64::floor(precision);

      if precision < 1.0 || precision > 100.0 {
        return Err("precision must be between 1 and 100".to_range_error());
      }

      format!("{:.*}", precision as usize, number).to_val()
    }
    _ => return Err(format!("TODO: number indirection").to_val()),
  })
});

static TO_EXPONENTIAL: NativeFunction = native_fn(|this, params| {
  Ok(match this.get() {
    Val::Number(number) => match params.get(0) {
      Some(p) => {
        let mut precision = p.to_number();
        precision = f64::floor(precision);

        if precision < 0.0 || precision > 100.0 {
          return Err("precision must be between 0 and 100".to_range_error());
        }

        format_exponential(*number, Some(precision as usize))
      }
      None => format_exponential(*number, None),
    },
    _ => return Err("number indirection".to_internal_error()),
  })
});

static TODO_LOCALE: NativeFunction = native_fn(|this, _params| match this.get() {
  Val::Number(_number) => return Err("TODO: locale".to_internal_error()),
  _ => return Err("number indirection".to_internal_error()),
});

static TO_STRING: NativeFunction = native_fn(|this, params| {
  Ok(match this.get() {
    Val::Number(number) => match params.get(0) {
      Some(_) => {
        return Err("TODO: toString with radix".to_internal_error());
      }

      None => number.to_val().to_string().to_val(),
    },
    _ => return Err("number indirection".to_internal_error()),
  })
});

static VALUE_OF: NativeFunction = native_fn(|this, _params| {
  Ok(match this.get() {
    Val::Number(number) => Val::Number(*number),
    _ => return Err("number indirection".to_internal_error()),
  })
});

fn format_exponential(number: f64, precision: Option<usize>) -> Val {
  if number.is_infinite() {
    return if number.is_sign_positive() {
      "Infinity"
    } else {
      "-Infinity"
    }
    .to_val();
  }

  let exp_format = match precision {
    Some(p) => format!("{:.*e}", p, number),
    None => format!("{:e}", number),
  };

  let mut parts = exp_format.splitn(2, 'e');

  let mantissa = parts.next().unwrap();

  let exponent = match parts.next() {
    Some(e) => e,
    None => return exp_format.to_val(),
  };

  let string = if exponent.starts_with('-') {
    format!("{}e{}", mantissa, exponent)
  } else {
    format!("{}e+{}", mantissa, exponent)
  };

  string.to_val()
}