use super::*;
use crate::box_trait::NyashBox;

pub(super) fn try_handle_string_box(
    this: &mut MirInterpreter,
    dst: Option<ValueId>,
    box_val: ValueId,
    method: &str,
    args: &[ValueId],
) -> Result<bool, VMError> {
        let recv = this.reg_load(box_val)?;
        let recv_box_any: Box<dyn NyashBox> = match recv.clone() {
            VMValue::BoxRef(b) => b.share_box(),
            other => other.to_nyash_box(),
        };
        if let Some(sb) = recv_box_any
            .as_any()
            .downcast_ref::<crate::box_trait::StringBox>()
        {
            match method {
                "length" => {
                    let ret = sb.length();
                    if let Some(d) = dst { this.regs.insert(d, VMValue::from_nyash_box(ret)); }
                    return Ok(true);
                }
                "substring" => {
                    if args.len() != 2 {
                        return Err(VMError::InvalidInstruction(
                            "substring expects 2 args (start, end)".into(),
                        ));
                    }
                    let s_idx = this.reg_load(args[0])?.as_integer().unwrap_or(0);
                    let e_idx = this.reg_load(args[1])?.as_integer().unwrap_or(0);
                    let len = sb.value.chars().count() as i64;
                    let start = s_idx.max(0).min(len) as usize;
                    let end = e_idx.max(start as i64).min(len) as usize;
                    let chars: Vec<char> = sb.value.chars().collect();
                    let sub: String = chars[start..end].iter().collect();
                    if let Some(d) = dst { this.regs.insert(d, VMValue::from_nyash_box(Box::new(crate::box_trait::StringBox::new(sub)))) ; }
                    return Ok(true);
                }
                "concat" => {
                    if args.len() != 1 {
                        return Err(VMError::InvalidInstruction("concat expects 1 arg".into()));
                    }
                    let rhs = this.reg_load(args[0])?;
                    let new_s = format!("{}{}", sb.value, rhs.to_string());
                    if let Some(d) = dst { this.regs.insert(d, VMValue::from_nyash_box(Box::new(crate::box_trait::StringBox::new(new_s)))) ; }
                    return Ok(true);
                }
                _ => {}
            }
        }
        Ok(false)
}