use fix_error::Error;
use fix_lang::StringId;
use fix_runtime::{
    BytecodeReader, Machine, MachineExt, NixString, NixType, Path, Step, StrictValue, Value,
    VmRuntimeCtx,
};
use gc_arena::Mutation;

pub fn to_string<'gc, M: Machine<'gc>>(
    m: &mut M,
    _ctx: &mut impl VmRuntimeCtx,
    reader: &mut BytecodeReader<'_>,
    mc: &Mutation<'gc>,
) -> Step {
    let val = m.force_and_retry::<StrictValue>(reader, mc)?;
    if val.is::<StringId>() || val.is::<NixString>() {
        return m.return_from_primop(val.relax(), reader);
    }
    if let Some(p) = val.downcast::<Path>() {
        return m.return_from_primop(Value::new(p.0), reader);
    }
    //  TODO: derivations / `__toString` / `outPath`,
    //        numbers, lists.
    m.finish_err(Error::eval_error(format!(
        "cannot coerce {} to a string",
        val.ty()
    )))
}

pub fn type_of<'gc, M: Machine<'gc>>(
    m: &mut M,
    ctx: &mut impl VmRuntimeCtx,
    reader: &mut BytecodeReader<'_>,
    mc: &Mutation<'gc>,
) -> Step {
    let val = m.force_and_retry::<StrictValue>(reader, mc)?;
    let name: &str = match val.ty() {
        NixType::Int => "int",
        NixType::Float => "float",
        NixType::Bool => "bool",
        NixType::Null => "null",
        NixType::String => "string",
        NixType::Path => "path",
        NixType::AttrSet => "set",
        NixType::List => "list",
        NixType::Closure | NixType::PrimOp | NixType::PrimOpApp => "lambda",
        NixType::Thunk => unreachable!("forced"),
    };
    let sid = ctx.intern_string(name);
    m.return_from_primop(Value::new(sid), reader)
}