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use std::borrow::Cow;

use crate::core::{Globals, Intern};
use crate::error::Error;
use crate::sys;
use crate::value::Value;
use crate::Artichoke;

// TODO: Handle invalid variable names. For now this is delegated to mruby.
// The parser in `spinoso-symbol` can handle this.

impl Globals for Artichoke {
    type Value = Value;

    type Error = Error;

    fn set_global_variable<T>(&mut self, name: T, value: &Self::Value) -> Result<(), Self::Error>
    where
        T: Into<Cow<'static, [u8]>>,
    {
        let sym = self.intern_bytes(name.into())?;
        unsafe {
            self.with_ffi_boundary(|mrb| sys::mrb_gv_set(mrb, sym, value.inner()))?;
        }
        Ok(())
    }

    /// Unset global variable pointed to by `name`.
    ///
    /// Unsetting a global variable removes the name from the global storage
    /// table. Unset globals resolve to `nil` in the Ruby VM.
    ///
    /// Unsetting a global that is currently unset is a no-op.
    ///
    /// # Errors
    ///
    /// If the name is not a valid global name, an error is returned.
    fn unset_global_variable<T>(&mut self, name: T) -> Result<(), Self::Error>
    where
        T: Into<Cow<'static, [u8]>>,
    {
        let sym = self.intern_bytes(name.into())?;
        let nil = Value::nil();
        unsafe {
            self.with_ffi_boundary(|mrb| sys::mrb_gv_set(mrb, sym, nil.inner()))?;
        }
        Ok(())
    }

    fn get_global_variable<T>(&mut self, name: T) -> Result<Option<Self::Value>, Self::Error>
    where
        T: Into<Cow<'static, [u8]>>,
    {
        let sym = self.intern_bytes(name.into())?;
        let value = unsafe { self.with_ffi_boundary(|mrb| sys::mrb_gv_get(mrb, sym))? };
        // NOTE: This implementation is not compliant with the spec laid out in
        // the trait documentation. This implementation always returns `Some(_)`
        // even if the global is unset.
        Ok(Some(Value::from(value)))
    }
}