ruststep-derive 0.3.0

use super::*;

use proc_macro_error::{Diagnostic, Level};
use std::convert::{TryFrom, TryInto};

/// espr-generated field type
#[derive(Debug, Clone)]
pub enum FieldType {
    /// Like `T`
    Path(syn::Path),
    /// Like `Option<T>`
    Optional(Box<FieldType>),
    /// Like `Vec<T>`
    List(Box<FieldType>),
    /// Like `Box<T>`
    Boxed(Box<FieldType>),
}

impl FieldType {
    pub fn as_holder(self) -> Self {
        match self {
            FieldType::Path(path) => {
                let syn::Path {
                    leading_colon,
                    mut segments,
                } = path;
                let mut last_seg = segments.last_mut().unwrap();
                match &mut last_seg.arguments {
                    syn::PathArguments::None => {
                        last_seg.ident = as_holder_ident(&last_seg.ident);
                    }
                    _ => unreachable!(),
                }
                FieldType::Path(syn::Path {
                    leading_colon,
                    segments,
                })
            }
            FieldType::Optional(ty) => {
                let holder = ty.as_holder();
                FieldType::Optional(Box::new(holder))
            }
            FieldType::List(ty) => {
                let holder = ty.as_holder();
                FieldType::List(Box::new(holder))
            }
            FieldType::Boxed(ty) => {
                let holder = ty.as_holder();
                FieldType::Boxed(Box::new(holder))
            }
        }
    }

    pub fn as_place_holder(self) -> Self {
        let ruststep = ruststep_crate();
        match self {
            FieldType::Path(path) => {
                let path = syn::parse_quote! { #ruststep::tables::PlaceHolder<#path> };
                FieldType::Path(path)
            }
            FieldType::Optional(ty) => {
                let place_holder = ty.as_place_holder();
                FieldType::Optional(Box::new(place_holder))
            }
            FieldType::List(ty) => {
                let place_holder = ty.as_place_holder();
                FieldType::List(Box::new(place_holder))
            }
            FieldType::Boxed(ty) => {
                let place_holder = ty.as_place_holder();
                FieldType::Boxed(Box::new(place_holder))
            }
        }
    }
}

#[derive(Debug, Clone)]
pub struct UnsupportedTypeError {}

impl Into<Diagnostic> for UnsupportedTypeError {
    fn into(self) -> Diagnostic {
        Diagnostic::new(
            Level::Error,
            "Unsupported Type for ruststep and espr".to_string(),
        )
    }
}

impl Into<syn::Type> for FieldType {
    fn into(self) -> syn::Type {
        let path = match self {
            FieldType::Path(path) => path,
            FieldType::Optional(ty) => {
                let ty: syn::Type = (*ty).into();
                syn::parse_quote! { Option<#ty> }
            }
            FieldType::List(ty) => {
                let ty: syn::Type = (*ty).into();
                syn::parse_quote! { Vec<#ty> }
            }
            FieldType::Boxed(ty) => {
                let ty: syn::Type = (*ty).into();
                syn::parse_quote! { Box<#ty> }
            }
        };
        syn::Type::Path(syn::TypePath { qself: None, path })
    }
}

impl TryFrom<syn::Type> for FieldType {
    type Error = UnsupportedTypeError;

    fn try_from(ty: syn::Type) -> Result<Self, Self::Error> {
        let path = if let syn::Type::Path(syn::TypePath { path, .. }) = ty {
            path
        } else {
            return Err(UnsupportedTypeError {});
        };

        let syn::Path { segments, .. } = &path;
        let last_seg = segments.last().unwrap();

        match &last_seg.arguments {
            syn::PathArguments::None => Ok(FieldType::Path(path.clone())),
            syn::PathArguments::AngleBracketed(syn::AngleBracketedGenericArguments {
                args,
                ..
            }) => {
                assert_eq!(args.len(), 1);
                if let syn::GenericArgument::Type(ty) = &args[0] {
                    let ty = Box::new(ty.clone().try_into()?);
                    if last_seg.ident == "Option" {
                        return Ok(FieldType::Optional(ty));
                    }
                    if last_seg.ident == "Vec" {
                        return Ok(FieldType::List(ty));
                    }
                    if last_seg.ident == "Box" {
                        return Ok(FieldType::Boxed(ty));
                    }
                }
                Err(UnsupportedTypeError {})
            }
            _ => Err(UnsupportedTypeError {}),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn field_type_convert() {
        let ty: syn::Type = syn::parse_str("T").unwrap();
        let f = ty.clone().try_into().unwrap();
        assert!(matches!(f, FieldType::Path(_)));
        assert_eq!(<FieldType as Into<syn::Type>>::into(f), ty);

        let ty: syn::Type = syn::parse_str("Option<T>").unwrap();
        let f = ty.clone().try_into().unwrap();
        assert!(matches!(f, FieldType::Optional(_)));
        assert_eq!(<FieldType as Into<syn::Type>>::into(f), ty);

        let ty: syn::Type = syn::parse_str("Vec<T>").unwrap();
        let f = ty.clone().try_into().unwrap();
        assert!(matches!(f, FieldType::List(_)));
        assert_eq!(<FieldType as Into<syn::Type>>::into(f), ty);

        let ty: syn::Type = syn::parse_str("Option<Vec<T>>").unwrap();
        let f = ty.clone().try_into().unwrap();
        if let FieldType::Optional(ty) = &f {
            assert!(matches!(**ty, FieldType::List(_)));
        } else {
            panic!()
        }
        assert_eq!(<FieldType as Into<syn::Type>>::into(f), ty);
    }

    #[test]
    fn as_holder() {
        let ty: syn::Type = syn::parse_str("T").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let holder = f.as_holder();
        let ans: syn::Type = syn::parse_str("THolder").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(holder), ans);

        let ty: syn::Type = syn::parse_str("Option<T>").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let holder = f.as_holder();
        let ans: syn::Type = syn::parse_str("Option<THolder>").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(holder), ans);

        let ty: syn::Type = syn::parse_str("Vec<T>").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let holder = f.as_holder();
        let ans: syn::Type = syn::parse_str("Vec<THolder>").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(holder), ans);

        let ty: syn::Type = syn::parse_str("Option<Vec<T>>").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let holder = f.as_holder();
        let ans: syn::Type = syn::parse_str("Option<Vec<THolder>>").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(holder), ans);
    }

    #[test]
    fn as_place_holder() {
        let ty: syn::Type = syn::parse_str("T").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let place_holder = f.as_holder().as_place_holder();
        let ans: syn::Type = syn::parse_str("::ruststep::tables::PlaceHolder<THolder>").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(place_holder), ans);

        let ty: syn::Type = syn::parse_str("Option<T>").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let place_holder = f.as_holder().as_place_holder();
        let ans: syn::Type =
            syn::parse_str("Option<::ruststep::tables::PlaceHolder<THolder>>").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(place_holder), ans);

        let ty: syn::Type = syn::parse_str("Vec<T>").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let place_holder = f.as_holder().as_place_holder();
        let ans: syn::Type =
            syn::parse_str("Vec<::ruststep::tables::PlaceHolder<THolder>>").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(place_holder), ans);

        let ty: syn::Type = syn::parse_str("Option<Vec<T>>").unwrap();
        let f: FieldType = ty.try_into().unwrap();
        let place_holder = f.as_holder().as_place_holder();
        let ans: syn::Type =
            syn::parse_str("Option<Vec<::ruststep::tables::PlaceHolder<THolder>>>").unwrap();
        assert_eq!(<FieldType as Into<syn::Type>>::into(place_holder), ans);
    }
}