cglue-gen 0.2.0

use proc_macro2::TokenStream;
use quote::*;
use std::collections::{HashMap, HashSet};
use syn::parse::{Parse, ParseStream};
use syn::punctuated::Punctuated;
use syn::token::{Comma, Gt, Lt};
use syn::*;

fn ident_path(ident: Ident) -> Type {
    let mut path = Path {
        leading_colon: None,
        segments: Punctuated::new(),
    };

    path.segments.push_value(PathSegment {
        ident,
        arguments: Default::default(),
    });

    Type::Path(TypePath { qself: None, path })
}

fn ty_ident(ty: &Type) -> Option<&Ident> {
    if let Type::Path(path) = ty {
        if path.qself.is_none() {
            path.path.get_ident()
        } else {
            None
        }
    } else {
        None
    }
}

#[derive(Clone)]
pub struct ParsedGenerics {
    /// Lifetime declarations on the left side of the type/trait.
    ///
    /// This may include any bounds it contains, for instance: `'a: 'b,`.
    pub life_declare: Punctuated<LifetimeDef, Comma>,
    /// Declarations "using" the lifetimes i.e. has bounds stripped.
    ///
    /// For instance: `'a: 'b,` becomes just `'a,`.
    pub life_use: Punctuated<Lifetime, Comma>,
    /// Type declarations on the left side of the type/trait.
    ///
    /// This may include any trait bounds it contains, for instance: `T: Clone,`.
    pub gen_declare: Punctuated<TypeParam, Comma>,
    /// Declarations that "use" the traits i.e. has bounds stripped.
    ///
    /// For instance: `T: Clone,` becomes just `T,`.
    pub gen_use: Punctuated<Type, Comma>,
    /// All where predicates, without the `where` keyword.
    pub gen_where_bounds: Punctuated<WherePredicate, Comma>,
    /// Remap generic T to a particular type using T = type syntax.
    ///
    /// Then, when generics get cross referenced, all concrete T declarations get removed, and T
    /// uses get replaced with concrete types.
    pub gen_remaps: HashMap<Ident, Type>,
}

impl ParsedGenerics {
    pub fn declare_without_nonstatic_bounds(&self) -> Punctuated<TypeParam, Comma> {
        let mut ret = self.gen_declare.clone();

        for p in ret.iter_mut() {
            p.bounds = std::mem::take(&mut p.bounds)
                .into_iter()
                .filter(|b| {
                    if let TypeParamBound::Lifetime(lt) = b {
                        lt.ident == "static"
                    } else {
                        true
                    }
                })
                .collect();
        }

        ret
    }

    #[cfg(feature = "layout_checks")]
    pub fn declare_lt_for_all(&self, lt: &TokenStream) -> TokenStream {
        let mut ts = TokenStream::new();

        for p in &self.gen_use {
            ts.extend(quote!(#p: #lt,));
        }

        ts
    }

    #[cfg(not(feature = "layout_checks"))]
    pub fn declare_lt_for_all(&self, _: &TokenStream) -> TokenStream {
        Default::default()
    }

    pub fn declare_sabi_for_all(&self, crate_path: &TokenStream) -> TokenStream {
        let mut ts = TokenStream::new();

        for p in &self.gen_use {
            ts.extend(quote!(#p: #crate_path::trait_group::GenericTypeBounds,));
        }

        ts
    }

    /// This function cross references input lifetimes and returns a new Self
    /// that only contains generic type information about those types.
    pub fn cross_ref<'a>(&self, input: impl IntoIterator<Item = &'a ParsedGenerics>) -> Self {
        let mut applied_lifetimes = HashSet::<&Ident>::new();
        let mut applied_typenames = HashSet::<&Type>::new();

        let mut life_declare = Punctuated::new();
        let mut life_use = Punctuated::new();
        let mut gen_declare = Punctuated::new();
        let mut gen_use = Punctuated::<Type, _>::new();
        let mut gen_where_bounds = Punctuated::new();

        for ParsedGenerics {
            life_use: in_lu,
            gen_use: in_gu,
            ..
        } in input
        {
            for lt in in_lu.iter() {
                if applied_lifetimes.contains(&lt.ident) {
                    continue;
                }

                let decl = self
                    .life_declare
                    .iter()
                    .find(|ld| ld.lifetime.ident == lt.ident)
                    .expect("Gen 1");

                life_declare.push_value(decl.clone());
                life_declare.push_punct(Default::default());
                life_use.push_value(decl.lifetime.clone());
                life_use.push_punct(Default::default());

                applied_lifetimes.insert(&lt.ident);
            }

            for ty in in_gu.iter() {
                if applied_typenames.contains(&ty) {
                    continue;
                }

                let (decl, ident) = self
                    .gen_declare
                    .iter()
                    .zip(self.gen_use.iter())
                    .find(|(_, ident)| *ident == ty)
                    .expect("Gen 2");

                gen_declare.push_value(decl.clone());
                gen_declare.push_punct(Default::default());
                gen_use.push_value(ident_path(decl.ident.clone()));
                gen_use.push_punct(Default::default());

                applied_typenames.insert(ident);
            }
        }

        for wb in self.gen_where_bounds.iter() {
            if match wb {
                WherePredicate::Type(ty) => applied_typenames.contains(&ty.bounded_ty),
                WherePredicate::Lifetime(lt) => applied_lifetimes.contains(&lt.lifetime.ident),
                _ => false,
            } {
                gen_where_bounds.push_value(wb.clone());
                gen_where_bounds.push_punct(Default::default());
            }
        }

        Self {
            life_declare,
            life_use,
            gen_declare,
            gen_use,
            gen_where_bounds,
            gen_remaps: Default::default(),
        }
    }

    pub fn merge_remaps(&mut self, other: &mut ParsedGenerics) {
        self.gen_remaps
            .extend(std::mem::take(&mut other.gen_remaps));
        other.gen_remaps = self.gen_remaps.clone();
    }

    pub fn merge_and_remap(&mut self, other: &mut ParsedGenerics) {
        self.merge_remaps(other);
        self.remap_types();
        other.remap_types();
    }

    pub fn remap_types(&mut self) {
        let old_gen_declare = std::mem::take(&mut self.gen_declare);
        let old_gen_use = std::mem::take(&mut self.gen_use);

        for val in old_gen_declare.into_pairs() {
            match val {
                punctuated::Pair::Punctuated(p, punc) => {
                    if !self.gen_remaps.contains_key(&p.ident) {
                        self.gen_declare.push_value(p);
                        self.gen_declare.push_punct(punc);
                    }
                }
                punctuated::Pair::End(p) => {
                    if !self.gen_remaps.contains_key(&p.ident) {
                        self.gen_declare.push_value(p);
                    }
                }
            }
        }

        for val in old_gen_use.into_pairs() {
            match val {
                punctuated::Pair::Punctuated(p, punc) => {
                    if let Some(ident) = ty_ident(&p) {
                        self.gen_use
                            .push_value(self.gen_remaps.get(ident).cloned().unwrap_or(p));
                    } else {
                        self.gen_use.push_value(p);
                    }
                    self.gen_use.push_punct(punc);
                }
                punctuated::Pair::End(p) => {
                    if let Some(ident) = ty_ident(&p) {
                        self.gen_use
                            .push_value(self.gen_remaps.get(ident).cloned().unwrap_or(p));
                    } else {
                        self.gen_use.push_value(p);
                    }
                }
            }
        }
    }

    /// Generate phantom data definitions for all lifetimes and types used.
    pub fn phantom_data_definitions(&self) -> TokenStream {
        let mut stream = TokenStream::new();

        for ty in self.gen_declare.iter() {
            let ty_ident = format_ident!("_ty_{}", ty.ident.to_string().to_lowercase());
            let ty = &ty.ident;
            stream.extend(quote!(#ty_ident: ::core::marker::PhantomData<#ty>,));
        }

        stream
    }

    /// Generate phantom data initializations for all lifetimes and types used.
    pub fn phantom_data_init(&self) -> TokenStream {
        let mut stream = TokenStream::new();

        for ty in self.gen_declare.iter() {
            let ty_ident = format_ident!("_ty_{}", ty.ident.to_string().to_lowercase());
            stream.extend(quote!(#ty_ident: ::core::marker::PhantomData{},));
        }

        stream
    }
}

impl<'a> std::iter::FromIterator<&'a ParsedGenerics> for ParsedGenerics {
    fn from_iter<I: IntoIterator<Item = &'a ParsedGenerics>>(input: I) -> Self {
        let mut life_declare = Punctuated::new();
        let mut life_declared = HashSet::<&Ident>::new();

        let mut life_use = Punctuated::new();
        let mut gen_use = Punctuated::new();

        let mut gen_declare = Punctuated::new();
        let mut gen_declared = HashSet::<&Ident>::new();

        let mut gen_where_bounds = Punctuated::new();

        let mut gen_remaps = HashMap::default();

        for val in input {
            life_use.extend(val.life_use.clone());
            gen_use.extend(val.gen_use.clone());

            for life in val.life_declare.pairs() {
                let (val, punct) = life.into_tuple();
                if life_declared.contains(&val.lifetime.ident) {
                    continue;
                }
                life_declare.push_value(val.clone());
                if let Some(punct) = punct {
                    life_declare.push_punct(*punct);
                }
                life_declared.insert(&val.lifetime.ident);
            }

            for gen in val.gen_declare.pairs() {
                let (val, punct) = gen.into_tuple();
                if gen_declared.contains(&val.ident) {
                    continue;
                }
                gen_declare.push_value(val.clone());
                if let Some(punct) = punct {
                    gen_declare.push_punct(*punct);
                }
                gen_declared.insert(&val.ident);
            }

            gen_where_bounds.extend(val.gen_where_bounds.clone());
            gen_remaps.extend(val.gen_remaps.clone());
        }

        if !gen_where_bounds.empty_or_trailing() {
            gen_where_bounds.push_punct(Default::default());
        }

        Self {
            life_declare,
            life_use,
            gen_declare,
            gen_use,
            gen_where_bounds,
            gen_remaps,
        }
    }
}

impl From<Option<&Punctuated<GenericArgument, Comma>>> for ParsedGenerics {
    fn from(input: Option<&Punctuated<GenericArgument, Comma>>) -> Self {
        match input {
            Some(input) => Self::from(input),
            _ => Self {
                life_declare: Punctuated::new(),
                life_use: Punctuated::new(),
                gen_declare: Punctuated::new(),
                gen_use: Punctuated::new(),
                gen_where_bounds: Punctuated::new(),
                gen_remaps: Default::default(),
            },
        }
    }
}

impl From<&Punctuated<GenericArgument, Comma>> for ParsedGenerics {
    fn from(input: &Punctuated<GenericArgument, Comma>) -> Self {
        let mut life_declare = Punctuated::new();
        let mut life_use = Punctuated::new();
        let mut gen_declare = Punctuated::new();
        let mut gen_use = Punctuated::new();
        let mut gen_remaps = HashMap::new();

        for param in input {
            match param {
                GenericArgument::Type(ty) => {
                    if let Some(ident) = ty_ident(ty).cloned() {
                        gen_declare.push_value(TypeParam {
                            attrs: vec![],
                            ident,
                            colon_token: None,
                            bounds: Punctuated::new(),
                            eq_token: None,
                            default: None,
                        });
                        gen_declare.push_punct(Default::default());
                    }
                    gen_use.push_value(ty.clone());
                    gen_use.push_punct(Default::default());
                }
                GenericArgument::Const(_cn) => {
                    // TODO
                }
                GenericArgument::Lifetime(lifetime) => {
                    life_use.push_value(lifetime.clone());
                    life_use.push_punct(Default::default());
                    life_declare.push_value(LifetimeDef {
                        attrs: vec![],
                        lifetime: lifetime.clone(),
                        colon_token: None,
                        bounds: Punctuated::new(),
                    });
                    life_declare.push_punct(Default::default());
                }
                GenericArgument::Constraint(constraint) => {
                    gen_use.push_value(ident_path(constraint.ident.clone()));
                    gen_use.push_punct(Default::default());
                    gen_declare.push_value(TypeParam {
                        attrs: vec![],
                        ident: constraint.ident.clone(),
                        colon_token: None,
                        bounds: constraint.bounds.clone(),
                        eq_token: None,
                        default: None,
                    });
                    gen_declare.push_punct(Default::default());
                }
                GenericArgument::Binding(bind) => {
                    gen_use.push_value(bind.ty.clone());
                    gen_use.push_punct(Default::default());
                    gen_remaps.insert(bind.ident.clone(), bind.ty.clone());
                }
            }
        }

        Self {
            life_declare,
            life_use,
            gen_declare,
            gen_use,
            gen_where_bounds: Punctuated::new(),
            gen_remaps,
        }
    }
}

impl From<&Generics> for ParsedGenerics {
    fn from(input: &Generics) -> Self {
        let gen_where = &input.where_clause;
        let gen_where_bounds = gen_where.as_ref().map(|w| &w.predicates);

        let mut life_declare = Punctuated::new();
        let mut life_use = Punctuated::new();
        let mut gen_declare = Punctuated::new();
        let mut gen_use = Punctuated::new();

        for param in input.params.iter() {
            match param {
                GenericParam::Type(ty) => {
                    gen_use.push_value(ident_path(ty.ident.clone()));
                    gen_use.push_punct(Default::default());
                    gen_declare.push_value(ty.clone());
                    gen_declare.push_punct(Default::default());
                }
                GenericParam::Const(_cn) => {
                    // TODO
                }
                GenericParam::Lifetime(lt) => {
                    let lifetime = &lt.lifetime;
                    life_use.push_value(lifetime.clone());
                    life_use.push_punct(Default::default());
                    life_declare.push_value(lt.clone());
                    life_declare.push_punct(Default::default());
                }
            }
        }

        Self {
            life_declare,
            life_use,
            gen_declare,
            gen_use,
            gen_where_bounds: gen_where_bounds.cloned().unwrap_or_else(Punctuated::new),
            gen_remaps: Default::default(),
        }
    }
}

fn parse_generic_arguments(input: ParseStream) -> Punctuated<GenericArgument, Comma> {
    let mut punct = Punctuated::new();

    while let Ok(arg) = input.parse::<GenericArgument>() {
        punct.push_value(arg);

        if let Ok(comma) = input.parse::<Comma>() {
            punct.push_punct(comma);
        } else {
            break;
        }
    }

    punct
}

impl Parse for ParsedGenerics {
    fn parse(input: ParseStream) -> Result<Self> {
        let gens = match input.parse::<Lt>() {
            Ok(_) => {
                let punct = parse_generic_arguments(input);
                input.parse::<Gt>()?;
                Some(punct)
            }
            _ => None,
        };

        let ret = Self::from(gens.as_ref());

        if let Ok(mut clause) = input.parse::<WhereClause>() {
            if !clause.predicates.trailing_punct() {
                clause.predicates.push_punct(Default::default());
            }

            let predicates = &clause.predicates;

            Ok(Self {
                gen_where_bounds: predicates.clone(),
                ..ret
            })
        } else {
            Ok(ret)
        }
    }
}

pub struct GenericCastType {
    pub ident: Box<Expr>,
    pub target: GenericType,
}

impl Parse for GenericCastType {
    fn parse(input: ParseStream) -> Result<Self> {
        let cast: ExprCast = input.parse()?;

        let ident = cast.expr;
        let target = GenericType::from_type(&*cast.ty, true);

        Ok(Self { ident, target })
    }
}

#[derive(Clone)]
pub struct GenericType {
    pub path: Path,
    pub gen_separator: TokenStream,
    pub generics: TokenStream,
    pub target: TokenStream,
}

impl GenericType {
    pub fn push_lifetime_start(&mut self, lifetime: &Lifetime) {
        let gen = &self.generics;
        self.generics = quote!(#lifetime, #gen);
    }

    pub fn push_types_start(&mut self, types: TokenStream) {
        let generics = std::mem::replace(&mut self.generics, TokenStream::new());

        let ParsedGenerics {
            life_declare,
            gen_declare,
            ..
        } = parse2::<ParsedGenerics>(quote!(<#generics>)).expect("Gen 3");

        self.generics
            .extend(quote!(#life_declare #types #gen_declare));
    }

    fn from_type(target: &Type, cast_to_group: bool) -> Self {
        let (path, target, generics) = match target {
            Type::Path(ty) => {
                let (path, target, generics) =
                    crate::util::split_path_ident(&ty.path).expect("Gen 3");
                (path, quote!(#target), generics)
            }
            x => (
                Path {
                    leading_colon: None,
                    segments: Default::default(),
                },
                quote!(#x),
                None,
            ),
        };

        let (gen_separator, generics) = match (cast_to_group, generics) {
            (true, Some(params)) => {
                let pg = ParsedGenerics::from(&params);

                let life = &pg.life_use;
                let gen = &pg.gen_use;

                (quote!(::), quote!(#life _, _, #gen))
            }
            (false, Some(params)) => (quote!(), quote!(#params)),
            (true, _) => (quote!(::), quote!()),
            _ => (quote!(), quote!()),
        };

        Self {
            path,
            gen_separator,
            generics,
            target,
        }
    }
}

impl ToTokens for GenericType {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        tokens.extend(self.path.to_token_stream());
        tokens.extend(self.target.clone());
        let generics = &self.generics;
        if !generics.is_empty() {
            tokens.extend(self.gen_separator.clone());
            tokens.extend(quote!(<#generics>));
        }
    }
}

impl Parse for GenericType {
    fn parse(input: ParseStream) -> Result<Self> {
        let target: Type = input.parse()?;
        Ok(Self::from_type(&target, false))
    }
}