gfx_macros 0.1.4

// Copyright 2014 The Gfx-rs Developers.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use syntax::{ast, ext};
use syntax::ext::build::AstBuilder;
use syntax::ext::deriving::generic;
use syntax::codemap;
use syntax::parse::token;
use syntax::ptr::P;
use syntax::ext::base::ItemDecorator;

#[derive(Copy, PartialEq, Debug)]
enum Param {
    Uniform,
    Block,
    Texture,
}

#[derive(Copy, Debug)]
enum ParamError {
    DeprecatedTexture,
}

/// Classify variable types (`i32`, `TextureParam`, etc) into the `Param`
fn classify(node: &ast::Ty_) -> Result<Param, ParamError> {
    match *node {
        ast::TyPath(ref path, _) => match path.segments.last() {
            Some(segment) => match segment.identifier.name.as_str() {
                "RawBufferHandle" => Ok(Param::Block),
                "TextureParam" => Ok(Param::Texture),
                "TextureHandle" => Err(ParamError::DeprecatedTexture),
                _ => Ok(Param::Uniform),
            },
            None => Ok(Param::Uniform),
        },
        _ => Ok(Param::Uniform),
    }
}

/// Generates the the method body for `gfx::shade::ParamValues::create_link`
fn method_create(cx: &mut ext::base::ExtCtxt, span: codemap::Span,
                 substr: &generic::Substructure,
                 link_name: &str,
                 path_root: ast::Ident) -> P<ast::Expr> {
    let link_ident = cx.ident_of(link_name);
    match *substr.fields {
        generic::StaticStruct(definition, generic::Named(ref fields)) => {
            let init_expr = cx.expr_struct_ident(
                span, link_ident,
                fields.iter().map(|&(fname, fspan)| {
                    cx.field_imm(fspan, fname, cx.expr_none(fspan))
                }).collect()
            );
            let class_info: Vec<(Param, P<ast::Expr>)> = definition.fields.iter()
                    .zip(fields.iter()).scan((), |_, (def, &(fname, fspan))|
                match classify(&def.node.ty.node) {
                    Ok(c) => {
                        let name = match super::find_name(cx, span, &def.node.attrs[]) {
                            Some(name) => name,
                            None => token::get_ident(fname),
                        };
                        Some((c, cx.expr_str(fspan, name)))
                    },
                    Err(e) => {
                        cx.span_err(fspan, &format!(
                            "Unrecognized parameter ({:?}) type {:?}",
                            fname.as_str(), e
                            )[]
                        );
                        None
                    },
                }
            ).collect();
            let gen_arms = |&: ptype: Param, var: ast::Ident| -> Vec<ast::Arm> {
                class_info.iter().zip(fields.iter())
                          .filter(|&(&(ref class, _), _)| *class == ptype)
                          .map(|(&(_, ref name_expr), &(fname, fspan))|
                    cx.arm(fspan,
                        vec![cx.pat_lit(fspan, name_expr.clone())],
                        quote_expr!(cx,
                            out.$fname = Some(i as $path_root::gfx::shade::$var)
                        )
                    )
                ).collect()
            };
            let uniform_arms = gen_arms(Param::Uniform, cx.ident_of("VarUniform"));
            let block_arms = gen_arms(Param::Block, cx.ident_of("VarBlock"));
            let texture_arms = gen_arms(Param::Texture, cx.ident_of("VarTexture"));
            let input = &substr.nonself_args[1];
            quote_expr!(cx, {
                let mut out = $init_expr;
                for (i, u) in $input.uniforms.iter().enumerate() {
                    let _ = i; // suppress warning about unused i
                    match &u.name[] {
                        $uniform_arms
                        _ => return Err($path_root::gfx::shade::
                            ParameterError::MissingUniform(u.name.clone())),
                    }
                }
                for (i, b) in $input.blocks.iter().enumerate() {
                    let _ = i; // suppress warning about unused i
                    match &b.name[] {
                        $block_arms
                        _ => return Err($path_root::gfx::shade::
                            ParameterError::MissingBlock(b.name.clone())),
                    }
                }
                for (i, t) in $input.textures.iter().enumerate() {
                    let _ = i; // suppress warning about unused i
                    match &t.name[] {
                        $texture_arms
                        _ => return Err($path_root::gfx::shade::
                            ParameterError::MissingTexture(t.name.clone())),
                    }
                }
                Ok(out)
            })
        },
        _ => {
            cx.span_err(span, "Unable to implement `ShaderParam::create_link()` on a non-structure");
            cx.expr_tuple(span, vec![])
        },
    }
}

/// Generates the the method body for `gfx::shade::ParamValues::fill_params`
fn method_fill(cx: &mut ext::base::ExtCtxt, span: codemap::Span,
               substr: &generic::Substructure,
               definition: P<ast::StructDef>,
               path_root: ast::Ident)
               -> P<ast::Expr> {
    match *substr.fields {
        generic::Struct(ref fields) => {
            let out = &substr.nonself_args[1];
            let max_num = cx.expr_usize(span, fields.len());
            let mut calls = vec![
                cx.stmt_item(span, cx.item_use_simple(
                    span,
                    ast::Inherited,
                    cx.path(span, vec![
                        cx.ident_of("self"),
                        path_root,
                        cx.ident_of("gfx"),
                        cx.ident_of("shade"),
                        cx.ident_of("ToUniform"),
                    ])
                )),
                quote_stmt!(cx, $out.uniforms.reserve($max_num);),
                quote_stmt!(cx, $out.blocks.reserve($max_num);),
                quote_stmt!(cx, $out.textures.reserve($max_num);),
            ];
            calls.extend(definition.fields.iter().zip(fields.iter())
                                   .map(|(def, f)| {
                let value_id = &f.self_;
                let var_id = cx.expr_field_access(
                    span,
                    substr.nonself_args[0].clone(),
                    f.name.unwrap()
                    );
                match classify(&def.node.ty.node) {
                    Ok(Param::Uniform) => quote_stmt!(cx,
                        $var_id.map_or((), |id| {
                            if $out.uniforms.len() <= id as usize {
                                unsafe { $out.uniforms.set_len(id as usize + 1) }
                            }
                            *$out.uniforms.get_mut(id as usize).unwrap() = $value_id.to_uniform()
                        })
                    ),
                    Ok(Param::Block)   => quote_stmt!(cx,
                        $var_id.map_or((), |id| {
                            if $out.blocks.len() <= id as usize {
                                unsafe { $out.blocks.set_len(id as usize + 1) }
                            }
                            *$out.blocks.get_mut(id as usize).unwrap() = {$value_id}
                        })
                    ),
                    Ok(Param::Texture) => quote_stmt!(cx,
                        $var_id.map_or((), |id| {
                            if $out.textures.len() <= id as usize {
                                unsafe { $out.textures.set_len(id as usize + 1) }
                            }
                            *$out.textures.get_mut(id as usize).unwrap() = {$value_id}
                        })
                    ),
                    Err(_) => {
                        cx.span_err(span, &format!(
                            "Invalid uniform: {:?}",
                            f.name.unwrap().as_str(),
                            )[]
                        );
                        cx.stmt_expr(cx.expr_usize(span, 0))
                    },
                }
            }));
            cx.expr_block(cx.block_all(span, calls, None))
        },
        _ => {
            cx.span_err(span, "Unable to implement `ShaderParam::bind()` on a non-structure");
            cx.expr_tuple(span, vec![])
        }
    }
}

/// A helper function that translates variable type (`i32`, `TextureHandle`, etc)
/// into the corresponding shader var id type (`VarUniform`, `VarBlock`, or `VarTexture`)
fn node_to_var_type(cx: &mut ext::base::ExtCtxt,
                    span: codemap::Span, node: &ast::Ty_,
                    path_root: ast::Ident) -> P<ast::Ty> {
    let id = match classify(node) {
        Ok(Param::Uniform) => "VarUniform",
        Ok(Param::Block)   => "VarBlock",
        Ok(Param::Texture) => "VarTexture",
        Err(ParamError::DeprecatedTexture) => {
            cx.span_err(span, "Use gfx::shade::TextureParam for texture vars instead of gfx::shade::TextureHandle");
            ""
        },
    };
    cx.ty_option(cx.ty_path(
        cx.path(span, vec![
            path_root,
            cx.ident_of("gfx"),
            cx.ident_of("shade"),
            cx.ident_of(id),
        ]),
    ))
}

#[derive(Copy)]
pub struct ShaderParam;

impl ItemDecorator for ShaderParam {
    /// Decorator for `shader_param` attribute
    fn expand(&self, context: &mut ext::base::ExtCtxt, span: codemap::Span,
              meta_item: &ast::MetaItem, item: &ast::Item,
              mut push: Box<FnMut(P<ast::Item>)>) {
        // Insert the `gfx` reexport module
        let path_root = super::extern_crate_hack(context, span, |i| (*push)(i));

        // constructing the Link struct
        let (base_def, link_def) = match item.node {
            ast::ItemStruct(ref definition, ref generics) => {
                if generics.lifetimes.len() > 0 {
                    context.bug("Lifetimes are not allowed in ShaderParam struct");
                }
                (definition, ast::StructDef {
                    fields: definition.fields.iter()
                        .map(|f| codemap::Spanned {
                            node: ast::StructField_ {
                                kind: f.node.kind,
                                id: f.node.id,
                                ty: node_to_var_type(context, f.span, &f.node.ty.node, path_root),
                                attrs: Vec::new(),
                            },
                            span: f.span,
                        }).collect(),
                    ctor_id: None,
                })
            },
            _ => {
                context.span_err(span, "Only free-standing named structs allowed to derive ShaderParam");
                return;
            }
        };
        let link_name = format!("_{}Link", item.ident.as_str());
        let link_ident = context.ident_of(&link_name[]);
        let link_ty = generic::ty::Literal(
            generic::ty::Path::new_local(&link_name[])
        );
        let link_item = context.item_struct(span, link_ident, link_def)
                               .map(|mut item| {
            item.attrs.push(context.attribute(span,
                context.meta_list(span, token::InternedString::new("derive"), vec![
                        context.meta_word(span, token::InternedString::new("Copy")),
                        context.meta_word(span, token::InternedString::new("Debug")),
                ])
            ));
            item
        });
        (*push)(link_item);

        // process meta parameters (expecting none)
        match meta_item.node {
            ast::MetaWord(_) => (), //expected
            _ => {
                context.span_warn(meta_item.span,
                    "No arguments are expected for #[shader_param]")
            }
        }

        // #[derive ShaderParam]
        let trait_def = generic::TraitDef {
            span: span,
            attributes: Vec::new(),
            path: generic::ty::Path {
                path: vec![super::EXTERN_CRATE_HACK, "gfx", "shade", "ShaderParam"],
                lifetime: None,
                params: Vec::new(),
                global: false,
            },
            additional_bounds: Vec::new(),
            generics: generic::ty::LifetimeBounds::empty(),
            methods: vec![
                generic::MethodDef {
                    name: "create_link",
                    generics: generic::ty::LifetimeBounds::empty(),
                    explicit_self: None,
                    args: vec![
                        generic::ty::Literal(generic::ty::Path {
                            path: vec!["Option"],
                            lifetime: None,
                            params: vec![
                                box generic::ty::Ptr(
                                    box generic::ty::Self,
                                    generic::ty::Borrowed(None, ast::MutImmutable)
                                ),
                            ],
                            global: false,
                        }),
                        generic::ty::Ptr(
                            box generic::ty::Literal(generic::ty::Path::new(
                                vec![super::EXTERN_CRATE_HACK, "gfx", "ProgramInfo"])),
                            generic::ty::Borrowed(None, ast::MutImmutable)
                        ),
                    ],
                    ret_ty: generic::ty::Literal(
                        generic::ty::Path {
                            path: vec!["Result"],
                            lifetime: None,
                            params: vec![
                                box link_ty.clone(),
                                box generic::ty::Literal(generic::ty::Path::new(
                                    vec![super::EXTERN_CRATE_HACK, "gfx", "shade", "ParameterError"]
                                ))
                            ],
                            global: false,
                        },
                    ),
                    attributes: Vec::new(),
                    combine_substructure: generic::combine_substructure(box |cx, span, sub|
                        method_create(cx, span, sub, &link_name[], path_root)
                    ),
                },
                generic::MethodDef {
                    name: "fill_params",
                    generics: generic::ty::LifetimeBounds::empty(),
                    explicit_self: Some(Some(generic::ty::Borrowed(
                        None, ast::MutImmutable
                    ))),
                    args: vec![
                        generic::ty::Ptr(
                            box link_ty.clone(),
                            generic::ty::Borrowed(None, ast::MutImmutable)
                        ),
                        generic::ty::Literal(
                            generic::ty::Path::new(vec![super::EXTERN_CRATE_HACK, "gfx", "shade", "ParamValues"]),
                        ),
                    ],
                    ret_ty: generic::ty::Tuple(Vec::new()),
                    attributes: Vec::new(),
                    combine_substructure: generic::combine_substructure(box |cx, span, sub|
                        method_fill(cx, span, sub, base_def.clone(), path_root)
                    ),
                },
            ],
            associated_types: vec![
                (context.ident_of("Link"), link_ty),
            ],
        };
        let fixup = |item| {
            (*push)(super::fixup_extern_crate_paths(item, path_root))
        };
        trait_def.expand(context, meta_item, item, fixup);
    }
}