include-shader 0.2.0

//! A library to help working with shaders.
//!
//! Although this library works on `stable`, detection of shader file changes is not
//! guaranteed due to caching. Therefore, it is recommended to use `nightly` along with
//! the `track-path` feature enabled until the
//! [`track_path`](https://doc.rust-lang.org/stable/proc_macro/tracked_path/fn.path.html)
//! API stabilizes.
//!
//! ## Optional features
//! **`relative-path`** - Resolves path relative to the current file instead of relative
//! to the workspace root directory.
//!
//! **`track-path`** - Enables
//! [`file tracking`](https://doc.rust-lang.org/stable/proc_macro/tracked_path/fn.path.html)
//! to ensure detection of shader file changes.

#![cfg_attr(feature = "track-path", feature(track_path))]
#![cfg_attr(feature = "relative-path", feature(proc_macro_span))]

mod dependency_graph;

use dependency_graph::DependencyGraph;
use lazy_static::lazy_static;
use proc_macro::{Literal, TokenStream, TokenTree};
use regex::Regex;
use std::fs::{canonicalize, read_to_string};
use std::io;
use std::path::{Path, PathBuf};

fn resolve_path(path: &str, parent_dir_path: Option<PathBuf>) -> io::Result<PathBuf> {
    let mut path = PathBuf::from(path);
    if let Some(p) = parent_dir_path {
        if !path.is_absolute() {
            path = p.join(path);
        }
    }
    canonicalize(&path)
}

fn track_file(_path: &Path) {
    #[cfg(feature = "track-path")]
    proc_macro::tracked_path::path(_path.to_string_lossy());
}

fn process_file(path: &Path, dependency_graph: &mut DependencyGraph) -> String {
    let content = read_to_string(path).unwrap_or_else(|e| {
        panic!(
            "An error occured while trying to read file: {}. Error: {}",
            path.to_string_lossy(),
            e
        )
    });
    track_file(path);
    process_includes(path, content, dependency_graph)
}

fn process_includes(
    source_path: &Path,
    source_file_content: String,
    dependency_graph: &mut DependencyGraph,
) -> String {
    lazy_static! {
        static ref INCLUDE_RE: Regex = Regex::new(r#"#include\s+"(?P<file>.*)""#).unwrap();
    }
    let mut result = source_file_content;

    while let Some(captures) = INCLUDE_RE.captures(&result.clone()) {
        let capture = captures.get(0).unwrap();
        let file_path = captures.name("file").unwrap().as_str();

        #[allow(unused_assignments, unused_mut)]
        let mut include_parent_dir_path = None;

        #[cfg(feature = "relative-path")]
        {
            let mut path = source_path.to_path_buf();
            path.pop();
            include_parent_dir_path = Some(path);
        }

        let include_path = match resolve_path(&file_path, include_parent_dir_path) {
            Ok(path) => path,
            Err(e) => {
                panic!(
                    r#"An error occured while trying to resolve a dependency path: "{}". Error: {}"#,
                    &file_path,
                    e
                )
            }
        };

        dependency_graph.add_edge(
            source_path.to_string_lossy().to_string(),
            include_path.to_string_lossy().to_string(),
        );

        if let Some(cycle) = dependency_graph.find_cycle() {
            panic!("Circular dependency detected: {}", cycle.join(" -> "));
        }

        result.replace_range(
            capture.start()..capture.end(),
            &process_file(&include_path, dependency_graph),
        );
    }

    result
}

fn expr_to_string(expr: &Literal) -> Option<String> {
    let mut expr = expr.to_string();
    if !expr.starts_with(r#"""#) || !expr.ends_with(r#"""#) {
        return None;
    }
    expr.remove(0);
    expr.pop();
    Some(expr)
}

fn get_single_string_from_token_stream(token_stream: TokenStream) -> Option<String> {
    let tokens: Vec<_> = token_stream.into_iter().collect();
    match tokens.as_slice() {
        [TokenTree::Literal(expr)] => expr_to_string(expr),
        _ => None,
    }
}

/// Includes a shader file as a string with dependencies support.
///
/// By default, the file is located relative to the workspace root directory.
/// If the `relative-path` feature is enabled, then the file is located relative
/// to the current file.
///
/// # Panics
///
/// Panics if:
/// * A file specified cannot be found
/// * A circular dependency is detected
///
/// # Examples
///
/// ```ignore
/// use include_shader::include_shader;
///
/// fn main() {
///    // ...
///    let frag_shader = compile_shader(
///        &context,
///        WebGl2RenderingContext::FRAGMENT_SHADER,
///        include_shader!("src/shaders/fragment_shader.glsl"),
///    )?;
///    // ...
/// }
/// ```
///
/// ## Dependencies
///
/// Dependencies are supported within shader files using the `#include` preprocessor directive.
///
/// `rand.glsl`:
///
/// ```glsl
/// float rand(vec2 co) {
///     return fract(sin(dot(co, vec2(12.9898, 78.233))) * 43758.5453);
/// }
/// ```
///
/// `fragment_shader.glsl`:
///
/// ```glsl
/// uniform vec2 u_resolution;
///
/// #include "./src/shaders/functions/rand.glsl"
///
/// void main() {
///    vec2 st = gl_FragCoord.xy / u_resolution.xy;
///
///    gl_FragColor = vec4(vec3(rand(st)), 1.0);
/// }
/// ```
#[proc_macro]
pub fn include_shader(input: TokenStream) -> TokenStream {
    let arg = match get_single_string_from_token_stream(input) {
        Some(string) => string,
        None => panic!("Takes 1 argument and the argument must be a string literal"),
    };

    #[allow(unused_assignments, unused_mut)]
    let mut call_parent_dir_path = None;

    #[cfg(feature = "relative-path")]
    {
        let mut path = proc_macro::Span::call_site().source_file().path();
        path.pop();
        call_parent_dir_path = Some(path);
    }

    let root_path = match resolve_path(&arg, call_parent_dir_path) {
        Ok(path) => path,
        Err(e) => {
            panic!(
                r#"An error occured while trying to resolve root shader path: "{}". Error: {}"#,
                &arg,
                e
            )
        }
    };
    let mut dependency_graph = DependencyGraph::new();
    let result = process_file(&root_path, &mut dependency_graph);

    format!("{:?}", result).parse().unwrap()
}