1 files changed, 61 insertions, 77 deletions

diff --git a/src/project.rs b/src/project.rs
index bcbd7ad..0f56de9 100644
--- a/src/project.rs
+++ b/src/project.rs
@@ -1,99 +1,83 @@
-use glob::glob;
-use serde::{Deserialize, Serialize};
+use anyhow::{Context, Result};
+use serde::Serialize;
 use std::env;
-use std::error::Error;
 use std::path::PathBuf;
-use std::process::Command;
+use std::process::{Command, Stdio};
+
+use crate::exercise::Exercise;
 
 /// Contains the structure of resulting rust-project.json file
 /// and functions to build the data required to create the file
-#[derive(Serialize, Deserialize)]
-pub struct RustAnalyzerProject {
-    sysroot_src: String,
-    pub crates: Vec<Crate>,
+#[derive(Serialize)]
+struct RustAnalyzerProject {
+    sysroot_src: PathBuf,
+    crates: Vec<Crate>,
 }
 
-#[derive(Serialize, Deserialize)]
-pub struct Crate {
-    root_module: String,
-    edition: String,
-    deps: Vec<String>,
-    cfg: Vec<String>,
+#[derive(Serialize)]
+struct Crate {
+    root_module: PathBuf,
+    edition: &'static str,
+    // Not used, but required in the JSON file.
+    deps: Vec<()>,
+    // Only `test` is used for all crates.
+    // Therefore, an array is used instead of a `Vec`.
+    cfg: [&'static str; 1],
 }
 
 impl RustAnalyzerProject {
-    pub fn new() -> RustAnalyzerProject {
-        RustAnalyzerProject {
-            sysroot_src: String::new(),
-            crates: Vec::new(),
-        }
-    }
-
-    /// Write rust-project.json to disk
-    pub fn write_to_disk(&self) -> Result<(), std::io::Error> {
-        std::fs::write(
-            "./rust-project.json",
-            serde_json::to_vec(&self).expect("Failed to serialize to JSON"),
-        )?;
-        Ok(())
-    }
+    fn build(exercises: Vec<Exercise>) -> Result<Self> {
+        let crates = exercises
+            .into_iter()
+            .map(|exercise| Crate {
+                root_module: exercise.path,
+                edition: "2021",
+                deps: Vec::new(),
+                // This allows rust_analyzer to work inside `#[test]` blocks
+                cfg: ["test"],
+            })
+            .collect();
 
-    /// If path contains .rs extension, add a crate to `rust-project.json`
-    fn path_to_json(&mut self, path: PathBuf) -> Result<(), Box<dyn Error>> {
-        if let Some(ext) = path.extension() {
-            if ext == "rs" {
-                self.crates.push(Crate {
-                    root_module: path.display().to_string(),
-                    edition: "2021".to_string(),
-                    deps: Vec::new(),
-                    // This allows rust_analyzer to work inside #[test] blocks
-                    cfg: vec!["test".to_string()],
-                })
-            }
-        }
-
-        Ok(())
-    }
-
-    /// Parse the exercises folder for .rs files, any matches will create
-    /// a new `crate` in rust-project.json which allows rust-analyzer to
-    /// treat it like a normal binary
-    pub fn exercises_to_json(&mut self) -> Result<(), Box<dyn Error>> {
-        for path in glob("./exercises/**/*")? {
-            self.path_to_json(path?)?;
-        }
-        Ok(())
-    }
-
-    /// Use `rustc` to determine the default toolchain
-    pub fn get_sysroot_src(&mut self) -> Result<(), Box<dyn Error>> {
-        // check if RUST_SRC_PATH is set
-        if let Ok(path) = env::var("RUST_SRC_PATH") {
-            self.sysroot_src = path;
-            return Ok(());
+        if let Some(path) = env::var_os("RUST_SRC_PATH") {
+            return Ok(Self {
+                sysroot_src: PathBuf::from(path),
+                crates,
+            });
         }
 
         let toolchain = Command::new("rustc")
             .arg("--print")
             .arg("sysroot")
-            .output()?
+            .stderr(Stdio::inherit())
+            .output()
+            .context("Failed to get the sysroot from `rustc`. Do you have `rustc` installed?")?
             .stdout;
 
-        let toolchain = String::from_utf8_lossy(&toolchain);
-        let mut whitespace_iter = toolchain.split_whitespace();
-
-        let toolchain = whitespace_iter.next().unwrap_or(&toolchain);
+        let toolchain =
+            String::from_utf8(toolchain).context("The toolchain path is invalid UTF8")?;
+        let toolchain = toolchain.trim_end();
+        println!("Determined toolchain: {toolchain}\n");
 
-        println!("Determined toolchain: {}\n", &toolchain);
+        let mut sysroot_src = PathBuf::with_capacity(256);
+        sysroot_src.extend([toolchain, "lib", "rustlib", "src", "rust", "library"]);
 
-        self.sysroot_src = (std::path::Path::new(toolchain)
-            .join("lib")
-            .join("rustlib")
-            .join("src")
-            .join("rust")
-            .join("library")
-            .to_string_lossy())
-        .to_string();
-        Ok(())
+        Ok(Self {
+            sysroot_src,
+            crates,
+        })
     }
 }
+
+/// Write `rust-project.json` to disk.
+pub fn write_project_json(exercises: Vec<Exercise>) -> Result<()> {
+    let content = RustAnalyzerProject::build(exercises)?;
+
+    // Using the capacity 2^14 since the file length in bytes is higher than 2^13.
+    // The final length is not known exactly because it depends on the user's sysroot path,
+    // the current number of exercises etc.
+    let mut buf = Vec::with_capacity(1 << 14);
+    serde_json::to_writer(&mut buf, &content)?;
+    std::fs::write("rust-project.json", buf)?;
+
+    Ok(())
+}