add compile method

crates/ere-risczero/src/compile.rs

@@ -0,0 +1,90 @@
+mod file_utils;
+use file_utils::FileRestorer;
+
+use crate::error::CompileError;
+use serde_json::Value as JsonValue;
+use std::{
+    fs,
+    path::{Path, PathBuf},
+    process::Command,
+};
+
+/// BUILD_SCRIPT_TEMPLATE that we will use to fetch the elf-path
+/// TODO: We might be able to deterministically get the elf path
+/// TODO: But note we also probably want the image id too, so not sure
+/// TODO: we can remove this hack sometime soon.
+const BUILD_SCRIPT_TEMPLATE: &str = include_str!("../build_script_template.rs");
+
+pub(crate) fn compile_risc0_program(path: &Path) -> Result<Vec<u8>, CompileError> {
+    if !path.exists() || !path.is_dir() {
+        return Err(CompileError::InvalidMethodsPath(path.to_path_buf()));
+    }
+
+    // Inject `build.rs`
+    let build_rs_path = path.join("build.rs");
+    let _restorer = FileRestorer::new(&build_rs_path)?;
+    fs::write(&build_rs_path, BUILD_SCRIPT_TEMPLATE)
+        .map_err(|e| CompileError::io(e, "writing template build.rs"))?;
+
+    // Run `cargo build`
+    let output = Command::new("cargo")
+        .current_dir(path)
+        .arg("build")
+        .output()
+        .map_err(|e| CompileError::io(e, "spawning cargo build"))?;
+
+    if !output.status.success() {
+        return Err(CompileError::CargoBuildFailure {
+            crate_path: path.to_path_buf(),
+            status: output.status,
+            stdout: String::from_utf8_lossy(&output.stdout).into_owned(),
+            stderr: String::from_utf8_lossy(&output.stderr).into_owned(),
+        });
+    }
+
+    // Read guest info JSON
+    let info_file = path.join("ere_guest_info.json");
+    let info_text = fs::read_to_string(&info_file)
+        .map_err(|e| CompileError::io(e, "reading ere_guest_info.json"))?;
+    let info_json: JsonValue = serde_json::from_str(&info_text)
+        .map_err(|e| CompileError::serde(e, "parsing ere_guest_info.json"))?;
+
+    let elf_path = info_json["elf_path"]
+        .as_str()
+        .map(PathBuf::from)
+        .ok_or_else(|| CompileError::MissingJsonField {
+            field: "elf_path",
+            file: info_file.clone(),
+        })?;
+
+    // Return bytes
+    fs::read(&elf_path).map_err(|e| CompileError::io(e, "reading ELF file"))
+}
+
+#[cfg(test)]
+mod tests {
+    mod compile {
+
+        use crate::compile::compile_risc0_program;
+        use std::path::PathBuf;
+
+        fn get_test_risc0_methods_crate_path() -> PathBuf {
+            let workspace_dir = env!("CARGO_WORKSPACE_DIR");
+            PathBuf::from(workspace_dir)
+                .join("tests")
+                .join("risczero")
+                .join("project_structure_build")
+                .canonicalize()
+                .expect("Failed to find or canonicalize test Risc0 methods crate")
+        }
+
+        #[test]
+        fn test_compile_risc0_method_with_custom_build_rs() {
+            let test_methods_path = get_test_risc0_methods_crate_path();
+
+            let program =
+                compile_risc0_program(&test_methods_path).expect("risc0 compilation failed");
+            assert!(!program.is_empty(), "Risc0 ELF bytes should not be empty.");
+        }
+    }
+}