add build_script template

crates/ere-risczero/build_script_template.rs

@@ -0,0 +1,62 @@
+// This is ere-risczero/build_script_template.rs
+// This script will be temporarily copied as build.rs into the target methods crate.
+
+use std::env;
+use std::fs::File;
+use std::io::Write;
+use std::path::Path;
+
+#[derive(Debug)]
+struct GuestMethodInfo {
+    name: String,
+    elf_path: String, // Path to the ELF in OUT_DIR, as determined by risc0_build
+    image_id_hex: String,
+}
+
+fn main() {
+    let guest_entries = risc0_build::embed_methods();
+
+    if guest_entries.is_empty() {
+        eprintln!("ere Risc0 Template Build: risc0_build::embed_methods() found no guest methods.");
+        return;
+    }
+
+    let entry = &guest_entries[0]; // For simplicity, take the first guest
+    let info = GuestMethodInfo {
+        name: entry.name.to_string(),
+        elf_path: entry.path.to_string(), // This path is to the ELF in OUT_DIR
+        image_id_hex: entry
+            .image_id
+            .as_bytes()
+            .iter()
+            .map(|b| format!("{:02x}", b))
+            .collect(),
+    };
+
+    // Output the info to a known file directly in the methods crate directory.
+    let manifest_dir =
+        env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR not set for template build.rs");
+    let info_file_path = Path::new(&manifest_dir).join("ere_guest_info.json");
+
+    let json_output = format!(
+        r#"{{
+    "name": "{}",
+    "elf_path": "{}",
+    "image_id_hex": "{}"
+}}"#,
+        info.name.replace('\\', "\\\\").replace('"', "\\\""),
+        info.elf_path.replace('\\', "\\\\").replace('"', "\\\""),
+        info.image_id_hex
+    );
+
+    let mut file = File::create(&info_file_path)
+        .expect("Template build.rs: Failed to create ere_guest_info.json in manifest dir");
+    file.write_all(json_output.as_bytes())
+        .expect("Template build.rs: Failed to write to ere_guest_info.json in manifest dir");
+
+    println!("cargo:rerun-if-changed=build.rs");
+    eprintln!(
+        "ere Risc0 Template Build: Guest info written to {:?}",
+        info_file_path
+    );
+}