[M7] cargoxx vendor + build --offline + path: store-path codegen

src/codegen/vendor.cpp

@@ -0,0 +1,69 @@
+module;
+
+#include <toml.hpp>
+
+module cargoxx.codegen;
+
+import std;
+import cargoxx.util;
+
+namespace cargoxx::codegen {
+
+auto parse_vendor_toml(std::string_view body) -> util::Result<VendorIndex> {
+    toml::table root;
+    try {
+        root = toml::parse(body);
+    } catch (const toml::parse_error& e) {
+        return std::unexpected(util::Error{
+            util::ErrorCode::ManifestParseError,
+            std::format("vendor.toml is not valid TOML: {}", e.description()),
+            "", std::nullopt, std::nullopt,
+        });
+    }
+
+    auto missing = [](std::string msg) {
+        return util::Error{
+            util::ErrorCode::ManifestInvalidField, std::move(msg), "",
+            std::nullopt, std::nullopt,
+        };
+    };
+
+    VendorIndex out;
+    if (const auto* tbl = root["nixpkgs"].as_table()) {
+        if (auto v = (*tbl)["store_path"].value<std::string>()) {
+            out.nixpkgs_store_path = *v;
+        } else {
+            return std::unexpected(missing("vendor.toml: [nixpkgs].store_path is required"));
+        }
+    } else {
+        return std::unexpected(missing("vendor.toml: [nixpkgs] table is required"));
+    }
+    if (const auto* tbl = root["flake_utils"].as_table()) {
+        if (auto v = (*tbl)["store_path"].value<std::string>()) {
+            out.flake_utils_store_path = *v;
+        } else {
+            return std::unexpected(missing("vendor.toml: [flake_utils].store_path is required"));
+        }
+    } else {
+        return std::unexpected(missing("vendor.toml: [flake_utils] table is required"));
+    }
+
+    if (const auto* arr = root["dep"].as_array()) {
+        for (const auto& el : *arr) {
+            const auto* tbl = el.as_table();
+            if (!tbl) {
+                return std::unexpected(missing("vendor.toml: [[dep]] entries must be tables"));
+            }
+            auto attr = (*tbl)["nixpkgs_attr"].value<std::string>();
+            auto path = (*tbl)["store_path"].value<std::string>();
+            if (!attr || !path) {
+                return std::unexpected(missing(
+                    "vendor.toml: each [[dep]] needs nixpkgs_attr and store_path"));
+            }
+            out.dep_store_paths.emplace(*attr, *path);
+        }
+    }
+    return out;
+}
+
+} // namespace cargoxx::codegen