1 files changed, 88 insertions, 0 deletions
diff --git a/bpkg/system-package-manager-debian.cxx b/bpkg/system-package-manager-debian.cxx
index 1e43206..21b7e04 100644
--- a/bpkg/system-package-manager-debian.cxx
+++ b/bpkg/system-package-manager-debian.cxx
@@ -25,4 +25,92 @@ namespace bpkg
   //    (e.g., openssl-devel) so probably should track the status of
   //    individual system packages. What if we "installed any version"
   //    first and then need to install specific?
+
+  auto system_package_manager_debian::
+  pkg_status (const package_name& pn,
+              const available_packages* aps,
+              bool install,
+              bool fetch) -> const vector<package_status>*
+  {
+    // First check the cache.
+    //
+    {
+      auto i (status_cache_.find (pn));
+
+      if (i != status_cache_.end ())
+        return &i->second;
+
+      if (aps == nullptr)
+        return nullptr;
+    }
+
+    // Translate our package name to the system package names.
+    //
+    strings spns (system_package_names (*aps,
+                                        os_release_.name_id,
+                                        os_release_.version_id,
+                                        os_release_.like_ids));
+
+    // @@ TODO: fallback to our package name if empty (plus -dev if lib).
+    // @@ TODO: split into packages/components
+
+    vector<package_status> r;
+
+    // First look for an already installed package.
+    //
+
+
+    // Next look for available versions if we are allowed to install.
+    //
+    // We only do this if we don't have a package already installed. This is
+    // because while Debian generally supports installing multiple versions in
+    // parallel, this is unlikely to be supported for the packages we are
+    // interested in due to the underlying limitations.
+    //
+    // Specifically, the packages that we are primarily interested in are
+    // libraries with headers and executables (tools). While Debian is able to
+    // install multiple libraries in parallel, it normally can only install a
+    // single set of headers, static libraries, pkg-config files, etc., (i.e.,
+    // the -dev package) at a time due to them being installed into the same
+    // location (e.g., /usr/include). The same holds for executables, which
+    // are installed into the same location (e.g., /usr/bin).
+    //
+    // It is possible that a certain library has made arrangements for
+    // multiple of its versions to co-exist. For example, hypothetically, our
+    // libssl package could be mapped to both libssl1.1 libssl1.1-dev and
+    // libssl3 libssl3-dev which could be installed at the same time (note
+    // that it is not the case in reality; there is only libssl-dev). However,
+    // in this case, we should probably also have two packages with separate
+    // names (e.g., libssl and libssl3) that can also co-exist. An example of
+    // this would be libQt5Core and libQt6Core. (Note that strictly speaking
+    // there could be different degrees of co-existence: for the system
+    // package manager it is sufficient for different versions not to clobber
+    // each other's files while for us we may also need the ability to use
+    // different versions in the base build).
+    //
+    // Note also that the above reasoning is quite C/C++-centric and it's
+    // possible that multiple versions of libraries (or equivalent) for other
+    // languages (e.g., Rust) can always co-exist. In this case we may need to
+    // revise this decision.
+    //
+    if (install && r.empty ())
+    {
+      if (fetch && !fetched_)
+      {
+        // @@ TODO: apt-get update
+
+        fetched_ = true;
+      }
+    }
+
+    // Cache.
+    //
+    return &status_cache_.emplace (pn, move (r)).first->second;
+  }
+
+  bool system_package_manager_debian::
+  pkg_install (const package_name&, const version&)
+  {
+    return false;
+  }
 }