xapian: Wrap FieldProcessor.

* xapian.i.in (GuileXapianFieldProcessorWrapper): New class.
* xapian/xapian.scm (field-processor): New public function.

2 files changed, 40 insertions, 2 deletions

diff --git a/xapian.i.in b/xapian.i.in
index ff4ce80..bc9991c 100644
--- a/xapian.i.in
+++ b/xapian.i.in
@@ -1,5 +1,5 @@
 /* guile-xapian --- Guile bindings for Xapian
- * Copyright © 2020, 2023 Arun Isaac <arunisaac@systemreboot.net>
+ * Copyright © 2020, 2023–2024 Arun Isaac <arunisaac@systemreboot.net>
  * Copyright © 2021, 2022 Bob131 <bob@bob131.so>
  *
  * This file is part of guile-xapian.
@@ -141,3 +141,34 @@
     return new Xapian::Query (op_, slot, range_lower, range_upper);
   }
 }
+
+// Child class of Xapian::FieldProcessor that calls back to a
+// user-specified Scheme procedure to process fields.
+%{
+  class GuileXapianFieldProcessorWrapper
+    : public Xapian::FieldProcessor {
+  private:
+    SCM proc;
+  public:
+    GuileXapianFieldProcessorWrapper(SCM _proc) {
+      proc = _proc;
+    }
+    Xapian::Query operator()(const std::string &str) {
+      void *ptr;
+      int res = SWIG_ConvertPtr(scm_call_1(proc, scm_from_utf8_string(str.c_str())),
+                                &ptr,
+                                SWIGTYPE_p_Xapian__Query,
+                                0);
+      return *((Xapian::Query*)ptr);
+    }
+  };
+%}
+
+class GuileXapianFieldProcessorWrapper
+: public Xapian::FieldProcessor
+{
+ public:
+  GuileXapianFieldProcessorWrapper(SCM);
+  ~GuileXapianFieldProcessorWrapper();
+  Xapian::Query operator()(std::string const&);
+};
diff --git a/xapian/xapian.scm b/xapian/xapian.scm
index 80b4b9b..8b8b952 100644
--- a/xapian/xapian.scm
+++ b/xapian/xapian.scm
@@ -1,5 +1,5 @@
 ;;; guile-xapian --- Guile bindings for Xapian
-;;; Copyright © 2020, 2022 Arun Isaac <arunisaac@systemreboot.net>
+;;; Copyright © 2020, 2022, 2024 Arun Isaac <arunisaac@systemreboot.net>
 ;;; Copyright © 2021 Bob131 <bob@bob131.so>
 ;;;
 ;;; This file is part of guile-xapian.
@@ -53,6 +53,7 @@
             query-and
             query-or
             query-filter
+            field-processor
             enquire
             enquire-mset
             mset-item-docid
@@ -234,6 +235,12 @@ In a non-weighted context, @code{query-filter} and @code{query-and}
 are equivalent."
   (apply query-combine (Query-OP-FILTER) (Query-MatchAll) queries))
 
+(define (field-processor proc)
+  "Return a @code{FieldProcessor} object that calls
+@var{proc} to process its field. @var{proc} is a procedure that, given
+a string, must return a @code{Query} object."
+  (new-GuileXapianFieldProcessorWrapper proc))
+
 (define (get-flag flag-thunk value)
   (if value (flag-thunk) 0))