mruby: return api mpv queries as either monads

5 files changed, 63 insertions, 49 deletions

diff --git a/player/mruby.c b/player/mruby.c
index f82fa54aaa..864043e7d0 100644
--- a/player/mruby.c
+++ b/player/mruby.c
@@ -34,8 +34,8 @@
 #include "mpv_talloc.h"
 
 static const char * const mruby_scripts[][2] = {
-    {"mpv/reply.mrb",
-#   include "player/mruby/reply.inc"
+    {"mpv/either.mrb",
+#   include "player/mruby/either.inc"
     },
     {"mpv/logging.mrb",
 #   include "player/mruby/logging.inc"
@@ -74,11 +74,11 @@ static int get_loglevel(char *level)
 
 static mrb_value api_return(mrb_state *mrb, int err, mrb_value value)
 {
-    const char* status = mpv_error_string(err);
+    bool ok = err == MPV_ERROR_SUCCESS;
     struct RClass *M = mrb_module_get(mrb, "M");
-    struct RClass *c = mrb_class_get_under(mrb, M, "Reply");
-    mrb_value init_args[2] = { value, mrb_str_new_cstr(mrb, status) };
-    return mrb_obj_new(mrb, c, MP_ARRAY_SIZE(init_args), init_args);
+    struct RClass *c = mrb_class_get_under(mrb, M, ok ? "Right" : "Left");
+    mrb_value val = ok ? value : mrb_str_new_cstr(mrb, mpv_error_string(err));
+    return mrb_obj_new(mrb, c, 1, &val);
 }
 
 #define api_return_bool(mrb, err) api_return(mrb, err, mrb_bool_value(err >= 0))
diff --git a/player/mruby/either.mrb b/player/mruby/either.mrb
new file mode 100644
index 0000000000..becec6c961
--- /dev/null
+++ b/player/mruby/either.mrb
@@ -0,0 +1,49 @@
+module M
+  class ReplyError < StandardError; end
+
+  class Either
+    def initialize(value)
+      @value = value
+    end
+
+    def to_s
+      "#<#{self.class.name} value=#{@value}>"
+    end
+  end
+
+  class Left < Either
+    def map(&block)
+      self
+    end
+
+    def get_or_else(value)
+      value
+    end
+
+    def get!
+      raise ReplyError, @value
+    end
+
+    def success?
+      false
+    end
+  end
+
+  class Right < Either
+    def map(&block)
+      Right.new(block.call(@value))
+    end
+
+    def get_or_else(_value)
+      @value
+    end
+
+    def get!
+      @value
+    end
+
+    def success?
+      true
+    end
+  end
+end
diff --git a/player/mruby/reply.mrb b/player/mruby/reply.mrb
deleted file mode 100644
index 4ae65dbd3f..0000000000
--- a/player/mruby/reply.mrb
+++ /dev/null
@@ -1,37 +0,0 @@
-module M
-  class ReplyError < StandardError; end
-  class Reply < Struct.new(:val, :status)
-    %w(b f i s).map{|type| "to_#{type}"}.map(&:intern).each do |method|
-      define_method(method) { unbox!.send(method) }
-    end
-
-    def unbox(default=nil, &block)
-      unbox!(&block)
-    rescue ReplyError
-      default
-    end
-
-    def unbox!(&block)
-      if success?
-        block_given? ? yield(val) : val
-      else
-        raise ReplyError, status
-      end
-    end
-
-    private :val
-
-    private
-    def success?
-      status == "success"
-    end
-
-    def method_missing(method, *args, &block)
-      if success? and val.respond_to?(method)
-        val.send(method, *args, &block)
-      else
-        super
-      end
-    end
-  end
-end
diff --git a/player/mruby/test.mrb b/player/mruby/test.mrb
index 4fb68d76ea..2a4f8687b1 100644
--- a/player/mruby/test.mrb
+++ b/player/mruby/test.mrb
@@ -5,8 +5,8 @@ end
 
 def with_unbox(a, &block)
   case [a.class]
-  when [M::Reply] then
-    a.unbox(&block)
+  when [M::Left], [M::Right] then
+    a.map(&block).get_or_else(false)
   else
     yield(a)
   end
@@ -22,7 +22,8 @@ def assert_class(a, klass)
 end
 
 def assert_include(a, b)
-  raise "Expected:\n#{a}\nto include\n#{b}\n" unless a.include?(b)
+  raise "Expected:\n#{a}\nto include\n#{b}\n" \
+    unless with_unbox(a) { |v| v.include?(b) }
 end
 
 def ok(s)
@@ -55,7 +56,8 @@ def run
 end
 
 assert ".property_list returns an array" do
-  assert_class(M.get_property('property-list').val, Array)
+  assert_class(M.get_property('property-list').get!, Array)
+  assert_class(M.get_property('property-list'), Array)
 end
 
 assert ".property_list contains options" do
@@ -67,7 +69,7 @@ assert ".get_property returns proper values" do
   assert_class(M.get_property("volume"),    Float)
   assert_class(M.get_property("osd-width"), Fixnum)
   assert_class(M.get_property("vf"),        Array)
-  assert_include([true, false], M.get_property("mute").unbox!)
+  assert_equal(M.get_property("mute"),      false)
 end
 
 assert ".set_property works on complex types" do
diff --git a/wscript_build.py b/wscript_build.py
index 332bc9e596..8dc72aee96 100644
--- a/wscript_build.py
+++ b/wscript_build.py
@@ -109,7 +109,7 @@ def build(ctx):
             target = os.path.splitext(fn)[0] + ".inc",
         )
 
-    mruby_files = ['events.mrb', 'logging.mrb', 'reply.mrb']
+    mruby_files = ['events.mrb', 'logging.mrb', 'either.mrb']
     for fn in mruby_files:
         fn = "player/mruby/" + fn
         ctx(