From cd493d4152d7b9a2dc7a4383bb24e4650afb4ea4 Mon Sep 17 00:00:00 2001
From: s-ol <s-ol@users.noreply.github.com>
Date: Tue, 1 Sep 2020 15:24:37 +0200
Subject: support :vis() on builtins

---
 alv/base/builtin.moon | 11 +++++++++++
 alv/builtins.moon     |  7 ++++++-
 alv/copilot/udp.moon  |  2 +-
 alv/invoke.moon       |  7 +++++++
 4 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/alv/base/builtin.moon b/alv/base/builtin.moon
index 54f7433..558a65a 100644
--- a/alv/base/builtin.moon
+++ b/alv/base/builtin.moon
@@ -53,6 +53,17 @@ class Builtin
   -- @tparam ?Builtin prev the previous Builtin instance
   setup: (prev) =>
 
+  --- collect visualisation data (optional).
+  --
+  -- This may return any simple Lua value, including Lua tables, as long as it
+  -- has no metatables, multiple references/loops, userdata etc.
+  --
+  -- This value is exposed to alv editors in order to render realtime
+  -- visualisations overlaid onto the program text.
+  --
+  -- @treturn table vis
+  vis: => {}
+
   --- the `Cell` this Builtin was created for.
   -- @tfield Cell cell
 
diff --git a/alv/builtins.moon b/alv/builtins.moon
index 8a08705..d6a52b9 100644
--- a/alv/builtins.moon
+++ b/alv/builtins.moon
@@ -279,6 +279,7 @@ to `then-expr`, otherwise it is equivalent to `else-xpr` if given, or nil otherw
         msg = "'if'-expression needs to be constant, did you mean 'switch'?"
         error Error 'argument', msg
       xif = xif.result\unwrap!
+      @state = xif
 
       super if xif
         xthen\eval scope
@@ -287,6 +288,8 @@ to `then-expr`, otherwise it is equivalent to `else-xpr` if given, or nil otherw
       else
         RTNode!
 
+    vis: => step: if @state then 0 else 1
+
 when_ = Constant.meta
   meta:
     name: 'when'
@@ -366,7 +369,9 @@ switch_ = Constant.meta
 
       @out\set if v = values[@state + 1] then v!
 
-    vis: => step: @state
+    vis: =>
+      with Op.vis @
+        .step = @state
 
 trace_ = Constant.meta
   meta:
diff --git a/alv/copilot/udp.moon b/alv/copilot/udp.moon
index 0640189..f5deb50 100644
--- a/alv/copilot/udp.moon
+++ b/alv/copilot/udp.moon
@@ -49,7 +49,7 @@ class UDPServer
         if builtin and builtin.__class.__name ~= 'DummyReg'
           res.head_meta = builtin.head.meta
           res.result = encode_res builtin.node.result
-          res.vis = if builtin.op then builtin.op\vis!
+          res.vis = builtin\vis!
           res.kind = switch builtin.__class
             when op_invoke then 'op'
             when fn_invoke then 'fn'
diff --git a/alv/invoke.moon b/alv/invoke.moon
index 6962f4d..e40cbc4 100644
--- a/alv/invoke.moon
+++ b/alv/invoke.moon
@@ -77,6 +77,13 @@ class op_invoke extends Builtin
 
     super RTNode :children, result: @op.out, op: @op
 
+  --- `Builtin:vis` implementation.
+  --
+  -- calls `op`:@{Op:vis|vis}.
+  --
+  -- @treturn table vis
+  vis: => if @op then @op\vis!
+
   --- The `Op` instance.
   --
   -- @tfield Op op
-- 
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