From b4fd18ffcd66259d8987b96e214aba707534f63e Mon Sep 17 00:00:00 2001
From: Emery Hemingway <ehmry@posteo.net>
Date: Wed, 8 Jun 2022 20:19:12 -0500
Subject: [PATCH] Generate literal patterns for values

---
 src/syndicate.nim          | 13 +++++---
 src/syndicate/patterns.nim | 62 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 70 insertions(+), 5 deletions(-)

diff --git a/src/syndicate.nim b/src/syndicate.nim
index d322fb1..928d7dd 100644
--- a/src/syndicate.nim
+++ b/src/syndicate.nim
@@ -31,7 +31,7 @@ import ./syndicate/[actors, dataspaces, durings, patterns]
 from ./syndicate/relays import connectStdio, connectUnix
 
 export Assertion, Facet, Handle, Ref, Symbol, Turn, TurnAction, bootDataspace,
-    `$`, connectStdio, connectUnix, drop, facet, grab, message, publish,
+    `$`, `?`, connectStdio, connectUnix, drop, facet, grab, message, publish,
     retract, replace, run, stop, unembed
 
 proc `?`*(T: static typedesc): Pattern =
@@ -81,7 +81,11 @@ proc `?`*(T: static typedesc): Pattern =
   else:
     grab() # otherwise an abritrary capture
 
-proc `?`*(T: typedesc; bindings: sink openArray[(int, Pattern)]): Pattern =
+proc fieldCount(T: typedesc): int =
+  for _, _ in fieldPairs(default T):
+    inc result
+
+proc `?`*(T: static typedesc; bindings: sink openArray[(int, Pattern)]): Pattern =
   ## Construct a `Pattern` from type `T` that selectively captures fields.
   runnableExamples:
     import preserves
@@ -94,11 +98,10 @@ proc `?`*(T: typedesc; bindings: sink openArray[(int, Pattern)]): Pattern =
   elif T.hasPreservesRecordPragma:
     var
       label = T.recordLabel.tosymbol(Ref)
-      fields = newSeq[Pattern]()
+      fields = newSeq[Pattern](fieldCount T)
     for (i, pat) in bindings:
-      if i > fields.high: fields.setLen(succ i)
       fields[i] = pat
-    for pat in bindings.mitems:
+    for pat in fields.mitems:
       if pat.isNil: pat = drop()
     result = ?DCompound(
       orKind: DCompoundKind.rec,
diff --git a/src/syndicate/patterns.nim b/src/syndicate/patterns.nim
index 24213d6..555d6bd 100644
--- a/src/syndicate/patterns.nim
+++ b/src/syndicate/patterns.nim
@@ -55,6 +55,68 @@ proc grab*(): Pattern = ?DBind(pattern: drop())
 proc `?_`*(): Pattern = drop()
 proc `?*`*(): Pattern = grab()
 
+proc `?`*[A, B](table: TableRef[A,B]): Pattern =
+  raiseAssert "not implemented"
+
+proc `?`*[T](val: T): Pattern =
+  ## Construct a `Pattern` from value of type `T`.
+  when T is Pattern: result = val
+  elif T is Ref:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.embedded,
+        embedded: embed(val))))
+  elif T is ptr | ref:
+    if system.`==`(val, nil): result = ?(Symbol "null")
+    else: result = ?(val[])
+  elif T is bool:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.bool,
+        bool: val)))
+  elif T is float32:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.float,
+        float: val)))
+  elif T is float64:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.double,
+        double: val)))
+  elif T is SomeInteger:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.int,
+        int: AnyAtomInt val)))
+  elif T is string:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.string,
+        string: val)))
+  elif T is seq[byte]:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.bytes,
+        bytes: val)))
+  elif T is enum or T is Symbol:
+    result = Pattern(orKind: PatternKind.DLit, dlit: DLit(
+      value: AnyAtom(
+        orKind: AnyAtomKind.symbol,
+        symbol: Symbol $val)))
+  elif T.hasPreservesRecordPragma:
+    var
+      label = T.recordLabel.tosymbol(Ref)
+      fields = newSeq[Pattern]()
+    for f in fields(val):
+      fields.add ?f
+    result = ?DCompound(
+      orKind: DCompoundKind.rec,
+      rec: DCompoundRec(
+        label: label, fields: fields))
+  else:
+    {.error: "cannot derive pattern from " & $T.}
+
 type
   Value = Preserve[Ref]
   Path = seq[Value]