From b434fe4e14f6dcc8d1d7433a29351b8e8ea77d37 Mon Sep 17 00:00:00 2001
From: Charlie Stanton <charlie@shtanton.xyz>
Date: Thu, 2 May 2024 21:45:45 +0100
Subject: Add , subex syntax to make FullMerge commands easier

---
 main/main_test.go | 15 +++++++++++----
 subex/filter.go   | 20 ++++++++++++++++++++
 subex/parse.go    | 11 +++++++++++
 subex/subexast.go | 12 ++++++++++++
 4 files changed, 54 insertions(+), 4 deletions(-)

diff --git a/main/main_test.go b/main/main_test.go
index 3d10c48..076693d 100644
--- a/main/main_test.go
+++ b/main/main_test.go
@@ -6,7 +6,8 @@ import (
 )
 
 const miscInput string = `{"something":{"nested":"Here is my test value"},"array":["Hello","world","these","are","values"],"people":[{"first_name":"Charlie","last_name":"Johnson","age":22},{"first_name":"Tom","last_name":"Johnson","age":18},{"first_name":"Charlie","last_name":"Chaplin","age":122},{"first_name":"John","last_name":"Johnson","age":48}]}`
-const mixedArray string = `{"array":["first",{"name":"second"},"third"]}`
+const mixedArray string = `{"array":["first",null,3,{"name":"second"},"third"]}`
+const mixedArray2 string = `{"array":["first",null,3,"second",{"name":"third"}]}`
 
 func TestSpecificCases(t *testing.T) {
 	type test struct {
@@ -116,7 +117,7 @@ func TestSpecificCases(t *testing.T) {
 		},
 		{
 			name: "Drop last element of array",
-			program: `M/#( "people" @( . #()# )@ )#/{ Ed }`,
+			program: `M/#( "people" @( . , )@ )#/{ Ed }`,
 			input: miscInput,
 			expected: `{"something":{"nested":"Here is my test value"},"array":["Hello","world","these","are","values"],"people":[{"first_name":"Charlie","last_name":"Johnson","age":22},{"first_name":"Tom","last_name":"Johnson","age":18},{"first_name":"Charlie","last_name":"Chaplin","age":122}]}`,
 		},
@@ -128,9 +129,15 @@ func TestSpecificCases(t *testing.T) {
 		},
 		{
 			name: "Drop last element of mixed array",
-			program: `M/#( "array" @( . (~[.]~|@()@|#()#) )@ )#/{ Ed }`,
+			program: `M/#( "array" @( . , )@ )#/{ Ed }`,
 			input: mixedArray,
-			expected: `{"array":["first",{"name":"second"}]}`,
+			expected: `{"array":["first",null,3,{"name":"second"}]}`,
+		},
+		{
+			name: "Drop last element of mixed array 2",
+			program: `M/#( "array" @( . , )@ )#/{ Ed }`,
+			input: mixedArray2,
+			expected: `{"array":["first",null,3,"second"]}`,
 		},
 		{
 			name: "Prepend to array",
diff --git a/subex/filter.go b/subex/filter.go
index ae4b8ab..309d6c7 100644
--- a/subex/filter.go
+++ b/subex/filter.go
@@ -27,6 +27,26 @@ func (_ anyBoolFilter) valueFilter(value walk.Value) bool {
 	return isBool
 }
 
+type simpleValueFilter struct {}
+func (_ simpleValueFilter) valueFilter(value walk.Value) bool {
+	switch value := value.(type) {
+	case walk.NullValue:
+		return true
+	case walk.BoolValue:
+		return true
+	case walk.NumberValue:
+		return true
+	case walk.StringValue:
+		return true
+	case walk.ArrayValue:
+		return len(value) == 0
+	case walk.MapValue:
+		return len(value) == 0
+	default:
+		panic("Invalid value type")
+	}
+}
+
 type anyValueFilter struct {}
 func (_ anyValueFilter) valueFilter(value walk.Value) bool {
 	return true
diff --git a/subex/parse.go b/subex/parse.go
index 9a7a75c..e91008a 100644
--- a/subex/parse.go
+++ b/subex/parse.go
@@ -520,6 +520,17 @@ func parseSubex(l RuneReader, minPower int, inType Type) (lhs SubexAST, outType
 			} else {
 				lhs = SubexASTCopyAnyValue{}
 			}
+		case ',':
+			switch inType {
+			case ValueType:
+				outType = inType
+				lhs = SubexASTCopyAnySimpleValue{}
+			case RuneType:
+				outType = inType
+				lhs = SubexASTCopyRune{','}
+			default:
+				panic("Invalid inType")
+			}
 		case '?':
 			outType = inType
 			lhs = SubexASTCopyBool{}
diff --git a/subex/subexast.go b/subex/subexast.go
index d08ddac..655a783 100644
--- a/subex/subexast.go
+++ b/subex/subexast.go
@@ -238,6 +238,18 @@ func (ast SubexASTCopyNumber) String() string {
 	return "%"
 }
 
+// Read in a null, bool, number, string or empty array or map and output it unchanged
+type SubexASTCopyAnySimpleValue struct {}
+func (ast SubexASTCopyAnySimpleValue) compileWith(next SubexState, slotMap *SlotMap, inType Type, outType Type) SubexState {
+	if inType != ValueType || outType != ValueType {
+		panic("Invalid types for SubexASTCopyAnySimpleValue")
+	}
+	return &SubexCopyState {
+		next: next,
+		filter: simpleValueFilter{},
+	}
+}
+
 // Read in any single Atom and output it unchanged
 type SubexASTCopyAnyValue struct {}
 func (ast SubexASTCopyAnyValue) compileWith(next SubexState, slotMap *SlotMap, inType Type, outType Type) SubexState {
-- 
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