Add functions for source and destination diff texts (#1)

Author: peter-evans

format.go

@@ -6,21 +6,60 @@ import (
 	"strings"
 )
 
+// typeSymbol returns the associated symbol of a DiffType.
+func typeSymbol(t DiffType) string {
+	switch t {
+	case Equal:
+		return " "
+	case Insert:
+		return "+"
+	case Delete:
+		return "-"
+	default:
+		panic("unknown DiffType")
+	}
+}
+
 // DiffText returns the source and destination texts (all equalities, insertions and deletions).
 func DiffText(diffs []DiffLine) string {
 	s := make([]string, len(diffs))
 	for i, l := range diffs {
 		if len(l.Text) == 0 && l.Type == Equal {
 			continue
 		}
-		prefix := " "
-		switch l.Type {
-		case Insert:
-			prefix = "+"
-		case Delete:
-			prefix = "-"
+		s[i] = fmt.Sprintf("%s%s", typeSymbol(l.Type), l.Text)
+	}
+	return strings.Join(s, "\n")
+}
+
+// DiffTextA returns the source text (all equalities and deletions).
+func DiffTextA(diffs []DiffLine) string {
+	s := []string{}
+	for _, l := range diffs {
+		if l.Type == Insert {
+			continue
+		}
+		if l.Type == Equal && len(l.Text) == 0 {
+			s = append(s, "")
+		} else {
+			s = append(s, fmt.Sprintf("%s%s", typeSymbol(l.Type), l.Text))
+		}
+	}
+	return strings.Join(s, "\n")
+}
+
+// DiffTextB returns the destination text (all equalities and insertions).
+func DiffTextB(diffs []DiffLine) string {
+	s := []string{}
+	for _, l := range diffs {
+		if l.Type == Delete {
+			continue
+		}
+		if l.Type == Equal && len(l.Text) == 0 {
+			s = append(s, "")
+		} else {
+			s = append(s, fmt.Sprintf("%s%s", typeSymbol(l.Type), l.Text))
 		}
-		s[i] = fmt.Sprintf("%s%s", prefix, l.Text)
 	}
 	return strings.Join(s, "\n")
 }

format_test.go

@@ -0,0 +1,155 @@
+// Package patience implements the Patience Diff algorithm.
+package patience
+
+import (
+	"testing"
+)
+
+func TestDiffText(t *testing.T) {
+	type args struct {
+		diffs []DiffLine
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			name: "TestDiffText",
+			args: args{
+				diffs: []DiffLine{
+					{
+						Type: Equal,
+						Text: "a",
+					},
+					{
+						Type: Insert,
+						Text: "b",
+					},
+					{
+						Type: Equal,
+						Text: "c",
+					},
+					{
+						Type: Equal,
+						Text: "",
+					},
+					{
+						Type: Delete,
+						Text: "d",
+					},
+					{
+						Type: Equal,
+						Text: "e",
+					},
+				},
+			},
+			want: " a\n+b\n c\n\n-d\n e",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := DiffText(tt.args.diffs); got != tt.want {
+				t.Errorf("DiffText() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestDiffTextA(t *testing.T) {
+	type args struct {
+		diffs []DiffLine
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			name: "TestDiffText",
+			args: args{
+				diffs: []DiffLine{
+					{
+						Type: Equal,
+						Text: "a",
+					},
+					{
+						Type: Insert,
+						Text: "b",
+					},
+					{
+						Type: Equal,
+						Text: "c",
+					},
+					{
+						Type: Equal,
+						Text: "",
+					},
+					{
+						Type: Delete,
+						Text: "d",
+					},
+					{
+						Type: Equal,
+						Text: "e",
+					},
+				},
+			},
+			want: " a\n c\n\n-d\n e",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := DiffTextA(tt.args.diffs); got != tt.want {
+				t.Errorf("DiffTextA() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestDiffTextB(t *testing.T) {
+	type args struct {
+		diffs []DiffLine
+	}
+	tests := []struct {
+		name string
+		args args
+		want string
+	}{
+		{
+			name: "TestDiffText",
+			args: args{
+				diffs: []DiffLine{
+					{
+						Type: Equal,
+						Text: "a",
+					},
+					{
+						Type: Insert,
+						Text: "b",
+					},
+					{
+						Type: Equal,
+						Text: "c",
+					},
+					{
+						Type: Equal,
+						Text: "",
+					},
+					{
+						Type: Equal,
+						Text: "e",
+					},
+				},
+			},
+			want: " a\n+b\n c\n\n e",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := DiffTextB(tt.args.diffs); got != tt.want {
+				t.Errorf("DiffTextB() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}