Restore "table" --format from V1

* --format "table {{.field..." will print fields out in a table with
  headings.  Table keyword is removed, spaces between fields are
  converted to tabs
* Update parse.MatchesJSONFormat()'s regex to be more inclusive
* Add report.Headers(), obtain all the field names to be used as
  column headers, a map of field name to column headers may be provided
  to override the field names
* Update several commands to use new functions

Signed-off-by: Jhon Honce <jhonce@redhat.com>

2 files changed, 103 insertions, 0 deletions

diff --git a/cmd/podman/report/format.go b/cmd/podman/report/format.go
new file mode 100644
index 000000000..32d92bec5
--- /dev/null
+++ b/cmd/podman/report/format.go
@@ -0,0 +1,68 @@
+package report
+
+import (
+	"reflect"
+	"strings"
+)
+
+// tableReplacer will remove 'table ' prefix and clean up tabs
+var tableReplacer = strings.NewReplacer(
+	"table ", "",
+	`\t`, "\t",
+	`\n`, "\n",
+	" ", "\t",
+)
+
+// escapedReplacer will clean up escaped characters from CLI
+var escapedReplacer = strings.NewReplacer(
+	`\t`, "\t",
+	`\n`, "\n",
+)
+
+// NormalizeFormat reads given go template format provided by CLI and munges it into what we need
+func NormalizeFormat(format string) string {
+	f := format
+	// two replacers used so we only remove the prefix keyword `table`
+	if strings.HasPrefix(f, "table ") {
+		f = tableReplacer.Replace(f)
+	} else {
+		f = escapedReplacer.Replace(format)
+	}
+
+	if !strings.HasSuffix(f, "\n") {
+		f += "\n"
+	}
+
+	return f
+}
+
+// Headers queries the interface for field names
+func Headers(object interface{}, overrides map[string]string) []map[string]string {
+	value := reflect.ValueOf(object)
+	if value.Kind() == reflect.Ptr {
+		value = value.Elem()
+	}
+
+	// Column header will be field name upper-cased.
+	headers := make(map[string]string, value.NumField())
+	for i := 0; i < value.Type().NumField(); i++ {
+		field := value.Type().Field(i)
+		// Recurse to find field names from promoted structs
+		if field.Type.Kind() == reflect.Struct && field.Anonymous {
+			h := Headers(reflect.New(field.Type).Interface(), nil)
+			for k, v := range h[0] {
+				headers[k] = v
+			}
+			continue
+		}
+		headers[field.Name] = strings.ToUpper(field.Name)
+	}
+
+	if len(overrides) > 0 {
+		// Override column header as provided
+		for k, v := range overrides {
+			headers[k] = strings.ToUpper(v)
+		}
+	}
+	return []map[string]string{headers}
+}
diff --git a/cmd/podman/report/format_test.go b/cmd/podman/report/format_test.go
new file mode 100644
index 000000000..7dd62e899
--- /dev/null
+++ b/cmd/podman/report/format_test.go
@@ -0,0 +1,35 @@
+package report
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestNormalizeFormat(t *testing.T) {
+	cases := []struct {
+		format   string
+		expected string
+	}{
+		{"table {{.ID}}", "{{.ID}}\n"},
+		{"table {{.ID}} {{.C}}", "{{.ID}}\t{{.C}}\n"},
+		{"{{.ID}}", "{{.ID}}\n"},
+		{"{{.ID}}\n", "{{.ID}}\n"},
+		{"{{.ID}} {{.C}}", "{{.ID}} {{.C}}\n"},
+		{"\t{{.ID}}", "\t{{.ID}}\n"},
+		{`\t` + "{{.ID}}", "\t{{.ID}}\n"},
+		{"table {{.ID}}\t{{.C}}", "{{.ID}}\t{{.C}}\n"},
+		{"{{.ID}} table {{.C}}", "{{.ID}} table {{.C}}\n"},
+	}
+	for _, tc := range cases {
+		tc := tc
+
+		label := strings.ReplaceAll(tc.format, " ", "<sp>")
+		t.Run("NormalizeFormat/"+label, func(t *testing.T) {
+			t.Parallel()
+			actual := NormalizeFormat(tc.format)
+			if actual != tc.expected {
+				t.Errorf("Expected %q, actual %q", tc.expected, actual)
+			}
+		})
+	}
+}