lang: funcs: Add datetime.format function

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

examples/lang/datetime4.mcl

@@ -0,0 +1,10 @@
+import "datetime"
+import "sys"
+import "example"
+
+$now = datetime.now()
+
+file "/tmp/mgmt-datetime" {
+	state => "exists",
+	content => template("Il est l'or Monseignor: {{ . }}\n", datetime.format($now, "15:04:05")),
+}

lang/funcs/core/datetime/format_func.go

@@ -0,0 +1,51 @@
+// Mgmt
+// Copyright (C) 2013-2019+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package coredatetime
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/purpleidea/mgmt/lang/funcs/simple"
+	"github.com/purpleidea/mgmt/lang/types"
+)
+
+func init() {
+	simple.ModuleRegister(ModuleName, "format", &types.FuncValue{
+		T: types.NewType("func(a int, b str) str"),
+		V: Format,
+	})
+}
+
+// Format returns returns a textual representation of the input time. The format
+// has to be defined like specified by the golang "time" package. The time is
+// the number of seconds since the epoch, and matches what comes from our Now
+// function.
+// Golang documentation: https://golang.org/pkg/time/#Time.Format
+func Format(input []types.Value) (types.Value, error) {
+	epochDelta := input[0].Int()
+	if epochDelta < 0 {
+		return nil, fmt.Errorf("epoch delta must be positive")
+	}
+	format := input[1].Str()
+
+	v := time.Unix(epochDelta, 0).Format(format)
+	return &types.StrValue{
+		V: v,
+	}, nil
+}

lang/funcs/core/datetime/format_func_test.go

@@ -0,0 +1,39 @@
+// Mgmt
+// Copyright (C) 2013-2019+ James Shubin and the project contributors
+// Written by James Shubin <james@shubin.ca> and the project contributors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+// +build !darwin
+
+package coredatetime
+
+import (
+	"testing"
+
+	"github.com/purpleidea/mgmt/lang/types"
+)
+
+func TestFormat(t *testing.T) {
+	inputVal := &types.IntValue{V: 1443158163}
+	inputFormat := &types.StrValue{V: "2006"}
+
+	val, err := Format([]types.Value{inputVal, inputFormat})
+	if err != nil {
+		t.Error(err)
+	}
+	if val.String() != `"2015"` {
+		t.Errorf("invalid output, expected %s, got %s", `"2015"`, val.String())
+	}
+}