// Mgmt
// Copyright (C) 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 <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this program, or any covered work, by linking or combining it
// with embedded mcl code and modules (and that the embedded mcl code and
// modules which link with this program, contain a copy of their source code in
// the authoritative form) containing parts covered by the terms of any other
// license, the licensors of this program grant you additional permission to
// convey the resulting work. Furthermore, the licensors of this program grant
// the original author, James Shubin, additional permission to update this
// additional permission if he deems it necessary to achieve the goals of this
// additional permission.

package corestrings

import (
	"context"
	"strings"

	"github.com/purpleidea/mgmt/lang/funcs/simple"
	"github.com/purpleidea/mgmt/lang/types"
)

func init() {
	simple.ModuleRegister(ModuleName, "join_nonempty", &simple.Scaffold{
		T: types.NewType("func(s []str, sep str) str"),
		F: JoinNonempty,
	})
}

// JoinNonempty behaves exactly like the regular string join, except it filters
// out empty elements first. Since this behaviour is commonly useful when
// writing scripts, we include it as a built-in primitive, since it is also
// cheaper than running the graph changing, filter function.
// TODO: compiler optimization: find patterns where someone used the filter
// function as previously described, and replace it with this implementation.
func JoinNonempty(ctx context.Context, input []types.Value) (types.Value, error) {
	return &types.StrValue{
		V: joinNonempty(types.ValueToListStr(input[0]), input[1].Str()),
	}, nil
}

// joinNonempty is the actual implementation.
func joinNonempty(elems []string, sep string) string {
	l := []string{}
	for _, x := range elems {
		if x == "" {
			continue
		}
		l = append(l, x)
	}

	return strings.Join(l, sep)
}