package html

import (
	"encoding/json"
	"errors"
	"reflect"
	"unicode/utf8"
)

func dump(args ...interface{}) (string, error) {
	out := ""
	for _, a := range args {
		str, err := json.MarshalIndent(a, "", "  ")
		if err != nil {
			return "", err
		}
		out += string(str) + "\n"
	}
	return out, nil
}

func increment(value int) int {
	return value + 1
}

func ellipsis(str string, max int) string {
	if utf8.RuneCountInString(str) > max {
		return string([]rune(str)[0:(max-3)]) + "..."
	}
	return str
}

func customMap(values ...interface{}) (map[string]interface{}, error) {
	if len(values)%2 != 0 {
		return nil, errors.New("invalid custoMmap call")
	}
	customMap := make(map[string]interface{}, len(values)/2)
	for i := 0; i < len(values); i += 2 {
		key, ok := values[i].(string)
		if !ok {
			return nil, errors.New("map keys must be strings")
		}
		customMap[key] = values[i+1]
	}
	return customMap, nil
}

func defaultVal(src interface{}, defaultValue interface{}) interface{} {
	switch typ := src.(type) {
	case string:
		if typ == "" {
			return defaultValue
		}
	default:
		if src == nil {
			return defaultValue
		}
	}
	return src
}

func has(v interface{}, name string) bool {
	rv := reflect.ValueOf(v)
	if rv.Kind() == reflect.Ptr {
		rv = rv.Elem()
	}
	if rv.Kind() != reflect.Struct {
		return false
	}
	return rv.FieldByName(name).IsValid()
}