package slice

import "reflect"
import "html/template"
import "git.tebibyte.media/sashakoshka/step"

const hiddenPrefix = "."

var _ step.FuncProvider = new(Provider)

// Provider provides slice functions.
type Provider struct {
	
}

// Package fulfills the step.Provider interface.
func (this *Provider) Package () string {
	return "slice"
}

// FuncMap fulfills the step.FuncProvider interface.
func (this *Provider) FuncMap () template.FuncMap {
	return template.FuncMap {
		"list":   funcList,
		"append": funcAppend,
	}
}

func funcList (items ...reflect.Value) (reflect.Value, error) {
	if len(items) == 0 { return reflect.Value { }, nil }
	ty := items[0].Type()
	list := reflect.MakeSlice(ty, len(items), len(items))
	for index, item := range items {
		if item.Type().AssignableTo(ty) {
			return reflect.Value { }, step.ErrTypeMismatch
		}
		dest := list.Index(index)
		dest.Set(item)
	}
	return list, nil
}

func funcAppend (slice reflect.Value, items ...reflect.Value) (reflect.Value, error) {
	if slice.Type().Kind() != reflect.Slice {
		return reflect.Value { }, step.ErrTypeMismatch
	}
	if len(items) == 0 { return reflect.Value { }, nil }
	ty := slice.Type().Elem()
	end := slice.Len() + len(items)
	list := reflect.MakeSlice(ty, end, end)
	boundary := reflect.Copy(list, slice)
	reflect.Copy(list.Slice(boundary, end), reflect.ValueOf(items))
	return list, nil
}