<template>
    <div v-if="shouldShowPagination">
        <div class="col-lg-12">
            <nav aria-label="Page navigation">
                <ul class="pagination justify-content-center">
                    <li :class="(pagination.currentPage === 1) ? 'page-item disabled' : 'page-item'">
                        <a href="javascript:void(0)"
                           class="page-link"
                           @click="pageClicked( pagination.currentPage - 1 )">
                            Предыдущая
                        </a>
                    </li>
                    <li class="page-item"
                        v-for="page in this.pageLinks()"
                        :key="page"
                        :class="(isActive(page) || page === '...') ? 'page-item disabled' : 'page-item'">
                        <a class="page-link"
                           @click="pageClicked(page)"
                           href="javascript:void(0)">
                            {{ page }}
                        </a>
                    </li>
                    <li :class="(pagination.currentPage === this.pagination.totalPages) ? 'page-item disabled': 'page-item'">
                        <a href="javascript:void(0)"
                           class="page-link"
                           @click="pageClicked( pagination.currentPage + 1 )">
                            Следующая
                        </a>
                    </li>
                </ul>
            </nav>
        </div>
    </div>
</template>
<script>
    export default {
        name: 'Pagination',
        props: ['pagination'],
        methods: {
            pageLinks: function () {
                if (this.pagination.totalPages === undefined) {
                    return [];
                }

                const arr = [];
                let preDots = false;
                let postDots = false;

                for (let i = 1; i <= this.pagination.totalPages; i++) {
                    if (this.pagination.totalPages <= 10) {
                        arr.push(i);
                    } else {
                        if (i === 1) {
                            arr.push(i);
                        } else if (i === this.pagination.totalPages) {
                            arr.push(i);
                        } else if (
                            (i > this.pagination.currentPage - 4 && i < this.pagination.currentPage + 4) ||
                            (i < 4 && this.pagination.currentPage < 4) ||
                            (i > this.pagination.totalPages - 4 && this.pagination.currentPage > this.pagination.totalPages - 4)) {
                            arr.push(i);
                        } else if (i < this.pagination.currentPage && !preDots) {
                            arr.push('...');
                            preDots = true;
                        } else if (i > this.pagination.currentPage && !postDots) {
                            arr.push('...');
                            postDots = true;
                        }
                    }
                }

                return arr;
            },

            shouldShowPagination: function () {
                if (this.pagination.totalPages === undefined) {
                    return false;
                }

                if (this.pagination.count === 0) {
                    return false;
                }

                return this.pagination.totalPages > 1;
            },

            isActive: function (page) {
                const currentPage = this.pagination.currentPage || 1;

                return currentPage === page;
            },

            pageClicked: function (page) {
                if (page === '...' ||
                    page === this.pagination.currentPage ||
                    page > this.pagination.totalPages ||
                    page < 1) {
                    return;
                }

                this.$emit('pageChange', page);
                this.$scrollTo('#top_line', 450);
            },
        },
    };
</script>