<template>
    <div class="server-box animate fadein">
        <router-link :to="{ name: 'server', params: { id: server.identifier }}" class="content">
            <div class="float-right">
                <div class="indicator" :class="status"></div>
            </div>
            <div class="mb-4">
                <div class="text-black font-bold text-xl">
                    {{ server.name }}
                </div>
            </div>
            <div class="mb-0 flex">
                <div class="usage">
                    <div class="indicator-title">{{ $t('dashboard.index.cpu_title') }}</div>
                </div>
                <div class="usage">
                    <div class="indicator-title">{{ $t('dashboard.index.memory_title') }}</div>
                </div>
            </div>
            <div class="mb-4 flex text-center">
                <div class="inline-block border border-grey-lighter border-l-0 p-4 flex-1">
                    <span class="font-bold text-xl">{{ cpu > 0 ? cpu : '&mdash;' }}</span>
                    <span class="font-light text-sm">%</span>
                </div>
                <div class="inline-block border border-grey-lighter border-l-0 border-r-0 p-4 flex-1">
                    <span class="font-bold text-xl">{{ memory > 0 ? memory : '&mdash;' }}</span>
                    <span class="font-light text-sm">MB</span>
                </div>
            </div>
            <div class="flex items-center">
                <div class="text-sm">
                    <p class="text-grey">{{ server.node }}</p>
                    <p class="text-grey-dark">{{ server.allocation.ip }}:{{ server.allocation.port }}</p>
                </div>
            </div>
        </router-link>
    </div>
</template>

<script>
    import get from 'lodash/get';
    import differenceInSeconds from 'date-fns/difference_in_seconds';

    export default {
        name: 'server-box',
        props: {
            server: { type: Object, required: true },
        },

        dataGetTimeout: null,

        data: function () {
            return {
                backgroundedAt: new Date(),
                documentVisible: true,
                resources: undefined,
                cpu: 0,
                memory: 0,
                status: '',
            };
        },

        watch: {
            /**
             * Watch the documentVisible item and perform actions when it is changed. If it becomes
             * true, we want to check how long ago the last poll was, if it was more than 30 seconds
             * we want to immediately trigger the resourceUse api call, otherwise we just want to restart
             * the time.
             *
             * If it is now false, we want to clear the timer that checks resource use, since we know
             * we won't be doing anything with them anyways. Might as well avoid extraneous resource
             * usage by the browser.
             */
            documentVisible: function (value) {
                if (!value) {
                    window.clearTimeout(this.$options.dataGetTimeout);
                    return;
                }

                if (differenceInSeconds(new Date(), this.backgroundedAt) >= 30) {
                    this.getResourceUse();
                }

                this.$options.dataGetTimeout = window.setInterval(() => {
                    this.getResourceUse();
                }, 10000);
            },
        },

        /**
         * Grab the initial resource usage for this specific server instance and add a listener
         * to monitor when this window is no longer visible. We don't want to needlessly poll the
         * API when we aren't looking at the page.
         */
        created: function () {
            this.getResourceUse();
            document.addEventListener('visibilitychange', this._visibilityChange.bind(this));
        },

        /**
         * Poll the API for changes every 10 seconds when the component is mounted.
         */
        mounted: function () {
            this.$options.dataGetTimeout = window.setInterval(() => {
                this.getResourceUse();
            }, 10000);
        },

        /**
         * Clear the timer and event listeners when we destroy the component.
         */
        beforeDestroy: function () {
            window.clearInterval(this.$options.dataGetTimeout);
            document.removeEventListener('visibilitychange', this._visibilityChange.bind(this), false);
        },

        methods: {
            /**
             * Query the resource API to determine what this server's state and resource usage is.
             */
            getResourceUse: function () {
                window.axios.get(this.route('api.client.servers.resources', { server: this.server.identifier }))
                    .then(response => {
                        if (!(response.data instanceof Object)) {
                            throw new Error('Received an invalid response object back from status endpoint.');
                        }


                        this.resources = response.data.attributes;
                        this.status = this.getServerStatus();

                        this.memory = Number(get(this.resources, 'memory.current', 0)).toFixed(0);
                        this.cpu = this._calculateCpu(
                            Number(get(this.resources, 'cpu.current', 0)),
                            Number(this.server.limits.cpu)
                        );
                    })
                    .catch(err => {
                        console.error({ err });
                    });
            },

            /**
             * Set the CSS to use for displaying the server's current status.
             */
            getServerStatus: function () {
                if (!(this.resources instanceof Object)) {
                    return '';
                }

                if (!this.resources.installed || this.resources.suspended) {
                    return '';
                }

                switch (this.resources.state) {
                    case 'off':
                        return 'offline';
                    case 'on':
                    case 'starting':
                    case 'stopping':
                        return 'online';
                    default:
                        return '';
                }
            },

            /**
             * Calculate the CPU usage for a given server relative to their set maximum.
             *
             * @param {Number} current
             * @param {Number} max
             * @return {Number}
             * @private
             */
            _calculateCpu: function (current, max) {
                if (max === 0) {
                    return parseFloat(current.toFixed(1));
                }

                return parseFloat((current / max * 100).toFixed(1));
            },

            /**
             * Handle document visibility changes.
             *
             * @private
             */
            _visibilityChange: function () {
                this.documentVisible = document.visibilityState === 'visible';

                if (!this.documentVisible) {
                    this.backgroundedAt = new Date();
                }
            },
        }
    };
</script>