<template>
    <div class="server-card-container animated-fade-in">
        <div>
            <div class="server-card">
                <router-link :to="link" class="block">
                    <h2 class="text-xl flex flex-row items-center mb-2">
                        <div class="identifier-icon select-none" :class="{
                            'bg-neutral-400': status === '',
                            'bg-red-500': status === 'offline',
                            'bg-green-500': status === 'online'
                        }">
                            {{ server.name[0] }}
                        </div>
                        {{ server.name }}
                    </h2>
                </router-link>
                <div class="flex-1 py-3">
                    <p v-if="server.description.length" class="text-neutral-500 text-sm">{{ server.description }}</p>
                </div>
                <div class="flex flex-none pt-2">
                    <div class="flex-1">
                        <span class="font-semibold text-cyan-800">{{ server.node }}</span>
                    </div>
                    <div>
                        <span class="text-neutral-300">{{ server.allocation.ip }}:{{ server.allocation.port }}</span>
                    </div>
                </div>
            </div>
            <div class="footer p-4 text-sm">
                <div class="inline-block pr-2">
                    <div class="pillbox bg-neutral-700"><span class="select-none">MEM:</span> {{ memory }} Mb</div>
                </div>
                <div class="inline-block">
                    <div class="pillbox bg-neutral-700"><span class="select-none">CPU:</span> {{ cpu }} %</div>
                </div>
            </div>
        </div>
    </div>
</template>

<script lang="ts">
    import Vue from 'vue';
    import {get} from 'lodash';
    import {differenceInSeconds} from 'date-fns';
    import {AxiosError, AxiosResponse} from "axios";

    type DataStructure = {
        backgroundedAt: Date,
        documentVisible: boolean,
        resources: null | { [s: string]: any },
        cpu: number,
        memory: number,
        status: string,
        link: { name: string, params: { id: string } },
        dataGetTimeout: undefined | number,
    }

    export default Vue.extend({
        name: 'ServerBox',
        props: {
            server: {type: Object, required: true},
        },

        data: function (): DataStructure {
            return {
                backgroundedAt: new Date(),
                documentVisible: true,
                resources: null,
                cpu: 0,
                memory: 0,
                status: '',
                link: {name: 'server', params: {id: this.server.identifier}},
                dataGetTimeout: undefined,
            };
        },

        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.dataGetTimeout);
                    return;
                }

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

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

        /**
         * Clear the timer and event listeners when we destroy the component.
         */
        beforeDestroy: function () {
            window.clearInterval(this.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: AxiosResponse) => {
                        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 = parseInt(parseFloat(get(this.resources, 'memory.current', '0')).toFixed(0));
                        this.cpu = this._calculateCpu(
                            parseFloat(get(this.resources, 'cpu.current', '0')),
                            parseFloat(this.server.limits.cpu)
                        );
                    })
                    .catch((err: AxiosError) => console.warn('Error fetching server resource usage', {...err}));
            },

            /**
             * Set the CSS to use for displaying the server's current status.
             */
            getServerStatus: function () {
                if (!this.resources || !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.
             *
             * @private
             */
            _calculateCpu: function (current: number, max: number) {
                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>