perf(alert): convert template to render function (#1308)

* [alert] Convert template to render function

* Delete alert.vue

* remove unneeded warn import

src/components/alert/alert.js

@@ -1,3 +1,117 @@
-import bAlert from './alert.vue';
+import bBtnClose from '../button/button-close';
 
-export default bAlert;
+export default {
+    components: {bBtnClose},
+    render(h) {
+        if (!this.localShow) {
+            // If not showing, render placeholder
+            return h(false);
+        }
+        let dismissBtn = h(false);
+        if (this.dismissible) {
+            // Add dismiss button
+            dismissBtn = h(
+                'b-button-close',
+                { attrs: { "aria-label": this.dismissLabel }, on: { "click": this.dismiss } },
+                [ this.$slots.dismiss ]
+            );
+        }
+        return h(
+            'div',
+            { class: this.classObject, attrs: { role: 'alert', 'aria-live': 'polite', 'aria-atomic': true } },
+            [ dismissBtn, this.$slots.default ]
+        );
+    },
+    model: {
+        prop: 'show',
+        event: 'input'
+    },
+    data() {
+        return {
+            countDownTimerId: null,
+            dismissed: false
+        };
+    },
+    computed: {
+        classObject() {
+            return ['alert', this.alertVariant, this.dismissible ? 'alert-dismissible' : ''];
+        },
+        alertVariant() {
+            const variant = this.variant;
+            return `alert-${variant}`;
+        },
+        localShow() {
+            return !this.dismissed && (this.countDownTimerId || this.show);
+        }
+    },
+    props: {
+        variant: {
+            type: String,
+            default: 'info'
+        },
+        dismissible: {
+            type: Boolean,
+            default: false
+        },
+        dismissLabel: {
+            type: String,
+            default: 'Close'
+        },
+        show: {
+            type: [Boolean, Number],
+            default: false
+        }
+    },
+    watch: {
+        show() {
+            this.showChanged();
+        }
+    },
+    mounted() {
+        this.showChanged();
+    },
+    destroyed() {
+        this.clearCounter();
+    },
+    methods: {
+        dismiss() {
+            this.clearCounter();
+            this.dismissed = true;
+            this.$emit('dismissed');
+            this.$emit('input', false);
+            if (typeof this.show === 'number') {
+                this.$emit('dismiss-count-down', 0);
+                this.$emit('input', 0);
+            } else {
+                this.$emit('input', false);
+            }
+        },
+        clearCounter() {
+            if (this.countDownTimerId) {
+                clearInterval(this.countDownTimerId);
+                this.countDownTimerId = null;
+            }
+        },
+        showChanged() {
+            // Reset counter status
+            this.clearCounter();
+            // Reset dismiss status
+            this.dismissed = false;
+            // No timer for boolean values
+            if (this.show === true || this.show === false || this.show === null || this.show === 0) {
+                return;
+            }
+            // Start counter
+            let dismissCountDown = this.show;
+            this.countDownTimerId = setInterval(() => {
+                if (dismissCountDown < 1) {
+                    this.dismiss();
+                    return;
+                }
+                dismissCountDown--;
+                this.$emit('dismiss-count-down', dismissCountDown);
+                this.$emit('input', dismissCountDown);
+             }, 1000);
+        }
+    }
+};