2 files changed, 253 insertions, 0 deletions
diff --git a/shared/metrics-8/src/impressions/constants.ts b/shared/metrics-8/src/impressions/constants.ts
new file mode 100644
index 0000000..0638f9e
--- /dev/null
+++ b/shared/metrics-8/src/impressions/constants.ts
@@ -0,0 +1 @@
+export const IMPRESSION_CONTEXT_NAME = 'metrics:impression' as const;
diff --git a/shared/metrics-8/src/impressions/index.ts b/shared/metrics-8/src/impressions/index.ts
new file mode 100644
index 0000000..b904feb
--- /dev/null
+++ b/shared/metrics-8/src/impressions/index.ts
@@ -0,0 +1,252 @@
+import type { Logger, LoggerFactory } from '@amp/web-apps-logger/src/types';
+import { IMPRESSION_CONTEXT_NAME } from './constants';
+import { createSvelteImpressionAction } from './utils/svelte/impressions-svelte-action';
+import type {
+    AppImpressionModel,
+    ImpressionSettings,
+    ImpressionsInstance,
+} from './types';
+import type {
+    ImpressionObserver,
+    newInstanceWithMetricsConfig,
+} from '@amp-metrics/mt-impressions-observer';
+import type { ClickstreamProcessor } from '@amp-metrics/mt-metricskit-processor-clickstream';
+
+/**
+ * Adapter class to handle interactions with
+ * metricsKit impression observer.
+ */
+export class Impressions implements ImpressionsInstance {
+    private readonly logger: Logger;
+    private impressionObserverInstance: ImpressionObserver | undefined;
+    private hasInitialized: boolean = false;
+    private impressionDataMap: Map<HTMLElement, any> = new Map();
+    private currentSnapshot: Record<string, unknown>[] = [];
+    private readonly impressionSettings: ImpressionSettings | undefined;
+
+    constructor(
+        loggerFactory: LoggerFactory,
+        context: Map<string, unknown>,
+        settings?: ImpressionSettings,
+    ) {
+        this.logger = loggerFactory.loggerFor(IMPRESSION_CONTEXT_NAME);
+        this.impressionSettings = settings;
+
+        context.set(IMPRESSION_CONTEXT_NAME, this);
+    }
+
+    async init(
+        makeImpressionObserver: typeof newInstanceWithMetricsConfig,
+        clickStreamInstance: ClickstreamProcessor,
+    ) {
+        if (this.hasInitialized) {
+            this.logger.warn(
+                'Ignoring, Impressions.init() can only be called once',
+            );
+            return;
+        }
+
+        const options = { root: document, rootMargin: '0px' };
+        const config = clickStreamInstance.config;
+        const impressionObserver: ImpressionObserver =
+            await makeImpressionObserver(config, options);
+
+        impressionObserver.setDelegate({
+            extractImpressionInfo: (domNode: HTMLElement) => {
+                const dataMap = this.impressionDataMap;
+                const nodeMetricData = dataMap.get(domNode);
+                if (nodeMetricData) {
+                    const impressionData = nodeMetricData.impressionMetrics;
+                    impressionData.location =
+                        clickStreamInstance.utils.eventFields.buildLocationStructure(
+                            domNode,
+                            (node: HTMLElement) => {
+                                const metrics = dataMap.get(node);
+                                if (metrics?.location) {
+                                    return metrics.location;
+                                }
+                                return;
+                            },
+                        );
+                    return impressionData;
+                } else {
+                    this.logger.warn('no impression data found for', domNode);
+                }
+            },
+        });
+
+        this.impressionObserverInstance = impressionObserver;
+        this.impressionDataMap.forEach((_value, node) => {
+            this.logger.debug('observing deffered node', node);
+            this.impressionObserverInstance?.observe(node);
+        });
+        this.hasInitialized = true;
+
+        this.logger.debug('impressions initialized');
+    }
+
+    get settings() {
+        return this.impressionSettings;
+    }
+
+    isEnabled(event: 'click' | 'exit' | 'impressions'): boolean {
+        if (this.impressionSettings?.captureType === 'jet') {
+            return (
+                this.impressionSettings?.metricsKitEvents?.includes(event) ??
+                false
+            );
+        }
+        return true;
+    }
+
+    consumeImpressions(): Record<string, unknown>[] | undefined {
+        if (this.hasInitialized) {
+            this.logger.debug('consuming impression metrics');
+            return this.impressionObserverInstance?.consumeImpressions();
+        }
+        this.logger.warn('impressions not avaiable yet');
+        return;
+    }
+
+    captureSnapshotImpression(): Record<string, unknown>[] | undefined {
+        const snapshot =
+            this.impressionObserverInstance?.snapshotImpressions() ?? [];
+
+        // if the current page already transitioned. fallback to the snapshot we captured before transition
+        if (snapshot.length === 0) {
+            return this.getSnapshotImpression();
+        }
+
+        return snapshot;
+    }
+
+    getSnapshotImpression(): Record<string, unknown>[] | undefined {
+        if (this.hasInitialized) {
+            return this.currentSnapshot;
+        }
+        this.logger.warn('impressions not avaiable yet');
+        return;
+    }
+
+    setCurrentSnapshot(): void {
+        if (this.hasInitialized) {
+            this.logger.debug('capturing impression snapshot');
+            this.currentSnapshot =
+                this.impressionObserverInstance?.snapshotImpressions() ?? [];
+        } else {
+            this.logger.warn('impressions not avaiable yet');
+        }
+    }
+
+    get nodeList() {
+        const impressionClass = this;
+
+        return new Proxy(impressionClass.impressionDataMap, {
+            get(target, prop, receiver) {
+                const orginalFn = Reflect.get(target, prop, receiver);
+
+                // overriding 'set' to also be able to observe
+                if (prop === 'set') {
+                    return (
+                        node: HTMLElement,
+                        value: Record<string, unknown>,
+                    ) => {
+                        if (impressionClass.hasInitialized) {
+                            impressionClass.logger.debug(
+                                'observing',
+                                node,
+                                value,
+                            );
+
+                            impressionClass.impressionObserverInstance?.observe(
+                                node,
+                            );
+                        }
+
+                        return orginalFn.bind(target)(node, value);
+                    };
+                }
+
+                // overriding 'delete' to also be able to unobserve
+                if (prop === 'delete') {
+                    return (node: HTMLElement) => {
+                        if (impressionClass.hasInitialized) {
+                            impressionClass.logger.debug('unobserve', node);
+                            impressionClass.impressionObserverInstance?.unobserve(
+                                node,
+                            );
+                        }
+
+                        return orginalFn.bind(target)(node);
+                    };
+                }
+
+                return orginalFn.bind(target);
+            },
+            set(target, prop, value) {
+                return Reflect.set(target, prop, value);
+            },
+        });
+    }
+}
+
+/**
+ * Server Noop for above
+ */
+class ServerNoopImpressions implements ImpressionsInstance {
+    readonly nodeList: WeakMap<any, any>;
+    constructor() {
+        this.nodeList = new WeakMap();
+    }
+    setCurrentSnapshot(): void {}
+}
+
+/**
+ * Gets the current Impression instance from the Svelte context.
+ *
+ * @return The current instance of Impression
+ */
+export function generateBrowserImpressionsContextGetter(
+    getContext: (context: string) => unknown,
+): () => AppImpressionModel {
+    return function getImpressions(): AppImpressionModel {
+        const impressions = getContext(IMPRESSION_CONTEXT_NAME) as
+            | Impressions
+            | undefined;
+
+        if (!impressions) {
+            const noopImpressions = new ServerNoopImpressions();
+            return {
+                captureImpressions: (_node: any, _impressionsData: any) => {
+                    return {
+                        destroy() {},
+                    };
+                },
+                impressions: noopImpressions,
+            };
+        }
+
+        return {
+            captureImpressions: createSvelteImpressionAction(impressions),
+            impressions,
+        };
+    };
+}
+
+/**
+ * Server No-op for generateImpressionsContextGetter
+ *
+ */
+export function generateServerImpressionsContextGetter(
+    _getContext: (context: string) => unknown,
+): () => AppImpressionModel {
+    const impressions = new ServerNoopImpressions();
+    return () => ({
+        captureImpressions: (_node: any, _impressionsData: any) => {
+            return {
+                destroy() {},
+            };
+        },
+        impressions,
+    });
+}