// from /my/site/homepage/www/rdf/streamed-graph.js

import { eachJsonLdQuad } from "./json_ld_quads";
import { N3Store } from 'n3';
import { Store } from 'n3';

export class StreamedGraphClient {
    // holds a n3 Store, which is synced to a server-side
    // store that sends patches over SSE

    onStatus: (msg: string) => void;
    onGraphChanged: () => void;
    store: N3Store;
    events!: EventSource;
    constructor(
        eventsUrl: string,
        onGraphChanged: () => void,
        onStatus: (status: string) => void,
        prefixes: Array<Record<string, string>>,
        staticGraphUrls: Array<string>) {
        console.log('new StreamedGraph', eventsUrl);
        this.onStatus = onStatus;
        this.onGraphChanged = onGraphChanged;
        this.onStatus('startup...');

        this.store = new Store();

        //     //             Object.keys(prefixes).forEach((prefix) => {
        //     //                 this.store.setPrefix(prefix, prefixes[prefix]);
        //     //             });

        this.connect(eventsUrl);
        this.reconnectOnWake();

        //     staticGraphUrls.forEach((url) => {
        //         fetch(url).then((response) => response.text())
        //             .then((body) => {
        //                 // parse with n3, add to output
        //             });
        //     });

    }

    reconnectOnWake() {
        // it's not this, which fires on every mouse-in on a browser window, and doesn't seem to work for screen-turned-back-on
        //window.addEventListener('focus', function() { this.connect(eventsUrl); }.bind(this));
    }

    connect(eventsUrl: string) {
        // need to exit here if this obj has been replaced

        this.onStatus('start connect...');
        this.close();
        if (this.events && this.events.readyState != EventSource.CLOSED) {
            this.onStatus('zombie');
            throw new Error("zombie eventsource");
        }

        this.events = new EventSource(eventsUrl);

        this.events.addEventListener('error', (ev) => {
            // todo: this is piling up tons of retries and eventually multiple connections
            // this.testEventUrl(eventsUrl);
            this.onStatus('connection lost- retrying');
            setTimeout(() => {
                requestAnimationFrame(() => {
                    this.connect(eventsUrl);
                });
            }, 3000);
        });

        this.events.addEventListener('fullGraph', async (ev) => {
            this.onStatus('sync- full graph update');
            await this.replaceFullGraph((ev as MessageEvent).data);
            this.onStatus(`synced ${this.store.size}`);
            this.onGraphChanged();
        });

        this.events.addEventListener('patch', async (ev) => {
            this.onStatus('sync- updating');
            await this.patchGraph((ev as MessageEvent).data);
            this.onStatus(`synced ${this.store.size}`);
            this.onGraphChanged();
        });
        this.onStatus('connecting...');
    }

    // these need some locks
    async replaceFullGraph(jsonLdText: string) {
        this.store = new Store();
        await eachJsonLdQuad(JSON.parse(jsonLdText),
            this.store.addQuad.bind(this.store));
    }

    async patchGraph(patchJson: string) {
        var patch = JSON.parse(patchJson).patch;

        await eachJsonLdQuad(patch.deletes,
            this.store.removeQuad.bind(this.store));
        await eachJsonLdQuad(patch.adds,
            this.store.addQuad.bind(this.store));
    }

    close() {
        if (this.events) {
            this.events.close();
        }
    }

    async testEventUrl(eventsUrl: string): Promise<void> {
        return new Promise<void>((resolve, reject) => {
            this.onStatus('testing connection');
            fetch(eventsUrl, {
                method: "HEAD",
                credentials: "include",
            }).then((value) => {
                if (value.status == 403) {
                    reject();
                    return;
                }
                resolve();
            }).catch((err) => {
                reject();
            });
        });
    }

}