import {Injectable} from '@angular/core';
import {ApiService} from './api.service';
import PageRecord from '../structures/PageRecord';
import HostRecord from '../structures/HostRecord';
import {EditorNodeContract} from '../components/nodes/EditorNode.contract';
import {BehaviorSubject, Subscription} from 'rxjs';

export class NoPageLoadedError extends Error {
    constructor(msg = 'There is no page open for editing.') {
        super(msg);
    }
}

@Injectable({
    providedIn: 'root'
})
export class EditorService {
    protected currentPage?: PageRecord;
    protected currentNodes: HostRecord[] = [];
    protected nodeIdToEditorContract: { [key: string]: EditorNodeContract } = {};
    protected dirtyOverride = false;
    protected ready$: BehaviorSubject<boolean> = new BehaviorSubject<boolean>(false);
    protected subs: Subscription[] = [];

    public get immutableNodes(): HostRecord[] {
        return [...this.currentNodes];
    }

    public get mutablePageName(): string {
        if ( this.currentPage ) {
            return this.currentPage.Name;
        }

        return '';
    }

    public set mutablePageName(name: string) {
        if ( this.currentPage && this.canEdit() ) {
            if ( this.currentPage.Name !== name ) {
                this.dirtyOverride = true;
            }

            this.currentPage.Name = name;
        }
    }

    constructor(
        protected api: ApiService,
    ) {
        console.log('editor service', this);
    }

    async startEditing(pageId: string) {
        if ( this.currentPage ) {
            await this.stopEditing();
        }

        this.currentPage = await this.loadPage(pageId);
        this.currentNodes = await this.loadNodes(pageId);
        await this.ready$.next(true);
        console.log('editing', this.currentPage);
        console.log('nodes', this.currentNodes);
    }

    async stopEditing() {
        delete this.currentPage;
        this.currentNodes = [];
        this.nodeIdToEditorContract = {};
        this.subs.forEach(sub => sub.unsubscribe());
        this.subs = [];
        this.ready$.next(false);
    }

    async save() {
        if ( !(await this.needsSave()) ) {
            return;
        }

        const editors = Object.values(this.nodeIdToEditorContract);

        // Save all editors that handle their data independently first
        await Promise.all(editors.map(async editor => {
            if ( await editor.needsSave() ) {
                await editor.performSave();
            }
        }));

        // Tell the editors to write their state changes to the HostRecords
        await Promise.all(editors.map(async editor => {
            await editor.writeChangesToNode();
        }));

        await this.saveNodesAsPage(this.currentPage, this.currentNodes);
    }

    async saveNodesAsPage(page: PageRecord, nodes: HostRecord[]) {
        await new Promise((res, rej) => {
            const saveNodes = nodes.map(x => {
                x.PageId = page.UUID;
                return x.toSave();
            });

            this.api.post(`/page/${page.UUID}/nodes/save`, saveNodes).subscribe({
                next: result => {
                    res(); // TODO load in returned data!!
                },
                error: rej,
            });
        });
    }

    async needsSave() {
        if ( this.dirtyOverride ) {
            return true;
        }

        const dirties = await Promise.all(Object.values(this.nodeIdToEditorContract).map(editor => editor.isDirty()));
        const needSaves = await Promise.all(Object.values(this.nodeIdToEditorContract).map(editor => editor.needsSave()));

        return dirties.some(Boolean) || needSaves.some(Boolean);
    }

    async deleteNode(nodeId: string) {
        if ( !this.currentPage ) {
            throw new NoPageLoadedError();
        }

        const node = this.currentNodes.find(maybeNode => maybeNode.UUID === nodeId);
        if ( !node ) {
            throw new Error('Invalid node ID.');
        }

        const editor = this.nodeIdToEditorContract[nodeId];
        if ( editor ) {
            await editor.performDelete();
            delete this.nodeIdToEditorContract[nodeId];
        }

        this.currentNodes = this.currentNodes.filter(x => x.UUID !== nodeId);
        this.dirtyOverride = true;
    }

    canEdit() {
        if ( !this.currentPage ) {
            throw new NoPageLoadedError();
        }

        return !this.currentPage.isViewOnly();
    }

    async registerNodeEditor(nodeId: string, editor: EditorNodeContract) {
        return new Promise((res, rej) => {
            const sub = this.ready$.subscribe(async val => {
                if ( val ) {
                    try {
                        if ( !this.currentPage ) {
                            return rej(new NoPageLoadedError());
                        }

                        const node = this.currentNodes.find(maybeNode => maybeNode.UUID === nodeId);
                        if ( !node ) {
                            return rej(new Error('Invalid node ID.'));
                        }

                        editor.page = this.currentPage;
                        editor.node = node;
                        this.nodeIdToEditorContract[nodeId] = editor;

                        if ( editor.needsLoad() ) {
                            await editor.performLoad();
                        }

                        res();
                    } catch (e) {
                        rej(e);
                    }
                }
            });

            this.subs.push(sub);
        });
    }

    async unregisterNodeEditor(nodeId: string) {
        if ( !this.currentPage ) {
            throw new NoPageLoadedError();
        }

        delete this.nodeIdToEditorContract[nodeId];
    }

    async loadPage(pageId: string): Promise<PageRecord> {
        return new Promise((res, rej) => {
            this.api.get(`/page/${pageId}`).subscribe({
                next: result => {
                    res(new PageRecord(result.data));
                },
                error: rej,
            });
        });
    }

    async loadNodes(pageId: string): Promise<HostRecord[]> {
        return new Promise((res, rej) => {
            this.api.get(`/page/${pageId}/nodes`).subscribe({
                next: result => {
                    res(result.data.map(rec => {
                        const host = new HostRecord(rec.Value.Value);
                        host.load(rec);
                        return host;
                    }));
                },
                error: rej,
            });
        });
    }
}