import { Location } from "@angular/common";
import { inject, Injectable, OnDestroy } from "@angular/core";
import { MatDialog } from "@angular/material/dialog";
import { MatSnackBar } from "@angular/material/snack-bar";
import { ActivatedRoute } from "@angular/router";
import { BehaviorSubject, Observable, Subscription } from "rxjs";
import { Publication } from "../../core/rest-services/publications/model/publication";
import { PublicationRestService } from "../../core/rest-services/publications/publication.rest-service";
import { copy } from "../../core/utils/ObjectUtils";
import { CodeBlockDialog } from "./code-block-dialog/code-block-dialog.component";
import { PictureSelectionDialog } from "./picture-selection-dialog/picture-selection-dialog.component";

declare let Prism: any;

export class CursorPosition {
    start: number;
    end: number;
    selectedCharacters: number;

    constructor(start: number, end: number) {
        this.start = start;
        this.end = end;
        this.selectedCharacters = end - start;
    }
}

export interface PublicationEditionState {
    publication: Publication;
    cursorPosition: CursorPosition;
}

const DEFAULT_PUBLICATION: Publication = {
    id: '',
    key: '',
    title: '',
    text: '',
    parsedText: '',
    description: '',
    creationDate: new Date(),
    illustrationId: '',
    categoryId: '',
    author: {
        id: '',
        name: '',
        image: ''
    }
};

const DEFAULT_CURSOR_POSITION = new CursorPosition(0, 0);

const DEFAULT_STATE: PublicationEditionState = {
    publication: DEFAULT_PUBLICATION,
    cursorPosition: DEFAULT_CURSOR_POSITION
};

@Injectable()
export class PublicationEditionService implements OnDestroy {
    private readonly activatedRoute = inject(ActivatedRoute);
    private readonly publicationRestService = inject(PublicationRestService);
    private readonly location = inject(Location);
    private readonly snackBar = inject(MatSnackBar);
    private readonly dialog = inject(MatDialog);

    private isLoadingSubject = new BehaviorSubject<boolean>(false);
    private stateSubject = new BehaviorSubject<PublicationEditionState>(copy(DEFAULT_STATE));
    private subscriptions: Subscription[] = [];
    private isSavingSubject = new BehaviorSubject<boolean>(false);
    private isPreviewingSubject = new BehaviorSubject<boolean>(false);

    ngOnDestroy(): void {
        this.subscriptions.forEach(subscription => subscription.unsubscribe());
    }

    private get _state(): PublicationEditionState {
        return this.stateSubject.value;
    }

    private _save(state: PublicationEditionState): void {
        this.stateSubject.next(state);    
    }

    get isLoading$(): Observable<boolean> {
        return this.isLoadingSubject.asObservable();
    }

    get isSaving$(): Observable<boolean> {
        return this.isSavingSubject.asObservable();
    }

    get isPreviewing$(): Observable<boolean> {
        return this.isPreviewingSubject.asObservable();
    }

    get state$(): Observable<PublicationEditionState> {
        return this.stateSubject.asObservable();
    }

    loadPublication(): void {
        this.isLoadingSubject.next(true);
        
        this.activatedRoute.paramMap.subscribe(params => {
            const publicationId = params.get('publicationId');
            if (publicationId == undefined) {
                this.snackBar.open('A technical error occurred while loading publication data.', 'Close', {duration: 5000});
                this.location.back();
            } else {
                this.publicationRestService.getById(publicationId)
                .then(publication => {
                    const state = this._state;
                    state.publication = publication;
                    this.stateSubject.next(state);
                })
                .catch(error => {
                    const errorMessage = 'A technical error occurred while loading publication data.';
                    this.snackBar.open(errorMessage, 'Close', {duration: 5000});
                    console.error(errorMessage, error)
                })
                .finally(() => this.isLoadingSubject.next(false));
            }
          });
    }

    init(publication: Publication): void {
        const state = this._state;
        state.publication = publication;
        this.stateSubject.next(state);
    }

    editTitle(title: string): void {
        const state = this._state;
        state.publication.title = title;
        this._save(state);
    }

    editDescription(description: string): void {
        const state = this._state;
        state.publication.description = description;
        this._save(state);
    }

    editCategoryId(categoryId: string): void {
        const state = this._state;
        state.publication.categoryId = categoryId;
        this._save(state);
    }

    editText(text: string): void {
        const state = this._state;
        state.publication.text = text;
        this._save(state);
    }

    editIllustrationId(pictureId: string): void {
        const state = this._state;
        state.publication.illustrationId = pictureId
        this._save(state);
    }

    displayPictureSectionDialog(): void {
        const dialogRef = this.dialog.open(PictureSelectionDialog);

        const afterDialogCloseSubscription = dialogRef.afterClosed()
            .subscribe(newPictureId => {
                if (newPictureId) {
                    this.editIllustrationId(newPictureId);
                }
            });
        this.subscriptions.push(afterDialogCloseSubscription);
    }

    displayCodeBlockDialog(): void {
        const dialogRef = this.dialog.open(CodeBlockDialog, { width: '60em' });

        const afterDialogCloseSubscription = dialogRef.afterClosed()
            .subscribe(codeBlockWithLanguage => {
                if (codeBlockWithLanguage) {
                    this.insertCodeBlock(codeBlockWithLanguage.programmingLanguage, codeBlockWithLanguage.codeBlock);
                }
            });
        this.subscriptions.push(afterDialogCloseSubscription);
    }

    editCursorPosition(positionStart: number, positionEnd: number): void {
        const state = this._state;

        state.cursorPosition.start = positionStart;
        state.cursorPosition.end = positionEnd;

        this._save(state);
    }

    insertTitle(titleNumber: number): void {
        if (titleNumber >= 1 && titleNumber <= 3) {
            const state = this._state;

            const publication = state.publication;

            const publicationTextLeftPart = publication.text.substring(0, state.cursorPosition.start);
            const publicationTextMiddlePart = publication.text.substring(state.cursorPosition.start, state.cursorPosition.end);
            const publicationTextRightPart = publication.text.substring(state.cursorPosition.end);
            const textWithTags = `${publicationTextLeftPart}[h${titleNumber}]${publicationTextMiddlePart}[/h${titleNumber}]${publicationTextRightPart}`;

            publication.text = textWithTags;

            this._save(state);
        } else {
            console.error(`Bad value for parameter of function 'insertTitle': '${titleNumber}'.`);
        }
    }

    selectAPicture(): void {
        const dialogRef = this.dialog.open(PictureSelectionDialog);

        const afterDialogCloseSubscription = dialogRef.afterClosed()
            .subscribe(newPictureId => {
                if (newPictureId) {
                    this.insertPicture(newPictureId);
                }
            });
        this.subscriptions.push(afterDialogCloseSubscription);
    }

    insertPicture(pictureId: string): void {
        const state = this._state;

        const publication = state.publication;

        const publicationTextLeftPart = publication.text.substring(0, state.cursorPosition.start);
        const publicationTextRightPart = publication.text.substring(state.cursorPosition.start);
        const textWithTags = `${publicationTextLeftPart}[img src="/api/pictures/${pictureId}" /]${publicationTextRightPart}`;

        publication.text = textWithTags;

        this._save(state);
    }

    insertLink(): void {
        const state = this._state;

        const publication = state.publication;

        const publicationTextLeftPart = publication.text.substring(0, state.cursorPosition.start);
        const publicationTextMiddlePart = publication.text.substring(state.cursorPosition.start, state.cursorPosition.end);
        const publicationTextRightPart = publication.text.substring(state.cursorPosition.end);
        const textWithTags = `${publicationTextLeftPart}[link href="" txt="${publicationTextMiddlePart}" /]${publicationTextRightPart}`;

        publication.text = textWithTags;

        this._save(state);
    }

    insertCodeBlock(programmingLanguage: string, codeBlock: string): void {
        const state = this._state;

        const publication = state.publication;

        const publicationTextLeftPart = publication.text.substring(0, state.cursorPosition.start);
        const publicationTextRightPart = publication.text.substring(state.cursorPosition.start);
        const codeBlockInstruction = `\n[code lg="${programmingLanguage}"]\n${codeBlock}\n[/code]\n\n`;
        const textWithTags = `${publicationTextLeftPart}${codeBlockInstruction}${publicationTextRightPart}`;

        publication.text = textWithTags;

        this._save(state);
    }

    loadPreview(): void {
        const state = this._state;

        this.isPreviewingSubject.next(true);
        this.publicationRestService.preview(state.publication.text)
            .then(parsedText => {
                state.publication.parsedText = parsedText;
                this._save(state);
                setTimeout(() => Prism.highlightAll(), 1000);
            })
            .catch(error => {
                console.error(error);
            })
            .finally(() => {
                this.isPreviewingSubject.next(false);
            });
    }
}