server/front/src/Stores/BiggestAvailableAreaStore.ts

import {get, writable} from "svelte/store";
import type {Box} from "../WebRtc/LayoutManager";
import {HtmlUtils} from "../WebRtc/HtmlUtils";
import {LayoutMode} from "../WebRtc/LayoutManager";
import {layoutModeStore} from "./StreamableCollectionStore";

/**
 * Tries to find the biggest available box of remaining space (this is a space where we can center the character)
 */
function findBiggestAvailableArea(): Box {
    const game = HtmlUtils.querySelectorOrFail<HTMLCanvasElement>('#game canvas');
    if (get(layoutModeStore) === LayoutMode.VideoChat) {
        const children = document.querySelectorAll<HTMLDivElement>('div.chat-mode > div');
        const htmlChildren = Array.from(children.values());

        // No chat? Let's go full center
        if (htmlChildren.length === 0) {
            return {
                xStart: 0,
                yStart: 0,
                xEnd: game.offsetWidth,
                yEnd: game.offsetHeight
            }
        }

        const lastDiv = htmlChildren[htmlChildren.length - 1];
        // Compute area between top right of the last div and bottom right of window
        const area1 = (game.offsetWidth - (lastDiv.offsetLeft + lastDiv.offsetWidth))
            * (game.offsetHeight - lastDiv.offsetTop);

        // Compute area between bottom of last div and bottom of the screen on whole width
        const area2 = game.offsetWidth
            * (game.offsetHeight - (lastDiv.offsetTop + lastDiv.offsetHeight));

        if (area1 < 0 && area2 < 0) {
            // If screen is full, let's not attempt something foolish and simply center character in the middle.
            return {
                xStart: 0,
                yStart: 0,
                xEnd: game.offsetWidth,
                yEnd: game.offsetHeight
            }
        }
        if (area1 <= area2) {
            return {
                xStart: 0,
                yStart: lastDiv.offsetTop + lastDiv.offsetHeight,
                xEnd: game.offsetWidth,
                yEnd: game.offsetHeight
            }
        } else {
            return {
                xStart: lastDiv.offsetLeft + lastDiv.offsetWidth,
                yStart: lastDiv.offsetTop,
                xEnd: game.offsetWidth,
                yEnd: game.offsetHeight
            }
        }
    } else {
        // Possible destinations: at the center bottom or at the right bottom.
        const mainSectionChildren = Array.from(document.querySelectorAll<HTMLDivElement>('div.main-section > div').values());
        const sidebarChildren = Array.from(document.querySelectorAll<HTMLDivElement>('aside.sidebar > div').values());

        // No presentation? Let's center on the screen
        if (mainSectionChildren.length === 0) {
            return {
                xStart: 0,
                yStart: 0,
                xEnd: game.offsetWidth,
                yEnd: game.offsetHeight
            }
        }

        // At this point, we know we have at least one element in the main section.
        const lastPresentationDiv = mainSectionChildren[mainSectionChildren.length-1];

        const presentationArea = (game.offsetHeight - (lastPresentationDiv.offsetTop + lastPresentationDiv.offsetHeight))
            * (lastPresentationDiv.offsetLeft + lastPresentationDiv.offsetWidth);

        let leftSideBar: number;
        let bottomSideBar: number;
        if (sidebarChildren.length === 0) {
            leftSideBar = HtmlUtils.getElementByIdOrFail<HTMLDivElement>('sidebar').offsetLeft;
            bottomSideBar = 0;
        } else {
            const lastSideBarChildren = sidebarChildren[sidebarChildren.length - 1];
            leftSideBar = lastSideBarChildren.offsetLeft;
            bottomSideBar = lastSideBarChildren.offsetTop + lastSideBarChildren.offsetHeight;
        }
        const sideBarArea = (game.offsetWidth - leftSideBar)
            * (game.offsetHeight - bottomSideBar);

        if (presentationArea <= sideBarArea) {
            return {
                xStart: leftSideBar,
                yStart: bottomSideBar,
                xEnd: game.offsetWidth,
                yEnd: game.offsetHeight
            }
        } else {
            return {
                xStart: 0,
                yStart: lastPresentationDiv.offsetTop + lastPresentationDiv.offsetHeight,
                xEnd: /*lastPresentationDiv.offsetLeft + lastPresentationDiv.offsetWidth*/ game.offsetWidth , // To avoid flickering when a chat start, we center on the center of the screen, not the center of the main content area
                yEnd: game.offsetHeight
            }
        }
    }
}


/**
 * A store that contains the list of (video) peers we are connected to.
 */
function createBiggestAvailableAreaStore() {

    const { subscribe, set } = writable<Box>({xStart:0, yStart: 0, xEnd: 1, yEnd: 1});

    return {
        subscribe,
        recompute: () => {
            set(findBiggestAvailableArea());
        }
    };
}

export const biggestAvailableAreaStore = createBiggestAvailableAreaStore();