favicon.ts

/*
Copyright 2020 New Vector Ltd

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

interface IParams {
    // colour parameters
    bgColor: string;
    textColor: string;
    // font styling parameters
    fontFamily: string;
    fontWeight: "normal" | "italic" | "bold" | "bolder" | "lighter" | number;

    // positioning parameters
    isUp: boolean;
    isLeft: boolean;
}

const defaults: IParams = {
    bgColor: "#d00",
    textColor: "#fff",
    fontFamily: "sans-serif", // Arial,Verdana,Times New Roman,serif,sans-serif,...
    fontWeight: "bold", // normal,italic,oblique,bold,bolder,lighter,100,200,300,400,500,600,700,800,900

    isUp: false,
    isLeft: false,
};

// Allows dynamic rendering of a circular badge atop the loaded favicon
// supports colour, font and basic positioning parameters.
// Based upon https://github.com/ejci/favico.js/blob/master/favico.js [MIT license]
export default class Favicon {
    private readonly browser = {
        ff: typeof window.InstallTrigger !== "undefined",
        opera: !!window.opera || navigator.userAgent.includes("Opera"),
    };

    private readonly params: IParams;
    private readonly canvas: HTMLCanvasElement;
    private readonly baseImage: HTMLImageElement;
    private context: CanvasRenderingContext2D;
    private icons: HTMLLinkElement[];

    private isReady = false;
    // callback to run once isReady is asserted, allows for a badge to be queued for when it can be shown
    private readyCb = () => {};

    constructor(params: Partial<IParams> = {}) {
        this.params = { ...defaults, ...params };

        this.icons = Favicon.getIcons();
        // create work canvas
        this.canvas = document.createElement("canvas");
        // create clone of favicon as a base
        this.baseImage = document.createElement("img");

        const lastIcon = this.icons[this.icons.length - 1];
        if (lastIcon.hasAttribute("href")) {
            this.baseImage.setAttribute("crossOrigin", "anonymous");
            this.baseImage.onload = () => {
                // get height and width of the favicon
                this.canvas.height = (this.baseImage.height > 0) ? this.baseImage.height : 32;
                this.canvas.width = (this.baseImage.width > 0) ? this.baseImage.width : 32;
                this.context = this.canvas.getContext("2d");
                this.ready();
            };
            this.baseImage.setAttribute("src", lastIcon.getAttribute("href"));
        } else {
            this.canvas.height = this.baseImage.height = 32;
            this.canvas.width = this.baseImage.width = 32;
            this.context = this.canvas.getContext("2d");
            this.ready();
        }
    }

    private reset() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
        this.context.drawImage(this.baseImage, 0, 0, this.canvas.width, this.canvas.height);
    }

    private options(n: number | string, params: IParams) {
        const opt = {
            n: ((typeof n) === "number") ? Math.abs(n as number | 0) : n,
            len: ("" + n).length,
            // badge positioning constants as percentages
            x: 0.4,
            y: 0.4,
            w: 0.6,
            h: 0.6,
        };

        // apply positional transformations
        if (params.isUp) {
            if (opt.y < 0.6) {
                opt.y = opt.y - 0.4;
            } else {
                opt.y = opt.y - 2 * opt.y + (1 - opt.w);
            }
        }
        if (params.isLeft) {
            if (opt.x < 0.6) {
                opt.x = opt.x - 0.4;
            } else {
                opt.x = opt.x - 2 * opt.x + (1 - opt.h);
            }
        }

        // scale the position to the canvas
        opt.x = this.canvas.width * opt.x;
        opt.y = this.canvas.height * opt.y;
        opt.w = this.canvas.width * opt.w;
        opt.h = this.canvas.height * opt.h;
        return opt;
    }

    private circle(n: number | string, opts?: Partial<IParams>) {
        const params = { ...this.params, ...opts };
        const opt = this.options(n, params);

        let more = false;
        if (opt.len === 2) {
            opt.x = opt.x - opt.w * 0.4;
            opt.w = opt.w * 1.4;
            more = true;
        } else if (opt.len >= 3) {
            opt.x = opt.x - opt.w * 0.65;
            opt.w = opt.w * 1.65;
            more = true;
        }

        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
        this.context.drawImage(this.baseImage, 0, 0, this.canvas.width, this.canvas.height);
        this.context.beginPath();
        const fontSize = Math.floor(opt.h * (opt.n > 99 ? 0.85 : 1)) + "px";
        this.context.font = `${params.fontWeight} ${fontSize} ${params.fontFamily}`;
        this.context.textAlign = "center";

        if (more) {
            this.context.moveTo(opt.x + opt.w / 2, opt.y);
            this.context.lineTo(opt.x + opt.w - opt.h / 2, opt.y);
            this.context.quadraticCurveTo(opt.x + opt.w, opt.y, opt.x + opt.w, opt.y + opt.h / 2);
            this.context.lineTo(opt.x + opt.w, opt.y + opt.h - opt.h / 2);
            this.context.quadraticCurveTo(opt.x + opt.w, opt.y + opt.h, opt.x + opt.w - opt.h / 2, opt.y + opt.h);
            this.context.lineTo(opt.x + opt.h / 2, opt.y + opt.h);
            this.context.quadraticCurveTo(opt.x, opt.y + opt.h, opt.x, opt.y + opt.h - opt.h / 2);
            this.context.lineTo(opt.x, opt.y + opt.h / 2);
            this.context.quadraticCurveTo(opt.x, opt.y, opt.x + opt.h / 2, opt.y);
        } else {
            this.context.arc(opt.x + opt.w / 2, opt.y + opt.h / 2, opt.h / 2, 0, 2 * Math.PI);
        }

        this.context.fillStyle = params.bgColor;
        this.context.fill();
        this.context.closePath();
        this.context.beginPath();
        this.context.stroke();
        this.context.fillStyle = params.textColor;

        if ((typeof opt.n) === "number" && opt.n > 999) {
            const count = ((opt.n > 9999) ? 9 : Math.floor(opt.n as number / 1000)) + "k+";
            this.context.fillText(count, Math.floor(opt.x + opt.w / 2), Math.floor(opt.y + opt.h - opt.h * 0.2));
        } else {
            this.context.fillText("" + opt.n, Math.floor(opt.x + opt.w / 2), Math.floor(opt.y + opt.h - opt.h * 0.15));
        }

        this.context.closePath();
    }

    private ready() {
        if (this.isReady) return;
        this.isReady = true;
        this.readyCb();
    }

    private setIcon(canvas) {
        setImmediate(() => {
            this.setIconSrc(canvas.toDataURL("image/png"));
        });
    }

    private setIconSrc(url) {
        // if is attached to fav icon
        if (this.browser.ff || this.browser.opera) {
            // for FF we need to "recreate" element, attach to dom and remove old <link>
            const old = this.icons[this.icons.length - 1];
            const newIcon = window.document.createElement("link");
            this.icons = [newIcon];
            newIcon.setAttribute("rel", "icon");
            newIcon.setAttribute("type", "image/png");
            window.document.getElementsByTagName("head")[0].appendChild(newIcon);
            newIcon.setAttribute("href", url);
            if (old.parentNode) {
                old.parentNode.removeChild(old);
            }
        } else {
            this.icons.forEach(icon => {
                icon.setAttribute("href", url);
            });
        }
    }

    public badge(content: number | string, opts?: Partial<IParams>) {
        if (!this.isReady) {
            this.readyCb = () => {
                this.badge(content, opts);
            };
            return;
        }

        if (typeof content === "string" || content > 0) {
            this.circle(content, opts);
        } else {
            this.reset();
        }

        this.setIcon(this.canvas);
    }

    private static getLinks() {
        const icons: HTMLLinkElement[] = [];
        const links = window.document.getElementsByTagName("head")[0].getElementsByTagName("link");
        for (let i = 0; i < links.length; i++) {
            if ((/(^|\s)icon(\s|$)/i).test(links[i].getAttribute("rel"))) {
                icons.push(links[i]);
            }
        }
        return icons;
    }

    private static getIcons() {
        // get favicon link elements
        let elms = Favicon.getLinks();
        if (elms.length === 0) {
            elms = [window.document.createElement("link")];
            elms[0].setAttribute("rel", "icon");
            window.document.getElementsByTagName("head")[0].appendChild(elms[0]);
        }

        elms.forEach(item => {
            item.setAttribute("type", "image/png");
        });
        return elms;
    }
}