main.js

function get_base_url() {
    const url = document.location.href;
    let i = url.length-1;

    let cnt = 0;

    while(i >=0 ) {
        if(url[i] === '/') cnt++;
        i--;
        if(cnt === 3) break;
    }

    let final_url = "";

    let j = 0;

    while(j <= i) {
        final_url += url[j];
        j++;
    }
    return final_url;
}

function get_branch() {
    const branchName = document
    .querySelector("#ref-picker-commits")
    ?.getAttribute("aria-label")
    ?.replace(/ branch$/, "");
    return branchName;
}

function get_sha() {
    const latestCommit = [...document.querySelectorAll(
        'a[href*="/commit/"]'
    )].find(a => /\/commit\/[a-f0-9]{40}/i.test(a.pathname));

    const SHA = latestCommit?.pathname.match(
        /\/commit\/([a-f0-9]{40})/i
    )?.[1];

    if(latestCommit === undefined) {
        alert('cant find SHA open issue at: https://github.com/Anxhul10/github-root-commit/issues')
    }
    return SHA;
}
function get_url() {
    const base_url = get_base_url();
    const SHA = get_sha();
    const branch = get_branch();

    let total_commit = Number(sessionStorage.getItem("Anxhul10"+base_url+"-total-commits"));
    if(!total_commit) {
        total_commit = Number(prompt("enter repo total commits"));
    } 

    const jump = total_commit-35+1;
    if(jump < 0) {
        alert(
            "You're already on the root commit page: https://github.com/Anxhul10/github-root-commit/issues"
        )
        return null;
    }
    const URL = `${base_url}/commits/${branch}/?after=${SHA}+${jump}`
    return URL;
}

function normalize_url(url) {
    if(url == null) return null;
    const url_split = url.split('/');
    return url_split[0]+'//'+url_split[2]+'/'+url_split[3]+'/'+url_split[4];
}

function runner() {
    // to make it work dynamically we need to know the number of commints to skip after the current commit SHA
    const base_url = get_base_url();
    const normal_url = normalize_url(base_url);
    let res = sessionStorage.getItem("Anxhul10"+normal_url+"-oldest-url");

    if(!res) {
        const URL = get_url();
        if(!URL) {
            return document.location.href;
        }
        sessionStorage.setItem("Anxhul10"+normal_url+"-oldest-url", URL);
        return URL;
    }
    return res;
}
function normalize_commit(total_commit) {
    let commits = "";

    for(let i = 0 ; i < total_commit.length; i++) {
        if(total_commit[i] >= "0" && total_commit[i] <= "9") {
            commits += total_commit[i];
        }
    }
    return commits;
}
const observer = new MutationObserver(() => {
    const root = document.location.href;
    
    if(root.split("/").length === 5 && !sessionStorage.getItem("Anxhul10"+root+"-total-commits")) {
        const cmtContainer = document.querySelector(
            'a[href*="/commits/"]'
        );

        const total_commits = cmtContainer
            ?.querySelector('[data-component="text"] span')
            ?.textContent;
        
        const commit = normalize_commit(total_commits);
        sessionStorage.setItem("Anxhul10"+root+"-total-commits", commit);
        return;
    }
    // document.body.style.border = "5px solid red";

    const curr_div = document.querySelector(
        ".d-flex.flex-column.flex-sm-row.gap-2"
    )
    if(root.split('/')[5] === "commits") {
        if(!curr_div)return;
        if(document.getElementById("jumper-div")) return;

        const main_div = document.createElement("div");
        main_div.id = "jumper-div";

        const btn = document.createElement("button");

        btn.id = "btn-id";
        btn.textContent = "Jump to oldest commits";

        btn.addEventListener("click", function () {
            location.href = runner();
        })

        btn.classList.add("button-40");

        main_div.appendChild(btn);
        curr_div.appendChild(main_div);
    }
    return;
})

observer.observe(document.body, {
    childList: true,
    subtree: true
});