// makes a table of contents
// top level is h2, goes down from there

let elt_toc   = document.getElementById("toc");
let elts_enum = document.getElementsByClassName("enum");

// top level is h2
// if we see a bigger level
let last_level = 2;

let h2_idx = 0;
let h3_idx = 0;
let h4_idx = 0;
let h5_idx = 0;

// if we see an h2, reset the h3/h4/h5 indexes to 0
// if we see an h3, reset the h4/h5 indexes to 0
// so on
function reset_below(level) {
    switch(level) {
        case 2:  h3_idx = 0;
        case 3:  h4_idx = 0;
        case 4:  h5_idx = 0;
        default: break;
    }
}

// str index; e.g. "1.3.4"
function str_idx(level) {
    // build up components in reverse
    // so an h4 shouldn't have any h5 data
    let components = [];
    switch(level) {
        case 5: components.push(h5_idx);
        case 4: components.push(h4_idx);
        case 3: components.push(h3_idx);
        case 2: components.push(h2_idx);
        default: break;
    }
    components.reverse();
    return components.join(".");
}

// when we see a new element, increment the index
function incr(level) {
    switch(level) {
        case 2:  h2_idx += 1; break;
        case 3:  h3_idx += 1; break;
        case 4:  h4_idx += 1; break;
        case 5:  h5_idx += 1; break;
        default: break;
    }
}

for (let this_enum_elt of elts_enum)
{
    switch(this_enum_elt.tagName) {
        case "H2": this_level = 2; break;
        case "H3": this_level = 3; break;
        case "H4": this_level = 4; break;
        case "H5": this_level = 5; break;
        default:   this_level = 0;
    }

    //console.log(this_enum_elt);

    // increment index, reset those below
    // so if we see an h2, bump up the h2 index, reset h3/h4/h5 to 0
    reset_below(this_level);
    incr(this_level);

    // "Foo Bar" -> "1.3.4. Foo Bar"
    let old_section_title = this_enum_elt.innerText;
    let new_section_title = str_idx(this_level) + ". " + this_enum_elt.innerText;

    this_enum_elt.innerText = new_section_title;

    //console.log(new_section_title);
    let entry_a = document.createElement('a');

    // make an id for this entry if it doesn't exist
    if (!this_enum_elt.id) {
        // "Foo Bar" -> "foo-bar"
        let words = old_section_title.split(" ");
        let ident = words.map(function (s) { return s.toLowerCase(); }).join("-");
        this_enum_elt.id = ident;
    }

    entry_a.href = "#" + this_enum_elt.id;
    entry_a.innerText = new_section_title;
    entry_a.classList += "toc" + this_level;

    //console.log(entry_a);
    let entry_br = document.createElement('br');

    toc.appendChild(entry_a);
    toc.appendChild(entry_br);
}