// Kyler Olsen
// November 2023

class PythonEditor{
    constructor(ele) {
        this.element = ele;

        this.element.addEventListener("input", this.textInput.bind(this));
        this.element.addEventListener("keydown", this.handleKeyDown.bind(this));

        this.view_code = document.createElement("code");
        this.edit_code = document.createElement("code");
        this.view_pre = document.createElement("pre");
        this.edit_pre = document.createElement("pre");

        this.edit_code.contentEditable = true;
        this.edit_code.spellcheck = false;
        this.view_pre.classList.add("view-code");
        this.edit_pre.classList.add("edit-code");

        this.view_pre.appendChild(this.view_code);
        this.edit_pre.appendChild(this.edit_code);
        this.element.appendChild(this.view_pre);
        this.element.appendChild(this.edit_pre);
    }

    textInput(e) {
        let text = this.edit_code.innerHTML;
        syntax_highlight(text).forEach(ele => this.view_code.appendChild(ele));
    }

    handleKeyDown(e) {
        if (e.key === "Tab") {
            e.preventDefault();
            insertTab(e.target);
        }
    }
}

function insertTab() {
    const selection = window.getSelection();

    if (selection.rangeCount > 0) {
        const range = selection.getRangeAt(0);
        const startOffset = range.startOffset;
        const lineStart = range.startContainer.textContent.lastIndexOf('\n', startOffset - 1) + 1;
        const spacesToAdd = 4 - ((startOffset - lineStart) % 4);
        const tabSpaces = ' '.repeat(spacesToAdd);

        const tabNode = document.createTextNode(tabSpaces);
        range.deleteContents();
        range.insertNode(tabNode);
        range.setStartAfter(tabNode);
        range.setEndAfter(tabNode);
        selection.removeAllRanges();
        selection.addRange(range);
    }
}

function syntax_highlight(text) {
    const whitespace = " \n\t";
    const string_start = `'"`;

    const elements = [];
    var char = text.substr(0, 1); text = text.substr(1);

    while (text.length) {
        const element = document.createElement("span");
        var token_type = "";

        if (whitespace.includes(char))
            token_type = "whitespace";
        else if (string_start.includes(char))
            token_type = "string";

        while (text.length) {
            if (token_type == "whitespace" && !whitespace.includes(char))
                break;
            element.innerText.concat(char);
            char = text.substr(0, 1); text = text.substr(1);
        }

        elements.push(element);
    }

    return elements;
}

document.addEventListener('DOMContentLoaded', () => {
    document.querySelectorAll(".code").forEach(ele => new PythonEditor(ele))
});