// Initiating variables
const length = pretext.current.length+1;
let cursorPosition = 0;
let cursorYOffset = 7;
let history = { index: 0, list: [] };

// Initiating constants
const tbDiv = document.getElementById("textbox");
const textIn = document.getElementById("input");
const textCur = document.getElementById("current");
const cursor = document.getElementById("cursor");
// Set initial pretext
const pretextElement = document.createElement('a');
pretextElement.innerHTML = pretext.original;
tbDiv.insertBefore(pretextElement, tbDiv.children[1]);
// Initial cursor offset
cursor.style.transform = `translate(${length-1}ch,${2.222*7-0.4}ch)`;

// Handle user input
textIn.oninput = () => {
    const text = textCur.textContent;
    // If cursor at end of text
    if (cursorPosition === text.length)
        textCur.textContent += textIn.value;
    else {
        // Insert input at cursor position
        const left = text.substring(0, cursorPosition);
        const right = text.substring(cursorPosition, text.length);
        textCur.textContent = left + textIn.value + right;
    }
    // Increment by input length
    cursorPosition += textIn.value.length;
    textIn.value = "";
    updateCursor();
};
// Autofocus on start
textIn.focus();

// Key Listener
document.addEventListener("keydown", e => {
    const text = textCur.textContent;
    switch (e.key) {
        case "Backspace":
            // Delete one character to the left
            if (cursorPosition === 0)
                return;
            // Cursor is in the middle of the input
            if (cursorPosition <= textCur.textContent.length-1) {
                const a = text.substring(0, cursorPosition-1);
                const b = text.substring(cursorPosition, text.length);
                textCur.textContent=a+b;
            // Cursor is at the end of input
            } else
                textCur.textContent = text.substring(0,text.length-1);
            // Update cursor visuals
            cursorPosition--;
            updateCursor();
            break;
        case "ArrowLeft":
            // Go one cursor position to the left
            if (cursorPosition > 0) {
                cursorPosition--;
                updateCursor();
            }
            break;
        case "ArrowRight":
            // Go one cursor position to the right
            if (cursorPosition < textCur.textContent.length) {
                cursorPosition++;
                updateCursor();
            }
            break;
        case "Delete":
            // Delete one character to the left
            if (cursorPosition >= textCur.textContent.length)
                return;
            // No input given yet
            if (textCur.textContent.length === 0)
                return;
            const a = text.substring(0, cursorPosition);
            const b = text.substring(cursorPosition+1, text.length);
            textCur.textContent = a+b;
            break;
        case "Enter":
            // Send out command / line break
            outputText({user: text});
            // Refocus
            textIn.focus();
            break;
        case "ArrowUp":
            // Go back one command in the history
            if (history.index > 0) {
                history.index--;
                textCur.textContent = history.list[history.index];
                cursorPosition = textCur.textContent.length;
            }
            // Update cursor position
            updateCursor();
            break;
        case "ArrowDown":
            // Go forward one command in the history
            if (history.index < history.list.length-1) {
                history.index++;
                textCur.textContent = history.list[history.index];
                cursorPosition = textCur.textContent.length;
            // Reached end of history
            } else if (history.index < history.list.length) {
                history.index++;
                textCur.textContent = "";
                cursorPosition = 0;
            }
            // Update cursor position
            updateCursor();
            break;
        case "Tab":
            // Auto complete
            break;
    }
});

// Text output or user input handler
function outputText(params) {
    // Unpack parameters
    const { user, output, preNext } = params;

    // Temporarily remove core elements
    tbDiv.removeChild(textIn);
    tbDiv.removeChild(textCur);

    let inputSet, whitespaceOnly = false;
    if (user !== undefined) {
        // Save input into history if it's not empty
        inputSet = new Set(user.split(''));
        whitespaceOnly = inputSet.has(" ") && inputSet.size === 1;
        if (user !== "" && !whitespaceOnly) {
            history.list.push(user);
            history.index = history.list.length;
        }

        // Fixate current input to page
        tbDiv.appendChild(createText(user));
        tbDiv.innerHTML += `<br>`;
        cursorYOffset++;
    }

    // Replace text on last pretext
    if (preNext !== undefined) {
        const tbc = tbDiv.children;
        tbc[tbc.length - 1].innerHTML = preNext;
    }

    // Run as command if it's user input and display output
    const isUserInput = output === undefined && user !== undefined;
    let commandOutput = (isUserInput && !whitespaceOnly) ? runCommand(user) : (output ? output : "");
    if (commandOutput !== "" && commandOutput !== null) {
        // If output is given, display it as text with formatting
        tbDiv.append(createText(commandOutput, false))
        tbDiv.innerHTML += `<br>`;
        // Offset cursor by at least one line, and as many more as there are line breaks
        cursorYOffset += commandOutput.split("<br>").length;
    }

    // Add new pretext to terminal
    if (commandOutput !== null) {
        const prelink = document.createElement('a');
        prelink.innerHTML = pretext.current;
        tbDiv.appendChild(prelink);
    }

    // Add core elements back on top of div
    tbDiv.appendChild(textCur);
    tbDiv.appendChild(textIn);

    // Reset variables and position cursor
    if (isUserInput) {
        textCur.textContent = "";
        cursorPosition = 0;
    }
    updateCursor();
}

// Create an 'a' element with input string as its contents
function createText(str, safe=true) {
    const link = document.createElement("a");
    link.style.color = "lightgrey";
    link.style.whiteSpace = "pre";
    // No "HTML injection"
    if (safe)
        link.textContent = str;
    // "Anything goes" and keep formatting
    else
        link.innerHTML = str;
    return link;
}

// Rename last-posted pretext to own username
function renameToSelf() {
    const tbc = tbDiv.children;
    tbc[tbc.length - 3].innerHTML = `${window.localStorage.getItem("name")}#${window.localStorage.getItem("id")}: `;
}

// Update cursor position based on coordinates
function updateCursor() {
    let cursor = document.getElementById("cursor");
    cursor.style.transform = `translate(${pretext.current.length+cursorPosition}ch, ${2.222*cursorYOffset-0.4}ch)`;
}

// Toggle cursor visibility
setInterval(()=>{
    cursor.style.opacity = !parseInt(cursor.style.opacity)+0;
},1000);