// Run input as command if possible
function runCommand(input) {
    // Return on no input
    if (input === "")
        return "";

    if (input.toLowerCase().startsWith("exit")) {
        cmd_exit();
        return;
    }

    const modeSplit = chatMode.split(' ');
    switch (modeSplit[0]) {
        case "msg":
            directMessage(modeSplit[1], input)
            return "";
        // case "chat":
        //     // Global messages
        //     return "";
    }

    let output = "";
    const lowerIn = input.toLowerCase();

    // Go through properties of window
    for (const func in window) {
        const splits = func.split("cmd_");
        // If property is prefixed with 'cmd_' (a 'command', so an executable function)
        if (splits.length === 2) {
            const name = splits[1];
            const lowerNm = name.toLowerCase();
            // If command is called without parameters
            if (lowerIn === lowerNm) {
                output = window[func]();
                break;
                // If command is called with parameters
            } else if (lowerIn.startsWith(lowerNm + " ")) {
                // Parameters always follow the command name after first space
                const params = input.split(" ").filter((e,i)=>i!==0);
                output = window[func](params);
                break;
            }
        }
    }

    // Standard output:
    if (output === "")
        output = `${input.split(" ")[0]}: command not found`;
    if (output === undefined)
        output = "";

    // Return command output
    return output;
}

function directMessage(name, message) {
    // Direct message
    fetch('/message', {
        method: 'POST',
        headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json'
        },
        body: JSON.stringify({
            id: user.id,
            message,
            name
        })
    }).then(res => {});
}

// function globalMessage(message) {}

function cmd_help() {
    // Display 'help' message
    return "Commands list:<br>" +
        "   -about    Information about this website<br>"+
        "   -clear    Clear terminal screen<br>" +
        "   -history  Displays the command history of this session<br>" +
        "   -exec     Execute arbitrary math and logic equations";
}

function cmd_about() {
    // Display 'about' message
    return "This website is based on the general idea and design of a terminal.<br>" +
        "It serves the purpose of a homepage. It exists just for the fun of creating it.";
}

function cmd_clear() {
    // Clear terminal by reloading page
    window.location.reload();
}

function cmd_history() {
    // Display the command history line by line
    let output = "";

    const hl = history.list;
    for (let i = 0; i < hl.length; i++) {
        const lineBreak = (i !== hl.length - 1) ? "<br>" : "";
        output += `${i+1} ${hl[i]}${lineBreak}`;
    }

    return output;
}

function cmd_exec(input) {
    // No input was given
    if (input === undefined)
        return "You must enter parameters!";
    // Input contains letters or invalid characters
    const str = input.join(' ');
    if (/[',:;a-zA-Z]/.test(str) || str === "")
        return "Invalid input!";
    // Input is inside of character range with exceptions
    const chars = str.split('').filter(e => {
        const code = e.charCodeAt(0);
        const s = code ===  32;
        const a = code >    36;
        const b = code <    63;
        const c = code ===  94;
        const d = code === 124;
        return !(s || a && b || c || d);
    });
    // If exceptions remain, invalid input was given
    if (chars.length > 0)
        return "Invalid input!";
    // Execute input and return output
    return eval(str).toString();
}

function cmd_echo(input) {
    if (input === undefined)
        return " ";
    return input.join(' ');
}

function cmd_nick(input) {
    if (input === undefined)
        return "No nickname was given!";
    user.name = input[0];
    fetch('/nickname', {
        method: 'POST',
        headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json'
        },
        body: JSON.stringify({
            name: user.name,
            id: user.id
        })
    }).then(res => {
        if (res.status === 200)
            return res.json();
    }).then(res => {
        if (res === undefined)
            return;
        if (res.success)
            outputText({output: `Applied name '${user.name}'.`});
        else {
            outputText({output: `Name '${user.name}' is already taken!`});
            user.name = "";
        }
    });
    return null;
}

function cmd_msg(input) {
    if (input === undefined)
        return "No recipient was given!";
    if (!user.connected)
        return "You are not connected!";
    if (user.name === "")
        return "You do not have a name!";
    const username = input[0];
    pretext.current = `Chat (${username})> `;
    chatMode = `msg ${username}`;
    user.chatPull = setInterval(() => {
        fetch('/getChat', {
            method: 'POST',
            headers: {
                'Accept': 'application/json',
                'Content-Type': 'application/json'
            },
            body: JSON.stringify({
                id: user.id
            })
        }).then(res => {
            if (res.status === 200)
                return res.json();
            else if (res.status === 100)
                return;
            cmd_exit();
            outputText({output: "Error occurred while fetching messages!"});
        }).then(res => {
            if (res === undefined)
                return;
            console.log(res);
            for (const user in res)
                for (const msg of res[user])
                    outputText({output: msg});
        });
    }, 500);
}

function cmd_exit() {
    const level = chatMode.split(' ')[0];
    if (level === "default")
        return "Already at top-level!";

    chatMode = "default";
    pretext.current = pretext.original;
    switch (level) {
        // case "chat":
        case "msg":
            clearInterval(user.chatPull);
            break;
    }
}