function parseIRCMessage(line) {
  line = line.replace(/\r?\n$/, '');
  let tags = {};
  let prefix = null;
  let nick = null;
  let command = null;
  const params = [];

  // tags
  if (line[0] === '@') {
    const end = line.indexOf(' ');
    const rawTags = line.slice(1, end);
    for (const tag of rawTags.split(';')) {
      const [k, v = true] = tag.split('=');
      tags[k] = v === true ? true : v;
    }
    line = line.slice(end + 1);
  }

  // prefix
  if (line[0] === ':') {
    const end = line.indexOf(' ');
    prefix = line.slice(1, end);
    const bang = prefix.indexOf('!');
    if (bang !== -1) nick = prefix.slice(0, bang);
    line = line.slice(end + 1);
  }

  // command and params
  const parts = line.split(' ');
  command = parts.shift();
  for (let i = 0; i < parts.length; i++) {
    if (parts[i][0] === ':') {
      params.push(parts.slice(i).join(' ').slice(1));
      break;
    }
    if (parts[i].length) params.push(parts[i]);
  }

  return { tags, prefix, nick, command, params };
}

function displayMessage(data) {
    const messages = document.getElementById("window-messages");
    
    const message = document.createElement("p");
    message.classList.add("message");
    
    if ("nick" in data && data.nick.length > 0) {
        const nickElement = document.createElement("span");
        nickElement.classList.add("nick");
        nickElement.textContent = `${data.nick}: `;
        
        if ("color" in data.tags) {
            nickElement.style.color = data.tags["color"];
        }
        
        message.append(nickElement);
    }
    
    const messageContent = document.createElement("span");
    messageContent.classList.add("content");
    messageContent.textContent = data.params[1];
    message.append(messageContent);
    
    messages.append(message);
}

function displaySystemMessage(channelName, message, nick = "System") {
    displayMessage({
        "nick": nick,
        "prefix": nick,
        "command": "PRIVMSG",
        "params": [channelName, message],
        "tags": {}
    });
}

class TwitchIRCClient {
    constructor (host, nick, pass) {
        this.joinedChannels = [];
        this.socket = null;
        this.host = host;
        this.nick = nick;
        this.pass = pass;
    }
    
    connect() {
        this.socket = new WebSocket(this.host);
        
        this.socket.addEventListener("open", () => {
            this.socket.send(`NICK ${this.nick}`);
            this.socket.send(`PASS ${this.pass}`);
            this.socket.send(`CAP REQ :twitch.tv/tags twitch.tv/membership`);
        });
        
        this.socket.addEventListener("message", (e) => {
            const lines = e.data.split("\r\n");
            for (const line of lines) {
                if (line.trim().length == 0) {
                    continue;
                }
                
                const msg = parseIRCMessage(line);
                
                switch (msg.command) {
                    case "001": {
                        for (const c of this.joinedChannels) {
                            this.join(c);
                        }
                        displaySystemMessage("*", "Connected!");
                        break;
                    }
                    case "PRIVMSG": {
                        displayMessage(msg);
                    }
                    default: break;
                }
            }
        });
        
        this.socket.addEventListener("error", (e) => {
            console.error(e);
        });
        
        this.socket.addEventListener("close", (e) => {
            for (const c of this.joinedChannels) {
                displaySystemMessage(c, `Disconnected! Reason: ${e.reason}`);
                displaySystemMessage(c, "Reconnecting in 10 seconds...");
            }
            
            setTimeout(() => this.connect(), 10000);
        });
    }
    
    say(channelName, message) {
        this.socket.send(`PRIVMSG #${channelName} :${message}`);
    }
    
    join(channelName) {
        if (this.socket != null && this.socket.readyState == this.socket.OPEN) {
            this.socket.send(`JOIN #${channelName}`);
        }
        
        if (!this.joinedChannels.includes(channelName)) {
            this.joinedChannels.push(channelName);
        }
    }
}