Bukkit

Want to change something inside Legendchat? Or stop a player from receiving a message? Or cancel a message from being sent? Okay! You can do!
PS: I really recommend you to read "Set a value to a tag". It could be useful.

ChatMessageEvent

Event called when someone say something in the chat (but not the bungeecord channel).
List of methods available:

PrivateMessageEvent

Event called when a private message is sent.
List of methods available:

BungeecordChatMessageEvent

Event called when a chat message is sent through the bungeecord channel.
The methods inside this event is the same as ChatMessageEvent, excluding getSender(), setSender() and getBukkitFormat().
You can get the Sender's name inside the tag 'sender' or 'plainsender'.
Observation: Message flow when someone sent a bungeecord message:
Player say in channel => ChatMessageEvent (sender server) => Send message to BungeeCord => BungeeCord send message to other servers => BungeecordChatMessageEvent (others servers) => Other players receive the message

You can change other things inside Legendchat.
To hook with Legendchat you just need to use Legendchat.
Example:

public void onEnable() {
    ChannelManager channelManager = Legendchat.getChannelManager();
}

List of methods (I will list what manager do what):

ChannelManager

Contains: All channels.
Methods to: Create, delete and get channels.

PlayerManager

Contains: Player's channels, spies and hidden players.
Methods to: Get and change player channel, get and set spies, get and set hidden players.

MessageManager

Contains: All loaded messages.
Methods to: Get a message.

IgnoreManager

Contains: All ignored players and who ignored.
Methods to: Get and set players to ignore others.

PrivateMessageManager

Contains: All methods to send and change the private message system.
Methods to: Send private messages, reply private messages, start and stop chats.

DelayManager

Contains: All methods to change delays.
Methods to: Add, remove and get delays (the delay is per channel).

MuteManager

Contains: All methods to change muted player and muted server.
Methods to: Add, remove and get muted players and change muted server state.

CensorManager

Contains: All methods to censor functions.
Methods to: Add, remove and get censored words.

TemporaryChannelManager

Contains: All methods to temporary channels.
Methods to: Add, remove and get temporary channels.

ConfigManager

Contains: All methods to access others config files.
Methods to: Read config files.

LogManager

Contains: All methods to log messages.
Methods to: Manage the message cache.

AfkManager

Contains: All methods to afk managing.
Methods to: Add, remove and set afk reasons.

Block a message containg something

@EventHandler
private void onChat(ChatMessageEvent e) {
    if(e.getMessage().contains("something"))
        e.setCancelled(true);
}

Block someone from receiving messages

@EventHandler
private void onChat(ChatMessageEvent e) {
    if(e.getRecipients().contains(player))
        e.getRecipients().remove(player);
}

Set a value to a tag

//Observation: the channel format (config.yml) must contains {mytag}
//Like others prefixes ({prefix}, {suffix}, ...)
@EventHandler
private void onChat(ChatMessageEvent e) {
    if(e.getTags().contains("mytag"))
        e.setTagValue("mytag","&6[MyTag] ");
}

Unmute a player

public void myMethod(Player p) {
    MuteManager mm = Legendchat.getMuteManager();
    if(mm.isPlayerMuted(p.getName()))
        mm.unmutePlayer(p.getName());
}

Change player channel

public void myMethod(Player p, String ch_name) {
    Channel c = Legendchat.getChannelManager().getChannelByName(ch_name);
    Legendchat.getPlayerManager().setPlayerChannel(p,c,/*send message?*/ true);
}

Unmute server

public void myMethod() {
    Legendchat.getMuteManager().unmuteServer();
}