roll20 follow v2

gistfile1.txt

/**
 * A script with a command for specifying tokens to follow other tokens.
 * Simply select the tokens in the marching order and enter the "!follow" 
 * commandwith either a direction for the marching order of the selected tokens 
 * or the name of a token for the selected tokens to follow behind.
 * 
 * E.G. "!follow west" will make the selected tokens follow each other in order
 * from east to west, with the westmost token being the leader and the eastmost 
 * token being the caboose.
 * Alternatively if we want the selected tokens to follow a character named 
 * "Drizt", enter the command "!follow Drizt".
 * 
 * !follow [north|south|east|west|name of leader token]
 * 
 * To make a token stop following the token in front of it, just manually move
 * the token anywhere.
 */


/** Helper function: Makes one token follow another token. */
var _followCmd = function(leader, follower) {
    
    if(!leader || !follower) {
        return;
    }
    
    // unbind all of cur's following links.
    _unfollowCmd(follower);
    
    var prevFollower = leader.follower;
    follower.leader = leader;
    follower.follower = prevFollower;
    
    leader.follower = follower;
    if(prevFollower) {
        prevFollower.leader = follower;
    }
    
}


/** 
 * Helper method for making a character token stop following another token 
 * and stopped being followed by another token. 
 */
var _unfollowCmd = function(token) {
    if(token.leader) {
        token.leader.follower = token.follower;
    }
    if(token.follower) {
        token.follower.leader = token.leader;
    }
    
    token.leader = null;
    token.follower = null;
}


/** Interpret the chat commands. */
on("chat:message", function(msg) {
    var cmdName;
    var msgTxt;
    
    if(!msg.selected || msg.selected.length == 0) {
        return;
    }
    
    cmdName = "!follow";
    msgTxt = msg.content;
    if(msg.type == "api" && msgTxt.indexOf(cmdName) !== -1) {
        var curPageID = Campaign().get("playerpageid");
        
        // A direction can be given for the marching order since 
        // the msg.selected array is in no particular order.
        var direction;
        if(msgTxt.indexOf("north") !== -1) {
            direction = "north";
        }
        else if(msgTxt.indexOf("south") !== -1) {
            direction = "south";
        }
        else if(msgTxt.indexOf("west") !== -1) {
            direction = "west";
        }
        else if(msgTxt.indexOf("east") !== -1) {
            direction = "east";
        }
        
        // Get the tokens for the selected objects.
        var selected = msg.selected;
        var marchingOrder = [];
        for(var i=0; i<selected.length; i++) {
          var token = findObjs({
              _id: selected[i]._id, 
              _pageid: curPageID
          })[0];
          marchingOrder.push(token);
        }
        
        // Sort the marching order in the specified direction.
        if(direction !== undefined) {
            marchingOrder.sort(function(a,b) {
                var aX = parseFloat(a.get("left"));
                var bX = parseFloat(b.get("left"));
                var aY = parseFloat(a.get("top"));
                var bY = parseFloat(b.get("top"));
                
                if(direction === "north") {
                    return (aY - bY);
                }
                else if(direction === "south") {
                    return (bY - aY);
                }
                else if(direction === "west") {
                    return (aX - bX);
                }
                else {
                    return (bX - aX);
                }
            });
        }
        
        // Alternatively, we can tell the tokens to follow a character given
        // by name.
        else {
            var leader = findObjs({
                name: msgTxt.substr(cmdName.length+1),
                _pageid: curPageID
            })[0];
            
            if(leader === undefined) {
                var playerName = msg.who;
                if(playerName.indexOf(" ") !== -1) {
                    playerName = playerName.substring(0, playerName.indexOf(" "));
                }
                sendChat("A mysterious voice", "/w " + playerName + " Invalid " +
                "command. After the command enter either north, south," +
                " east, or west for the direction of the marching order, " + 
                "or the name of a character to follow.");
                return;
            }
            else {
                marchingOrder.unshift(leader);
            }
        }
        
        // Set up the marching order from leader to caboose.
        for(var i=0; i<marchingOrder.length - 1; i++) {
          var leader = marchingOrder[i];
          var follower = marchingOrder[i+1];
          
          sendChat("", follower.get("name") + " is following " + leader.get("name"));
          _followCmd(leader, follower);
        }
    }
});


/** Do the marching order effect when the leader tokens move! */
on("change:graphic", function(obj, prev) {
    var leader = obj;
    var follower = leader.follower;
    leader.prevLeft = prev["left"];
    leader.prevTop = prev["top"];
    leader.prevRotation = prev["rotation"];
   
   // Only move the followers if there was a change in either the leader's 
   // left or top attributes.
   if(leader.get("left") == leader.prevLeft && leader.get("top") == leader.prevTop) {
       return;
   }
   
    // We stepped out of line. Stop following the guy in front of us.
    if(leader.leader) {
        _unfollowCmd(leader);
    }
   
   // move everyone to the previous position of the token in front of them.
    while(follower) {
        follower.prevLeft = follower.get("left");
        follower.prevTop = follower.get("top");
        follower.prevRotation = follower.get("rotation")
        
        follower.set("left",leader.prevLeft);
        follower.set("top",leader.prevTop);
        follower.set("rotation", leader.prevRotation);
        
        leader = follower;
        follower = follower.follower;
        
        // avoid cycles.
        if(follower == obj) {
           return;
        }
    }
    
});