Managing Discrete Character Animation States

Question

I'm creating a 2D game in which each possible direction of movement for the player, (Up, Down, Left, Right), has its own distinct animation, i.e., they aren't rotations of each other. Currently I am using a FSM design to manage this, but its getting messy already, and I know it will only get worse.

For example: (in Lua)

StateComponent = {
    states = {
        walking_left = {set_animation("walking_left")},
        walking_right = {set_animation("walking_right")},
        ...
    }
},

Now say I want to add attacking, the collection of states then becomes:

StateComponent = {
    states = {
        walking_left = {set_animation("walking_left")},
        walking_right = {set_animation("walking_right")},
        ...

        attacking_left = {...},
        attacking_right = {...},
        ...
    }
},

Okay, but now what about opening up a chest from each different side... This quickly becomes very complex. I read about a using a Behavior Tree, but it doesn't seem to support the discrete division of states necessary for having a different animation for walking/attacking/etc in each cardinal direction. What kind of design would be elegant and scalable for this problem? Or how else might I represent these states?

Answer 1

Since you asked to expand on my first part, here it is.

Currently, under states you save all your states, regardless of the relation between them, but we can clearly see that you can group them up to make it more organized.

So, this:

StateComponent = {
    states = {
        walking_left = {set_animation("walking_left")},
        walking_right = {set_animation("walking_right")},
        ...

        attacking_left = {...},
        attacking_right = {...},
        ...
    }
},

Becomes this:

StateComponent = {
    states = {
        walking = {
             left = {set_animation("walking_left")},
             right = {set_animation("walking_right")},
        }, 
        ...

        attacking = {
            left = { ... },
            right = { ...},
        }
        ....
    }
},

And then you would save two states in your code: state type and state direction (maybe word it a bit differently).

And then, you'd set the state by stats[type][direction] or something like that