Swizzling, dynamic instance methods

vec3i.coffee

Function::property = (prop, desc) ->
    Object.defineProperty @prototype, prop, desc

arrayExcept = (arr, idx) ->
    res = arr[0..]
    res.splice idx, 1
    res

combine = (str) ->
    fn = (active, rest, a) ->
        if !active && !rest
            return
        if !rest
            a.push active
        else
            fn(active + rest[0], rest.slice(1), a)
            fn(active, rest.slice(1), a)
        a
    fn("", str, [])

permute = (arr) ->
    arr = Array::slice.call arr, 0
    return [[]] if arr.length == 0
 
    permutations = (for value,idx in arr
        [value].concat perm for perm in permute arrayExcept arr, idx)
 
    [].concat permutations...

perm_comb = (input) ->
    result = []
    combine(input).map((c) -> permute(c))
        .forEach (cp) ->
            cp.forEach (accessor) ->
                result.push accessor.join('')
    result

typed_concat = (type, a, b) ->
    alen = a.length
    result = new type(alen + b.length)
    result.set(a)
    result.set(b, alen)
    result


class vec2i
    X = 0
    Y = 1
    SIZE = 2
    PREALLOCATE = 50
    
    TYPE = Int32Array
    DATA = new TYPE()
    NREF = 0
    
    @ensure_capacity: ->
        if DATA.length < NREF * SIZE
            DATA = typed_concat(TYPE, DATA, new TYPE(PREALLOCATE * SIZE))
    
    constructor: (x, y) ->
        @offset = NREF * SIZE
        NREF += 1
        
        @constructor.ensure_capacity()
        @x = x
        @y = y
 
    @property 'x',
        get: -> DATA[@offset + X]
        set: (x) -> DATA[@offset + X] = x
    @property 'y',
        get: -> DATA[@offset + Y]
        set: (y) -> DATA[@offset + Y] = y

    perm_comb('xy').forEach (els) ->
        if els.length > 1
            vec2i::constructor.property els,
                get: -> new vec2i(
                    @__lookupGetter__(els[0])(),
                    @__lookupGetter__(els[1])())

    toString: ->
        "vec2i(" + @x + "," + @y + ")"

 
class vec3i
    X = 0
    Y = 1
    Z = 2
    SIZE = 3
    PREALLOCATE = 50
    
    TYPE = Int32Array
    DATA = new TYPE()
    NREF = 0
    
    @ensure_capacity: ->
        if DATA.length < NREF * SIZE
            DATA = typed_concat(TYPE, DATA, new TYPE(PREALLOCATE * SIZE))

    constructor: (x, y, z) ->
        @offset = NREF * SIZE
        NREF += 1
        
        @constructor.ensure_capacity()
        @x = x
        @y = y
        @z = z
 
    @property 'x',
        get: -> DATA[@offset + X]
        set: (x) -> DATA[@offset + X] = x
    @property 'y',
        get: -> DATA[@offset + Y]
        set: (y) -> DATA[@offset + Y] = y
    @property 'z',
        get: -> DATA[@offset + Z]
        set: (z) -> DATA[@offset + Z] = z

    perm_comb('xyz').forEach (els) ->
        if els.length == 3
           type = vec3i
        else if els.length == 2
           type = vec2i
        else
            return
        vec3i::constructor.property els,
            get: -> new type(els.split('').map((c) => @__lookupGetter__(c)())...)

    toString: ->
        "vec3i(" + @x + "," + @y + "," + @z + ")"
 

console.log(new vec3i(1,2,3).zyx + '')