--require("math.quat")
--require("math.vec3")

Transform = { translation = Vec3.ZERO, rotation = Quat.IDENTITY, scale = Vec3.ONE }
Transform.__index = Transform
Transform.__name = "Transform"

function Transform:new(translation, rotation, scale)
    local t = {}
    setmetatable(t, Transform)
    
    t.translation = translation
    t.rotation = rotation
    t.scale = scale
    
    return t
end

function Transform:copy()
    return Transform:new(self.translation:copy(), self.rotation:copy(), self.scale:copy())
end

--- Creates a new Transform with the translation at the vec3
--- @param pos Vec3
function Transform:from_vec3(pos)
    local t = Transform:copy() -- copy of default transform
    t.translation = pos
    return t
end

function Transform:from_xyz(x, y, z)
    Transform:from_vec3(Vec3:new(x, y, z))
end

--- Calculates the forward vector of the Transform.
--- @return Vec3
function Transform:forward()
    return (self.rotation * Vec3.NEG_Z):normalize()
end

--- Calculates the left vector of the Transform.
--- @return Vec3
function Transform:left()
    return (self.rotation * Vec3.X):normalize()
end

--- Calculates the up vector of the Transform.
--- @return Vec3
function Transform:up()
    return (self.rotation * Vec3.Y):normalize()
end

--- Rotates `self` using a Quaternion
--- @param quat Quat
function Transform:rotate(quat)
    self.rotation = (quat * self.rotation):normalize()
end

--- Rotates `self` around the x-axis
--- @param rad number
function Transform:rotate_x(rad)
    self:rotate(Quat:from_rotation_x(rad))
end

--- Rotates `self` around the y-axis
--- @param rad number
function Transform:rotate_y(rad)
    self:rotate(Quat:from_rotation_y(rad))
end

--- Rotates `self` around the z-axis
--- @param rad number
function Transform:rotate_z(rad)
    self:rotate(Quat:from_rotation_z(rad))
end

--- Calculates the linear iterpolation between `self` and `rhs` based on the `alpha`.
--- When `alpha` is `0`, the result will be equal to `self`. When `s` is `1`, the result
--- will be equal to `rhs`
--- @param rhs Transform
--- @param alpha number
--- @return Transform
function Transform:lerp(rhs, alpha)
    local res = self:copy()
    res.translation = self.translation:lerp(rhs.translation, alpha)
    res.rotation = self.rotation:lerp(rhs.rotation, alpha)
    res.scale = self.scale:lerp(rhs.scale, alpha)
    return res
end

function Transform:__tostring()
    return "Transform(pos=" .. tostring(self.translation) .. ", rot="
        .. tostring(self.rotation) .. ", scale=" .. tostring(self.scale) .. ")"
end