love2d rope physics

Rope = {}
Rope.__index = Rope

--[[
Basic Usage:
    local Rope = require 'rope'

    .load()
        Rope:load()
        Rope:createRope()
        Rope:attachToObject(body_to_attach{body, shape, fixture)

    .update()
        Rope:update()

    .draw()
        Rope:draw()

    Uses key q and e to handle rope length
--]]

function Rope:load()
    rope = {
        x = 300,
        y = 100,
        segmentLength = 5,
        maxLength = 5, -- length between joints
        segmentCount = 20,
        minLength = 4,
        attachedObject = nil
    }
    setmetatable(rope, Rope)
    return rope
end

local delay = 0.09 -- rope extension delay
local timer = 0
function Rope:update(dt)
    Rope:fixRopePosition()
    timer = timer + dt

    -- Add a segment
    if love.keyboard.isDown("e") and timer > delay then
        timer = 0
        print("Current rope length:" , #ropeSegments)
        rope.segmentCount = rope.segmentCount + 1

        -- Remove the first joint
        if not rope.mainJoint:isDestroyed() then
            rope.mainJoint:destroy()
        end

        -- Create new segment then attach to the object
        local newY = ropeSegments[1].body:getY() + 10
        local newX = ropeSegments[1].body:getX()
        newSegment = Rope:createRopeSegment(newX, newY)
        local joint = Rope:connectRopeSegment(ropeSegments[1].body, newSegment.body)
        table.insert(ropeSegments, 1, newSegment)
        table.insert(ropeJoints, 1, joint)

        if rope.attachedObject then
            rope.mainJoint = Rope:attachToObject(rope.attachedObject)
        end

    -- Remove a segment
    elseif love.keyboard.isDown("q") and timer > delay then
        timer = 0
        print("Current rope length:", #ropeSegments)
        rope.segmentCount = rope.segmentCount - 1

        if #ropeJoints == rope.minLength then return end

        -- Remove the first joint and segment then attach to the object
        joint_to_delete = table.remove(ropeJoints, 1)
        joint_to_delete:destroy()
        first = ropeSegments[1]
        first.body:destroy()

        table.remove(ropeSegments, 1)

        if rope.attachedObject then
            rope.mainJoint = Rope:attachToObject(rope.attachedObject)
        end

    end
end

function Rope:removeSegment()
    if ropeSegments > 1 then
        local joint_to_delete = table.remove(ropeJoints, #ropeJoints)
        joint_to_delete:destroy()

        local segment_to_delete = table.remove(ropeSegments, #ropeSegments)
        segment_to_delete.body:destroy()
    end
end

function Rope:unDockHookObject()
   if hook.dockJoint and hook.docking then
       hook.dockJoint:destroy()
       hook.docking = false
       hook.dockJoint = nil
   end
end

function Rope:dockHookObject()
    if hook.readyToDock then
        hook.dockJoint = love.physics.newRevoluteJoint(
            hook.body,
            hook.contactBody,
            hook.body:getX(),
            hook.body:getY(), false
        )
        hook.readyToDock = false
        hook.docking = true
    end
end

function Rope:mousepressed(key)
    if key == 1 then -- left click
        Rope:toggleHook()
    end
end

function Rope:toggleHook()
    if hook.docking then
       print("Undocking..")
       Rope:unDockHookObject()
    elseif hook.readyToDock then
       print("Docking Object to Rope Hook")
       Rope:dockHookObject()
    end
end

function Rope:createRopeSegment(x, y)
    newSegment = {}
    newSegment.body = love.physics.newBody(world, x, y, "dynamic")
    newSegment.shape = love.physics.newCircleShape(5)
    newSegment.fixture = love.physics.newFixture(newSegment.body, newSegment.shape, 0.2)
    newSegment.body:setLinearDamping(2)
    return newSegment
end

function Rope:connectRopeSegment(segmentA, segmentB)
    local joint = love.physics.newRopeJoint(
        segmentA,        segmentB,
        segmentA:getX(), segmentA:getY(),
        segmentB:getX(), segmentB:getY(),
        rope.maxLength,
        false
    )
    return joint
end

function Rope:attachToObject(object)
    firstSegment = ropeSegments[1]
    newJoint = love.physics.newRopeJoint(
        firstSegment.body, object.body,
        firstSegment.body:getX(), firstSegment.body:getY(),
        object.body:getX(), object.body:getY()+10,
        10
    )
    rope.attachedObject = object
    return newJoint
end

function Rope:createRope()
    ropeSegments = {}
    ropeJoints = {}

    -- create all the segments
    for segment = 1, rope.segmentCount do
        newSegment = Rope:createRopeSegment(rope.x, rope.y + (segment - 1) * rope.segmentLength)
        table.insert(ropeSegments, {
            body = newSegment.body,
            shape = newSegment.shape,
            fixture = newSegment.fixture
        })
    end

    -- connect all segments
    for segment = 1, #ropeSegments - 1 do
        local bodyA = ropeSegments[segment].body
        local bodyB = ropeSegments[segment + 1].body
        newJoint = Rope:connectRopeSegment(bodyA, bodyB)
        table.insert(ropeJoints, newJoint)
    end

    -- hook configuration
    hook = ropeSegments[#ropeSegments]
    hook.fixture:setUserData("hook")
    hook.docking = false -- is holding an object?
    hook.dockJoint = nil -- the joint
    hook.contactBody = nil -- the body that is holding or contacting
end

function Rope:fixRopePosition()
    for i = 1, #ropeSegments - 1 do
        local segmentA = ropeSegments[i]
        local segmentB = ropeSegments[i + 1]

        local dx = segmentB.body:getX() - segmentA.body:getX()
        local dy = segmentB.body:getY() - segmentA.body:getY()
        local distance = math.sqrt(dx * dx + dy * dy)

        local desiredDistance = 10
        local correctionFactor = 0.5

        if distance > desiredDistance then
            local offsetX = (dx / distance) * (distance - desiredDistance) * correctionFactor
            local offsetY = (dy / distance) * (distance - desiredDistance) * correctionFactor
            segmentB.body:setPosition(
                segmentB.body:getX() - offsetX,
                segmentB.body:getY() - offsetY
            )
        end
    end
end

function Rope:draw()
    drawSegments = true

    love.graphics.push()
    if drawSegments then
        for _, segment in ipairs(ropeSegments) do
            line = love.graphics.line(
            segment.body:getX(),
            segment.body:getX(),
            segment.body:getX(),
            segment.body:getX())
            love.graphics.setLineWidth(6)
            love.graphics.setLineStyle("smooth")
        end
    end
    love.graphics.pop()

    for _, joint in ipairs(ropeJoints) do
        love.graphics.line(joint:getAnchors())
    end
end

return Rope