-- A sample 3rd person camera
-- /luac camera.LoadScript "tpscam.lua"

-- TODO: add support for lateral offset

DEFAULT_LOOKAT_OFFSET = Vec( 0, 2, 0 )  -- offset on target point to look at
DEFAULT_CAM_OFFSET = Vec( 0, 2, 6 )    -- (lateral offset, height, distance to player)

camOffset = DEFAULT_CAM_OFFSET
minDistance = 1
zoomSensitivity = 0.5
smoothSpeed = 5.0
checkForWorldCollisions = false -- doesn't work well yet, Racyast/SphereSweep needs to be tweaked

-- note: this should probably be exposed on the engine side directly (Vec.Lerp)
local function VecLerp( v1, v2, t )
	return v1 * ( 1 - t ) + v2 * t
end

function OnActivate()
    debug.log('warning', 'Activating 3rd Person Camera Mode' )
end

function OnDeactivate()
    debug.log('warning', 'Deactivating 3rd Person Camera Mode' )
end

function OnReset()
    camOffset = DEFAULT_CAM_OFFSET
    controller:SetPosition( camOffset )
end

function OnUpdate(dt)
    local forward = Vec( 0, 0, 1 ) * player.rot -- the player forward vector in world space
    local up = Vec( 0, 1, 0 )
    local lookAtPos = player.pos + DEFAULT_LOOKAT_OFFSET
    local idealPos = lookAtPos - forward * camOffset.z + up * camOffset.y
    local pos = VecLerp( controller:GetPosition(), idealPos, smoothSpeed * dt )
    
    -- check for collisions with the environment and move the camera closer to make sure 
    -- we have clear line of sight to our target
    if checkForWorldCollisions then
        hit = DWEngine.SphereSweep( lookAtPos, pos, 1 )
        if hit then
            pos = hit.pos - hit.normal
        end
    end
    
    controller:SetPosition( pos )
    controller:LookAtPosition( lookAtPos )
end

function OnZoom(amount)
    camOffset.z = camOffset.z - zoomSensitivity * amount
    if camOffset.z < minDistance then
        camOffset.z = minDistance
    end
end

-- this is required to make the script load properly (side-effect of engine's CoreLua::Run() method)
return true