--------------------------------------------
-- Lookat (position, target, up) to Transform.
-- @author      OTOY
-- @version     0.1
-- @script-id   fa54a91a-22be-4ba7-9075-5a5d232c3e34
--------------------------------------------

local inputLinkers = {}
local outputLinkers = {}
local nodeOutputValue = nil

local function setInputLinkers(graph)

    local liPosition =
    {
        key = "pos",
        label = "Position",
        description = "The position of the camera.",
        type = octane.pinType.PT_FLOAT,
        defaultNodeType = octane.nodeType.NT_FLOAT,
        defaultValue = {0, 0.5, 1.0},
    }

    local liTarget =
    {
        key = "target",
        label = "Target",
        description = "The target position, i.e. the point the camera looks at.",
        type = octane.pinType.PT_FLOAT,
        defaultNodeType = octane.nodeType.NT_FLOAT,
        defaultValue = {0, 0, 0},
    }

    local liUp =
    {
        key = "up",
        label = "Up-vector",
        description = "The up-vector, i.e. the vector that defines where is up.",
        type = octane.pinType.PT_FLOAT,
        defaultNodeType = octane.nodeType.NT_FLOAT,
        defaultValue = {0, 1, 0},
    }

    local linkersInfo = { liPosition, liTarget, liUp }

    local inputs = graph:setInputLinkers(linkersInfo)

    for i, info in ipairs(linkersInfo) do
        inputLinkers[info.key] = inputs[i]
    end
end

local function setOutputLinkers(graph)

    local liOutput =
    {
        key = "outputValue",
        label = "Output value",
        type = octane.pinType.PT_TRANSFORM,
        defaultValue = octane.matrix.getIdentity()
    }

    local linkersInfo = { liOutput }

    local outputs = graph:setOutputLinkers(linkersInfo)

    for i, info in ipairs(linkersInfo) do
        outputLinkers[info.key] = outputs[i]
    end
end

local function update(script)

  local pos = script:getInputValue(inputLinkers.pos)
  local target = script:getInputValue(inputLinkers.target)
  local up = script:getInputValue(inputLinkers.up)

  local zaxis = octane.vec.normalized(octane.vec.sub(pos, target))
  local xaxis = octane.vec.normalized(octane.vec.cross(up, zaxis))
  local yaxis = octane.vec.cross(zaxis, xaxis)

  local m =
  {
      {xaxis[1], yaxis[1], zaxis[1], pos[1]},
      {xaxis[2], yaxis[2], zaxis[2], pos[2]},
      {xaxis[3], yaxis[3], zaxis[3], pos[3]},
  }

  nodeOutputValue:setAttribute(octane.attributeId.A_TRANSFORM, m)
end

local function prepareGraph(graph)
  nodeOutputValue = octane.node.create
  {
      type = octane.nodeType.NT_TRANSFORM_VALUE,
      name = "Value",
      graphOwner = graph
  }

  outputLinkers.outputValue:connectTo(octane.pinId.P_INPUT, nodeOutputValue)
end


--------------------------------------------

local node = {}
node._name = "Lookat to Transform"
node._icon = octane.image.fromBase64("iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAABHNCSVQICAgIfAhkiAAAAAlwSFlz"..
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  "Z8rMXcHTCZx7gBUzzwLAH61qoROxh1pDAAAAAElFTkSuQmCC", 3)
node.evaluateAllChanges = true

-- Callback called after initializing the scripted graph with the code.
function node.onInit(self, graph)

    graph:setAttribute(octane.attributeId.A_COLOR, { 0.20, 0.35, 0.55 }, true)

    setInputLinkers(graph)
    setOutputLinkers(graph)
    prepareGraph(graph)
    update(self)
    octane.nodegraph.unfold(graph, true)
end

-- Callback called when the connected value of one of the input linker nodes changes.
function node.onEvaluate(self, graph)
    update(self)
end

return node