Economy: metal.lua

----------------------------------------------------------------
--parameters
----------------------------------------------------------------
local maxMetal = 1 --scale metal by this value; acts like map max metal

----------------------------------------------------------------
--speed-ups
----------------------------------------------------------------
local mapSizeX = Game.mapSizeX
local mapSizeZ = Game.mapSizeZ
local extractorRadius = Game.extractorRadius

local GetGroundInfo = Spring.GetGroundInfo
local GetUnitPosition = Spring.GetUnitPosition

----------------------------------------------------------------
--constants
----------------------------------------------------------------

local metalMapMaxX = math.floor(mapSizeX / metalMapScale) - 1
local metalMapMaxZ = math.floor(mapSizeX / metalMapScale) - 1
local extractSearchMax = math.floor(extractorRadius / metalMapScale)

local metalMapScale = 16
local metalMapScaleSq = 256

----------------------------------------------------------------
--locals
----------------------------------------------------------------

--2-D array that stores the metal map
local metalMap = {}

--3-D array that stores what mexes are lined up to control each particular square on the metal map
local controlMap = {}

--quarter-circle indicating whether a particular metal map square is within the extractor radius of the origin
local circleMask = {}

--table of mexes; entries are indexed by unitID and have values equal to the raw metal produced by the mex
local mexes = {}

--setup metal map, control map
local function SetupMaps()
  for i = 0, metalMapMaxX do
    metalMap[i] = {}
    controlMap[i] = {}
    for j = 0, metalMapMaxZ do
      _, metalMap[i][j] = GetGroundInfo(metalMapScale * i + 8, metalMapScale * j + 8) * maxMetal
      controlMap[i][j] = {}
    end
  end
end

--setup circle mask
local function SetupCircleMask()
  do
    local radiusSq = extractorRadius * extractorRadius
    for i = 0, extractSearchMax do
      for j = 0, extractSearchMax do
        if ((i*i + j*j) * metalMapScaleSq < radiusSq) then
          circleMask[i][j] = true
        end
      end
    end
  end
end

local function GetTotalGlobalMetal()
  local result = 0
  for i = 0, metalMapMaxX do
    for j = 0, metalMapMaxZ do
      result = result + metalMap[i][j]
    end
  end
  return result
end

local function GetMetalMapCoords(posX, posZ)
  return math.floor(posX / metalMapScale), math.floor(posZ / metalMapScale)
end

local function AddMex(unitID)
  local metal = 0
  local posX, _, posZ = GetUnitPosition(unitID)
  local mPosX, mPosZ = GetMetalMapCoords(posX, posZ)
  
  --establish how far we are willing to search
  local backX = math.min(extractSearchMax, mPosX)
  local frontX = math.min(extractSearchMax, metalMapMaxX - mPosX)
  local backZ = math.min(extractSearchMax, mPosZ)
  local frontZ = math.min(extractSearchMax, metalMapMaxZ - mPosZ)
  
  --iterate over the search area
  for i = -backX, frontX do
    for j = -backZ, frontZ do
      --check our pre-calculated mask to see if each spot is within the extractor radius
      if (circleMask[math.abs(i)][math.abs(j)]) then
        --position on metal map
        local iPos = mPosX + i
        local jPos = mPosZ + j
        
        --if spot not already claimed, give the metal to the mex
        if (not controlMap[iPos][jPos]) then
          metal = metal + metalMap[iPos][jPos]
        end
        
        --add the mex to the queue of controllers
        table.insert(controlMap[iPos][jPos], unitID)
      end
    end
  end
  mexes[unitID] = metal
end

local function RemoveMex(unitID)
  local metal = 0
  local posX, _, posZ = GetUnitPosition(unitID)
  local mPosX, mPosZ = GetMetalMapCoords(posX, posZ)
  
  --establish how far we are willing to search
  local backX = math.min(extractSearchMax, mPosX)
  local frontX = math.min(extractSearchMax, metalMapMaxX - mPosX)
  local backZ = math.min(extractSearchMax, mPosZ)
  local frontZ = math.min(extractSearchMax, metalMapMaxZ - mPosZ)
  
  --iterate over the search area
  for i = -backX, frontX do
    for j = -backZ, frontZ do
      --position on metal map
      local iPos = mPosX + i
      local jPos = mPosZ + j
      
      --if we control this spot, give it to the next in line
      if (controlMap[i][j][1] == unitID) then
        --remove any mexes in line which no longer exist
        local nextID
        
        repeat
          table.remove(controlMap[i][j], 1)
          nextID = controlMap[i][j][1]
        until (not nextID or mexes[nextID])
        
        --add the metal to the new owner
        if (nextID) then
          mexes[nextID] = mexes[nextID] + metalMap[iPos][jPos]
        end
      end
    end
  end
  mexes[unitID] = nil
end