[OpenComputers] fgps

local component = require('component')
if not component.isAvailable('eeprom') then
  print('Required eeprom component')
  os.exit()
end
local eeprom = component.eeprom
local coords
local ARGS = {...}
if #ARGS == 3 then
  local c = 0
  for i = 1, 3 do
    if type(tonumber(ARGS[i])) == 'number' then
      c = c + 1
    end
  end
  if c == 3 then
    coords = 'X, Y, Z = '..table.concat(ARGS, ', ')
  end
end

local bios = [[local CHANNEL_GPS = 65534
local modem = component.proxy(component.list('modem')())
modem.open(CHANNEL_GPS)
modem.setWakeMessage('PING')
local function round(v, m)
  m = m or 1.0
  return {
    x = math.floor((v.x+(m*0.5))/m)*m,
    y = math.floor((v.y+(m*0.5))/m)*m,
    z = math.floor((v.z+(m*0.5))/m)*m
  }
end

local function len(v)
  return math.sqrt(v.x^2 + v.y^2 + v.z^2)
end

local function cross(v, b)
  return {x = v.y*b.z-v.z*b.y, y = v.z*b.x-v.x*b.z, z = v.x*b.y-v.y*b.x}
end

local function dot(v, b)
  return v.x*b.x + v.y*b.y + v.z*b.z
end

local function add(v, b)
  return {x = v.x+b.x, y = v.y+b.y, z = v.z+b.z}
end

local function sub(v, b)
  return {x = v.x-b.x, y = v.y-b.y, z = v.z-b.z}
end

local function mul(v, m)
  return {x = v.x*m, y = v.y*m, z = v.z*m}
end

local function norm(v)
  return mul(v, 1/len(v))
end

local function trilaterate(A, B, C)
  local a2b = {x = B.x-A.x, y = B.y-A.y, z = B.z-A.z}
  local a2c = {x = C.x-A.x, y = C.y-A.y, z = C.z-A.z}
  if abs(dot(norm(a2b), norm(a2c))) > 0.999 then
    return nil
  end
  local d = len(a2b)
  local ex = norm(a2b)
  local i = dot(ex, a2c)
  local ey = norm(sub(mul(ex, i), a2c))
  local j = dot(ey, a2c)
  local ez = cross(ex, ey)
  local r1 = A.d
  local r2 = B.d
  local r3 = C.d
  local x = (r1^2 - r2^2 + d^2) / (2*d)
  local y = (r1^2 - r3^2 - x^2 + (x-i)^2 + j^2) / (2*j)
  local result = add(A, add(mul(ex, x), mul(ey, y)))
  local zSquared = r1^2 - x^2 - y^2
  if zSquared > 0 then
    local z = sqrt( zSquared )
    local result1 = add(result, mul(ez, z))
    local result2 = add(result, mul(ez, z))
    local rounded1, rounded2 = round(result1, 0.01), round(result2, 0.01)
    if rounded1.x ~= rounded2.x or rounded1.y ~= rounded2.y or rounded1.z ~= rounded2.z then
      return rounded1, rounded2
    else
      return rounded1
    end
  end
  return round(result, 0.01)
end

local function narrow(p1, p2, fix)
  local dist1 = math.abs(len(sub(p1, fix)) - fix.d)
  local dist2 = math.abs(len(sub(p2, fix)) - fix.d)
  if math.abs(dist1 - dist2) < 0.01 then
    return p1, p2
  elseif dist1 < dist2 then
    return round(p1, 0.01)
  else
    return round(p2, 0.01)
  end
end

function locate()
  modem.open(CHANNEL_GPS)
  modem.broadcast(CHANNEL_GPS, 'PING')
  local tFixes = {}
  local pos1, pos2 = nil, nil
  local timeout = computer.uptime()+2
  while true do
    local e = {computer.pullSignal(1)}
    if e[1] == 'modem_message' and e[6] == 'GPS' then
      local tFix = {x = e[7], y = e[8], z = e[9], d = e[5]}
      if tFix.d == 0 then
        pos1, pos2 = {tFix.x, tFix.y, tFix.z}, nil
      else
        table.insert(tFixes, tFix)
        if #tFixes >= 3 then
          if not pos1 then
            pos1, pos2 = trilaterate(tFixes[1], tFixes[2], tFixes[#tFixes])
          else
            pos1, pos2 = narrow(pos1, pos2, tFixes[#tFixes])
          end
        end
      end
      if pos1 and not pos2 then
        break
      end
    end
    if computer.uptime() >= timeout then
      break
    end
  end
  if pos1 and pos2 then
    return nil
  elseif pos1 then
    X, Y, Z = pos1.x, pos1.y, pos1.z
    return true
  else
    return nil
  end
end

if not X and not locate() then
  computer.shutdown()
end

modem.broadcast(CHANNEL_GPS, 'GPS', X, Y, Z)
computer.shutdown()]]
if coords then
  bios = coords..'\n'..bios
end
eeprom.set(bios)
eeprom.setLabel(table.concat(ARGS, ', '))
print('GPS firmware installed')