GPS CONSTELATION

-- GPS Host Program with Coordinate Storage

-- File to store coordinates
local COORD_FILE = "gps_coords.txt"

-- Function to read coordinates from file
local function readCoordsFromFile()
    if fs.exists(COORD_FILE) then
        local file = fs.open(COORD_FILE, "r")
        local x = tonumber(file.readLine())
        local y = tonumber(file.readLine())
        local z = tonumber(file.readLine())
        file.close()
        if x and y and z then
            return x, y, z
        end
    end
    return nil
end

-- Function to write coordinates to file
local function writeCoordsToFile(x, y, z)
    local file = fs.open(COORD_FILE, "w")
    file.writeLine(x)
    file.writeLine(y)
    file.writeLine(z)
    file.close()
end

-- Function to get coordinates from user input
local function getCoords()
    print("Enter this computer's exact Minecraft block coordinates:")
    io.write("X: ")
    local x = tonumber(io.read())
    io.write("Y: ")
    local y = tonumber(io.read())
    io.write("Z: ")
    local z = tonumber(io.read())
    return x, y, z
end

-- Main program
local x, y, z = readCoordsFromFile()

if not x or not y or not z then
    x, y, z = getCoords()
    if not x or not y or not z then
        print("Invalid coordinates. Exiting.")
        return
    end
    writeCoordsToFile(x, y, z)
    print("Coordinates saved to file.")
else
    print("Using stored coordinates:", x, y, z)
end

print("Starting GPS Host at Minecraft coordinates:", x, y, z)

-- Ensure the modem is on
local sides = {"top", "bottom", "left", "right", "front", "back"}
local modemOpened = false

for _, side in ipairs(sides) do
    if peripheral.isPresent(side) and peripheral.getType(side) == "modem" then
        rednet.open(side)
        modemOpened = true
        print("Modem opened on side: " .. side)
        break
    end
end

if not modemOpened then
    print("No modem found. Please attach a modem to the computer.")
    return
end

-- Start the GPS host
print("Starting GPS host...")
shell.run("gps", "host", x, y, z)

-- This point is reached only if shell.run returns, which it shouldn't under normal operation
print("GPS Host has stopped. Please check for errors.")