add error if modems.info missing

GLONASS/UNS.lua

@@ -1,5 +1,5 @@
 --[[
-Unitary Navigational System v0
+Unitary Navigational System
 
 This basic script attempts to consolidate a GPS constellation into a single computer. Because using 4 is plain wasteful!
 It was made out of project "GLONASS Tower" I wrote back in 2022 after first discovering CC
@@ -9,23 +9,6 @@ TODO: Bring back cool logging!
 
 local UNS_VERSION = 0
 
--- modems format:
---[[
-        {
-        id = "modem_id",
-        pos = {
-            1,  -- x
-            1,  -- y
-            1   -- z
-        },
-        primary = true,  -- The modem that does listening
-        modem = nil,  -- Declared below, leave as nil
-    }
-]]
-local file = fs.open("modems.info", "r")
-local contents = file.readAll()
-file.close()
-local modems = textutils.unserialise(contents)
 
 -- Simple logging. It's not ideal but will do as a "temporary" solution
 local function log(message)
@@ -40,6 +23,40 @@ term.clear()
 term.setCursorPos(1, 1)
 log("UNS v" .. UNS_VERSION)
 
+-- modems.info format:
+--[[
+    {
+        id = "modem_id",
+        pos = {
+            1,  -- x
+            1,  -- y
+            1   -- z
+        },
+        primary = true,  -- The modem that does listening
+        modem = nil,  -- Declared below, leave as nil
+    }
+]]
+local modems
+if fs.exists("modems.info") then
+    local file = fs.open("modems.info", "r")
+    local contents = file.readAll()
+    file.close()
+    modems = textutils.unserialise(contents)
+else
+    log("error: modems.info file missing")
+
+    -- TODO: Automatic setup
+    print("Attempt automatic setup? (Y/n) : ")
+    local ans = read()
+    if ans:lower() == "y" or ans == "" then
+        log("Not implemented yet, sorry!")
+    else
+        log("nothing to do")
+        os.exit()
+    end
+end
+
+
 -- Prepare all modems
 local primary_modem = nil
 for i, modem in ipairs(modems) do
@@ -47,7 +64,7 @@ for i, modem in ipairs(modems) do
     if modems[i].primary then
         primary_modem = modems[i].modem
     end
-    log("load <" .. modem.id .. "> pos - " .. textutils.serialise(modem.pos))
+    log("loaded <" .. modem.id .. "> pos - " .. textutils.serialise(modem.pos))
 end
 if primary_modem == nil then
     primary_modem = modems[0].modem
@@ -61,9 +78,9 @@ while true do
         event, side, channel, replyChannel, message, distance = os.pullEvent("modem_message")
     until channel == gps.CHANNEL_GPS and message == "PING"
 
-    log("Recieved location request, d-" .. distance)
+    log("recieved location request, d-" .. distance)
     for _, modem in ipairs(modems) do
         modem.modem.transmit(channel, replyChannel, modem.pos)
-        log("Modem <" .. modem.id .. "> transmitted location")
+        log("modem <" .. modem.id .. "> transmitted location")
     end
 end