Merge pull request 'issue-2 Resolves #2' (#4) from issue-2 into main

Reviewed-on: #4

tg_server/hash.lua

@@ -0,0 +1,7 @@
+function hash(str)
+    local hash = 0
+    for i = 1, #str do
+        hash = (hash * 31 + string.byte(str, i)) % 65536
+    end
+    return string.format("%04X", hash)
+end

tg_server/tg_server.lua

@@ -1,5 +1,6 @@
 local fullPath = shell.getRunningProgram()
 local dir = fullPath:match("^(.*/)") or ""
+local args = {...}
 
 local config = dofile(dir..'taskguard.cfg')
 
@@ -13,14 +14,7 @@ local function split(str, divider)
     return t
 end
 
-local function hash(str)
-    local hash = 0
-    for i = 1, #str do
-        hash = (hash * 31 + string.byte(str, i)) % 65536
-    end
-    return string.format("%04X", hash)
-end
-
+dofile(dir..'hash.lua')
 
 local function check_for_outdated_sessions()
     local expired = 0
@@ -57,10 +51,10 @@ local function validate_key(card_holder, card_clearance, random_chars)
     end
 end
 
+if args[1] == "serve" then
     rednet.open(config.modem_side)
     rednet.host('tg', config.name)
     print("Server started, waiting for requests...")
-
     while true do
         local id, msg, proto = rednet.receive('tg')
         check_for_outdated_sessions()
@@ -116,3 +110,39 @@ while true do
             print("Transaction finished")
         end
     end
+elseif args[1] == "add_card" then
+    if args[2] then
+        local new_card = args[2]
+        local new_card_parts = split(new_card, ',')
+        local card_holder = new_card_parts[1]
+
+        local key_file = fs.open(card_holder..'.key', 'w')
+        key_file.write(new_card)
+        key_file.close()
+
+        local trusted_keys = fs.open(dir..config.key_file, 'a')
+        local card_hash = hash(new_card)
+        trusted_keys.write(card_hash)
+        trusted_keys.close()
+    end
+elseif args[1] == "remove_card" then
+    if args[2] then
+        local key_hash = args[2]
+        local trusted_keys = fs.open(dir..config.key_file, 'r')
+        local new_key_table = {}
+        while true do
+            local trusted_hash = trusted_keys.readLine()
+            if trusted_hash ~= key_hash then
+                table.insert(new_key_table, trusted_hash)
+            end
+            if not trusted_hash then break end -- Stop when EOF reached
+        end
+        trusted_keys.close()
+
+        local trusted_keys = fs.open(dir..config.key_file, 'w+')
+        for _, entry in ipairs(new_key_table) do
+            trusted_keys.write(entry .. '\n')
+        end
+        trusted_keys.close()
+    end
+end