1 files changed, 142 insertions, 0 deletions
diff --git a/src/util.lua b/src/util.lua
new file mode 100644
index 0000000..f74953a
--- /dev/null
+++ b/src/util.lua
@@ -0,0 +1,142 @@
+--[[
+Various helpful functions
+]]
+local util = {}
+function util.cartesian(...)
+	-- cartesian(tbl1, tbl2, tbl3, ...)
+	-- for each table, returns a permutation of key, value in tbl1, tbl2, ect.
+	local args = {...}
+	return coroutine.wrap(function()
+		local cursors = {} -- cursors[1], cursors[3], ect. are the keys
+		for k,v in ipairs(args) do
+			local a,b = next(v,nil)
+			cursors[(k*2) - 1] = a
+			cursors[(k*2)] = b
+		end
+		coroutine.yield(unpack(cursors))
+		local any_left = true
+		while any_left do
+			while next(args[#args],cursors[#cursors - 1]) do
+				local a,b = next(args[#args],cursors[#cursors - 1])
+				cursors[#cursors - 1] = a
+				cursors[#cursors] = b
+				coroutine.yield(unpack(cursors))
+			end
+			any_left = false
+			for i = #args, 1, -1 do
+				if next(args[i],cursors[(i*2)-1]) then
+					cursors[(i*2)-1], cursors[i*2] = next(args[i],cursors[(i*2)-1])
+					for j = i+1, #args do
+						cursors[(j*2)-1], cursors[j*2] = next(args[j],nil)
+					end
+					coroutine.yield(unpack(cursors))
+					any_left = true
+					break
+				end
+			end
+		end
+	end)
+end
+
+-- Override tostring to display more info about the table
+local old_tostring = tostring
+local numtabs = 0
+local printed_tables = {}
+local function tostring_helper(el)
+        assert(type(el) == "table", "Tried to call helper with something that was not a table, it was a " .. type(el))
+        local mt = getmetatable(el)
+        if mt and mt.__tostring then
+                return mt.__tostring(el)
+        elseif printed_tables[el] == true then
+                return old_tostring(el)
+        else
+                printed_tables[el] = true
+                numtabs = numtabs + 1
+                local strbuilder = {"{"}
+                for k,v in pairs(el) do
+                        local key,value
+                        if type(k) == "table" then
+                                key = tostring_helper(k)
+                        else
+                                key = old_tostring(k)
+                        end
+                        if type(v) == "table" then
+                                value = tostring_helper(v)
+                        else
+                                value = old_tostring(v)
+                        end
+                        strbuilder[#strbuilder + 1] = string.format("%s%s : %s", string.rep("\t",numtabs), key, value)
+                end
+                strbuilder[#strbuilder + 1] = string.rep("\t",numtabs - 1) .. "}"
+                numtabs = numtabs - 1
+                return table.concat(strbuilder,"\n")
+        end
+
+end
+function tostring(el)
+        printed_tables = {}
+        if type(el) == "table" then
+                return tostring_helper(el)
+        end
+        return old_tostring(el)
+end
+
+function util.reverse(tbl, val)
+	val = val or true
+	local ret = {}
+	for _,v in ipairs(tbl) do
+		ret[v] = val
+	end
+	return ret
+end
+
+function util.typecheck(tbl, ...)
+	local args = {...}
+	assert(#args % 2 == 0,"Typecheck should have an odd number of arguments, found " .. tostring(#args + 1) .. ".")
+	for i = 1, #args, 2 do
+		assert(args[i] and type(args[i]) == "string", "Cannot check a field of type " .. type(args[i]) .. " at position " .. tostring(i + 1) .. ".")
+		assert(tbl[args[i]], "Failed to find a field: " .. args[i])
+		assert(args[i+1] and type(args[i + 1]) == "string", "Cannot check for a type " .. type(args[i + 1]) .. " at position " .. tostring(i + 2) .. ".")
+		assert(type(tbl[args[i]]) == args[i+1], "Expected a " .. args[i+1] .. " at position " .. tostring(i+2) .. " but found a " .. type(tbl[args[i]]))
+	end
+	return true
+end
+
+function util.peer_to_code(str)
+	-- Turn peerjs peer ids into shorter strings
+	-- Example: 0dbbe67a-5358-4ea2-910a-195754b556a7
+	-- = 16 bytes
+	local buffer = am.buffer(16)
+	local view = buffer:view("ubyte")
+	local i = 0
+	for byte in str:gmatch("%x%x") do
+		local n = tonumber(byte,16)
+		view[(i % 16) + 1] = n
+		i = i + 1
+	end
+	local encoded = am.base64_encode(buffer)
+	return encoded:gsub("[/+]",{["/"] = "-",["+"] = "_"}):sub(1,22) -- chop the last 2 glyphs, assume 16 bytes
+end
+
+function util.code_to_peer(str)
+	local padded = str:gsub("[_-]",{["-"] = "/", ["_"] = "+"}) .. "=="
+	local buffer = am.base64_decode(padded)
+	local view = buffer:view("ubyte")
+	local dashes = {4,2,2,2,6}
+	local builder = {}
+	local i = 1
+	while #dashes > 0 do
+		local nbytes = table.remove(dashes,1)
+		for _ = 1, nbytes do
+			table.insert(builder, string.format("%02x",view[i]))
+			i = i + 1
+		end
+		if #dashes > 0 then
+			table.insert(builder,"-")
+		end
+	end
+	ret = table.concat(builder)
+	return ret
+end
+
+return util