Add lua-based server implementation

flake.nix

@@ -10,6 +10,7 @@
     devShell.${system} = pkgs.mkShell rec {
       buildInputs = [
         pkgs.deno
+        (pkgs.lua5_3.withPackages(ps: [ ps.http ps.fennel ]))
       ];
     };
   };

lua-server/echo.fnl

@@ -0,0 +1,78 @@
+;; a simple websocket echo server
+;; 
+;; usage: fennel echo.fnl <port>
+;;
+;; test via websocat ws://127.0.0.1:<port>
+
+(local port (or (. arg 1) 0))
+(local http-server (require :http.server))
+(local http-headers (require :http.headers))
+(local websocket (require :http.websocket))
+
+;; this handler contains the main logic. it is called further down in this
+;; file, as soon as a websocket connection has been established.
+
+(fn handle-websocket [ws]
+  ;; TODO: Generate birb name
+  (assert (ws:accept))
+  ;; connection is open
+  (print "connection opened")
+  (ws:send "Welcome to the echo server! Send any command, it will be sent back to you.")
+  (var closed? false)
+  (while (not closed?)
+    (local (data opcode) (ws:receive))
+    (if data
+      (do
+        (assert (= opcode :text))
+        (print "opcode" opcode "data" data)
+        (ws:send data))
+      ;; connection has been closed
+      (do
+        (print "connection closed")
+        (ws:close)
+        (set closed? true)))))
+
+;; this is the low-level server code. it's an adapted version of
+;; https://github.com/daurnimator/lua-http/blob/ddab2835/examples/server_hello.lua
+
+(local server
+  (assert (http-server.listen {:host :localhost
+                               :onerror (fn [server context op err errno]
+                                          (var msg (.. op " on " (tostring context) " failed"))
+                                          (when err
+                                            (set msg (.. msg ": " (tostring err))))
+                                          (assert (io.stderr:write msg "\n")))
+                               :onstream (fn [server stream]
+                                           (let [headers (assert (stream:get_headers))
+                                                 method (headers:get ":method")]
+                                             ;; log request
+                                             (assert (io.stdout:write (string.format "[%s] \"%s %s HTTP/%g\"  \"%s\" \"%s\"\n"
+                                                                                     (os.date "%d/%b/%Y:%H:%M:%S %z")
+                                                                                     (or method "")
+                                                                                     (or (headers:get ":path") "")
+                                                                                     stream.connection.version
+                                                                                     (or (headers:get :referer) "-")
+                                                                                     (or (headers:get :user-agent) "-"))))
+                                             ;; start and handle websocket connection
+                                             (local ws (websocket.new_from_stream stream headers))
+                                             (if ws
+                                               (handle-websocket ws)
+                                               ;; if we couldn't establish the websocket connection, something's wrong
+                                               (assert (stream:write_headers (doto (http-headers.new)
+                                                                                (: :append ::status :400)) true)))))
+                               : port})))
+
+(assert (server:listen))
+
+(let [(_ _ bound-port) (server:localname)]
+  (assert (io.stderr:write (.. "Now listening on port " bound-port "\n"))))
+
+;; automatically start server when run from the command line
+(when (> (length arg) 0)
+  (assert (server:loop)))
+
+(comment
+  ;; run this to handle a response manually
+  (for [i 1 3]
+    (server:step))
+  )

lua-server/json.lua

@@ -0,0 +1,388 @@
+--
+-- json.lua
+--
+-- Copyright (c) 2020 rxi
+--
+-- Permission is hereby granted, free of charge, to any person obtaining a copy of
+-- this software and associated documentation files (the "Software"), to deal in
+-- the Software without restriction, including without limitation the rights to
+-- use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+-- of the Software, and to permit persons to whom the Software is furnished to do
+-- so, subject to the following conditions:
+--
+-- The above copyright notice and this permission notice shall be included in all
+-- copies or substantial portions of the Software.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+-- IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+-- FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+-- AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+-- LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+-- OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+-- SOFTWARE.
+--
+
+local json = { _version = "0.1.2" }
+
+-------------------------------------------------------------------------------
+-- Encode
+-------------------------------------------------------------------------------
+
+local encode
+
+local escape_char_map = {
+  [ "\\" ] = "\\",
+  [ "\"" ] = "\"",
+  [ "\b" ] = "b",
+  [ "\f" ] = "f",
+  [ "\n" ] = "n",
+  [ "\r" ] = "r",
+  [ "\t" ] = "t",
+}
+
+local escape_char_map_inv = { [ "/" ] = "/" }
+for k, v in pairs(escape_char_map) do
+  escape_char_map_inv[v] = k
+end
+
+
+local function escape_char(c)
+  return "\\" .. (escape_char_map[c] or string.format("u%04x", c:byte()))
+end
+
+
+local function encode_nil(val)
+  return "null"
+end
+
+
+local function encode_table(val, stack)
+  local res = {}
+  stack = stack or {}
+
+  -- Circular reference?
+  if stack[val] then error("circular reference") end
+
+  stack[val] = true
+
+  if rawget(val, 1) ~= nil or next(val) == nil then
+    -- Treat as array -- check keys are valid and it is not sparse
+    local n = 0
+    for k in pairs(val) do
+      if type(k) ~= "number" then
+        error("invalid table: mixed or invalid key types")
+      end
+      n = n + 1
+    end
+    if n ~= #val then
+      error("invalid table: sparse array")
+    end
+    -- Encode
+    for i, v in ipairs(val) do
+      table.insert(res, encode(v, stack))
+    end
+    stack[val] = nil
+    return "[" .. table.concat(res, ",") .. "]"
+
+  else
+    -- Treat as an object
+    for k, v in pairs(val) do
+      if type(k) ~= "string" then
+        error("invalid table: mixed or invalid key types")
+      end
+      table.insert(res, encode(k, stack) .. ":" .. encode(v, stack))
+    end
+    stack[val] = nil
+    return "{" .. table.concat(res, ",") .. "}"
+  end
+end
+
+
+local function encode_string(val)
+  return '"' .. val:gsub('[%z\1-\31\\"]', escape_char) .. '"'
+end
+
+
+local function encode_number(val)
+  -- Check for NaN, -inf and inf
+  if val ~= val or val <= -math.huge or val >= math.huge then
+    error("unexpected number value '" .. tostring(val) .. "'")
+  end
+  return string.format("%.14g", val)
+end
+
+
+local type_func_map = {
+  [ "nil"     ] = encode_nil,
+  [ "table"   ] = encode_table,
+  [ "string"  ] = encode_string,
+  [ "number"  ] = encode_number,
+  [ "boolean" ] = tostring,
+}
+
+
+encode = function(val, stack)
+  local t = type(val)
+  local f = type_func_map[t]
+  if f then
+    return f(val, stack)
+  end
+  error("unexpected type '" .. t .. "'")
+end
+
+
+function json.encode(val)
+  return ( encode(val) )
+end
+
+
+-------------------------------------------------------------------------------
+-- Decode
+-------------------------------------------------------------------------------
+
+local parse
+
+local function create_set(...)
+  local res = {}
+  for i = 1, select("#", ...) do
+    res[ select(i, ...) ] = true
+  end
+  return res
+end
+
+local space_chars   = create_set(" ", "\t", "\r", "\n")
+local delim_chars   = create_set(" ", "\t", "\r", "\n", "]", "}", ",")
+local escape_chars  = create_set("\\", "/", '"', "b", "f", "n", "r", "t", "u")
+local literals      = create_set("true", "false", "null")
+
+local literal_map = {
+  [ "true"  ] = true,
+  [ "false" ] = false,
+  [ "null"  ] = nil,
+}
+
+
+local function next_char(str, idx, set, negate)
+  for i = idx, #str do
+    if set[str:sub(i, i)] ~= negate then
+      return i
+    end
+  end
+  return #str + 1
+end
+
+
+local function decode_error(str, idx, msg)
+  local line_count = 1
+  local col_count = 1
+  for i = 1, idx - 1 do
+    col_count = col_count + 1
+    if str:sub(i, i) == "\n" then
+      line_count = line_count + 1
+      col_count = 1
+    end
+  end
+  error( string.format("%s at line %d col %d", msg, line_count, col_count) )
+end
+
+
+local function codepoint_to_utf8(n)
+  -- http://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=iws-appendixa
+  local f = math.floor
+  if n <= 0x7f then
+    return string.char(n)
+  elseif n <= 0x7ff then
+    return string.char(f(n / 64) + 192, n % 64 + 128)
+  elseif n <= 0xffff then
+    return string.char(f(n / 4096) + 224, f(n % 4096 / 64) + 128, n % 64 + 128)
+  elseif n <= 0x10ffff then
+    return string.char(f(n / 262144) + 240, f(n % 262144 / 4096) + 128,
+                       f(n % 4096 / 64) + 128, n % 64 + 128)
+  end
+  error( string.format("invalid unicode codepoint '%x'", n) )
+end
+
+
+local function parse_unicode_escape(s)
+  local n1 = tonumber( s:sub(1, 4),  16 )
+  local n2 = tonumber( s:sub(7, 10), 16 )
+   -- Surrogate pair?
+  if n2 then
+    return codepoint_to_utf8((n1 - 0xd800) * 0x400 + (n2 - 0xdc00) + 0x10000)
+  else
+    return codepoint_to_utf8(n1)
+  end
+end
+
+
+local function parse_string(str, i)
+  local res = ""
+  local j = i + 1
+  local k = j
+
+  while j <= #str do
+    local x = str:byte(j)
+
+    if x < 32 then
+      decode_error(str, j, "control character in string")
+
+    elseif x == 92 then -- `\`: Escape
+      res = res .. str:sub(k, j - 1)
+      j = j + 1
+      local c = str:sub(j, j)
+      if c == "u" then
+        local hex = str:match("^[dD][89aAbB]%x%x\\u%x%x%x%x", j + 1)
+                 or str:match("^%x%x%x%x", j + 1)
+                 or decode_error(str, j - 1, "invalid unicode escape in string")
+        res = res .. parse_unicode_escape(hex)
+        j = j + #hex
+      else
+        if not escape_chars[c] then
+          decode_error(str, j - 1, "invalid escape char '" .. c .. "' in string")
+        end
+        res = res .. escape_char_map_inv[c]
+      end
+      k = j + 1
+
+    elseif x == 34 then -- `"`: End of string
+      res = res .. str:sub(k, j - 1)
+      return res, j + 1
+    end
+
+    j = j + 1
+  end
+
+  decode_error(str, i, "expected closing quote for string")
+end
+
+
+local function parse_number(str, i)
+  local x = next_char(str, i, delim_chars)
+  local s = str:sub(i, x - 1)
+  local n = tonumber(s)
+  if not n then
+    decode_error(str, i, "invalid number '" .. s .. "'")
+  end
+  return n, x
+end
+
+
+local function parse_literal(str, i)
+  local x = next_char(str, i, delim_chars)
+  local word = str:sub(i, x - 1)
+  if not literals[word] then
+    decode_error(str, i, "invalid literal '" .. word .. "'")
+  end
+  return literal_map[word], x
+end
+
+
+local function parse_array(str, i)
+  local res = {}
+  local n = 1
+  i = i + 1
+  while 1 do
+    local x
+    i = next_char(str, i, space_chars, true)
+    -- Empty / end of array?
+    if str:sub(i, i) == "]" then
+      i = i + 1
+      break
+    end
+    -- Read token
+    x, i = parse(str, i)
+    res[n] = x
+    n = n + 1
+    -- Next token
+    i = next_char(str, i, space_chars, true)
+    local chr = str:sub(i, i)
+    i = i + 1
+    if chr == "]" then break end
+    if chr ~= "," then decode_error(str, i, "expected ']' or ','") end
+  end
+  return res, i
+end
+
+
+local function parse_object(str, i)
+  local res = {}
+  i = i + 1
+  while 1 do
+    local key, val
+    i = next_char(str, i, space_chars, true)
+    -- Empty / end of object?
+    if str:sub(i, i) == "}" then
+      i = i + 1
+      break
+    end
+    -- Read key
+    if str:sub(i, i) ~= '"' then
+      decode_error(str, i, "expected string for key")
+    end
+    key, i = parse(str, i)
+    -- Read ':' delimiter
+    i = next_char(str, i, space_chars, true)
+    if str:sub(i, i) ~= ":" then
+      decode_error(str, i, "expected ':' after key")
+    end
+    i = next_char(str, i + 1, space_chars, true)
+    -- Read value
+    val, i = parse(str, i)
+    -- Set
+    res[key] = val
+    -- Next token
+    i = next_char(str, i, space_chars, true)
+    local chr = str:sub(i, i)
+    i = i + 1
+    if chr == "}" then break end
+    if chr ~= "," then decode_error(str, i, "expected '}' or ','") end
+  end
+  return res, i
+end
+
+
+local char_func_map = {
+  [ '"' ] = parse_string,
+  [ "0" ] = parse_number,
+  [ "1" ] = parse_number,
+  [ "2" ] = parse_number,
+  [ "3" ] = parse_number,
+  [ "4" ] = parse_number,
+  [ "5" ] = parse_number,
+  [ "6" ] = parse_number,
+  [ "7" ] = parse_number,
+  [ "8" ] = parse_number,
+  [ "9" ] = parse_number,
+  [ "-" ] = parse_number,
+  [ "t" ] = parse_literal,
+  [ "f" ] = parse_literal,
+  [ "n" ] = parse_literal,
+  [ "[" ] = parse_array,
+  [ "{" ] = parse_object,
+}
+
+
+parse = function(str, idx)
+  local chr = str:sub(idx, idx)
+  local f = char_func_map[chr]
+  if f then
+    return f(str, idx)
+  end
+  decode_error(str, idx, "unexpected character '" .. chr .. "'")
+end
+
+
+function json.decode(str)
+  if type(str) ~= "string" then
+    error("expected argument of type string, got " .. type(str))
+  end
+  local res, idx = parse(str, next_char(str, 1, space_chars, true))
+  idx = next_char(str, idx, space_chars, true)
+  if idx <= #str then
+    decode_error(str, idx, "trailing garbage")
+  end
+  return res
+end
+
+
+return json

lua-server/server.fnl

@@ -0,0 +1,112 @@
+;; the server for pond.
+;; 
+;; usage: fennel server.fnl <port>
+;;
+;; test via websocat ws://127.0.0.1:<port>
+
+(local port (or (. arg 1) 0))
+(local http-server (require :http.server))
+(local http-headers (require :http.headers))
+(local websocket (require :http.websocket))
+(local json (require :json))
+
+(fn log [msg]
+  (assert (io.stdout:write (.. "[" (os.date "%d/%b/%Y:%H:%M:%S %z") "] " msg "\n"))))
+
+;; this will be used to generate random names later
+
+(local birbs
+  (with-open [f (io.open "birbs.txt" "r")]
+    (icollect [line (fn [] (f:read))]
+      line)))
+
+(fn table-length [tbl]
+  (accumulate [n 0 _ _ (pairs tbl)] (+ n 1)))
+
+(local open-sockets {})
+
+;; this handler contains the main logic. it is called further down in this
+;; file, as soon as a websocket connection has been established.
+
+(fn handle-websocket [ws]
+  (assert (ws:accept))
+  ; connection is open; pick a random name and make sur eit is not reused
+  (local i (math.random (table-length birbs)))
+  (local name (string.lower (table.remove birbs i)))
+  ; register this socket so other sockets can send messages to it
+  (tset open-sockets name ws)
+  (log (.. name " joined" ))
+  (local greeting (json.encode {:type "presence-information"
+                                :others (- (table-length open-sockets) 1)}))
+  (each [_ ws (pairs open-sockets)]
+    (ws:send greeting))
+  (var closed? false)
+  ; receive loop
+  (while (not closed?)
+    (local (data opcode) (ws:receive))
+    (if data
+      ; handle incoming messages; since this is mostly a relay, we're trying
+      ; to make sure no junk is sent around
+      (do
+        (assert (= opcode :text))
+        (assert (string.match data "ripple"))
+        (assert (< (string.len data) 1000))
+        (log (.. "relaying message for " name ": " data))
+        (each [other-name ws (pairs open-sockets)]
+          (when (not= name other-name)
+            (ws:send data))))
+      ; connection has been closed. time for cleanup
+      (do
+        (log (.. name " left"))
+        (ws:close)
+        (tset open-sockets name nil) ; close connection
+        (local goodbye (json.encode {:type "presence-information"
+                                     :others (- (table-length open-sockets) 1)}))
+        (each [_ ws (pairs open-sockets)]
+          (ws:send goodbye))
+        (table.insert birbs name) ; name is available again
+        (set closed? true)))))
+
+;; this is the low-level server code. it's an adapted version of
+;; https://github.com/daurnimator/lua-http/blob/ddab2835/examples/server_hello.lua
+
+(local server
+  (assert (http-server.listen {:host :localhost
+                               :onerror (fn [server context op err errno]
+                                          (var msg (.. op " on " (tostring context) " failed"))
+                                          (when err
+                                            (set msg (.. msg ": " (tostring err))))
+                                          (assert (io.stderr:write msg "\n")))
+                               :onstream (fn [server stream]
+                                           (let [headers (assert (stream:get_headers))
+                                                 method (headers:get ":method")]
+                                             ;; log request
+                                             (log (string.format "\"%s %s HTTP/%g\"  \"%s\" \"%s\""
+                                                                 (or method "")
+                                                                 (or (headers:get ":path") "")
+                                                                 stream.connection.version
+                                                                 (or (headers:get :referer) "-")
+                                                                 (or (headers:get :user-agent) "-")))
+                                             ;; start and handle websocket connection
+                                             (local ws (websocket.new_from_stream stream headers))
+                                             (if ws
+                                               (handle-websocket ws)
+                                               ;; if we couldn't establish the websocket connection, something's wrong
+                                               (assert (stream:write_headers (doto (http-headers.new)
+                                                                                (: :append ::status :400)) true)))))
+                               : port})))
+
+(assert (server:listen))
+
+(let [(_ _ bound-port) (server:localname)]
+  (log (.. "Now listening on port " bound-port)))
+
+;; automatically start server when run from the command line
+(when (> (length arg) 0)
+  (assert (server:loop)))
+
+(comment
+  ;; run this to handle a response manually
+  (for [i 1 3]
+    (server:step))
+  )