add random match-making logic

main-server/app/controllers/api/matchmaking_controller.rb

@@ -0,0 +1,21 @@
+class Api::MatchmakingController < ApplicationController
+  def create
+    result = MatchmakingService.find_match(current_user.id)
+
+    if result
+      render json: {
+        match_id: result[:match_id],
+        game_token: result[:game_token],
+        game_server: result[:game_server],
+        players: result[:players]
+      }
+    else
+      render json: { error: "No opponent found. Try again." }, status: :request_timeout
+    end
+  end
+
+  def destroy
+    MatchmakingService.cancel(current_user.id)
+    render json: { message: "Matchmaking cancelled" }
+  end
+end

main-server/app/services/matchmaking_service.rb

@@ -0,0 +1,122 @@
+class MatchmakingService
+  QUEUE_KEY = "matchmaking:queue"
+  LOCK_KEY = "matchmaking:lock"
+  MATCH_PREFIX = "matchmaking:match:"
+  MATCH_TTL = 60 # seconds
+  POLL_INTERVAL = 0.5 # seconds
+  MAX_WAIT = 30 # seconds
+
+  # Game server to redirect players to (hardcoded for now)
+  GAME_SERVER = ENV.fetch("GAME_SERVER_URL", "ws://game-server.example.com:8080")
+
+  class << self
+    # Main entry point: waits for an opponent and returns match data
+    def find_match(user_id)
+      user_id = user_id.to_i
+
+      # Try to pair with an existing waiting player
+      opponent_id = pop_opponent(user_id)
+
+      if opponent_id
+        create_match(user_id, opponent_id)
+      else
+        # Add self to queue and wait
+        add_to_queue(user_id)
+        wait_for_match(user_id)
+      end
+    end
+
+    # Cancel matchmaking (remove from queue)
+    def cancel(user_id)
+      RedisConnection.with do |redis|
+        redis.lrem(QUEUE_KEY, 0, user_id)
+      end
+    end
+
+    private
+
+    # Atomically pop an opponent from the queue (excluding self)
+    def pop_opponent(user_id)
+      RedisConnection.with do |redis|
+        redis.watch(QUEUE_KEY) do
+          queue = redis.lrange(QUEUE_KEY, 0, -1)
+          opponent = queue.find { |id| id.to_i != user_id }
+
+          if opponent
+            result = redis.multi do |tx|
+              tx.lrem(QUEUE_KEY, 0, opponent)
+            end
+            return opponent.to_i if result&.first&.positive?
+          else
+            redis.unwatch
+          end
+        end
+      end
+      nil
+    end
+
+    def add_to_queue(user_id)
+      RedisConnection.with do |redis|
+        # Remove any stale entries first
+        redis.lrem(QUEUE_KEY, 0, user_id)
+        redis.rpush(QUEUE_KEY, user_id)
+      end
+    end
+
+    def wait_for_match(user_id)
+      start_time = Time.current
+      match_id = nil
+
+      while Time.current - start_time < MAX_WAIT
+        RedisConnection.with do |redis|
+          match_id = redis.get("#{MATCH_PREFIX}#{user_id}")
+        end
+        break if match_id
+
+        sleep POLL_INTERVAL
+      end
+
+      if match_id
+        # Retrieve and delete the match data
+        data = nil
+        RedisConnection.with do |redis|
+          data = redis.get("#{MATCH_PREFIX}match:#{match_id}")
+          redis.del("#{MATCH_PREFIX}#{user_id}")
+          redis.del("#{MATCH_PREFIX}match:#{match_id}")
+        end
+        JSON.parse(data, symbolize_names: true) if data
+      else
+        # Timeout: remove from queue
+        cancel(user_id)
+        nil
+      end
+    end
+
+    def create_match(player1_id, player2_id)
+      match_id = SecureRandom.uuid
+      game_token = JwtService.encode(
+        match_id: match_id,
+        player1_id: player1_id,
+        player2_id: player2_id,
+        game_server: GAME_SERVER,
+        exp: 1.hour.from_now.to_i
+      )
+
+      match_data = {
+        match_id: match_id,
+        game_token: game_token,
+        game_server: GAME_SERVER,
+        players: [player1_id, player2_id]
+      }
+
+      # Store match data for both players
+      RedisConnection.with do |redis|
+        redis.set("#{MATCH_PREFIX}match:#{match_id}", match_data.to_json, ex: MATCH_TTL)
+        redis.set("#{MATCH_PREFIX}#{player1_id}", match_id, ex: MATCH_TTL)
+        redis.set("#{MATCH_PREFIX}#{player2_id}", match_id, ex: MATCH_TTL)
+      end
+
+      match_data
+    end
+  end
+end