Initial commit: extracted from impostor-bbs gems/bbs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/bbs/store.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'csv'
+require 'fileutils'
+require 'time'
+
+module BBS
+  class Store
+    def initialize(path:, headers:)
+      @path    = path
+      @headers = headers
+      @mutex   = Mutex.new
+    end
+
+    def upsert(session_id:, **fields)
+      @mutex.synchronize do
+        ensure_file!
+        rows = CSV.read(@path, headers: true)
+        row  = rows.find { |r| r['session_id'] == session_id }
+
+        if row
+          fields.each { |k, v| row[k.to_s] = v }
+        else
+          values = @headers.map do |h|
+            case h
+            when 'session_id' then session_id
+            when 'timestamp'  then Time.now.utc.iso8601
+            else fields[h.to_sym]
+            end
+          end
+          rows << CSV::Row.new(@headers, values)
+        end
+
+        CSV.open(@path, 'w') do |csv|
+          csv << @headers
+          rows.each { |r| csv << r.fields }
+        end
+      end
+    end
+
+    private
+
+    def ensure_file!
+      FileUtils.mkdir_p(File.dirname(@path))
+      return if File.exist?(@path)
+      CSV.open(@path, 'w') { |csv| csv << @headers }
+    end
+  end
+end