source: DataSource, Frame, SourceConfig and the registry (unused yet)

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

src/source/source_config.hpp

@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2026 Martino Ferrari
+
+#pragma once
+
+#include <string>
+#include <utility>
+#include <vector>
+
+namespace udpscope {
+
+/// A source's settings: an ordered string key/value map. It is the stored form (top-level
+/// `source_opt_<key>` entries of a session), the `--source-opt k=v` form, and what a config form
+/// reads and writes. Order is insertion order, so a stored session stays diff-friendly.
+class SourceConfig {
+ public:
+  using Items = std::vector<std::pair<std::string, std::string>>;
+
+  SourceConfig() = default;
+  explicit SourceConfig(Items items) : items_(std::move(items)) {}
+
+  /// Replaces the value in place if the key exists, else appends.
+  void set(const std::string& key, const std::string& value);
+  bool has(const std::string& key) const;
+  std::string get(const std::string& key, const std::string& def = {}) const;
+  long get_int(const std::string& key, long def) const;
+  double get_double(const std::string& key, double def) const;
+  /// 1/true/yes/on and 0/false/no/off (case-insensitive); anything else gives `def`.
+  bool get_bool(const std::string& key, bool def) const;
+
+  /// Parses `k=v`; false (and no change) if there is no `=` or the key is not `valid_key`.
+  bool parse_assignment(const std::string& kv);
+
+  const Items& items() const noexcept { return items_; }
+  bool empty() const noexcept { return items_.empty(); }
+
+  /// `[A-Za-z0-9_]+` -- the characters that survive as a TOML bare key suffix.
+  static bool valid_key(const std::string& key);
+
+ private:
+  Items items_;
+};
+
+}  // namespace udpscope