[dynamic control] Add SourceKind as sources are a known list

dynamic-control/src/main/java/io/opentelemetry/contrib/dynamic/policy/source/SourceKind.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.dynamic.policy.source;
+
+import java.util.Locale;
+import java.util.Objects;
+
+/**
+ * Identifies where policy configuration is loaded from for registry initialization (e.g. local
+ * file, OpAMP, HTTP). Distinct from {@link SourceFormat}, which describes how individual policy
+ * lines or payloads are encoded (key-value vs JSON).
+ */
+public enum SourceKind {
+  /** Policies loaded from a local file (e.g. line-per-policy file). */
+  FILE("file"),
+
+  /** Policies delivered via OpAMP (remote management). */
+  OPAMP("opamp"),
+
+  /** Policies fetched from an HTTP/HTTPS endpoint. */
+  HTTP("http"),
+
+  /** User-defined or extension provider. */
+  CUSTOM("custom");
+
+  private final String configValue;
+
+  SourceKind(String configValue) {
+    this.configValue = configValue;
+  }
+
+  /**
+   * Stable string used in registry JSON configuration (lowercase).
+   *
+   * @return the config value for this kind
+   */
+  public String configValue() {
+    return configValue;
+  }
+
+  /**
+   * Parses the value used in JSON configuration. Leading and trailing whitespace is removed, then
+   * the remainder is matched case-insensitively against {@link #configValue()} for each kind.
+   *
+   * @param value the string from config (e.g. {@code "file"}, {@code "OPAMP"})
+   * @return the matching kind
+   * @throws NullPointerException if value is null
+   * @throws IllegalArgumentException if no kind matches the trimmed value
+   */
+  public static SourceKind fromConfigValue(String value) {
+    Objects.requireNonNull(value, "value cannot be null");
+    String normalized = value.trim().toLowerCase(Locale.ROOT);
+    for (SourceKind kind : values()) {
+      if (kind.configValue.equals(normalized)) {
+        return kind;
+      }
+    }
+    throw new IllegalArgumentException("Unknown source kind: " + value);
+  }
+}

dynamic-control/src/test/java/io/opentelemetry/contrib/dynamic/policy/source/SourceKindTest.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.dynamic.policy.source;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import org.junit.jupiter.api.Test;
+
+class SourceKindTest {
+
+  @Test
+  void configValuesAreStableLowercase() {
+    assertThat(SourceKind.FILE.configValue()).isEqualTo("file");
+    assertThat(SourceKind.OPAMP.configValue()).isEqualTo("opamp");
+    assertThat(SourceKind.HTTP.configValue()).isEqualTo("http");
+    assertThat(SourceKind.CUSTOM.configValue()).isEqualTo("custom");
+  }
+
+  @Test
+  void fromConfigValueParsesCaseInsensitive() {
+    assertThat(SourceKind.fromConfigValue("FILE")).isEqualTo(SourceKind.FILE);
+    assertThat(SourceKind.fromConfigValue("Opamp")).isEqualTo(SourceKind.OPAMP);
+  }
+
+  @Test
+  void fromConfigValueTrimsWhitespace() {
+    assertThat(SourceKind.fromConfigValue("  http  ")).isEqualTo(SourceKind.HTTP);
+  }
+
+  @Test
+  void fromConfigValueRejectsNullInput() {
+    assertThatThrownBy(() -> SourceKind.fromConfigValue(null))
+        .isInstanceOf(NullPointerException.class)
+        .hasMessage("value cannot be null");
+  }
+
+  @Test
+  void fromConfigValueRejectsUnknownValue() {
+    assertThatThrownBy(() -> SourceKind.fromConfigValue("unknown"))
+        .isInstanceOf(IllegalArgumentException.class)
+        .hasMessage("Unknown source kind: unknown");
+  }
+}