[magnusp]

Fixes #212

What changed

LibsqlPreparedStatement now holds one cached ParameterMetaDataView (package-private, new file) that owns the parameter count and the closed and index checks. getParameterMetaData() returns that view. The statement keeps implements ParameterMetaData and delegates the nine interface methods, so instanceof ParameterMetaData still holds for a prepared statement. The parameter-metadata paragraph moved from the statement's javadoc to the view.

Behavior preserved

• getParameterMetaData() still throws after close, and metadata calls on a view taken before close still throw after close, because the view checks the owning statement.
• Index message unchanged: Parameter index out of range: N.
• Count still comes from SqlTokenizer.placeholderCount.
• ParameterMetaData extends Wrapper, so the view delegates unwrap/isWrapperFor to the statement; unwrapping still reaches the statement.
• No existing test edited, no message changed, pom.xml untouched.

Pins added

A follow-up commit, test(jdbc): pin parameter metadata invariants, adds seven characterization tests so the invariants above are enforced rather than asserted in prose. The class goes from 22 to 29 tests; the additions are pure insertions, with no existing assertion edited.

#	Test	Pinned behavior
1	getParameterMetaDataReturnsAViewWithThePlaceholderCount	View is non-null and getParameterCount() equals the placeholder count (2 for two ?).
2	getParameterMetaDataAfterCloseThrows	getParameterMetaData() after close() throws SQLException: Statement is closed.
3	parameterMetadataViewTakenBeforeCloseStillThrowsAfterClose	A view obtained before close() throws from both getParameterCount() and getParameterType(1) afterwards.
4	parameterMetadataRejectsAnOutOfRangeIndex	Index 0 throws SQLException with the exact message Parameter index out of range: 0.
5	preparedStatementRemainsAParameterMetaData	statement instanceof ParameterMetaData holds.
6	getParameterMetaDataReturnsTheSameCachedView	Two calls return the same instance, proving the view is cached.
7	parameterMetadataUnwrapReachesTheStatement	Today's behavior pinned: isWrapperFor(ParameterMetaData.class) is true and unwrap(ParameterMetaData.class) returns the statement itself, because the view delegates to the statement's wrapper surface.

Mutant kills

Each mutation was made as a scratch edit, the test class was run, and the edit was reverted to a clean tree before committing.

Scratch mutation	Result
Index message changed to Parameter index out of range [N]	parameterMetadataRejectsAnOutOfRangeIndex failed: expected Parameter index out of range: 0, got Parameter index out of range [0].
Closed checks removed from getParameterMetaData() and from the view's getParameterCount()/checkParameterIndex()	getParameterMetaDataAfterCloseThrows and parameterMetadataViewTakenBeforeCloseStillThrowsAfterClose both failed.

Diff

 .../jdbc/LibsqlPreparedStatement.java              | 87 ++++--------------------
 .../jdbc/ParameterMetaDataView.java                | 98 +++++++++++++++++++++++
 .../jdbc/LibsqlPreparedStatementTest.java          | 86 ++++++++++++++++++++++
 3 files changed, 200 insertions(+), 71 deletions(-)

Line counts

• LibsqlPreparedStatement.java: 614 -> 559 lines (limit: under 560).
• ParameterMetaDataView.java: 98 lines (new).

Probe

Inverted the closed check in ParameterMetaDataView.getParameterCount() so it threw while the statement was open. LibsqlPreparedStatementTest.parameterCountComesFromThePlaceholders failed at LibsqlPreparedStatementTest.java:265 with java.sql.SQLException: Statement is closed. Reverted; the same class then ran 22/22 green.

Lanes

Lane	Command	Result
unit	./mvnw -pl libsql-jdbc -am test	405 tests, 0 failures (baseline 398; +7 pins)
spotless apply	./mvnw spotless:apply	BUILD SUCCESS (no reformat)
spotless	./mvnw spotless:check	BUILD SUCCESS
conformance	./mvnw -pl libsql-conformance -am verify	272 tests, 0 failures, 7 skipped (baseline 272)
itests	DOCKER_CONFIG="$PWD/libsql-conformance/src/test/docker-config" ./mvnw -pl libsql-itests -am verify	43 tests, 0 failures (baseline 43)