hayson-binding-shared 0.11.0

use std::io;
use std::path::Path;

use hayson_engine::atomic::AtomicTemporaryFileError;
use hayson_engine::catalog::MigrateFormat1Error;
use hayson_engine::database::DatabaseError;
use hayson_engine::errors::{HaysonCipherError, HaysonIndexMismatchError, HaysonLogReplacedError};
use hayson_engine::lock::{DirLockError, LockedError};
use hayson_engine::table::TableError;
use hayson_engine::txn::TxnError;
use serde_json::{json, Map, Value};

/// Envelope version of the JSON carried in every thrown `Error.message`. Bumped only if the shape
/// below changes incompatibly — the TS shim reads it before trusting `code`.
pub const ENVELOPE_VERSION: u64 = 1;

/// Stable, machine-readable tags a TS shim switches on to re-throw the matching `HaysonXxxError`.
/// Every `DatabaseError`/`TableError` variant maps onto exactly one of these.
pub mod code {
    pub const VALIDATION: &str = "Validation";
    pub const UNIQUE_VIOLATION: &str = "UniqueViolation";
    pub const PENDING_CONFLICT: &str = "PendingConflict";
    pub const NOT_FOUND: &str = "NotFound";
    pub const SCHEMA: &str = "Schema";
    pub const PARTITION: &str = "Partition";
    pub const RELATION_VIOLATION: &str = "RelationViolation";
    pub const RELATION_RESTRICT: &str = "RelationRestrict";
    pub const CIPHER: &str = "Cipher";
    pub const LOCKED: &str = "Locked";
    pub const LOCK_LOST: &str = "LockLost";
    pub const SUSPICIOUS_LOCK_FILE: &str = "SuspiciousLockFile";
    pub const READ_ONLY: &str = "ReadOnly";
    pub const FIELD_IN_USE: &str = "FieldInUse";
    pub const CATALOG: &str = "Catalog";
    pub const TXN: &str = "Txn";
    pub const INDEX_MISMATCH: &str = "IndexMismatch";
    pub const LOG_REPLACED: &str = "LogReplaced";
    pub const TEMPORARY_FILE: &str = "TemporaryFile";
    pub const IO: &str = "Io";
    pub const INVALID_JSON: &str = "InvalidJson";
    pub const CLOSED: &str = "Closed";
}

fn envelope(code: &str, message: String, fields: Map<String, Value>) -> Value {
    let mut object = Map::new();
    object.insert("envelopeVersion".to_string(), json!(ENVELOPE_VERSION));
    object.insert("code".to_string(), json!(code));
    object.insert("message".to_string(), json!(message));
    for (key, value) in fields {
        object.insert(key, value);
    }
    Value::Object(object)
}

fn no_fields() -> Map<String, Value> {
    Map::new()
}

fn fields(pairs: Value) -> Map<String, Value> {
    match pairs {
        Value::Object(map) => map,
        _ => Map::new(),
    }
}

fn describe_cipher_error(error: &HaysonCipherError) -> Value {
    envelope(
        code::CIPHER,
        error.to_string(),
        fields(json!({
            "table": error.table,
            "field": error.field,
            "reason": error.reason,
            "keyId": error.key_id,
        })),
    )
}

fn describe_locked_error(error: &LockedError) -> Value {
    // NOTE: `subject` is the database directory, not the lock file — `DirLock::acquire` takes the
    // parent of the path it was given before building this error.
    let dir = error.subject.display().to_string();
    let holder = error.holder.as_ref().map(|holder| {
        json!({
            "owner": holder.owner,
            "pid": holder.pid,
            "host": holder.host,
            "startedAt": holder.started_at,
            "heartbeatAt": holder.heartbeat_at,
        })
    });
    envelope(
        code::LOCKED,
        error.to_string(),
        fields(json!({ "dir": dir, "holder": holder, "waitedMs": error.waited_ms })),
    )
}

/// `table` is the name the call was made against — `TableError` itself carries one only on the
/// variants built from a `HaysonXxxError`, and even then not on `Io`.
pub fn describe_table_error(table: &str, error: &TableError) -> Value {
    let message = error.to_string();
    match error {
        TableError::Validation(inner) => envelope(
            code::VALIDATION,
            message,
            fields(json!({
                "table": inner.table,
                "issues": inner
                    .issues
                    .iter()
                    .map(|issue| json!({ "field": issue.field, "reason": issue.reason }))
                    .collect::<Vec<_>>(),
            })),
        ),
        TableError::Unique(inner) => envelope(
            code::UNIQUE_VIOLATION,
            message,
            fields(json!({ "table": inner.table, "field": inner.field, "holder": inner.holder })),
        ),
        TableError::Conflict(inner) => envelope(
            code::PENDING_CONFLICT,
            message,
            fields(json!({ "table": inner.table, "key": inner.key, "fields": inner.fields })),
        ),
        TableError::NotFound(inner) => envelope(
            code::NOT_FOUND,
            message,
            fields(json!({ "table": inner.table, "key": inner.key })),
        ),
        TableError::Schema(_) => envelope(code::SCHEMA, message, fields(json!({ "table": table }))),
        TableError::Partition(inner) => envelope(
            code::PARTITION,
            message,
            fields(json!({ "table": inner.table, "field": inner.field, "reason": inner.reason })),
        ),
        TableError::Relation(inner) => envelope(
            code::RELATION_VIOLATION,
            message,
            fields(json!({
                "relation": inner.relation,
                "table": inner.table,
                "field": inner.field,
                "value": inner.value,
            })),
        ),
        TableError::RelationRestrict(inner) => envelope(
            code::RELATION_RESTRICT,
            message,
            fields(json!({
                "relation": inner.relation,
                "table": inner.table,
                "key": inner.key,
                "referencingTable": inner.referencing_table,
                "referencingField": inner.referencing_field,
                "referencing": inner.referencing,
            })),
        ),
        TableError::Cipher(inner) => describe_cipher_error(inner),
        TableError::Io(inner) => describe_io_error(inner),
    }
}

/// `checkpoint::restore_or_rebuild` reports a snapshot paired with a different log through
/// `io::Error::other`, so the typed refusal survives only as the boxed source of that io error.
/// Without this the shim sees `Io` and cannot tell the index-mismatch refusal from a disk failure.
fn index_mismatch_of(error: &io::Error) -> Option<&HaysonIndexMismatchError> {
    error.get_ref()?.downcast_ref::<HaysonIndexMismatchError>()
}

fn log_replaced_of(error: &io::Error) -> Option<&HaysonLogReplacedError> {
    error.get_ref()?.downcast_ref::<HaysonLogReplacedError>()
}

/// `atomic::open_temporary` refuses a `.tmp` path it could not claim through an `io::Error` that
/// boxes the typed refusal, so the path and the reason survive only as that boxed source. Without
/// this the shim sees `Io` — or, on a catalog write, `Catalog` — and the caller loses the one file
/// it has to remove before retrying.
fn temporary_file_of(error: &io::Error) -> Option<&AtomicTemporaryFileError> {
    AtomicTemporaryFileError::downcast(error)
}

pub fn describe_io_error(error: &io::Error) -> Value {
    if let Some(inner) = temporary_file_of(error) {
        return envelope(
            code::TEMPORARY_FILE,
            error.to_string(),
            fields(json!({
                "path": inner.path.display().to_string(),
                "reason": inner.reason,
            })),
        );
    }
    if let Some(inner) = log_replaced_of(error) {
        return envelope(
            code::LOG_REPLACED,
            error.to_string(),
            fields(json!({ "path": inner.path })),
        );
    }
    if let Some(inner) = index_mismatch_of(error) {
        return envelope(
            code::INDEX_MISMATCH,
            error.to_string(),
            fields(json!({
                "indexPath": inner.path,
                "logPath": inner.log_path,
                "watermark": inner.watermark,
                "expectedHash": inner.expected_hash,
                "actualHash": inner.actual_hash,
            })),
        );
    }
    envelope(
        code::IO,
        error.to_string(),
        fields(json!({ "kind": format!("{:?}", error.kind()) })),
    )
}

/// The errno name a host raised in a language whose IO errors carry one — Node reports it as
/// `error.code`, and a caller that means to tell "this file is gone" from "this file is unreadable"
/// has nothing else to go on. `None` for a kind with no single portable name, in which case the
/// envelope simply omits it rather than guessing.
fn errno_name_of(error: &io::Error) -> Option<&'static str> {
    match error.kind() {
        io::ErrorKind::NotFound => Some("ENOENT"),
        io::ErrorKind::PermissionDenied => Some("EACCES"),
        _ => None,
    }
}

/// A [`describe_io_error`] that knows which file failed. `io::Error` carries no path, so only a
/// call site that kept one can produce this — today `DatabaseError::Log`, raised by the readonly
/// open probing the logs it is about to take on.
fn describe_log_io_error(path: &Path, error: &io::Error) -> Value {
    let mut described = fields(json!({
        "kind": format!("{:?}", error.kind()),
        "path": path.display().to_string(),
    }));
    if let Some(name) = errno_name_of(error) {
        described.insert("errnoCode".to_string(), json!(name));
    }
    envelope(code::IO, format!("{error}, open \"{}\"", path.display()), described)
}

/// Public because a binding raises `TxnError::AlreadyCommitted` itself: a unit of work handed to
/// the engine is consumed there, so a second call on the same host-side handle never reaches the
/// engine to be refused by it.
pub fn describe_txn_error(error: &TxnError) -> Value {
    match error {
        TxnError::Table(name, inner) => describe_table_error(name, inner),
        TxnError::Io(inner) => describe_io_error(inner),
        TxnError::UnknownTable(name) => envelope(code::NOT_FOUND, error.to_string(), fields(json!({ "table": name }))),
        TxnError::AlreadyCommitted | TxnError::JournalPending(_) => envelope(code::TXN, error.to_string(), no_fields()),
    }
}

pub fn describe_database_error(error: &DatabaseError) -> Value {
    let message = error.to_string();
    match error {
        DatabaseError::Lock(DirLockError::Locked(inner)) => describe_locked_error(inner),
        DatabaseError::Lock(DirLockError::Lost(path)) => envelope(
            code::LOCK_LOST,
            message,
            fields(json!({ "lockPath": path.display().to_string() })),
        ),
        DatabaseError::Lock(DirLockError::SuspiciousLockFile(path)) => envelope(
            code::SUSPICIOUS_LOCK_FILE,
            message,
            fields(json!({ "lockPath": path.display().to_string() })),
        ),
        DatabaseError::Lock(DirLockError::Io(inner)) => describe_io_error(inner),
        DatabaseError::Schema(_) => envelope(code::SCHEMA, message, no_fields()),
        DatabaseError::ReadOnly { dir, operation } => envelope(
            code::READ_ONLY,
            message,
            fields(json!({ "dir": dir.display().to_string(), "operation": operation })),
        ),
        DatabaseError::FieldInUse { table, field, records } => envelope(
            code::FIELD_IN_USE,
            message,
            fields(json!({ "table": table, "field": field, "records": records })),
        ),
        DatabaseError::Catalog(_) => envelope(code::CATALOG, message, no_fields()),
        DatabaseError::Io(inner) => describe_io_error(inner),
        DatabaseError::Log(path, inner) => describe_log_io_error(path, inner),
        DatabaseError::Table(name, inner) => describe_table_error(name, inner),
        DatabaseError::Txn(inner) => describe_txn_error(inner),
        DatabaseError::Cipher(inner) => describe_cipher_error(inner),
    }
}

pub fn describe_migrate_format1_error(error: &MigrateFormat1Error) -> Value {
    let message = error.to_string();
    match error {
        MigrateFormat1Error::Schema(_) | MigrateFormat1Error::Write(_) => envelope(code::SCHEMA, message, no_fields()),
        MigrateFormat1Error::Io(inner) => describe_io_error(inner),
        MigrateFormat1Error::NotADirectory(path)
        | MigrateFormat1Error::UnreadableMarker(path, _)
        | MigrateFormat1Error::UnknownMarker(path, _)
        | MigrateFormat1Error::NoSchemaFiles(path) => envelope(
            code::SCHEMA,
            message,
            fields(json!({ "path": path.display().to_string() })),
        ),
    }
}

pub fn describe_invalid_json(what: &str, error: &serde_json::Error) -> Value {
    envelope(
        code::INVALID_JSON,
        format!("{what} is not valid JSON: {error}"),
        fields(json!({ "argument": what })),
    )
}

pub fn describe_unknown_table(table: &str, dir: &str) -> Value {
    envelope(
        code::NOT_FOUND,
        format!("table \"{table}\" does not exist in \"{dir}\""),
        fields(json!({ "table": table, "dir": dir })),
    )
}

pub fn describe_closed(operation: &str) -> Value {
    envelope(
        code::CLOSED,
        format!("{operation} was called after the database was closed"),
        fields(json!({ "operation": operation })),
    )
}

/// Free-form refusals raised by this binding itself (a malformed `open` option, an unusable key).
pub fn describe_schema(message: String) -> Value {
    envelope(code::SCHEMA, message, no_fields())
}

pub fn describe_cipher_config(message: String) -> Value {
    envelope(code::CIPHER, message, fields(json!({ "table": "", "field": "" })))
}

#[cfg(test)]
mod tests {
    use hayson_engine::errors::{
        HaysonNotFoundError, HaysonPartitionError, HaysonSchemaError, HaysonUniqueViolationError,
        HaysonValidationError, ValidationIssue,
    };
    use hayson_engine::lock::LockHolder;
    use std::path::PathBuf;

    use super::*;

    fn scratch_dir(prefix: &str) -> PathBuf {
        let dir = std::env::temp_dir().join(format!(
            "{prefix}{}-{}",
            std::process::id(),
            std::time::SystemTime::now()
                .duration_since(std::time::UNIX_EPOCH)
                .unwrap()
                .as_nanos()
        ));
        std::fs::create_dir_all(&dir).unwrap();
        dir
    }

    fn code_of(value: &Value) -> &str {
        value.get("code").and_then(Value::as_str).unwrap()
    }

    #[test]
    fn a_validation_error_carries_every_issue_the_shim_needs_to_rebuild_it() {
        let error = TableError::Validation(HaysonValidationError {
            table: "users".into(),
            issues: vec![ValidationIssue {
                field: "name".into(),
                reason: "is required".into(),
            }],
        });

        let described = describe_table_error("users", &error);

        assert_eq!(code_of(&described), code::VALIDATION);
        assert_eq!(described["table"], json!("users"));
        assert_eq!(
            described["issues"],
            json!([{ "field": "name", "reason": "is required" }])
        );
        assert_eq!(described["envelopeVersion"], json!(ENVELOPE_VERSION));
        assert_eq!(described["message"], json!(error.to_string()));
    }

    #[test]
    fn a_unique_violation_names_the_field_and_the_key_already_holding_it() {
        let error = TableError::Unique(HaysonUniqueViolationError {
            table: "users".into(),
            field: "email".into(),
            holder: "u1".into(),
        });

        let described = describe_table_error("users", &error);

        assert_eq!(code_of(&described), code::UNIQUE_VIOLATION);
        assert_eq!(described["field"], json!("email"));
        assert_eq!(described["holder"], json!("u1"));
    }

    #[test]
    fn a_not_found_error_keeps_the_table_and_key_apart_from_the_message() {
        let error = TableError::NotFound(HaysonNotFoundError {
            table: "users".into(),
            key: "u9".into(),
        });

        let described = describe_table_error("users", &error);

        assert_eq!(code_of(&described), code::NOT_FOUND);
        assert_eq!(described["key"], json!("u9"));
    }

    #[test]
    fn a_partition_error_is_tagged_apart_from_a_plain_schema_rejection() {
        let partition = TableError::Partition(HaysonPartitionError::new("events", "day", "is empty"));
        let schema = TableError::Schema(HaysonSchemaError("no".into()));

        assert_eq!(code_of(&describe_table_error("events", &partition)), code::PARTITION);
        assert_eq!(code_of(&describe_table_error("events", &schema)), code::SCHEMA);
    }

    #[test]
    fn a_cipher_error_carries_the_key_id_it_could_not_use() {
        let error = TableError::Cipher(Box::new(
            HaysonCipherError::new("secrets", "token", "cannot be opened").with_key_id("k2"),
        ));

        let described = describe_table_error("secrets", &error);

        assert_eq!(code_of(&described), code::CIPHER);
        assert_eq!(described["keyId"], json!("k2"));
        assert_eq!(described["field"], json!("token"));
    }

    #[test]
    fn a_locked_database_reports_the_directory_the_holder_and_how_long_we_waited() {
        let error = DatabaseError::Lock(DirLockError::Locked(LockedError {
            // `DirLock::acquire` stores the directory here, not the `.hayson.lock` inside it.
            subject: PathBuf::from("/data/db"),
            holder: Some(LockHolder {
                owner: "0f1e2d3c".into(),
                pid: Some(42),
                host: Some("box".into()),
                started_at: 10,
                heartbeat_at: 20,
            }),
            waited_ms: 250,
        }));

        let described = describe_database_error(&error);

        assert_eq!(code_of(&described), code::LOCKED);
        assert_eq!(described["dir"], json!("/data/db"));
        assert_eq!(described["waitedMs"], json!(250));
        assert_eq!(described["holder"]["owner"], json!("0f1e2d3c"));
        assert_eq!(described["holder"]["pid"], json!(42));
        assert_eq!(described["holder"]["startedAt"], json!(10));
    }

    #[test]
    fn a_lock_taken_over_by_another_writer_reports_the_lock_path_under_its_own_code() {
        let error = DatabaseError::Lock(DirLockError::Lost(PathBuf::from("/data/db/.hayson.lock")));

        let described = describe_database_error(&error);

        assert_eq!(code_of(&described), code::LOCK_LOST);
        assert_eq!(described["lockPath"], json!("/data/db/.hayson.lock"));
    }

    #[test]
    fn a_symlink_planted_at_the_lock_path_reports_the_lock_path_under_its_own_code() {
        let error = DatabaseError::Lock(DirLockError::SuspiciousLockFile(PathBuf::from("/data/db/.hayson.lock")));

        let described = describe_database_error(&error);

        assert_eq!(code_of(&described), code::SUSPICIOUS_LOCK_FILE);
        assert_eq!(described["lockPath"], json!("/data/db/.hayson.lock"));
    }

    #[test]
    fn a_readonly_refusal_is_told_apart_from_a_genuine_schema_error() {
        let readonly = DatabaseError::ReadOnly {
            dir: PathBuf::from("/data/db"),
            operation: "createTable".into(),
        };
        let genuine = DatabaseError::Schema(HaysonSchemaError("field \"id\" has no type".into()));

        let described = describe_database_error(&readonly);
        assert_eq!(code_of(&described), code::READ_ONLY);
        assert_eq!(described["operation"], json!("createTable"));
        assert_eq!(described["dir"], json!("/data/db"));

        assert_eq!(code_of(&describe_database_error(&genuine)), code::SCHEMA);
    }

    #[test]
    fn a_residual_field_refusal_is_told_apart_from_a_plain_catalog_error() {
        let in_use = DatabaseError::FieldInUse {
            table: "users".into(),
            field: "name".into(),
            records: 3,
        };
        let plain = DatabaseError::Catalog("table \"ghost\" does not exist in \"/data/db\"".into());

        let described = describe_database_error(&in_use);
        assert_eq!(code_of(&described), code::FIELD_IN_USE);
        assert_eq!(described["table"], json!("users"));
        assert_eq!(described["field"], json!("name"));
        assert_eq!(described["records"], json!(3));

        assert_eq!(code_of(&describe_database_error(&plain)), code::CATALOG);
    }

    #[test]
    fn a_table_scoped_database_error_is_described_as_its_inner_table_error() {
        let error = DatabaseError::Table(
            "users".into(),
            TableError::NotFound(HaysonNotFoundError {
                table: "users".into(),
                key: "u9".into(),
            }),
        );

        assert_eq!(code_of(&describe_database_error(&error)), code::NOT_FOUND);
    }

    #[test]
    fn an_unknown_table_inside_a_unit_of_work_is_reported_as_not_found() {
        let error = DatabaseError::Txn(TxnError::UnknownTable("ghost".into()));

        let described = describe_database_error(&error);

        assert_eq!(code_of(&described), code::NOT_FOUND);
        assert_eq!(described["table"], json!("ghost"));
    }

    #[test]
    fn an_io_failure_keeps_its_kind_so_the_shim_can_tell_missing_from_denied() {
        let error = DatabaseError::Io(io::Error::new(io::ErrorKind::PermissionDenied, "nope"));

        let described = describe_database_error(&error);

        assert_eq!(code_of(&described), code::IO);
        assert_eq!(described["kind"], json!("PermissionDenied"));
    }

    #[test]
    fn an_io_failure_the_engine_could_name_a_file_for_carries_the_path_and_the_errno_name() {
        let error = DatabaseError::Log(
            PathBuf::from("/data/db/notes/note.jsonl"),
            io::Error::from(io::ErrorKind::NotFound),
        );

        let described = describe_database_error(&error);

        assert_eq!(code_of(&described), code::IO);
        assert_eq!(described["path"], json!("/data/db/notes/note.jsonl"));
        assert_eq!(described["errnoCode"], json!("ENOENT"));
    }

    #[test]
    fn an_io_kind_with_no_portable_errno_name_leaves_the_field_out_rather_than_guessing() {
        let error = DatabaseError::Log(
            PathBuf::from("/data/db/notes.jsonl"),
            io::Error::new(io::ErrorKind::InvalidData, "garbled"),
        );

        let described = describe_database_error(&error);

        assert_eq!(described["path"], json!("/data/db/notes.jsonl"));
        assert!(described.get("errnoCode").is_none(), "{described}");
    }

    #[test]
    fn a_read_that_failed_to_decrypt_arrives_typed_with_the_key_id_the_flattened_text_used_to_lose() {
        let error = TableError::Cipher(Box::new(
            HaysonCipherError::new("secrets", "token", "was written with key \"k1\", which is not on hand")
                .with_key_id("k1"),
        ));

        let described = describe_table_error("secrets", &error);

        assert_eq!(code_of(&described), code::CIPHER);
        assert_eq!(described["table"], json!("secrets"));
        assert_eq!(described["field"], json!("token"));
        assert_eq!(described["keyId"], json!("k1"));
    }

    #[test]
    fn an_io_failure_on_a_read_stays_an_io_failure_now_that_nothing_reads_its_text() {
        let corrupt = TableError::Io(io::Error::new(
            io::ErrorKind::InvalidData,
            "log \"a.jsonl\" is corrupt at offset 12",
        ));

        assert_eq!(code_of(&describe_table_error("notes", &corrupt)), code::IO);
    }

    #[test]
    fn a_search_against_a_table_with_no_fulltext_field_arrives_as_a_typed_schema_refusal() {
        let error = TableError::Schema(HaysonSchemaError(
            "table \"users\" has no field marked \"fulltext\": true — search is not available".into(),
        ));

        let described = describe_table_error("users", &error);

        assert_eq!(code_of(&described), code::SCHEMA);
        assert_eq!(described["table"], json!("users"));
    }

    #[test]
    fn a_write_onto_a_replaced_log_travels_under_its_own_code_with_the_path() {
        let error = TableError::Io(io::Error::other(HaysonLogReplacedError {
            path: "/data/db/users.jsonl".into(),
        }));

        let described = describe_table_error("users", &error);

        assert_eq!(code_of(&described), code::LOG_REPLACED);
        assert_eq!(described["path"], json!("/data/db/users.jsonl"));
        assert_eq!(described["message"], json!(error.to_string()));
    }

    #[test]
    fn a_refused_index_snapshot_travels_under_its_own_code_with_both_paths_and_the_watermark() {
        let error = DatabaseError::Io(io::Error::other(HaysonIndexMismatchError {
            path: "/data/db/users.idx".into(),
            log_path: "/data/db/users.jsonl".into(),
            watermark: 397,
            expected_hash: "9f2c000000000000".into(),
            actual_hash: "4b1e000000000000".into(),
        }));

        let described = describe_database_error(&error);

        assert_eq!(code_of(&described), code::INDEX_MISMATCH);
        assert_eq!(described["indexPath"], json!("/data/db/users.idx"));
        assert_eq!(described["logPath"], json!("/data/db/users.jsonl"));
        assert_eq!(described["watermark"], json!(397));
        assert_eq!(described["expectedHash"], json!("9f2c000000000000"));
        assert_eq!(described["actualHash"], json!("4b1e000000000000"));
        assert_eq!(described["message"], json!(error.to_string()));
    }

    #[test]
    fn a_temporary_path_that_could_not_be_claimed_travels_under_its_own_code_with_path_and_reason() {
        let dir = scratch_dir("hayson-envelope-temporary-");
        // A directory on the .tmp path: open_exclusive reports AlreadyExists and remove_file cannot
        // clear it, which is the shape of the refusal a catalog write hits on EISDIR.
        let temporary = dir.join("hayson.json.tmp");
        std::fs::create_dir(&temporary).unwrap();
        let refusal = hayson_engine::atomic::open_temporary(&temporary, None).unwrap_err();
        let message = refusal.to_string();
        let error = DatabaseError::Io(refusal);

        let described = describe_database_error(&error);
        std::fs::remove_dir_all(&dir).unwrap();

        assert_eq!(code_of(&described), code::TEMPORARY_FILE);
        assert_eq!(described["path"], json!(temporary.display().to_string()));
        assert_eq!(described["reason"], json!("is in the way and could not be cleared, so nothing on disk was changed — remove whatever holds that path and retry"));
        assert_eq!(described["message"], json!(message));
    }

    #[test]
    fn an_io_error_that_boxes_nothing_typed_is_still_reported_as_io() {
        let error = io::Error::other("snapshot \"a.idx\" claims watermark and schema match the log");

        assert_eq!(code_of(&describe_io_error(&error)), code::IO);
    }
}