/**
 * Legacy-backup walker for `cleo doctor legacy-backups`.
 *
 * Enumerates every `*-pre-cleo.db.bak`, `brain.db.PRE-DUP-FIX-*`,
 * `*.pre-untrack-*`, and overflow `.cleo/backups/sqlite/*.db` artefact
 * across:
 *
 *   - `<projectRoot>/.cleo/quarantine/`     (NEVER auto-pruned)
 *   - `<projectRoot>/.cleo/backups/`        (snapshot rotation overflow only)
 *   - `<projectRoot>/.cleo/backups/sqlite/` (per-DB rotation overflow)
 *   - `<projectRoot>/.cleo/backups/safety/` (T5158 pre-untrack siblings)
 *   - `<cleoHome>/`                          (global tier legacy DBs)
 *   - `<cleoHome>/nexus/`                    (nested-nexus legacy DBs)
 *
 * Each match is classified by `LegacyBackupOriginHint` and given a
 * retention recommendation (`keep` / `compress` / `delete`) based on the
 * 30-day soft + 90-day hard retention windows documented in ADR-013 §9.
 *
 * Two modes are exposed:
 *
 *   - {@link scanLegacyBackups}  — read-only walk; populates `entries`.
 *   - {@link pruneLegacyBackups} — same walk + actually deletes
 *     `delete`-recommended files (dry-run by default).
 *
 * Path resolution honours the project root + `@cleocode/paths`
 * `getCleoHome()`. Every disk op is wrapped in a defensive try/catch so
 * a single permission error never breaks the survey.
 *
 * @task T10309
 * @epic T10282
 * @saga T10281
 * @see ADR-013 §9 — Legacy backup retention policy
 */
import type { LegacyBackupEntry, LegacyBackupOriginHint, LegacyBackupRecommendation, LegacyBackupScanResult } from '@cleocode/contracts';
/**
 * Default soft retention window. Files younger than this are
 * unconditionally classified `keep` regardless of any other heuristic.
 */
export declare const DEFAULT_SOFT_RETENTION_DAYS = 30;
/**
 * Default hard retention window. Files older than this and outside the
 * quarantine tree are classified `delete`.
 */
export declare const DEFAULT_HARD_RETENTION_DAYS = 90;
/**
 * Configurable retention thresholds + override hook for clock-skew
 * deterministic tests.
 *
 * @task T10309
 */
export interface LegacyBackupScanOptions {
    /** Soft retention window in days (default {@link DEFAULT_SOFT_RETENTION_DAYS}). */
    softRetentionDays?: number;
    /** Hard retention window in days (default {@link DEFAULT_HARD_RETENTION_DAYS}). */
    hardRetentionDays?: number;
    /**
     * Wall-clock reference used by the walker for age computation. Test
     * fixtures pin this so the recommendation is independent of the
     * machine clock. Defaults to `Date.now()` at call time.
     */
    nowMs?: number;
}
/**
 * Prune-mode options. Always implies dry-run unless the caller passes
 * `dryRun: false`.
 *
 * @task T10309
 */
export interface LegacyBackupPruneOptions extends LegacyBackupScanOptions {
    /**
     * When `false`, the walker physically removes every artefact whose
     * recommendation is `delete`. DEFAULTS to `true` (dry-run) so a bare
     * `--prune` invocation can never destroy data.
     */
    dryRun?: boolean;
}
/**
 * Predicate: does this filename match one of the legacy backup
 * patterns the walker is responsible for?
 *
 * @param name - Plain filename (no directory).
 * @returns `true` when the file is a legacy backup candidate.
 */
export declare function isLegacyBackupFilename(name: string): boolean;
/**
 * Infer the origin hint for a legacy backup file from its absolute path
 * and basename.
 *
 * @param absolutePath - Absolute path to the candidate file.
 * @returns The most specific {@link LegacyBackupOriginHint} we can
 *   confidently assign without opening the file.
 */
export declare function classifyLegacyBackup(absolutePath: string): LegacyBackupOriginHint;
/**
 * Compute the retention recommendation for a legacy backup.
 *
 * Decision table:
 *
 * | Condition                            | Recommendation |
 * |--------------------------------------|----------------|
 * | `originHint === 'quarantine-*'`      | `keep`         |
 * | `ageDays <= softRetentionDays`       | `keep`         |
 * | `ageDays >= hardRetentionDays`       | `delete`       |
 * | `softRetentionDays < age < hard...`  | `compress`     |
 *
 * Quarantine and brain-malformed origins are ALWAYS kept — operators
 * may need them for forensic incident analysis.
 *
 * @param entry - Partial entry with `ageDays` and `originHint` already
 *   resolved.
 * @param softRetentionDays - Soft retention threshold.
 * @param hardRetentionDays - Hard retention threshold.
 * @returns Tuple of recommendation + human-readable reason.
 */
export declare function recommendForBackup(entry: Pick<LegacyBackupEntry, 'ageDays' | 'originHint'>, softRetentionDays: number, hardRetentionDays: number): {
    recommendation: LegacyBackupRecommendation;
    reason: string;
};
/**
 * Source paths the walker visits, in canonical order. Excludes the
 * worktree mirror under `<projectRoot>/.cleo/worktrees.json` (sentinel
 * file, not a directory) and the `.git/` tree.
 *
 * @param projectRoot - Absolute project root.
 * @param cleoHome    - Absolute CLEO home (`getCleoHome()`).
 * @returns Ordered array of directories to walk.
 */
export declare function legacyBackupSearchRoots(projectRoot: string, cleoHome: string): string[];
/**
 * Read-only legacy-backup walker.
 *
 * Enumerates every artefact under {@link legacyBackupSearchRoots} that
 * matches {@link isLegacyBackupFilename}, classifies each by origin,
 * and assigns a retention recommendation. The result is sorted by path
 * ascending and exposes the configured thresholds back to the caller.
 *
 * @param projectRoot - Absolute path to the project root.
 * @param options - Optional retention thresholds + clock override.
 * @returns A {@link LegacyBackupScanResult} with `prune: false` and
 *   empty `pruned`/`kept` arrays.
 *
 * @task T10309
 */
export declare function scanLegacyBackups(projectRoot: string, options?: LegacyBackupScanOptions): LegacyBackupScanResult;
/**
 * Prune-mode wrapper around {@link scanLegacyBackups}.
 *
 * Walks the same roots and, when `options.dryRun === false`, removes
 * every artefact whose `recommendation === 'delete'`. Quarantine
 * artefacts are NEVER touched — the `recommendForBackup` decision
 * table already filters them out.
 *
 * @param projectRoot - Absolute path to the project root.
 * @param options - Retention thresholds + dry-run toggle. `dryRun`
 *   defaults to `true` so the verb is safe under all calling
 *   conditions.
 * @returns A {@link LegacyBackupScanResult} with `prune: true` and
 *   `pruned`/`kept`/`errors` populated.
 *
 * @task T10309
 */
export declare function pruneLegacyBackups(projectRoot: string, options?: LegacyBackupPruneOptions): LegacyBackupScanResult;
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