interface AssistantTurn {
    cache_read: number;
    cache_creation: number;
    input_tokens: number;
}
export interface CacheHealthSummary {
    turns: number;
    totalCacheRead: number;
    totalCacheCreation: number;
    totalInput: number;
    /** Fraction of total tokens that were cache hits. Bounded [0, 1]. */
    hitRatio: number;
    /** Number of turns detected as cache flushes (turn_index > 0, cache_creation > 5000, cache_read < 1000). */
    flushCount: number;
    /**
     * Effective cost in "input token equivalent" units:
     *   cache_read × 0.1 + cache_creation × 1.25 + input × 1.0
     */
    effectiveInputTokens: number;
    /** Turn index (0-based) of the last detected flush, or null if none. */
    lastFlushAt: number | null;
}
/** Shape returned after extracting the assistant entry — always has usage. */
interface AssistantEntryNormalised {
    usage: Record<string, unknown>;
}
/**
 * Type guard / extractor for assistant JSONL entries (DoD #3: `isAssistantEntry` equivalent).
 *
 * Returns a normalised `{ usage }` object when the entry is a valid assistant
 * turn, or null otherwise. A classic `v is X` predicate could not be used here
 * because the union type produced by the nested-vs-flat duality prevents TS from
 * narrowing `usage` after the guard (TS7053 — hence this extract-and-return pattern).
 *
 * Accepts both forms observed in production:
 *   (a) Nested: { type:"assistant", message:{ role:"assistant", usage:{...} } }
 *   (b) Flat (defensive fallback): { role:"assistant", usage:{...} }
 *
 * Returns null when:
 * - the entry is not an object
 * - `role` is not "assistant"
 * - `usage` is absent or not an object (DoD: missing usage → skip)
 */
export declare function extractAssistantEntry(v: unknown): AssistantEntryNormalised | null;
/** Extract a non-negative integer from an unknown value, defaulting to 0. */
export declare function extractTokenCount(v: unknown): number;
/**
 * Read a Claude Code session JSONL file and return one `AssistantTurn` per
 * assistant message that has a valid `usage` object.
 *
 * Parsing rules:
 * - Lines are read via `fs.readFileSync` + split on `\n`, empty lines filtered.
 * - Malformed JSON lines are skipped silently (no throw).
 * - Only entries with `role === 'assistant'` and a present usage object are included.
 * - Missing token count fields fall back to 0.
 */
export declare function readSessionJsonl(filePath: string): AssistantTurn[];
/** Minimum cache_creation value (exclusive) to consider a turn a cache flush. */
export declare const FLUSH_CREATION_THRESHOLD = 5000;
/** Maximum cache_read value (exclusive) that can coexist with a flush. */
export declare const FLUSH_READ_THRESHOLD = 1000;
/**
 * Compute cache health metrics from a list of `AssistantTurn` entries.
 *
 * Flush detection heuristic (turn_index > 0 required — initial creation is expected):
 *   `cache_creation > FLUSH_CREATION_THRESHOLD && cache_read < FLUSH_READ_THRESHOLD`
 *
 * Pricing constants for `effectiveInputTokens`:
 *   `cache_read × 0.1 + cache_creation × 1.25 + input × 1.0`
 */
export declare function summariseCacheHealth(entries: AssistantTurn[], _opts?: Record<string, never>): CacheHealthSummary;
export {};