export interface CacheUsageTotals {
  input: number;
  output: number;
  cacheRead: number;
  cacheWrite: number;
  totalTokens: number;
  assistantMessages: number;
}

export interface AssistantUsageMetric {
  sequence: number;
  activeBranchSequence?: number;
  entryId: string;
  timestamp: string;
  provider: string;
  model: string;
  input: number;
  output: number;
  cacheRead: number;
  cacheWrite: number;
  totalTokens: number;
  cacheHitPercent: number;
  isOnActiveBranch: boolean;
  /** True when provider/model differs from the previous assistant message. */
  modelChanged?: boolean;
  /** Gap in ms to the previous assistant message. */
  idleMs?: number;
  /** True when the idle gap exceeds the TTL applicable to this model's API protocol. */
  idleExpired?: boolean;
  /** True when a compaction/branch summary sits between this turn and the previous one. */
  afterCompact?: boolean;
  /** True when a thinking-level change entry sits between this turn and the previous one. */
  thinkingChanged?: boolean;
  /**
   * True when the prompt shrank substantially versus the previous assistant
   * message. Appending never shrinks a prompt and idle expiry never changes
   * it, so a large shrink is decisive evidence that the context was rebuilt
   * differently (restart replay, restored session, replay/tool-set change).
   */
  promptShrunk?: boolean;
  /**
   * True when a large share of the cached prefix was re-billed with no
   * recorded cause — the catch-all signal for prefix rewrites pi does not
   * persist (tool set, context files, extension injection). Co-occurs with
   * idleExpired: a restart, for example, creates both a long gap and a
   * rebuilt prefix, and the rebuilt tag must not be suppressed by the gap.
   */
  contextInvalidated?: boolean;
  /** Prefix tokens re-billed as fresh (pi's cache-miss math), when significant. */
  missedTokens?: number;
  /** Estimated extra cost of the miss in USD, when significant. */
  missedCost?: number;
  /** Missed tokens as a ratio of the previous prompt (cached prefix). */
  missRatio?: number;
  /**
   * Listed in the miss analysis: the miss ratio exceeded the cached-length-
   * scaled threshold, i.e. the cacheable prefix was broken.
   */
  missFlagged?: boolean;
}

export interface CacheSessionMetrics {
  allMessages: AssistantUsageMetric[];
  treeTotals: CacheUsageTotals;
  activeBranchTotals: CacheUsageTotals;
}