/**
 * Shared identifiers for pi-context-epochs session entries and markers.
 *
 * All package-owned session artifacts are namespaced under
 * "pi-context-epochs/" so they can be recognized on reload, resume,
 * branch navigation, and by diagnostics tooling.
 */

/** details.kind marker persisted on package-owned epoch-boundary compaction entries. */
export const EPOCH_KIND = "pi-context-epochs/epoch";

/** EPOCH_DETAILS_VERSION of the epoch boundary payload format. */
export const EPOCH_DETAILS_VERSION = 1;

/** custom entry type used to persist note write/delete events. */
export const NOTE_ENTRY_TYPE = "pi-context-epochs/note";

/** custom message type used for the continuation nudge after a model/manual rollover. */
export const CONTINUATION_MESSAGE_TYPE = "pi-context-epochs/continuation";

/** custom message type used for one-shot context-pressure reminders. */
export const REMINDER_MESSAGE_TYPE = "pi-context-epochs/reminder";

/**
 * customInstructions prefix that routes a manual compaction through the
 * package-owned epoch boundary instead of the native summarizer.
 * Only ever produced by this package (new_context tool, /epoch new).
 */
export const ROLLOVER_INSTRUCTIONS_PREFIX = "pi-context-epochs/rollover:";

/**
 * firstKeptEntryId used on epoch-boundary compactions.
 *
 * Pi entry ids are 8 hex characters, so this value can never match a real
 * entry. buildContextEntries() then keeps ONLY the compaction entry itself
 * plus entries appended after it - which is exactly "prior history fully
 * exits the active model context while the raw transcript stays intact".
 */
export const IMPOSSIBLE_FIRST_KEPT_ENTRY_ID = "ctx-epochs:none";

/** Default settings used when no config file exists or values are invalid. */
export interface EpochConfig {
  enabled: boolean;
  softRemainingRatio: number;
  criticalRemainingRatio: number;
  autoRollover: boolean;
  historySearchLimit: number;
  historyReadAround: number;
  historyMaxChars: number;
  noteMaxChars: number;
  continuationAnchorMaxChars: number;
}

export const DEFAULT_CONFIG: EpochConfig = {
  enabled: true,
  softRemainingRatio: 0.25,
  criticalRemainingRatio: 0.1,
  autoRollover: true,
  historySearchLimit: 8,
  historyReadAround: 2,
  historyMaxChars: 16_000,
  noteMaxChars: 8_000,
  continuationAnchorMaxChars: 2_000,
};

export type EpochTrigger = "model" | "threshold" | "manual" | "overflow";