export const COMPACTION_OVERRIDE_ENTRY = "vera.compaction.override";
export const COMPACTION_DETAILS_VERSION = 3;

/** Structural subset of Pi's model registry entries used by compaction. */
export interface CompactModel {
  provider: string;
  id: string;
  name?: string;
  api?: string;
  reasoning?: boolean;
  contextWindow?: number;
  maxTokens?: number;
  input?: string[];
  baseUrl?: string;
  cost?: {
    input?: number;
    output?: number;
    cacheRead?: number;
    cacheWrite?: number;
  };
  [key: string]: unknown;
}

export type SessionModelOverride =
  | { mode: "auto" }
  | { mode: "current" }
  | { mode: "model"; reference: string };

export interface CompactionConfig {
  enabled: boolean;
  modelSelection: {
    mode: "preferred" | "current";
    preferredModels: string[];
    allowCurrentSessionModel: boolean;
  };
  strategy: {
    usePiPreparationFirst: boolean;
    recoverFromBranchEntriesWhenEmpty: boolean;
    groupByTurns: boolean;
    groupToolCycles: boolean;
    keptBudgetChars: number;
    dropRawThinking: boolean;
    toolResults: {
      mode: "compress";
      headLines: number;
      tailLines: number;
      maxChars: number;
    };
    oversizedMessages: {
      mode: "compress";
      headChars: number;
      tailChars: number;
      maxChars: number;
    };
    historySnip: {
      enabled: boolean;
      targetChars: number;
      keepHeadUnits: number;
      keepTailUnits: number;
      minOmittedUnits: number;
      maxPreviewChars: number;
    };
    microcompact: {
      enabled: boolean;
      targetChars: number;
      keepRecentToolResults: number;
      maxPlaceholderChars: number;
    };
    contextCollapse: {
      enabled: boolean;
      targetChars: number;
      keepFirstUnits: number;
      keepRecentUnits: number;
      maxSummaryChars: number;
      maxListItems: number;
    };
    chunking: {
      enabled: boolean;
      targetChars: number;
      maxChunks: number;
      minMessagesPerChunk: number;
    };
  };
  fallback: {
    onFailure: "next-model" | "cancel";
    maxAttempts: number;
  };
  notifications: {
    showModelUsed: boolean;
    showCompressionStats: boolean;
  };
}

export interface CompressionStats {
  inputMessages: number;
  outputMessages: number;
  recoveredFromBranchEntries: boolean;
  groupedTurns: number;
  semanticUnits: number;
  chunkCount: number;
  droppedThinkingBlocks: number;
  compressedToolResults: number;
  truncatedMessages: number;
  truncatedTextBlocks: number;
  snippedMessages: number;
  snippedSemanticUnits: number;
  microcompactedToolResults: number;
  collapsedMessages: number;
  collapsedSemanticUnits: number;
}

export interface CompactionModelSelection {
  selected: CompactModel | null;
  models: CompactModel[];
  availableRefs: string[];
  source: "session-override" | "config-preferred" | "current-model" | "available-fallback" | "none";
  override: SessionModelOverride | null;
  warnings: string[];
}

export interface CompactionRunInfo {
  modelReference: string;
  source: string;
  attempt: number;
  attempts: number;
  usedFallback: boolean;
  compression: CompressionStats;
  lastError?: string;
}

export interface CompactionState {
  config: CompactionConfig;
  configSource: string;
  sessionOverride: SessionModelOverride | null;
  lastRun: CompactionRunInfo | null;
}