/**
 * @license
 * Copyright 2025 Vybestack LLC
 * SPDX-License-Identifier: Apache-2.0
 */
/**
 * @plan PLAN-20260211-COMPRESSION.P04
 * @requirement REQ-CS-004.1, REQ-CS-004.2, REQ-CS-004.3, REQ-CS-004.4
 *
 * Shared utility functions for adjusting compression/truncation boundaries
 * to avoid splitting tool call/response pairs in conversation history.
 *
 * Extracted from GeminiChat as pure standalone functions with no class or
 * logging dependencies.
 */
import type { ContentBlock, IContent } from '../../services/history/IContent.js';
/**
 * Aggregate text from content blocks, handling spacing between text and
 * non-text blocks. Used by LLM-based compression strategies to collect
 * streamed response text.
 */
export declare function aggregateTextFromBlocks(blocks: ContentBlock[], currentText: string, lastBlockWasNonText: boolean): {
    text: string;
    lastBlockWasNonText: boolean;
};
/**
 * Adjust compression boundary to not split tool call/response pairs.
 * Searches for a valid split point that doesn't break tool call/response
 * pairs. If the initial index lands inside a tool response sequence, it
 * first tries moving forward, then searches backward for a valid boundary.
 */
export declare function adjustForToolCallBoundary(history: IContent[], index: number): number;
/**
 * Search forward from the given index to find a valid split point that
 * doesn't land in the middle of a tool response sequence. If, after
 * skipping tool responses, the preceding AI message has tool calls
 * whose responses are not in the kept portion, backs up by one to
 * include the AI message in the removed portion.
 */
export declare function findForwardValidSplitPoint(history: IContent[], index: number): number;
/**
 * Search backward from the given start index to find a valid split point.
 * Skips tool response messages and AI messages whose tool calls don't
 * have matching responses in the remaining history. Returns the first
 * valid boundary found, or startIndex if none is found.
 */
export declare function findBackwardValidSplitPoint(history: IContent[], startIndex: number): number;
/**
 * Build a context-aware continuation directive to replace the static
 * compression acknowledgment. When active todos exist the directive
 * references the first task and points the model at todo_read for
 * full recovery; otherwise it emits a simple "continue" statement.
 */
export declare function buildContinuationDirective(activeTodos?: string): string;
/**
 * Convert tool_call and tool_response blocks to plain text representations
 * so the compression request doesn't trip Anthropic's strict tool_use /
 * tool_result pairing validation.  Orphaned tool blocks (from interrupted
 * loops or the loop-detector halting mid-tool-call) would otherwise cause
 * 400 errors when sent to the LLM for summarisation.
 *
 * Messages whose speaker is 'tool' are re-tagged as 'human' since they
 * no longer carry structural tool_result blocks.  All other block types
 * (text, thinking, code, media) pass through unchanged.
 */
export declare function sanitizeHistoryForCompression(messages: readonly IContent[]): IContent[];