import { ITokenizer } from './tokenizers/i-tokenizer.js';
import { ISummarizer } from './summarization.js';
/**
 * Session state — addresses issues #121 and #122.
 *
 * A Session holds a single user's conversation history plus a per-file
 * content snapshot. The history is token-budgeted (see #121) and the file
 * snapshots feed context-delta tracking (#122).
 */
export type MessageRole = 'system' | 'user' | 'assistant' | 'tool';
export interface Message {
    role: MessageRole;
    content: string;
    timestamp: number;
}
export interface SessionFileState {
    [filePath: string]: string;
}
export interface SessionSnapshot {
    id: string;
    history: Message[];
    fileState: SessionFileState;
    maxTokens: number;
    createdAt: number;
    updatedAt: number;
}
export interface SessionOptions {
    id?: string;
    maxTokens?: number;
    preserveTailRatio?: number;
    tokenizer?: ITokenizer;
    summarizer?: ISummarizer;
    /**
     * When true, getHistoryTokenCount may fall back to a character/4
     * heuristic if no tokenizer is supplied. Production code should
     * always pass a real tokenizer and leave this false (the default).
     */
    allowCharHeuristic?: boolean;
    /** Override for createdAt — used by fromSnapshot. */
    createdAt?: number;
    /** Override for updatedAt — used by fromSnapshot. */
    updatedAt?: number;
}
export declare class Session {
    readonly id: string;
    maxTokens: number;
    readonly createdAt: number;
    updatedAt: number;
    private history;
    private fileState;
    private readonly preserveTailRatio;
    private readonly tokenizer;
    private readonly summarizer;
    private readonly allowCharHeuristic;
    constructor(options?: SessionOptions);
    addMessage(role: MessageRole, content: string): Message;
    getHistory(): readonly Message[];
    getFileState(): Readonly<SessionFileState>;
    getFileContent(filePath: string): string | undefined;
    setFileContent(filePath: string, content: string): void;
    clearFileContent(filePath: string): void;
    /**
     * Total token count of the current history.
     *
     * Requires a tokenizer unless the caller opted into the character/4
     * heuristic via `allowCharHeuristic: true`. We default to requiring a
     * tokenizer because #124's whole point is eliminating char/4.
     */
    getHistoryTokenCount(): Promise<number>;
    /**
     * Compress the history by summarizing everything except the
     * preserve-tail fraction. Does nothing if history fits under maxTokens.
     *
     * Returns the new token count after compression.
     */
    compressHistory(): Promise<number>;
    toSnapshot(): SessionSnapshot;
    static fromSnapshot(snapshot: SessionSnapshot, options?: Omit<SessionOptions, 'id' | 'maxTokens' | 'createdAt' | 'updatedAt'>): Session;
}
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