import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-agent";
import type { PruneFrontier } from "./types.js";
import { CUSTOM_TYPE_FRONTIER } from "./types.js";

/**
 * Tracks the most recent completed prune-attempt boundary.
 *
 * The frontier advances when a prune attempt finishes, regardless of whether it
 * produced a persisted summary or was skipped because the summary was larger
 * than the raw tool outputs. It does not advance on operational failures.
 */
export class PruneFrontierTracker {
  private frontier: PruneFrontier | null = null;

  reset(): void {
    this.frontier = null;
  }

  get(): PruneFrontier | null {
    return this.frontier ? { ...this.frontier } : null;
  }

  fromJSON(data: PruneFrontier): void {
    if (!data?.lastAttemptedToolCallId) return;
    this.frontier = {
      lastAttemptedToolCallId: data.lastAttemptedToolCallId,
      lastAttemptedToolName: data.lastAttemptedToolName ?? "unknown",
      lastAttemptedTurnIndex: data.lastAttemptedTurnIndex ?? 0,
      lastAttemptedTimestamp: data.lastAttemptedTimestamp ?? 0,
      attemptedBatchCount: data.attemptedBatchCount ?? 0,
      attemptedToolCallCount: data.attemptedToolCallCount ?? 0,
      rawCharCount: data.rawCharCount ?? 0,
      summaryCharCount: data.summaryCharCount ?? 0,
      outcome: data.outcome ?? "summarized",
    };
  }

  reconstructFromSession(ctx: ExtensionContext): void {
    this.reset();
    const branch = ctx.sessionManager.getBranch();
    for (const entry of branch) {
      if (
        entry.type === "custom" &&
        (entry as any).customType === CUSTOM_TYPE_FRONTIER
      ) {
        const data = (entry as any).data as PruneFrontier;
        if (data) {
          this.fromJSON(data);
        }
      }
    }
  }

  advance(frontier: PruneFrontier): void {
    this.frontier = { ...frontier };
  }

  persist(pi: ExtensionAPI): void {
    if (!this.frontier) return;
    pi.appendEntry(CUSTOM_TYPE_FRONTIER, this.frontier);
  }
}