/**
 * PendingEditRegistry — the seam's bookkeeping (spec §6.2, INV-9). Before
 * applyAgentEdit applies a WorkspaceEdit, it registers the exact expected
 * change; the controller's change handler consumes a matching registration to
 * attribute that change to the agent. Anything unmatched is human typing.
 * vscode-free and unit-testable.
 */
import type { Provenance } from "./model";

export interface PendingEdit {
  docPath: string;
  /** half-open [start, end) offsets of the replaced range. */
  start: number;
  end: number;
  newText: string;
  provenance: Provenance;
  turnId?: string;
}

export class PendingEditRegistry {
  private pending: PendingEdit[] = [];

  register(edit: PendingEdit): void {
    this.pending.push(edit);
  }

  /**
   * Remove a registration that failed to apply. Identity-based (`===`), so
   * callers must keep the exact registered object; it is a no-op when `match`
   * already consumed the registration.
   */
  unregister(edit: PendingEdit): void {
    this.pending = this.pending.filter((p) => p !== edit);
  }

  /**
   * Find-and-consume the registration exactly matching a change event
   * (same doc, same replaced range, same inserted text). Null → human edit.
   */
  match(docPath: string, change: { start: number; end: number; text: string }): PendingEdit | null {
    const i = this.pending.findIndex(
      (p) =>
        p.docPath === docPath &&
        p.start === change.start &&
        p.end === change.end &&
        p.newText === change.text,
    );
    if (i === -1) return null;
    const [hit] = this.pending.splice(i, 1);
    return hit;
  }
}