/**
 * CoeditingRegistry — the INV-10 activation gate (spec §6.4). Holds the set of
 * documents the writer has explicitly entered into coediting; every surface
 * (SCM/QuickDiff, comments, preview annotations, edit commands, decorations)
 * checks membership before attaching. Persisted in workspaceState so a reload
 * restores the set (the durable sidecar carries the artifacts; this carries
 * only the mode).
 */
import * as vscode from "vscode";

const STATE_KEY = "cowriting.coeditingSet";

export class CoeditingRegistry implements vscode.Disposable {
  private readonly set: Set<string>;
  private readonly emitter = new vscode.EventEmitter<{ uri: string; coediting: boolean }>();
  readonly onDidChange = this.emitter.event;
  /** Set by the SCM surface (Task 3) so syncContext can expose the baseline mode. */
  baselineModeOf: ((uri: vscode.Uri) => "head" | "snapshot" | undefined) | undefined;

  constructor(private readonly state: vscode.Memento) {
    this.set = new Set(state.get<string[]>(STATE_KEY, []));
  }

  enter(uri: vscode.Uri): void {
    const key = uri.toString();
    if (this.set.has(key)) return;
    this.set.add(key);
    void this.state.update(STATE_KEY, [...this.set]);
    this.emitter.fire({ uri: key, coediting: true });
  }

  exit(uri: vscode.Uri): void {
    const key = uri.toString();
    if (!this.set.delete(key)) return;
    void this.state.update(STATE_KEY, [...this.set]);
    this.emitter.fire({ uri: key, coediting: false });
  }

  isCoediting(uri: vscode.Uri): boolean {
    return this.set.has(uri.toString());
  }

  list(): string[] {
    return [...this.set];
  }

  syncContext(editor: vscode.TextEditor | undefined): void {
    const coediting = !!editor && this.isCoediting(editor.document.uri);
    void vscode.commands.executeCommand("setContext", "cowriting.isCoediting", coediting);
    const mode = coediting && editor ? this.baselineModeOf?.(editor.document.uri) : undefined;
    void vscode.commands.executeCommand("setContext", "cowriting.baselineMode", mode ?? "");
  }

  dispose(): void {
    this.emitter.dispose();
  }
}