// Briefs as documents (spec §5.2): `spectra-brief:/overall.md` and
// `spectra-brief:/project/NAME.md`. Opening one reads it from Spectra;
// saving it records a signed brief.set, so agents are told.
import * as vscode from "vscode";
import type { Briefs } from "./spectra-api";
import { Bridge } from "./bridge";

export const SCHEME = "spectra-brief";

export function uriFor(project?: string): vscode.Uri {
  return vscode.Uri.from({ scheme: SCHEME, path: project ? `/project/${project}.md` : "/overall.md" });
}

function projectOf(uri: vscode.Uri): string | undefined {
  const m = /^\/project\/([a-z0-9][a-z0-9-]*)\.md$/.exec(uri.path);
  if (m) return m[1];
  if (uri.path === "/overall.md") return undefined;
  throw vscode.FileSystemError.FileNotFound(uri);
}

export class BriefFs implements vscode.FileSystemProvider {
  private readonly emitter = new vscode.EventEmitter<vscode.FileChangeEvent[]>();
  readonly onDidChangeFile = this.emitter.event;
  private readonly times = new Map<string, number>();

  constructor(private readonly bridge: Bridge) {}

  watch(): vscode.Disposable {
    return new vscode.Disposable(() => undefined);
  }

  /** Tell open editors that briefs changed in Spectra. */
  changed(): void {
    const now = Date.now();
    const events: vscode.FileChangeEvent[] = [];
    for (const k of this.times.keys()) {
      this.times.set(k, now);
      events.push({ type: vscode.FileChangeType.Changed, uri: vscode.Uri.parse(k) });
    }
    if (events.length) this.emitter.fire(events);
  }

  private async text(uri: vscode.Uri): Promise<string> {
    const project = projectOf(uri);
    const b = await this.bridge.request<Briefs>("GET", "/api/v1/briefs");
    return (project ? b.projects.find((p) => p.project === project)?.text : b.overall) ?? "";
  }

  async stat(uri: vscode.Uri): Promise<vscode.FileStat> {
    projectOf(uri);
    const key = uri.toString();
    if (!this.times.has(key)) this.times.set(key, Date.now());
    const size = Buffer.byteLength(await this.text(uri).catch(() => ""));
    return { type: vscode.FileType.File, ctime: 0, mtime: this.times.get(key)!, size };
  }

  async readFile(uri: vscode.Uri): Promise<Uint8Array> {
    return Buffer.from(await this.text(uri));
  }

  async writeFile(uri: vscode.Uri, content: Uint8Array): Promise<void> {
    const project = projectOf(uri);
    try {
      await this.bridge.request("PUT", "/api/v1/briefs", { project: project ?? null, text: Buffer.from(content).toString("utf8") });
    } catch (e) {
      throw vscode.FileSystemError.NoPermissions(`Spectra did not take the brief: ${(e as Error).message}`);
    }
    this.times.set(uri.toString(), Date.now());
    void vscode.window.setStatusBarMessage(`$(check) ${project ? `${project}'s brief` : "Overall brief"} signed into Spectra; agents are told on their next call`, 5000);
  }

  readDirectory(): [string, vscode.FileType][] {
    return [];
  }
  createDirectory(): void {
    throw vscode.FileSystemError.NoPermissions("briefs are not folders");
  }
  delete(): void {
    throw vscode.FileSystemError.NoPermissions("clear a brief by saving it empty");
  }
  rename(): void {
    throw vscode.FileSystemError.NoPermissions("briefs cannot be renamed");
  }
}