// 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");

  }

}