import { existsSync } from 'node:fs';
import { join } from 'node:path';
import { itemsDir, type ItemType } from './data-path';
import { snapshotPlugins } from './plugins/mount';

/**
 * Where capabilities are read from — the owner's own store, plus every installed and enabled plugin's.
 *
 * ── Why plugins are read in place rather than copied in ──
 *
 * `capabilities/` is a git repository, and the point of it is that anybody can fork it: core's tasks and
 * skills, plus their own on top. That only holds if the directory contains exactly two things, what core
 * ships and what its owner wrote. Publishing a plugin's files into it broke that — a fork accumulated
 * files it did not author, with nothing on disk saying which, so committing them carried another plugin's
 * work and not committing them left `git status` permanently dirty.
 *
 * Copying was wrong a second way that has nothing to do with git. A copy goes STALE: `plugins:update` is
 * a `git pull` in the plugin's directory, and a capability copied out of it keeps describing the previous
 * version until something republishes. And a copy survives `plugins:disable`, so a disabled plugin's
 * skill stayed in the agent's index — the plugin off, the agent still told it was there.
 *
 * Reading in place fixes all of that by construction, and needs no namespace to do it. Scoping the paths
 * would have made provenance READABLE; separate directories make it STRUCTURAL, which is the stronger
 * property and the cheaper one.
 *
 * See `docs/plugin-capabilities.md`.
 *
 * ── Enabled, not merely installed ──
 *
 * A disabled plugin contributes nothing. That is the whole meaning of disable — routes down, sidecar
 * stopped — and a capability that outlived it was the one piece that did not comply.
 *
 * ── Cost ──
 *
 * This reads the database, so it is async, and it must not be called per turn. Its callers resolve it
 * once per session (`skillsBlock`, `affordanceBlock`) or per request on surfaces that are already doing
 * database work. A missing directory is skipped rather than erroring: most plugins ship no capabilities
 * at all, and that is the ordinary case rather than a fault.
 */
export type CapabilitySource = {
  dir: string;
  /** The plugin that ships it, or null for the owner's own store. */
  plugin: string | null;
};

export async function capabilitySources(type: ItemType | 'affordances' | 'notifications'): Promise<CapabilitySource[]> {
  const sources: CapabilitySource[] = [{ dir: itemsDir(type as ItemType), plugin: null }];

  let states: Awaited<ReturnType<typeof snapshotPlugins>>['states'] = [];
  try {
    ({ states } = await snapshotPlugins());
  } catch {
    // The owner's own capabilities still load. A database that cannot be read is a much louder problem
    // somewhere else, and losing the agent's whole skill index to it would only obscure that.
    return sources;
  }

  for (const state of states) {
    if (!state.install?.enabled) continue;
    const dir = join(state.plugin.dir, type);
    if (existsSync(dir)) sources.push({ dir, plugin: state.plugin.appName });
  }
  return sources;
}

/**
 * The same list for a caller that only needs the paths.
 *
 * Which is most of them: a skill or an affordance is read, compiled into a preamble and never written
 * to, so where it came from changes nothing. Tasks are the exception — one can be deleted, and deleting
 * a plugin's file out of the owner's screen is not a thing the owner asked for — so `task-files.ts`
 * takes the sources and keeps the provenance.
 */
export async function capabilityRoots(type: ItemType | 'affordances' | 'notifications'): Promise<string[]> {
  return (await capabilitySources(type)).map((s) => s.dir);
}

/**
 * Installed and enabled plugins, in the shape the notification catalogue wants.
 *
 * Notifications are the one capability whose namespace cannot be read off a path once the file stays in
 * the plugin's own directory — see `notifications/catalogue.ts` → `loadPluginEntries`. So the source list
 * carries the identity with it.
 */
export async function pluginCatalogueSources(): Promise<
  { appName: string; dir: string; manifest: { publisher: string } }[]
> {
  try {
    const { states } = await snapshotPlugins();
    return states
      .filter((s) => s.install?.enabled)
      .map((s) => ({
        appName: s.plugin.appName,
        dir: s.plugin.dir,
        manifest: { publisher: s.plugin.manifest.publisher },
      }));
  } catch {
    return [];
  }
}