/**
 * Where this plugin keeps things on disk.
 *
 * Everything lives under `$DSH_HOME`, never inside the workspace. That is the
 * whole point of the plugin's economics: the index holds a vector per code
 * chunk, which for a 300k-line repository is tens of megabytes — several times
 * the size of the source it describes. A multi-megabyte binary file appearing
 * in a repository the user might commit, or that a `git status` might surface
 * mid-task, is a worse outcome than the tokens it saves.
 *
 * The index is also disposable by construction. It is keyed by content hash, so
 * deleting it costs one re-embed and nothing else — which is what makes it safe
 * to treat as a cache rather than a document.
 */

import { createHash } from 'node:crypto'
import { homedir } from 'node:os'
import { basename, join, resolve } from 'node:path'

/** Plugin name. Also the `$DSH_HOME/<name>` directory. */
export const PLUGIN_NAME = 'dsh-recall'

/** The dsh home directory: `$DSH_HOME`, else `~/.dsh`. */
export function resolveDshHome(env = process.env) {
  const configured = typeof env.DSH_HOME === 'string' ? env.DSH_HOME.trim() : ''
  return configured === '' ? join(homedir(), '.dsh') : resolve(configured)
}

/**
 * A stable, filesystem-safe key for one workspace.
 *
 * The basename is for a human reading the directory listing; the hash is what
 * actually identifies it, so two checkouts both named `app` cannot collide and
 * one checkout moved between parents does not silently inherit the other's
 * index.
 */
export function workspaceKey(cwd) {
  const absolute = resolve(cwd)
  const name =
    basename(absolute)
      .replace(/[^A-Za-z0-9._-]+/g, '-')
      .replace(/^[-.]+|-+$/g, '') || 'workspace'
  const hash = createHash('sha256').update(absolute).digest('hex').slice(0, 8)
  return `${name}-${hash}`
}

/** Root of this plugin's own data, independent of any workspace. */
export function pluginDataDir(dshHome) {
  return join(dshHome, PLUGIN_NAME)
}

/** Per-workspace state directory. */
export function workspaceStateDir(dshHome, cwd) {
  return join(pluginDataDir(dshHome), 'workspaces', workspaceKey(cwd))
}

/** The SQLite index for one workspace. */
/**
 * The SQLite index for one workspace, optionally narrowed to one focus.
 *
 * The workspace-wide index deliberately keeps its original path. Focus is
 * additive: a deployment that never sets one must find the index it already
 * built, not silently re-embed the repository into a new file.
 *
 * @param {string} dshHome harness home
 * @param {string} cwd workspace root
 * @param {string} [focus] focus key, `.` for the workspace itself
 */
export function indexFile(dshHome, cwd, focus = '.') {
  const base = workspaceStateDir(dshHome, cwd)
  return focus === '.' ? join(base, 'index.sqlite') : join(base, 'focus', focus, 'index.sqlite')
}