/**
 * Where this plugin keeps things on disk.
 *
 * Every path here is deliberately under `$DSH_HOME`, because `$DSH_HOME` is the
 * one directory that survives the container this harness usually runs in. The
 * uv-managed slopo install and the CPython it needs would otherwise live in
 * `~/.local`, which is on the container's writable layer and is lost whenever
 * the container is recreated rather than merely restarted.
 *
 * Relative paths are never used: slopo resolves every relative path against the
 * *process working directory*, not against the config file that named it, so a
 * relative path in a config invoked as `--config /elsewhere/x.yaml` still lands
 * in whatever directory the caller happened to be in.
 */

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

/** Plugin name, used for the `$DSH_HOME/plugin-data/<name>` directory. */
export const PLUGIN_NAME = 'dsh-slopo'

/** 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.
 */
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}`
}

/** Per-workspace state: the slopo config, index database, ignore file and log. */
export function workspaceStateDir(dshHome, cwd) {
  return join(dshHome, 'plugin-data', PLUGIN_NAME, 'workspaces', workspaceKey(cwd))
}

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

/**
 * The directory `uv tool install` writes the slopo venv and shim into.
 *
 * Redirected here from its `~/.local/share/uv/tools` default for the durability
 * reason in the file header.
 */
export function managedToolDir(dshHome) {
  return join(pluginDataDir(dshHome), 'uv-tools')
}

/** The directory uv keeps its downloaded CPython builds in. */
export function managedPythonDir(dshHome) {
  return join(pluginDataDir(dshHome), 'uv-python')
}

/** The slopo executable inside {@link managedToolDir}. */
export function managedSlopoPath(dshHome) {
  return join(managedToolDir(dshHome), 'bin', process.platform === 'win32' ? 'slopo.exe' : 'slopo')
}

/** Slopo's own default install location, for machines that already have one. */
export function userLocalSlopoPath(env = process.env) {
  const home = typeof env.HOME === 'string' && env.HOME !== '' ? env.HOME : homedir()
  return join(home, '.local', 'bin', process.platform === 'win32' ? 'slopo.exe' : 'slopo')
}