/**
 * Default aliases, alias/unalias builtins, and ~/.barerc loader.
 */
import { stripAliasQuotes } from './shell-syntax.js'
import { tokenize } from './shell-token.js'
import { expandWord } from './shell-expand.js'
import {
  applyBareOsThemeFromEnv,
  bareOsGetThemePreset
} from './bare-os-theme-presets.js'

/** Max alias indirections (prevents cycles). */
const MAX_ALIAS_DEPTH = 16

/**
 * Baseline aliases; `~/.barerc` and `unalias -a` merge/reset from this table.
 * @returns {Record<string, string>}
 */
export function defaultShellAliases() {
  return {
    nano: 'edit',
    top: 'baretop',
    btop: 'baretop',
    ll: 'ls -la',
    la: 'ls -A',
    l: 'ls',
    '..': 'cd ..',
    '...': 'cd ../..'
  }
}

/**
 * Expand first argv[0] through alias chain; append original argv.slice(1).
 * @param {string[]} argv
 * @param {Record<string, string> | null | undefined} aliases
 * @returns {string[]}
 */
export function expandArgvAliases(argv, aliases) {
  if (!argv.length) return argv
  const map = aliases && typeof aliases === 'object' ? aliases : {}
  const out = [...argv]
  let depth = 0
  while (depth < MAX_ALIAS_DEPTH) {
    const first = out[0]
    const repl = map[first]
    if (repl == null || repl === '') break
    const words = tokenize(repl)
      .filter((t) => t.type === 'word')
      .map((t) => t.value)
    if (!words.length) break
    out.splice(0, 1, ...words)
    depth++
  }
  if (depth >= MAX_ALIAS_DEPTH && map[out[0]]) {
    throw new Error('alias: expansion nested too deeply')
  }
  return out
}

/**
 * @param {Record<string, unknown>} ctx
 * @param {string} rest content after `alias ` (name=value...)
 */
export function applyAliasDefinition(ctx, rest) {
  const eq = rest.indexOf('=')
  if (eq <= 0) return false
  const aname = rest.slice(0, eq).trim()
  if (!aname) return false
  let val = rest.slice(eq + 1).trim()
  val = stripAliasQuotes(val)
  if (!ctx.shellAliases) ctx.shellAliases = {}
  ctx.shellAliases[aname] = val
  return true
}

/**
 * @param {Record<string, unknown>} ctx
 * @param {string[]} argv argv for unalias builtin (includes 'unalias')
 */
export function runUnaliasBuiltin(ctx, argv, logError) {
  if (!ctx.shellAliases) ctx.shellAliases = { ...defaultShellAliases() }
  const args = argv.slice(1)
  if (args.length === 0) {
    logError('unalias: missing name')
    return
  }
  if (args.includes('-a')) {
    ctx.shellAliases = { ...defaultShellAliases() }
    return
  }
  for (const name of args) {
    if (name === '-a') continue
    delete ctx.shellAliases[name]
  }
}

/**
 * Parse one line from ~/.barerc (without leading `unalias`).
 */
export function applyBarercUnalias(ctx, rest) {
  if (!ctx.shellAliases) ctx.shellAliases = { ...defaultShellAliases() }
  const parts = rest.split(/\s+/).filter(Boolean)
  if (parts.length === 1 && parts[0] === '-a') {
    ctx.shellAliases = { ...defaultShellAliases() }
    return
  }
  for (const name of parts) {
    if (name === '-a') ctx.shellAliases = { ...defaultShellAliases() }
    else delete ctx.shellAliases[name]
  }
}

/**
 * Comment-only template written on first login when `~/.barerc` is absent
 * (`loadBarerc(ctx, { createSkeletonIfMissing: true })`).
 */
export const BARERC_SKELETON = `# Bare OS — ~/.barerc (not full sh; only export, alias, unalias, theme, # comments).
#
# export MY_VAR=value
# theme default
# export BARE_OS_COLOR_DEPTH=truecolor
# export BARE_OS_DIRCOLORS=~/.dir_colors
# export BARE_OS_LS_COLORS_LOCKED=1
# alias gst='git status'
# unalias ll
`

/**
 * Load `~/.barerc`: only `export`, `alias`, `unalias`, `theme`, comments, blank lines.
 * Resets aliases to defaults first, then applies file.
 * @param {Record<string, unknown>} ctx
 * @param {{ createSkeletonIfMissing?: boolean }} [opts] If true and the file is missing, write {@link BARERC_SKELETON} (login / unlock only).
 */
export async function loadBarerc(ctx, opts = {}) {
  const { createSkeletonIfMissing = false } = opts
  const strict = globalThis.process?.env?.BARE_OS_STRICT_BARC === '1'
  ctx.shellAliases = { ...defaultShellAliases() }
  const vfs = ctx.vfs
  const env = vfs.env
  let buf = null
  try {
    buf = await vfs.readFile('~/.barerc')
  } catch {
    buf = null
  }

  let text = null
  if (!buf && createSkeletonIfMissing) {
    try {
      await vfs.writeFile('~/.barerc', ctx.b4a.from(BARERC_SKELETON))
      text = BARERC_SKELETON
    } catch (e) {
      ctx.console?.error?.(
        '[bare-os] could not create ~/.barerc: ' + ((e && e.message) || e)
      )
    }
  }

  if (!text) {
    if (!buf) {
      await applyBareOsThemeFromEnv(ctx)
      return
    }
    text = ctx.b4a.toString(buf)
  }
  for (const line of text.split(/\r?\n/)) {
    const t = line.trim()
    if (!t || t.startsWith('#')) continue
    if (t.startsWith('export ')) {
      const rest = t.slice(7).trim()
      const eq = rest.indexOf('=')
      if (eq > 0 && /^[A-Za-z_][A-Za-z0-9_]*$/.test(rest.slice(0, eq))) {
        env[rest.slice(0, eq)] = expandWord(rest.slice(eq + 1), env)
      } else if (strict) {
        ctx.console?.error?.('barerc: ignored: ' + t)
      }
      continue
    }
    if (t.startsWith('theme ') || t === 'theme') {
      const name = t === 'theme' ? '' : t.slice(6).trim()
      if (!name) {
        if (strict) ctx.console?.error?.('barerc: theme requires a name')
        continue
      }
      if (!/^[a-zA-Z0-9_.-]+$/.test(name)) {
        if (strict) ctx.console?.error?.('barerc: invalid theme name: ' + name)
        continue
      }
      const norm = name.toLowerCase().replace(/\s+/g, '_')
      if (!bareOsGetThemePreset(norm)) {
        ctx.console?.error?.('barerc: unknown theme: ' + name)
        continue
      }
      env.BARE_OS_THEME = norm
      continue
    }
    if (t.startsWith('alias ')) {
      const ok = applyAliasDefinition(ctx, t.slice(6).trim())
      if (!ok && strict) ctx.console?.error?.('barerc: ignored: ' + t)
      continue
    }
    if (t.startsWith('unalias ')) {
      applyBarercUnalias(ctx, t.slice(8).trim())
      continue
    }
    if (strict) ctx.console?.error?.('barerc: ignored: ' + t)
  }
  await applyBareOsThemeFromEnv(ctx)
}