// ── The logic half of configuration-from-the-site ─────────────────────────
//
// Everything here is about the difference between what a game host reports and
// what an admin should be shown. Three jobs:
//
//  1. **Group a flat file list by plugin**, because one plugin can own several
//     files and a form that lists 40 paths is not a settings screen.
//  2. **Say which file is ours, and which keys inside it are locked** (D38). The
//     plugin names itself in the catalogue rather than us matching a filename,
//     so renaming the file cannot quietly unlock the three keys that would cut
//     the link or split a server's history.
//  3. **Decide nothing about paths.** The only process that can say whether a
//     path resolves inside a configuration directory is the one holding the
//     directory. This file checks SHAPE, so an obviously malformed request is
//     refused before it costs a round trip — never as a substitute for the real
//     check on the host.

const configEdit = require('../../configEdit')

/**
 * Keys in the bridge plugin's own config that the website may not change (D38).
 *
 * `Host` and `Port` are the link this edit is travelling over, and `ServerId` is
 * how every row this module has ever stored is keyed — changing it does not
 * rename a server, it strands its history and starts a new one under a name
 * nobody chose deliberately. All three are editable on the host, by a person
 * who is standing on it.
 */
const LOCKED_KEYS = ['Host', 'Port', 'ServerId']

/** What a locked field says for itself, on the screen and in a refusal. */
const LOCKED_REASON = {
  host: 'the website reaches this server through this address',
  port: 'the website reaches this server through this port',
  serverid: 'every row this site holds for this server is keyed to this id',
}

/**
 * A path shaped like something the host could plausibly have listed.
 *
 * Deliberately narrow and deliberately **not** the security boundary: no `..`,
 * nothing absolute, no drive letter, forward slashes, and it ends in `.json`.
 */
const PATH_SHAPE = /^(?!.*\.\.)(?!\/)[A-Za-z0-9 _.\-()[\]]+(?:\/[A-Za-z0-9 _.\-()[\]]+)*\.json$/

function isPlausiblePath(path) {
  return typeof path === 'string' && path.length > 0 && path.length <= 255 && PATH_SHAPE.test(path)
}

/**
 * Shapes the plugin's catalogue into the screen's shape: plugins, each with its
 * files, each file saying whether it can be edited and why not.
 *
 * A file whose guessed plugin is not loaded is kept and **marked**, not dropped.
 * An operator whose config for an unloaded plugin vanished from the page would
 * conclude the bridge cannot see it, which is a different and much more alarming
 * problem than the true one.
 */
function shapeCatalogue(catalogue) {
  if (!catalogue || typeof catalogue !== 'object') return null

  const loaded = Array.isArray(catalogue.plugins) ? catalogue.plugins : []
  const byName = new Map(loaded.map((p) => [String(p.name).toLowerCase(), p]))
  const self = catalogue.self ? String(catalogue.self) : null

  const groups = new Map()

  for (const file of Array.isArray(catalogue.files) ? catalogue.files : []) {
    const plugin = String(file.plugin || 'unknown')
    const key = plugin.toLowerCase()

    if (!groups.has(key)) {
      const match = byName.get(key)
      groups.set(key, {
        plugin,
        loaded: Boolean(match),
        title: match ? match.title : null,
        version: match ? match.version : null,
        // The bridge plugin cannot reload itself — the reload would close the
        // link carrying the answer — so the screen says so up front rather than
        // offering a button that always refuses.
        isBridge: self != null && plugin.toLowerCase() === self.toLowerCase(),
        files: [],
      })
    }

    groups.get(key).files.push({
      path: String(file.path),
      bytes: Number(file.bytes) || 0,
      modified: file.modified ? Number(file.modified) : null,
      editable: file.editable !== false,
      ...(file.reason ? { reason: String(file.reason) } : {}),
    })
  }

  return {
    root: catalogue.root ? String(catalogue.root) : null,
    self,
    truncated: Boolean(catalogue.truncated),
    limits: catalogue.limits || null,
    plugins: [...groups.values()].sort((a, b) => a.plugin.localeCompare(b.plugin)),
    loaded: loaded
      .map((p) => ({ name: String(p.name), title: p.title || null, version: p.version || null }))
      .sort((a, b) => a.name.localeCompare(b.name)),
  }
}

/** Whether this file is the bridge's own config, by the name the plugin gave. */
function isBridgeConfig(path, self) {
  if (!self) return false
  const plugin = String(path).includes('/') ? String(path).split('/')[0] : String(path).replace(/\.json$/i, '')
  return plugin.toLowerCase() === String(self).toLowerCase()
}

/** The locked keys for a file: three of them in our own config, none anywhere else. */
function lockedKeysFor(path, self) {
  return isBridgeConfig(path, self) ? LOCKED_KEYS : []
}

/**
 * Turns one file the host sent into what the form renders.
 *
 * The text is passed through untouched. What is added is the READING of it: the
 * field list, which fields are locked, and which hold something a browser should
 * mask by default.
 */
function shapeFile(file, { self = null, maxDepth = 6 } = {}) {
  if (!file || typeof file.text !== 'string') return null

  const locked = lockedKeysFor(file.path, self)
  let fields = null
  let parseError = null

  try {
    fields = configEdit.describe(configEdit.scan(file.text), { maxDepth, locked })
  } catch (err) {
    // A config already broken on disk still opens — in the raw tier, which is
    // the only thing that can fix it. A page that refused to show a broken file
    // would send somebody to SSH for the one job this feature exists to do.
    parseError = err.message
  }

  return {
    path: String(file.path),
    plugin: file.plugin ? String(file.plugin) : null,
    version: String(file.version),
    bytes: Number(file.bytes) || 0,
    modified: file.modified ? Number(file.modified) : null,
    text: file.text,
    fields,
    parseError,
    locked: locked.map((key) => ({ key, reason: LOCKED_REASON[key.toLowerCase()] || null })),
    isBridge: isBridgeConfig(file.path, self),
  }
}

/**
 * Which locked keys differ between two versions of a document.
 *
 * The form refuses a locked field by pointer, but the **raw tier submits a whole
 * document**, and a document can change `Port` without anything resembling an
 * edit to a field. So the raw tier is checked the only way it can be: by
 * comparing the literals before and after.
 *
 * A file that will not parse is not a way around this — an unparseable document
 * is refused before it gets here.
 */
function lockedChanges(before, after, locked) {
  if (!locked || locked.length === 0) return []

  let a
  let b

  try {
    a = configEdit.scan(before)
    b = configEdit.scan(after)
  } catch {
    // Nothing can be compared, so nothing is cleared. The caller refuses.
    return locked.slice()
  }

  const literal = (root, key) => {
    if (root.type !== 'object') return null
    const node = root.children.find((c) => String(c.key).toLowerCase() === key.toLowerCase())
    return node ? JSON.stringify(node.value) + ':' + (node.raw || '') : null
  }

  return locked.filter((key) => literal(a, key) !== literal(b, key))
}

/** Every change a report says landed, as one line per file. */
function summariseReport(report) {
  if (!report || typeof report !== 'object') return null

  const files = Array.isArray(report.files) ? report.files : []

  return {
    ok: report.ok !== false,
    reloaded: Boolean(report.reloaded),
    rolledBack: Boolean(report.rolledBack),
    reason: report.reason ? String(report.reason) : null,
    // The plugin only reads this on the failure path, and it is the difference
    // between "your change was undone" and "your change was undone BECAUSE line
    // 14 is not valid for that field".
    log: report.log ? String(report.log).slice(-4000) : null,
    files: files.map((f) => ({
      path: String(f.path),
      version: f.version ? String(f.version) : null,
      bytes: f.bytes != null ? Number(f.bytes) : null,
      // Both frameworks merge missing defaults on load and save the file back,
      // so the file after a successful reload is regularly not the file we
      // wrote. Saying so keeps an operator from reading it as our bug.
      rewritten: Boolean(f.rewritten),
    })),
  }
}

module.exports = {
  LOCKED_KEYS,
  LOCKED_REASON,
  PATH_SHAPE,
  isPlausiblePath,
  shapeCatalogue,
  shapeFile,
  isBridgeConfig,
  lockedKeysFor,
  lockedChanges,
  summariseReport,
}