// ── Admin · Rust · Mod configuration ──────────────────────────────────────
//
// R18. Four routes: list the tree, read a file, write a file, read what has
// been written lately. Every one of them is a live round trip to a game host —
// nothing here is cached, because a cached config is an edit somebody made over
// SSH that this website then silently overwrote.
//
// ── The write is three steps and the order is the whole design ────────────
//
//  1. **Re-read the file from the host.** Form edits are spliced into the text
//     that is on disk *now*, not into the text a browser was holding. The
//     version the browser presents is checked against the fresh one, and a
//     mismatch is a conflict rather than an overwrite.
//  2. **Compose the new bytes here** (D35). The browser sends pointers and
//     literals; `configEdit` splices them. It never parses and re-serialises,
//     because that is how every untouched `1.0` becomes `1` and how a plugin
//     fails to come back from its reload.
//  3. **Hand the whole file to the plugin**, which version-checks it again,
//     backs the old one up, writes, reloads, and rolls the write back if the
//     plugin does not announce itself. That last part is the feature; this file
//     reports it.
//
// ── What the outcome means ────────────────────────────────────────────────
//
// A `config.report` with `rolledBack: true` is a SUCCESSFUL round trip carrying
// bad news: the edit was undone, the plugin is back on its old config, and the
// admin needs to see the log line that says why. It is not a 5xx, and treating
// it as one would lose the only diagnosis available.

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

const configEdit = require('../../configEdit')
const db = require('../../model/config/config.db')
const model = require('../../model/config/config.model')
const servers = require('../../model/servers/servers.model')
const serversDb = require('../../model/servers/servers.db')
const sidecar = require('../../sidecarClient')

const log = core.logger('admin:config')

/** Reads the server row with its token, or answers 404 once, here. */
async function serverOr404(req, res) {
  const row = servers.withToken(await serversDb.getServer(req.params.serverId))

  if (!row) {
    res.status(404).json({ message: 'No such server' })
    return null
  }

  return row
}

/**
 * Turns a sidecar failure into a sentence an operator can act on.
 *
 * The statuses are the ones `sidecarClient` produces, and each names a different
 * fix: nothing configured, no credential, the wrong protocol, a game that is
 * down, a game that is up and silent.
 */
function unreachable(res, reply, what) {
  const messages = {
    'not-configured': 'That server has no sidecar URL configured',
    'no-token': 'That server has no sidecar token configured',
    'protocol-mismatch': 'That server’s sidecar speaks a different protocol version',
    unauthorized: 'That server’s sidecar rejected the stored token',
    timeout: 'That server’s sidecar did not answer in time',
    'http-503': 'The game is not connected to that server’s sidecar',
    'http-504': 'The game did not answer in time',
  }

  const message = messages[reply.status] || `Could not ${what}`
  return res.status(503).json({ message, status: reply.status })
}

/** Every settings file on one host, grouped by the plugin that probably owns it. */
async function listFiles(req, res) {
  const server = await serverOr404(req, res)
  if (!server) return undefined

  const reply = await sidecar.configFiles(server)
  if (!reply.ok) return unreachable(res, reply, 'read that server’s configuration')

  if (reply.data && reply.data.kind === 'config.error') {
    return res.status(502).json({ message: refusalMessage(reply.data) })
  }

  return res.json(model.shapeCatalogue(reply.data))
}

/** One file: its text, and the reading of it the form is drawn from. */
async function readFile(req, res) {
  const path = String(req.query.path || '')

  if (!model.isPlausiblePath(path)) {
    return res.status(400).json({ message: 'That is not a configuration path' })
  }

  const server = await serverOr404(req, res)
  if (!server) return undefined

  const [fileReply, catalogueReply] = await Promise.all([
    sidecar.configFile(server, path),
    // Asked alongside, because whether this file is OURS decides whether three
    // of its keys are locked (D38) — and the answer is the plugin's own name,
    // never a filename this module matched on.
    sidecar.configFiles(server),
  ])

  if (!fileReply.ok) return unreachable(res, fileReply, 'read that file')

  if (fileReply.data && fileReply.data.kind === 'config.error') {
    return res.status(refusalStatus(fileReply.data)).json({ message: refusalMessage(fileReply.data) })
  }

  const self = catalogueReply.ok && catalogueReply.data ? catalogueReply.data.self : null
  return res.json(model.shapeFile(fileReply.data, { self }))
}

/**
 * Save one file, and reload whatever owns it.
 *
 * Two tiers in one route, because they are one action with two ways of saying
 * what changed: `edits` is the generated form, `text` is the raw editor.
 */
async function writeFile(req, res) {
  const path = String(req.body.path || '')
  const tier = Array.isArray(req.body.edits) ? 'form' : 'raw'
  const reload = req.body.reload ? String(req.body.reload) : null
  const serverId = req.params.serverId

  if (!model.isPlausiblePath(path)) {
    return res.status(400).json({ message: 'That is not a configuration path' })
  }

  const server = await serverOr404(req, res)
  if (!server) return undefined

  const [current, catalogue] = await Promise.all([
    sidecar.configFile(server, path),
    sidecar.configFiles(server),
  ])

  if (!current.ok) return unreachable(res, current, 'read that file')

  if (current.data && current.data.kind === 'config.error') {
    return res.status(refusalStatus(current.data)).json({ message: refusalMessage(current.data) })
  }

  const onDisk = current.data
  const self = catalogue.ok && catalogue.data ? catalogue.data.self : null
  const locked = model.lockedKeysFor(path, self)

  // The browser's version against what is on the host right now. The plugin
  // checks this again before it writes — this check exists so that a conflict
  // is reported with the current file in hand, which is what a person needs to
  // merge their change rather than retype it.
  if (String(req.body.version || '') !== String(onDisk.version)) {
    return res.status(409).json({
      message: 'That file changed on the server since you opened it',
      current: model.shapeFile(onDisk, { self }),
    })
  }

  let text
  let changes

  if (tier === 'form') {
    const applied = configEdit.applyEdits(onDisk.text, req.body.edits, { locked })
    if (applied.error) return res.status(400).json({ message: applied.error })

    text = applied.text
    changes = applied.changes
  } else {
    text = String(req.body.text || '')

    try {
      configEdit.scan(text)
    } catch (err) {
      return res.status(400).json({ message: `That is not valid JSON: ${err.message}` })
    }

    const broken = model.lockedChanges(onDisk.text, text, locked)

    if (broken.length > 0) {
      return res.status(400).json({
        message: `${broken.join(', ')} cannot be changed from the website`,
        locked: broken.map((key) => ({ key, reason: model.LOCKED_REASON[key.toLowerCase()] || null })),
      })
    }

    // A raw save records that the document was replaced rather than a field
    // list, because that is what happened. Pretending to know which keys moved
    // would mean diffing two documents and reporting a guess as an audit fact.
    changes = text === onDisk.text ? [] : [{ path: '(whole file)', from: null, to: null }]
  }

  if (changes.length === 0) {
    return res.json({ changed: false, version: onDisk.version })
  }

  const reply = await sidecar.configWrite(server, {
    files: [{ path, version: onDisk.version, text }],
    ...(reload ? { reload } : {}),
  })

  if (!reply.ok) {
    await record(req, {
      serverId,
      path,
      self,
      reload,
      tier,
      outcome: 'unreachable',
      changes,
      versionBefore: onDisk.version,
      detail: reply.status,
    })

    return unreachable(res, reply, 'write that file')
  }

  if (reply.data && reply.data.kind === 'config.error') {
    await record(req, {
      serverId,
      path,
      self,
      reload,
      tier,
      outcome: 'refused',
      changes,
      versionBefore: onDisk.version,
      detail: refusalMessage(reply.data),
    })

    return res.status(refusalStatus(reply.data)).json({ message: refusalMessage(reply.data) })
  }

  const report = model.summariseReport(reply.data)
  const after = report && report.files[0] ? report.files[0].version : null

  await record(req, {
    serverId,
    path,
    self,
    reload,
    tier,
    outcome: report && report.rolledBack ? 'rolled-back' : 'applied',
    reloaded: Boolean(report && report.reloaded),
    changes,
    versionBefore: onDisk.version,
    versionAfter: after,
    detail: report ? report.reason : null,
  })

  // 200 either way. A rollback is a round trip that worked and an edit that did
  // not, and the body says which — collapsing it into a 5xx would throw away
  // the log line that explains it.
  return res.json({ changed: true, report })
}

/** What has been written to this server's configuration lately, and by whom. */
async function history(req, res) {
  try {
    return res.json({ writes: await db.recentWrites(req.params.serverId, req.query.limit) })
  } catch (err) {
    log.error('failed to read the configuration history', { error: err.message })
    return res.status(500).json({ message: 'Failed to read the configuration history' })
  }
}

/** One audit row, plus the activity entry core owns. Never lets a logging failure fail a save. */
async function record(req, row) {
  try {
    await db.recordWrite({
      ...row,
      plugin: model.isBridgeConfig(row.path, row.self) ? row.self : pluginOf(row.path),
      reloadTarget: row.reload,
      userId: req.user ? req.user.id : null,
    })

    await core.activity.log({
      req,
      action: 'rust.config.write',
      detail: {
        server: row.serverId,
        path: row.path,
        tier: row.tier,
        outcome: row.outcome,
        reload: row.reload || null,
        fields: Array.isArray(row.changes) ? row.changes.length : 0,
      },
    })
  } catch (err) {
    log.error('failed to record a configuration write', { path: row.path, error: err.message })
  }
}

function pluginOf(path) {
  return String(path).includes('/') ? String(path).split('/')[0] : String(path).replace(/\.json$/i, '')
}

/** A `config.error` frame as a sentence. */
function refusalMessage(frame) {
  const reasons = {
    busy: 'Another configuration write on that server is still finishing',
    conflict: 'That file changed on the server since you opened it',
    invalid: 'The game refused that file: it is not valid JSON',
    missing: 'That file is not on that server',
    path: 'That path is not inside the server’s configuration directory',
    'too-large': 'That file is larger than the bridge will carry',
    'too-many': 'That save touches too many files',
    'reload-self': 'The bridge plugin cannot be reloaded from the website',
    'reload-failed': 'The game could not reload that plugin',
    unwritable: 'The game could not write that file',
    unreadable: 'The game could not read that file',
    'no-root': 'That framework reports no configuration directory',
  }

  const base = reasons[frame.reason] || 'The game refused that configuration change'
  return frame.detail ? `${base} (${frame.detail})` : base
}

/** A refusal's status: the caller's fault where it is, the far end's where it is not. */
function refusalStatus(frame) {
  if (frame.reason === 'conflict') return 409
  if (frame.reason === 'busy') return 409
  if (['path', 'missing', 'invalid', 'too-large', 'too-many', 'reload-self'].includes(frame.reason)) return 400
  return 502
}

module.exports = { listFiles, readFile, writeFile, history, refusalMessage, refusalStatus }