// ── The authored set, and what it means for one server ────────────────────
//
// This file turns "what an operator wrote on the website" into "what one game
// server's store should contain", which is where four of phase 7's decisions
// actually live:
//
//   D28  a grant is authored against a WEBSITE USER and resolved to every Steam
//        id they have linked, here, at the moment of the push.
//   D29  every authored row carries a scope — one server, or `*` for the fleet —
//        and a server sees only what names it.
//   D30  groups travel as groups. Membership is a separate wire fact from the
//        permissions the group carries, because the game stores them separately
//        and one of the two can fail on its own (§12.2 rule 4).
//   D31  the difference between the desired set and what this site has already
//        pushed is what gets retired. Anything else in the store is drift, and
//        drift is reported rather than undone.
//
// Nothing here talks to a sidecar — `permSync.js` does that. The split is the
// usual one and earns its keep twice over here: the whole of the interesting
// logic is a pure function of four tables, so it is tested without a game, a
// sidecar, or a database.

const crypto = require('node:crypto')

const db = require('./permissions.db')

/** A scope that means every server. Stored, rather than null, so the column never needs a coalesce. */
const FLEET = '*'

/**
 * Permission and group names, as both frameworks store them.
 *
 * Lowercased on the way in, because the store lowers them and a site that did
 * not would author `Kits.VIP`, push it, read back `kits.vip`, and report its own
 * grant as drift for ever.
 */
function normaliseName(value) {
  return String(value || '').trim().toLowerCase()
}

/** Whether a scope reaches a server. */
function inScope(scope, serverId) {
  return scope === FLEET || scope === serverId
}

/**
 * Everything the authoring screen renders, in one read.
 *
 * Assembled here rather than in SQL because the shape is a tree — a group with
 * its permissions and its members — and the alternative is either four round
 * trips per group or one join that repeats every group row once per member.
 */
async function overview() {
  const [groups, groupPermissions, members, grants, sync, drift, catalogue] = await Promise.all([
    db.listGroups(),
    db.listGroupPermissions(),
    db.listGroupMembers(),
    db.listGrants(),
    db.listSync(),
    db.listDrift(),
    db.listCatalogue(),
  ])

  const byGroup = new Map(groups.map((group) => [group.name, { ...group, permissions: [], members: [] }]))

  for (const row of groupPermissions) {
    const group = byGroup.get(row.groupName)
    if (group) group.permissions.push(row.permission)
  }

  // A member with two linked Steam accounts arrives as two rows from the join,
  // and is one person on the screen — holding BOTH accounts, not the first one
  // the join happened to return. The screen needs all of them: a membership is
  // pushed per account, and it can be waiting on one while it landed on another.
  const memberByKey = new Map()

  for (const row of members) {
    const group = byGroup.get(row.groupName)
    if (!group) continue

    const key = `${row.groupName}:${row.userId}`
    let member = memberByKey.get(key)

    if (!member) {
      member = {
        userId: row.userId,
        username: row.username,
        accounts: [],
        addedAt: row.addedAt,
      }
      memberByKey.set(key, member)
      group.members.push(member)
    }

    if (row.steamId) member.accounts.push({ steamId: row.steamId, name: row.playerName || null })
  }

  return {
    groups: [...byGroup.values()],
    grants: collapseGrants(grants),
    servers: sync.map(shapeSync),
    drift,
    catalogue: catalogueByPermission(catalogue),
  }
}

/**
 * One row per grant, not one per linked account.
 *
 * The join in `listGrants` multiplies a grant by the holder's accounts, which is
 * what the push wants and the opposite of what a screen wants.
 */
function collapseGrants(rows) {
  const byId = new Map()

  for (const row of rows) {
    const existing = byId.get(row.id)

    if (!existing) {
      byId.set(row.id, {
        id: row.id,
        userId: row.userId,
        username: row.username,
        permission: row.permission,
        scope: row.scope,
        source: row.source,
        note: row.note,
        grantedAt: row.grantedAt,
        accounts: row.steamId ? [{ steamId: row.steamId, name: row.playerName || null }] : [],
      })

      continue
    }

    if (row.steamId) existing.accounts.push({ steamId: row.steamId, name: row.playerName || null })
  }

  return [...byId.values()]
}

/**
 * The sync row as a client reads it.
 *
 * `report` is stored as the JSON the game sent and parsed here rather than on the
 * way in, so a report this build cannot read is a rendering problem on one
 * screen instead of a write that failed.
 */
function shapeSync(row) {
  let report = null

  if (row.report) {
    try {
      report = JSON.parse(row.report)
    } catch {
      report = null
    }
  }

  return {
    serverId: row.serverId,
    state: row.state,
    dirty: Boolean(row.dirty),
    inSync: Boolean(row.desiredHash) && row.desiredHash === row.syncedHash && row.state === 'ok',
    lastAttemptAt: row.lastAttemptAt,
    lastOkAt: row.lastOkAt,
    error: row.error || null,
    report,
  }
}

/** Which servers know each permission name — the form's option source, and its warning label. */
function catalogueByPermission(rows) {
  const byPermission = new Map()

  for (const row of rows) {
    if (!byPermission.has(row.permission)) byPermission.set(row.permission, [])
    byPermission.get(row.permission).push(row.serverId)
  }

  return [...byPermission.entries()]
    .map(([permission, servers]) => ({ permission, servers }))
    .sort((a, b) => a.permission.localeCompare(b.permission))
}

/**
 * The whole authored set, read once, in the shape the per-server build wants.
 *
 * Read once per sync tick rather than once per server: six servers is six
 * different answers derived from one set of tables, and re-reading them per
 * server is six times the queries for the same rows.
 */
async function readAuthored() {
  const [groups, groupPermissions, members, grants, links] = await Promise.all([
    db.listGroups(),
    db.listGroupPermissions(),
    db.listGroupMembers(),
    db.listGrants(),
    db.listLinks(),
  ])

  const steamIdsByUser = new Map()

  for (const link of links) {
    if (!steamIdsByUser.has(link.userId)) steamIdsByUser.set(link.userId, [])
    steamIdsByUser.get(link.userId).push(link.steamId)
  }

  return { groups, groupPermissions, members, grants, steamIdsByUser }
}

/**
 * What one server's store should contain, and the rows that say so.
 *
 * Returns three things the caller needs together and must not compute twice:
 *
 *   `payload`  what goes on the wire
 *   `rows`     the same set in `rust_perm_pushed`'s shape, for the diff
 *   `hash`     a stable digest of `rows`, which is how the loop knows nothing
 *              has changed without asking a game server
 *
 * **A user with no linked Steam account contributes nothing and is not an
 * error.** They are authored against perfectly well and reach nobody until they
 * link — which the admin screen says out loud, because a grant that reaches
 * nothing looks exactly like one that worked.
 */
function buildDesired(serverId, authored) {
  const { groups, groupPermissions, members, grants, steamIdsByUser } = authored

  const scopedGroups = groups.filter((group) => inScope(group.scope, serverId))
  const groupNames = new Set(scopedGroups.map((group) => group.name))

  const permissionsByGroup = new Map(scopedGroups.map((group) => [group.name, []]))
  const membersByGroup = new Map(scopedGroups.map((group) => [group.name, []]))
  const managed = new Set()
  const rows = []

  for (const group of scopedGroups)
    rows.push({ kind: 'group', subject: group.name, object: '' })

  for (const row of groupPermissions) {
    if (!groupNames.has(row.groupName)) continue

    const permission = normaliseName(row.permission)
    permissionsByGroup.get(row.groupName).push(permission)
    managed.add(permission)
    rows.push({ kind: 'group-permission', subject: row.groupName, object: permission })
  }

  const seenMember = new Set()

  for (const row of members) {
    if (!groupNames.has(row.groupName)) continue

    for (const steamId of steamIdsByUser.get(row.userId) || []) {
      const key = `${row.groupName}:${steamId}`
      if (seenMember.has(key)) continue
      seenMember.add(key)

      membersByGroup.get(row.groupName).push(steamId)
      rows.push({ kind: 'member', subject: steamId, object: row.groupName })
    }
  }

  const permissionsBySteamId = new Map()
  const seenGrant = new Set()

  for (const row of grants) {
    if (!inScope(row.scope, serverId)) continue

    const permission = normaliseName(row.permission)

    // Managed whether or not it reaches anybody: the namespace is what makes a
    // hand grant of this permission to somebody else show up as drift, and a
    // grant whose holder has linked nothing would otherwise silently narrow it.
    managed.add(permission)

    // **Resolved from the link map, not from the row.** `listGrants` joins the
    // links and therefore repeats a grant once per linked account, which would
    // give the right answer here by accident — until somebody changes that query
    // and one of a person's two accounts quietly stops being granted. The map is
    // the same source the members above use, and it says what it means.
    for (const steamId of steamIdsByUser.get(row.userId) || []) {
      const key = `${steamId}:${permission}`
      if (seenGrant.has(key)) continue
      seenGrant.add(key)

      if (!permissionsBySteamId.has(steamId)) permissionsBySteamId.set(steamId, [])
      permissionsBySteamId.get(steamId).push(permission)
      rows.push({ kind: 'grant', subject: steamId, object: permission })
    }
  }

  const payload = {
    groups: scopedGroups.map((group) => ({
      name: group.name,
      title: group.title || group.name,
      rank: group.rank,
      permissions: permissionsByGroup.get(group.name),
      members: membersByGroup.get(group.name),
    })),
    grants: [...permissionsBySteamId.entries()].map(([steamId, permissions]) => ({
      steamId,
      permissions,
    })),
    managed: [...managed].sort(),
  }

  return { payload, rows, hash: hashRows(rows) }
}

/**
 * A digest of the desired set.
 *
 * Sorted before hashing, because the rows come out of several queries in an
 * order nothing guarantees — an unsorted digest would differ between two reads
 * of an unchanged set and push to every game server on every tick.
 */
function hashRows(rows) {
  const canonical = rows
    .map((row) => `${row.kind}${row.subject}${row.object}`)
    .sort()
    .join('\n')

  return crypto.createHash('sha256').update(canonical).digest('hex')
}

/** A row's identity, for set arithmetic against what was pushed. */
const rowKey = (row) => `${row.kind}${row.subject}${row.object}`

/**
 * What this site put in a server and has since withdrawn.
 *
 * `pushed − desired`, and it is the one calculation that cannot be replaced by
 * asking the game: a name in the store that is not in the desired set is either
 * something the site retired or something a human granted, and those have
 * opposite correct answers (D31). Only the pushed ledger tells them apart.
 */
function retirements(pushed, desiredRows) {
  const desired = new Set(desiredRows.map(rowKey))

  return pushed.filter((row) => !desired.has(rowKey(row)))
}

module.exports = {
  FLEET,
  normaliseName,
  inScope,
  overview,
  readAuthored,
  buildDesired,
  retirements,
  hashRows,
  rowKey,
  collapseGrants,
  shapeSync,
}