// Per-Team voice channels (TEAMS.md §7.3, phase 9).
//
// **The site decides; this file compares and applies.** Every judgement — which
// Teams qualify, who may enter, what the channel is called — was made on the site
// and arrives in the request. What cannot be made there is the DIFF: which of
// those people already hold the role, whether the channel still exists, whether
// the category was deleted last week. That is live guild state, only this process
// can see it, and shipping it to the site to be compared and shipped back would
// be a copy of the guild in a database that cannot watch it change.
//
// So the contract is "make it look like this", not "do these calls".
//
// **Access is a per-Team ROLE.** §7.3 designed per-member permission overwrites
// with a role only above ~90 members; the org lead settled on roles always
// (2026-08-18). The channel therefore carries exactly three kinds of overwrite —
// @everyone denied, the Team's role allowed, and each operator-designated staff
// role allowed — and membership is the role's member list rather than a hundred
// entries on the channel.
const { ChannelType, PermissionFlagsBits } = require('discord.js')

const createLogger = require('../utils/logger')

const log = createLogger('team-voice')

// The category every Team channel is created under. Created on the first pass
// that needs one; the site stores the id and sends it back next time.
const CATEGORY_NAME = 'Teams'

// discord.js REST error codes for "the thing you are addressing is already gone".
// A teardown that finds its target missing has SUCCEEDED — the desired end state
// holds — and the same is true of a sync that finds a channel a human deleted,
// which simply becomes a create.
const UNKNOWN_CHANNEL = 10003
const UNKNOWN_ROLE = 10011

const isMissing = (err) => err && (err.code === UNKNOWN_CHANNEL || err.code === UNKNOWN_ROLE)

// What a Team member may do in their channel, and what @everyone may not. Both
// halves are needed: denying ViewChannel alone still leaves Connect resolvable
// for anyone who has the id, and allowing ViewChannel alone shows a channel
// nobody can enter.
const ACCESS_BITS = [PermissionFlagsBits.ViewChannel, PermissionFlagsBits.Connect]

/**
 * Can this bot do §7.3's job in this guild?
 *
 * Asked before an operator may switch voice on, and again at the top of every
 * pass. The site has no way to know: the operator invites the bot by hand, there
 * is no invite URL with a permission integer anywhere in this project, and an
 * unticked box means every call fails with nothing to point at.
 *
 * `bot_role_position` is reported because it is the second, quieter failure:
 * ManageRoles lets the bot create a role, but it can only GRANT roles below its
 * own highest one. A bot sitting at the bottom of the role list creates roles it
 * then cannot hand to anybody — which looks exactly like a channel nobody can
 * enter, with no error anywhere.
 */
async function preflight(client, guildId) {
  const guild = await client.guilds.fetch(guildId)
  const me = guild.members.me || (await guild.members.fetchMe())
  return {
    connected: true,
    guild_id: guild.id,
    can_manage_channels: me.permissions.has(PermissionFlagsBits.ManageChannels),
    can_manage_roles: me.permissions.has(PermissionFlagsBits.ManageRoles),
    // The guild's whole role list, not just the ones this feature made. The
    // 250-role cap is guild-wide and shared with everything the operator created
    // themselves, so counting ours would promise headroom that is not there.
    role_count: guild.roles.cache.size,
    bot_role_position: me.roles.highest.position,
  }
}

/** The `Teams` category, reusing the one we were given when it is still there. */
async function ensureCategory(guild, categoryId) {
  if (categoryId) {
    const existing = await guild.channels.fetch(categoryId).catch(() => null)
    if (existing && existing.type === ChannelType.GuildCategory) return existing
    log.warn('the configured Teams category is gone; making another', { categoryId })
  }
  const created = await guild.channels.create({
    name: CATEGORY_NAME,
    type: ChannelType.GuildCategory,
    reason: 'Team voice channels',
  })
  log.info('created the Teams category', { categoryId: created.id })
  return created
}

/**
 * The Team's own role.
 *
 * A rename is applied but never allowed to fail the pass: a Team's name is the
 * least important thing here and Discord rate-limits name edits hard, so losing
 * one is worth strictly less than losing the access change in the same request.
 */
async function ensureRole(guild, roleId, name) {
  let role = roleId ? await guild.roles.fetch(roleId).catch(() => null) : null
  let created = false
  if (!role) {
    role = await guild.roles.create({
      name,
      // Not mentionable and not hoisted: this role exists to open a door, and a
      // Team with two hundred members should not become a way to ping them all or
      // a second copy of the member list down the sidebar.
      mentionable: false,
      hoist: false,
      reason: 'Team voice access',
    })
    created = true
    log.info('created a team role', { roleId: role.id, name })
  } else if (role.name !== name) {
    await role.setName(name, 'Team renamed').catch((err) => {
      log.warn('could not rename the team role', { roleId: role.id, message: err.message })
    })
  }
  return { role, created }
}

/** The overwrites a Team channel carries, in the order Discord takes them. */
function overwritesFor(guild, role, staffRoleIds) {
  const overwrites = [
    { id: guild.roles.everyone.id, deny: ACCESS_BITS },
    { id: role.id, allow: ACCESS_BITS },
  ]
  for (const staffId of staffRoleIds) {
    // A staff role the operator has since deleted would make Discord reject the
    // WHOLE set, taking the Team's own grant down with it. Filtered here rather
    // than validated on the site, which cannot see the guild's role list.
    if (!guild.roles.cache.has(staffId)) {
      log.warn('a configured staff role is not in this guild; skipping it', { roleId: staffId })
      continue
    }
    overwrites.push({ id: staffId, allow: ACCESS_BITS })
  }
  return overwrites
}

async function ensureChannel(guild, channelId, { name, category, role, staffRoleIds }) {
  const overwrites = overwritesFor(guild, role, staffRoleIds)
  let channel = channelId ? await guild.channels.fetch(channelId).catch(() => null) : null

  if (channel && channel.type !== ChannelType.GuildVoice) {
    // Somebody pointed us at, or converted this into, something that is not a
    // voice channel. Not ours to repurpose — make the right one and leave theirs.
    log.warn('the stored channel is not a voice channel; making a new one', { channelId })
    channel = null
  }

  if (!channel) {
    const created = await guild.channels.create({
      name,
      type: ChannelType.GuildVoice,
      parent: category.id,
      permissionOverwrites: overwrites,
      reason: 'Team voice channel',
    })
    log.info('created a team voice channel', { channelId: created.id, name })
    return { channel: created, created: true }
  }

  // Overwrites are re-set on every pass rather than diffed: the set is three or
  // four entries, `set` is one API call, and re-asserting it is what repairs a
  // channel somebody edited by hand.
  await channel.permissionOverwrites.set(overwrites, 'Team voice access')
  if (channel.parentId !== category.id) {
    await channel.setParent(category.id, { lockPermissions: false, reason: 'Team voice channel' })
  }
  if (channel.name !== name) {
    await channel.setName(name, 'Team renamed').catch((err) => {
      log.warn('could not rename the team voice channel', { channelId: channel.id, message: err.message })
    })
  }
  return { channel, created: false }
}

/**
 * Bring the role's member list to the site's list, up to `maxOps` changes.
 *
 * **Bounded, and the remainder is reported rather than dropped.** Each grant is
 * its own API call under its own rate limit, so an unbounded first pass on a
 * large guild is a request that outlives its own timeout — and a timeout is the
 * one outcome that leaves the site not knowing what was applied. The site asks
 * again until `pending` reaches zero.
 *
 * **A member the site names who is not in this guild is skipped silently.** They
 * linked their Discord account to the site and never joined the guild, which is
 * an ordinary state (§2.6 hop 3 without hop 4) and not something an operator
 * needs to see a hundred of.
 */
async function syncRoleMembers(guild, role, memberIds, maxOps) {
  // One fetch of the whole member list, so `role.members` and the "are they even
  // here" check both read from a cache that is actually populated. discord.js
  // keeps it current from gateway events afterwards; without the fetch, a bot
  // that has been up for five minutes knows only the members who spoke.
  await guild.members.fetch()

  const desired = new Set(memberIds.map(String))
  const current = new Set(role.members.map((member) => member.id))

  const toAdd = [...desired].filter((id) => !current.has(id) && guild.members.cache.has(id))
  const toRemove = [...current].filter((id) => !desired.has(id))

  let ops = 0
  let added = 0
  let removed = 0

  for (const id of toAdd) {
    if (ops >= maxOps) break
    const member = guild.members.cache.get(id)
    try {
      // eslint-disable-next-line no-await-in-loop
      await member.roles.add(role, 'Team member')
      added += 1
    } catch (err) {
      // One member the bot cannot touch — almost always the role hierarchy, when
      // the member outranks the bot — must not cost the other forty-nine.
      log.warn('could not grant the team role', { userId: id, roleId: role.id, message: err.message })
    }
    ops += 1
  }

  for (const id of toRemove) {
    if (ops >= maxOps) break
    const member = guild.members.cache.get(id)
    if (!member) continue
    try {
      // eslint-disable-next-line no-await-in-loop
      await member.roles.remove(role, 'No longer a team member')
      removed += 1
    } catch (err) {
      log.warn('could not revoke the team role', { userId: id, roleId: role.id, message: err.message })
    }
    ops += 1
  }

  return { added, removed, pending: Math.max(0, toAdd.length + toRemove.length - ops) }
}

/** One Team, reconciled. */
async function syncTeamVoice(client, guildId, {
  teamId, name, categoryId, channelId, roleId, staffRoleIds = [], memberIds = [], maxMemberOps = 50,
}) {
  const guild = await client.guilds.fetch(guildId)
  const category = await ensureCategory(guild, categoryId)
  const { role, created: roleCreated } = await ensureRole(guild, roleId, name)
  const { channel, created: channelCreated } = await ensureChannel(guild, channelId, {
    name, category, role, staffRoleIds,
  })
  const members = await syncRoleMembers(guild, role, memberIds, maxMemberOps)

  log.info('team voice reconciled', {
    teamId, name, channelId: channel.id, roleId: role.id, ...members,
  })

  return {
    category_id: category.id,
    channel_id: channel.id,
    role_id: role.id,
    created: { channel: channelCreated, role: roleCreated },
    members,
  }
}

/**
 * Remove a Team's channel and role.
 *
 * Both, in one call, because they are one lifecycle: deleting the channel and
 * leaving the role would leave every member wearing a badge for a place that no
 * longer exists. Either being already gone is success.
 */
async function removeTeamVoice(client, guildId, { channelId, roleId }) {
  const guild = await client.guilds.fetch(guildId)
  const result = { channel_deleted: false, role_deleted: false }

  if (channelId) {
    const channel = await guild.channels.fetch(channelId).catch(() => null)
    if (channel) {
      try {
        await channel.delete('Team no longer qualifies for a voice channel')
        result.channel_deleted = true
      } catch (err) {
        if (!isMissing(err)) throw err
      }
    }
  }

  if (roleId) {
    const role = await guild.roles.fetch(roleId).catch(() => null)
    if (role) {
      try {
        await role.delete('Team no longer qualifies for a voice channel')
        result.role_deleted = true
      } catch (err) {
        if (!isMissing(err)) throw err
      }
    }
  }

  log.info('team voice removed', { channelId, roleId, ...result })
  return result
}

module.exports = {
  CATEGORY_NAME,
  ACCESS_BITS,
  preflight,
  ensureCategory,
  ensureRole,
  ensureChannel,
  overwritesFor,
  syncRoleMembers,
  syncTeamVoice,
  removeTeamVoice,
}