'use strict'

const crypto = require('hypercore-crypto')
const b4a = require('b4a')

function checksumSettingsSnapshot (obj) {
  const json = JSON.stringify(obj || {})
  return b4a.toString(crypto.hash(b4a.from(json)), 'hex').slice(0, 16)
}

/**
 * Prune compose drafts for deleted or inaccessible channels (P409-18).
 */
function pruneStaleComposeDrafts (composeDrafts, { channelIds, canPostByChannel = {} } = {}) {
  const allowed = new Set(channelIds || [])
  const out = { ...(composeDrafts || {}) }
  const removed = []
  for (const chId of Object.keys(out)) {
    if (!allowed.has(chId)) {
      removed.push(chId)
      delete out[chId]
      continue
    }
    if (canPostByChannel[chId] === false) {
      removed.push(chId)
      delete out[chId]
    }
  }
  return { composeDrafts: out, removed }
}

/**
 * Cross-reference messages, reactions, pins before renderer (P409-17).
 */
function auditMessageReactionCrossRefs ({
  messages = [],
  messageById = {},
  reactions = {},
  pins = []
} = {}) {
  const historyIds = new Set(messages.map((m) => m.id))
  const issues = []
  for (const messageId of Object.keys(reactions)) {
    if (!messageById[messageId] && !historyIds.has(messageId)) {
      issues.push({ kind: 'reaction-orphan', messageId })
    }
  }
  for (const pin of pins) {
    const mid = pin.messageId
    if (!mid) continue
    if (!pin.message && !messageById[mid] && !historyIds.has(mid)) {
      issues.push({ kind: 'pin-missing-body', messageId: mid })
    }
  }
  return {
    ok: issues.length === 0,
    issueCount: issues.length,
    issues: issues.slice(0, 32)
  }
}

/**
 * Safe pin row when message body missing (P409-19).
 */
function pinWithMessageFallback (pin, messageById = {}) {
  if (!pin?.messageId) return pin
  if (pin.message) return pin
  const embedded = messageById[pin.messageId]
  if (!embedded) {
    return {
      ...pin,
      message: {
        id: pin.messageId,
        content: '(message unavailable)',
        displayContent: '(message unavailable)',
        authorId: pin.authorId || null,
        missing: true
      }
    }
  }
  return { ...pin, message: embedded }
}

module.exports = {
  checksumSettingsSnapshot,
  pruneStaleComposeDrafts,
  auditMessageReactionCrossRefs,
  pinWithMessageFallback
}