import fs from 'node:fs'
import path from 'node:path'
import crypto from 'node:crypto'
import { atomicWriteFile, readJSON, writeJSON, projectIdOf, pageSlugOf } from './util.js'

export const DATA_DIR = process.env.DATA_DIR || path.resolve('./data-dev')

const DOCS_DIR = path.join(DATA_DIR, 'docs')
const SNAP_DIR = path.join(DATA_DIR, 'snapshots')
const REGISTRY = path.join(DATA_DIR, 'registry.json')
const UPLOAD_OWNERS = path.join(DATA_DIR, 'uploads.json')
const AGENTS = path.join(DATA_DIR, 'agents.json')
const MENTIONS = path.join(DATA_DIR, 'mentions.json')
const SECRET_FILE = path.join(DATA_DIR, 'session-secret')

export function initStore() {
  fs.mkdirSync(DOCS_DIR, { recursive: true })
  fs.mkdirSync(SNAP_DIR, { recursive: true })
}

export function sessionSecret() {
  try {
    const s = fs.readFileSync(SECRET_FILE, 'utf8').trim()
    if (s.length >= 32) return s
  } catch {}
  const s = crypto.randomBytes(32).toString('hex')
  atomicWriteFile(SECRET_FILE, s)
  return s
}

// --- doc binary state ---

// Unified projects use `${id}.yjs`. The page-derived path remains here so the
// migration and whole-project deletion can find pre-unification page files.
export function docPath(docName) {
  const id = projectIdOf(docName)
  const slug = pageSlugOf(docName)
  return path.join(DOCS_DIR, slug === 'home' ? `${id}.yjs` : `${id}__${slug}.yjs`)
}

function mdPath(docName) {
  return docPath(docName).replace(/\.yjs$/, '.md')
}

function snapDirFor(docName) {
  return path.join(SNAP_DIR, docName.replace('::', '__'))
}

export function loadDocState(id) {
  try {
    return new Uint8Array(fs.readFileSync(docPath(id)))
  } catch {
    return null
  }
}

// Read a pre-unified page file during the one-time project migration. These
// files are deliberately left in place afterwards as rollback material.
export function loadLegacyPageState(projectId, slug) {
  if (!slug || slug === 'home') return null
  try {
    return new Uint8Array(fs.readFileSync(path.join(DOCS_DIR, `${projectId}__${slug}.yjs`)))
  } catch {
    return null
  }
}

export function saveDocState(docName, update, markdown) {
  atomicWriteFile(docPath(docName), Buffer.from(update))
  if (markdown != null) atomicWriteFile(mdPath(docName), markdown)
  maybeSnapshot(docName, update)
}

const SNAPSHOT_EVERY_MS = 10 * 60 * 1000
const SNAPSHOT_KEEP = 6

function maybeSnapshot(docName, update) {
  const dir = snapDirFor(docName)
  fs.mkdirSync(dir, { recursive: true })
  let files = []
  try {
    files = fs.readdirSync(dir).filter(f => f.endsWith('.yjs')).sort()
  } catch {}
  const last = files.length ? parseInt(files[files.length - 1], 10) : 0
  if (Date.now() - last < SNAPSHOT_EVERY_MS) return
  atomicWriteFile(path.join(dir, `${Date.now()}.yjs`), Buffer.from(update))
  for (const f of files.slice(0, Math.max(0, files.length + 1 - SNAPSHOT_KEEP))) {
    try { fs.unlinkSync(path.join(dir, f)) } catch {}
  }
}

export const UPLOADS_DIR = path.join(DATA_DIR, 'uploads')

const MIME_EXT = { 'image/png': 'png', 'image/jpeg': 'jpg', 'image/gif': 'gif', 'image/webp': 'webp', 'image/svg+xml': 'svg' }

export function saveUpload(buffer, mime, projectId = null) {
  const ext = MIME_EXT[mime]
  if (!ext) return null
  fs.mkdirSync(UPLOADS_DIR, { recursive: true })
  const name = `${crypto.randomBytes(8).toString('hex')}.${ext}`
  atomicWriteFile(path.join(UPLOADS_DIR, name), buffer)
  if (projectId) {
    const owners = readJSON(UPLOAD_OWNERS, {})
    owners[name] = projectId
    writeJSON(UPLOAD_OWNERS, owners)
  }
  return name
}

// Which project an upload was made in. A signed-in user can fetch any upload by
// name, as they always could; a public-link visitor is confined to the project
// their link opens, so an unguessable filename is not the only thing standing
// between a stranger and someone else's figures.
export function uploadProject(name) {
  return readJSON(UPLOAD_OWNERS, {})[name] || null
}

// Remove one page's files (keeps the registry entry)
export function deletePageFiles(docName) {
  for (const f of [docPath(docName), mdPath(docName)]) {
    try { fs.unlinkSync(f) } catch {}
  }
  try { fs.rmSync(snapDirFor(docName), { recursive: true, force: true }) } catch {}
}

// Remove a whole project: every page file + the registry entry
export function deleteDocFiles(id) {
  const reg = getRegistry()
  const pages = Object.keys(reg[id]?.pages || {})
  for (const slug of [...new Set(['home', '_structure', ...pages])]) {
    deletePageFiles(slug === 'home' ? id : `${id}::${slug}`)
  }
  delete reg[id]
  writeJSON(REGISTRY, reg)
}

// --- registry (doc list) ---

export function getRegistry() {
  return readJSON(REGISTRY, {})
}

export function upsertRegistry(id, patch) {
  const reg = getRegistry()
  reg[id] = { ...(reg[id] || {}), ...patch }
  writeJSON(REGISTRY, reg)
  return reg[id]
}

// --- public share links -----------------------------------------------------
// A link is a bearer credential: whoever holds it reads the project. 24 random
// bytes (192 bits) is far past guessable, and the compare is constant-time so a
// scan of the registry cannot be turned into a character-by-character oracle.

export function newShareToken() {
  return crypto.randomBytes(24).toString('base64url')
}

export function docByShareToken(token) {
  if (typeof token !== 'string' || token.length < 32 || token.length > 64) return null
  const given = Buffer.from(token)
  for (const [id, meta] of Object.entries(getRegistry())) {
    if (!meta.shareToken || meta.shareToken.length !== token.length) continue
    if (crypto.timingSafeEqual(Buffer.from(meta.shareToken), given)) return id
  }
  return null
}

// --- doc access control ---

export function canAccessDoc(docName, username) {
  const meta = getRegistry()[projectIdOf(docName)]
  if (!meta || !username) return false
  if (!meta.createdBy) return true // legacy docs created before ACLs
  return meta.createdBy === username || (meta.sharedWith || []).includes(username)
}

// One combined registry touch per doc store, and only when something actually
// changed — registry.json lives on bucket-mounted storage where every sync
// write is expensive (and a hung write blocks the event loop).
export function touchProjectOnStore(projectId, slug, title, subtitle) {
  const reg = getRegistry()
  const meta = reg[projectId]
  if (!meta) return
  const now = Date.now()
  let dirty = now - (meta.updatedAt || 0) > 30000
  const next = { ...meta, updatedAt: now }
  if (slug === 'home') {
    if ((title || 'Untitled') !== meta.title) {
      next.title = title || 'Untitled'
      dirty = true
    }
    // the project's one-line description, from home's opening paragraph. Absent
    // (the paragraph was emptied or never written) drops the key rather than
    // storing a null — a write either way, but only when it really changed.
    const sub = subtitle || null
    if (sub !== (meta.subtitle || null)) {
      if (sub) next.subtitle = sub
      else delete next.subtitle
      dirty = true
    }
  } else {
    const pageTitle = slug === '_structure' ? 'Structure' : title || slug
    if (meta.pages?.[slug]?.title !== pageTitle) {
      next.pages = { ...(meta.pages || {}), [slug]: { ...(meta.pages?.[slug] || {}), title: pageTitle } }
      dirty = true
    }
  }
  if (dirty) {
    reg[projectId] = next
    writeJSON(REGISTRY, reg)
  }
}

// --- pages metadata (inside the project's registry entry) ---

export function upsertPageMeta(projectId, slug, patch) {
  const reg = getRegistry()
  if (!reg[projectId]) return null
  const pages = { ...(reg[projectId].pages || {}) }
  pages[slug] = { ...(pages[slug] || {}), ...patch }
  reg[projectId] = { ...reg[projectId], pages }
  writeJSON(REGISTRY, reg)
  return pages[slug]
}

export function removePageMeta(projectId, slug) {
  const reg = getRegistry()
  if (!reg[projectId]?.pages?.[slug]) return
  const pages = { ...reg[projectId].pages }
  delete pages[slug]
  reg[projectId] = { ...reg[projectId], pages }
  writeJSON(REGISTRY, reg)
}

// Every project has at least the home page; older entries predate `pages`.
export function pagesOf(projectId) {
  const meta = getRegistry()[projectId]
  if (!meta) return null
  return { home: { title: meta.title || 'Untitled' }, ...(meta.pages || {}) }
}

// --- agent handles + app-issued keys ---
// agents.json: { handle: { owner, createdAt, keyHash } } — only the sha256 of
// the key is stored; the plaintext is shown once at registration/rotation.

export function getAgents() {
  return readJSON(AGENTS, {})
}

export function saveAgents(agents) {
  writeJSON(AGENTS, agents)
}

export function hashAgentKey(key) {
  return crypto.createHash('sha256').update(key).digest('hex')
}

export function newAgentKey() {
  return 'ak_' + crypto.randomBytes(24).toString('hex')
}

export function agentByKey(key) {
  if (!key?.startsWith('ak_')) return null
  const hash = hashAgentKey(key)
  for (const [handle, info] of Object.entries(getAgents())) {
    if (info.keyHash && info.keyHash === hash) return { handle, owner: info.owner }
  }
  return null
}

// --- mention tasks ---
// shape: { processed: { [messageId]: true }, tasks: { [mentionId]: task } }

export function getMentionState() {
  return readJSON(MENTIONS, { processed: {}, tasks: {} })
}

export function saveMentionState(state) {
  writeJSON(MENTIONS, state)
}