/**
 * useThreads — multi-conversation sidebar with IndexedDB persistence.
 * Each thread has its own message list (separate IDB key).
 */
import { useCallback, useEffect, useState } from 'react'
import { get, set, del } from 'idb-keyval'

const THREADS_META_KEY = 'careless-threads-meta'

export interface ThreadMeta {
  id: string
  title: string
  createdAt: number
  updatedAt: number
  messageCount: number
  pinned?: boolean
  archived?: boolean
}

export function threadKey(id: string) { return `careless-thread-${id}` }

export function useThreads() {
  const [threads, setThreads] = useState<ThreadMeta[]>([])
  const [activeId, setActiveId] = useState<string | null>(null)

  const load = useCallback(async () => {
    const meta = (await get<ThreadMeta[]>(THREADS_META_KEY)) || []
    setThreads(meta)
    if (!activeId && meta.length) setActiveId(meta[0].id)
  }, [activeId])

  useEffect(() => { load() }, [])

  const save = async (next: ThreadMeta[]) => {
    await set(THREADS_META_KEY, next)
    setThreads(next)
  }

  const create = useCallback(async (title = 'New thread') => {
    const id = 't-' + Date.now().toString(36) + '-' + Math.random().toString(36).slice(2, 6)
    const meta: ThreadMeta = {
      id, title, createdAt: Date.now(), updatedAt: Date.now(), messageCount: 0,
    }
    await save([meta, ...threads])
    setActiveId(id)
    return id
  }, [threads])

  const remove = useCallback(async (id: string) => {
    await del(threadKey(id))
    const next = threads.filter(t => t.id !== id)
    await save(next)
    if (activeId === id) setActiveId(next[0]?.id || null)
  }, [threads, activeId])

  const rename = useCallback(async (id: string, title: string) => {
    await save(threads.map(t => t.id === id ? { ...t, title, updatedAt: Date.now() } : t))
  }, [threads])

  const togglePin = useCallback(async (id: string) => {
    await save(threads.map(t => t.id === id ? { ...t, pinned: !t.pinned } : t))
  }, [threads])

  const updateMeta = useCallback(async (id: string, patch: Partial<ThreadMeta>) => {
    await save(threads.map(t => t.id === id ? { ...t, ...patch, updatedAt: Date.now() } : t))
  }, [threads])

  return {
    threads, activeId, setActiveId,
    create, remove, rename, togglePin, updateMeta, reload: load,
    storageKey: activeId ? threadKey(activeId) : null,
  }
}