import { create } from 'zustand'
import { getToken, saveToken } from '../utils/api'

const THEME_KEY = 'owngpt_theme'
const PROVIDER_KEY = 'owngpt_provider'
const MODEL_KEY = 'owngpt_model'
const MODE_KEY = 'owngpt_mode'
const SIDEBAR_KEY = 'owngpt_sidebar_open'
const VALID_THEME_PREFERENCES = new Set(['system', 'light', 'dark'])
const THEME_COLORS = {
  dark: '#212121',
  light: '#ffffff',
}

const MODE_CONFIG = {
  chat: {
    id: 'chat',
    label: 'Chat',
    description: 'Balanced conversation for general help.',
  },
  research: {
    id: 'research',
    label: 'Research',
    description: 'Biases the assistant toward search-heavy responses.',
  },
  coding: {
    id: 'coding',
    label: 'Coding',
    description: 'Focuses on implementation, debugging, and code generation.',
  },
  document: {
    id: 'document',
    label: 'Document Q&A',
    description: 'Optimized for file-grounded answers and summaries.',
  },
}

export const CHAT_MODES = Object.values(MODE_CONFIG)

function createId() {
  if (typeof crypto !== 'undefined' && crypto.randomUUID) {
    return crypto.randomUUID()
  }
  return `id-${Math.random().toString(36).slice(2, 11)}`
}

function readStorage(key, fallback) {
  if (typeof window === 'undefined') return fallback
  const value = window.localStorage.getItem(key)
  return value ?? fallback
}

function getSystemTheme() {
  if (
    typeof window !== 'undefined' &&
    typeof window.matchMedia === 'function' &&
    window.matchMedia('(prefers-color-scheme: light)').matches
  ) {
    return 'light'
  }
  return 'dark'
}

function readTheme() {
  const storedTheme = readStorage(THEME_KEY, 'system')
  if (VALID_THEME_PREFERENCES.has(storedTheme)) return storedTheme
  return 'system'
}

function resolveTheme(themePreference) {
  return themePreference === 'system' ? getSystemTheme() : themePreference
}

function readBoolean(key, fallback) {
  const value = readStorage(key, String(fallback))
  return value === 'true'
}

function writeStorage(key, value) {
  if (typeof window === 'undefined') return
  window.localStorage.setItem(key, String(value))
}

function applyTheme(themePreference) {
  if (typeof document === 'undefined') return

  const resolvedTheme = resolveTheme(themePreference)

  document.documentElement.setAttribute('data-theme', resolvedTheme)
  document.documentElement.setAttribute('data-theme-preference', themePreference)
  document.documentElement.style.colorScheme = resolvedTheme

  const themeColor = document.querySelector('meta[name="theme-color"]')
  if (themeColor) {
    themeColor.setAttribute('content', THEME_COLORS[resolvedTheme] || THEME_COLORS.dark)
  }

  return resolvedTheme
}

const initialThemePreference = readTheme()
const initialTheme = applyTheme(initialThemePreference)

export function encodeSharePayload(payload) {
  if (typeof window === 'undefined') return ''
  return window.btoa(unescape(encodeURIComponent(JSON.stringify(payload))))
}

export function decodeSharePayload(hash) {
  if (typeof window === 'undefined' || !hash.startsWith('#share=')) return null
  try {
    const raw = hash.replace('#share=', '')
    return JSON.parse(decodeURIComponent(escape(window.atob(raw))))
  } catch {
    return null
  }
}

export const useAppStore = create((set, get) => ({
  token: getToken(),
  theme: initialTheme,
  themePreference: initialThemePreference,
  sidebarOpen: readBoolean(SIDEBAR_KEY, true),
  currentSessionId: null,
  currentSessionTitle: 'New Chat',
  provider: readStorage(PROVIDER_KEY, 'groq'),
  model: readStorage(MODEL_KEY, 'llama-3.3-70b-versatile'),
  mode: readStorage(MODE_KEY, 'chat'),
  composerText: '',
  attachments: [],
  authMode: null,
  activeModal: null,
  modalPayload: null,
  sessionSearch: '',
  sidePanel: null,
  selectedFile: null,
  sharedConversation: null,
  toasts: [],
  speakingMessageId: null,
  setToken: (token) => {
    saveToken(token)
    set({ token })
  },
  hydrateToken: () => {
    set({ token: getToken() })
  },
  setThemePreference: (themePreference) => {
    const nextPreference = VALID_THEME_PREFERENCES.has(themePreference) ? themePreference : 'system'
    writeStorage(THEME_KEY, nextPreference)
    const theme = applyTheme(nextPreference)
    set({ themePreference: nextPreference, theme })
  },
  setTheme: (themePreference) => get().setThemePreference(themePreference),
  syncSystemTheme: () => {
    if (get().themePreference !== 'system') return
    const theme = applyTheme('system')
    set({ theme })
  },
  setSidebarOpen: (sidebarOpen) => {
    writeStorage(SIDEBAR_KEY, sidebarOpen)
    set({ sidebarOpen })
  },
  toggleSidebar: () => {
    const next = !get().sidebarOpen
    writeStorage(SIDEBAR_KEY, next)
    set({ sidebarOpen: next })
  },
  setCurrentSession: (currentSessionId, currentSessionTitle = 'New Chat') =>
    set({
      currentSessionId,
      currentSessionTitle,
      selectedFile: null,
      sidePanel: null,
      sharedConversation: null,
    }),
  renameCurrentSession: (currentSessionTitle) => set({ currentSessionTitle }),
  startNewChat: () =>
    set({
      currentSessionId: null,
      currentSessionTitle: 'New Chat',
      composerText: '',
      attachments: [],
      selectedFile: null,
      sidePanel: null,
      sharedConversation: null,
    }),
  setComposerText: (composerText) => set({ composerText }),
  addAttachment: (attachment) =>
    set((state) => ({
      attachments: [
        ...state.attachments,
        {
          ...attachment,
          localId: attachment.localId || createId(),
        },
      ],
    })),
  removeAttachment: (localId) =>
    set((state) => ({
      attachments: state.attachments.filter((attachment) => attachment.localId !== localId),
    })),
  clearAttachments: () => set({ attachments: [] }),
  setMode: (mode) => {
    writeStorage(MODE_KEY, mode)
    set({ mode })
  },
  setProviderModel: (provider, model) => {
    writeStorage(PROVIDER_KEY, provider)
    writeStorage(MODEL_KEY, model)
    set({ provider, model })
  },
  openAuth: (authMode = 'login') => set({ activeModal: 'auth', authMode }),
  closeAuth: () => set({ activeModal: null, authMode: null }),
  openModal: (activeModal, modalPayload = null) => set({ activeModal, modalPayload }),
  closeModal: () => set({ activeModal: null, modalPayload: null }),
  setSessionSearch: (sessionSearch) => set({ sessionSearch }),
  setSidePanel: (sidePanel) => set({ sidePanel }),
  previewFile: (selectedFile) => set({ selectedFile, sidePanel: 'file' }),
  clearSelectedFile: () => set({ selectedFile: null, sidePanel: null }),
  setSharedConversation: (sharedConversation) =>
    set({
      sharedConversation,
      currentSessionId: null,
      currentSessionTitle: sharedConversation?.title || 'Shared Conversation',
    }),
  clearSharedConversation: () => set({ sharedConversation: null }),
  addToast: ({ title, description = '', variant = 'info', duration = 4200 }) => {
    const id = createId()
    set((state) => ({
      toasts: [...state.toasts, { id, title, description, variant, duration }],
    }))
    if (typeof window !== 'undefined') {
      window.setTimeout(() => {
        get().removeToast(id)
      }, duration)
    }
    return id
  },
  removeToast: (id) =>
    set((state) => ({
      toasts: state.toasts.filter((toast) => toast.id !== id),
    })),
  setSpeakingMessageId: (speakingMessageId) => set({ speakingMessageId }),
}))