import { defineStore } from 'pinia'
import { ref, computed } from 'vue'
import * as api from '../api/client.js'

/**
 * Session-storage key for last visited folder per connection.
 * Only folder navigation state is stored — never tokens or credentials.
 */
function folderSessionKey(connectionId) {
  return `docuvault:cloud:folder:${connectionId}`
}

/**
 * Valid health state values used by both browser compact status and Settings diagnostics.
 * Translates server vocabulary to UI-actionable states (D-12).
 *
 * healthy          — provider reachable and credentials valid
 * requires_reauth  — credentials expired or revoked; reconnect required (D-14/D-15)
 * degraded         — transient outage; credentials preserved, retry/reconnect allowed (D-15)
 * unknown          — not yet tested or health state unavailable
 */
const VALID_HEALTH_STATES = new Set(['healthy', 'requires_reauth', 'degraded', 'unknown'])

export function saveLastFolder(connectionId, folderId) {
  try {
    if (folderId && folderId !== 'root') {
      sessionStorage.setItem(folderSessionKey(connectionId), folderId)
    } else {
      sessionStorage.removeItem(folderSessionKey(connectionId))
    }
  } catch {
    // sessionStorage unavailable — ignore
  }
}

export function loadLastFolder(connectionId) {
  try {
    return sessionStorage.getItem(folderSessionKey(connectionId)) || null
  } catch {
    return null
  }
}

export const useCloudConnectionsStore = defineStore('cloudConnections', () => {
  const connections = ref([])
  const loading = ref(false)
  const error = ref(null)

  // Active browse state (populated by CloudFolderView)
  const selectedConnectionId = ref(null)
  const browseItems = ref([])
  const browseLoading = ref(false)
  const browseError = ref(null)
  /** Capabilities for the currently selected connection */
  const capabilities = ref(null)
  /** 'refreshing' | 'fresh' | 'stale' | null */
  const folderFreshness = ref(null)
  const lastRefreshedAt = ref(null)
  /** 'cached' | 'cloud_only' | null */
  const byteAvailability = ref(null)

  /**
   * D-12: Connection health state map — single source for both browser compact status
   * and Settings full diagnostics.
   *
   * Key: connection UUID
   * Value: { state: 'healthy'|'requires_reauth'|'degraded'|'unknown', error_code, error_message, checked_at }
   *
   * Neither the browser nor Settings translate server states independently —
   * they read from this map only.
   */
  const connectionHealth = ref({})

  /**
   * D-13 / D-14: Set of connection IDs that need a health retest.
   * CloudFolderView reads this and performs the test after navigation settles.
   * Cleared after the test is performed.
   */
  const pendingHealthRetest = ref(new Set())

  /**
   * D-14: Flag set during reconnect so CloudFolderView refreshes the current folder
   * after a successful reconnect without clearing cached browse items first.
   */
  const reconnectRefreshPending = ref(false)

  const selectedConnection = computed(() =>
    connections.value.find(c => c.id === selectedConnectionId.value) ?? null
  )

  async function fetchConnections() {
    loading.value = true
    error.value = null
    try {
      const data = await api.listCloudConnections()
      connections.value = data.items ?? []
    } catch (e) {
      error.value = e.message || 'Failed to load cloud connections'
    } finally {
      loading.value = false
    }
  }

  async function disconnect(id) {
    try {
      await api.disconnectCloud(id)
      connections.value = connections.value.filter(c => c.id !== id)
      if (selectedConnectionId.value === id) {
        selectedConnectionId.value = null
      }
    } catch (e) {
      throw e
    }
  }

  async function disconnectAll() {
    const ids = connections.value.map(c => c.id)
    for (const id of ids) await disconnect(id)
    connections.value = []
  }

  /**
   * Rename a connection's display_name via the API.
   * Only updates the single returned connection in state.
   */
  async function rename(id, displayName) {
    const trimmed = displayName?.trim()
    if (!trimmed) throw new Error('Display name cannot be empty')
    const updated = await api.renameCloudConnection(id, trimmed)
    const idx = connections.value.findIndex(c => c.id === id)
    if (idx !== -1) {
      connections.value[idx] = { ...connections.value[idx], ...updated }
    }
    return updated
  }

  /**
   * Default display_name for a connection.
   * If another connection shares the same provider, append a 4-char UUID suffix.
   */
  function defaultDisplayName(connection) {
    const providerLabel = {
      google_drive: 'Google Drive',
      onedrive: 'OneDrive',
      nextcloud: 'Nextcloud',
      webdav: 'WebDAV',
    }[connection.provider] ?? connection.provider
    const siblings = connections.value.filter(
      c => c.provider === connection.provider && c.id !== connection.id
    )
    if (siblings.length > 0) {
      return `${providerLabel} (${connection.id.slice(0, 4)})`
    }
    return providerLabel
  }

  function selectConnection(id) {
    selectedConnectionId.value = id
    browseItems.value = []
    browseError.value = null
    capabilities.value = null
    folderFreshness.value = null
    lastRefreshedAt.value = null
    byteAvailability.value = null
  }

  function setBrowseState({ items, caps, freshness, refreshedAt, byteAvail, err }) {
    if (err !== undefined) browseError.value = err
    if (items !== undefined) browseItems.value = items
    if (caps !== undefined) capabilities.value = caps
    if (freshness !== undefined) folderFreshness.value = freshness
    if (refreshedAt !== undefined) lastRefreshedAt.value = refreshedAt
    if (byteAvail !== undefined) byteAvailability.value = byteAvail
  }

  /**
   * D-12: Set the health state for a specific connection.
   * Translates server health payload to the UI-actionable vocabulary.
   * Both browser compact status and Settings diagnostics consume this.
   *
   * @param {string} id — connection UUID
   * @param {{ state: string, error_code?: string, error_message?: string, checked_at?: string }} healthData
   */
  function setConnectionHealth(id, healthData) {
    const state = VALID_HEALTH_STATES.has(healthData?.state) ? healthData.state : 'unknown'
    connectionHealth.value = {
      ...connectionHealth.value,
      [id]: {
        state,
        error_code: healthData?.error_code ?? null,
        error_message: healthData?.error_message ?? null,
        checked_at: healthData?.checked_at ?? null,
      },
    }
  }

  /**
   * D-13: Mark a connection as requiring a health retest after a credential failure.
   * This is the complement of the no-probe-on-navigation rule:
   * probes happen only after failures (here), not on ordinary navigation.
   *
   * @param {string} id — connection UUID
   * @param {{ state: string, error_code?: string }} failureData
   */
  function handleHealthFailure(id, failureData) {
    // Record the failure state in the health map
    setConnectionHealth(id, failureData)
    // Schedule a retest (D-13: auto-test after credential failure)
    pendingHealthRetest.value = new Set([...pendingHealthRetest.value, id])
  }

  /**
   * D-14: Mark that a reconnect just completed and the current folder should refresh.
   * Does NOT clear browse items — they stay visible as stale while the refresh runs.
   *
   * @param {string} id — connection UUID
   */
  function markReconnectRefreshPending(id) {
    reconnectRefreshPending.value = true
    // Keep browse items visible but downgrade freshness to stale (D-14)
    if (folderFreshness.value !== null) {
      folderFreshness.value = 'stale'
    }
  }

  /**
   * D-14: Enter reconnecting state — preserve cached items as stale.
   * Does NOT call selectConnection (which clears items).
   *
   * @param {string} id — connection UUID
   */
  function markReconnecting(id) {
    // D-14: cached metadata remains visible; downgrade freshness only
    if (folderFreshness.value !== null) {
      folderFreshness.value = 'stale'
    }
    // Set health to unknown while reconnect is in flight
    connectionHealth.value = {
      ...connectionHealth.value,
      [id]: { state: 'unknown', error_code: null, error_message: null, checked_at: null },
    }
  }

  /**
   * D-13: Explicitly test the health of a connection.
   * Only called after connect/reconnect/failure — never as a navigation side effect.
   *
   * @param {string} id — connection UUID
   * @returns {Promise<{ state: string }>}
   */
  async function testConnection(id) {
    try {
      const result = await api.testCloudConnection(id)
      const state = result?.state ?? 'unknown'
      setConnectionHealth(id, { state, ...result })
      // Clear pending retest flag for this connection
      const next = new Set(pendingHealthRetest.value)
      next.delete(id)
      pendingHealthRetest.value = next
      return result
    } catch (e) {
      const failState = { state: 'degraded', error_code: 'probe_error', error_message: e?.message ?? 'Health check failed' }
      setConnectionHealth(id, failState)
      return failState
    }
  }

  /**
   * D-13: Store-level reconnect handler.
   * Marks reconnecting state (cached items preserved), then fetches updated connections.
   *
   * @param {string} id — connection UUID
   */
  async function reconnect(id) {
    markReconnecting(id)
    // Re-fetch connection list to pick up updated status
    await fetchConnections()
    markReconnectRefreshPending(id)
  }

  /**
   * D-12 / D-13: Connections with null or absent health are candidates for an initial test.
   * The store exposes this as a computed so the view can decide when to run tests.
   */
  const connectionsNeedingHealthCheck = computed(() =>
    connections.value.filter(c => {
      const h = connectionHealth.value[c.id]
      return !h || h.state === undefined || h.state === 'unknown'
    })
  )

  /**
   * D-12: Retrieve the health state for a specific connection.
   * Returns { state: 'unknown', ... } if no health data is available.
   *
   * @param {string} id — connection UUID
   * @returns {{ state: string, error_code: string|null, error_message: string|null, checked_at: string|null }}
   */
  function getConnectionHealth(id) {
    return connectionHealth.value[id] ?? { state: 'unknown', error_code: null, error_message: null, checked_at: null }
  }

  return {
    connections,
    loading,
    error,
    selectedConnectionId,
    selectedConnection,
    browseItems,
    browseLoading,
    browseError,
    capabilities,
    folderFreshness,
    lastRefreshedAt,
    byteAvailability,
    // D-12: health state map — single source for browser and Settings
    connectionHealth,
    // D-13: pending health retests (after credential failures)
    pendingHealthRetest,
    // D-14: reconnect refresh flag
    reconnectRefreshPending,
    // D-12: connections needing initial health check
    connectionsNeedingHealthCheck,
    fetchConnections,
    disconnect,
    disconnectAll,
    rename,
    defaultDisplayName,
    selectConnection,
    setBrowseState,
    // D-12/D-13: health management
    setConnectionHealth,
    getConnectionHealth,
    handleHealthFailure,
    markReconnectRefreshPending,
    markReconnecting,
    testConnection,
    reconnect,
  }
})