import React from 'react'
import {BskyAgent, AtpPersistSessionHandler} from '@atproto/api'
import {useQueryClient} from '@tanstack/react-query'
import {jwtDecode} from 'jwt-decode'

import {networkRetry} from '#/lib/async/retry'
import {logger} from '#/logger'
import * as persisted from '#/state/persisted'
import {PUBLIC_BSKY_AGENT} from '#/state/queries'
import {IS_PROD} from '#/lib/constants'
import {emitSessionDropped} from '../events'
import {useLoggedOutViewControls} from '#/state/shell/logged-out'
import {useCloseAllActiveElements} from '#/state/util'
import {track} from '#/lib/analytics/analytics'

let __globalAgent: BskyAgent = PUBLIC_BSKY_AGENT

/**
 * NOTE
 * Never hold on to the object returned by this function.
 * Call `getAgent()` at the time of invocation to ensure
 * that you never have a stale agent.
 */
export function getAgent() {
  return __globalAgent
}

export type SessionAccount = persisted.PersistedAccount

export type SessionState = {
  isInitialLoad: boolean
  isSwitchingAccounts: boolean
  accounts: SessionAccount[]
  currentAccount: SessionAccount | undefined
}
export type StateContext = SessionState & {
  hasSession: boolean
  isSandbox: boolean
}
export type ApiContext = {
  createAccount: (props: {
    service: string
    email: string
    password: string
    handle: string
    inviteCode?: string
  }) => Promise<void>
  login: (props: {
    service: string
    identifier: string
    password: string
  }) => Promise<void>
  /**
   * A full logout. Clears the `currentAccount` from session, AND removes
   * access tokens from all accounts, so that returning as any user will
   * require a full login.
   */
  logout: () => Promise<void>
  /**
   * A partial logout. Clears the `currentAccount` from session, but DOES NOT
   * clear access tokens from accounts, allowing the user to return to their
   * other accounts without logging in.
   *
   * Used when adding a new account, deleting an account.
   */
  clearCurrentAccount: () => void
  initSession: (account: SessionAccount) => Promise<void>
  resumeSession: (account?: SessionAccount) => Promise<void>
  removeAccount: (account: SessionAccount) => void
  selectAccount: (account: SessionAccount) => Promise<void>
  updateCurrentAccount: (
    account: Partial<
      Pick<SessionAccount, 'handle' | 'email' | 'emailConfirmed'>
    >,
  ) => void
}

const StateContext = React.createContext<StateContext>({
  isInitialLoad: true,
  isSwitchingAccounts: false,
  accounts: [],
  currentAccount: undefined,
  hasSession: false,
  isSandbox: false,
})

const ApiContext = React.createContext<ApiContext>({
  createAccount: async () => {},
  login: async () => {},
  logout: async () => {},
  initSession: async () => {},
  resumeSession: async () => {},
  removeAccount: () => {},
  selectAccount: async () => {},
  updateCurrentAccount: () => {},
  clearCurrentAccount: () => {},
})

function createPersistSessionHandler(
  account: SessionAccount,
  persistSessionCallback: (props: {
    expired: boolean
    refreshedAccount: SessionAccount
  }) => void,
): AtpPersistSessionHandler {
  return function persistSession(event, session) {
    const expired = event === 'expired' || event === 'create-failed'

    const refreshedAccount: SessionAccount = {
      service: account.service,
      did: session?.did || account.did,
      handle: session?.handle || account.handle,
      email: session?.email || account.email,
      emailConfirmed: session?.emailConfirmed || account.emailConfirmed,

      /*
       * Tokens are undefined if the session expires, or if creation fails for
       * any reason e.g. tokens are invalid, network error, etc.
       */
      refreshJwt: session?.refreshJwt,
      accessJwt: session?.accessJwt,
    }

    logger.info(`session: persistSession`, {
      event,
      did: refreshedAccount.did,
      handle: refreshedAccount.handle,
    })

    if (expired) {
      emitSessionDropped()
    }

    /*
     * If the session expired, or it was successfully created/updated, we want
     * to update/persist the data.
     *
     * If the session creation failed, it could be a network error, or it could
     * be more serious like an invalid token(s). We can't differentiate, so in
     * order to allow the user to get a fresh token (if they need it), we need
     * to persist this data and wipe their tokens, effectively logging them
     * out.
     */
    persistSessionCallback({
      expired,
      refreshedAccount,
    })
  }
}

export function Provider({children}: React.PropsWithChildren<{}>) {
  const queryClient = useQueryClient()
  const isDirty = React.useRef(false)
  const [state, setState] = React.useState<SessionState>({
    isInitialLoad: true,
    isSwitchingAccounts: false,
    accounts: persisted.get('session').accounts,
    currentAccount: undefined, // assume logged out to start
  })

  const setStateAndPersist = React.useCallback(
    (fn: (prev: SessionState) => SessionState) => {
      isDirty.current = true
      setState(fn)
    },
    [setState],
  )

  const upsertAccount = React.useCallback(
    (account: SessionAccount, expired = false) => {
      setStateAndPersist(s => {
        return {
          ...s,
          currentAccount: expired ? undefined : account,
          accounts: [account, ...s.accounts.filter(a => a.did !== account.did)],
        }
      })
    },
    [setStateAndPersist],
  )

  const createAccount = React.useCallback<ApiContext['createAccount']>(
    async ({service, email, password, handle, inviteCode}: any) => {
      logger.debug(
        `session: creating account`,
        {
          service,
          handle,
        },
        logger.DebugContext.session,
      )

      const agent = new BskyAgent({service})

      await agent.createAccount({
        handle,
        password,
        email,
        inviteCode,
      })

      if (!agent.session) {
        throw new Error(`session: createAccount failed to establish a session`)
      }

      const account: SessionAccount = {
        service: agent.service.toString(),
        did: agent.session.did,
        handle: agent.session.handle,
        email: agent.session.email!, // TODO this is always defined?
        emailConfirmed: false,
        refreshJwt: agent.session.refreshJwt,
        accessJwt: agent.session.accessJwt,
      }

      agent.setPersistSessionHandler(
        createPersistSessionHandler(account, ({expired, refreshedAccount}) => {
          upsertAccount(refreshedAccount, expired)
        }),
      )

      __globalAgent = agent
      queryClient.clear()
      upsertAccount(account)

      logger.debug(
        `session: created account`,
        {
          service,
          handle,
        },
        logger.DebugContext.session,
      )
    },
    [upsertAccount, queryClient],
  )

  const login = React.useCallback<ApiContext['login']>(
    async ({service, identifier, password}) => {
      logger.debug(
        `session: login`,
        {
          service,
          identifier,
        },
        logger.DebugContext.session,
      )

      const agent = new BskyAgent({service})

      await agent.login({identifier, password})

      if (!agent.session) {
        throw new Error(`session: login failed to establish a session`)
      }

      const account: SessionAccount = {
        service: agent.service.toString(),
        did: agent.session.did,
        handle: agent.session.handle,
        email: agent.session.email,
        emailConfirmed: agent.session.emailConfirmed || false,
        refreshJwt: agent.session.refreshJwt,
        accessJwt: agent.session.accessJwt,
      }

      agent.setPersistSessionHandler(
        createPersistSessionHandler(account, ({expired, refreshedAccount}) => {
          upsertAccount(refreshedAccount, expired)
        }),
      )

      __globalAgent = agent
      queryClient.clear()
      upsertAccount(account)

      logger.debug(
        `session: logged in`,
        {
          service,
          identifier,
        },
        logger.DebugContext.session,
      )

      track('Sign In', {resumedSession: false})
    },
    [upsertAccount, queryClient],
  )

  const clearCurrentAccount = React.useCallback(() => {
    logger.debug(
      `session: clear current account`,
      {},
      logger.DebugContext.session,
    )
    __globalAgent = PUBLIC_BSKY_AGENT
    queryClient.clear()
    setStateAndPersist(s => ({
      ...s,
      currentAccount: undefined,
    }))
  }, [setStateAndPersist, queryClient])

  const logout = React.useCallback<ApiContext['logout']>(async () => {
    clearCurrentAccount()
    logger.debug(`session: logout`, {}, logger.DebugContext.session)
    setStateAndPersist(s => {
      return {
        ...s,
        accounts: s.accounts.map(a => ({
          ...a,
          refreshJwt: undefined,
          accessJwt: undefined,
        })),
      }
    })
  }, [clearCurrentAccount, setStateAndPersist])

  const initSession = React.useCallback<ApiContext['initSession']>(
    async account => {
      logger.debug(
        `session: initSession`,
        {
          did: account.did,
          handle: account.handle,
        },
        logger.DebugContext.session,
      )

      const agent = new BskyAgent({
        service: account.service,
        persistSession: createPersistSessionHandler(
          account,
          ({expired, refreshedAccount}) => {
            upsertAccount(refreshedAccount, expired)
          },
        ),
      })

      let canReusePrevSession = false
      try {
        if (account.accessJwt) {
          const decoded = jwtDecode(account.accessJwt)
          if (decoded.exp) {
            const didExpire = Date.now() >= decoded.exp * 1000
            if (!didExpire) {
              canReusePrevSession = true
            }
          }
        }
      } catch (e) {
        logger.error(`session: could not decode jwt`)
      }

      const prevSession = {
        accessJwt: account.accessJwt || '',
        refreshJwt: account.refreshJwt || '',
        did: account.did,
        handle: account.handle,
      }

      if (canReusePrevSession) {
        agent.session = prevSession
        __globalAgent = agent
        queryClient.clear()
        upsertAccount(account)

        // Intentionally not awaited to unblock the UI:
        resumeSessionWithFreshAccount()
          .then(freshAccount => {
            if (JSON.stringify(account) !== JSON.stringify(freshAccount)) {
              upsertAccount(freshAccount)
            }
          })
          .catch(e => {
            /*
             * Note: `agent.persistSession` is also called when this fails, and
             * we handle that failure via `createPersistSessionHandler`
             */
            logger.info(`session: resumeSessionWithFreshAccount failed`, {
              error: e,
            })

            __globalAgent = PUBLIC_BSKY_AGENT
          })
      } else {
        try {
          const freshAccount = await resumeSessionWithFreshAccount()
          __globalAgent = agent
          queryClient.clear()
          upsertAccount(freshAccount)
        } catch (e) {
          /*
           * Note: `agent.persistSession` is also called when this fails, and
           * we handle that failure via `createPersistSessionHandler`
           */
          logger.info(`session: resumeSessionWithFreshAccount failed`, {
            error: e,
          })

          __globalAgent = PUBLIC_BSKY_AGENT
        }
      }

      async function resumeSessionWithFreshAccount(): Promise<SessionAccount> {
        await networkRetry(1, () => agent.resumeSession(prevSession))

        /*
         * If `agent.resumeSession` fails above, it'll throw. This is just to
         * make TypeScript happy.
         */
        if (!agent.session) {
          throw new Error(`session: initSession failed to establish a session`)
        }

        // ensure changes in handle/email etc are captured on reload
        return {
          service: agent.service.toString(),
          did: agent.session.did,
          handle: agent.session.handle,
          email: agent.session.email,
          emailConfirmed: agent.session.emailConfirmed || false,
          refreshJwt: agent.session.refreshJwt,
          accessJwt: agent.session.accessJwt,
        }
      }
    },
    [upsertAccount, queryClient],
  )

  const resumeSession = React.useCallback<ApiContext['resumeSession']>(
    async account => {
      try {
        if (account) {
          await initSession(account)
        }
      } catch (e) {
        logger.error(`session: resumeSession failed`, {error: e})
      } finally {
        setState(s => ({
          ...s,
          isInitialLoad: false,
        }))
      }
    },
    [initSession],
  )

  const removeAccount = React.useCallback<ApiContext['removeAccount']>(
    account => {
      setStateAndPersist(s => {
        return {
          ...s,
          accounts: s.accounts.filter(a => a.did !== account.did),
        }
      })
    },
    [setStateAndPersist],
  )

  const updateCurrentAccount = React.useCallback<
    ApiContext['updateCurrentAccount']
  >(
    account => {
      setStateAndPersist(s => {
        const currentAccount = s.currentAccount

        // ignore, should never happen
        if (!currentAccount) return s

        const updatedAccount = {
          ...currentAccount,
          handle: account.handle || currentAccount.handle,
          email: account.email || currentAccount.email,
          emailConfirmed:
            account.emailConfirmed !== undefined
              ? account.emailConfirmed
              : currentAccount.emailConfirmed,
        }

        return {
          ...s,
          currentAccount: updatedAccount,
          accounts: [
            updatedAccount,
            ...s.accounts.filter(a => a.did !== currentAccount.did),
          ],
        }
      })
    },
    [setStateAndPersist],
  )

  const selectAccount = React.useCallback<ApiContext['selectAccount']>(
    async account => {
      setState(s => ({...s, isSwitchingAccounts: true}))
      try {
        await initSession(account)
        setState(s => ({...s, isSwitchingAccounts: false}))
      } catch (e) {
        // reset this in case of error
        setState(s => ({...s, isSwitchingAccounts: false}))
        // but other listeners need a throw
        throw e
      }
    },
    [setState, initSession],
  )

  React.useEffect(() => {
    if (isDirty.current) {
      isDirty.current = false
      persisted.write('session', {
        accounts: state.accounts,
        currentAccount: state.currentAccount,
      })
    }
  }, [state])

  React.useEffect(() => {
    return persisted.onUpdate(() => {
      const session = persisted.get('session')

      logger.debug(`session: onUpdate`, {}, logger.DebugContext.session)

      if (session.currentAccount) {
        if (session.currentAccount?.did !== state.currentAccount?.did) {
          logger.debug(
            `session: switching account`,
            {
              from: {
                did: state.currentAccount?.did,
                handle: state.currentAccount?.handle,
              },
              to: {
                did: session.currentAccount.did,
                handle: session.currentAccount.handle,
              },
            },
            logger.DebugContext.session,
          )

          initSession(session.currentAccount)
        }
      } else if (!session.currentAccount && state.currentAccount) {
        logger.debug(
          `session: logging out`,
          {
            did: state.currentAccount?.did,
            handle: state.currentAccount?.handle,
          },
          logger.DebugContext.session,
        )

        clearCurrentAccount()
      }
    })
  }, [state, clearCurrentAccount, initSession])

  const stateContext = React.useMemo(
    () => ({
      ...state,
      hasSession: !!state.currentAccount,
      isSandbox: state.currentAccount
        ? !IS_PROD(state.currentAccount?.service)
        : false,
    }),
    [state],
  )

  const api = React.useMemo(
    () => ({
      createAccount,
      login,
      logout,
      initSession,
      resumeSession,
      removeAccount,
      selectAccount,
      updateCurrentAccount,
      clearCurrentAccount,
    }),
    [
      createAccount,
      login,
      logout,
      initSession,
      resumeSession,
      removeAccount,
      selectAccount,
      updateCurrentAccount,
      clearCurrentAccount,
    ],
  )

  return (
    <StateContext.Provider value={stateContext}>
      <ApiContext.Provider value={api}>{children}</ApiContext.Provider>
    </StateContext.Provider>
  )
}

export function useSession() {
  return React.useContext(StateContext)
}

export function useSessionApi() {
  return React.useContext(ApiContext)
}

export function useRequireAuth() {
  const {hasSession} = useSession()
  const {setShowLoggedOut} = useLoggedOutViewControls()
  const closeAll = useCloseAllActiveElements()

  return React.useCallback(
    (fn: () => void) => {
      if (hasSession) {
        fn()
      } else {
        closeAll()
        setShowLoggedOut(true)
      }
    },
    [hasSession, setShowLoggedOut, closeAll],
  )
}