# vim:fileencoding=utf-8
# License: GPL v3 Copyright: 2015, Kovid Goyal <kovid at kovidgoyal.net>

def storage_available(which):
    which = which or 'localStorage'
    try:
        storage = window[which]
        x = '__storage__test__'
        storage.setItem(x, x)
        storage.removeItem(x)
        return True
    except:
        return False

session_storage = None

class FakeStorage:

    def __init__(self):
        self.data = {}

    def getItem(self, key):
        return self.data[key]

    def setItem(self, key, value):
        if type(value) != 'string':
            value = JSON.stringify(value)
        self.data[key] = value

    def clear(self):
        self.data = {}

def get_session_storage():
    nonlocal session_storage
    if session_storage is None:
        if storage_available('localStorage'):
            session_storage = window.localStorage
        elif storage_available('sessionStorage'):
            session_storage = window.sessionStorage
            console.error('localStorage not available using sessionStorage instead')
        else:
            session_storage = FakeStorage()
            console.error('sessionStorage and localStorage not available using a temp cache instead')
    return session_storage

class SessionData:

    def __init__(self):
        self.storage = get_session_storage()
        self.overflow_storage = {}
        self.has_overflow = False

    def get(self, key, defval):
        if defval is undefined:
            defval = None
        if self.has_overflow:
            ans = self.overflow_storage[key]
            if ans is undefined:
                ans = self.storage.getItem(key)
        else:
            ans = self.storage.getItem(key)
        if ans is undefined:
            return defval
        return JSON.parse(ans)

    def set(self, key, value):
        value = JSON.stringify(value)
        try:
            self.storage.setItem(key, value)
            v'delete self.overflow_storage[key]'
            return True
        except:
            self.overflow_storage[key] = value
            self.has_overflow = True
            console.error('session storage has overflowed, using a temp cache instead')
        return False

    def clear(self):
        self.storage.clear()
        self.overflow_storage = {}
        self.has_overflow = False

class UserSessionData(SessionData):

    def __init__(self, username):
        self.prefix = (username or '') + ':'
        self.has_user = bool(username)
        self.username = username
        SessionData.__init__(self)

    def get(self, key, defval):
        return SessionData.get(self, (self.prefix + key), defval)

    def set(self, key, value):
        return SessionData.set(self, (self.prefix + key), value)