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

from gettext import gettext as _

def encode_query(query):
    if not query:
        return ''
    keys = Object.keys(query)
    has_query = False
    path = ''
    if keys.length:
        for k in keys:
            val = query[k]
            if val is undefined or val is None:
                continue
            path += ('&' if has_query else '?') + encodeURIComponent(k) + '=' + encodeURIComponent(val.toString())
            has_query = True
    return path

def ajax(path, on_complete, on_progress=None, bypass_cache=True, method='GET', query=None, timeout=30*1000, ok_code=200, progress_totals_needed=True):
    # Run an AJAX request. on_complete must be a function that accepts three
    # arguments: end_type, xhr, ev where end_type is one of 'abort', 'error',
    # 'load', 'timeout'. In case end_type is anything other than 'load' you can
    # get a descriptive error message via `xhr.error_html`.  on_progress, if
    # provided must be a function accepting three arguments: loaded, total, xhr
    # where loaded is the number of bytes received, total is the total size.
    #
    # Returns the xhr object, call xhr.send() to start the request.
    query = query or {}
    xhr = XMLHttpRequest()
    eq = encode_query(query)
    has_query = eq.length > 0
    path += eq
    if bypass_cache:
        path += ('&' if has_query else '?') + Date().getTime()

    xhr.request_path = path
    xhr.error_html = ''

    def set_error(event):
        if event is 'timeout':
            xhr.error_html = str.format(_('Failed to communicate with "{}", timed out after: {} seconds'), xhr.request_path, timeout/1000)
        elif event is 'abort':
            xhr.error_html = str.format(_('Failed to communicate with "{}", aborted'), xhr.request_path)
        else:
            rtext = xhr.responseText or ''
            xhr.error_html = str.format(_('Failed to communicate with "{}", with status: [{}] {}<br>{}'), xhr.request_path, xhr.status, xhr.statusText, rtext[:200])

    def progress_callback(ev):
        if ev.lengthComputable:
            on_progress(ev.loaded, ev.total, xhr)
        elif ev.loaded:
            if not progress_totals_needed:
                on_progress(ev.loaded, undefined, xhr)
                return
            ul = xhr.getResponseHeader('Calibre-Uncompressed-Length')
            if ul:
                try:
                    ul = int(ul)
                except Exception:
                    return
                on_progress(ev.loaded, ul, xhr)

    def complete_callback(end_type, ev):
        if xhr.status is not ok_code and end_type is 'load':
            end_type = 'error'
        if end_type is not 'load':
            set_error(end_type)
        on_complete(end_type, xhr, ev)

    if on_progress:
        xhr.addEventListener('progress', progress_callback)
    xhr.addEventListener('abort', def(ev): complete_callback('abort', ev);)
    xhr.addEventListener('error', def(ev): complete_callback('error', ev);)
    xhr.addEventListener('load', def(ev): complete_callback('load', ev);)
    xhr.addEventListener('timeout', def(ev): complete_callback('timeout', ev);)
    xhr.open(method, path)
    xhr.timeout = timeout  # IE requires timeout to be set after open
    return xhr

def ajax_send(path, data, on_complete, on_progress=None, query=None, timeout=30*1000, ok_code=200):
    # Unfortunately, browsers do not allow sending of data with HTTP GET, except
    # as query parameters, so we have to use POST
    xhr = ajax(path, on_complete, on_progress, False, 'POST', query, timeout, ok_code)
    xhr.setRequestHeader('Content-Type', 'application/json;charset=UTF-8')
    xhr.send(JSON.stringify(data))
    return xhr

# TODO: Implement AJAX based switch user by:
# 1) POST to a logout URL with an incorrect username and password
# 2) Have the server accept that incorrect username/password
# 3) Navigate to / which should cause the browser to re-prompt for username and password
# (only problem is login dialog will likely pre-show the wrong username) To workaround that,
# You can consider using a dedicated ajax based login form, see http://www.peej.co.uk/articles/http-auth-with-html-forms.html)