"""
    sphinx.builders.linkcheck
    ~~~~~~~~~~~~~~~~~~~~~~~~~

    The CheckExternalLinksBuilder class.

    :copyright: Copyright 2007-2019 by the Sphinx team, see AUTHORS.
    :license: BSD, see LICENSE for details.
"""

import queue
import re
import socket
import threading
from html.parser import HTMLParser
from os import path
from urllib.parse import unquote

from docutils import nodes
from requests.exceptions import HTTPError

from sphinx.builders import Builder
from sphinx.locale import __
from sphinx.util import encode_uri, requests, logging
from sphinx.util.console import (  # type: ignore
    purple, red, darkgreen, darkgray, darkred, turquoise
)
from sphinx.util.nodes import get_node_line
from sphinx.util.requests import is_ssl_error

if False:
    # For type annotation
    from typing import Any, Dict, List, Set, Tuple  # NOQA
    from sphinx.application import Sphinx  # NOQA
    from sphinx.util.requests.requests import Response  # NOQA


logger = logging.getLogger(__name__)


class AnchorCheckParser(HTMLParser):
    """Specialized HTML parser that looks for a specific anchor."""

    def __init__(self, search_anchor):
        # type: (str) -> None
        super().__init__()

        self.search_anchor = search_anchor
        self.found = False

    def handle_starttag(self, tag, attrs):
        # type: (Any, Any) -> None
        for key, value in attrs:
            if key in ('id', 'name') and value == self.search_anchor:
                self.found = True
                break


def check_anchor(response, anchor):
    # type: (Response, str) -> bool
    """Reads HTML data from a response object `response` searching for `anchor`.
    Returns True if anchor was found, False otherwise.
    """
    parser = AnchorCheckParser(anchor)
    # Read file in chunks. If we find a matching anchor, we break
    # the loop early in hopes not to have to download the whole thing.
    for chunk in response.iter_content(chunk_size=4096, decode_unicode=True):
        parser.feed(chunk)
        if parser.found:
            break
    parser.close()
    return parser.found


class CheckExternalLinksBuilder(Builder):
    """
    Checks for broken external links.
    """
    name = 'linkcheck'
    epilog = __('Look for any errors in the above output or in '
                '%(outdir)s/output.txt')

    def init(self):
        # type: () -> None
        self.to_ignore = [re.compile(x) for x in self.app.config.linkcheck_ignore]
        self.anchors_ignore = [re.compile(x)
                               for x in self.app.config.linkcheck_anchors_ignore]
        self.good = set()       # type: Set[str]
        self.broken = {}        # type: Dict[str, str]
        self.redirected = {}    # type: Dict[str, Tuple[str, int]]
        # set a timeout for non-responding servers
        socket.setdefaulttimeout(5.0)
        # create output file
        open(path.join(self.outdir, 'output.txt'), 'w').close()

        # create queues and worker threads
        self.wqueue = queue.Queue()  # type: queue.Queue
        self.rqueue = queue.Queue()  # type: queue.Queue
        self.workers = []  # type: List[threading.Thread]
        for i in range(self.app.config.linkcheck_workers):
            thread = threading.Thread(target=self.check_thread)
            thread.setDaemon(True)
            thread.start()
            self.workers.append(thread)

    def check_thread(self):
        # type: () -> None
        kwargs = {
            'allow_redirects': True,
            'headers': {
                'Accept': 'text/html,application/xhtml+xml;q=0.9,*/*;q=0.8',
                'User-Agent': requests.useragent_header[0][1],
            },
        }
        if self.app.config.linkcheck_timeout:
            kwargs['timeout'] = self.app.config.linkcheck_timeout

        def check_uri():
            # type: () -> Tuple[str, str, int]
            # split off anchor
            if '#' in uri:
                req_url, anchor = uri.split('#', 1)
                for rex in self.anchors_ignore:
                    if rex.match(anchor):
                        anchor = None
                        break
            else:
                req_url = uri
                anchor = None

            # handle non-ASCII URIs
            try:
                req_url.encode('ascii')
            except UnicodeError:
                req_url = encode_uri(req_url)

            try:
                if anchor and self.app.config.linkcheck_anchors:
                    # Read the whole document and see if #anchor exists
                    response = requests.get(req_url, stream=True, config=self.app.config,
                                            **kwargs)
                    found = check_anchor(response, unquote(anchor))

                    if not found:
                        raise Exception(__("Anchor '%s' not found") % anchor)
                else:
                    try:
                        # try a HEAD request first, which should be easier on
                        # the server and the network
                        response = requests.head(req_url, config=self.app.config, **kwargs)
                        response.raise_for_status()
                    except HTTPError:
                        # retry with GET request if that fails, some servers
                        # don't like HEAD requests.
                        response = requests.get(req_url, stream=True, config=self.app.config,
                                                **kwargs)
                        response.raise_for_status()
            except HTTPError as err:
                if err.response.status_code == 401:
                    # We'll take "Unauthorized" as working.
                    return 'working', ' - unauthorized', 0
                else:
                    return 'broken', str(err), 0
            except Exception as err:
                if is_ssl_error(err):
                    return 'ignored', str(err), 0
                else:
                    return 'broken', str(err), 0
            if response.url.rstrip('/') == req_url.rstrip('/'):
                return 'working', '', 0
            else:
                new_url = response.url
                if anchor:
                    new_url += '#' + anchor
                # history contains any redirects, get last
                if response.history:
                    code = response.history[-1].status_code
                    return 'redirected', new_url, code
                else:
                    return 'redirected', new_url, 0

        def check():
            # type: () -> Tuple[str, str, int]
            # check for various conditions without bothering the network
            if len(uri) == 0 or uri.startswith(('#', 'mailto:', 'ftp:')):
                return 'unchecked', '', 0
            elif not uri.startswith(('http:', 'https:')):
                return 'local', '', 0
            elif uri in self.good:
                return 'working', 'old', 0
            elif uri in self.broken:
                return 'broken', self.broken[uri], 0
            elif uri in self.redirected:
                return 'redirected', self.redirected[uri][0], self.redirected[uri][1]
            for rex in self.to_ignore:
                if rex.match(uri):
                    return 'ignored', '', 0

            # need to actually check the URI
            for _ in range(self.app.config.linkcheck_retries):
                status, info, code = check_uri()
                if status != "broken":
                    break

            if status == "working":
                self.good.add(uri)
            elif status == "broken":
                self.broken[uri] = info
            elif status == "redirected":
                self.redirected[uri] = (info, code)

            return (status, info, code)

        while True:
            uri, docname, lineno = self.wqueue.get()
            if uri is None:
                break
            status, info, code = check()
            self.rqueue.put((uri, docname, lineno, status, info, code))

    def process_result(self, result):
        # type: (Tuple[str, str, int, str, str, int]) -> None
        uri, docname, lineno, status, info, code = result
        if status == 'unchecked':
            return
        if status == 'working' and info == 'old':
            return
        if lineno:
            logger.info('(line %4d) ', lineno, nonl=True)
        if status == 'ignored':
            if info:
                logger.info(darkgray('-ignored- ') + uri + ': ' + info)
            else:
                logger.info(darkgray('-ignored- ') + uri)
        elif status == 'local':
            logger.info(darkgray('-local-   ') + uri)
            self.write_entry('local', docname, lineno, uri)
        elif status == 'working':
            logger.info(darkgreen('ok        ') + uri + info)
        elif status == 'broken':
            self.write_entry('broken', docname, lineno, uri + ': ' + info)
            if self.app.quiet or self.app.warningiserror:
                logger.warning(__('broken link: %s (%s)'), uri, info,
                               location=(self.env.doc2path(docname), lineno))
            else:
                logger.info(red('broken    ') + uri + red(' - ' + info))
        elif status == 'redirected':
            text, color = {
                301: ('permanently', darkred),
                302: ('with Found', purple),
                303: ('with See Other', purple),
                307: ('temporarily', turquoise),
                0:   ('with unknown code', purple),
            }[code]
            self.write_entry('redirected ' + text, docname, lineno,
                             uri + ' to ' + info)
            logger.info(color('redirect  ') + uri + color(' - ' + text + ' to ' + info))

    def get_target_uri(self, docname, typ=None):
        # type: (str, str) -> str
        return ''

    def get_outdated_docs(self):
        # type: () -> Set[str]
        return self.env.found_docs

    def prepare_writing(self, docnames):
        # type: (Set[str]) -> None
        return

    def write_doc(self, docname, doctree):
        # type: (str, nodes.Node) -> None
        logger.info('')
        n = 0

        # reference nodes
        for refnode in doctree.traverse(nodes.reference):
            if 'refuri' not in refnode:
                continue
            uri = refnode['refuri']
            lineno = get_node_line(refnode)
            self.wqueue.put((uri, docname, lineno), False)
            n += 1

        # image nodes
        for imgnode in doctree.traverse(nodes.image):
            uri = imgnode['candidates'].get('?')
            if uri and '://' in uri:
                lineno = get_node_line(imgnode)
                self.wqueue.put((uri, docname, lineno), False)
                n += 1

        done = 0
        while done < n:
            self.process_result(self.rqueue.get())
            done += 1

        if self.broken:
            self.app.statuscode = 1

    def write_entry(self, what, docname, line, uri):
        # type: (str, str, int, str) -> None
        with open(path.join(self.outdir, 'output.txt'), 'a', encoding='utf-8') as output:
            output.write("%s:%s: [%s] %s\n" % (self.env.doc2path(docname, None),
                                               line, what, uri))

    def finish(self):
        # type: () -> None
        for worker in self.workers:
            self.wqueue.put((None, None, None), False)


def setup(app):
    # type: (Sphinx) -> Dict[str, Any]
    app.add_builder(CheckExternalLinksBuilder)

    app.add_config_value('linkcheck_ignore', [], None)
    app.add_config_value('linkcheck_retries', 1, None)
    app.add_config_value('linkcheck_timeout', None, None, [int])
    app.add_config_value('linkcheck_workers', 5, None)
    app.add_config_value('linkcheck_anchors', True, None)
    # Anchors starting with ! are ignored since they are
    # commonly used for dynamic pages
    app.add_config_value('linkcheck_anchors_ignore', ["^!"], None)

    return {
        'version': 'builtin',
        'parallel_read_safe': True,
        'parallel_write_safe': True,
    }
