#!/usr/bin/env python2
# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
from __future__ import with_statement

__license__   = 'GPL v3'
__copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
__docformat__ = 'restructuredtext en'


'''
Input plugin for HTML or OPF ebooks.
'''

import os, re, sys,  errno as gerrno
from urlparse import urlparse, urlunparse

from calibre.ebooks.oeb.base import urlunquote
from calibre.ebooks.chardet import detect_xml_encoding
from calibre.constants import iswindows
from calibre import unicode_path, as_unicode, replace_entities


class Link(object):

    '''
    Represents a link in a HTML file.
    '''

    @classmethod
    def url_to_local_path(cls, url, base):
        path = url.path
        isabs = False
        if iswindows and path.startswith('/'):
            path = path[1:]
            isabs = True
        path = urlunparse(('', '', path, url.params, url.query, ''))
        path = urlunquote(path)
        if isabs or os.path.isabs(path):
            return path
        return os.path.abspath(os.path.join(base, path))

    def __init__(self, url, base):
        '''
        :param url:  The url this link points to. Must be an unquoted unicode string.
        :param base: The base directory that relative URLs are with respect to.
                     Must be a unicode string.
        '''
        assert isinstance(url, unicode) and isinstance(base, unicode)
        self.url         = url
        self.parsed_url  = urlparse(self.url)
        self.is_local    = self.parsed_url.scheme in ('', 'file')
        self.is_internal = self.is_local and not bool(self.parsed_url.path)
        self.path        = None
        self.fragment    = urlunquote(self.parsed_url.fragment)
        if self.is_local and not self.is_internal:
            self.path = self.url_to_local_path(self.parsed_url, base)

    def __hash__(self):
        if self.path is None:
            return hash(self.url)
        return hash(self.path)

    def __eq__(self, other):
        return self.path == getattr(other, 'path', other)

    def __str__(self):
        return u'Link: %s --> %s'%(self.url, self.path)


class IgnoreFile(Exception):

    def __init__(self, msg, errno):
        Exception.__init__(self, msg)
        self.doesnt_exist = errno == gerrno.ENOENT
        self.errno = errno


class HTMLFile(object):

    '''
    Contains basic information about an HTML file. This
    includes a list of links to other files as well as
    the encoding of each file. Also tries to detect if the file is not a HTML
    file in which case :member:`is_binary` is set to True.

    The encoding of the file is available as :member:`encoding`.
    '''

    HTML_PAT  = re.compile(r'<\s*html', re.IGNORECASE)
    TITLE_PAT = re.compile('<title>([^<>]+)</title>', re.IGNORECASE)
    LINK_PAT  = re.compile(
    r'<\s*a\s+.*?href\s*=\s*(?:(?:"(?P<url1>[^"]+)")|(?:\'(?P<url2>[^\']+)\')|(?P<url3>[^\s>]+))',
    re.DOTALL|re.IGNORECASE)

    def __init__(self, path_to_html_file, level, encoding, verbose, referrer=None):
        '''
        :param level: The level of this file. Should be 0 for the root file.
        :param encoding: Use `encoding` to decode HTML.
        :param referrer: The :class:`HTMLFile` that first refers to this file.
        '''
        self.path     = unicode_path(path_to_html_file, abs=True)
        self.title    = os.path.splitext(os.path.basename(self.path))[0]
        self.base     = os.path.dirname(self.path)
        self.level    = level
        self.referrer = referrer
        self.links    = []

        try:
            with open(self.path, 'rb') as f:
                src = header = f.read(4096)
                encoding = detect_xml_encoding(src)[1]
                if encoding:
                    try:
                        header = header.decode(encoding)
                    except ValueError:
                        pass
                self.is_binary = level > 0 and not bool(self.HTML_PAT.search(header))
                if not self.is_binary:
                    src += f.read()
        except IOError as err:
            msg = 'Could not read from file: %s with error: %s'%(self.path, as_unicode(err))
            if level == 0:
                raise IOError(msg)
            raise IgnoreFile(msg, err.errno)

        if not src:
            if level == 0:
                raise ValueError('The file %s is empty'%self.path)
            self.is_binary = True

        if not self.is_binary:
            if not encoding:
                encoding = detect_xml_encoding(src[:4096], verbose=verbose)[1]
                self.encoding = encoding
            else:
                self.encoding = encoding

            src = src.decode(encoding, 'replace')
            match = self.TITLE_PAT.search(src)
            self.title = match.group(1) if match is not None else self.title
            self.find_links(src)

    def __eq__(self, other):
        return self.path == getattr(other, 'path', other)

    def __str__(self):
        return u'HTMLFile:%d:%s:%s'%(self.level, 'b' if self.is_binary else 'a', self.path)

    def __repr__(self):
        return str(self)

    def find_links(self, src):
        for match in self.LINK_PAT.finditer(src):
            url = None
            for i in ('url1', 'url2', 'url3'):
                url = match.group(i)
                if url:
                    break
            url = replace_entities(url)
            try:
                link = self.resolve(url)
            except ValueError:
                # Unparseable URL, ignore
                continue
            if link not in self.links:
                self.links.append(link)

    def resolve(self, url):
        return Link(url, self.base)


def depth_first(root, flat, visited=set([])):
    yield root
    visited.add(root)
    for link in root.links:
        if link.path is not None and link not in visited:
            try:
                index = flat.index(link)
            except ValueError:  # Can happen if max_levels is used
                continue
            hf = flat[index]
            if hf not in visited:
                yield hf
                visited.add(hf)
                for hf in depth_first(hf, flat, visited):
                    if hf not in visited:
                        yield hf
                        visited.add(hf)


def traverse(path_to_html_file, max_levels=sys.maxint, verbose=0, encoding=None):
    '''
    Recursively traverse all links in the HTML file.

    :param max_levels: Maximum levels of recursion. Must be non-negative. 0
                       implies that no links in the root HTML file are followed.
    :param encoding:   Specify character encoding of HTML files. If `None` it is
                       auto-detected.
    :return:           A pair of lists (breadth_first, depth_first). Each list contains
                       :class:`HTMLFile` objects.
    '''
    assert max_levels >= 0
    level = 0
    flat =  [HTMLFile(path_to_html_file, level, encoding, verbose)]
    next_level = list(flat)
    while level < max_levels and len(next_level) > 0:
        level += 1
        nl = []
        for hf in next_level:
            rejects = []
            for link in hf.links:
                if link.path is None or link.path in flat:
                    continue
                try:
                    nf = HTMLFile(link.path, level, encoding, verbose, referrer=hf)
                    if nf.is_binary:
                        raise IgnoreFile('%s is a binary file'%nf.path, -1)
                    nl.append(nf)
                    flat.append(nf)
                except IgnoreFile as err:
                    rejects.append(link)
                    if not err.doesnt_exist or verbose > 1:
                        print repr(err)
            for link in rejects:
                hf.links.remove(link)

        next_level = list(nl)
    orec = sys.getrecursionlimit()
    sys.setrecursionlimit(500000)
    try:
        return flat, list(depth_first(flat[0], flat))
    finally:
        sys.setrecursionlimit(orec)


def get_filelist(htmlfile, dir, opts, log):
    '''
    Build list of files referenced by html file or try to detect and use an
    OPF file instead.
    '''
    log.info('Building file list...')
    filelist = traverse(htmlfile, max_levels=int(opts.max_levels),
                        verbose=opts.verbose,
                        encoding=opts.input_encoding)[0 if opts.breadth_first else 1]
    if opts.verbose:
        log.debug('\tFound files...')
        for f in filelist:
            log.debug('\t\t', f)
    return filelist



