'''
CSS flattening transform.
'''


__license__   = 'GPL v3'
__copyright__ = '2008, Marshall T. Vandegrift <llasram@gmail.com>'

import math
import numbers
import operator
import re
from collections import defaultdict
from xml.dom import SyntaxErr

import css_parser
from css_parser.css import Property
from lxml import etree

from calibre import guess_type
from calibre.ebooks import unit_convert
from calibre.ebooks.oeb.base import CSS_MIME, OEB_STYLES, SVG, SVG_NS, XHTML, XHTML_NS, XPath, barename, css_text, namespace
from calibre.ebooks.oeb.stylizer import Stylizer
from calibre.utils.filenames import ascii_filename, ascii_text
from calibre.utils.icu import numeric_sort_key
from polyglot.builtins import iteritems, string_or_bytes

COLLAPSE = re.compile(r'[ \t\r\n\v]+')
STRIPNUM = re.compile(r'[-0-9]+$')


def asfloat(value, default):
    if not isinstance(value, numbers.Number):
        value = default
    return float(value)


class KeyMapper:

    def __init__(self, sbase, dbase, dkey):
        self.sbase = float(sbase)
        self.dprop = [(self.relate(x, dbase), float(x)) for x in dkey]
        self.cache = {}

    @staticmethod
    def relate(size, base):
        if size == 0:
            return base
        size = float(size)
        base = float(base)
        if abs(size - base) < 0.1:
            return 0
        sign = -1 if size < base else 1
        endp = 0 if size < base else 36
        diff = (abs(base - size) * 3) + ((36 - size) / 100)
        logb = abs(base - endp)
        if logb == 1.0:
            logb = 1.1
        try:
            result = sign * math.log(diff, logb)
        except ValueError:
            if diff < 0:
                # Size is both very large and close to base
                return 0
            if logb == 0:
                logb = 1e-6
            if diff == 0:
                diff = 1e-6
            result = sign * math.log(diff, logb)
        return result

    def __getitem__(self, ssize):
        ssize = asfloat(ssize, 0)
        if ssize in self.cache:
            return self.cache[ssize]
        dsize = self.map(ssize)
        self.cache[ssize] = dsize
        return dsize

    def map(self, ssize):
        sbase = self.sbase
        prop = self.relate(ssize, sbase)
        diff = [(abs(prop - p), s) for p, s in self.dprop]
        dsize = min(diff)[1]
        return dsize


class ScaleMapper:

    def __init__(self, sbase, dbase):
        self.dscale = float(dbase) / float(sbase)

    def __getitem__(self, ssize):
        ssize = asfloat(ssize, 0)
        dsize = ssize * self.dscale
        return dsize


class NullMapper:

    def __init__(self):
        pass

    def __getitem__(self, ssize):
        return ssize


def FontMapper(sbase=None, dbase=None, dkey=None):
    if sbase and dbase and dkey:
        return KeyMapper(sbase, dbase, dkey)
    elif sbase and dbase:
        return ScaleMapper(sbase, dbase)
    else:
        return NullMapper()


class EmbedFontsCSSRules:

    def __init__(self, body_font_family, rules):
        self.body_font_family, self.rules = body_font_family, rules
        self.href = None

    def __call__(self, oeb):
        if not self.body_font_family:
            return None
        if not self.href:
            iid, href = oeb.manifest.generate('page_styles', 'page_styles.css')
            rules = [css_text(x) for x in self.rules]
            rules = '\n\n'.join(rules)
            sheet = css_parser.parseString(rules, validate=False)
            self.href = oeb.manifest.add(iid, href, guess_type(href)[0],
                    data=sheet).href
        return self.href


class CSSFlattener:

    def __init__(self, fbase=None, fkey=None, lineh=None, unfloat=False,
                 untable=False, page_break_on_body=False, specializer=None,
                 transform_css_rules=()):
        self.fbase = fbase
        self.transform_css_rules = transform_css_rules
        if self.transform_css_rules:
            from calibre.ebooks.css_transform_rules import compile_rules
            self.transform_css_rules = compile_rules(self.transform_css_rules)
        self.fkey = fkey
        self.lineh = lineh
        self.unfloat = unfloat
        self.untable = untable
        self.specializer = specializer
        self.page_break_on_body = page_break_on_body

    @classmethod
    def config(cls, cfg):
        return cfg

    @classmethod
    def generate(cls, opts):
        return cls()

    def __call__(self, oeb, context):
        oeb.logger.info('Flattening CSS and remapping font sizes...')
        self.context = self.opts = context
        self.oeb = oeb
        self.items = list(self.oeb.spine)
        titlepage = self.oeb.guide.get('titlepage')
        if titlepage is not None:
            titlepage = titlepage.item
            if titlepage is not None and titlepage not in self.items:
                self.items.append(titlepage)
        epub3_nav = None
        if getattr(self.opts, 'epub3_nav_href', None):
            epub3_nav = self.oeb.manifest.hrefs.get(self.opts.epub3_nav_href)
            if epub3_nav is not None and epub3_nav not in self.items:
                self.items.append(epub3_nav)

        self.filter_css = frozenset()
        if self.opts.filter_css:
            try:
                self.filter_css = {x.strip().lower() for x in
                    self.opts.filter_css.split(',')}
            except:
                self.oeb.log.warning('Failed to parse filter_css, ignoring')
            else:
                from calibre.ebooks.oeb.normalize_css import normalize_filter_css
                self.filter_css = frozenset(normalize_filter_css(self.filter_css))
                self.oeb.log.debug('Filtering CSS properties: %s'%
                    ', '.join(self.filter_css))

        for item in oeb.manifest.values():
            # Make all links to resources absolute, as these sheets will be
            # consolidated into a single stylesheet at the root of the document
            if item.media_type in OEB_STYLES:
                css_parser.replaceUrls(item.data, item.abshref,
                        ignoreImportRules=True)

        self.body_font_family, self.embed_font_rules = self.get_embed_font_info(
                self.opts.embed_font_family)
        # Store for use in output plugins/transforms that generate content,
        # like the AZW3 output inline ToC.
        self.oeb.store_embed_font_rules = EmbedFontsCSSRules(self.body_font_family,
                self.embed_font_rules)
        self.stylize_spine()
        self.sbase = self.baseline_spine() if self.fbase else None
        self.fmap = FontMapper(self.sbase, self.fbase, self.fkey)
        self.flatten_spine()
        if epub3_nav is not None:
            self.opts.epub3_nav_parsed = epub3_nav.data

        self.store_page_margins()

    def store_page_margins(self):
        self.opts._stored_page_margins = {}
        for item, stylizer in iteritems(self.stylizers):
            margins = self.opts._stored_page_margins[item.href] = {}
            for prop, val in stylizer.page_rule.items():
                p, w = prop.partition('-')[::2]
                if p == 'margin':
                    margins[w] = unit_convert(
                            val, stylizer.profile.width_pts, stylizer.body_font_size,
                            stylizer.profile.dpi, body_font_size=stylizer.body_font_size)

    def get_embed_font_info(self, family, failure_critical=True):
        efi = []
        body_font_family = None
        if not family:
            return body_font_family, efi
        from calibre.utils.fonts.scanner import NoFonts, font_scanner
        from calibre.utils.fonts.utils import panose_to_css_generic_family
        try:
            faces = font_scanner.fonts_for_family(family)
        except NoFonts:
            msg = ('No embeddable fonts found for family: %r'%family)
            if failure_critical:
                raise ValueError(msg)
            self.oeb.log.warn(msg)
            return body_font_family, efi
        if not faces:
            msg = ('No embeddable fonts found for family: %r'%family)
            if failure_critical:
                raise ValueError(msg)
            self.oeb.log.warn(msg)
            return body_font_family, efi

        from calibre.ebooks.oeb.polish.utils import OEB_FONTS
        for i, font in enumerate(faces):
            ext = 'otf' if font['is_otf'] else 'ttf'
            font_data = font_scanner.get_font_data(font)
            for x in self.oeb.manifest:
                if x.media_type in OEB_FONTS:
                    matches = x.data == font_data
                    x.unload_data_from_memory()
                    if matches:
                        item = x
                        href = item.href
                        break
            else:
                fid, href = self.oeb.manifest.generate(id='font',
                    href='fonts/%s.%s'%(ascii_filename(font['full_name']).replace(' ', '-'), ext))
                item = self.oeb.manifest.add(fid, href,
                        guess_type('dummy.'+ext)[0],
                        data=font_data)
                item.unload_data_from_memory()

            cfont = {
                'font-family': '"%s"'%font['font-family'],
                'src': 'url(%s)'%item.href,
            }

            if i == 0:
                generic_family = panose_to_css_generic_family(font['panose'])
                body_font_family = "'%s',%s"%(font['font-family'], generic_family)
                self.oeb.log('Embedding font: %s'%font['font-family'])
            for k in ('font-weight', 'font-style', 'font-stretch'):
                if font[k] != 'normal':
                    cfont[k] = font[k]
            rule = '@font-face { %s }'%('; '.join('%s:%s'%(k, v) for k, v in
                iteritems(cfont)))
            rule = css_parser.parseString(rule)
            efi.append(rule)

        return body_font_family, efi

    def stylize_spine(self):
        self.stylizers = {}
        profile = self.context.source
        css = ''
        for item in self.items:
            html = item.data
            body = html.find(XHTML('body'))
            if 'style' in html.attrib:
                b = body.attrib.get('style', '')
                body.set('style',  html.get('style') + ';' + b)
                del html.attrib['style']
            bs = body.get('style', '').split(';')
            bs.append('margin-top: 0pt')
            bs.append('margin-bottom: 0pt')
            if float(self.context.margin_left) >= 0:
                bs.append('margin-left : %gpt'%
                        float(self.context.margin_left))
            if float(self.context.margin_right) >= 0:
                bs.append('margin-right : %gpt'%
                        float(self.context.margin_right))
            bs.extend(['padding-left: 0pt', 'padding-right: 0pt'])
            if self.page_break_on_body:
                bs.extend(['page-break-before: always'])
            if self.context.change_justification != 'original':
                bs.append('text-align: '+ self.context.change_justification)
            if self.body_font_family:
                bs.append('font-family: '+self.body_font_family)
            body.set('style', '; '.join(bs))
            stylizer = Stylizer(html, item.href, self.oeb, self.context, profile,
                    user_css=self.context.extra_css,
                    extra_css=css)
            self.stylizers[item] = stylizer

    def baseline_node(self, node, stylizer, sizes, csize):
        csize = stylizer.style(node)['font-size']
        if node.text:
            sizes[csize] += len(COLLAPSE.sub(' ', node.text))
        for child in node:
            self.baseline_node(child, stylizer, sizes, csize)
            if child.tail:
                sizes[csize] += len(COLLAPSE.sub(' ', child.tail))

    def baseline_spine(self):
        sizes = defaultdict(float)
        for item in self.items:
            html = item.data
            stylizer = self.stylizers[item]
            body = html.find(XHTML('body'))
            fsize = self.context.source.fbase
            self.baseline_node(body, stylizer, sizes, fsize)
        try:
            sbase = max(list(sizes.items()), key=operator.itemgetter(1))[0]
        except:
            sbase = 12.0
        self.oeb.logger.info(
            "Source base font size is %0.05fpt" % sbase)
        return sbase

    def clean_edges(self, cssdict, style, fsize):
        slineh = self.sbase * 1.26
        dlineh = self.lineh
        for kind in ('margin', 'padding'):
            for edge in ('bottom', 'top'):
                property = f"{kind}-{edge}"
                if property not in cssdict:
                    continue
                if '%' in cssdict[property]:
                    continue
                value = style[property]
                if value == 0 or not isinstance(value, numbers.Number):
                    continue
                if value <= slineh:
                    cssdict[property] = "%0.5fem" % (dlineh / fsize)
                else:
                    try:
                        value = round(value / slineh) * dlineh
                    except:
                        self.oeb.logger.warning(
                                'Invalid length:', value)
                        value = 0.0
                    cssdict[property] = "%0.5fem" % (value / fsize)

    def flatten_node(self, node, stylizer, names, styles, pseudo_styles, psize, item_id, recurse=True):
        if not isinstance(node.tag, string_or_bytes) or namespace(node.tag) not in (XHTML_NS, SVG_NS):
            return
        tag = barename(node.tag)
        style = stylizer.style(node)
        cssdict = style.cssdict()
        try:
            font_size = style['font-size']
        except:
            font_size = self.sbase if self.sbase is not None else \
                self.context.source.fbase
        if tag == 'body' and isinstance(font_size, numbers.Number):
            stylizer.body_font_size = font_size
        if 'align' in node.attrib:
            if tag != 'img':
                cssdict['text-align'] = node.attrib['align']
                if cssdict['text-align'] == 'center':
                    # align=center causes tables to be center aligned,
                    # which text-align does not. And the ever trustworthy Word
                    # uses this construct in its HTML output. See
                    # https://bugs.launchpad.net/bugs/1569583
                    if tag == 'table':
                        if 'margin-left' not in cssdict and 'margin-right' not in cssdict:
                            cssdict['margin-left'] = cssdict['margin-right'] = 'auto'
                    else:
                        for table in node.iterchildren(XHTML("table")):
                            ts = stylizer.style(table)
                            if ts.get('margin-left') is None and ts.get('margin-right') is None:
                                ts.set('margin-left', 'auto')
                                ts.set('margin-right', 'auto')
            else:
                val = node.attrib['align']
                if val in ('middle', 'bottom', 'top'):
                    cssdict['vertical-align'] = val
                elif val in ('left', 'right'):
                    cssdict['float'] = val
            del node.attrib['align']
        if 'valign' in node.attrib and tag == 'td':
            if cssdict.get('vertical-align') == 'inherit':
                cssdict['vertical-align'] = node.attrib['valign']
            del node.attrib['valign']
        if node.tag == XHTML('font'):
            tags = ['descendant::h:%s'%x for x in ('p', 'div', 'table', 'h1',
                'h2', 'h3', 'h4', 'h5', 'h6', 'ol', 'ul', 'dl', 'blockquote')]
            tag = 'div' if XPath('|'.join(tags))(node) else 'span'
            node.tag = XHTML(tag)
            if 'size' in node.attrib:
                def force_int(raw):
                    return int(re.search(r'([0-9+-]+)', raw).group(1))
                size = node.attrib['size'].strip()
                if size:
                    fnums = self.context.source.fnums
                    if size[0] in ('+', '-'):
                        # Oh, the warcrimes
                        try:
                            esize = 3 + force_int(size)
                        except:
                            esize = 3
                        if esize < 1:
                            esize = 1
                        if esize > 7:
                            esize = 7
                        font_size = fnums[esize]
                    else:
                        try:
                            font_size = fnums[force_int(size)]
                        except:
                            font_size = fnums[3]
                    cssdict['font-size'] = '%.1fpt'%font_size
                del node.attrib['size']
            if 'face' in node.attrib:
                cssdict['font-family'] = node.attrib['face']
                del node.attrib['face']
        if 'color' in node.attrib:
            try:
                cssdict['color'] = Property('color', node.attrib['color']).value
            except (ValueError, SyntaxErr):
                pass
            del node.attrib['color']
        if 'bgcolor' in node.attrib:
            try:
                cssdict['background-color'] = Property('background-color', node.attrib['bgcolor']).value
            except (ValueError, SyntaxErr):
                pass
            del node.attrib['bgcolor']
        if tag == 'ol' and 'type' in node.attrib:
            del node.attrib['type']
        if cssdict.get('font-weight', '').lower() == 'medium':
            cssdict['font-weight'] = 'normal'  # ADE chokes on font-weight medium

        fsize = font_size
        is_drop_cap = (cssdict.get('float', None) == 'left' and 'font-size' in cssdict and len(node) == 0 and node.text and (
            len(node.text) == 1 or (len(node.text) == 2 and 0x2000 <= ord(node.text[0]) <= 0x206f)))
        # Detect drop caps generated by the docx input plugin
        if node.tag and node.tag.endswith('}p') and len(node) == 0 and node.text and len(node.text.strip()) == 1 and \
                not node.tail and 'line-height' in cssdict and 'font-size' in cssdict:
            dp = node.getparent()
            if dp.tag and dp.tag.endswith('}div') and len(dp) == 1 and not dp.text:
                if stylizer.style(dp).cssdict().get('float', None) == 'left':
                    is_drop_cap = True
        if style.viewport_relative_font_size:
            cssdict['font-size'] = style.viewport_relative_font_size
        elif not self.context.disable_font_rescaling and not is_drop_cap:
            _sbase = self.sbase if self.sbase is not None else \
                self.context.source.fbase
            dyn_rescale = node.attrib.pop('data-calibre-rescale', None)
            if dyn_rescale is not None:
                try:
                    dyn_rescale = float(dyn_rescale) / 100
                except Exception:
                    dyn_rescale = 1
                fsize = self.fmap[_sbase]
                fsize *= dyn_rescale
                cssdict['font-size'] = '%0.5fem'%(fsize/psize)
                psize = fsize
            elif 'font-size' in cssdict or tag == 'body':
                fsize = self.fmap[font_size]
                try:
                    cssdict['font-size'] = "%0.5fem" % (fsize / psize)
                except ZeroDivisionError:
                    cssdict['font-size'] = '%.1fpt'%fsize
                psize = fsize

        try:
            minlh = self.context.minimum_line_height / 100.
            slh = style['line-height']
            if not is_drop_cap and isinstance(slh, numbers.Number) and slh < minlh * fsize:
                cssdict['line-height'] = str(minlh)
        except Exception:
            self.oeb.logger.exception('Failed to set minimum line-height')

        if cssdict:
            for x in self.filter_css:
                popval = cssdict.pop(x, None)
                if self.body_font_family and popval and x == 'font-family' \
                    and popval.partition(',')[0][1:-1] == self.body_font_family.partition(',')[0][1:-1]:
                    cssdict[x] = popval

        if cssdict:
            if self.lineh and self.fbase and tag not in ('body', 'html'):
                self.clean_edges(cssdict, style, psize)
            if 'display' in cssdict and cssdict['display'] == 'in-line':
                cssdict['display'] = 'inline'
            if self.unfloat and 'float' in cssdict \
               and cssdict.get('display', 'none') != 'none':
                del cssdict['display']
            if self.untable and 'display' in cssdict \
               and cssdict['display'].startswith('table'):
                display = cssdict['display']
                if display == 'table-cell':
                    cssdict['display'] = 'inline'
                else:
                    cssdict['display'] = 'block'
            if 'vertical-align' in cssdict \
               and cssdict['vertical-align'] == 'sup':
                cssdict['vertical-align'] = 'super'
        if self.lineh and 'line-height' not in cssdict and tag != 'html':
            lineh = self.lineh / psize
            cssdict['line-height'] = "%0.5fem" % lineh

        if (self.context.remove_paragraph_spacing or self.context.insert_blank_line) and tag in ('p', 'div'):
            if item_id != 'calibre_jacket' or self.context.output_profile.name == 'Kindle':
                for prop in ('margin', 'padding', 'border'):
                    for edge in ('top', 'bottom'):
                        cssdict['%s-%s'%(prop, edge)] = '0pt'
            if self.context.insert_blank_line:
                cssdict['margin-top'] = cssdict['margin-bottom'] = \
                    '%fem'%self.context.insert_blank_line_size
            indent_size = self.context.remove_paragraph_spacing_indent_size
            keep_indents = indent_size < 0.0
            if (self.context.remove_paragraph_spacing and not keep_indents and cssdict.get('text-align', None) not in ('center', 'right')):
                cssdict['text-indent'] =  "%1.1fem" % indent_size

        pseudo_classes = style.pseudo_classes(self.filter_css)
        if cssdict or pseudo_classes:
            keep_classes = set()

            if cssdict:
                items = sorted(iteritems(cssdict))
                css = ';\n'.join(f'{key}: {val}' for key, val in items)
                classes = node.get('class', '').strip() or 'calibre'
                classes_list = classes.split()
                # lower() because otherwise if the document uses the same class
                # name with different case, both cases will apply, leading
                # to incorrect results.
                klass = ascii_text(STRIPNUM.sub('', classes_list[0])).lower().strip().replace(' ', '_')
                if css in styles:
                    match = styles[css]
                else:
                    match = klass + str(names[klass] or '')
                    styles[css] = match
                    names[klass] += 1
                node.attrib['class'] = match
                keep_classes.add(match)

            for psel, cssdict in iteritems(pseudo_classes):
                items = sorted(iteritems(cssdict))
                css = ';\n'.join(f'{key}: {val}' for key, val in items)
                pstyles = pseudo_styles[psel]
                if css in pstyles:
                    match = pstyles[css]
                else:
                    # We have to use a different class for each psel as
                    # otherwise you can have incorrect styles for a situation
                    # like: a:hover { color: red } a:link { color: blue } a.x:hover { color: green }
                    # If the pcalibre class for a:hover and a:link is the same,
                    # then the class attribute for a.x tags will contain both
                    # that class and the class for a.x:hover, which is wrong.
                    klass = 'pcalibre'
                    match = klass + str(names[klass] or '')
                    pstyles[css] = match
                    names[klass] += 1
                keep_classes.add(match)
                node.attrib['class'] = ' '.join(keep_classes)

        elif 'class' in node.attrib:
            del node.attrib['class']
        if 'style' in node.attrib:
            del node.attrib['style']
        if recurse:
            for child in node:
                self.flatten_node(child, stylizer, names, styles, pseudo_styles, psize, item_id)

    def flatten_head(self, item, href, global_href):
        html = item.data
        head = html.find(XHTML('head'))

        def safe_lower(x):
            try:
                x = x.lower()
            except Exception:
                pass
            return x

        for node in html.xpath('//*[local-name()="style" or local-name()="link"]'):
            if node.tag == XHTML('link') \
               and safe_lower(node.get('rel', 'stylesheet')) == 'stylesheet' \
               and safe_lower(node.get('type', CSS_MIME)) in OEB_STYLES:
                node.getparent().remove(node)
            elif node.tag in (XHTML('style'), SVG('style')) \
                 and node.get('type', CSS_MIME) in OEB_STYLES:
                node.getparent().remove(node)
        href = item.relhref(href)
        l = etree.SubElement(head, XHTML('link'),
            rel='stylesheet', type=CSS_MIME, href=href)
        l.tail='\n'
        if global_href:
            href = item.relhref(global_href)
            l = etree.SubElement(head, XHTML('link'),
                rel='stylesheet', type=CSS_MIME, href=href)
            l.tail = '\n'

    def replace_css(self, css):
        manifest = self.oeb.manifest
        for item in manifest.values():
            if item.media_type in OEB_STYLES:
                manifest.remove(item)
        id, href = manifest.generate('css', 'stylesheet.css')
        sheet = css_parser.parseString(css, validate=False)
        if self.transform_css_rules:
            from calibre.ebooks.css_transform_rules import transform_sheet
            transform_sheet(self.transform_css_rules, sheet)
        item = manifest.add(id, href, CSS_MIME, data=sheet)
        self.oeb.manifest.main_stylesheet = item
        return href

    def collect_global_css(self):
        def rules_in(sheets):
            for s in sheets:
                yield from s.cssRules
        def unique_font_face_rules(*rules):
            seen = set()
            for rule in rules:
                try:
                    ff = rule.style.getPropertyValue('font-family')
                    src = rule.style.getPropertyValue('src')
                    w = rule.style.getPropertyValue('font-weight')
                    s = rule.style.getPropertyValue('font-style')
                except Exception:
                    yield rule
                else:
                    key = ff, src, w, s
                    if key not in seen:
                        seen.add(key)
                        yield rule

        global_css = defaultdict(list)
        for item in self.items:
            stylizer = self.stylizers[item]
            if float(self.context.margin_top) >= 0:
                stylizer.page_rule['margin-top'] = '%gpt'%\
                        float(self.context.margin_top)
            if float(self.context.margin_bottom) >= 0:
                stylizer.page_rule['margin-bottom'] = '%gpt'%\
                        float(self.context.margin_bottom)
            items = sorted(stylizer.page_rule.items())
            css = ';\n'.join(f"{key}: {val}" for key, val in items)
            css = ('@page {\n%s\n}\n'%css) if items else ''
            rules = [css_text(r) for r in unique_font_face_rules(*stylizer.font_face_rules, *rules_in(self.embed_font_rules))]
            raw = '\n\n'.join(rules)
            css += '\n\n' + raw
            global_css[css].append(item)

        gc_map = {}
        manifest = self.oeb.manifest
        for css in global_css:
            href = None
            if css.strip():
                id_, href = manifest.generate('page_css', 'page_styles.css')
                sheet = css_parser.parseString(css, validate=False)
                if self.transform_css_rules:
                    from calibre.ebooks.css_transform_rules import transform_sheet
                    transform_sheet(self.transform_css_rules, sheet)
                manifest.add(id_, href, CSS_MIME, data=sheet)
            gc_map[css] = href

        ans = {}
        for css, items in iteritems(global_css):
            for item in items:
                ans[item] = gc_map[css]
        return ans

    def flatten_spine(self):
        names = defaultdict(int)
        styles, pseudo_styles = {}, defaultdict(dict)
        for item in self.items:
            html = item.data
            stylizer = self.stylizers[item]
            if self.specializer is not None:
                self.specializer(item, stylizer)
            fsize = self.context.dest.fbase
            self.flatten_node(html, stylizer, names, styles, pseudo_styles, fsize, item.id, recurse=False)
            self.flatten_node(html.find(XHTML('body')), stylizer, names, styles, pseudo_styles, fsize, item.id)
        items = sorted(((key, val) for (val, key) in iteritems(styles)), key=lambda x:numeric_sort_key(x[0]))
        # :hover must come after link and :active must come after :hover
        psels = sorted(pseudo_styles, key=lambda x :
                {'hover':1, 'active':2}.get(x, 0))
        for psel in psels:
            styles = pseudo_styles[psel]
            if not styles:
                continue
            x = sorted(((k+':'+psel, v) for v, k in iteritems(styles)))
            items.extend(x)

        css = ''.join(f".{key} {{\n{val};\n}}\n\n" for key, val in items)

        href = self.replace_css(css)
        global_css = self.collect_global_css()
        for item in self.items:
            stylizer = self.stylizers[item]
            self.flatten_head(item, href, global_css[item])
