#!/usr/bin/env python


__license__   = 'GPL v3'
__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
__docformat__ = 'restructuredtext en'

import os
from collections import defaultdict
from io import BytesIO

from calibre.ebooks.oeb.base import css_text, urlnormalize
from calibre.utils.fonts.subset import subset
from polyglot.builtins import iteritems
from tinycss.fonts3 import parse_font_family


def get_font_properties(rule, default=None):
    '''
    Given a CSS rule, extract normalized font properties from
    it. Note that shorthand font property should already have been expanded
    by the CSS flattening code.
    '''
    props = {}
    s = rule.style
    for q in ('font-family', 'src', 'font-weight', 'font-stretch',
            'font-style'):
        g = 'uri' if q == 'src' else 'value'
        try:
            val = s.getProperty(q).propertyValue[0]
            val = getattr(val, g)
            if q == 'font-family':
                val = parse_font_family(css_text(s.getProperty(q).propertyValue))
                if val and val[0] == 'inherit':
                    val = None
        except (IndexError, KeyError, AttributeError, TypeError, ValueError):
            val = None if q in {'src', 'font-family'} else default
        if q in {'font-weight', 'font-stretch', 'font-style'}:
            val = str(val).lower() if (val or val == 0) else val
            if val == 'inherit':
                val = default
        if q == 'font-weight':
            val = {'normal':'400', 'bold':'700'}.get(val, val)
            if val not in {'100', '200', '300', '400', '500', '600', '700',
                    '800', '900', 'bolder', 'lighter'}:
                val = default
            if val == 'normal':
                val = '400'
        elif q == 'font-style':
            if val not in {'normal', 'italic', 'oblique'}:
                val = default
        elif q == 'font-stretch':
            if val not in {'normal', 'ultra-condensed', 'extra-condensed',
                    'condensed', 'semi-condensed', 'semi-expanded',
                    'expanded', 'extra-expanded', 'ultra-expanded'}:
                val = default
        props[q] = val
    return props


def find_font_face_rules(sheet, oeb):
    '''
    Find all @font-face rules in the given sheet and extract the relevant info from them.
    sheet can be either a ManifestItem or a CSSStyleSheet.
    '''
    ans = []
    try:
        rules = sheet.data.cssRules
    except AttributeError:
        rules = sheet.cssRules

    for i, rule in enumerate(rules):
        if rule.type != rule.FONT_FACE_RULE:
            continue
        props = get_font_properties(rule, default='normal')
        if not props['font-family'] or not props['src']:
            continue

        try:
            path = sheet.abshref(props['src'])
        except AttributeError:
            path = props['src']
        ff = oeb.manifest.hrefs.get(urlnormalize(path), None)
        if not ff:
            continue
        props['item'] = ff
        if props['font-weight'] in {'bolder', 'lighter'}:
            props['font-weight'] = '400'
        props['weight'] = int(props['font-weight'])
        props['rule'] = rule
        props['chars'] = set()
        ans.append(props)

    return ans


def elem_style(style_rules, cls, inherited_style):
    '''
    Find the effective style for the given element.
    '''
    classes = cls.split()
    style = inherited_style.copy()
    for cls in classes:
        style.update(style_rules.get(cls, {}))
    wt = style.get('font-weight', None)
    pwt = inherited_style.get('font-weight', '400')
    if wt == 'bolder':
        style['font-weight'] = {
                '100':'400',
                '200':'400',
                '300':'400',
                '400':'700',
                '500':'700',
                }.get(pwt, '900')
    elif wt == 'lighter':
        style['font-weight'] = {
                '600':'400', '700':'400',
                '800':'700', '900':'700'}.get(pwt, '100')

    return style


class SubsetFonts:

    '''
    Subset all embedded fonts. Must be run after CSS flattening, as it requires
    CSS normalization and flattening to work.
    '''

    def __call__(self, oeb, log, opts):
        self.oeb, self.log, self.opts = oeb, log, opts

        self.find_embedded_fonts()
        if not self.embedded_fonts:
            self.log.debug('No embedded fonts found')
            return
        self.find_style_rules()
        self.find_font_usage()

        totals = [0, 0]

        def remove(font):
            totals[1] += len(font['item'].data)
            self.oeb.manifest.remove(font['item'])
            font['rule'].parentStyleSheet.deleteRule(font['rule'])

        fonts = {}
        for font in self.embedded_fonts:
            item, chars = font['item'], font['chars']
            if item.href in fonts:
                fonts[item.href]['chars'] |= chars
            else:
                fonts[item.href] = font

        for font in fonts.values():
            if not font['chars']:
                self.log('The font %s is unused. Removing it.'%font['src'])
                remove(font)
                continue
            old_raw = font['item'].data
            output = BytesIO()
            font_type = os.path.splitext(font['item'].href)[1][1:].lower()
            try:
                subset(BytesIO(old_raw), output, font_type, font['chars'])
            except Exception as e:
                self.log.warn('The font %s is unsupported for subsetting. %s'%(font['src'], e))
                sz = len(font['item'].data)
                totals[0] += sz
                totals[1] += sz
            else:
                font['item'].data = output.getvalue()
                nlen = len(font['item'].data)
                olen = len(old_raw)
                self.log('Decreased the font %s to %.1f%% of its original size'%
                        (font['src'], nlen/olen *100))
                totals[0] += nlen
                totals[1] += olen

            font['item'].unload_data_from_memory()

        if totals[0]:
            self.log('Reduced total font size to %.1f%% of original'%
                    (totals[0]/totals[1] * 100))

    def find_embedded_fonts(self):
        '''
        Find all @font-face rules and extract the relevant info from them.
        '''
        self.embedded_fonts = []
        for item in self.oeb.manifest:
            try:
                if not hasattr(item.data, 'cssRules'):
                    continue
            except FileNotFoundError:
                continue
            self.embedded_fonts.extend(find_font_face_rules(item, self.oeb))

    def find_style_rules(self):
        '''
        Extract all font related style information from all stylesheets into a
        dict mapping classes to font properties specified by that class. All
        the heavy lifting has already been done by the CSS flattening code.
        '''
        rules = defaultdict(dict)
        for item in self.oeb.manifest:
            if not hasattr(item.data, 'cssRules'):
                continue
            for i, rule in enumerate(item.data.cssRules):
                if rule.type != rule.STYLE_RULE:
                    continue
                props = {k:v for k,v in
                        iteritems(get_font_properties(rule)) if v}
                if not props:
                    continue
                for sel in rule.selectorList:
                    sel = sel.selectorText
                    if sel and sel.startswith('.'):
                        # We dont care about pseudo-selectors as the worst that
                        # can happen is some extra characters will remain in
                        # the font
                        sel = sel.partition(':')[0]
                        rules[sel[1:]].update(props)

        self.style_rules = dict(rules)

    def find_font_usage(self):
        for item in self.oeb.manifest:
            if not hasattr(item.data, 'xpath'):
                continue
            for body in item.data.xpath('//*[local-name()="body"]'):
                base = {'font-family':['serif'], 'font-weight': '400',
                        'font-style':'normal', 'font-stretch':'normal'}
                self.find_usage_in(body, base)

    def used_font(self, style):
        '''
        Given a style find the embedded font that matches it. Returns None if
        no match is found (can happen if no family matches).
        '''
        ff = style.get('font-family', [])
        lnames = {str(x).lower() for x in ff}
        matching_set = []

        # Filter on font-family
        for ef in self.embedded_fonts:
            flnames = {x.lower() for x in ef.get('font-family', [])}
            if not lnames.intersection(flnames):
                continue
            matching_set.append(ef)
        if not matching_set:
            return None

        # Filter on font-stretch
        widths = {x:i for i, x in enumerate(('ultra-condensed',
                'extra-condensed', 'condensed', 'semi-condensed', 'normal',
                'semi-expanded', 'expanded', 'extra-expanded', 'ultra-expanded'
                ))}

        width = widths[style.get('font-stretch', 'normal')]
        for f in matching_set:
            f['width'] = widths[style.get('font-stretch', 'normal')]

        min_dist = min(abs(width-f['width']) for f in matching_set)
        nearest = [f for f in matching_set if abs(width-f['width']) ==
            min_dist]
        if width <= 4:
            lmatches = [f for f in nearest if f['width'] <= width]
        else:
            lmatches = [f for f in nearest if f['width'] >= width]
        matching_set = (lmatches or nearest)

        # Filter on font-style
        fs = style.get('font-style', 'normal')
        order = {
                'oblique':['oblique', 'italic', 'normal'],
                'normal':['normal', 'oblique', 'italic']
            }.get(fs, ['italic', 'oblique', 'normal'])
        for q in order:
            matches = [f for f in matching_set if f.get('font-style', 'normal') == q]
            if matches:
                matching_set = matches
                break

        # Filter on font weight
        fw = int(style.get('font-weight', '400'))
        if fw == 400:
            q = [400, 500, 300, 200, 100, 600, 700, 800, 900]
        elif fw == 500:
            q = [500, 400, 300, 200, 100, 600, 700, 800, 900]
        elif fw < 400:
            q = [fw] + list(range(fw-100, -100, -100)) + list(range(fw+100,
                100, 1000))
        else:
            q = [fw] + list(range(fw+100, 100, 1000)) + list(range(fw-100,
                -100, -100))
        for wt in q:
            matches = [f for f in matching_set if f['weight'] == wt]
            if matches:
                return matches[0]

    def find_chars(self, elem):
        ans = set()
        if elem.text:
            ans |= set(elem.text)
        for child in elem:
            if child.tail:
                ans |= set(child.tail)
        return ans

    def find_usage_in(self, elem, inherited_style):
        style = elem_style(self.style_rules, elem.get('class', '') or '', inherited_style)
        for child in elem:
            self.find_usage_in(child, style)
        font = self.used_font(style)
        if font:
            chars = self.find_chars(elem)
            if chars:
                font['chars'] |= chars
