#!/usr/bin/env python3
"""Build the standalone CS-Notes website from the published Markdown source."""
from __future__ import annotations

import argparse
import hashlib
import html
import json
import posixpath
import re
import shutil
import tempfile
import unicodedata
import urllib.parse
from collections import Counter
from pathlib import Path

from site_assets import copy_referenced_assets, heading_slug, optimize_images, write_manifest, write_search_index
from check import check

BASE = Path(__file__).resolve().parents[1]
ROOT = BASE / 'upstream'
SITE = BASE / 'templates'
DIST = BASE / 'dist'
CACHE = BASE / '.cache/site-assets'
VERSION_FILE = BASE / 'source-version.json'
SOURCE_COMMIT = json.loads(VERSION_FILE.read_text())['commit'] if VERSION_FILE.is_file() else 'unknown'
IMAGE_BY_NAME = {}
ANCHORS = {}
SOURCE_IMAGE_HOST = 'cs-notes-1256109796.cos.ap-guangzhou.myqcloud.com'
IMAGE = re.compile(r'(<img\b[^>]*?\bsrc=["\'])([^"\']+)(["\'])', re.I)
MD_IMAGE = re.compile(r'(!\[[^\]]*\]\()((?:[^()\s]|\([^()\n]*\))*)(\))')
MD_LINK = re.compile(r'(?<!!)\[((?:[^\[\]\n]|\[[^\[\]\n]*\])+)\]\(([^\s)]+)\)')
# A fence closes only with the same character and at least the same length, so ``` inside a ```` block stays code.
VERBATIM = re.compile(r'^(?P<fence>`{3,}|~{3,})[^\n]*\n[\s\S]*?^(?P=fence)[`~]*[ \t]*$|<!--[\s\S]*?-->', re.M)
HTML_LINK = re.compile(r'(<a\b[^>]*?\bhref=["\'])([^"\']+)(["\'])', re.I)


def sources():
    return [ROOT / 'README.md', ROOT / 'CONTRIBUTING.md',
            *sorted((ROOT / 'notes').glob('*.md')),
            *sorted((ROOT / 'assets').glob('*.md'))]


def image_urls():
    found = set()
    for path in sources():
        text = re.sub(r'```[^\n]*\n[\s\S]*?```|<!--[\s\S]*?-->', '', path.read_text())
        for pattern in (IMAGE, MD_IMAGE):
            for match in pattern.finditer(text):
                url = html.unescape(match[2].strip())
                if url.startswith(('https://', 'http://')):
                    found.add(url)
    return sorted(found)


def repository_images():
    result = {}
    for directory in ('notes/pics', 'assets', 'docs/_media'):
        for path in (ROOT / directory).rglob('*'):
            if path.is_file():
                result.setdefault(path.name, []).append(path)
    return result


def github_slug(text):
    text = re.sub(r'<[^>]+>', '', text).strip().lower().replace('\\', '')
    return ''.join(c for c in text if c in ' -_' or unicodedata.category(c)[0] in 'LN'
                   or unicodedata.category(c) == 'Mn').replace(' ', '-')


def anchor_map(path):
    """Map GitHub heading anchors to the ids Docsify gives the same headings."""
    result, github, docsify, fence = {}, Counter(), Counter(), None
    for line in re.sub(r'<!--[\s\S]*?-->', '', path.read_text()).splitlines():
        marker = re.match(r'^\s*(`{3,}|~{3,})', line)
        if marker:
            fence = marker[1][0] if fence is None else (None if marker[1][0] == fence else fence)
            continue
        heading = re.match(r'^(#{1,6})\s+(.+?)(?:\s+#+)?\s*$', line) if fence is None else None
        if heading:
            slug = github_slug(heading[2])
            count = github[slug]
            github[slug] += 1
            result.setdefault(slug + (f'-{count}' if count else ''), heading_slug(heading[2], docsify))
    return result


def site_anchor(path, fragment):
    fragment = urllib.parse.unquote(fragment)
    return ANCHORS.get(path, {}).get(fragment, fragment)


def local_target(url, source, html_link=False):
    url = html.unescape(url)
    parsed = urllib.parse.urlsplit(url)
    path = urllib.parse.unquote(parsed.path)
    if parsed.netloc.lower() in ('github.com', 'www.github.com'):
        prefix = '/CyC2018/CS-Notes/blob/master/'
        if path.startswith(prefix):
            path = path[len(prefix):]
        else:
            return url
    elif parsed.hostname == SOURCE_IMAGE_HOST:
        candidates = IMAGE_BY_NAME.get(Path(path).name, [])
        if len(candidates) != 1:
            return url
        path = candidates[0].relative_to(ROOT).as_posix()
    elif parsed.netloc:
        return url
    elif not path and url.startswith('#') and len(url) > 1:
        return '#' + site_anchor(source.relative_to(ROOT).as_posix(), url[1:])
    elif not path or url.startswith(('#', 'mailto:', 'data:', '//')):
        return url
    elif not path.startswith('/'):
        path = posixpath.normpath(str(source.relative_to(ROOT).parent / path))
    path = path.lstrip('/')
    if not (ROOT / path).resolve().is_relative_to(ROOT.resolve()) or not (ROOT / path).is_file():
        return url
    if path.endswith('.md'):
        if not html_link:
            result = '/' + urllib.parse.quote(path, safe='/')
            if parsed.fragment:
                result += '#' + urllib.parse.quote(site_anchor(path, parsed.fragment), safe='')
            return result
        if path == 'README.md':
            route = '/'
        else:
            route = '/' + urllib.parse.quote(path[:-3], safe='/')
        if parsed.fragment:
            route += '?id=' + urllib.parse.quote(site_anchor(path, parsed.fragment), safe='')
        return '/#' + route
    return '/' + urllib.parse.quote(path, safe='/')


def render_markdown(path):
    content = path.read_text()
    def image(match):
        url = html.unescape(match[2].strip())
        parsed = urllib.parse.urlsplit(url)
        if parsed.path and not parsed.scheme and not parsed.netloc:
            candidate = (ROOT / urllib.parse.unquote(parsed.path).lstrip('/')) if parsed.path.startswith('/') else (path.parent / urllib.parse.unquote(parsed.path))
            if not candidate.resolve().is_relative_to(ROOT.resolve()) or not candidate.is_file():
                raise ValueError('Missing source image: ' + parsed.path)
        url = local_target(url, path)
        return match[1] + url + match[3]
    def convert(part):
        part = IMAGE.sub(image, part)
        part = MD_IMAGE.sub(image, part)
        part = MD_LINK.sub(lambda m: f'[{m[1]}]({local_target(m[2], path)})', part)
        return HTML_LINK.sub(lambda m: m[1] + local_target(m[2], path, html_link=True) + m[3], part)
    result, last = [], 0
    for match in VERBATIM.finditer(content):
        result += [convert(content[last:match.start()]), match[0]]
        last = match.end()
    return ''.join(result + [convert(content[last:])])


def build(optimize=True):
    global IMAGE_BY_NAME, ANCHORS
    IMAGE_BY_NAME = repository_images()
    ANCHORS = {p.relative_to(ROOT).as_posix(): anchor_map(p) for p in sources()}
    external = image_urls()
    replacements = {url: local_target(url, ROOT / 'README.md') for url in external}
    reused = {url: path for url, path in replacements.items() if path.startswith('/')}
    unchanged_external = [url for url, path in replacements.items() if not path.startswith('/')]
    with tempfile.TemporaryDirectory(prefix='.site-build-', dir=DIST.parent) as temporary:
        dist = Path(temporary) / 'dist'
        dist.mkdir()
        shutil.copytree(SITE / 'vendor', dist / 'vendor')
        for name in ('index.html', 'site.css', 'site.js', 'search.js'):
            shutil.copyfile(SITE / name, dist / name)
        for path in sources():
            target = dist / path.relative_to(ROOT)
            target.parent.mkdir(parents=True, exist_ok=True)
            target.write_text(render_markdown(path))
        homepage = (dist / 'README.md').read_text()
        emojis = {'rocket': '🚀', 'pencil2': '✏️', 'computer': '💻', 'cloud': '☁️', 'floppy_disk': '💾',
                  'coffee': '☕', 'bulb': '💡', 'art': '🎨', 'wrench': '🔧',
                  'watermelon': '🍉', 'memo': '📝'}
        for name, symbol in emojis.items():
            homepage = re.sub(r'^(## ):' + name + r':\s*', r'\1', homepage, flags=re.M)
            homepage = homepage.replace('#' + name + '-', '#')
            homepage = homepage.replace(':' + name + ':', symbol)
        topics = [('学习路线', '🚀'), ('算法', '✏️'), ('操作系统', '💻'), ('网络', '☁️'), ('面向对象', '🎨'),
                  ('数据库', '💾'), ('Java', '☕'), ('系统设计', '💡'), ('工具', '🔧'),
                  ('后记', '📝')]
        cards = '<nav class="topic-grid" aria-label="笔记分类">' + ''.join(
            f'<a href="/#/?id={urllib.parse.quote(label.lower())}"><span aria-hidden="true">{symbol}</span>{label}</a>'
            for label, symbol in topics) + '</nav>'
        homepage = re.sub(r'^\| (?:学习路线|算法)[^\n]*\n\|[^\n]*\n\|[^\n]*', cards, homepage, count=1, flags=re.M)
        homepage = homepage.replace('width="200px"', 'class="site-logo" width="200px"', 1)
        (dist / 'README.md').write_text('# CS-Notes\n\n' + homepage)
        note_paths = ['/' + str(p.relative_to(ROOT).with_suffix('')) for p in sorted((ROOT / 'notes').glob('*.md'))]
        sidebar = ['- [首页](/)', '']
        for line in homepage.splitlines():
            if line.startswith('## '):
                label = re.sub(r':[a-z0-9_]+:', '', line[3:]).strip()
                if label == '后记':
                    break
                sidebar.extend(['', '- **' + label + '**'])
            elif line.startswith('- ['):
                sidebar.append('  ' + re.match(r'- \[[^\]]+\]\([^)]+\)', line).group(0))
        (dist / '_sidebar.md').write_text('\n'.join(sidebar) + '\n')
        (dist / '_404.md').write_text('# 页面暂未找到\n\n请从目录或搜索查找笔记。\n\n[返回首页](/)\n')
        (dist / '.nojekyll').touch()
        shutil.copyfile(ROOT / 'docs/_media/LogoMakr_1J56bI.png', dist / 'favicon.png')
        copy_referenced_assets(dist, ROOT)
        image_report = optimize_images(dist, CACHE) if optimize else {'converted': 0}
        index_name, search_report = write_search_index(dist, sorted((dist / 'notes').glob('*.md')))
        legacy = json.loads((SITE / 'legacy-routes.json').read_text())
        (dist / 'search-paths.js').write_text(
            'window.CS_NOTES_PATHS = ' + json.dumps(note_paths, ensure_ascii=False) + ';\n'
            'window.CS_NOTES_LEGACY_ROUTES = ' + json.dumps(legacy, ensure_ascii=False, separators=(',', ':')) + ';\n'
            'window.CS_NOTES_SEARCH_INDEX = "/' + index_name + '";\n')
        generator = hashlib.sha256()
        for resource in sorted([*Path(__file__).parent.glob('*.py'), *SITE.rglob('*')]):
            if resource.is_file():
                generator.update(resource.relative_to(BASE).as_posix().encode())
                generator.update(resource.read_bytes())
        build_info = {'sourceCommit': SOURCE_COMMIT, 'generatorHash': generator.hexdigest(), 'notes': len(note_paths),
                      'searchIndex': index_name, 'legacyRoutes': len(legacy)}
        (dist / 'build-info.json').write_text(json.dumps(build_info, indent=2) + '\n')
        entry = (dist / 'index.html').read_text()
        for name in ('site.css', 'site.js', 'search.js', 'search-paths.js'):
            digest = hashlib.sha256((dist / name).read_bytes()).hexdigest()[:12]
            entry = entry.replace('/' + name + '"', '/' + name + '?v=' + digest + '"')
        (dist / 'index.html').write_text(entry)
        write_manifest(dist, build_info)
        files = [p for p in dist.rglob('*') if p.is_file()]
        report = {'notes': len(note_paths), 'files': len(files), 'bytes': sum(p.stat().st_size for p in files),
                  'oversized': [str(p.relative_to(dist)) for p in files if p.stat().st_size > 25*1024*1024],
                  'repositoryImagesUsedForOldUrls': len(reused), 'externalImages': len(unchanged_external), 'search': search_report, 'images': image_report, 'legacyRoutes': len(legacy)}
        if report['oversized'] or len(files) > 20000:
            raise ValueError('Static hosting quota exceeded')
        validation = check(ROOT, dist)
        if validation['errors']:
            raise ValueError('Static site validation failed: ' + '; '.join(validation['errors']))
        previous = Path(temporary) / 'previous'
        if DIST.exists():
            DIST.rename(previous)
        try:
            dist.rename(DIST)
        except BaseException:
            if previous.exists():
                previous.rename(DIST)
            raise
    report.update({'sourceCommit': SOURCE_COMMIT, 'imageReplacements': reused, 'externalImageUrls': unchanged_external})
    DIST.with_name(DIST.name + '-report.json').write_text(json.dumps(report, ensure_ascii=False, indent=2) + '\n')
    print(json.dumps({k: v for k, v in report.items() if k not in ('imageReplacements', 'externalImageUrls')}, ensure_ascii=False, indent=2))


if __name__ == '__main__':
    parser = argparse.ArgumentParser(description='仅在本机从最新上游源码生成静态站，不下载图片、不发布。')
    parser.add_argument('--source', type=Path, default=ROOT)
    parser.add_argument('--output', type=Path, default=DIST)
    parser.add_argument('--source-commit', default=SOURCE_COMMIT)
    parser.add_argument('--no-optimize-images', action='store_true')
    args = parser.parse_args()
    ROOT, DIST, SOURCE_COMMIT = args.source.resolve(), args.output.resolve(), args.source_commit
    if not ROOT.is_dir():
        parser.error("源码目录不存在，请先运行 website/refresh.py。")
    if ROOT == DIST or ROOT.is_relative_to(DIST) or DIST.is_relative_to(ROOT):
        parser.error('源码和输出目录必须相互独立。')
    if not DIST.is_relative_to(BASE):
        parser.error('本地验证输出必须保存在当前验证目录中。')
    build(optimize=not args.no_optimize_images)