"""Audit / convert single-line $$...$$ math blocks for SilverBullet compatibility.

SilverBullet's Math library defines block math with the line-anchored marker
regex ^\\$\\$$ for BOTH start and end, so `$$...$$` written on one line never
closes and is rendered as raw text.

Usage:
    python math_fix.py audit   <base_dir>
    python math_fix.py convert <base_dir> [--apply]
"""
import os
import re
import sys

CMD = sys.argv[1]
BASE = sys.argv[2] if len(sys.argv) > 2 else '.'
APPLY = '--apply' in sys.argv

LINE_RE = re.compile(r'^\$\$(.+)\$\$$')


def notes():
    for root, dirs, files in os.walk(BASE):
        if any(x in root for x in ['_scripts', '_text', '_digest', '.git']):
            continue
        for fn in sorted(files):
            if fn.endswith('.md') and fn != 'README.md':
                yield os.path.join(root, fn)


def walk_lines(path):
    """Yield (index, line, in_fence)."""
    fence = False
    lines = open(path, encoding='utf-8').read().split('\n')
    for i, line in enumerate(lines):
        if line.lstrip().startswith('```'):
            yield i, line, fence
            fence = not fence
            continue
        yield i, line, fence


def audit():
    total = indented = multi = in_fence = trailing = 0
    samples = []
    for p in notes():
        for i, line, fence in walk_lines(p):
            s = line.strip()
            if not s.startswith('$$') or s.count('$$') < 2:
                continue
            total += 1
            if fence:
                in_fence += 1
                samples.append(('FENCE', p, i, s[:90]))
            if line != line.lstrip():
                indented += 1
                samples.append(('INDENT', p, i, s[:90]))
            if s.count('$$') > 2:
                multi += 1
                samples.append(('MULTI', p, i, s[:90]))
            if not s.endswith('$$'):
                trailing += 1
                samples.append(('TAILTEXT', p, i, s[-80:]))
    print('单行 $$ 块总数        :', total)
    print('  其中在代码块内      :', in_fence)
    print('  其中带前导缩进      :', indented)
    print('  其中一行含 >2 个 $$ :', multi)
    print('  其中不以 $$ 结尾    :', trailing)
    for kind, p, i, s in samples[:20]:
        print('  [%s] %s:%d  %s' % (kind, os.path.relpath(p, BASE), i + 1, s))


def convert():
    files_changed = 0
    blocks_changed = 0
    skipped = []
    for p in notes():
        lines = open(p, encoding='utf-8').read().split('\n')
        out = []
        fence = False
        n = 0
        for line in lines:
            if line.lstrip().startswith('```'):
                fence = not fence
                out.append(line)
                continue
            m = LINE_RE.match(line)
            if m and not fence:
                body = m.group(1).strip()
                if '$$' in body:
                    skipped.append((os.path.relpath(p, BASE), line[:90]))
                    out.append(line)
                    continue
                out.append('$$')
                out.append(body)
                out.append('$$')
                n += 1
                continue
            out.append(line)
        if n:
            files_changed += 1
            blocks_changed += n
            print('%3d 处  %s' % (n, os.path.relpath(p, BASE)))
            if APPLY:
                with open(p, 'w', encoding='utf-8', newline='\n') as f:
                    f.write('\n'.join(out))
    print()
    print('文件数: %d   转换块数: %d' % (files_changed, blocks_changed))
    if skipped:
        print('跳过（正文含 $$，需人工确认）:')
        for s in skipped:
            print('   ', s)
    print('模式:', '已写入' if APPLY else '预演（未写入，加 --apply 才落盘）')


if __name__ == '__main__':
    if CMD == 'audit':
        audit()
    elif CMD == 'convert':
        convert()
    else:
        raise SystemExit('unknown command: ' + CMD)