# SPDX-FileCopyrightText: Copyright (c) 2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.
# SPDX-License-Identifier: OpenMDW-1.1

"""Strict rich_tabular_v3 reverse reader. Other LaTeX uses the legacy parser."""
import html,re

TAGS={'textstrong':'b','textem':'i','textbf':'b','textit':'i','underline':'u','sout':'s',
      'textsuperscript':'sup','textsubscript':'sub'}

LITERALS={'textbackslash':'\\','textasciitilde':'~','textasciicircum':'^',
          'textless':'<','textgreater':'>'}

def split_top(text,delimiter):
    parts=[];start=0;depth=0;i=0
    while i<len(text):
        if depth==0 and text.startswith(delimiter,i):
            parts.append(text[start:i]);i+=len(delimiter);start=i;continue
        if text[i]=='\\':
            i+=2;continue
        if text[i]=='{':depth+=1
        elif text[i]=='}':depth-=1
        if depth<0:raise ValueError('unbalanced_generated_latex')
        i+=1
    if depth:raise ValueError('unbalanced_generated_latex')
    parts.append(text[start:]);return parts

def argument(text,pos):
    if pos>=len(text) or text[pos]!='{':raise ValueError('expected_braced_argument')
    start=pos+1;depth=1;pos+=1
    while pos<len(text):
        if text[pos]=='\\':pos+=2;continue
        if text[pos]=='{':depth+=1
        elif text[pos]=='}':
            depth-=1
            if depth==0:return text[start:pos],pos+1
        pos+=1
    raise ValueError('unbalanced_generated_latex')

def inline_html(text):
    try:
        from .hybrid_inline import inline_html as decode
    except ImportError:
        from hybrid_inline import inline_html as decode
    return decode(text)

def cell_parts(text):
    text=text.strip();rs=cs=1
    while text.startswith((r'\multicolumn',r'\multirow')):
        command='multicolumn' if text.startswith(r'\multicolumn') else 'multirow';pos=len(command)+1
        count,pos=argument(text,pos);_,pos=argument(text,pos);body,pos=argument(text,pos)
        if text[pos:].strip():raise ValueError('trailing_span_content')
        if command=='multicolumn':cs=int(count)
        else:rs=int(count)
        text=body
    header=False
    if text.startswith(r'\thead{'):
        body,end=argument(text,len(r'\thead'))
        if text[end:].strip():raise ValueError('trailing_header_content')
        text=body
        header=True
    return rs,cs,inline_html(text),header

def to_html(latex):
    m=re.fullmatch(r'\\begin\{tabular\}\{[clrx]+\}\n(.*?)\n\\end\{tabular\}',latex,re.S)
    if not m:raise ValueError('unsupported_generated_tabular')
    rows=split_top(m.group(1),r'\\')
    if rows[-1].strip():raise ValueError('missing_final_row_separator')
    columns=len(re.match(r'\\begin\{tabular\}\{([clrx]+)\}',latex).group(1))
    rows.pop();occupied=set();out=['<table>']
    if not rows or len(rows)>4096 or columns>512:raise ValueError('generated_grid_size')
    for r,row in enumerate(rows):
        out.append('<tr>');c=0
        for part in split_top(row,'&'):
            rs,cs,content,header=cell_parts(part)
            if rs<1 or cs<1 or r+rs>len(rows) or c+cs>columns:raise ValueError('invalid_generated_span')
            if (r,c) in occupied:
                if content or header or rs!=1:raise ValueError('nonempty_span_placeholder')
                if any((r,cc) not in occupied for cc in range(c,c+cs)):raise ValueError('invalid_span_placeholder')
                c+=cs;continue
            if any((rr,cc) in occupied for rr in range(r,r+rs) for cc in range(c,c+cs)):
                raise ValueError('overlapping_generated_span')
            tag='th' if header else 'td'
            out.append('<'+tag+' rowspan="'+str(rs)+'" colspan="'+str(cs)+'">'+content+'</'+tag+'>')
            for rr in range(r,r+rs):
                for cc in range(c,c+cs):occupied.add((rr,cc))
            c+=cs
        if c!=columns:raise ValueError('generated_column_count')
        out.append('</tr>')
    return ''.join(out)+'</table>'