"""Test for removing false heading markers from single-formula content.

OCR sometimes incorrectly identifies a single formula as a heading by adding '#' prefix.
This test verifies that the heading marker is correctly removed.
"""

import re


def _remove_false_heading_from_single_formula(markdown_content: str) -> str:
    """Remove false heading markers from single-formula content."""
    if not markdown_content or not markdown_content.strip():
        return markdown_content
    
    lines = markdown_content.split('\n')
    
    # Count formulas and heading lines
    formula_count = 0
    heading_lines = []
    has_non_formula_text = False
    
    for i, line in enumerate(lines):
        line_stripped = line.strip()
        
        if not line_stripped:
            continue
        
        # Check if line starts with heading marker
        heading_match = re.match(r'^(#{1,6})\s+(.+)$', line_stripped)
        
        if heading_match:
            heading_level = heading_match.group(1)
            content = heading_match.group(2)
            
            # Check if the heading content is a formula
            if re.fullmatch(r'\$\$?.+\$\$?', content):
                # This is a heading with a formula
                heading_lines.append((i, heading_level, content))
                formula_count += 1
            else:
                # This is a real heading with text
                has_non_formula_text = True
        elif re.fullmatch(r'\$\$?.+\$\$?', line_stripped):
            # Standalone formula line (not in a heading)
            formula_count += 1
        elif line_stripped and not re.match(r'^#+\s*$', line_stripped):
            # Non-empty, non-heading, non-formula line
            has_non_formula_text = True
    
    # Only remove heading markers if:
    # 1. There's exactly one formula
    # 2. That formula is in a heading line
    # 3. There's no other text content
    if formula_count == 1 and len(heading_lines) == 1 and not has_non_formula_text:
        # Remove the heading marker from the formula
        line_idx, heading_level, formula_content = heading_lines[0]
        lines[line_idx] = formula_content
    
    return '\n'.join(lines)


# Test cases
test_cases = [
    # Should remove heading marker (single formula with heading)
    (
        "# $$E = mc^2$$",
        "$$E = mc^2$$",
        "Single display formula with heading"
    ),
    (
        "# $x = y$",
        "$x = y$",
        "Single inline formula with heading"
    ),
    (
        "## $$\\frac{a}{b}$$",
        "$$\\frac{a}{b}$$",
        "Single formula with level-2 heading"
    ),
    (
        "### $$\\lambda_{1}$$",
        "$$\\lambda_{1}$$",
        "Single formula with level-3 heading"
    ),
    
    # Should NOT remove heading marker (has text content)
    (
        "# Introduction\n$$E = mc^2$$",
        "# Introduction\n$$E = mc^2$$",
        "Heading with text + formula (keep heading)"
    ),
    (
        "# Title\nSome text\n$$E = mc^2$$",
        "# Title\nSome text\n$$E = mc^2$$",
        "Heading + text + formula (keep heading)"
    ),
    (
        "$$E = mc^2$$\n# Summary",
        "$$E = mc^2$$\n# Summary",
        "Formula + heading with text (keep heading)"
    ),
    
    # Should NOT remove heading marker (multiple formulas)
    (
        "# $$x = y$$\n$$a = b$$",
        "# $$x = y$$\n$$a = b$$",
        "Multiple formulas (keep heading)"
    ),
    (
        "$$x = y$$\n# $$a = b$$",
        "$$x = y$$\n# $$a = b$$",
        "Two formulas, one with heading (keep heading)"
    ),
    
    # Should NOT remove heading marker (standalone formula without heading)
    (
        "$$E = mc^2$$",
        "$$E = mc^2$$",
        "Single formula without heading (no change)"
    ),
    (
        "$x = y$",
        "$x = y$",
        "Single inline formula without heading (no change)"
    ),
    
    # Edge cases
    (
        "",
        "",
        "Empty string"
    ),
    (
        "# ",
        "# ",
        "Empty heading"
    ),
    (
        "#",
        "#",
        "Just hash symbol"
    ),
    (
        "# $$E = mc^2$$\n\n",
        "$$E = mc^2$$\n\n",
        "Formula with heading and trailing newlines"
    ),
    (
        "\n\n# $$E = mc^2$$",
        "\n\n$$E = mc^2$$",
        "Formula with heading and leading newlines"
    ),
    
    # Complex formulas
    (
        "# $$\\int_{0}^{\\infty} e^{-x^2} dx = \\frac{\\sqrt{\\pi}}{2}$$",
        "$$\\int_{0}^{\\infty} e^{-x^2} dx = \\frac{\\sqrt{\\pi}}{2}$$",
        "Complex integral formula with heading"
    ),
    (
        "# $$\\begin{pmatrix} a & b \\\\ c & d \\end{pmatrix}$$",
        "$$\\begin{pmatrix} a & b \\\\ c & d \\end{pmatrix}$$",
        "Matrix formula with heading"
    ),
]

print("=" * 80)
print("Remove False Heading from Single Formula - Test")
print("=" * 80)

passed = 0
failed = 0

for i, (input_text, expected, description) in enumerate(test_cases, 1):
    result = _remove_false_heading_from_single_formula(input_text)
    
    if result == expected:
        status = "✅ PASS"
        passed += 1
    else:
        status = "❌ FAIL"
        failed += 1
    
    print(f"\n{status} Test {i}: {description}")
    print(f"  Input:    {repr(input_text)}")
    print(f"  Expected: {repr(expected)}")
    print(f"  Got:      {repr(result)}")
    if result != expected:
        print(f"  >>> MISMATCH!")

print("\n" + "=" * 80)
print("SUMMARY")
print("=" * 80)
print(f"Total tests: {len(test_cases)}")
print(f"✅ Passed: {passed}")
print(f"❌ Failed: {failed}")

if failed == 0:
    print("\n✅ All tests passed!")
else:
    print(f"\n⚠️  {failed} test(s) failed")

print("\n" + "=" * 80)
print("KEY SCENARIOS")
print("=" * 80)

key_scenarios = [
    ("# $$E = mc^2$$", "$$E = mc^2$$", "✅ Remove heading"),
    ("# Introduction\n$$E = mc^2$$", "# Introduction\n$$E = mc^2$$", "❌ Keep heading (has text)"),
    ("# $$x = y$$\n$$a = b$$", "# $$x = y$$\n$$a = b$$", "❌ Keep heading (multiple formulas)"),
    ("$$E = mc^2$$", "$$E = mc^2$$", "→ No change (no heading)"),
]

print("\nBehavior Summary:")
for input_text, expected, explanation in key_scenarios:
    result = _remove_false_heading_from_single_formula(input_text)
    match = "✓" if result == expected else "✗"
    print(f"  {match} {explanation}")
    print(f"     {repr(input_text)} → {repr(result)}")

print("\n" + "=" * 80)
print("DECISION LOGIC")
print("=" * 80)
print("""
Remove heading marker ONLY when ALL conditions are met:
1. ✅ Exactly ONE formula in the entire content
2. ✅ That formula is on a line starting with '#' (heading marker)
3. ✅ No other text content exists (only formula and empty lines)

Otherwise: Keep the heading marker as-is.
""")

print("=" * 80)