#!/usr/bin/env python3
"""Update README.md code blocks marked with snippet-source comments from the referenced files.

Usage: python scripts/update_readme_snippets.py [--check]
"""

import argparse
import re
import sys
from pathlib import Path


def get_github_url(file_path: str) -> str:
    """Return the GitHub URL for a repo-relative file path."""
    base_url = "https://github.com/modelcontextprotocol/python-sdk/blob/main"
    return f"{base_url}/{file_path}"


def process_snippet_block(match: re.Match[str], check_mode: bool = False) -> str:
    """Return the regenerated block, or the original in check mode when the code is unchanged."""
    full_match = match.group(0)
    indent = match.group(1)
    file_path = match.group(2)

    try:
        # A missing source file must be fatal: returning the stale block would let --check
        # exit 0, hiding renamed/deleted snippets from CI. SystemExit escapes the
        # `except Exception` below.
        file = Path(file_path)
        if not file.exists():
            sys.exit(f"Error: snippet-source file not found: {file_path}")

        code = file.read_text().rstrip()
        github_url = get_github_url(file_path)

        indented_code = code.replace("\n", f"\n{indent}")
        replacement = f"""{indent}<!-- snippet-source {file_path} -->
{indent}```python
{indent}{indented_code}
{indent}```

{indent}_Full example: [{file_path}]({github_url})_
{indent}<!-- /snippet-source -->"""

        if check_mode:
            existing_content = match.group(3)
            if existing_content is not None:
                existing_lines = existing_content.strip().split("\n")
                code_lines: list[str] = []
                in_code = False
                for line in existing_lines:
                    if line.strip() == "```python":
                        in_code = True
                    elif line.strip() == "```":
                        break
                    elif in_code:
                        code_lines.append(line)
                existing_code = "\n".join(code_lines).strip()
                expected_code = code.replace("\n", f"\n{indent}").strip()
                if existing_code == expected_code:
                    return full_match

        return replacement

    except Exception as e:
        print(f"Error processing {file_path}: {e}")
        return full_match


def update_readme_snippets(check_mode: bool = False) -> bool:
    """Update README.md snippet blocks from their source files.

    Returns False when README.md is missing or check_mode finds stale snippets.
    """
    readme_path = Path("README.md")
    if not readme_path.exists():
        print(f"Error: README file not found: {readme_path}")
        return False

    content = readme_path.read_text()
    original_content = content

    # Matches `<!-- snippet-source path -->` ... `<!-- /snippet-source -->` blocks
    pattern = r"^(\s*)<!-- snippet-source ([^\s]+) -->\n" r"(.*?)" r"^\1<!-- /snippet-source -->"

    updated_content = re.sub(
        pattern, lambda m: process_snippet_block(m, check_mode), content, flags=re.MULTILINE | re.DOTALL
    )

    if check_mode:
        if updated_content != original_content:
            print(
                f"Error: {readme_path} has outdated code snippets. "
                "Run 'python scripts/update_readme_snippets.py' to update."
            )
            return False
        else:
            print(f"✓ {readme_path} code snippets are up to date")
            return True
    else:
        if updated_content != original_content:
            readme_path.write_text(updated_content)
            print(f"✓ Updated {readme_path}")
        else:
            print(f"✓ {readme_path} already up to date")
        return True


def main():
    parser = argparse.ArgumentParser(description="Update README code snippets from source files")
    parser.add_argument(
        "--check", action="store_true", help="Check mode - verify snippets are up to date without modifying"
    )

    args = parser.parse_args()

    success = update_readme_snippets(check_mode=args.check)

    if not success:
        sys.exit(1)


if __name__ == "__main__":
    main()