history.py

"""Saving, loading, and comparing DevCheck scan history."""

import json
from pathlib import Path
from typing import Dict, List, Optional


def save_scan(report: Dict, history_path: Path) -> None:
    """Persist a scan report to the history file, overwriting any previous one."""
    history_path.parent.mkdir(parents=True, exist_ok=True)
    with history_path.open("w", encoding="utf-8") as file_handle:
        json.dump(report, file_handle, indent=2)


def load_scan(history_path: Path) -> Optional[Dict]:
    """Load a previously saved scan report, if one exists and is readable."""
    if not history_path.exists():
        return None
    try:
        with history_path.open("r", encoding="utf-8") as file_handle:
            return json.load(file_handle)
    except (json.JSONDecodeError, OSError):
        return None


def compare_scans(previous: Dict, current: Dict) -> List[Dict[str, str]]:
    """Compare two scan reports and return a list of human-readable changes."""
    changes: List[Dict[str, str]] = []

    previous_lookup = {item["tool"]: item for item in previous.get("results", [])}
    current_lookup = {item["tool"]: item for item in current.get("results", [])}

    all_tool_names = sorted(set(previous_lookup) | set(current_lookup))

    for tool_name in all_tool_names:
        old_entry = previous_lookup.get(tool_name)
        new_entry = current_lookup.get(tool_name)

        if old_entry is None and new_entry is not None:
            changes.append({"tool": tool_name, "change": f"New tool tracked: {new_entry['status']}"})
            continue
        if new_entry is None and old_entry is not None:
            changes.append({"tool": tool_name, "change": "Tool no longer tracked"})
            continue
        if old_entry is None or new_entry is None:
            continue

        if old_entry["status"] != new_entry["status"]:
            changes.append(
                {
                    "tool": tool_name,
                    "change": f"Status changed: {old_entry['status']} -> {new_entry['status']}",
                }
            )
        elif old_entry["version"] != new_entry["version"]:
            changes.append(
                {
                    "tool": tool_name,
                    "change": f"Version changed: {old_entry['version']} -> {new_entry['version']}",
                }
            )

    return changes


def print_comparison(changes: List[Dict[str, str]]) -> None:
    """Print a comparison result list produced by compare_scans()."""
    if not changes:
        print("No differences found between the previous scan and the current scan.")
        return

    print(f"{'Tool':<18}{'Change'}")
    for change in changes:
        print(f"{change['tool']:<18}{change['change']}")