#!/usr/bin/env python3
"""
Knowledge Store Staleness Detector — Detect stale knowledge entries by comparing source file hashes.

Usage:
    python3 scripts/knowledge_staleness_check.py --index knowledge/index.json
    python3 scripts/knowledge_staleness_check.py --index knowledge/index.json --json
    python3 scripts/knowledge_staleness_check.py --index knowledge/index.json --fix
"""

import argparse
import hashlib
import json
import os
import sys
from datetime import datetime, timezone
from pathlib import Path
from typing import Dict, List, Any, Optional


def compute_file_hash(filepath: str) -> Optional[str]:
    """Compute SHA-256 hash of a file. Returns None if file doesn't exist."""
    try:
        with open(filepath, "rb") as f:
            return "sha256:" + hashlib.sha256(f.read()).hexdigest()
    except (FileNotFoundError, IsADirectoryError, PermissionError):
        return None


def check_staleness(index_path: str, repo_root: str = ".") -> List[Dict[str, Any]]:
    """Check all entries in knowledge index for staleness.
    
    Returns list of entries with staleness info:
    - status: "fresh" | "stale" | "missing_source" | "no_hash"
    - current_hash: computed hash (if source exists)
    - stored_hash: hash from index
    """
    with open(index_path) as f:
        data = json.load(f)

    facts = data.get("facts", [])
    results = []

    for entry in facts:
        source_file = entry.get("source_file")
        stored_hash = entry.get("source_hash")

        if not source_file:
            results.append({**entry, "status": "no_source", "current_hash": None})
            continue

        full_path = os.path.join(repo_root, source_file)
        current_hash = compute_file_hash(full_path)

        if current_hash is None:
            results.append({**entry, "status": "missing_source", "current_hash": None})
        elif not stored_hash:
            results.append({**entry, "status": "no_hash", "current_hash": current_hash})
        elif current_hash != stored_hash:
            results.append({**entry, "status": "stale", "current_hash": current_hash})
        else:
            results.append({**entry, "status": "fresh", "current_hash": current_hash})

    return results


def fix_hashes(index_path: str, repo_root: str = ".") -> int:
    """Add hashes to entries missing them. Returns count of fixed entries."""
    with open(index_path) as f:
        data = json.load(f)

    fixed = 0
    for entry in data.get("facts", []):
        if entry.get("source_hash"):
            continue
        source_file = entry.get("source_file")
        if not source_file:
            continue
        full_path = os.path.join(repo_root, source_file)
        h = compute_file_hash(full_path)
        if h:
            entry["source_hash"] = h
            fixed += 1

    with open(index_path, "w") as f:
        json.dump(data, f, indent=2)

    return fixed


def main():
    parser = argparse.ArgumentParser(description="Check knowledge store staleness")
    parser.add_argument("--index", required=True, help="Path to knowledge/index.json")
    parser.add_argument("--repo", default=".", help="Repo root for source file resolution")
    parser.add_argument("--json", action="store_true", help="Output as JSON")
    parser.add_argument("--fix", action="store_true", help="Add hashes to entries missing them")

    args = parser.parse_args()

    if args.fix:
        fixed = fix_hashes(args.index, args.repo)
        print(f"Fixed {fixed} entries with missing hashes.")
        return

    results = check_staleness(args.index, args.repo)

    if args.json:
        print(json.dumps(results, indent=2))
    else:
        stale = [r for r in results if r["status"] != "fresh"]
        fresh = [r for r in results if r["status"] == "fresh"]

        print(f"Knowledge Store Staleness Check")
        print(f"  Total entries: {len(results)}")
        print(f"  Fresh: {len(fresh)}")
        print(f"  Stale/Issues: {len(stale)}")
        print()

        if stale:
            print("Issues found:")
            for r in stale:
                status = r["status"]
                fact = r.get("fact", "?")[:60]
                source = r.get("source_file", "?")
                print(f"  [{status}] {source}: {fact}")
        else:
            print("All entries are fresh!")


if __name__ == "__main__":
    main()