import difflib
import json
from datetime import datetime, timezone
from pathlib import Path

STORE_PATH = Path(__file__).parent / "site_content.json"
MAX_SNAPSHOTS = 10

# Multi-page store — one snapshot per URL, refreshed together
MULTI_PAGE_STORE = Path(__file__).parent / "multi_page_content.json"


def _load_store() -> list[dict]:
    if not STORE_PATH.exists():
        return []
    with STORE_PATH.open("r", encoding="utf-8") as f:
        return json.load(f)


def _write_store(snapshots: list[dict]) -> None:
    with STORE_PATH.open("w", encoding="utf-8") as f:
        json.dump(snapshots, f, ensure_ascii=False, indent=2)


def save_site_content(data: dict) -> None:
    snapshots = _load_store()
    entry = {**data, "saved_at": datetime.now(timezone.utc).isoformat()}
    snapshots.append(entry)
    snapshots = snapshots[-MAX_SNAPSHOTS:]
    _write_store(snapshots)


def load_latest_content() -> dict:
    snapshots = _load_store()
    if not snapshots:
        return {}
    return snapshots[-1]


def get_content_diff(snapshot_1: dict, snapshot_2: dict) -> dict:
    text_a = (snapshot_1.get("body_text") or "").splitlines()
    text_b = (snapshot_2.get("body_text") or "").splitlines()

    diff_lines = list(
        difflib.unified_diff(text_a, text_b, lineterm="", n=2)
    )

    if not diff_lines:
        return {"is_changed": False, "summary_of_changes": "No changes detected."}

    added = [l[1:] for l in diff_lines if l.startswith("+") and not l.startswith("+++")]
    removed = [l[1:] for l in diff_lines if l.startswith("-") and not l.startswith("---")]

    parts = []
    if removed:
        parts.append(f"Removed ({len(removed)} line(s)):\n" + "\n".join(f"  - {l}" for l in removed[:5]))
    if added:
        parts.append(f"Added ({len(added)} line(s)):\n" + "\n".join(f"  + {l}" for l in added[:5]))
    if len(removed) > 5 or len(added) > 5:
        parts.append("(truncated — showing first 5 lines per section)")

    return {"is_changed": True, "summary_of_changes": "\n".join(parts)}


def is_content_stale(max_age_minutes: int = 60) -> bool:
    latest = load_latest_content()
    if not latest:
        return True
    saved_at_str = latest.get("saved_at") or latest.get("scraped_at")
    if not saved_at_str:
        return True
    saved_at = datetime.fromisoformat(saved_at_str)
    age_minutes = (datetime.now(timezone.utc) - saved_at).total_seconds() / 60
    return age_minutes > max_age_minutes


# ── Multi-page store ─────────────────────────────────────────────────────────

def save_all_pages(pages: list[dict]) -> None:
    """Save a fresh multi-page snapshot keyed by URL."""
    data = {
        "pages": {p["url"]: p for p in pages},
        "saved_at": datetime.now(timezone.utc).isoformat(),
    }
    MULTI_PAGE_STORE.write_text(json.dumps(data, ensure_ascii=False, indent=2), encoding="utf-8")


def load_all_pages() -> dict[str, dict]:
    """Return the latest multi-page snapshot as {url: page_data}."""
    if not MULTI_PAGE_STORE.exists():
        return {}
    data = json.loads(MULTI_PAGE_STORE.read_text(encoding="utf-8"))
    return data.get("pages", {})


def is_multi_page_stale(max_age_minutes: int = 60) -> bool:
    if not MULTI_PAGE_STORE.exists():
        return True
    data = json.loads(MULTI_PAGE_STORE.read_text(encoding="utf-8"))
    saved_at_str = data.get("saved_at")
    if not saved_at_str:
        return True
    saved_at = datetime.fromisoformat(saved_at_str)
    age_minutes = (datetime.now(timezone.utc) - saved_at).total_seconds() / 60
    return age_minutes > max_age_minutes