"""Study streak and progress analytics."""

from __future__ import annotations

from datetime import date, datetime, timezone
from typing import Any

from plane_mode_scholar.storage.sqlite_store import SQLiteStore


def _parse_date(iso: str) -> datetime | None:
    if not iso:
        return None
    try:
        dt = datetime.fromisoformat(iso.replace("Z", "+00:00"))
        if dt.tzinfo is None:
            dt = dt.replace(tzinfo=timezone.utc)
        return dt
    except ValueError:
        return None


def compute_streak(sessions: list[dict[str, Any]]) -> int:
    """Count consecutive calendar days with completed sessions (UTC)."""
    days: set[str] = set()
    for s in sessions:
        if s.get("status") != "completed":
            continue
        dt = _parse_date(str(s.get("ended_at") or s.get("started_at", "")))
        if dt:
            days.add(dt.date().isoformat())
    if not days:
        return 0
    today = datetime.now(timezone.utc).date()
    cursor = today
    streak = 0
    while cursor.isoformat() in days:
        streak += 1
        cursor = date.fromordinal(cursor.toordinal() - 1)
    return streak


def compute_progress_stats(
    store: SQLiteStore,
    user_id: str,
    pack_id: str | None = None,
) -> dict[str, Any]:
    sessions = [
        s.to_dict()
        for s in store.list_sessions(pack_id=pack_id, user_id=user_id, limit=50)
    ]
    completed = [s for s in sessions if s.get("status") == "completed"]
    active_memories = store.list_memories(pack_id=pack_id, user_id=user_id, status="active")
    quiz_correct = sum(
        1 for m in active_memories if "quiz" in m.tags and m.type.value == "mastery_estimate"
    )
    return {
        "streak_days": compute_streak(sessions),
        "sessions_total": len(sessions),
        "sessions_completed": len(completed),
        "active_memories": len(active_memories),
        "last_session_date": (
            str(completed[0].get("ended_at", ""))[:10] if completed else None
        ),
    }