services/tier_manager.py

"""
Tier Manager — Enforces usage limits for unregistered users.

Uses in-memory session tracking keyed by a session token from the frontend
(stored in localStorage). Lightweight — no database or IP tracking needed.

Unregistered limits:
  - 5 processing sessions per rolling 7-day window
  - 3 files per session
  - 10MB max per file

Registered users bypass all limits (placeholder for Supabase auth integration).
"""
import time
from collections import defaultdict
from models.schemas import TierStatus, TierCheckResponse


# Rolling window: 7 days in seconds
WEEK_SECONDS = 7 * 24 * 60 * 60

# In-memory store: { session_token: [timestamp1, timestamp2, ...] }
_usage_store: dict[str, list[float]] = defaultdict(list)

# Track files per active session: { session_token: int }
_session_file_counts: dict[str, int] = defaultdict(int)

# Limits
UNREGISTERED_SESSIONS_PER_WEEK = 5
UNREGISTERED_FILES_PER_SESSION = 3
UNREGISTERED_MAX_FILE_SIZE_MB = 10


def _prune_old_entries(session_token: str) -> None:
    """Remove usage entries older than 7 days."""
    cutoff = time.time() - WEEK_SECONDS
    _usage_store[session_token] = [
        ts for ts in _usage_store[session_token] if ts > cutoff
    ]


def get_tier_status(session_token: str, is_registered: bool = False) -> TierStatus:
    """Get the current usage status for a session."""
    if is_registered:
        return TierStatus(
            is_registered=True,
            sessions_used=0,
            sessions_limit=999999,
            files_this_session=0,
            files_limit=999999,
            max_file_size_mb=50,
        )

    _prune_old_entries(session_token)

    return TierStatus(
        is_registered=False,
        sessions_used=len(_usage_store[session_token]),
        sessions_limit=UNREGISTERED_SESSIONS_PER_WEEK,
        files_this_session=_session_file_counts.get(session_token, 0),
        files_limit=UNREGISTERED_FILES_PER_SESSION,
        max_file_size_mb=UNREGISTERED_MAX_FILE_SIZE_MB,
    )


def check_upload_allowed(
    session_token: str,
    file_size_bytes: int,
    is_registered: bool = False,
) -> TierCheckResponse:
    """
    Check if the user is allowed to upload a file.
    Returns a TierCheckResponse indicating whether the upload is permitted.
    """
    tier = get_tier_status(session_token, is_registered)

    # Registered users bypass all limits
    if is_registered:
        return TierCheckResponse(allowed=True, tier=tier, message="Registered user — no limits.")

    # Check weekly session limit
    if tier.sessions_used >= UNREGISTERED_SESSIONS_PER_WEEK:
        return TierCheckResponse(
            allowed=False,
            tier=tier,
            message=f"Weekly limit reached ({UNREGISTERED_SESSIONS_PER_WEEK} sessions). Register for unlimited access!",
        )

    # Check files-per-session limit
    if tier.files_this_session >= UNREGISTERED_FILES_PER_SESSION:
        return TierCheckResponse(
            allowed=False,
            tier=tier,
            message=f"File limit reached ({UNREGISTERED_FILES_PER_SESSION} files per session). Register for unlimited uploads!",
        )

    # Check file size
    max_bytes = UNREGISTERED_MAX_FILE_SIZE_MB * 1024 * 1024
    if file_size_bytes > max_bytes:
        return TierCheckResponse(
            allowed=False,
            tier=tier,
            message=f"File too large (max {UNREGISTERED_MAX_FILE_SIZE_MB}MB for free tier). Register for larger uploads!",
        )

    return TierCheckResponse(allowed=True, tier=tier, message="Upload permitted.")


def record_usage(session_token: str) -> None:
    """Record a processing session usage event."""
    _prune_old_entries(session_token)
    _usage_store[session_token].append(time.time())
    _session_file_counts[session_token] = _session_file_counts.get(session_token, 0) + 1


def reset_session_files(session_token: str) -> None:
    """Reset the file count for a new session (called when session starts fresh)."""
    _session_file_counts[session_token] = 0