"""
DocuLens — Usage tracking & tier enforcement.

Middleware that checks a user's monthly page quota before allowing extraction,
and increments the counter after successful processing.
"""

import os
import logging
from datetime import date, datetime
from typing import Optional

logger = logging.getLogger(__name__)

# ---------------------------------------------------------------------------
# Tier configuration
# ---------------------------------------------------------------------------

TIER_LIMITS = {
    "free": 50,
    "starter": 500,
    "pro": 2000,
    "enterprise": 100_000,  # effectively unlimited; real cap set per-contract
}

TIER_FEATURES = {
    "free": {
        "pages_per_month": 50,
        "batch_upload": False,
        "max_batch_files": 0,
        "webhooks": False,
        "priority_models": False,
        "api_access": False,
        "support": "community",
    },
    "starter": {
        "pages_per_month": 500,
        "batch_upload": True,
        "max_batch_files": 10,
        "webhooks": True,
        "priority_models": False,
        "api_access": True,
        "support": "email",
    },
    "pro": {
        "pages_per_month": 2000,
        "batch_upload": True,
        "max_batch_files": 20,
        "webhooks": True,
        "priority_models": True,
        "api_access": True,
        "support": "priority",
    },
    "enterprise": {
        "pages_per_month": 100_000,
        "batch_upload": True,
        "max_batch_files": 50,
        "webhooks": True,
        "priority_models": True,
        "api_access": True,
        "support": "dedicated",
    },
}


def _current_period() -> str:
    """Return the first day of the current month as YYYY-MM-DD."""
    today = date.today()
    return today.replace(day=1).isoformat()


# ---------------------------------------------------------------------------
# Supabase-backed usage tracking
# ---------------------------------------------------------------------------

def _get_supabase():
    """Return the Supabase client, or None if not configured."""
    try:
        from db.supabase import get_client
        return get_client()
    except Exception:
        return None


def get_user_tier(user_id: str) -> str:
    """Look up the user's tier from user_profiles. Defaults to 'free'."""
    sb = _get_supabase()
    if not sb:
        return "free"
    try:
        resp = sb.table("user_profiles").select("tier").eq("id", user_id).single().execute()
        if resp.data:
            return resp.data.get("tier", "free")
    except Exception as e:
        logger.warning("Failed to fetch user tier: %s", e)
    return "free"


def get_usage(user_id: str) -> dict:
    """
    Get the user's current month usage and limits.
    Returns: {tier, pages_used, pages_limit, period_start, remaining}
    """
    tier = get_user_tier(user_id)
    limit = TIER_LIMITS.get(tier, 50)
    period = _current_period()

    sb = _get_supabase()
    pages_used = 0
    if sb:
        try:
            resp = (
                sb.table("usage_tracking")
                .select("pages_used")
                .eq("user_id", user_id)
                .eq("period_start", period)
                .single()
                .execute()
            )
            if resp.data:
                pages_used = resp.data.get("pages_used", 0)
        except Exception as e:
            logger.warning("Failed to fetch usage: %s", e)

    return {
        "tier": tier,
        "pages_used": pages_used,
        "pages_limit": limit,
        "period_start": period,
        "remaining": max(0, limit - pages_used),
    }


def check_quota(user_id: str, pages_requested: int = 1) -> dict:
    """
    Check if the user has enough quota for the requested pages.
    Returns: {allowed: bool, usage: {...}, message: str}
    """
    usage = get_usage(user_id)
    allowed = usage["remaining"] >= pages_requested

    if not allowed:
        msg = (
            f"Monthly quota exceeded. You've used {usage['pages_used']} of "
            f"{usage['pages_limit']} pages on the {usage['tier']} plan. "
            f"Upgrade your plan or wait until next month."
        )
    else:
        msg = "ok"

    return {"allowed": allowed, "usage": usage, "message": msg}


def increment_usage(user_id: str, pages: int = 1) -> bool:
    """
    Increment the user's page count for the current month.
    Creates the usage row if it doesn't exist (upsert).
    Returns True on success.
    """
    sb = _get_supabase()
    if not sb:
        return False

    period = _current_period()
    tier = get_user_tier(user_id)

    try:
        # Try to upsert — on conflict (user_id, period_start), increment
        resp = sb.rpc("increment_usage", {
            "p_user_id": user_id,
            "p_period": period,
            "p_pages": pages,
            "p_tier": tier,
        }).execute()
        return True
    except Exception:
        # Fallback: manual upsert if RPC not available
        try:
            existing = (
                sb.table("usage_tracking")
                .select("id, pages_used")
                .eq("user_id", user_id)
                .eq("period_start", period)
                .maybe_single()
                .execute()
            )
            if existing.data:
                new_count = existing.data["pages_used"] + pages
                sb.table("usage_tracking").update({
                    "pages_used": new_count,
                    "updated_at": datetime.utcnow().isoformat(),
                }).eq("id", existing.data["id"]).execute()
            else:
                sb.table("usage_tracking").insert({
                    "user_id": user_id,
                    "period_start": period,
                    "pages_used": pages,
                    "tier": tier,
                }).execute()
            return True
        except Exception as e:
            logger.error("Failed to increment usage: %s", e)
            return False


def check_feature(user_id: str, feature: str) -> bool:
    """Check if a user's tier includes a specific feature."""
    tier = get_user_tier(user_id)
    tier_features = TIER_FEATURES.get(tier, TIER_FEATURES["free"])
    return bool(tier_features.get(feature, False))


# ---------------------------------------------------------------------------
# SQL function for atomic increment (run in Supabase SQL Editor)
# ---------------------------------------------------------------------------

USAGE_INCREMENT_SQL = """
-- Atomic usage increment — add to schema_additions.sql and run once
CREATE OR REPLACE FUNCTION increment_usage(
    p_user_id TEXT,
    p_period  DATE,
    p_pages   INTEGER,
    p_tier    TEXT DEFAULT 'free'
)
RETURNS void
LANGUAGE plpgsql
AS $$
BEGIN
    INSERT INTO usage_tracking (user_id, period_start, pages_used, tier)
    VALUES (p_user_id, p_period, p_pages, p_tier)
    ON CONFLICT (user_id, period_start)
    DO UPDATE SET
        pages_used = usage_tracking.pages_used + p_pages,
        updated_at = now();
END;
$$;
"""