// Ad Tracking Engine — Impression/Click recording, deduplication, rollups

import type { AdTrackingEvent, PlacementDailyStats } from '@/lib/types/ads';
import type { SurfaceKey } from '@/lib/types/ad-control';

const TRACKING_KEY = 'ad_tracking_events';
const DAILY_STATS_KEY = 'ad_daily_stats';
const DEDUPE_WINDOW_MS = 30_000; // 30 seconds

// --- Persistence ---

function getTrackingStore(): AdTrackingEvent[] {
    if (typeof window === 'undefined') return [];
    try { return JSON.parse(localStorage.getItem(TRACKING_KEY) || '[]'); }
    catch { return []; }
}

function saveTrackingStore(events: AdTrackingEvent[]) {
    if (typeof window === 'undefined') return;
    // Cap at 5000 to avoid localStorage limits
    localStorage.setItem(TRACKING_KEY, JSON.stringify(events.slice(-5000)));
}

function getDailyStatsStore(): PlacementDailyStats[] {
    if (typeof window === 'undefined') return [];
    try { return JSON.parse(localStorage.getItem(DAILY_STATS_KEY) || '[]'); }
    catch { return []; }
}

function saveDailyStatsStore(stats: PlacementDailyStats[]) {
    if (typeof window === 'undefined') return;
    localStorage.setItem(DAILY_STATS_KEY, JSON.stringify(stats));
}

// --- Deduplication ---

function isDuplicate(events: AdTrackingEvent[], newEvent: Omit<AdTrackingEvent, 'id'>): boolean {
    const cutoff = new Date(new Date(newEvent.timestamp).getTime() - DEDUPE_WINDOW_MS).toISOString();
    return events.some(e =>
        e.type === newEvent.type &&
        e.placementId === newEvent.placementId &&
        e.anonId === newEvent.anonId &&
        e.timestamp > cutoff
    );
}

// --- Record Events ---

export function recordImpression(data: {
    placementId: string;
    campaignId: string;
    surfaceKey: SurfaceKey;
    eventId: string;
    userId?: string | null;
    anonId: string;
    sessionId: string;
    device?: string;
    cityId?: string;
}): { success: boolean; deduplicated?: boolean } {
    const store = getTrackingStore();
    const now = new Date().toISOString();

    const event: Omit<AdTrackingEvent, 'id'> = {
        type: 'IMPRESSION',
        placementId: data.placementId,
        campaignId: data.campaignId,
        surfaceKey: data.surfaceKey,
        eventId: data.eventId,
        userId: data.userId || null,
        anonId: data.anonId,
        sessionId: data.sessionId,
        timestamp: now,
        device: data.device || 'unknown',
        cityId: data.cityId || 'unknown',
    };

    if (isDuplicate(store, event)) {
        return { success: true, deduplicated: true };
    }

    const fullEvent: AdTrackingEvent = {
        ...event,
        id: `te-imp-${Date.now()}-${Math.random().toString(36).slice(2, 6)}`,
    };

    store.push(fullEvent);
    saveTrackingStore(store);
    return { success: true };
}

export function recordClick(data: {
    placementId: string;
    campaignId: string;
    surfaceKey: SurfaceKey;
    eventId: string;
    userId?: string | null;
    anonId: string;
    sessionId: string;
    device?: string;
    cityId?: string;
}): { success: boolean } {
    const store = getTrackingStore();
    const now = new Date().toISOString();

    const fullEvent: AdTrackingEvent = {
        id: `te-clk-${Date.now()}-${Math.random().toString(36).slice(2, 6)}`,
        type: 'CLICK',
        placementId: data.placementId,
        campaignId: data.campaignId,
        surfaceKey: data.surfaceKey,
        eventId: data.eventId,
        userId: data.userId || null,
        anonId: data.anonId,
        sessionId: data.sessionId,
        timestamp: now,
        device: data.device || 'unknown',
        cityId: data.cityId || 'unknown',
    };

    store.push(fullEvent);
    saveTrackingStore(store);
    return { success: true };
}

// --- Queries ---

export function getTrackingEvents(campaignId?: string, type?: 'IMPRESSION' | 'CLICK'): AdTrackingEvent[] {
    let events = getTrackingStore();
    if (campaignId) events = events.filter(e => e.campaignId === campaignId);
    if (type) events = events.filter(e => e.type === type);
    return events;
}

export function getUserImpressionCount(anonId: string, campaignId: string, date: string): number {
    const events = getTrackingStore();
    return events.filter(e =>
        e.type === 'IMPRESSION' &&
        e.anonId === anonId &&
        e.campaignId === campaignId &&
        e.timestamp.startsWith(date)
    ).length;
}

export function getTodaySpend(campaignId: string, cpmRate: number): number {
    const today = new Date().toISOString().slice(0, 10);
    const impressions = getTrackingStore().filter(e =>
        e.type === 'IMPRESSION' &&
        e.campaignId === campaignId &&
        e.timestamp.startsWith(today)
    ).length;
    return Number(((impressions / 1000) * cpmRate).toFixed(2));
}

// --- Daily Stats Rollup ---

export function computeDailyStats(campaignId: string, billingModel: string, bid: number): PlacementDailyStats[] {
    const events = getTrackingStore().filter(e => e.campaignId === campaignId);

    // Group by date + surfaceKey
    const buckets: Record<string, { impressions: number; clicks: number; surfaceKey: SurfaceKey; placementId: string }> = {};

    for (const e of events) {
        const date = e.timestamp.slice(0, 10);
        const key = `${date}|${e.surfaceKey}`;
        if (!buckets[key]) {
            buckets[key] = { impressions: 0, clicks: 0, surfaceKey: e.surfaceKey, placementId: e.placementId };
        }
        if (e.type === 'IMPRESSION') buckets[key].impressions++;
        else buckets[key].clicks++;
    }

    return Object.entries(buckets).map(([key, data]) => {
        const [date] = key.split('|');
        let spend = 0;
        if (billingModel === 'CPM') spend = (data.impressions / 1000) * bid;
        else if (billingModel === 'CPC') spend = data.clicks * bid;
        // FIXED: spread evenly (simplified)
        else spend = bid / 30; // assume 30-day campaign

        const ctr = data.impressions > 0 ? data.clicks / data.impressions : 0;

        return {
            id: `ds-${key}`,
            campaignId,
            placementId: data.placementId,
            surfaceKey: data.surfaceKey,
            date,
            impressions: data.impressions,
            clicks: data.clicks,
            ctr: Number(ctr.toFixed(4)),
            spend: Number(spend.toFixed(2)),
        };
    }).sort((a, b) => a.date.localeCompare(b.date));
}