import { createHash } from "node:crypto";
import { getConfig } from "./config.js";
import { getDb } from "./db.js";
import { readVisitorCookie, isValidVisitorId } from "./visitorCookie.js";

const DEFAULT_DAILY_METRICS_COLLECTION_NAME = "daily_metrics";
const DEFAULT_DAILY_VISITOR_ACTIVITY_COLLECTION_NAME = "daily_visitor_activity";
const DEFAULT_ACTIVITY_RETENTION_DAYS = 60;

const METRIC_FIELDS = [
  "uniqueVisitors",
  "totalVisits",
  "totalMatchStarts",
  "totalMatchFinishes",
  "visitorsWithTwoOrMoreMatches",
  "donationClicks",
];

const EVENT_CONFIG = {
  "match-started": {
    metricField: "totalMatchStarts",
    activityField: "matchStarts",
  },
  "match-finished": {
    metricField: "totalMatchFinishes",
    activityField: "matchFinishes",
  },
  "donation-clicked": {
    metricField: "donationClicks",
    activityField: "donationClicks",
  },
};

let metricsIndexesReady;
let activityIndexesReady;

export async function dailyMetricsRoutes(fastify) {
  fastify.get("/today", async () => {
    return getTodayDailyMetrics();
  });

  fastify.post("/match-started", async (request) => {
    return recordDailyMetricEvent("match-started", {
      visitorId: readVisitorCookie(request),
    });
  });

  fastify.post("/match-finished", async (request) => {
    return recordDailyMetricEvent("match-finished", {
      visitorId: readVisitorCookie(request),
    });
  });

  fastify.post("/donation-clicked", async (request) => {
    return recordDailyMetricEvent("donation-clicked", {
      visitorId: readVisitorCookie(request),
    });
  });
}

export async function recordDailyVisit(visitorId, { now = new Date() } = {}) {
  const date = dayKey(now);
  let uniqueVisitors = 0;

  if (isValidVisitorId(visitorId)) {
    const activityCollection = await getDailyVisitorActivityCollection();
    const activityId = await ensureDailyVisitorActivity(
      activityCollection,
      date,
      visitorId,
      now,
    );
    const uniqueResult = await activityCollection.updateOne(
      {
        _id: activityId,
        dailyUniqueCounted: { $ne: true },
      },
      {
        $set: {
          dailyUniqueCounted: true,
          lastSeenAt: now,
        },
        $inc: {
          visits: 1,
        },
      },
    );

    if (uniqueResult.modifiedCount > 0) {
      uniqueVisitors = 1;
    } else {
      await activityCollection.updateOne(
        { _id: activityId },
        {
          $set: {
            lastSeenAt: now,
          },
          $inc: {
            visits: 1,
          },
        },
      );
    }
  }

  return updateDailyMetrics(date, now, {
    totalVisits: 1,
    uniqueVisitors,
  });
}

export async function recordDailyMetricEvent(eventType, { visitorId, now = new Date() } = {}) {
  const eventConfig = EVENT_CONFIG[eventType];

  if (!eventConfig) {
    throw new Error(`Unknown daily metric event: ${eventType}`);
  }

  const date = dayKey(now);
  const increments = {
    [eventConfig.metricField]: 1,
  };

  if (isValidVisitorId(visitorId)) {
    const countedSecondMatch = await recordDailyVisitorEvent(
      date,
      visitorId,
      eventConfig.activityField,
      now,
    );

    if (countedSecondMatch) {
      increments.visitorsWithTwoOrMoreMatches = 1;
    }
  }

  return updateDailyMetrics(date, now, increments);
}

async function recordDailyVisitorEvent(date, visitorId, activityField, now) {
  const activityCollection = await getDailyVisitorActivityCollection();
  const activityId = await ensureDailyVisitorActivity(
    activityCollection,
    date,
    visitorId,
    now,
  );

  if (activityField !== "matchStarts") {
    await activityCollection.updateOne(
      { _id: activityId },
      {
        $set: {
          lastSeenAt: now,
        },
        $inc: {
          [activityField]: 1,
        },
      },
    );
    return false;
  }

  const secondMatchResult = await activityCollection.updateOne(
    {
      _id: activityId,
      matchStarts: 1,
    },
    {
      $set: {
        lastSeenAt: now,
      },
      $inc: {
        matchStarts: 1,
      },
    },
  );

  if (secondMatchResult.modifiedCount > 0) {
    return true;
  }

  await activityCollection.updateOne(
    { _id: activityId },
    {
      $set: {
        lastSeenAt: now,
      },
      $inc: {
        matchStarts: 1,
      },
    },
  );
  return false;
}

async function ensureDailyVisitorActivity(collection, date, visitorId, now) {
  const visitorHash = dailyVisitorHash(date, visitorId);
  const activityId = `${date}:${visitorHash}`;

  await collection.updateOne(
    { _id: activityId },
    {
      $setOnInsert: {
        _id: activityId,
        date,
        visitorHash,
        dailyUniqueCounted: false,
        visits: 0,
        matchStarts: 0,
        matchFinishes: 0,
        donationClicks: 0,
        firstSeenAt: now,
        expireAt: retentionDate(now),
      },
    },
    { upsert: true },
  );

  return activityId;
}

async function updateDailyMetrics(date, now, increments) {
  const collection = await getDailyMetricsCollection();
  const normalizedIncrements = normalizeIncrements(increments);

  await collection.updateOne(
    { _id: date },
    {
      $setOnInsert: {
        _id: date,
        date,
        createdAt: now,
      },
      $set: {
        updatedAt: now,
      },
      $inc: normalizedIncrements,
    },
    { upsert: true },
  );

  const today = await collection.findOne({ _id: date });
  return formatDailyMetrics(today, date);
}

async function getTodayDailyMetrics(now = new Date()) {
  const date = dayKey(now);
  const collection = await getDailyMetricsCollection();
  const today = await collection.findOne({ _id: date });

  return formatDailyMetrics(today, date);
}

async function getDailyMetricsCollection() {
  const db = await getDb();
  const collection = db.collection(
    getConfig().MONGODB_DAILY_METRICS_COLLECTION || DEFAULT_DAILY_METRICS_COLLECTION_NAME,
  );

  await ensureDailyMetricsIndexes(collection);
  return collection;
}

async function getDailyVisitorActivityCollection() {
  const db = await getDb();
  const collection = db.collection(
    getConfig().MONGODB_DAILY_VISITOR_ACTIVITY_COLLECTION
      || DEFAULT_DAILY_VISITOR_ACTIVITY_COLLECTION_NAME,
  );

  await ensureDailyVisitorActivityIndexes(collection);
  return collection;
}

async function ensureDailyMetricsIndexes(collection) {
  if (!metricsIndexesReady) {
    metricsIndexesReady = collection.createIndex({ updatedAt: -1 });
  }

  return metricsIndexesReady;
}

async function ensureDailyVisitorActivityIndexes(collection) {
  if (!activityIndexesReady) {
    activityIndexesReady = Promise.all([
      collection.createIndex({ date: 1 }),
      collection.createIndex({ expireAt: 1 }, { expireAfterSeconds: 0 }),
    ]);
  }

  return activityIndexesReady;
}

function normalizeIncrements(increments) {
  return Object.entries(increments).reduce((result, [field, value]) => {
    const numericValue = Math.max(0, Math.round(Number(value) || 0));

    if (METRIC_FIELDS.includes(field) && numericValue > 0) {
      result[field] = numericValue;
    }

    return result;
  }, {});
}

function formatDailyMetrics(document, date) {
  return {
    date,
    uniqueVisitors: metricNumber(document?.uniqueVisitors),
    totalVisits: metricNumber(document?.totalVisits),
    totalMatchStarts: metricNumber(document?.totalMatchStarts),
    totalMatchFinishes: metricNumber(document?.totalMatchFinishes),
    visitorsWithTwoOrMoreMatches: metricNumber(document?.visitorsWithTwoOrMoreMatches),
    donationClicks: metricNumber(document?.donationClicks),
    updatedAt: document?.updatedAt?.toISOString?.() ?? null,
  };
}

function metricNumber(value) {
  return Math.max(0, Math.round(Number(value) || 0));
}

function dailyVisitorHash(date, visitorId) {
  return createHash("sha256")
    .update(`${date}:${visitorId}`)
    .digest("hex")
    .slice(0, 32);
}

function retentionDate(now) {
  const retentionDays = getConfig().DAILY_ACTIVITY_RETENTION_DAYS || DEFAULT_ACTIVITY_RETENTION_DAYS;
  return new Date(now.getTime() + retentionDays * 24 * 60 * 60 * 1000);
}

function dayKey(date) {
  const appConfig = getConfig();
  const timeZone = appConfig.ANALYTICS_TIME_ZONE || appConfig.DEATH_STATS_TIME_ZONE || "Asia/Seoul";

  try {
    const parts = new Intl.DateTimeFormat("en-US", {
      day: "2-digit",
      month: "2-digit",
      timeZone,
      year: "numeric",
    })
      .formatToParts(date)
      .reduce((result, part) => {
        result[part.type] = part.value;
        return result;
      }, {});

    return `${parts.year}-${parts.month}-${parts.day}`;
  } catch {
    return date.toISOString().slice(0, 10);
  }
}