import type { SupportLogEntryDto, SupportLogFiltersDto, SupportLogListDto, SupportLogSummaryDto } from "@mrp/shared";
import { randomUUID } from "node:crypto";

const SUPPORT_LOG_LIMIT = 500;
const SUPPORT_LOG_RETENTION_DAYS = 14;

const supportLogs: SupportLogEntryDto[] = [];

function serializeContext(context?: Record<string, unknown>) {
  if (!context) {
    return "{}";
  }

  try {
    return JSON.stringify(context);
  } catch {
    return JSON.stringify({ serializationError: "Unable to serialize support log context." });
  }
}

function getRetentionCutoff(now = new Date()) {
  return new Date(now.getTime() - SUPPORT_LOG_RETENTION_DAYS * 24 * 60 * 60 * 1000);
}

function pruneSupportLogs(now = new Date()) {
  const cutoff = getRetentionCutoff(now).getTime();
  const retained = supportLogs.filter((entry) => new Date(entry.createdAt).getTime() >= cutoff);
  supportLogs.length = 0;
  supportLogs.push(...retained.slice(0, SUPPORT_LOG_LIMIT));
}

function normalizeFilters(filters?: SupportLogFiltersDto): SupportLogFiltersDto {
  return {
    level: filters?.level,
    source: filters?.source?.trim() || undefined,
    query: filters?.query?.trim() || undefined,
    start: filters?.start,
    end: filters?.end,
    limit: filters?.limit,
  };
}

function filterSupportLogs(filters?: SupportLogFiltersDto) {
  pruneSupportLogs();

  const normalized = normalizeFilters(filters);
  const startMs = normalized.start ? new Date(normalized.start).getTime() : null;
  const endMs = normalized.end ? new Date(normalized.end).getTime() : null;
  const query = normalized.query?.toLowerCase();
  const limit = Math.max(0, Math.min(normalized.limit ?? 100, SUPPORT_LOG_LIMIT));

  return supportLogs
    .filter((entry) => {
      if (normalized.level && entry.level !== normalized.level) {
        return false;
      }

      if (normalized.source && entry.source !== normalized.source) {
        return false;
      }

      const createdAtMs = new Date(entry.createdAt).getTime();
      if (startMs != null && createdAtMs < startMs) {
        return false;
      }

      if (endMs != null && createdAtMs > endMs) {
        return false;
      }

      if (!query) {
        return true;
      }

      return [entry.source, entry.message, entry.contextJson].some((value) => value.toLowerCase().includes(query));
    })
    .slice(0, limit);
}

function buildSupportLogSummary(entries: SupportLogEntryDto[], totalCount: number, availableSources: string[]): SupportLogSummaryDto {
  return {
    totalCount,
    filteredCount: entries.length,
    sourceCount: availableSources.length,
    retentionDays: SUPPORT_LOG_RETENTION_DAYS,
    oldestEntryAt: entries.length > 0 ? entries[entries.length - 1]?.createdAt ?? null : null,
    newestEntryAt: entries.length > 0 ? entries[0]?.createdAt ?? null : null,
    levelCounts: {
      INFO: entries.filter((entry) => entry.level === "INFO").length,
      WARN: entries.filter((entry) => entry.level === "WARN").length,
      ERROR: entries.filter((entry) => entry.level === "ERROR").length,
    },
  };
}

export function recordSupportLog(entry: {
  level: SupportLogEntryDto["level"];
  source: string;
  message: string;
  context?: Record<string, unknown>;
}) {
  pruneSupportLogs();

  supportLogs.unshift({
    id: randomUUID(),
    level: entry.level,
    source: entry.source,
    message: entry.message,
    contextJson: serializeContext(entry.context),
    createdAt: new Date().toISOString(),
  });

  if (supportLogs.length > SUPPORT_LOG_LIMIT) {
    supportLogs.length = SUPPORT_LOG_LIMIT;
  }
}

export function listSupportLogs(filters?: SupportLogFiltersDto): SupportLogListDto {
  pruneSupportLogs();
  const normalized = normalizeFilters(filters);
  const availableSources = [...new Set(supportLogs.map((entry) => entry.source))].sort();
  const entries = filterSupportLogs(normalized);

  return {
    entries,
    summary: buildSupportLogSummary(entries, supportLogs.length, availableSources),
    availableSources,
    filters: normalized,
  };
}

export function getSupportLogCount() {
  pruneSupportLogs();
  return supportLogs.length;
}

export function getSupportLogRetentionDays() {
  return SUPPORT_LOG_RETENTION_DAYS;
}