import { Injectable } from "@nestjs/common";
import { EntryStatus } from "@prisma/client";
import { PrismaService } from "../../prisma/prisma.service";
import type { KnowledgeStats } from "../entities/stats.entity";

/**
 * Service for knowledge base statistics
 */
@Injectable()
export class StatsService {
  constructor(private readonly prisma: PrismaService) {}

  /**
   * Get comprehensive knowledge base statistics
   */
  async getStats(workspaceId: string): Promise<KnowledgeStats> {
    // Run queries in parallel for better performance
    const [
      totalEntries,
      totalTags,
      totalLinks,
      publishedEntries,
      draftEntries,
      archivedEntries,
      entriesWithLinkCounts,
      recentEntries,
      tagsWithCounts,
    ] = await Promise.all([
      // Total entries
      this.prisma.knowledgeEntry.count({
        where: { workspaceId },
      }),

      // Total tags
      this.prisma.knowledgeTag.count({
        where: { workspaceId },
      }),

      // Total links
      this.prisma.knowledgeLink.count({
        where: {
          source: { workspaceId },
        },
      }),

      // Published entries
      this.prisma.knowledgeEntry.count({
        where: {
          workspaceId,
          status: EntryStatus.PUBLISHED,
        },
      }),

      // Draft entries
      this.prisma.knowledgeEntry.count({
        where: {
          workspaceId,
          status: EntryStatus.DRAFT,
        },
      }),

      // Archived entries
      this.prisma.knowledgeEntry.count({
        where: {
          workspaceId,
          status: EntryStatus.ARCHIVED,
        },
      }),

      // Most connected entries
      this.prisma.knowledgeEntry.findMany({
        where: { workspaceId },
        include: {
          _count: {
            select: {
              incomingLinks: true,
              outgoingLinks: true,
            },
          },
        },
        orderBy: {
          incomingLinks: {
            _count: "desc",
          },
        },
        take: 10,
      }),

      // Recent activity
      this.prisma.knowledgeEntry.findMany({
        where: { workspaceId },
        orderBy: {
          updatedAt: "desc",
        },
        take: 10,
        select: {
          id: true,
          slug: true,
          title: true,
          updatedAt: true,
          status: true,
        },
      }),

      // Tag distribution
      this.prisma.knowledgeTag.findMany({
        where: { workspaceId },
        include: {
          _count: {
            select: {
              entries: true,
            },
          },
        },
        orderBy: {
          entries: {
            _count: "desc",
          },
        },
      }),
    ]);

    // Transform most connected entries
    const mostConnected = entriesWithLinkCounts.map((entry) => {
      const incomingLinks = entry._count.incomingLinks;
      const outgoingLinks = entry._count.outgoingLinks;
      return {
        id: entry.id,
        slug: entry.slug,
        title: entry.title,
        incomingLinks,
        outgoingLinks,
        totalConnections: incomingLinks + outgoingLinks,
      };
    });

    // Sort by total connections
    mostConnected.sort((a, b) => b.totalConnections - a.totalConnections);

    // Transform tag distribution
    const tagDistribution = tagsWithCounts.map((tag) => ({
      id: tag.id,
      name: tag.name,
      slug: tag.slug,
      color: tag.color,
      entryCount: tag._count.entries,
    }));

    return {
      overview: {
        totalEntries,
        totalTags,
        totalLinks,
        publishedEntries,
        draftEntries,
        archivedEntries,
      },
      mostConnected,
      recentActivity: recentEntries.map((entry) => ({
        id: entry.id,
        slug: entry.slug,
        title: entry.title,
        updatedAt: entry.updatedAt,
        status: entry.status,
      })),
      tagDistribution,
    };
  }
}