import { Router, type IRouter } from "express";
import { eq, sql, desc, and } from "drizzle-orm";
import { db, toolsTable, ratingsTable } from "@workspace/db";
import {
  GetTopToolsQueryParams,
  GetRatingDistributionQueryParams,
} from "@workspace/api-zod";

const router: IRouter = Router();

router.get("/analytics/summary", async (_req, res): Promise<void> => {
  const [toolStats] = await db
    .select({ totalTools: sql<number>`count(*)::int` })
    .from(toolsTable)
    .where(sql`${toolsTable.deletedAt} IS NULL`);

  const [ratingStats] = await db
    .select({
      totalRatings: sql<number>`count(*)::int`,
      avgUsefulness: sql<number | null>`avg(${ratingsTable.usefulness})`,
      avgUsability: sql<number | null>`avg(${ratingsTable.usability})`,
    })
    .from(ratingsTable);

  const [catStats] = await db
    .select({ categoriesCount: sql<number>`count(distinct ${toolsTable.category})::int` })
    .from(toolsTable)
    .where(sql`${toolsTable.deletedAt} IS NULL`);

  const avgCombined = ratingStats.avgUsefulness != null && ratingStats.avgUsability != null
    ? (Number(ratingStats.avgUsefulness) + Number(ratingStats.avgUsability)) / 2
    : null;

  // Most-rated tool
  const [mostRatedRow] = await db
    .select({
      toolId: ratingsTable.toolId,
      ratingCount: sql<number>`count(*)::int`,
    })
    .from(ratingsTable)
    .groupBy(ratingsTable.toolId)
    .orderBy(desc(sql`count(*)`))
    .limit(1);

  let mostRatedTool = null;
  if (mostRatedRow) {
    const [tool] = await db.select().from(toolsTable).where(and(eq(toolsTable.id, mostRatedRow.toolId), sql`${toolsTable.deletedAt} IS NULL`));
    if (tool) {
      const ratingRows = await db
        .select({ usefulness: ratingsTable.usefulness, usability: ratingsTable.usability })
        .from(ratingsTable)
        .where(eq(ratingsTable.toolId, tool.id));
      const rc = ratingRows.length;
      const au = rc > 0 ? ratingRows.reduce((s, r) => s + r.usefulness, 0) / rc : null;
      const aus = rc > 0 ? ratingRows.reduce((s, r) => s + r.usability, 0) / rc : null;
      const ac = au != null && aus != null ? (au + aus) / 2 : null;
      mostRatedTool = { ...tool, ratingCount: rc, avgUsefulness: au, avgUsability: aus, avgCombined: ac };
    }
  }

  res.json({
    totalTools: toolStats?.totalTools ?? 0,
    totalRatings: ratingStats?.totalRatings ?? 0,
    avgUsefulness: ratingStats?.avgUsefulness != null ? Number(ratingStats.avgUsefulness) : null,
    avgUsability: ratingStats?.avgUsability != null ? Number(ratingStats.avgUsability) : null,
    avgCombined,
    categoriesCount: catStats?.categoriesCount ?? 0,
    mostRatedTool,
  });
});

router.get("/analytics/top-tools", async (req, res): Promise<void> => {
  const parsed = GetTopToolsQueryParams.safeParse(req.query);
  if (!parsed.success) {
    res.status(400).json({ error: parsed.error.message });
    return;
  }
  const limit = Math.min(Math.max(parsed.data.limit ?? 10, 1), 50);
  const metric = parsed.data.metric ?? "combined";

  const scoreExpr = metric === "usefulness"
    ? sql`avg(${ratingsTable.usefulness})`
    : metric === "usability"
      ? sql`avg(${ratingsTable.usability})`
      : sql`(avg(${ratingsTable.usefulness}) + avg(${ratingsTable.usability})) / 2`;

  const rows = await db
    .select({
      tool: toolsTable,
      ratingCount: sql<number>`count(${ratingsTable.id})::int`,
      avgUsefulness: sql<number | null>`avg(${ratingsTable.usefulness})`,
      avgUsability: sql<number | null>`avg(${ratingsTable.usability})`,
      score: sql<number>`${scoreExpr}`,
    })
    .from(toolsTable)
    .innerJoin(ratingsTable, eq(ratingsTable.toolId, toolsTable.id))
    .where(sql`${toolsTable.deletedAt} IS NULL`)
    .groupBy(toolsTable.id)
    .orderBy(desc(scoreExpr))
    .limit(limit);

  const scored = rows.map(({ tool, ratingCount, avgUsefulness, avgUsability, score }) => {
    const avgCombined = avgUsefulness != null && avgUsability != null
      ? (Number(avgUsefulness) + Number(avgUsability)) / 2
      : null;
    return {
      tool: {
        ...tool,
        ratingCount,
        avgUsefulness: avgUsefulness != null ? Number(avgUsefulness) : null,
        avgUsability: avgUsability != null ? Number(avgUsability) : null,
        avgCombined,
      },
      score: Number(score),
      ratingCount,
    };
  });

  res.json(scored);
});

router.get("/analytics/by-category", async (_req, res): Promise<void> => {
  const rows = await db
    .select({
      category: toolsTable.category,
      toolCount: sql<number>`count(distinct ${toolsTable.id})::int`,
      totalRatings: sql<number>`count(${ratingsTable.id})::int`,
      avgUsefulness: sql<number | null>`avg(${ratingsTable.usefulness})`,
      avgUsability: sql<number | null>`avg(${ratingsTable.usability})`,
    })
    .from(toolsTable)
    .leftJoin(ratingsTable, eq(ratingsTable.toolId, toolsTable.id))
    .where(sql`${toolsTable.deletedAt} IS NULL`)
    .groupBy(toolsTable.category)
    .orderBy(toolsTable.category);

  res.json(rows.map((r) => ({
    category: r.category,
    toolCount: r.toolCount ?? 0,
    totalRatings: r.totalRatings ?? 0,
    avgUsefulness: r.avgUsefulness != null ? Number(r.avgUsefulness) : null,
    avgUsability: r.avgUsability != null ? Number(r.avgUsability) : null,
  })));
});

router.get("/analytics/rating-distribution", async (req, res): Promise<void> => {
  const parsed = GetRatingDistributionQueryParams.safeParse(req.query);
  if (!parsed.success) {
    res.status(400).json({ error: parsed.error.message });
    return;
  }

  const toolIdFilter = parsed.data.toolId;

  const baseQuery = toolIdFilter
    ? db.select({ usefulness: ratingsTable.usefulness, usability: ratingsTable.usability })
        .from(ratingsTable)
        .where(eq(ratingsTable.toolId, toolIdFilter))
    : db.select({ usefulness: ratingsTable.usefulness, usability: ratingsTable.usability })
        .from(ratingsTable);

  const allRatings = await baseQuery;

  const usefulnessBuckets = [1, 2, 3, 4, 5].map((score) => ({
    score,
    count: allRatings.filter((r) => r.usefulness === score).length,
  }));

  const usabilityBuckets = [1, 2, 3, 4, 5].map((score) => ({
    score,
    count: allRatings.filter((r) => r.usability === score).length,
  }));

  res.json({ usefulness: usefulnessBuckets, usability: usabilityBuckets });
});

export default router;