import { z } from "zod";
import { and, desc, eq, inArray, isNull, sql } from "drizzle-orm";
import { objects } from "@tasks/database/schema";
import { objectTypes } from "@tasks/shared";
import type { Context } from "@/server/trpc";
import { router, protectedProcedure } from "@/server/trpc";

const objectTypeSchema = z.enum(objectTypes);

function escapeIlike(value: string): string {
  return value.replace(/\\/g, "\\\\").replace(/%/g, "\\%").replace(/_/g, "\\_");
}

function makeSnippet(
  description: string | null,
  query: string,
  maxLen = 160,
): string | null {
  if (!description) return null;
  const t = description.trim();
  if (!t) return null;
  const q = query.trim().toLowerCase();
  if (!q) {
    return t.length > maxLen ? `${t.slice(0, maxLen)}…` : t;
  }
  const lower = t.toLowerCase();
  const idx = lower.indexOf(q);
  if (idx === -1) {
    return t.length > maxLen ? `${t.slice(0, maxLen)}…` : t;
  }
  const pad = 48;
  const start = Math.max(0, idx - pad);
  const end = Math.min(t.length, idx + query.length + pad);
  let s = t.slice(start, end);
  if (start > 0) s = `…${s}`;
  if (end < t.length) s = `${s}…`;
  return s;
}

type ParentRow = { parentId: string | null; title: string };

export type SearchResult = {
  id: string;
  type: string;
  title: string;
  status: string | null;
  parentId: string | null;
  workspaceId: string | null;
  descriptionSnippet: string | null;
  parentBreadcrumb: string | null;
};

async function fetchAncestorMap(
  db: Context["db"],
  parentIds: string[],
): Promise<Map<string, ParentRow>> {
  const map = new Map<string, ParentRow>();
  const seen = new Set<string>();
  let frontier = [...new Set(parentIds)];

  while (frontier.length > 0) {
    const batch = await db
      .select({
        id: objects.id,
        parentId: objects.parentId,
        title: objects.title,
      })
      .from(objects)
      .where(inArray(objects.id, frontier));

    const next: string[] = [];
    for (const row of batch) {
      map.set(row.id, { parentId: row.parentId, title: row.title });
      seen.add(row.id);
      if (row.parentId && !seen.has(row.parentId)) {
        next.push(row.parentId);
      }
    }
    frontier = [...new Set(next.filter((id) => !seen.has(id)))];
  }

  return map;
}

function parentBreadcrumb(
  parentId: string | null,
  ancestorMap: Map<string, ParentRow>,
): string | null {
  if (!parentId) return null;
  const parts: string[] = [];
  let cur: string | null = parentId;
  for (let i = 0; i < 32 && cur; i++) {
    const row = ancestorMap.get(cur);
    if (!row) break;
    parts.unshift(row.title);
    cur = row.parentId;
  }
  return parts.length > 0 ? parts.join(" > ") : null;
}

export const searchRouter = router({
  search: protectedProcedure
    .input(
      z.object({
        query: z.string(),
        workspaceId: z.string().uuid().optional(),
        type: objectTypeSchema.optional(),
        limit: z.number().int().positive().max(100).optional(),
      }),
    )
    .query(async ({ ctx, input }) => {
      const limit = input.limit ?? 20;
      const raw = input.query.trim();
      if (raw.length === 0) {
        return { results: [] as SearchResult[] };
      }

      const pattern = `%${escapeIlike(raw)}%`;
      const matchCondition = sql`(${objects.title} ILIKE ${pattern} ESCAPE '\\' OR ${objects.description} ILIKE ${pattern} ESCAPE '\\')`;

      const conditions = [isNull(objects.archivedAt), matchCondition];

      if (input.workspaceId !== undefined) {
        conditions.push(eq(objects.workspaceId, input.workspaceId));
      }
      if (input.type !== undefined) {
        conditions.push(eq(objects.type, input.type));
      }

      const titleFirst = sql<number>`
        CASE
          WHEN ${objects.title} ILIKE ${pattern} ESCAPE '\\' THEN 0
          ELSE 1
        END
      `.mapWith(Number);

      const rows = await ctx.db
        .select({
          id: objects.id,
          type: objects.type,
          title: objects.title,
          status: objects.status,
          parentId: objects.parentId,
          workspaceId: objects.workspaceId,
          description: objects.description,
        })
        .from(objects)
        .where(and(...conditions))
        .orderBy(titleFirst, desc(objects.updatedAt))
        .limit(limit);

      const parentIds = rows
        .map((r) => r.parentId)
        .filter((x): x is string => x != null);

      const ancestorMap =
        parentIds.length > 0
          ? await fetchAncestorMap(ctx.db, parentIds)
          : new Map<string, ParentRow>();

      const results: SearchResult[] = rows.map((r) => ({
        id: r.id,
        type: r.type,
        title: r.title,
        status: r.status,
        parentId: r.parentId,
        workspaceId: r.workspaceId,
        descriptionSnippet: makeSnippet(r.description, raw),
        parentBreadcrumb: parentBreadcrumb(r.parentId, ancestorMap),
      }));

      return { results };
    }),

  recent: protectedProcedure
    .input(
      z.object({
        workspaceId: z.string().uuid().optional(),
        limit: z.number().int().positive().max(50).optional(),
      }),
    )
    .query(async ({ ctx, input }) => {
      const limit = input.limit ?? 10;

      const conditions = [isNull(objects.archivedAt)];
      if (input.workspaceId !== undefined) {
        conditions.push(eq(objects.workspaceId, input.workspaceId));
      }

      const rows = await ctx.db
        .select({
          id: objects.id,
          type: objects.type,
          title: objects.title,
          status: objects.status,
          parentId: objects.parentId,
          workspaceId: objects.workspaceId,
          description: objects.description,
        })
        .from(objects)
        .where(and(...conditions))
        .orderBy(desc(objects.updatedAt))
        .limit(limit);

      const parentIds = rows
        .map((r) => r.parentId)
        .filter((x): x is string => x != null);

      const ancestorMap =
        parentIds.length > 0
          ? await fetchAncestorMap(ctx.db, parentIds)
          : new Map<string, ParentRow>();

      const results: SearchResult[] = rows.map((r) => ({
        id: r.id,
        type: r.type,
        title: r.title,
        status: r.status,
        parentId: r.parentId,
        workspaceId: r.workspaceId,
        descriptionSnippet: makeSnippet(r.description, ""),
        parentBreadcrumb: parentBreadcrumb(r.parentId, ancestorMap),
      }));

      return { results };
    }),
});