import { z } from "zod";
import { TRPCError } from "@trpc/server";
import { SystemRole } from "@planarchy/shared";
import { createTRPCRouter, protectedProcedure } from "../trpc.js";
import { emitNotificationCreated } from "../sse/event-bus.js";

// ─── Helpers ──────────────────────────────────────────────────────────────────

/** Resolve the DB user id from the session email. Throws UNAUTHORIZED if not found. */
async function resolveUserId(ctx: {
  db: {
    user: {
      findUnique: (args: {
        where: { email: string };
        select: { id: true };
      }) => Promise<{ id: string } | null>;
    };
  };
  session: { user?: { email?: string | null } | null };
}): Promise<string> {
  const email = ctx.session.user?.email;
  if (!email) throw new TRPCError({ code: "UNAUTHORIZED" });
  const user = await ctx.db.user.findUnique({
    where: { email },
    select: { id: true },
  });
  if (!user) throw new TRPCError({ code: "UNAUTHORIZED" });
  return user.id;
}

/**
 * Parse @mentions from comment body.
 * Pattern: @[Display Name](userId)
 * Returns an array of unique user IDs.
 */
function parseMentions(body: string): string[] {
  const regex = /@\[([^\]]+)\]\(([^)]+)\)/g;
  const ids = new Set<string>();
  let match: RegExpExecArray | null;
  while ((match = regex.exec(body)) !== null) {
    ids.add(match[2]!);
  }
  return Array.from(ids);
}

// ─── Router ───────────────────────────────────────────────────────────────────

export const commentRouter = createTRPCRouter({
  /** List comments for a given entity, with author info and 1-level nested replies */
  list: protectedProcedure
    .input(
      z.object({
        entityType: z.string(),
        entityId: z.string(),
      }),
    )
    .query(async ({ ctx, input }) => {
      return ctx.db.comment.findMany({
        where: {
          entityType: input.entityType,
          entityId: input.entityId,
          parentId: null, // only top-level comments
        },
        include: {
          author: { select: { id: true, name: true, email: true, image: true } },
          replies: {
            include: {
              author: { select: { id: true, name: true, email: true, image: true } },
            },
            orderBy: { createdAt: "asc" },
          },
        },
        orderBy: { createdAt: "asc" },
      });
    }),

  /** Count comments for a given entity (used for badge) */
  count: protectedProcedure
    .input(
      z.object({
        entityType: z.string(),
        entityId: z.string(),
      }),
    )
    .query(async ({ ctx, input }) => {
      return ctx.db.comment.count({
        where: {
          entityType: input.entityType,
          entityId: input.entityId,
        },
      });
    }),

  /** Create a comment, parse @mentions, and notify mentioned users */
  create: protectedProcedure
    .input(
      z.object({
        entityType: z.string(),
        entityId: z.string(),
        parentId: z.string().optional(),
        body: z.string().min(1).max(10_000),
      }),
    )
    .mutation(async ({ ctx, input }) => {
      const authorId = await resolveUserId(ctx);
      const mentions = parseMentions(input.body);

      // If replying, verify the parent exists
      if (input.parentId) {
        const parent = await ctx.db.comment.findUnique({
          where: { id: input.parentId },
          select: { id: true },
        });
        if (!parent) {
          throw new TRPCError({ code: "NOT_FOUND", message: "Parent comment not found" });
        }
      }

      const comment = await ctx.db.comment.create({
        data: {
          entityType: input.entityType,
          entityId: input.entityId,
          ...(input.parentId !== undefined ? { parentId: input.parentId } : {}),
          authorId,
          body: input.body,
          mentions,
        },
        include: {
          author: { select: { id: true, name: true, email: true, image: true } },
        },
      });

      // Create notifications for mentioned users (excluding the author)
      const mentionedUserIds = mentions.filter((id) => id !== authorId);
      if (mentionedUserIds.length > 0) {
        const authorName = comment.author.name ?? comment.author.email;
        const truncatedBody =
          input.body.length > 120 ? `${input.body.slice(0, 120)}...` : input.body;

        await Promise.all(
          mentionedUserIds.map(async (userId) => {
            const notification = await ctx.db.notification.create({
              data: {
                userId,
                type: "COMMENT_MENTION",
                title: `${authorName} mentioned you in a comment`,
                body: truncatedBody,
                entityId: input.entityId,
                entityType: input.entityType,
                senderId: authorId,
                link: `/estimates/${input.entityId}?tab=comments`,
                channel: "in_app",
              },
            });
            emitNotificationCreated(userId, notification.id);
          }),
        );
      }

      return comment;
    }),

  /** Resolve or unresolve a comment (author or admin only) */
  resolve: protectedProcedure
    .input(
      z.object({
        id: z.string(),
        resolved: z.boolean().default(true),
      }),
    )
    .mutation(async ({ ctx, input }) => {
      const userId = await resolveUserId(ctx);
      const dbUser = ctx.dbUser;

      const existing = await ctx.db.comment.findUnique({
        where: { id: input.id },
        select: { id: true, authorId: true },
      });

      if (!existing) {
        throw new TRPCError({ code: "NOT_FOUND", message: "Comment not found" });
      }

      // Only the author or an admin can resolve
      const isAdmin = dbUser?.systemRole === SystemRole.ADMIN;
      if (existing.authorId !== userId && !isAdmin) {
        throw new TRPCError({
          code: "FORBIDDEN",
          message: "Only the comment author or an admin can resolve comments",
        });
      }

      return ctx.db.comment.update({
        where: { id: input.id },
        data: { resolved: input.resolved },
        include: {
          author: { select: { id: true, name: true, email: true, image: true } },
        },
      });
    }),

  /** Delete a comment (author or admin only). Hard-deletes, including all replies. */
  delete: protectedProcedure
    .input(z.object({ id: z.string() }))
    .mutation(async ({ ctx, input }) => {
      const userId = await resolveUserId(ctx);
      const dbUser = ctx.dbUser;

      const existing = await ctx.db.comment.findUnique({
        where: { id: input.id },
        select: { id: true, authorId: true },
      });

      if (!existing) {
        throw new TRPCError({ code: "NOT_FOUND", message: "Comment not found" });
      }

      const isAdmin = dbUser?.systemRole === SystemRole.ADMIN;
      if (existing.authorId !== userId && !isAdmin) {
        throw new TRPCError({
          code: "FORBIDDEN",
          message: "Only the comment author or an admin can delete comments",
        });
      }

      // Delete all replies first (they reference this comment as parent)
      await ctx.db.comment.deleteMany({
        where: { parentId: input.id },
      });

      await ctx.db.comment.delete({ where: { id: input.id } });
    }),
});