import { z } from "zod";
import { TRPCError } from "@trpc/server";
import { createTRPCRouter, protectedProcedure } from "../trpc.js";
import { createNotification } from "../lib/create-notification.js";
import { createAuditEntry } from "../lib/audit.js";
import { assertCommentEntityAccess, CommentEntityTypeSchema } from "../lib/comment-entity-registry.js";

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

/**
 * 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: CommentEntityTypeSchema,
        entityId: z.string(),
      }),
    )
    .query(async ({ ctx, input }) => {
      await assertCommentEntityAccess(ctx, input.entityType, input.entityId);

      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" },
      });
    }),

  /** List mention candidates that match the audience of the backing comment entity */
  listMentionCandidates: protectedProcedure
    .input(
      z.object({
        entityType: CommentEntityTypeSchema,
        entityId: z.string(),
        query: z.string().trim().max(100).optional(),
      }),
    )
    .query(async ({ ctx, input }) => {
      const normalizedQuery = input.query && input.query.length > 0 ? input.query : undefined;
      const policy = await assertCommentEntityAccess(ctx, input.entityType, input.entityId);
      return policy.listMentionCandidates(ctx, input.entityId, normalizedQuery);
    }),

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

      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: CommentEntityTypeSchema,
        entityId: z.string(),
        parentId: z.string().optional(),
        body: z.string().min(1).max(10_000),
      }),
    )
    .mutation(async ({ ctx, input }) => {
      const policy = await assertCommentEntityAccess(ctx, input.entityType, input.entityId);
      const authorId = ctx.dbUser?.id;
      if (!authorId) throw new TRPCError({ code: "UNAUTHORIZED" });
      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, entityType: true, entityId: true },
        });
        if (!parent) {
          throw new TRPCError({ code: "NOT_FOUND", message: "Parent comment not found" });
        }
        if (parent.entityType !== input.entityType || parent.entityId !== input.entityId) {
          throw new TRPCError({
            code: "BAD_REQUEST",
            message: "Parent comment does not belong to the requested entity",
          });
        }
      }

      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((userId) =>
            createNotification({
              db: ctx.db,
              userId,
              type: "COMMENT_MENTION",
              title: `${authorName} mentioned you in a comment`,
              body: truncatedBody,
              entityId: input.entityId,
              entityType: input.entityType,
              senderId: authorId,
              link: policy.buildLink(input.entityId),
              channel: "in_app",
            }),
          ),
        );
      }

      void createAuditEntry({
        db: ctx.db,
        entityType: "Comment",
        entityId: comment.id,
        entityName: input.body.slice(0, 50),
        action: "CREATE",
        userId: ctx.dbUser?.id,
        after: comment as unknown as Record<string, unknown>,
        source: "ui",
      });

      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 = ctx.dbUser?.id;
      if (!userId) throw new TRPCError({ code: "UNAUTHORIZED" });
      const dbUser = ctx.dbUser;

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

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

      await assertCommentEntityAccess(ctx, existing.entityType, existing.entityId);

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

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

      void createAuditEntry({
        db: ctx.db,
        entityType: "Comment",
        entityId: input.id,
        action: "UPDATE",
        userId: ctx.dbUser?.id,
        summary: input.resolved ? "Resolved comment" : "Unresolved comment",
        after: updated as unknown as Record<string, unknown>,
        source: "ui",
      });

      return updated;
    }),

  /** 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 = ctx.dbUser?.id;
      if (!userId) throw new TRPCError({ code: "UNAUTHORIZED" });
      const dbUser = ctx.dbUser;

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

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

      await assertCommentEntityAccess(ctx, existing.entityType, existing.entityId);

      const isAdmin = dbUser?.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 } });

      void createAuditEntry({
        db: ctx.db,
        entityType: "Comment",
        entityId: input.id,
        action: "DELETE",
        userId: ctx.dbUser?.id,
        before: existing as unknown as Record<string, unknown>,
        source: "ui",
      });
    }),
});