"use client";

/**
 * MentionsDrawer — the users tagged on a post. Right-side drawer on desktop,
 * bottom sheet on mobile. Read-only for everyone except the post's author,
 * who gets an autocomplete to add people and an X to remove them.
 *
 * `onCountChange(delta)` lets the card update its mentions-icon badge as the
 * author adds/removes, without a refetch.
 */

import { useEffect, useRef, useState } from "react";
import Link from "next/link";
import Image from "next/image";
import { X } from "lucide-react";
import { toast } from "sonner";
import {
  Drawer,
  DrawerContent,
  DrawerHeader,
  DrawerTitle,
} from "@/components/ui/drawer";
import { useMediaQuery } from "@/components/selection-toolbar/shared";
import { posts, type UserSummary } from "@/lib/social";
import { useAuth } from "@/components/auth/auth-provider";
import { MentionAutocomplete } from "@/components/social/mention-autocomplete";
import { cn } from "@/lib/utils";

export function MentionsDrawer({
  open,
  postId,
  authorId,
  onClose,
  onCountChange,
}: {
  open: boolean;
  postId: string;
  authorId: string;
  onClose: () => void;
  onCountChange?: (delta: number) => void;
}) {
  const isMobile = useMediaQuery("(max-width: 767px)");
  const direction = isMobile ? "bottom" : "right";
  const { user } = useAuth();
  const isAuthor = !!user && user.id === authorId;

  const [list, setList] = useState<UserSummary[]>([]);
  const [status, setStatus] = useState<"loading" | "idle" | "error">("loading");
  const reqRef = useRef(0);

  useEffect(() => {
    if (!open) return;
    // Deferred to a timer so the setState calls aren't synchronous in the
    // effect body.
    const t = window.setTimeout(() => {
      const token = ++reqRef.current;
      setStatus("loading");
      posts
        .mentions(postId)
        .then((res) => {
          if (reqRef.current === token) {
            setList(res);
            setStatus("idle");
          }
        })
        .catch(() => {
          if (reqRef.current === token) setStatus("error");
        });
    }, 0);
    return () => window.clearTimeout(t);
  }, [open, postId]);

  async function add(u: UserSummary) {
    if (!u.id || list.some((m) => m.id === u.id)) return;
    setList((prev) => [...prev, u]); // optimistic
    onCountChange?.(1);
    try {
      await posts.addMention(postId, u.id);
    } catch {
      setList((prev) => prev.filter((m) => m.id !== u.id));
      onCountChange?.(-1);
      toast.error("Couldn't add that person");
    }
  }

  async function remove(u: UserSummary) {
    if (!u.id) return;
    setList((prev) => prev.filter((m) => m.id !== u.id)); // optimistic
    onCountChange?.(-1);
    try {
      await posts.removeMention(postId, u.id);
    } catch {
      setList((prev) => [...prev, u]);
      onCountChange?.(1);
      toast.error("Couldn't remove that person");
    }
  }

  return (
    <Drawer
      open={open}
      direction={direction}
      // Let the browser handle the on-screen keyboard. vaul's default
      // input-repositioning resizes/translates the sheet and gets stuck on
      // iOS (stays enlarged after blur, drags dismiss it). The add-field sits
      // at the top of the scrollable body, so it stays visible without it.
      repositionInputs={false}
      onOpenChange={(o) => {
        if (!o) onClose();
      }}
    >
      <DrawerContent
        direction={direction}
        className={cn(
          "bg-card flex flex-col",
          isMobile ? "h-[80vh]" : "h-full w-[88vw] max-w-sm",
        )}
      >
        <DrawerHeader className="border-b border-border text-left">
          <DrawerTitle className="text-base">Mentions</DrawerTitle>
        </DrawerHeader>

        <div className="flex-1 min-h-0 overflow-y-auto">
          {/* Author add-field lives inside the scroll area so its inline
              results scroll with the sheet instead of overflowing a fixed
              header. */}
          {isAuthor ? (
            <div className="p-4 pb-2">
              <MentionAutocomplete
                excludeIds={list.map((m) => m.id).filter((id): id is string => !!id)}
                onSelect={add}
                placeholder="Add someone…"
              />
            </div>
          ) : null}
          {status === "loading" ? (
            <Message>Loading…</Message>
          ) : status === "error" ? (
            <Message>Couldn&apos;t load mentions.</Message>
          ) : list.length === 0 ? (
            <Message>
              {isAuthor ? "No one tagged yet — add someone above." : "No one is tagged."}
            </Message>
          ) : (
            list.map((u) => (
              <div
                key={u.id ?? u.handle}
                className="flex h-16 items-center gap-3 px-4 hover:bg-muted/40"
              >
                <Link
                  href={`/u/${u.handle}`}
                  onClick={onClose}
                  className="flex min-w-0 flex-1 items-center gap-3"
                >
                  <RowAvatar src={u.avatar_url} name={u.name} />
                  <span className="min-w-0">
                    <span className="block truncate text-sm font-semibold text-foreground">
                      {u.name}
                    </span>
                    <span className="block truncate text-sm text-muted-foreground">
                      @{u.handle}
                    </span>
                  </span>
                </Link>
                {isAuthor ? (
                  <button
                    type="button"
                    onClick={() => remove(u)}
                    aria-label={`Remove @${u.handle}`}
                    className="shrink-0 rounded-full p-1.5 text-muted-foreground hover:bg-muted hover:text-foreground"
                  >
                    <X className="size-4" />
                  </button>
                ) : null}
              </div>
            ))
          )}
        </div>
      </DrawerContent>
    </Drawer>
  );
}

function RowAvatar({ src, name }: { src: string | null; name: string }) {
  if (src) {
    return (
      <Image
        src={src}
        alt={name}
        width={40}
        height={40}
        className="size-10 shrink-0 rounded-full object-cover ring-1 ring-foreground/10"
        unoptimized
      />
    );
  }
  const initials =
    name
      .split(/\s+/)
      .map((p) => p[0])
      .slice(0, 2)
      .join("")
      .toUpperCase() || "?";
  return (
    <span className="flex size-10 shrink-0 items-center justify-center rounded-full bg-primary/15 text-sm font-semibold text-primary ring-1 ring-foreground/10">
      {initials}
    </span>
  );
}

function Message({ children }: { children: React.ReactNode }) {
  return (
    <p className="px-4 py-10 text-center text-sm text-muted-foreground">
      {children}
    </p>
  );
}