"use client";

import { useState, useCallback } from "react";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import { MemberList } from "./member-list";
import { TransferOwnershipModal } from "./transfer-ownership-modal";
import { GROUP_NAME_MAX_LENGTH } from "@/lib/constants";

interface GroupData {
  group: {
    id: string;
    name: string;
    invite_code: string;
    created_by: string;
    created_at: string;
  };
  role: "admin" | "member";
}

export function SettingsPanel({ groupId }: { groupId: string }) {
  const queryClient = useQueryClient();
  const [newName, setNewName] = useState("");
  const [copied, setCopied] = useState(false);
  const [transferTarget, setTransferTarget] = useState<{
    userId: string;
    displayName: string;
  } | null>(null);

  const { data, isLoading, error } = useQuery<GroupData>({
    queryKey: ["groups", groupId],
    queryFn: async () => {
      const res = await fetch(`/api/groups/${groupId}`);
      if (!res.ok) throw new Error("Failed to fetch group");
      return res.json();
    },
    staleTime: 30_000,
  });

  const rename = useMutation({
    mutationFn: async (name: string) => {
      const res = await fetch(`/api/groups/${groupId}`, {
        method: "PATCH",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ name }),
      });
      if (!res.ok) {
        const body = await res.json();
        throw new Error(body.error || "Failed to rename");
      }
      return res.json();
    },
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["groups", groupId] });
      setNewName("");
    },
  });

  const regenerateCode = useMutation({
    mutationFn: async () => {
      const res = await fetch(`/api/groups/${groupId}/invite`, {
        method: "POST",
      });
      if (!res.ok) {
        const body = await res.json();
        throw new Error(body.error || "Failed to regenerate code");
      }
      return res.json();
    },
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["groups", groupId] });
    },
  });

  const deleteGroup = useMutation({
    mutationFn: async () => {
      const res = await fetch(`/api/groups/${groupId}`, { method: "DELETE" });
      if (!res.ok) {
        const body = await res.json();
        throw new Error(body.error || "Failed to delete group");
      }
      return res.json();
    },
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["groups"] });
    },
  });

  const leaveGroup = useMutation({
    mutationFn: async () => {
      const res = await fetch(`/api/groups/${groupId}/leave`, {
        method: "POST",
      });
      if (!res.ok) {
        const body = await res.json();
        throw new Error(body.error || "Failed to leave group");
      }
      return res.json();
    },
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["groups"] });
    },
  });

  const inviteCode = data?.group.invite_code;
  const handleCopyCode = useCallback(async () => {
    if (!inviteCode) return;
    try {
      await navigator.clipboard.writeText(inviteCode);
      setCopied(true);
      setTimeout(() => setCopied(false), 2000);
    } catch {
      // Fallback: select text for manual copy
    }
  }, [inviteCode]);

  const handleTransferRequest = useCallback((userId: string, displayName: string) => {
    setTransferTarget({ userId, displayName });
  }, []);

  if (isLoading) return <p className="text-sm text-gray-500">Loading...</p>;
  if (error) return <p className="text-sm text-red-500">Failed to load group</p>;
  if (!data) return null;

  const isAdmin = data.role === "admin";

  return (
    <div className="space-y-6">
      {/* Invite Code */}
      <div>
        <h3 className="text-sm font-medium mb-2">Invite Code</h3>
        <div className="flex items-center gap-2">
          <code className="rounded bg-gray-100 px-3 py-2 font-mono text-lg dark:bg-gray-800">
            {data.group.invite_code}
          </code>
          <button
            onClick={handleCopyCode}
            className="rounded-md border border-gray-300 px-3 py-2 text-sm hover:bg-gray-50 dark:border-gray-700 dark:hover:bg-gray-800"
            aria-label="Copy invite code"
          >
            {copied ? "Copied!" : "Copy"}
          </button>
          {isAdmin && (
            <button
              onClick={() => regenerateCode.mutate()}
              disabled={regenerateCode.isPending}
              className="rounded-md border border-gray-300 px-3 py-2 text-sm hover:bg-gray-50 disabled:opacity-50 dark:border-gray-700 dark:hover:bg-gray-800"
            >
              {regenerateCode.isPending ? "..." : "Regenerate"}
            </button>
          )}
        </div>
        {regenerateCode.error && (
          <p className="mt-1 text-sm text-red-500">{regenerateCode.error.message}</p>
        )}
      </div>

      {/* Rename (admin only) */}
      {isAdmin && (
        <div>
          <h3 className="text-sm font-medium mb-2">Rename Group</h3>
          <form
            onSubmit={(e) => {
              e.preventDefault();
              const trimmed = newName.trim();
              if (trimmed) rename.mutate(trimmed);
            }}
            className="flex gap-2"
          >
            <input
              type="text"
              value={newName}
              onChange={(e) => setNewName(e.target.value)}
              maxLength={GROUP_NAME_MAX_LENGTH}
              placeholder={data.group.name}
              className="flex-1 rounded-md border border-gray-300 bg-transparent px-3 py-2 text-sm focus:outline-none focus:ring-2 focus:ring-blue-500 dark:border-gray-700"
            />
            <button
              type="submit"
              disabled={rename.isPending || !newName.trim()}
              className="rounded-md bg-blue-600 px-4 py-2 text-sm font-medium text-white hover:bg-blue-700 disabled:opacity-50"
            >
              {rename.isPending ? "..." : "Rename"}
            </button>
          </form>
          {rename.error && <p className="mt-1 text-sm text-red-500">{rename.error.message}</p>}
        </div>
      )}

      {/* Members */}
      <MemberList groupId={groupId} onTransferRequest={handleTransferRequest} />

      {/* Leave / Delete */}
      <div className="border-t border-gray-200 pt-4 dark:border-gray-700">
        {isAdmin ? (
          <div className="space-y-2">
            <button
              onClick={() => {
                if (confirm("Are you sure you want to delete this group? This cannot be undone.")) {
                  deleteGroup.mutate();
                }
              }}
              disabled={deleteGroup.isPending}
              className="w-full rounded-md bg-red-600 px-4 py-2 text-sm font-medium text-white hover:bg-red-700 disabled:opacity-50"
            >
              {deleteGroup.isPending ? "Deleting..." : "Delete Group"}
            </button>
            {deleteGroup.error && (
              <p className="text-sm text-red-500">{deleteGroup.error.message}</p>
            )}
          </div>
        ) : (
          <div className="space-y-2">
            <button
              onClick={() => {
                if (confirm("Are you sure you want to leave this group?")) {
                  leaveGroup.mutate();
                }
              }}
              disabled={leaveGroup.isPending}
              className="w-full rounded-md border border-red-300 px-4 py-2 text-sm font-medium text-red-600 hover:bg-red-50 disabled:opacity-50 dark:border-red-800 dark:text-red-400 dark:hover:bg-red-900/20"
            >
              {leaveGroup.isPending ? "Leaving..." : "Leave Group"}
            </button>
            {leaveGroup.error && <p className="text-sm text-red-500">{leaveGroup.error.message}</p>}
          </div>
        )}
      </div>

      {/* Transfer modal */}
      {transferTarget && (
        <TransferOwnershipModal
          groupId={groupId}
          targetUserId={transferTarget.userId}
          targetDisplayName={transferTarget.displayName}
          onClose={() => setTransferTarget(null)}
        />
      )}
    </div>
  );
}