import { useState } from "react";
import { motion, AnimatePresence } from "motion/react";
import {
  Plus,
  MessageSquare,
  Trash2,
  ChevronLeft,
  ChevronRight,
  Settings,
  LogOut,
} from "lucide-react";
import maintivalogoUrl from "../../../assets/maintiva-logo.jpg";
import type { ChatSession, StoredUser } from "./types";

interface SidebarProps {
  sessions: ChatSession[];
  activeSessionId: string | null;
  isLoadingSessions: boolean;
  user: StoredUser | null;
  onNewChat: () => void;
  onSelectSession: (id: string) => void;
  onDeleteSession: (id: string) => void;
  onLogout: () => void;
  mobileOpen: boolean;
  onMobileClose: () => void;
}

function formatTime(dateStr: string | null | undefined): string {
  if (!dateStr) return "";
  const d = new Date(dateStr);
  const now = new Date();
  const diffMs = now.getTime() - d.getTime();
  const diffDays = Math.floor(diffMs / 86400000);
  if (diffDays === 0) {
    return d.toLocaleTimeString([], { hour: "2-digit", minute: "2-digit" });
  }
  if (diffDays === 1) return "Yesterday";
  if (diffDays < 7) return `${diffDays}d ago`;
  return d.toLocaleDateString([], { month: "short", day: "numeric" });
}

export default function Sidebar({
  sessions,
  activeSessionId,
  isLoadingSessions,
  user,
  onNewChat,
  onSelectSession,
  onDeleteSession,
  onLogout,
  mobileOpen,
  onMobileClose,
}: SidebarProps) {
  const [collapsed, setCollapsed] = useState(false);
  const [hoveredSession, setHoveredSession] = useState<string | null>(null);

  return (
    <>
      {/* Mobile backdrop */}
      <AnimatePresence>
        {mobileOpen && (
          <motion.div
            className="fixed inset-0 bg-black/40 z-40 md:hidden"
            initial={{ opacity: 0 }}
            animate={{ opacity: 1 }}
            exit={{ opacity: 0 }}
            transition={{ duration: 0.2 }}
            onClick={onMobileClose}
          />
        )}
      </AnimatePresence>

      <motion.div
        className={[
          "flex flex-col h-full flex-shrink-0 bg-white border-r border-neutral-100 overflow-hidden",
          // Mobile: fixed overlay drawer; desktop: in-flow
          "fixed inset-y-0 left-0 z-50 md:relative md:inset-auto md:z-auto",
          // Mobile slide in/out; always visible on desktop
          mobileOpen ? "translate-x-0" : "-translate-x-full",
          "md:translate-x-0",
          // CSS transition for mobile only; framer-motion handles desktop width
          "transition-transform duration-300 ease-in-out md:transition-none",
          // Never overflow phone screen
          "max-w-[85vw] md:max-w-none",
        ].join(" ")}
        animate={{ width: collapsed ? 72 : 280 }}
        transition={{ duration: 0.3, ease: "easeInOut" }}
      >
        {/* Collapse toggle — desktop only */}
        <button
          onClick={() => setCollapsed((v) => !v)}
          className="hidden md:flex absolute -right-3 top-1/2 -translate-y-1/2 z-20 w-6 h-6 rounded-full bg-white border border-neutral-200 shadow-sm text-neutral-500 hover:text-brand-green hover:border-brand-green transition-all items-center justify-center"
          aria-label={collapsed ? "Expand sidebar" : "Collapse sidebar"}
        >
          {collapsed ? (
            <ChevronRight className="h-3.5 w-3.5" />
          ) : (
            <ChevronLeft className="h-3.5 w-3.5" />
          )}
        </button>

        {/* Header */}
        <div className="flex items-center gap-3 px-4 py-4 border-b border-neutral-100">
          <motion.div
            className="w-9 h-9 rounded-xl overflow-hidden flex-shrink-0 shadow-md"
            whileHover={{ scale: 1.05 }}
          >
            <img src={maintivalogoUrl} alt="Maintiva" className="w-full h-full object-cover" />
          </motion.div>

          <AnimatePresence>
            {!collapsed && (
              <motion.div
                initial={{ opacity: 0, width: 0 }}
                animate={{ opacity: 1, width: "auto" }}
                exit={{ opacity: 0, width: 0 }}
                transition={{ duration: 0.2 }}
                className="overflow-hidden"
              >
                <p className="font-bold text-neutral-900 text-base whitespace-nowrap">Maintiva Agent</p>
                <p className="text-xs text-neutral-400 whitespace-nowrap">AI Data Assistant</p>
              </motion.div>
            )}
          </AnimatePresence>
        </div>

        {/* New Chat button */}
        <div className="px-3 py-3">
          <button
            onClick={() => { onNewChat(); onMobileClose(); }}
            className={`w-full flex items-center gap-3 rounded-xl px-3 py-2.5 bg-gradient-to-br from-brand-green-light to-brand-green text-white text-sm font-semibold shadow-md shadow-brand-green/20 hover:shadow-lg hover:shadow-brand-green/25 hover:brightness-105 transition-all ${
              collapsed ? "justify-center px-0" : ""
            }`}
          >
            <Plus className="h-4 w-4 flex-shrink-0" />
            <AnimatePresence>
              {!collapsed && (
                <motion.span
                  initial={{ opacity: 0, width: 0 }}
                  animate={{ opacity: 1, width: "auto" }}
                  exit={{ opacity: 0, width: 0 }}
                  transition={{ duration: 0.2 }}
                  className="overflow-hidden whitespace-nowrap"
                >
                  New Chat
                </motion.span>
              )}
            </AnimatePresence>
          </button>
        </div>

        {/* Sessions */}
        <div className="flex-1 overflow-y-auto">
          {!collapsed && sessions.length > 0 && (
            <p className="text-xs font-semibold text-neutral-400 uppercase tracking-wider px-4 pt-2 pb-1">
              Recent
            </p>
          )}

          {isLoadingSessions ? (
            <div className="flex justify-center py-4">
              <div className="w-4 h-4 rounded-full border-2 border-brand-green border-t-transparent animate-spin" />
            </div>
          ) : (
            <div className="px-2 space-y-0.5">
              {sessions.map((session) => {
                const isActive = session.id === activeSessionId;
                return (
                  <div
                    key={session.id}
                    className={`relative flex items-center gap-3 rounded-xl px-3 py-2.5 cursor-pointer transition-all duration-150 ${
                      isActive
                        ? "bg-brand-green-50 text-brand-green"
                        : "text-neutral-700 hover:bg-neutral-50"
                    }`}
                    onClick={() => { onSelectSession(session.id); onMobileClose(); }}
                    onMouseEnter={() => setHoveredSession(session.id)}
                    onMouseLeave={() => setHoveredSession(null)}
                  >
                    <MessageSquare
                      className={`h-4 w-4 flex-shrink-0 ${
                        isActive ? "text-brand-green" : "text-neutral-400"
                      }`}
                    />

                    <AnimatePresence>
                      {!collapsed && (
                        <motion.div
                          initial={{ opacity: 0, width: 0 }}
                          animate={{ opacity: 1, width: "auto" }}
                          exit={{ opacity: 0, width: 0 }}
                          transition={{ duration: 0.2 }}
                          className="flex-1 min-w-0 overflow-hidden"
                        >
                          <p className="text-sm font-medium truncate">{session.title}</p>
                          <p className="text-xs text-neutral-400 truncate">
                            {formatTime(session.updatedAt ?? session.createdAt)}
                          </p>
                        </motion.div>
                      )}
                    </AnimatePresence>

                    {!collapsed && hoveredSession === session.id && (
                      <button
                        onClick={(e) => {
                          e.stopPropagation();
                          onDeleteSession(session.id);
                        }}
                        className="absolute right-2 top-1/2 -translate-y-1/2 p-1.5 rounded-lg text-neutral-400 hover:text-red-500 hover:bg-red-50 transition-all"
                        aria-label="Delete session"
                      >
                        <Trash2 className="h-3.5 w-3.5" />
                      </button>
                    )}
                  </div>
                );
              })}
            </div>
          )}
        </div>

        {/* Footer */}
        <div className="border-t border-neutral-100 p-3">
          <div className="flex items-center gap-3 rounded-xl px-2 py-2">
            <div className="h-7 w-7 rounded-full bg-gradient-to-br from-brand-green-light to-brand-green flex items-center justify-center flex-shrink-0">
              <span className="text-xs font-bold text-white">
                {user?.name?.[0]?.toUpperCase() ?? "U"}
              </span>
            </div>

            <AnimatePresence>
              {!collapsed && (
                <motion.div
                  initial={{ opacity: 0, width: 0 }}
                  animate={{ opacity: 1, width: "auto" }}
                  exit={{ opacity: 0, width: 0 }}
                  transition={{ duration: 0.2 }}
                  className="flex-1 min-w-0 overflow-hidden"
                >
                  <p className="text-sm font-semibold text-neutral-900 truncate whitespace-nowrap">
                    {user?.name ?? "User"}
                  </p>
                  <p className="text-xs text-neutral-400 truncate whitespace-nowrap">
                    {user?.email ?? ""}
                  </p>
                </motion.div>
              )}
            </AnimatePresence>

            {!collapsed && (
              <div className="flex items-center gap-0.5">
                <button
                  className="p-1.5 rounded-lg text-neutral-400 hover:text-brand-green hover:bg-brand-green-50 transition-all"
                  aria-label="Settings"
                >
                  <Settings className="h-4 w-4" />
                </button>
                <button
                  onClick={onLogout}
                  className="p-1.5 rounded-lg text-neutral-400 hover:text-red-500 hover:bg-red-50 transition-all"
                  aria-label="Logout"
                >
                  <LogOut className="h-4 w-4" />
                </button>
              </div>
            )}

            {collapsed && (
              <button
                onClick={onLogout}
                className="p-1.5 rounded-lg text-neutral-400 hover:text-red-500 hover:bg-red-50 transition-all"
                aria-label="Logout"
              >
                <LogOut className="h-4 w-4" />
              </button>
            )}
          </div>
        </div>
      </motion.div>
    </>
  );
}