// TaskList.tsx — left-rail task list. Polls listTasks every 5s, supports client-side search,
// highlights the active task based on the current pathname.
"use client";

import Link from "next/link";
import { usePathname } from "next/navigation";
import { useEffect, useMemo, useState } from "react";
import { ensureDefaultProject, listTasks } from "@/lib/api";
import type { TaskRecord } from "@/lib/types";

function formatRelative(ts: number): string {
  const diff = Math.max(0, Date.now() - ts);
  const s = Math.floor(diff / 1000);
  if (s < 60) return `${s}s ago`;
  const m = Math.floor(s / 60);
  if (m < 60) return `${m}m ago`;
  const h = Math.floor(m / 60);
  if (h < 24) return `${h}h ago`;
  const d = Math.floor(h / 24);
  return `${d}d ago`;
}

export default function TaskList() {
  const pathname = usePathname();
  const [projectId, setProjectId] = useState<string | null>(null);
  const [tasks, setTasks] = useState<TaskRecord[]>([]);
  const [query, setQuery] = useState("");

  // Resolve default project once on mount.
  useEffect(() => {
    let cancelled = false;
    ensureDefaultProject()
      .then((p) => {
        if (!cancelled) setProjectId(p.id);
      })
      .catch(() => {
        /* Swallow — empty state will render. */
      });
    return () => {
      cancelled = true;
    };
  }, []);

  // Poll tasks every 5s while projectId is known and component is mounted.
  useEffect(() => {
    if (!projectId) return;
    let cancelled = false;

    const fetchTasks = async () => {
      try {
        const { tasks: next } = await listTasks(projectId);
        if (!cancelled) setTasks(next);
      } catch {
        /* Keep last-known list on transient failure. */
      }
    };

    fetchTasks();
    const id = setInterval(fetchTasks, 5000);
    return () => {
      cancelled = true;
      clearInterval(id);
    };
  }, [projectId]);

  const filtered = useMemo(() => {
    const q = query.trim().toLowerCase();
    const sorted = [...tasks].sort((a, b) => b.updatedAt - a.updatedAt);
    if (!q) return sorted;
    return sorted.filter((t) => t.title.toLowerCase().includes(q));
  }, [tasks, query]);

  const activeId = useMemo(() => {
    const m = pathname?.match(/\/tasks\/([^/]+)/);
    return m ? m[1] : null;
  }, [pathname]);

  return (
    <div className="flex flex-col min-h-0">
      <div className="px-3 pt-1 pb-2">
        <p className="text-[10px] font-semibold uppercase tracking-widest text-muted-fg px-2 mb-1.5">
          Tasks
        </p>
        <input
          type="text"
          value={query}
          onChange={(e) => setQuery(e.target.value)}
          placeholder="Search tasks…"
          className="w-full rounded-lg border border-border bg-white px-3 py-1.5 text-xs text-foreground placeholder:text-muted-fg focus:outline-none focus:border-accent focus:ring-1 focus:ring-accent/20"
        />
      </div>

      {filtered.length === 0 ? (
        <div className="px-4 py-6 text-center flex flex-col items-center">
          {/* Beaker / flask illustration */}
          <svg className="w-10 h-10 mb-2" viewBox="0 0 40 40" fill="none" aria-hidden="true">
            {/* Flask body */}
            <path
              d="M16 8 L16 18 L8 34 C7 36 8.5 38 11 38 L29 38 C31.5 38 33 36 32 34 L24 18 L24 8"
              stroke="currentColor" className="text-muted-fg/30" strokeWidth="1.2" strokeLinejoin="round" fill="currentColor" fillOpacity="0"
            />
            {/* Liquid fill */}
            <path
              d="M12.5 28 L16.8 20 L23.2 20 L27.5 28 L30 33 C30.5 34 29.8 35 29 35 L11 35 C10.2 35 9.5 34 10 33 Z"
              fill="currentColor" className="text-accent/[0.08]"
            />
            {/* Flask neck rim */}
            <line x1="14" y1="8" x2="26" y2="8" stroke="currentColor" className="text-muted-fg/30" strokeWidth="1.2" strokeLinecap="round" />
            {/* Bubbles */}
            <circle cx="17" cy="30" r="1.5" fill="currentColor" className="text-accent/20" />
            <circle cx="22" cy="27" r="1" fill="currentColor" className="text-accent/15" />
            <circle cx="20" cy="32" r="1.2" fill="currentColor" className="text-accent/20" />
          </svg>
          <p className="text-[11px] text-muted-fg leading-relaxed">
            No tasks yet — start a chat to create one.
          </p>
        </div>
      ) : (
        <ul className="flex-1 overflow-y-auto px-2 pb-2 space-y-0.5">
          {filtered.map((t) => {
            const isActive = t.id === activeId;
            return (
              <li key={t.id}>
                <Link
                  href={`/projects/${t.projectId}/tasks/${t.id}`}
                  className={`group flex items-center gap-2 rounded-lg px-2.5 py-1.5 transition-colors ${
                    isActive
                      ? "bg-accent/10 text-foreground"
                      : "text-foreground-dim hover:bg-muted hover:text-foreground"
                  }`}
                >
                  <span
                    className={`shrink-0 w-1.5 h-1.5 rounded-full ${
                      isActive ? "bg-accent" : "bg-muted-fg/40 group-hover:bg-accent/60"
                    }`}
                  />
                  <span className="flex-1 min-w-0 text-xs font-medium truncate">{t.title}</span>
                  <span className="shrink-0 text-[10px] text-muted-fg font-mono">
                    {formatRelative(t.updatedAt)}
                  </span>
                </Link>
              </li>
            );
          })}
        </ul>
      )}
    </div>
  );
}