"use client";

import { useState, useMemo } from "react";
import dynamic from "next/dynamic";
import Link from "next/link";
import { trpc } from "~/lib/trpc/client.js";
import { useDebounce } from "~/hooks/useDebounce.js";
import { SortableColumnHeader } from "~/components/ui/SortableColumnHeader.js";
import { useTableSort } from "~/hooks/useTableSort.js";

const SkillDistributionChart = dynamic(
  () => import("~/components/analytics/SkillDistributionChart.js"),
  { ssr: false, loading: () => <div className="h-80 shimmer-skeleton rounded-xl" /> },
);

const PROFICIENCY_LABELS = ["", "Aware", "Basic", "Intermediate", "Advanced", "Expert"];

const PROFICIENCY_CLASSES = [
  "bg-gray-100 text-gray-700 border-gray-300 dark:bg-gray-700 dark:text-gray-200 dark:border-gray-500",
  "bg-blue-100 text-blue-800 border-blue-300 dark:bg-blue-900/60 dark:text-blue-200 dark:border-blue-600",
  "bg-indigo-100 text-indigo-800 border-indigo-300 dark:bg-indigo-900/60 dark:text-indigo-200 dark:border-indigo-500",
  "bg-amber-100 text-amber-800 border-amber-300 dark:bg-amber-900/60 dark:text-amber-200 dark:border-amber-500",
  "bg-green-100 text-green-800 border-green-300 dark:bg-green-900/60 dark:text-green-200 dark:border-green-500",
];

function proficiencyClasses(level: number): string {
  const idx = Math.max(0, Math.min(4, Math.round(level) - 1));
  return PROFICIENCY_CLASSES[idx] ?? PROFICIENCY_CLASSES[0]!;
}

function ProficiencyBadge({ value }: { value: number }) {
  return (
    <span className={`inline-block px-2 py-0.5 text-xs rounded font-medium border ${proficiencyClasses(value)}`}>
      {value} {PROFICIENCY_LABELS[value] ?? ""}
    </span>
  );
}

function GapIndicator({ gap }: { gap: number }) {
  if (gap > 0) {
    return (
      <span className="inline-flex items-center gap-1 px-2 py-0.5 text-xs rounded font-semibold bg-red-100 text-red-700 border border-red-200 dark:bg-red-900/40 dark:text-red-300 dark:border-red-700">
        -{gap} shortage
      </span>
    );
  }
  if (gap < 0) {
    return (
      <span className="inline-flex items-center gap-1 px-2 py-0.5 text-xs rounded font-semibold bg-green-100 text-green-700 border border-green-200 dark:bg-green-900/40 dark:text-green-300 dark:border-green-700">
        +{Math.abs(gap)} surplus
      </span>
    );
  }
  return (
    <span className="inline-flex items-center gap-1 px-2 py-0.5 text-xs rounded font-semibold bg-gray-100 text-gray-500 border border-gray-200 dark:bg-gray-700 dark:text-gray-300 dark:border-gray-600">
      balanced
    </span>
  );
}

function formatDate(iso: string | null): string {
  if (!iso) return "Not within 30d";
  const d = new Date(iso);
  return d.toLocaleDateString("en-GB", { day: "2-digit", month: "short", year: "numeric" });
}

export function SkillMarketplace() {
  const [searchSkill, setSearchSkill] = useState("");
  const [minProficiency, setMinProficiency] = useState(1);
  const [availableOnly, setAvailableOnly] = useState(false);

  const debouncedSearch = useDebounce(searchSkill, 300);

  const { data, isLoading, error } = trpc.resource.getSkillMarketplace.useQuery(
    {
      searchSkill: debouncedSearch || undefined,
      minProficiency,
      availableOnly,
    },
    { staleTime: 30_000 },
  );

  const {
    sorted: sortedSearch,
    sortField: searchSortField,
    sortDir: searchSortDir,
    toggle: searchToggle,
  } = useTableSort(data?.searchResults ?? []);

  const gapData = useMemo(() => data?.gapData ?? [], [data?.gapData]);
  const {
    sorted: sortedGap,
    sortField: gapSortField,
    sortDir: gapSortDir,
    toggle: gapToggle,
  } = useTableSort(gapData);

  if (isLoading) {
    return (
      <div className="p-6 space-y-4">
        <div className="h-8 shimmer-skeleton rounded w-64" />
        <div className="h-16 shimmer-skeleton rounded-xl" />
        <div className="h-64 shimmer-skeleton rounded-xl" />
        <div className="h-80 shimmer-skeleton rounded-xl" />
      </div>
    );
  }

  if (error) {
    return (
      <div className="p-6">
        <div className="bg-red-50 border border-red-200 rounded-xl p-4 text-sm text-red-700 dark:bg-red-900/20 dark:border-red-800 dark:text-red-300">
          {error.message}
        </div>
      </div>
    );
  }

  return (
    <div className="p-6 pb-24 space-y-6">
      {/* Header */}
      <div>
        <h1 className="text-2xl font-bold text-gray-900 dark:text-gray-100">Skill Marketplace</h1>
        <p className="text-sm text-gray-500 dark:text-gray-400 mt-1">
          {data?.totalResources ?? 0} active resources &middot; Search skills, identify gaps, plan capacity
        </p>
      </div>

      {/* ── Section 1: Skill Search ──────────────────────────────────────────── */}
      <div className="bg-white dark:bg-slate-900 rounded-xl border border-gray-200 dark:border-slate-700 p-5 space-y-4">
        <h2 className="text-sm font-semibold text-gray-800 dark:text-gray-200">Skill Search</h2>

        <div className="flex flex-wrap gap-3 items-center">
          {/* Search input */}
          <div className="relative">
            <svg
              className="absolute left-2.5 top-1/2 -translate-y-1/2 w-4 h-4 text-gray-400 pointer-events-none"
              fill="none"
              viewBox="0 0 24 24"
              stroke="currentColor"
            >
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 21l-4.35-4.35M17 11A6 6 0 1 1 5 11a6 6 0 0 1 12 0z" />
            </svg>
            <input
              type="text"
              placeholder="Search by skill name..."
              value={searchSkill}
              onChange={(e) => setSearchSkill(e.target.value)}
              className="pl-8 pr-3 py-2 border border-gray-300 dark:border-slate-600 rounded-lg text-sm bg-white dark:bg-slate-800 dark:text-gray-200 focus:outline-none focus:ring-2 focus:ring-brand-500 w-60"
            />
          </div>

          {/* Min proficiency */}
          <div className="flex items-center gap-1.5">
            <span className="text-xs text-gray-500 dark:text-gray-400">Min. proficiency:</span>
            <div className="flex rounded-lg overflow-hidden border border-gray-200 dark:border-slate-600">
              {[1, 2, 3, 4, 5].map((lvl) => (
                <button
                  key={lvl}
                  type="button"
                  title={PROFICIENCY_LABELS[lvl]}
                  onClick={() => setMinProficiency(lvl)}
                  className={`px-2 py-1 text-xs font-medium transition-colors ${
                    minProficiency === lvl
                      ? "bg-brand-600 text-white"
                      : "bg-white dark:bg-slate-800 text-gray-500 dark:text-gray-400 hover:bg-gray-50 dark:hover:bg-slate-700"
                  }`}
                >
                  {lvl}
                </button>
              ))}
            </div>
          </div>

          {/* Available only */}
          <label className="flex items-center gap-2 text-sm text-gray-600 dark:text-gray-300 cursor-pointer select-none">
            <input
              type="checkbox"
              checked={availableOnly}
              onChange={(e) => setAvailableOnly(e.target.checked)}
              className="rounded border-gray-300 text-brand-600 focus:ring-brand-500"
            />
            Available in next 30 days
          </label>
        </div>

        {/* Search results table */}
        {debouncedSearch && debouncedSearch.trim().length > 0 && (
          <div className="border-t border-gray-100 dark:border-slate-700 pt-4">
            {sortedSearch.length === 0 ? (
              <p className="text-sm text-gray-400 italic">
                No resources found with &quot;{debouncedSearch}&quot; at proficiency {minProficiency}+.
              </p>
            ) : (
              <>
                <p className="text-xs text-gray-500 dark:text-gray-400 mb-3">
                  {sortedSearch.length} resource{sortedSearch.length !== 1 ? "s" : ""} found
                </p>
                <div className="overflow-x-auto">
                  <table className="w-full text-sm">
                    <thead className="bg-gray-50 dark:bg-slate-800 border-b border-gray-200 dark:border-slate-700">
                      <tr>
                        <SortableColumnHeader label="Resource" field="displayName" sortField={searchSortField} sortDir={searchSortDir} onSort={searchToggle} />
                        <SortableColumnHeader label="Chapter" field="chapter" sortField={searchSortField} sortDir={searchSortDir} onSort={searchToggle} />
                        <SortableColumnHeader label="Skill" field="skillName" sortField={searchSortField} sortDir={searchSortDir} onSort={searchToggle} />
                        <SortableColumnHeader label="Proficiency" field="skillProficiency" sortField={searchSortField} sortDir={searchSortDir} onSort={searchToggle} align="center" />
                        <SortableColumnHeader label="Utilization" field="utilizationPercent" sortField={searchSortField} sortDir={searchSortDir} onSort={searchToggle} align="right" />
                        <SortableColumnHeader label="Available From" field="availableFrom" sortField={searchSortField} sortDir={searchSortDir} onSort={searchToggle} />
                      </tr>
                    </thead>
                    <tbody className="divide-y divide-gray-100 dark:divide-slate-700">
                      {sortedSearch.map((r) => (
                        <tr key={r.id} className="hover:bg-gray-50 dark:hover:bg-slate-800/50">
                          <td className="px-4 py-2.5">
                            <Link
                              href={`/resources/${r.id}`}
                              className="font-medium text-gray-900 dark:text-gray-100 hover:text-brand-600 transition-colors"
                            >
                              {r.displayName}
                            </Link>
                          </td>
                          <td className="px-4 py-2.5 text-gray-500 dark:text-gray-400">{r.chapter ?? "---"}</td>
                          <td className="px-4 py-2.5 text-gray-700 dark:text-gray-300">{r.skillName}</td>
                          <td className="px-4 py-2.5 text-center">
                            <ProficiencyBadge value={r.skillProficiency} />
                          </td>
                          <td className="px-4 py-2.5 text-right">
                            <span className={`text-sm font-medium ${
                              r.utilizationPercent >= 90
                                ? "text-red-600 dark:text-red-400"
                                : r.utilizationPercent >= 70
                                  ? "text-amber-600 dark:text-amber-400"
                                  : "text-green-600 dark:text-green-400"
                            }`}>
                              {r.utilizationPercent}%
                            </span>
                          </td>
                          <td className="px-4 py-2.5 text-gray-500 dark:text-gray-400 text-sm">
                            {formatDate(r.availableFrom)}
                          </td>
                        </tr>
                      ))}
                    </tbody>
                  </table>
                </div>
              </>
            )}
          </div>
        )}
      </div>

      {/* ── Section 2: Skill Gap Heat Map ────────────────────────────────────── */}
      <div className="bg-white dark:bg-slate-900 rounded-xl border border-gray-200 dark:border-slate-700 p-5 space-y-4">
        <div>
          <h2 className="text-sm font-semibold text-gray-800 dark:text-gray-200">Skill Gap Analysis</h2>
          <p className="text-xs text-gray-400 dark:text-gray-500 mt-1">
            Supply = resources with proficiency 3+ &middot; Demand = unfilled demand requirements &middot; Sorted by largest gap
          </p>
        </div>

        {sortedGap.length === 0 ? (
          <p className="text-sm text-gray-400 italic py-4">
            No gap data available. Gaps appear when projects have unfilled demand requirements with required skills.
          </p>
        ) : (
          <div className="overflow-x-auto">
            <table className="w-full text-sm">
              <thead className="bg-gray-50 dark:bg-slate-800 border-b border-gray-200 dark:border-slate-700">
                <tr>
                  <SortableColumnHeader label="Skill" field="skill" sortField={gapSortField} sortDir={gapSortDir} onSort={gapToggle} />
                  <SortableColumnHeader label="Supply" field="supply" sortField={gapSortField} sortDir={gapSortDir} onSort={gapToggle} align="right" />
                  <SortableColumnHeader label="Demand" field="demand" sortField={gapSortField} sortDir={gapSortDir} onSort={gapToggle} align="right" />
                  <SortableColumnHeader label="Gap" field="gap" sortField={gapSortField} sortDir={gapSortDir} onSort={gapToggle} align="center" />
                  <th className="px-4 py-3 text-left text-xs font-medium text-gray-500 dark:text-gray-400 uppercase tracking-wider">Visual</th>
                </tr>
              </thead>
              <tbody className="divide-y divide-gray-100 dark:divide-slate-700">
                {sortedGap.map((row) => {
                  const maxBar = Math.max(row.supply, row.demand, 1);
                  return (
                    <tr key={row.skill} className="hover:bg-gray-50 dark:hover:bg-slate-800/50">
                      <td className="px-4 py-2.5 font-medium text-gray-900 dark:text-gray-100">
                        <button
                          type="button"
                          className="hover:text-brand-600 transition-colors text-left"
                          onClick={() => {
                            setSearchSkill(row.skill);
                            setMinProficiency(3);
                            window.scrollTo({ top: 0, behavior: "smooth" });
                          }}
                          title={`Search for "${row.skill}"`}
                        >
                          {row.skill}
                        </button>
                      </td>
                      <td className="px-4 py-2.5 text-right text-gray-700 dark:text-gray-300">{row.supply}</td>
                      <td className="px-4 py-2.5 text-right text-gray-700 dark:text-gray-300">{row.demand}</td>
                      <td className="px-4 py-2.5 text-center">
                        <GapIndicator gap={row.gap} />
                      </td>
                      <td className="px-4 py-2.5 w-48">
                        <div className="flex items-center gap-1 h-4">
                          <div
                            className="h-3 rounded-sm bg-green-400 dark:bg-green-500 transition-all"
                            style={{ width: `${(row.supply / maxBar) * 100}%`, minWidth: row.supply > 0 ? 4 : 0 }}
                            title={`Supply: ${row.supply}`}
                          />
                          <div
                            className="h-3 rounded-sm bg-red-400 dark:bg-red-500 transition-all"
                            style={{ width: `${(row.demand / maxBar) * 100}%`, minWidth: row.demand > 0 ? 4 : 0 }}
                            title={`Demand: ${row.demand}`}
                          />
                        </div>
                      </td>
                    </tr>
                  );
                })}
              </tbody>
            </table>
            <div className="flex items-center gap-4 mt-3 px-4">
              <div className="flex items-center gap-1.5 text-xs text-gray-500 dark:text-gray-400">
                <span className="w-3 h-3 rounded-sm bg-green-400 dark:bg-green-500 inline-block" /> Supply (prof. 3+)
              </div>
              <div className="flex items-center gap-1.5 text-xs text-gray-500 dark:text-gray-400">
                <span className="w-3 h-3 rounded-sm bg-red-400 dark:bg-red-500 inline-block" /> Demand (unfilled)
              </div>
            </div>
          </div>
        )}
      </div>

      {/* ── Section 3: Skill Distribution ────────────────────────────────────── */}
      {(data?.distribution ?? []).length > 0 && (
        <div className="bg-white dark:bg-slate-900 rounded-xl border border-gray-200 dark:border-slate-700 p-5">
          <h2 className="text-sm font-semibold text-gray-800 dark:text-gray-200 mb-4">
            Top 20 Skills by Resource Count
          </h2>
          <SkillDistributionChart data={data?.distribution ?? []} />
          <p className="text-xs text-gray-400 dark:text-gray-500 mt-2">
            Bar color = average proficiency (light to dark = low to high)
          </p>
        </div>
      )}
    </div>
  );
}