"use client";

import { useState, useMemo, useCallback } from "react";
import { keepPreviousData } from "@tanstack/react-query";
import { trpc } from "~/lib/trpc/client.js";
import { clsx } from "clsx";

// ─── Types ──────────────────────────────────────────────────────────────────

type EntityType = "resource" | "project" | "assignment";
type FilterOp = "eq" | "neq" | "gt" | "lt" | "gte" | "lte" | "contains" | "in";

interface FilterRow {
  id: string;
  field: string;
  op: FilterOp;
  value: string;
}

const ENTITY_OPTIONS: { value: EntityType; label: string }[] = [
  { value: "resource", label: "Resources" },
  { value: "project", label: "Projects" },
  { value: "assignment", label: "Assignments" },
];

const OPERATOR_OPTIONS: { value: FilterOp; label: string }[] = [
  { value: "eq", label: "equals" },
  { value: "neq", label: "not equals" },
  { value: "gt", label: "greater than" },
  { value: "lt", label: "less than" },
  { value: "gte", label: ">= (gte)" },
  { value: "lte", label: "<= (lte)" },
  { value: "contains", label: "contains" },
  { value: "in", label: "in (comma-sep)" },
];

const PAGE_SIZE = 50;

function generateId(): string {
  return Math.random().toString(36).slice(2, 10);
}

// ─── Component ──────────────────────────────────────────────────────────────

export function ReportBuilder() {
  // Config state
  const [entity, setEntity] = useState<EntityType>("resource");
  const [selectedColumns, setSelectedColumns] = useState<Set<string>>(new Set());
  const [filters, setFilters] = useState<FilterRow[]>([]);
  const [groupBy, setGroupBy] = useState<string>("");
  const [sortBy, setSortBy] = useState<string>("");
  const [sortDir, setSortDir] = useState<"asc" | "desc">("asc");
  const [page, setPage] = useState(0);
  const [runQuery, setRunQuery] = useState(false);

  // Fetch available columns when entity changes
  const columnsQuery = trpc.report.getAvailableColumns.useQuery(
    { entity },
    { placeholderData: keepPreviousData },
  );

  const availableColumns = columnsQuery.data ?? [];

  // Scalar columns (for filter/sort/group — only non-relation columns)
  const scalarColumns = useMemo(
    () => availableColumns.filter((c) => !c.key.includes(".")),
    [availableColumns],
  );

  // Build query input
  const queryInput = useMemo(() => {
    if (!runQuery || selectedColumns.size === 0) return null;
    return {
      entity,
      columns: Array.from(selectedColumns),
      filters: filters
        .filter((f) => f.field && f.value)
        .map(({ field, op, value }) => ({ field, op, value })),
      ...(groupBy ? { groupBy } : {}),
      ...(sortBy ? { sortBy, sortDir } : {}),
      limit: PAGE_SIZE,
      offset: page * PAGE_SIZE,
    };
  }, [runQuery, entity, selectedColumns, filters, groupBy, sortBy, sortDir, page]);

  // Fetch report data
  const reportQuery = trpc.report.getReportData.useQuery(
    queryInput!,
    { enabled: queryInput !== null, placeholderData: keepPreviousData },
  );

  const exportMutation = trpc.report.exportReport.useMutation();

  // ─── Handlers ───────────────────────────────────────────────────────────

  const handleEntityChange = useCallback((newEntity: EntityType) => {
    setEntity(newEntity);
    setSelectedColumns(new Set());
    setFilters([]);
    setGroupBy("");
    setSortBy("");
    setRunQuery(false);
    setPage(0);
  }, []);

  const toggleColumn = useCallback((key: string) => {
    setSelectedColumns((prev) => {
      const next = new Set(prev);
      if (next.has(key)) {
        next.delete(key);
      } else {
        next.add(key);
      }
      return next;
    });
  }, []);

  const selectAllColumns = useCallback(() => {
    setSelectedColumns(new Set(availableColumns.map((c) => c.key)));
  }, [availableColumns]);

  const clearAllColumns = useCallback(() => {
    setSelectedColumns(new Set());
  }, []);

  const addFilter = useCallback(() => {
    const firstField = scalarColumns[0]?.key ?? "";
    setFilters((prev) => [...prev, { id: generateId(), field: firstField, op: "eq", value: "" }]);
  }, [scalarColumns]);

  const updateFilter = useCallback((id: string, patch: Partial<FilterRow>) => {
    setFilters((prev) => prev.map((f) => (f.id === id ? { ...f, ...patch } : f)));
  }, []);

  const removeFilter = useCallback((id: string) => {
    setFilters((prev) => prev.filter((f) => f.id !== id));
  }, []);

  const handleRun = useCallback(() => {
    setPage(0);
    setRunQuery(true);
  }, []);

  const handleSort = useCallback((column: string) => {
    if (!column.includes(".")) {
      if (sortBy === column) {
        setSortDir((prev) => (prev === "asc" ? "desc" : "asc"));
      } else {
        setSortBy(column);
        setSortDir("asc");
      }
      // Re-run with new sort
      setRunQuery(true);
    }
  }, [sortBy]);

  const handleExport = useCallback(async () => {
    if (selectedColumns.size === 0) return;
    try {
      const result = await exportMutation.mutateAsync({
        entity,
        columns: Array.from(selectedColumns),
        filters: filters
          .filter((f) => f.field && f.value)
          .map(({ field, op, value }) => ({ field, op, value })),
        ...(groupBy ? { groupBy } : {}),
        ...(sortBy ? { sortBy, sortDir } : {}),
        limit: 5000,
      });

      // Download CSV
      const blob = new Blob([result.csv], { type: "text/csv;charset=utf-8;" });
      const url = URL.createObjectURL(blob);
      const link = document.createElement("a");
      link.href = url;
      link.download = `report-${entity}-${new Date().toISOString().slice(0, 10)}.csv`;
      link.click();
      URL.revokeObjectURL(url);
    } catch {
      // Error handled by tRPC
    }
  }, [entity, selectedColumns, filters, groupBy, sortBy, sortDir, exportMutation]);

  // ─── Derived ──────────────────────────────────────────────────────────

  const rows = reportQuery.data?.rows ?? [];
  const totalCount = reportQuery.data?.totalCount ?? 0;
  const outputColumns = reportQuery.data?.columns ?? [];
  const totalPages = Math.ceil(totalCount / PAGE_SIZE);
  const isLoading = reportQuery.isFetching;

  // Column label lookup
  const columnLabelMap = useMemo(() => {
    const map = new Map<string, string>();
    for (const col of availableColumns) {
      map.set(col.key, col.label);
    }
    return map;
  }, [availableColumns]);

  // ─── Render ───────────────────────────────────────────────────────────

  return (
    <div className="mx-auto max-w-[1600px] space-y-6 p-6">
      {/* Header */}
      <div>
        <h1 className="text-2xl font-bold text-gray-900 dark:text-gray-50">Report Builder</h1>
        <p className="mt-1 text-sm text-gray-500 dark:text-gray-400">
          Build custom reports by selecting an entity, columns, and filters.
        </p>
      </div>

      {/* Config Panel */}
      <div className="space-y-5 rounded-2xl border border-gray-200 bg-white p-6 shadow-sm dark:border-slate-800 dark:bg-slate-950">
        {/* Entity Selector */}
        <div>
          <label className="mb-2 block text-sm font-medium text-gray-700 dark:text-gray-300">
            Entity
          </label>
          <div className="flex gap-3">
            {ENTITY_OPTIONS.map((opt) => (
              <button
                key={opt.value}
                type="button"
                onClick={() => handleEntityChange(opt.value)}
                className={clsx(
                  "rounded-xl px-4 py-2 text-sm font-medium transition-colors",
                  entity === opt.value
                    ? "bg-brand-600 text-white shadow-sm"
                    : "bg-gray-100 text-gray-700 hover:bg-gray-200 dark:bg-slate-800 dark:text-gray-300 dark:hover:bg-slate-700",
                )}
              >
                {opt.label}
              </button>
            ))}
          </div>
        </div>

        {/* Column Picker */}
        <div>
          <div className="mb-2 flex items-center justify-between">
            <label className="text-sm font-medium text-gray-700 dark:text-gray-300">
              Columns ({selectedColumns.size} selected)
            </label>
            <div className="flex gap-2">
              <button
                type="button"
                onClick={selectAllColumns}
                className="text-xs font-medium text-brand-600 hover:text-brand-700 dark:text-brand-400"
              >
                Select all
              </button>
              <span className="text-xs text-gray-300 dark:text-gray-600">|</span>
              <button
                type="button"
                onClick={clearAllColumns}
                className="text-xs font-medium text-gray-500 hover:text-gray-700 dark:text-gray-400 dark:hover:text-gray-200"
              >
                Clear
              </button>
            </div>
          </div>
          {columnsQuery.isLoading ? (
            <div className="py-3 text-sm text-gray-400">Loading columns...</div>
          ) : (
            <div className="grid grid-cols-2 gap-x-4 gap-y-1 sm:grid-cols-3 lg:grid-cols-4 xl:grid-cols-5">
              {availableColumns.map((col) => (
                <label
                  key={col.key}
                  className="flex cursor-pointer items-center gap-2 rounded-lg px-2 py-1.5 text-sm transition-colors hover:bg-gray-50 dark:hover:bg-slate-900"
                >
                  <input
                    type="checkbox"
                    checked={selectedColumns.has(col.key)}
                    onChange={() => toggleColumn(col.key)}
                    className="h-3.5 w-3.5 rounded border-gray-300 text-brand-600 focus:ring-brand-500 dark:border-slate-600"
                  />
                  <span className="text-gray-700 dark:text-gray-300">{col.label}</span>
                  <span className="ml-auto text-[10px] uppercase tracking-wider text-gray-400 dark:text-gray-600">
                    {col.dataType}
                  </span>
                </label>
              ))}
            </div>
          )}
        </div>

        {/* Filter Builder */}
        <div>
          <div className="mb-2 flex items-center justify-between">
            <label className="text-sm font-medium text-gray-700 dark:text-gray-300">
              Filters
            </label>
            <button
              type="button"
              onClick={addFilter}
              className="flex items-center gap-1 text-xs font-medium text-brand-600 hover:text-brand-700 dark:text-brand-400"
            >
              <svg className="h-3.5 w-3.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 4v16m8-8H4" />
              </svg>
              Add filter
            </button>
          </div>
          {filters.length === 0 ? (
            <p className="text-sm text-gray-400 dark:text-gray-500">No filters applied.</p>
          ) : (
            <div className="space-y-2">
              {filters.map((filter) => (
                <div key={filter.id} className="flex items-center gap-2">
                  {/* Field */}
                  <select
                    value={filter.field}
                    onChange={(e) => updateFilter(filter.id, { field: e.target.value })}
                    className="w-44 rounded-lg border border-gray-300 bg-white px-2.5 py-1.5 text-sm text-gray-700 focus:border-brand-500 focus:ring-brand-500 dark:border-slate-700 dark:bg-slate-900 dark:text-gray-300"
                  >
                    {scalarColumns.map((col) => (
                      <option key={col.key} value={col.key}>{col.label}</option>
                    ))}
                  </select>

                  {/* Operator */}
                  <select
                    value={filter.op}
                    onChange={(e) => updateFilter(filter.id, { op: e.target.value as FilterOp })}
                    className="w-36 rounded-lg border border-gray-300 bg-white px-2.5 py-1.5 text-sm text-gray-700 focus:border-brand-500 focus:ring-brand-500 dark:border-slate-700 dark:bg-slate-900 dark:text-gray-300"
                  >
                    {OPERATOR_OPTIONS.map((op) => (
                      <option key={op.value} value={op.value}>{op.label}</option>
                    ))}
                  </select>

                  {/* Value */}
                  <input
                    type="text"
                    value={filter.value}
                    onChange={(e) => updateFilter(filter.id, { value: e.target.value })}
                    placeholder="Value..."
                    className="min-w-0 flex-1 rounded-lg border border-gray-300 bg-white px-2.5 py-1.5 text-sm text-gray-700 placeholder:text-gray-400 focus:border-brand-500 focus:ring-brand-500 dark:border-slate-700 dark:bg-slate-900 dark:text-gray-300 dark:placeholder:text-gray-600"
                  />

                  {/* Remove */}
                  <button
                    type="button"
                    onClick={() => removeFilter(filter.id)}
                    className="flex h-8 w-8 shrink-0 items-center justify-center rounded-lg text-gray-400 transition-colors hover:bg-red-50 hover:text-red-600 dark:hover:bg-red-950 dark:hover:text-red-400"
                    title="Remove filter"
                  >
                    <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                      <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M6 18L18 6M6 6l12 12" />
                    </svg>
                  </button>
                </div>
              ))}
            </div>
          )}
        </div>

        {/* Sort & Group */}
        <div className="flex flex-wrap gap-4">
          <div className="min-w-[160px]">
            <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">
              Group by
            </label>
            <select
              value={groupBy}
              onChange={(e) => setGroupBy(e.target.value)}
              className="w-full rounded-lg border border-gray-300 bg-white px-2.5 py-1.5 text-sm text-gray-700 focus:border-brand-500 focus:ring-brand-500 dark:border-slate-700 dark:bg-slate-900 dark:text-gray-300"
            >
              <option value="">None</option>
              {scalarColumns.map((col) => (
                <option key={col.key} value={col.key}>{col.label}</option>
              ))}
            </select>
          </div>
          <div className="min-w-[160px]">
            <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">
              Sort by
            </label>
            <select
              value={sortBy}
              onChange={(e) => setSortBy(e.target.value)}
              className="w-full rounded-lg border border-gray-300 bg-white px-2.5 py-1.5 text-sm text-gray-700 focus:border-brand-500 focus:ring-brand-500 dark:border-slate-700 dark:bg-slate-900 dark:text-gray-300"
            >
              <option value="">Default</option>
              {scalarColumns.map((col) => (
                <option key={col.key} value={col.key}>{col.label}</option>
              ))}
            </select>
          </div>
          <div className="min-w-[120px]">
            <label className="mb-1 block text-sm font-medium text-gray-700 dark:text-gray-300">
              Direction
            </label>
            <select
              value={sortDir}
              onChange={(e) => setSortDir(e.target.value as "asc" | "desc")}
              className="w-full rounded-lg border border-gray-300 bg-white px-2.5 py-1.5 text-sm text-gray-700 focus:border-brand-500 focus:ring-brand-500 dark:border-slate-700 dark:bg-slate-900 dark:text-gray-300"
            >
              <option value="asc">Ascending</option>
              <option value="desc">Descending</option>
            </select>
          </div>
        </div>

        {/* Run button */}
        <div className="flex items-center gap-3">
          <button
            type="button"
            onClick={handleRun}
            disabled={selectedColumns.size === 0}
            className="inline-flex items-center gap-2 rounded-xl bg-brand-600 px-5 py-2.5 text-sm font-medium text-white shadow-sm transition-colors hover:bg-brand-700 disabled:cursor-not-allowed disabled:opacity-50"
          >
            <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M14.752 11.168l-3.197-2.132A1 1 0 0010 9.87v4.263a1 1 0 001.555.832l3.197-2.132a1 1 0 000-1.664z" />
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M21 12a9 9 0 11-18 0 9 9 0 0118 0z" />
            </svg>
            Run Report
          </button>
          {selectedColumns.size === 0 && (
            <span className="text-sm text-gray-400 dark:text-gray-500">Select at least one column</span>
          )}
        </div>
      </div>

      {/* Results */}
      {runQuery && (
        <div className="rounded-2xl border border-gray-200 bg-white shadow-sm dark:border-slate-800 dark:bg-slate-950">
          {/* Results Header */}
          <div className="flex items-center justify-between border-b border-gray-200 px-6 py-4 dark:border-slate-800">
            <div className="flex items-center gap-3">
              <h2 className="text-lg font-semibold text-gray-900 dark:text-gray-50">Results</h2>
              {!isLoading && (
                <span className="rounded-full bg-gray-100 px-2.5 py-0.5 text-xs font-medium text-gray-600 dark:bg-slate-800 dark:text-gray-400">
                  {totalCount.toLocaleString()} row{totalCount !== 1 ? "s" : ""}
                </span>
              )}
            </div>
            <button
              type="button"
              onClick={() => void handleExport()}
              disabled={exportMutation.isPending || totalCount === 0}
              className="inline-flex items-center gap-1.5 rounded-lg border border-gray-300 bg-white px-3 py-1.5 text-sm font-medium text-gray-700 shadow-sm transition-colors hover:bg-gray-50 disabled:cursor-not-allowed disabled:opacity-50 dark:border-slate-700 dark:bg-slate-900 dark:text-gray-300 dark:hover:bg-slate-800"
            >
              <svg className="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M12 10v6m0 0l-3-3m3 3l3-3m2 8H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z" />
              </svg>
              {exportMutation.isPending ? "Exporting..." : "Export CSV"}
            </button>
          </div>

          {/* Table */}
          <div className="overflow-x-auto">
            {isLoading ? (
              <div className="flex items-center justify-center py-16">
                <div className="h-8 w-8 animate-spin rounded-full border-2 border-brand-600 border-t-transparent" />
              </div>
            ) : rows.length === 0 ? (
              <div className="py-16 text-center text-sm text-gray-400 dark:text-gray-500">
                No data found. Try adjusting your filters.
              </div>
            ) : (
              <table className="w-full text-sm">
                <thead>
                  <tr className="border-b border-gray-200 bg-gray-50/80 dark:border-slate-800 dark:bg-slate-900/50">
                    {outputColumns.map((col) => {
                      const isSortable = !col.includes(".");
                      const isSorted = sortBy === col;
                      return (
                        <th
                          key={col}
                          onClick={isSortable ? () => handleSort(col) : undefined}
                          className={clsx(
                            "whitespace-nowrap px-4 py-3 text-left text-xs font-semibold uppercase tracking-wider text-gray-500 dark:text-gray-400",
                            isSortable && "cursor-pointer select-none hover:text-gray-700 dark:hover:text-gray-200",
                          )}
                        >
                          <span className="inline-flex items-center gap-1">
                            {columnLabelMap.get(col) ?? col}
                            {isSorted && (
                              <svg className={clsx("h-3 w-3", sortDir === "desc" && "rotate-180")} fill="none" stroke="currentColor" viewBox="0 0 24 24">
                                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M5 15l7-7 7 7" />
                              </svg>
                            )}
                          </span>
                        </th>
                      );
                    })}
                  </tr>
                </thead>
                <tbody className="divide-y divide-gray-100 dark:divide-slate-800/60">
                  {rows.map((row, idx) => (
                    <tr
                      key={(row.id as string) ?? idx}
                      className="transition-colors hover:bg-gray-50/60 dark:hover:bg-slate-900/40"
                    >
                      {outputColumns.map((col) => (
                        <td
                          key={col}
                          className="whitespace-nowrap px-4 py-2.5 text-gray-700 dark:text-gray-300"
                        >
                          {formatCellValue(row[col])}
                        </td>
                      ))}
                    </tr>
                  ))}
                </tbody>
              </table>
            )}
          </div>

          {/* Pagination */}
          {totalPages > 1 && (
            <div className="flex items-center justify-between border-t border-gray-200 px-6 py-3 dark:border-slate-800">
              <span className="text-sm text-gray-500 dark:text-gray-400">
                Page {page + 1} of {totalPages}
              </span>
              <div className="flex gap-2">
                <button
                  type="button"
                  onClick={() => setPage((p) => Math.max(0, p - 1))}
                  disabled={page === 0}
                  className="rounded-lg border border-gray-300 px-3 py-1.5 text-sm font-medium text-gray-700 transition-colors hover:bg-gray-50 disabled:cursor-not-allowed disabled:opacity-50 dark:border-slate-700 dark:text-gray-300 dark:hover:bg-slate-800"
                >
                  Previous
                </button>
                <button
                  type="button"
                  onClick={() => setPage((p) => Math.min(totalPages - 1, p + 1))}
                  disabled={page >= totalPages - 1}
                  className="rounded-lg border border-gray-300 px-3 py-1.5 text-sm font-medium text-gray-700 transition-colors hover:bg-gray-50 disabled:cursor-not-allowed disabled:opacity-50 dark:border-slate-700 dark:text-gray-300 dark:hover:bg-slate-800"
                >
                  Next
                </button>
              </div>
            </div>
          )}
        </div>
      )}
    </div>
  );
}

// ─── Helpers ────────────────────────────────────────────────────────────────

function formatCellValue(value: unknown): string {
  if (value === null || value === undefined) return "--";
  if (typeof value === "boolean") return value ? "Yes" : "No";
  if (typeof value === "string") {
    // ISO date detection
    if (/^\d{4}-\d{2}-\d{2}T/.test(value)) {
      return new Date(value).toLocaleDateString("de-DE", {
        year: "numeric",
        month: "2-digit",
        day: "2-digit",
      });
    }
    return value;
  }
  if (typeof value === "number") {
    return value.toLocaleString("de-DE");
  }
  return String(value);
}