//=============================================
// File: Statistiche.tsx
// Componente per la gestione delle statistiche 
// da parte dei Referenti Academy
// @author: "villari.andrea@libero.it"
// @version: "1.0.0 2026-07-14"
//=============================================

import { useCallback, useEffect, useMemo, useState } from "react";
import { AlertCircle, BarChart3, Filter } from "lucide-react";
import { getCorsi, getStatisticheAcademy, getUtenti } from "@/api/client";
import { Alert, AlertDescription } from "@/components/ui/alert";
import { Badge } from "@/components/ui/badge";
import {
  Card,
  CardContent,
  CardDescription,
  CardHeader,
  CardTitle,
} from "@/components/ui/card";
import { Input } from "@/components/ui/input";
import { Label } from "@/components/ui/label";
import {
  Select,
  SelectContent,
  SelectItem,
  SelectTrigger,
  SelectValue,
} from "@/components/ui/select";
import { Skeleton } from "@/components/ui/skeleton";
import {
  Table,
  TableBody,
  TableCell,
  TableHead,
  TableHeader,
  TableRow,
} from "@/components/ui/table";
import type { StatisticaAcademy, Utente } from "@/types";

const ALL_VALUE = "__all__";

function currentMonth(): string {
  return new Date().toISOString().slice(0, 7);
}

function formatMeseIt(mese: string): string {
  const [year, month] = mese.split("-");
  if (!year || !month) return mese;
  const date = new Date(Number(year), Number(month) - 1, 1);
  return date.toLocaleDateString("it-IT", { month: "long", year: "numeric" });
}

function dipendenteLabel(utente: Pick<Utente, "nome" | "cognome">) {
  return `${utente.cognome} ${utente.nome}`;
}

function TableSkeleton() {
  return (
    <div className="space-y-2">
      {Array.from({ length: 5 }).map((_, index) => (
        <Skeleton key={index} className="h-12 w-full" />
      ))}
    </div>
  );
}

function SummaryCard({
  title,
  value,
  description,
}: {
  title: string;
  value: string | number;
  description: string;
}) {
  return (
    <Card>
      <CardHeader className="pb-2">
        <CardTitle className="text-sm font-medium">{title}</CardTitle>
      </CardHeader>
      <CardContent>
        <p className="text-2xl font-semibold">{value}</p>
        <p className="text-xs text-muted-foreground">{description}</p>
      </CardContent>
    </Card>
  );
}

export default function Statistiche() {
  const [statistiche, setStatistiche] = useState<StatisticaAcademy[]>([]);
  const [categorie, setCategorie] = useState<string[]>([]);
  const [dipendenti, setDipendenti] = useState<Utente[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [meseFilter, setMeseFilter] = useState(currentMonth());
  const [categoriaFilter, setCategoriaFilter] = useState(ALL_VALUE);
  const [dipendenteFilter, setDipendenteFilter] = useState(ALL_VALUE);

  useEffect(() => {
    Promise.all([getCorsi(), getUtenti({ ruolo: "Dipendente" })])
      .then(([corsi, dipendentiData]) => {
        const values = new Set(corsi.map((c) => c.categoria));
        setCategorie(Array.from(values).sort());
        setDipendenti(dipendentiData);
      })
      .catch(() => {
        /* i filtri possono restare vuoti */
      });
  }, []);

  const loadStatistiche = useCallback(async () => {
    setLoading(true);
    setError(null);
    try {
      const data = await getStatisticheAcademy({
        mese: meseFilter || undefined,
        categoria: categoriaFilter === ALL_VALUE ? undefined : categoriaFilter,
        dipendenteId:
          dipendenteFilter === ALL_VALUE
            ? undefined
            : Number(dipendenteFilter),
      });
      setStatistiche(data);
    } catch (err) {
      setError(err instanceof Error ? err.message : "Errore nel caricamento");
    } finally {
      setLoading(false);
    }
  }, [meseFilter, categoriaFilter, dipendenteFilter]);

  useEffect(() => {
    loadStatistiche();
  }, [loadStatistiche]);

  const totali = useMemo(() => {
    const assegnazioni = statistiche.reduce(
      (sum, row) => sum + row.numeroAssegnazioni,
      0
    );
    const completamenti = statistiche.reduce(
      (sum, row) => sum + row.numeroCompletamenti,
      0
    );
    const percentuale =
      assegnazioni === 0
        ? 0
        : Math.round((completamenti / assegnazioni) * 10000) / 100;

    return { assegnazioni, completamenti, percentuale };
  }, [statistiche]);

  const dipendenteSelezionato = dipendenti.find(
    (d) => String(d.id) === dipendenteFilter
  );

  return (
    <div className="space-y-6">
      <div>
        <h1 className="text-2xl font-semibold tracking-tight">Statistiche</h1>
        <p className="text-muted-foreground">
          Riepiloghi formativi aggregati per mese e categoria. Le assegnazioni
          annullate sono escluse dal conteggio.
        </p>
      </div>

      {error && (
        <Alert variant="destructive">
          <AlertCircle />
          <AlertDescription>{error}</AlertDescription>
        </Alert>
      )}

      <Card>
        <CardHeader className="pb-4">
          <CardTitle className="flex items-center gap-2 text-base">
            <Filter className="size-4" />
            Filtri
          </CardTitle>
          <CardDescription>
            Filtra per mese di assegnazione, categoria o dipendente.
          </CardDescription>
        </CardHeader>
        <CardContent className="flex flex-wrap gap-4">
          <div className="space-y-1.5">
            <Label htmlFor="filtro-mese-statistiche">Mese</Label>
            <Input
              id="filtro-mese-statistiche"
              type="month"
              value={meseFilter}
              onChange={(e) => setMeseFilter(e.target.value)}
              className="w-44"
            />
          </div>

          <div className="space-y-1.5">
            <Label htmlFor="filtro-categoria-statistiche">Categoria</Label>
            <Select
              value={categoriaFilter}
              onValueChange={(value) => setCategoriaFilter(value ?? ALL_VALUE)}
            >
              <SelectTrigger id="filtro-categoria-statistiche" className="w-44">
                <SelectValue placeholder="Tutte" />
              </SelectTrigger>
              <SelectContent>
                <SelectItem value={ALL_VALUE}>Tutte le categorie</SelectItem>
                {categorie.map((categoria) => (
                  <SelectItem key={categoria} value={categoria}>
                    {categoria}
                  </SelectItem>
                ))}
              </SelectContent>
            </Select>
          </div>

          <div className="space-y-1.5">
            <Label htmlFor="filtro-dipendente-statistiche">Dipendente</Label>
            <Select
              value={dipendenteFilter}
              onValueChange={(value) => setDipendenteFilter(value ?? ALL_VALUE)}
            >
              <SelectTrigger
                id="filtro-dipendente-statistiche"
                className="w-52"
              >
                <SelectValue placeholder="Tutti" />
              </SelectTrigger>
              <SelectContent>
                <SelectItem value={ALL_VALUE}>Tutti i dipendenti</SelectItem>
                {dipendenti.map((dipendente) => (
                  <SelectItem key={dipendente.id} value={String(dipendente.id)}>
                    {dipendenteLabel(dipendente)}
                  </SelectItem>
                ))}
              </SelectContent>
            </Select>
          </div>
        </CardContent>
      </Card>

      {!loading && statistiche.length > 0 && (
        <div className="grid gap-4 sm:grid-cols-3">
          <SummaryCard
            title="Assegnazioni"
            value={totali.assegnazioni}
            description={
              meseFilter
                ? `Nel mese ${formatMeseIt(meseFilter)}`
                : "Totale nel periodo"
            }
          />
          <SummaryCard
            title="Completamenti"
            value={totali.completamenti}
            description="Corsi conclusi con successo"
          />
          <SummaryCard
            title="Tasso completamento"
            value={`${totali.percentuale}%`}
            description="Media sulle righe filtrate"
          />
        </div>
      )}

      <Card>
        <CardHeader>
          <CardTitle className="flex items-center gap-2 text-base">
            <BarChart3 className="size-4" />
            {loading
              ? "Caricamento..."
              : `${statistiche.length} righe di riepilogo`}
          </CardTitle>
          {meseFilter && (
            <CardDescription>
              Dati per {formatMeseIt(meseFilter)}
              {categoriaFilter !== ALL_VALUE && ` · ${categoriaFilter}`}
              {dipendenteSelezionato &&
                ` · ${dipendenteLabel(dipendenteSelezionato)}`}
            </CardDescription>
          )}
        </CardHeader>
        <CardContent>
          {loading ? (
            <TableSkeleton />
          ) : statistiche.length === 0 ? (
            <p className="text-sm text-muted-foreground">
              Nessun dato disponibile per i filtri selezionati.
            </p>
          ) : (
            <Table>
              <TableHeader>
                <TableRow>
                  <TableHead>Mese</TableHead>
                  <TableHead>Categoria</TableHead>
                  <TableHead className="text-right">Assegnazioni</TableHead>
                  <TableHead className="text-right">Completamenti</TableHead>
                  <TableHead className="text-right">Completamento</TableHead>
                </TableRow>
              </TableHeader>
              <TableBody>
                {statistiche.map((row) => (
                  <TableRow key={`${row.mese}-${row.categoria}`}>
                    <TableCell>{formatMeseIt(row.mese)}</TableCell>
                    <TableCell className="font-medium">{row.categoria}</TableCell>
                    <TableCell className="text-right">
                      {row.numeroAssegnazioni}
                    </TableCell>
                    <TableCell className="text-right">
                      {row.numeroCompletamenti}
                    </TableCell>
                    <TableCell className="text-right">
                      <Badge variant="secondary">
                        {row.percentualeCompletamento}%
                      </Badge>
                    </TableCell>
                  </TableRow>
                ))}
              </TableBody>
            </Table>
          )}
        </CardContent>
      </Card>
    </div>
  );
}