import { useState, useEffect } from 'react';
import { useTranslation } from 'react-i18next';
import { Database, Trash2, RefreshCw, Search, ChevronLeft, ChevronRight, Loader2, FileText, Wand2, CheckCircle2 } from 'lucide-react';
import { api } from '../lib/api';
import { useAuth } from '../lib/auth';
import { useTenant } from '../lib/tenant';
import { useToast } from '../hooks/useToast';
import { logError } from '../lib/logger';

interface KbEntry {
    id: string;
    content: string;
    metadata?: Record<string, unknown>;
    createdAt: string;
}

interface KbResponse {
    entries: KbEntry[];
    total: number;
    page: number;
    limit: number;
}

const PAGE_SIZE = 20;

export default function KnowledgeBasePage() {
    const { t } = useTranslation();
    const toast = useToast();
    const { token } = useAuth();
    const { selectedOrgId } = useTenant();
    const [data, setData] = useState<KbResponse | null>(null);
    const [loading, setLoading] = useState(true);
    const [page, setPage] = useState(1);
    const [search, setSearch] = useState('');
    const [deletingId, setDeletingId] = useState<string | null>(null);
    const [reindexing, setReindexing] = useState(false);
    const [genDescription, setGenDescription] = useState('');
    const [generating, setGenerating] = useState(false);
    const [genResult, setGenResult] = useState<{ faqCount: number; chunksIndexed: number; preview: Array<{ question: string; answer: string }> } | null>(null);

    const fetchEntries = async (p = page) => {
        if (!token || !selectedOrgId) return;
        setLoading(true);
        try {
            const res = await api.get(
                `/v1/organizations/${selectedOrgId}/kb?page=${p}&limit=${PAGE_SIZE}`,
                token
            );
            setData(res);
        } catch (err) {
            logError('[KB] Failed to fetch entries:', err);
        } finally {
            setLoading(false);
        }
    };

    useEffect(() => {
        fetchEntries(1);
        setPage(1);
    }, [token, selectedOrgId]);

    const handleDelete = async (id: string) => {
        if (!token || !selectedOrgId) return;
        if (!confirm(t('knowledge.confirm_delete'))) return;
        setDeletingId(id);
        try {
            await api.delete(`/v1/organizations/${selectedOrgId}/kb/${id}`, token);
            await fetchEntries(page);
        } catch (err: any) {
            logError('[KB] Delete failed:', err);
            toast.error(err?.message ?? t('knowledge.delete_error'));
        } finally {
            setDeletingId(null);
        }
    };

    const handleReindex = async () => {
        if (!token || !selectedOrgId) return;
        setReindexing(true);
        try {
            await api.post(`/v1/organizations/${selectedOrgId}/index-kb`, {}, token);
            toast.success(t('knowledge.reindex_success'));
        } catch (err: any) {
            const msg: string = err?.message ?? '';
            if (msg.toLowerCase().includes('no kb url') || msg.toLowerCase().includes('not configured')) {
                toast.error(t('knowledge.no_kb_url'));
            } else {
                logError('[KB] Re-index failed:', err);
                toast.error(t('knowledge.reindex_error'));
            }
        } finally {
            setReindexing(false);
        }
    };

    const handleGenerate = async () => {
        if (!token || !selectedOrgId || !genDescription.trim()) return;
        setGenerating(true);
        setGenResult(null);
        try {
            const res = await api.post(
                `/v1/organizations/${selectedOrgId}/kb/generate`,
                { description: genDescription },
                token
            );
            setGenResult(res);
            toast.success(t('knowledge.generate_success_count', { count: res.faqCount }));
            await fetchEntries(1);
            setPage(1);
        } catch (err: any) {
            logError('[KB] Generate failed:', err);
            toast.error(err?.message ?? t('knowledge.generate_error'));
        } finally {
            setGenerating(false);
        }
    };

    const handlePageChange = (newPage: number) => {
        setPage(newPage);
        fetchEntries(newPage);
    };

    const filteredEntries = (data?.entries ?? []).filter(e =>
        !search || e.content.toLowerCase().includes(search.toLowerCase())
    );

    const totalPages = data ? Math.ceil(data.total / PAGE_SIZE) : 1;

    return (
        <div className="p-8 max-w-5xl mx-auto">
            <div className="flex items-center justify-between mb-8">
                <div className="flex items-center gap-3">
                    <div className="w-10 h-10 bg-violet-100 rounded-2xl flex items-center justify-center">
                        <Database className="w-5 h-5 text-violet-600" />
                    </div>
                    <div>
                        <h1 className="text-2xl font-bold text-slate-900">{t('knowledge.title')}</h1>
                        <p className="text-sm text-slate-500">
                            {data ? `${data.total} ${t('knowledge.chunks')}` : t('common.loading')}
                        </p>
                    </div>
                </div>
                <button
                    onClick={handleReindex}
                    disabled={reindexing}
                    className="flex items-center gap-2 px-4 py-2 bg-violet-600 text-white rounded-xl text-sm font-medium hover:bg-violet-700 transition disabled:opacity-50"
                >
                    <RefreshCw className={`w-4 h-4 ${reindexing ? 'animate-spin' : ''}`} />
                    {reindexing ? t('knowledge.reindexing') : t('knowledge.reindex')}
                </button>
            </div>

            {/* KB Auto-Generation Panel */}
            <div className="bg-white rounded-2xl border border-slate-100 p-5 mb-6">
                <div className="flex items-center gap-2 mb-3">
                    <Wand2 className="w-4 h-4 text-violet-500" />
                    <h2 className="text-sm font-semibold text-slate-700">{t('knowledge.generate_from_desc')}</h2>
                </div>
                <textarea
                    value={genDescription}
                    onChange={e => setGenDescription(e.target.value)}
                    placeholder={t('knowledge.generate_placeholder')}
                    rows={3}
                    className="w-full px-3 py-2 border border-slate-200 rounded-xl text-sm outline-none focus:ring-2 focus:ring-violet-400 resize-none mb-3"
                />
                <button
                    onClick={handleGenerate}
                    disabled={generating || !genDescription.trim()}
                    className="flex items-center gap-2 px-4 py-2 bg-violet-600 text-white rounded-xl text-sm font-medium hover:bg-violet-700 transition disabled:opacity-50"
                >
                    {generating ? <Loader2 className="w-4 h-4 animate-spin" /> : <Wand2 className="w-4 h-4" />}
                    {generating ? t('knowledge.generating_btn') : t('knowledge.generate_btn')}
                </button>

                {genResult && (
                    <div className="mt-4 pt-4 border-t border-slate-100">
                        <p className="text-sm font-medium text-slate-700 mb-3">
                            <CheckCircle2 className="inline w-4 h-4 text-green-500 mr-1" />
                            {t('knowledge.generate_result_summary', { count: genResult.faqCount, chunks: genResult.chunksIndexed })}
                        </p>
                        <div className="space-y-2">
                            {genResult.preview.slice(0, 3).map((qa, i) => (
                                <div key={i} className="bg-slate-50 rounded-xl p-3 text-sm">
                                    <p className="font-medium text-slate-700 mb-1">Q: {qa.question}</p>
                                    <p className="text-slate-500">R: {qa.answer}</p>
                                </div>
                            ))}
                        </div>
                    </div>
                )}
            </div>

            <div className="relative mb-4">
                <Search className="absolute left-3 top-1/2 -translate-y-1/2 w-4 h-4 text-slate-400" />
                <input
                    type="text"
                    placeholder={t('knowledge.search_placeholder')}
                    value={search}
                    onChange={e => setSearch(e.target.value)}
                    className="w-full pl-10 pr-4 py-2.5 border border-slate-200 rounded-xl text-sm outline-none focus:ring-2 focus:ring-violet-400"
                />
            </div>

            {loading ? (
                <div className="flex items-center justify-center py-20">
                    <Loader2 className="w-8 h-8 animate-spin text-slate-400" />
                </div>
            ) : filteredEntries.length === 0 ? (
                <div className="text-center py-20 text-slate-400">
                    <FileText className="w-12 h-12 mx-auto mb-3 opacity-30" />
                    <p className="font-medium">{t('knowledge.no_documents')}</p>
                    <p className="text-sm mt-1">{t('knowledge.import_hint')}</p>
                </div>
            ) : (
                <div className="space-y-3">
                    {filteredEntries.map((entry, i) => (
                        <div key={entry.id} className="bg-white rounded-2xl border border-slate-100 p-5 hover:shadow-sm transition group">
                            <div className="flex items-start justify-between gap-4">
                                <div className="flex-1 min-w-0">
                                    <div className="flex items-center gap-2 mb-2">
                                        <span className="text-xs font-mono bg-slate-100 text-slate-500 px-2 py-0.5 rounded-lg">
                                            #{(page - 1) * PAGE_SIZE + i + 1}
                                        </span>
                                        {entry.metadata && (
                                            <span className="text-xs text-slate-400">
                                                {Object.entries(entry.metadata as Record<string, unknown>)
                                                    .slice(0, 2)
                                                    .map(([k, v]) => `${k}: ${v}`)
                                                    .join(' · ')}
                                            </span>
                                        )}
                                        <span className="text-xs text-slate-300 ml-auto">
                                            {new Date(entry.createdAt).toLocaleDateString()}
                                        </span>
                                    </div>
                                    <p className="text-sm text-slate-700 leading-relaxed line-clamp-4">
                                        {entry.content}
                                    </p>
                                </div>
                                <button
                                    onClick={() => handleDelete(entry.id)}
                                    disabled={deletingId === entry.id}
                                    className="opacity-0 group-hover:opacity-100 p-2 text-red-400 hover:text-red-600 hover:bg-red-50 rounded-xl transition"
                                    title="Supprimer ce chunk"
                                >
                                    {deletingId === entry.id
                                        ? <Loader2 className="w-4 h-4 animate-spin" />
                                        : <Trash2 className="w-4 h-4" />}
                                </button>
                            </div>
                        </div>
                    ))}
                </div>
            )}

            {!search && totalPages > 1 && (
                <div className="flex items-center justify-between mt-6">
                    <p className="text-sm text-slate-500">Page {page} sur {totalPages}</p>
                    <div className="flex gap-2">
                        <button
                            onClick={() => handlePageChange(page - 1)}
                            disabled={page === 1}
                            className="p-2 rounded-xl border border-slate-200 hover:bg-slate-50 disabled:opacity-40 transition"
                        >
                            <ChevronLeft className="w-4 h-4" />
                        </button>
                        <button
                            onClick={() => handlePageChange(page + 1)}
                            disabled={page === totalPages}
                            className="p-2 rounded-xl border border-slate-200 hover:bg-slate-50 disabled:opacity-40 transition"
                        >
                            <ChevronRight className="w-4 h-4" />
                        </button>
                    </div>
                </div>
            )}
        </div>
    );
}