import { useState, useEffect } from 'react';
import {
    FileText, Search, Filter, Plus, ChevronRight, Clock, User, Check, X,
    AlertCircle, Eye, Edit, Archive, Send, ThumbsUp, FolderOpen, Book,
    ClipboardList, FileCheck, HelpCircle, MoreVertical, History, Download
} from 'lucide-react';
import { documentsApi, Document, DocumentType, DocumentStatus, DocumentVersion } from '../lib/documentsApi';

const TYPE_CONFIG: Record<DocumentType, { icon: React.ElementType; color: string; label: string }> = {
    SOP: { icon: Book, color: 'text-indigo-500 bg-indigo-50 dark:bg-indigo-900/30', label: 'Standard Operating Procedure' },
    POLICY: { icon: FileCheck, color: 'text-purple-500 bg-purple-50 dark:bg-purple-900/30', label: 'Policy' },
    FORM: { icon: ClipboardList, color: 'text-blue-500 bg-blue-50 dark:bg-blue-900/30', label: 'Form' },
    CHECKLIST: { icon: Check, color: 'text-emerald-500 bg-emerald-50 dark:bg-emerald-900/30', label: 'Checklist' },
    GUIDE: { icon: HelpCircle, color: 'text-amber-500 bg-amber-50 dark:bg-amber-900/30', label: 'Guide' },
    OTHER: { icon: FileText, color: 'text-slate-500 bg-slate-50 dark:bg-slate-700', label: 'Document' }
};

const STATUS_CONFIG: Record<DocumentStatus, { color: string; label: string }> = {
    DRAFT: { color: 'bg-slate-100 text-slate-600 dark:bg-slate-700 dark:text-slate-300', label: 'Draft' },
    PENDING_APPROVAL: { color: 'bg-amber-100 text-amber-700 dark:bg-amber-900/30 dark:text-amber-400', label: 'Pending Approval' },
    APPROVED: { color: 'bg-emerald-100 text-emerald-700 dark:bg-emerald-900/30 dark:text-emerald-400', label: 'Approved' },
    ARCHIVED: { color: 'bg-red-100 text-red-700 dark:bg-red-900/30 dark:text-red-400', label: 'Archived' }
};

export default function DocumentsPage() {
    const [documents, setDocuments] = useState<Document[]>([]);
    const [loading, setLoading] = useState(true);
    const [searchTerm, setSearchTerm] = useState('');
    const [filterType, setFilterType] = useState<DocumentType | ''>('');
    const [filterStatus, setFilterStatus] = useState<DocumentStatus | ''>('');
    const [filterCategory, setFilterCategory] = useState('');
    const [selectedDoc, setSelectedDoc] = useState<Document | null>(null);
    const [versions, setVersions] = useState<DocumentVersion[]>([]);
    const [showVersions, setShowVersions] = useState(false);
    const [pendingAcks, setPendingAcks] = useState<Document[]>([]);

    useEffect(() => {
        loadDocuments();
        loadPendingAcks();
    }, [filterType, filterStatus, filterCategory]);

    async function loadDocuments() {
        setLoading(true);
        try {
            const docs = await documentsApi.getDocuments({
                type: filterType || undefined,
                status: filterStatus || undefined,
                category: filterCategory || undefined,
                search: searchTerm || undefined
            });
            setDocuments(docs);
        } catch (error) {
            console.error('Failed to load documents:', error);
        } finally {
            setLoading(false);
        }
    }

    async function loadPendingAcks() {
        try {
            const pending = await documentsApi.getPendingAcks();
            setPendingAcks(pending);
        } catch (error) {
            console.error('Failed to load pending acks:', error);
        }
    }

    async function handleViewDocument(doc: Document) {
        setSelectedDoc(doc);
        try {
            const vers = await documentsApi.getVersions(doc.id);
            setVersions(vers);
        } catch (error) {
            console.error('Failed to load versions:', error);
        }
    }

    async function handleAcknowledge(docId: string) {
        try {
            await documentsApi.acknowledgeDocument(docId);
            setPendingAcks(prev => prev.filter(d => d.id !== docId));
            if (selectedDoc?.id === docId) {
                const updated = await documentsApi.getDocument(docId);
                setSelectedDoc(updated);
            }
        } catch (error) {
            console.error('Failed to acknowledge:', error);
        }
    }

    const categories = [...new Set(documents.map(d => d.category).filter(Boolean))];

    const filteredDocs = documents.filter(doc => {
        if (searchTerm && !doc.title.toLowerCase().includes(searchTerm.toLowerCase())) {
            return false;
        }
        return true;
    });

    const groupedDocs = filteredDocs.reduce((acc, doc) => {
        const cat = doc.category || 'Uncategorized';
        if (!acc[cat]) acc[cat] = [];
        acc[cat].push(doc);
        return acc;
    }, {} as Record<string, Document[]>);

    return (
        <div className="space-y-6 pb-20">
            {/* Header */}
            <header className="flex flex-col sm:flex-row justify-between items-start sm:items-center gap-4">
                <div>
                    <h2 className="text-2xl font-bold text-slate-900 dark:text-white flex items-center gap-2">
                        <Book className="text-indigo-500" />
                        SOP Library
                    </h2>
                    <p className="text-sm text-slate-500">Standard Operating Procedures & Compliance Documents</p>
                </div>
                <button className="px-4 py-2 rounded-lg bg-indigo-600 text-white text-sm font-medium flex items-center gap-2 hover:bg-indigo-700 transition-colors">
                    <Plus size={16} />
                    New Document
                </button>
            </header>

            {/* Pending Acknowledgements Banner */}
            {pendingAcks.length > 0 && (
                <div className="bg-amber-50 dark:bg-amber-900/20 border border-amber-200 dark:border-amber-800 rounded-xl p-4">
                    <div className="flex items-center gap-3">
                        <AlertCircle className="text-amber-600" size={20} />
                        <div className="flex-1">
                            <p className="font-medium text-amber-800 dark:text-amber-200">
                                {pendingAcks.length} document{pendingAcks.length > 1 ? 's require' : ' requires'} your acknowledgement
                            </p>
                            <p className="text-sm text-amber-600 dark:text-amber-400">
                                Please review and acknowledge these documents to remain compliant.
                            </p>
                        </div>
                        <button
                            onClick={() => handleViewDocument(pendingAcks[0])}
                            className="px-3 py-1.5 bg-amber-600 text-white text-sm font-medium rounded-lg hover:bg-amber-700"
                        >
                            Review Now
                        </button>
                    </div>
                </div>
            )}

            {/* Filters */}
            <div className="flex flex-wrap gap-3">
                <div className="relative flex-1 min-w-[200px]">
                    <Search className="absolute left-3 top-1/2 -translate-y-1/2 text-slate-400" size={16} />
                    <input
                        type="text"
                        placeholder="Search documents..."
                        value={searchTerm}
                        onChange={(e) => setSearchTerm(e.target.value)}
                        className="w-full pl-9 pr-4 py-2 rounded-lg border border-slate-200 dark:border-slate-600 bg-white dark:bg-slate-800 text-sm focus:ring-2 focus:ring-indigo-500"
                    />
                </div>
                <select
                    value={filterType}
                    onChange={(e) => setFilterType(e.target.value as DocumentType | '')}
                    className="px-3 py-2 rounded-lg border border-slate-200 dark:border-slate-600 bg-white dark:bg-slate-800 text-sm"
                >
                    <option value="">All Types</option>
                    <option value="SOP">SOPs</option>
                    <option value="POLICY">Policies</option>
                    <option value="FORM">Forms</option>
                    <option value="CHECKLIST">Checklists</option>
                    <option value="GUIDE">Guides</option>
                </select>
                <select
                    value={filterStatus}
                    onChange={(e) => setFilterStatus(e.target.value as DocumentStatus | '')}
                    className="px-3 py-2 rounded-lg border border-slate-200 dark:border-slate-600 bg-white dark:bg-slate-800 text-sm"
                >
                    <option value="">All Statuses</option>
                    <option value="APPROVED">Approved</option>
                    <option value="PENDING_APPROVAL">Pending</option>
                    <option value="DRAFT">Draft</option>
                    <option value="ARCHIVED">Archived</option>
                </select>
                {categories.length > 0 && (
                    <select
                        value={filterCategory}
                        onChange={(e) => setFilterCategory(e.target.value)}
                        className="px-3 py-2 rounded-lg border border-slate-200 dark:border-slate-600 bg-white dark:bg-slate-800 text-sm"
                    >
                        <option value="">All Categories</option>
                        {categories.map(cat => (
                            <option key={cat} value={cat}>{cat}</option>
                        ))}
                    </select>
                )}
            </div>

            {/* Documents Grid */}
            {loading ? (
                <div className="text-center py-20 text-slate-500">Loading documents...</div>
            ) : filteredDocs.length === 0 ? (
                <div className="text-center py-20">
                    <FolderOpen className="mx-auto mb-3 text-slate-300" size={48} />
                    <p className="text-slate-500">No documents found</p>
                    <p className="text-sm text-slate-400 mt-1">Create your first document or adjust filters</p>
                </div>
            ) : (
                <div className="space-y-6">
                    {Object.entries(groupedDocs).map(([category, docs]) => (
                        <div key={category}>
                            <h3 className="text-sm font-bold text-slate-500 uppercase mb-3 flex items-center gap-2">
                                <FolderOpen size={14} />
                                {category}
                                <span className="text-xs font-normal text-slate-400">({docs.length})</span>
                            </h3>
                            <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-4">
                                {docs.map(doc => {
                                    const typeConfig = TYPE_CONFIG[doc.type];
                                    const TypeIcon = typeConfig.icon;
                                    const statusConfig = STATUS_CONFIG[doc.status];
                                    const isPending = pendingAcks.some(p => p.id === doc.id);

                                    return (
                                        <div
                                            key={doc.id}
                                            onClick={() => handleViewDocument(doc)}
                                            className={`bg-white dark:bg-slate-800 rounded-xl border transition-all cursor-pointer hover:shadow-md ${isPending
                                                    ? 'border-amber-300 dark:border-amber-700 ring-2 ring-amber-100 dark:ring-amber-900/30'
                                                    : 'border-slate-200 dark:border-slate-700 hover:border-indigo-300 dark:hover:border-indigo-700'
                                                }`}
                                        >
                                            <div className="p-4">
                                                <div className="flex items-start gap-3">
                                                    <div className={`p-2 rounded-lg ${typeConfig.color}`}>
                                                        <TypeIcon size={20} />
                                                    </div>
                                                    <div className="flex-1 min-w-0">
                                                        <h4 className="font-medium text-slate-900 dark:text-white truncate">
                                                            {doc.title}
                                                        </h4>
                                                        <p className="text-xs text-slate-500 mt-0.5">
                                                            {typeConfig.label} • v{doc.version}
                                                        </p>
                                                    </div>
                                                    {isPending && (
                                                        <span className="flex-shrink-0 w-2 h-2 bg-amber-500 rounded-full animate-pulse" />
                                                    )}
                                                </div>

                                                <div className="flex items-center justify-between mt-4 pt-3 border-t border-slate-100 dark:border-slate-700">
                                                    <span className={`px-2 py-0.5 rounded-full text-xs font-medium ${statusConfig.color}`}>
                                                        {statusConfig.label}
                                                    </span>
                                                    <div className="flex items-center gap-1.5 text-xs text-slate-400">
                                                        <Clock size={12} />
                                                        {new Date(doc.updatedAt).toLocaleDateString()}
                                                    </div>
                                                </div>
                                            </div>
                                        </div>
                                    );
                                })}
                            </div>
                        </div>
                    ))}
                </div>
            )}

            {/* Document Viewer Modal */}
            {selectedDoc && (
                <div className="fixed inset-0 bg-black/50 flex items-center justify-center p-4 z-50" onClick={() => setSelectedDoc(null)}>
                    <div
                        className="bg-white dark:bg-slate-800 rounded-2xl max-w-4xl w-full max-h-[90vh] overflow-hidden shadow-2xl flex flex-col"
                        onClick={e => e.stopPropagation()}
                    >
                        {/* Modal Header */}
                        <div className="p-4 border-b border-slate-200 dark:border-slate-700 flex justify-between items-start">
                            <div className="flex items-start gap-3">
                                <div className={`p-2 rounded-lg ${TYPE_CONFIG[selectedDoc.type].color}`}>
                                    {(() => {
                                        const Icon = TYPE_CONFIG[selectedDoc.type].icon;
                                        return <Icon size={24} />;
                                    })()}
                                </div>
                                <div>
                                    <h3 className="text-lg font-bold text-slate-900 dark:text-white">{selectedDoc.title}</h3>
                                    <p className="text-sm text-slate-500">
                                        {TYPE_CONFIG[selectedDoc.type].label} • Version {selectedDoc.version}
                                    </p>
                                </div>
                            </div>
                            <div className="flex items-center gap-2">
                                <button
                                    onClick={() => setShowVersions(!showVersions)}
                                    className={`p-2 rounded-lg transition-colors ${showVersions ? 'bg-indigo-100 text-indigo-600' : 'hover:bg-slate-100 dark:hover:bg-slate-700 text-slate-400'}`}
                                    title="Version History"
                                >
                                    <History size={18} />
                                </button>
                                <button
                                    onClick={() => setSelectedDoc(null)}
                                    className="p-2 rounded-lg hover:bg-slate-100 dark:hover:bg-slate-700"
                                >
                                    <X size={20} />
                                </button>
                            </div>
                        </div>

                        {/* Document Status Bar */}
                        <div className="px-4 py-2 bg-slate-50 dark:bg-slate-700/50 border-b border-slate-200 dark:border-slate-700 flex items-center justify-between text-sm">
                            <div className="flex items-center gap-4">
                                <span className={`px-2 py-0.5 rounded-full text-xs font-medium ${STATUS_CONFIG[selectedDoc.status].color}`}>
                                    {STATUS_CONFIG[selectedDoc.status].label}
                                </span>
                                {selectedDoc.effectiveDate && (
                                    <span className="text-slate-500">
                                        Effective: {new Date(selectedDoc.effectiveDate).toLocaleDateString()}
                                    </span>
                                )}
                                {selectedDoc.expiresAt && (
                                    <span className="text-amber-600">
                                        Expires: {new Date(selectedDoc.expiresAt).toLocaleDateString()}
                                    </span>
                                )}
                            </div>
                            <div className="flex items-center gap-2 text-slate-500">
                                {selectedDoc.createdBy && (
                                    <span className="flex items-center gap-1">
                                        <User size={14} />
                                        {selectedDoc.createdBy.name}
                                    </span>
                                )}
                            </div>
                        </div>

                        {/* Content Area */}
                        <div className="flex-1 overflow-hidden flex">
                            {/* Main Content */}
                            <div className={`flex-1 overflow-y-auto p-6 ${showVersions ? 'border-r border-slate-200 dark:border-slate-700' : ''}`}>
                                <div
                                    className="prose prose-slate dark:prose-invert max-w-none"
                                    dangerouslySetInnerHTML={{ __html: selectedDoc.content }}
                                />
                            </div>

                            {/* Version Sidebar */}
                            {showVersions && (
                                <div className="w-64 overflow-y-auto p-4 bg-slate-50 dark:bg-slate-900/50">
                                    <h4 className="font-medium text-slate-900 dark:text-white mb-3">Version History</h4>
                                    <div className="space-y-2">
                                        {versions.map(ver => (
                                            <div
                                                key={ver.id}
                                                className={`p-2 rounded-lg text-sm cursor-pointer ${ver.version === selectedDoc.version
                                                        ? 'bg-indigo-100 dark:bg-indigo-900/30 border border-indigo-300 dark:border-indigo-700'
                                                        : 'bg-white dark:bg-slate-800 border border-slate-200 dark:border-slate-700 hover:border-indigo-300'
                                                    }`}
                                            >
                                                <div className="flex justify-between items-center">
                                                    <span className="font-medium">v{ver.version}</span>
                                                    <span className="text-xs text-slate-400">{new Date(ver.createdAt).toLocaleDateString()}</span>
                                                </div>
                                                {ver.changeNotes && (
                                                    <p className="text-xs text-slate-500 mt-1 truncate">{ver.changeNotes}</p>
                                                )}
                                            </div>
                                        ))}
                                    </div>
                                </div>
                            )}
                        </div>

                        {/* Modal Footer */}
                        <div className="p-4 border-t border-slate-200 dark:border-slate-700 flex justify-between items-center">
                            <div>
                                {selectedDoc.requiresAck && (
                                    <button
                                        onClick={() => handleAcknowledge(selectedDoc.id)}
                                        className="px-4 py-2 bg-emerald-600 text-white rounded-lg text-sm font-medium flex items-center gap-2 hover:bg-emerald-700"
                                    >
                                        <Check size={16} />
                                        I Acknowledge This Document
                                    </button>
                                )}
                            </div>
                            <div className="flex gap-2">
                                <button className="p-2 rounded-lg border border-slate-200 dark:border-slate-600 hover:bg-slate-50 dark:hover:bg-slate-700 text-slate-500">
                                    <Download size={18} />
                                </button>
                                <button className="p-2 rounded-lg border border-slate-200 dark:border-slate-600 hover:bg-slate-50 dark:hover:bg-slate-700 text-slate-500">
                                    <Edit size={18} />
                                </button>
                            </div>
                        </div>
                    </div>
                </div>
            )}
        </div>
    );
}