import React, { useEffect, useState, useRef } from 'react';
import { Search, Plus, FileText, Upload, ArrowLeft, CloudUpload, File as FileIcon, X } from 'lucide-react';
import { Button, Input, TableHeader, TableRow, TableHead, TableCell, Card, Dialog } from '../components/UI';
import { KnowledgeBase } from '../types';
import { createKnowledgeBase, deleteKnowledgeDocument, fetchKnowledgeBases, uploadKnowledgeDocument } from '../services/backendApi';

export const KnowledgeBasePage: React.FC = () => {
  const [view, setView] = useState<'list' | 'detail'>('list');
  const [selectedKb, setSelectedKb] = useState<KnowledgeBase | null>(null);
  const [searchTerm, setSearchTerm] = useState('');
  const [kbs, setKbs] = useState<KnowledgeBase[]>([]);
  const [isUploadOpen, setIsUploadOpen] = useState(false);
  const [isCreateKbOpen, setIsCreateKbOpen] = useState(false);
  const [newKbName, setNewKbName] = useState('');
  const [isLoading, setIsLoading] = useState(true);

  const filteredKbs = kbs.filter(kb => kb.name.toLowerCase().includes(searchTerm.toLowerCase()));

  const refreshKnowledgeBases = async () => {
    setIsLoading(true);
    try {
      const list = await fetchKnowledgeBases();
      setKbs(list);
      if (selectedKb) {
        const nextSelected = list.find((item) => item.id === selectedKb.id) || null;
        setSelectedKb(nextSelected);
      }
    } catch (error) {
      console.error(error);
      alert('加载知识库失败，请检查后端服务。');
    } finally {
      setIsLoading(false);
    }
  };

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

  const handleSelect = (kb: KnowledgeBase) => {
    setSelectedKb(kb);
    setView('detail');
  };

  const handleImportClick = () => {
    setIsUploadOpen(true);
  };

  const handleCreateKb = async () => {
    if (!newKbName.trim()) return;
    try {
      await createKnowledgeBase(newKbName.trim());
      await refreshKnowledgeBases();
      setIsCreateKbOpen(false);
      setNewKbName('');
    } catch (error) {
      console.error(error);
      alert('新建知识库失败。');
    }
  };

  if (view === 'detail' && selectedKb) {
    return (
      <div className="py-4 pb-10">
        <KnowledgeBaseDetail 
          kb={selectedKb} 
          onBack={() => setView('list')} 
          onImport={handleImportClick}
          onDeleteDocument={async (docId) => {
            try {
              await deleteKnowledgeDocument(selectedKb.id, docId);
              await refreshKnowledgeBases();
            } catch (error) {
              console.error(error);
              alert('删除文档失败。');
            }
          }}
        />
        <UploadModal
          kbId={selectedKb.id}
          isOpen={isUploadOpen}
          onClose={() => setIsUploadOpen(false)}
          onUploaded={refreshKnowledgeBases}
        />
      </div>
    );
  }

  return (
    <div className="space-y-6 animate-in fade-in py-4 pb-10">
      <div className="flex items-center justify-between">
        <h1 className="text-2xl font-bold tracking-tight text-white">知识库</h1>
      </div>

      {/* Search Bar - Layout aligned with History Page and width filled */}
      <div className="bg-card/50 p-4 rounded-lg border border-white/5 shadow-sm">
        <div className="relative w-full">
            <Search className="absolute left-2.5 top-2.5 h-4 w-4 text-muted-foreground" />
            <Input 
              placeholder="搜索知识库名称..." 
              className="pl-9 border-0 bg-white/5 w-full"
              value={searchTerm}
              onChange={(e) => setSearchTerm(e.target.value)}
            />
        </div>
      </div>

      <div className="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-6">
        {filteredKbs.map(kb => (
          <Card 
            key={kb.id} 
            className="p-6 hover:border-primary/50 transition-colors cursor-pointer group"
          >
            <div onClick={() => handleSelect(kb)}>
              <div className="flex items-start justify-between mb-4">
                <div className="p-2 bg-primary/10 rounded-lg text-primary">
                  <FileText className="h-6 w-6" />
                </div>
              </div>
              <h3 className="text-lg font-semibold group-hover:text-primary transition-colors text-white">{kb.name}</h3>
              <div className="mt-4 space-y-1 text-sm text-muted-foreground">
                 <p>文档数量: {kb.documents.length}</p>
                 <p>创建人: {kb.creator}</p>
                 <p>创建时间: {kb.createdAt}</p>
              </div>
            </div>
          </Card>
        ))}
        
        {/* Add New Placeholder */}
        <div 
            onClick={() => setIsCreateKbOpen(true)}
            className="border border-dashed border-white/10 rounded-xl p-6 flex flex-col items-center justify-center text-muted-foreground hover:bg-white/5 hover:border-primary/30 transition-all cursor-pointer min-h-[200px]"
        >
            <Plus className="h-8 w-8 mb-2 opacity-50" />
            <span>新建知识库</span>
        </div>
        {!isLoading && filteredKbs.length === 0 && (
          <div className="col-span-full text-center text-muted-foreground py-8">暂无知识库</div>
        )}
        {isLoading && (
          <div className="col-span-full text-center text-muted-foreground py-8">加载中...</div>
        )}
      </div>

      {/* New Knowledge Base Dialog */}
      <Dialog
        isOpen={isCreateKbOpen}
        onClose={() => setIsCreateKbOpen(false)}
        title="新建知识库"
        footer={
          <>
            <Button variant="ghost" onClick={() => setIsCreateKbOpen(false)}>取消</Button>
            <Button onClick={handleCreateKb} disabled={!newKbName.trim()}>确认创建</Button>
          </>
        }
      >
        <div className="space-y-4">
          <div className="space-y-1.5">
            <label className="text-[10px] font-black text-muted-foreground uppercase tracking-widest block">知识库名称</label>
            <Input 
              value={newKbName}
              onChange={(e) => setNewKbName(e.target.value)}
              placeholder="请输入知识库名称..."
              autoFocus
              onKeyDown={(e) => e.key === 'Enter' && handleCreateKb()}
            />
          </div>
          <p className="text-xs text-muted-foreground">
            知识库用于存储私域文档，AI 小助手在回答问题时会优先检索绑定的知识库内容。
          </p>
        </div>
      </Dialog>
    </div>
  );
};

const KnowledgeBaseDetail: React.FC<{ 
  kb: KnowledgeBase; 
  onBack: () => void;
  onImport: () => void;
  onDeleteDocument: (docId: string) => void;
}> = ({ kb, onBack, onImport, onDeleteDocument }) => {
  const [docSearch, setDocSearch] = useState('');
  const filteredDocs = kb.documents.filter(d => d.name.toLowerCase().includes(docSearch.toLowerCase()));

  return (
    <div className="space-y-6 animate-in slide-in-from-right-4">
      <div className="flex items-center justify-between">
        <div className="flex items-center space-x-4">
          <Button variant="ghost" size="icon" onClick={onBack}>
            <ArrowLeft className="h-4 w-4" />
          </Button>
          <div>
            <h1 className="text-2xl font-bold text-white">{kb.name}</h1>
            <p className="text-sm text-muted-foreground">创建于 {kb.createdAt} · by {kb.creator}</p>
          </div>
        </div>
        <Button onClick={onImport}>
            <Upload className="mr-2 h-4 w-4" /> 新增知识 (导入)
        </Button>
      </div>

      <Card className="overflow-hidden border-white/5">
        <div className="p-4 border-b border-white/5 flex justify-between items-center bg-white/5">
            <h3 className="font-medium text-white">文档列表</h3>
            <div className="w-64">
                <Input 
                    placeholder="搜索文档..." 
                    value={docSearch}
                    onChange={(e) => setDocSearch(e.target.value)}
                    className="bg-black/20 border-transparent focus:bg-black/40"
                />
            </div>
        </div>
        <table className="w-full text-sm">
          <TableHeader>
            <TableRow>
              <TableHead>文档名称</TableHead>
              <TableHead>大小</TableHead>
              <TableHead>上传时间</TableHead>
              <TableHead className="text-right">操作</TableHead>
            </TableRow>
          </TableHeader>
          <tbody>
            {filteredDocs.length > 0 ? filteredDocs.map(doc => (
              <TableRow key={doc.id}>
                <TableCell className="font-medium flex items-center text-white">
                    <FileText className="h-4 w-4 mr-2 text-primary"/> {doc.name}
                </TableCell>
                <TableCell className="text-muted-foreground">{doc.size}</TableCell>
                <TableCell className="text-muted-foreground">{doc.uploadDate}</TableCell>
                <TableCell className="text-right">
                    <Button
                      variant="ghost"
                      size="sm"
                      className="text-destructive hover:text-destructive/80"
                      onClick={() => onDeleteDocument(doc.id)}
                    >
                      删除
                    </Button>
                </TableCell>
              </TableRow>
            )) : (
                <TableRow>
                    <TableCell colSpan={4} className="text-center py-8 text-muted-foreground">暂无文档</TableCell>
                </TableRow>
            )}
          </tbody>
        </table>
      </Card>
    </div>
  );
};

const UploadModal: React.FC<{ kbId: string; isOpen: boolean; onClose: () => void; onUploaded: () => Promise<void> }> = ({ kbId, isOpen, onClose, onUploaded }) => {
    const [dragActive, setDragActive] = useState(false);
    const [files, setFiles] = useState<File[]>([]);
    const inputRef = useRef<HTMLInputElement>(null);

    const handleDrag = (e: React.DragEvent) => {
        e.preventDefault();
        e.stopPropagation();
        if (e.type === "dragenter" || e.type === "dragover") {
            setDragActive(true);
        } else if (e.type === "dragleave") {
            setDragActive(false);
        }
    };

    const handleDrop = (e: React.DragEvent) => {
        e.preventDefault();
        e.stopPropagation();
        setDragActive(false);
        if (e.dataTransfer.files && e.dataTransfer.files[0]) {
            setFiles(prev => [...prev, ...Array.from(e.dataTransfer.files)]);
        }
    };

    const handleChange = (e: React.ChangeEvent<HTMLInputElement>) => {
        e.preventDefault();
        if (e.target.files && e.target.files[0]) {
            setFiles(prev => [...prev, ...Array.from(e.target.files || [])]);
        }
    };

    const removeFile = (idx: number) => {
        setFiles(prev => prev.filter((_, i) => i !== idx));
    };

    const handleUpload = async () => {
        if (files.length === 0) return;
        try {
            await Promise.all(files.map((file) => uploadKnowledgeDocument(kbId, file)));
            await onUploaded();
            onClose();
            setFiles([]);
        } catch (error) {
            console.error(error);
            alert('上传失败，请稍后重试。');
        }
    };

    return (
        <Dialog 
            isOpen={isOpen} 
            onClose={onClose} 
            title="上传知识文档"
            footer={
                <>
                    <Button variant="ghost" onClick={onClose}>取消</Button>
                    <Button onClick={handleUpload}>确认上传</Button>
                </>
            }
        >
            <div 
                className={`relative flex flex-col items-center justify-center w-full h-48 rounded-lg border-2 border-dashed transition-colors ${dragActive ? "border-primary bg-primary/10" : "border-white/10 bg-white/5 hover:bg-white/10"}`}
                onDragEnter={handleDrag}
                onDragLeave={handleDrag}
                onDragOver={handleDrag}
                onDrop={handleDrop}
                onClick={() => inputRef.current?.click()}
            >
                <input 
                    ref={inputRef} 
                    type="file" 
                    multiple 
                    className="hidden" 
                    onChange={handleChange} 
                    accept=".pdf,.doc,.docx,.txt,.md"
                />
                <CloudUpload className={`h-10 w-10 mb-3 ${dragActive ? 'text-primary' : 'text-muted-foreground'}`} />
                <p className="text-sm text-muted-foreground text-center">
                    <span className="font-semibold text-primary">点击上传</span> 或将文件拖拽到此处
                </p>
                <p className="text-xs text-muted-foreground mt-1 text-white/50">支持 PDF, DOCX, TXT (Max 10MB)</p>
            </div>

            {files.length > 0 && (
                <div className="mt-4 space-y-2 max-h-40 overflow-y-auto pr-1 custom-scrollbar">
                    {files.map((file, idx) => (
                        <div key={idx} className="flex items-center justify-between p-2 rounded-md bg-white/5 border border-white/5">
                            <div className="flex items-center space-x-2 overflow-hidden">
                                <FileIcon className="h-4 w-4 text-primary shrink-0" />
                                <span className="text-sm truncate max-w-[200px] text-white">{file.name}</span>
                                <span className="text-xs text-muted-foreground">({(file.size / 1024).toFixed(1)} KB)</span>
                            </div>
                            <button onClick={() => removeFile(idx)} className="text-muted-foreground hover:text-destructive transition-colors">
                                <X className="h-4 w-4" />
                            </button>
                        </div>
                    ))}
                </div>
            )}
        </Dialog>
    );
};