import React, { useState, useEffect, useRef } from 'react';
import ReactMarkdown from 'react-markdown';
import remarkGfm from 'remark-gfm';
import rehypeSanitize from 'rehype-sanitize';
import mermaid from 'mermaid';
import { X, Download, Loader, AlertCircle, FileText, File } from 'lucide-react';

mermaid.initialize({
  startOnLoad: false,
  theme: 'dark',
  darkMode: true,
  themeVariables: {
    background: '#0f172a',
    primaryColor: '#1e3a5f',
    primaryTextColor: '#e2e8f0',
    primaryBorderColor: '#0ea5e9',
    lineColor: '#475569',
    secondaryColor: '#1a2e1a',
    tertiaryColor: '#2d1f14',
    edgeLabelBackground: '#1e293b',
    clusterBkg: '#1e293b',
    titleColor: '#e2e8f0',
    fontFamily: 'monospace'
  }
});

let mermaidCounter = 0;

function MermaidDiagram({ code }) {
  const ref = useRef(null);
  const [svgError, setSvgError] = useState('');

  useEffect(() => {
    let cancelled = false;
    const id = `mermaid-kb-${++mermaidCounter}`;
    mermaid.render(id, code)
      .then(({ svg }) => {
        if (!cancelled && ref.current) {
          ref.current.innerHTML = svg;
          // Make SVG responsive
          const svgEl = ref.current.querySelector('svg');
          if (svgEl) {
            svgEl.removeAttribute('width');
            svgEl.removeAttribute('height');
            svgEl.style.width = '100%';
            svgEl.style.maxWidth = '100%';
          }
        }
      })
      .catch((err) => {
        if (!cancelled) setSvgError(err.message || 'Failed to render diagram');
      });
    return () => { cancelled = true; };
  }, [code]);

  if (svgError) {
    return (
      <pre style={{ color: '#EF4444', fontSize: '0.75rem', padding: '0.75rem', background: 'rgba(239,68,68,0.1)', borderRadius: '0.375rem', overflowX: 'auto' }}>
        Mermaid render error: {svgError}
      </pre>
    );
  }

  return (
    <div
      ref={ref}
      style={{ background: 'rgba(15,23,42,0.6)', border: '1px solid rgba(14,165,233,0.2)', borderRadius: '0.5rem', padding: '1rem', margin: '1rem 0', overflowX: 'auto' }}
    />
  );
}

const API_BASE = process.env.REACT_APP_API_BASE || 'http://localhost:3001/api';

export default function KnowledgeBaseViewer({ article, onClose }) {
  const [content, setContent] = useState('');
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState('');

  useEffect(() => {
    fetchArticleContent();
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [article.id]);

  const fetchArticleContent = async () => {
    setLoading(true);
    setError('');

    try {
      const response = await fetch(`${API_BASE}/knowledge-base/${article.id}/content`, {
        credentials: 'include'
      });

      if (!response.ok) throw new Error('Failed to fetch article content');

      const text = await response.text();
      setContent(text);
    } catch (err) {
      console.error('Error fetching article content:', err);
      setError(err.message);
    } finally {
      setLoading(false);
    }
  };

  const handleDownload = async () => {
    try {
      const response = await fetch(`${API_BASE}/knowledge-base/${article.id}/download`, {
        credentials: 'include'
      });

      if (!response.ok) throw new Error('Download failed');

      const blob = await response.blob();
      const url = window.URL.createObjectURL(blob);
      const a = document.createElement('a');
      a.href = url;
      a.download = article.file_name;
      document.body.appendChild(a);
      a.click();
      window.URL.revokeObjectURL(url);
      document.body.removeChild(a);
    } catch (err) {
      console.error('Error downloading file:', err);
      setError('Failed to download file');
    }
  };

  const isMarkdown = article.file_name?.endsWith('.md');
  const isText = article.file_name?.endsWith('.txt');
  const isPDF = article.file_name?.endsWith('.pdf');
  const isImage = /\.(jpg|jpeg|png|gif|bmp)$/i.test(article.file_name || '');

  const getCategoryColor = (cat) => {
    const colors = {
      'General': '#94A3B8',
      'Policy': '#0EA5E9',
      'Procedure': '#10B981',
      'Guide': '#F59E0B',
      'Reference': '#8B5CF6'
    };
    return colors[cat] || '#94A3B8';
  };

  const formatDate = (dateString) => {
    return new Date(dateString).toLocaleDateString('en-US', {
      year: 'numeric',
      month: 'long',
      day: 'numeric'
    });
  };

  return (
    <div
      style={{
        background: 'linear-gradient(135deg, rgba(30, 41, 59, 0.95) 0%, rgba(51, 65, 85, 0.9) 50%, rgba(30, 41, 59, 0.95) 100%)',
        border: '2px solid rgba(14, 165, 233, 0.4)',
        borderRadius: '0.5rem',
        boxShadow: '0 8px 24px rgba(0, 0, 0, 0.6), 0 0 28px rgba(14, 165, 233, 0.15)',
        padding: '1.5rem',
        position: 'relative',
        overflow: 'hidden'
      }}
    >
      {/* Header */}
      <div className="flex items-start justify-between mb-4 pb-4" style={{ borderBottom: '1px solid rgba(14, 165, 233, 0.2)' }}>
        <div className="flex-1">
          <div className="flex items-center gap-3 mb-2">
            <FileText className="w-5 h-5" style={{ color: getCategoryColor(article.category) }} />
            <h2 className="text-xl font-semibold" style={{ color: '#E2E8F0', fontFamily: 'monospace' }}>
              {article.title}
            </h2>
          </div>
          {article.description && (
            <p className="text-sm mb-2" style={{ color: '#94A3B8' }}>
              {article.description}
            </p>
          )}
          <div className="flex items-center gap-3 text-xs" style={{ color: '#64748B' }}>
            <span
              className="px-2 py-1 rounded"
              style={{
                background: `${getCategoryColor(article.category)}33`,
                color: getCategoryColor(article.category),
                fontWeight: '600'
              }}
            >
              {article.category}
            </span>
            <span>Created: {formatDate(article.created_at)}</span>
            {article.created_by_username && (
              <span>By: {article.created_by_username}</span>
            )}
          </div>
        </div>
        <div className="flex gap-2 ml-4">
          <button
            onClick={handleDownload}
            className="intel-button intel-button-small"
            title="Download"
          >
            <Download className="w-4 h-4" />
          </button>
          <button
            onClick={onClose}
            className="intel-button intel-button-small"
            title="Close"
          >
            <X className="w-4 h-4" />
          </button>
        </div>
      </div>

      {/* Content */}
      <div className="kb-content-area">
        {loading && (
          <div className="text-center py-12">
            <Loader className="w-8 h-8 animate-spin mx-auto mb-4" style={{ color: '#0EA5E9' }} />
            <p style={{ color: '#94A3B8' }}>Loading document...</p>
          </div>
        )}

        {error && (
          <div className="flex items-start gap-3 p-4 rounded" style={{ background: 'rgba(239, 68, 68, 0.1)', border: '1px solid #EF4444' }}>
            <AlertCircle className="w-6 h-6 flex-shrink-0" style={{ color: '#EF4444' }} />
            <div>
              <p className="font-medium" style={{ color: '#FCA5A5' }}>Failed to Load Document</p>
              <p className="text-sm mt-1" style={{ color: '#94A3B8' }}>{error}</p>
            </div>
          </div>
        )}

        {!loading && !error && (
          <>
            {/* Markdown Rendering */}
            {isMarkdown && (
              <div className="markdown-content">
                <ReactMarkdown
                  remarkPlugins={[remarkGfm]}
                  rehypePlugins={[rehypeSanitize]}
                  components={{
                    code({ inline, className, children }) {
                      const lang = /language-(\w+)/.exec(className || '')?.[1];
                      if (!inline && lang === 'mermaid') {
                        return <MermaidDiagram code={String(children).replace(/\n$/, '')} />;
                      }
                      return (
                        <code
                          className={className}
                          style={inline ? { background: 'rgba(14,165,233,0.15)', padding: '0.1rem 0.3rem', borderRadius: '0.25rem', fontFamily: 'monospace', fontSize: '0.85em' } : {}}
                        >
                          {children}
                        </code>
                      );
                    }
                  }}
                >
                  {content}
                </ReactMarkdown>
              </div>
            )}

            {/* Plain Text */}
            {isText && !isMarkdown && (
              <pre
                className="text-sm p-4 rounded overflow-auto"
                style={{
                  background: 'rgba(15, 23, 42, 0.8)',
                  border: '1px solid rgba(14, 165, 233, 0.2)',
                  color: '#E2E8F0',
                  fontFamily: 'monospace',
                  whiteSpace: 'pre-wrap',
                  wordWrap: 'break-word',
                  maxHeight: '600px'
                }}
              >
                {content}
              </pre>
            )}

            {/* PDF */}
            {isPDF && (
              <div className="w-full" style={{ height: '700px' }}>
                <iframe
                  sandbox="allow-same-origin"
                  src={`${API_BASE}/knowledge-base/${article.id}/content`}
                  title={article.title}
                  className="w-full h-full rounded"
                  style={{
                    border: '1px solid rgba(14, 165, 233, 0.3)',
                    background: 'rgba(15, 23, 42, 0.8)'
                  }}
                >
                  <div className="text-center py-12">
                    <File className="w-16 h-16 mx-auto mb-4" style={{ color: '#EF4444' }} />
                    <p className="mb-4" style={{ color: '#94A3B8' }}>
                      Your browser doesn't support PDF preview. Click the download button to view this file.
                    </p>
                    <button onClick={handleDownload} className="intel-button intel-button-success">
                      <Download className="w-4 h-4 mr-2" />
                      Download PDF
                    </button>
                  </div>
                </iframe>
              </div>
            )}

            {/* Images */}
            {isImage && (
              <div className="text-center">
                <img
                  src={`${API_BASE}/knowledge-base/${article.id}/content`}
                  alt={article.title}
                  className="max-w-full h-auto rounded"
                  style={{ border: '1px solid rgba(14, 165, 233, 0.3)' }}
                />
              </div>
            )}

            {/* Other file types */}
            {!isMarkdown && !isText && !isPDF && !isImage && (
              <div className="text-center py-12">
                <File className="w-16 h-16 mx-auto mb-4" style={{ color: '#94A3B8' }} />
                <p className="mb-4" style={{ color: '#94A3B8' }}>
                  Preview not available for this file type.
                </p>
                <button onClick={handleDownload} className="intel-button intel-button-success">
                  <Download className="w-4 h-4 mr-2" />
                  Download File
                </button>
              </div>
            )}
          </>
        )}
      </div>
    </div>
  );
}