/**
 * Sequence display panel for a selected chain
 * Shows sequence length and sequence with copy/download features
 */
import React, { useState } from 'react';
import { ChainMetadata } from '../../../types/protein';
import { formatText, formatNumber } from '../../../utils/format';

interface SequencePanelProps {
  metadata: ChainMetadata | null;
  isLoading?: boolean;
}

const SequencePanel: React.FC<SequencePanelProps> = ({ metadata, isLoading }) => {
  const [copied, setCopied] = useState(false);
  const [showAll, setShowAll] = useState(false);

  const sequence = metadata?.polymer_entity?.seq_can;
  const sequenceLength = metadata?.polymer_entity?.sequence_length;

  // Format sequence with line breaks every 60 chars
  const formatSequence = (seq: string): string[] => {
    if (!seq) return [];
    const lines = [];
    for (let i = 0; i < seq.length; i += 60) {
      lines.push(seq.substring(i, i + 60));
    }
    return lines;
  };

  const handleCopy = async () => {
    if (sequence) {
      try {
        await navigator.clipboard.writeText(sequence);
        setCopied(true);
        setTimeout(() => setCopied(false), 2000);
      } catch (err) {
        console.error('Failed to copy:', err);
      }
    }
  };

  const handleDownload = () => {
    if (!sequence || !metadata) return;

    const pdbId = formatText(metadata.pdb_id || metadata.entry?.rcsb_id, 'unknown');
    const chainId = formatText(metadata.chain_id || metadata.polymer_entity_instance?.auth_asym_id, 'X');
    const title = formatText(metadata.entry?.title, 'Unknown protein');
    
    const fasta = `>${pdbId}:${chainId} ${title}\n${sequence}`;
    const blob = new Blob([fasta], { type: 'text/plain' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = `${pdbId}_${chainId}.fasta`;
    a.click();
    URL.revokeObjectURL(url);
  };

  if (isLoading) {
    return (
      <section className="space-y-4">
        <h3 className="text-xl font-semibold text-slate-900">Amino Acid Sequence</h3>
        <div className="text-center py-10 text-slate-600">Loading sequence...</div>
      </section>
    );
  }

  if (!sequence) {
    return (
      <section className="space-y-4">
        <h3 className="text-xl font-semibold text-slate-900">Amino Acid Sequence</h3>
        <div className="text-center py-10 text-slate-600">No sequence data available</div>
      </section>
    );
  }

  const lines = formatSequence(sequence);
  const displayLines = showAll ? lines : lines.slice(0, 10);
  const hasMore = lines.length > 10;
  const formattedLength = formatNumber(sequenceLength, { decimals: 0 });

  return (
    <section className="space-y-4">
      {/* Header + Actions */}
      <div className="flex justify-between items-start">
        <div>
          <h3 className="text-xl font-semibold text-slate-900 mb-1">Amino Acid Sequence</h3>
          {formattedLength !== '—' && (
            <div className="text-sm text-slate-600">
              <span className="font-medium">{formattedLength}</span> residues
            </div>
          )}
        </div>
        <div className="flex gap-2">
          <button
            className="inline-flex items-center gap-1.5 px-3 py-1.5 border border-gray-300 text-slate-900 font-medium rounded-lg hover:bg-slate-50 transition-colors text-xs"
            onClick={handleCopy}
            title="Copy to clipboard"
          >
            {copied ? '✓' : '📋'}
          </button>
          <button
            className="inline-flex items-center gap-1.5 px-3 py-1.5 bg-slate-900 text-white font-medium rounded-lg hover:bg-slate-800 transition-colors text-xs"
            onClick={handleDownload}
            title="Download FASTA"
          >
            ⬇ FASTA
          </button>
        </div>
      </div>
      
      {/* Sequence Display */}
      <div className="bg-slate-50 border border-slate-200 rounded-lg p-4 font-mono text-xs max-h-80 overflow-y-auto overflow-x-hidden">
        {displayLines.map((line, idx) => (
          <div key={idx} className="flex mb-1 leading-relaxed">
            <span className="text-gray-400 mr-4 min-w-[50px] shrink-0 text-right select-none">{idx * 60 + 1}</span>
            <span className="text-gray-800 tracking-wide wrap-anywhere">{line}</span>
          </div>
        ))}
      </div>

      {hasMore && (
        <div className="text-center">
          <button
            className="inline-flex items-center gap-2 px-4 py-2 border border-gray-300 text-slate-900 font-medium rounded-lg hover:bg-slate-50 transition-colors text-sm"
            onClick={() => setShowAll(!showAll)}
          >
            {showAll ? '▲ Show less' : `▼ Show all (${lines.length - 10} more lines)`}
          </button>
        </div>
      )}
    </section>
  );
};

export default SequencePanel;