import React, { useState, useEffect, useRef, useMemo } from 'react';
import CodeMirror from '@uiw/react-codemirror';
import { javascript } from '@codemirror/lang-javascript';
import { python } from '@codemirror/lang-python';
import { html } from '@codemirror/lang-html';
import { css } from '@codemirror/lang-css';
import { json } from '@codemirror/lang-json';
import { markdown } from '@codemirror/lang-markdown';
import { oneDark } from '@codemirror/theme-one-dark';
import { EditorView, showPanel, ViewPlugin } from '@codemirror/view';
import { unifiedMergeView, getChunks } from '@codemirror/merge';
import { showMinimap } from '@replit/codemirror-minimap';
import { X, Save, Download, Maximize2, Minimize2, Eye, EyeOff } from 'lucide-react';
import { api } from '../utils/api';

function CodeEditor({ file, onClose, projectPath }) {
  const [content, setContent] = useState('');
  const [loading, setLoading] = useState(true);
  const [saving, setSaving] = useState(false);
  const [isFullscreen, setIsFullscreen] = useState(false);
  const [isDarkMode, setIsDarkMode] = useState(true);
  const [saveSuccess, setSaveSuccess] = useState(false);
  const [showDiff, setShowDiff] = useState(!!file.diffInfo);
  const [wordWrap, setWordWrap] = useState(false);
  const editorRef = useRef(null);

  // Create minimap extension with chunk-based gutters
  const minimapExtension = useMemo(() => {
    if (!file.diffInfo || !showDiff) return [];

    const gutters = {};

    return [
      showMinimap.compute(['doc'], (state) => {
        // Get actual chunks from merge view
        const chunksData = getChunks(state);
        const chunks = chunksData?.chunks || [];

        // Clear previous gutters
        Object.keys(gutters).forEach(key => delete gutters[key]);

        // Mark lines that are part of chunks
        chunks.forEach(chunk => {
          // Mark the lines in the B side (current document)
          const fromLine = state.doc.lineAt(chunk.fromB).number;
          const toLine = state.doc.lineAt(Math.min(chunk.toB, state.doc.length)).number;

          for (let lineNum = fromLine; lineNum <= toLine; lineNum++) {
            gutters[lineNum] = isDarkMode ? 'rgba(34, 197, 94, 0.8)' : 'rgba(34, 197, 94, 1)';
          }
        });

        return {
          create: () => ({ dom: document.createElement('div') }),
          displayText: 'blocks',
          showOverlay: 'always',
          gutters: [gutters]
        };
      })
    ];
  }, [file.diffInfo, showDiff, isDarkMode]);

  // Create extension to scroll to first chunk on mount
  const scrollToFirstChunkExtension = useMemo(() => {
    if (!file.diffInfo || !showDiff) return [];

    return [
      ViewPlugin.fromClass(class {
        constructor(view) {
          // Delay to ensure merge view is fully initialized
          setTimeout(() => {
            const chunksData = getChunks(view.state);
            const chunks = chunksData?.chunks || [];

            if (chunks.length > 0) {
              const firstChunk = chunks[0];

              // Scroll to the first chunk
              view.dispatch({
                effects: EditorView.scrollIntoView(firstChunk.fromB, { y: 'center' })
              });
            }
          }, 100);
        }

        update() {}
        destroy() {}
      })
    ];
  }, [file.diffInfo, showDiff]);

  // Create diff navigation panel extension
  const diffNavigationPanel = useMemo(() => {
    if (!file.diffInfo || !showDiff) return [];

    const createPanel = (view) => {
      const dom = document.createElement('div');
      dom.className = 'cm-diff-navigation-panel';

      let currentIndex = 0;

      const updatePanel = () => {
        // Use getChunks API to get ALL chunks regardless of viewport
        const chunksData = getChunks(view.state);
        const chunks = chunksData?.chunks || [];
        const chunkCount = chunks.length;

        dom.innerHTML = `
          <div style="display: flex; align-items: center; gap: 8px;">
            <span style="font-weight: 500;">${chunkCount > 0 ? `${currentIndex + 1}/${chunkCount}` : '0'} changes</span>
            <button class="cm-diff-nav-btn cm-diff-nav-prev" title="Previous change" ${chunkCount === 0 ? 'disabled' : ''}>
              <svg width="16" height="16" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M5 15l7-7 7 7" />
              </svg>
            </button>
            <button class="cm-diff-nav-btn cm-diff-nav-next" title="Next change" ${chunkCount === 0 ? 'disabled' : ''}>
              <svg width="16" height="16" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7" />
              </svg>
            </button>
          </div>
        `;

        const prevBtn = dom.querySelector('.cm-diff-nav-prev');
        const nextBtn = dom.querySelector('.cm-diff-nav-next');

        prevBtn?.addEventListener('click', () => {
          if (chunks.length === 0) return;
          currentIndex = currentIndex > 0 ? currentIndex - 1 : chunks.length - 1;

          // Navigate to the chunk - use fromB which is the position in the current document
          const chunk = chunks[currentIndex];
          if (chunk) {
            // Scroll to the start of the chunk in the B side (current document)
            view.dispatch({
              effects: EditorView.scrollIntoView(chunk.fromB, { y: 'center' })
            });
          }
          updatePanel();
        });

        nextBtn?.addEventListener('click', () => {
          if (chunks.length === 0) return;
          currentIndex = currentIndex < chunks.length - 1 ? currentIndex + 1 : 0;

          // Navigate to the chunk - use fromB which is the position in the current document
          const chunk = chunks[currentIndex];
          if (chunk) {
            // Scroll to the start of the chunk in the B side (current document)
            view.dispatch({
              effects: EditorView.scrollIntoView(chunk.fromB, { y: 'center' })
            });
          }
          updatePanel();
        });
      };

      updatePanel();

      return {
        top: true,
        dom,
        update: updatePanel
      };
    };

    return [showPanel.of(createPanel)];
  }, [file.diffInfo, showDiff]);

  // Get language extension based on file extension
  const getLanguageExtension = (filename) => {
    const ext = filename.split('.').pop()?.toLowerCase();
    switch (ext) {
      case 'js':
      case 'jsx':
      case 'ts':
      case 'tsx':
        return [javascript({ jsx: true, typescript: ext.includes('ts') })];
      case 'py':
        return [python()];
      case 'html':
      case 'htm':
        return [html()];
      case 'css':
      case 'scss':
      case 'less':
        return [css()];
      case 'json':
        return [json()];
      case 'md':
      case 'markdown':
        return [markdown()];
      default:
        return [];
    }
  };

  // Load file content
  useEffect(() => {
    const loadFileContent = async () => {
      try {
        setLoading(true);

        // If we have diffInfo with both old and new content, we can show the diff directly
        // This handles both GitPanel (full content) and ChatInterface (full content from API)
        if (file.diffInfo && file.diffInfo.new_string !== undefined && file.diffInfo.old_string !== undefined) {
          // Use the new_string as the content to display
          // The unifiedMergeView will compare it against old_string
          setContent(file.diffInfo.new_string);
          setLoading(false);
          return;
        }

        // Otherwise, load from disk
        const response = await api.readFile(file.projectName, file.path);

        if (!response.ok) {
          throw new Error(`Failed to load file: ${response.status} ${response.statusText}`);
        }

        const data = await response.json();
        setContent(data.content);
      } catch (error) {
        console.error('Error loading file:', error);
        setContent(`// Error loading file: ${error.message}\n// File: ${file.name}\n// Path: ${file.path}`);
      } finally {
        setLoading(false);
      }
    };

    loadFileContent();
  }, [file, projectPath]);

  const handleSave = async () => {
    setSaving(true);
    try {
      console.log('Saving file:', {
        projectName: file.projectName,
        path: file.path,
        contentLength: content?.length
      });

      const response = await api.saveFile(file.projectName, file.path, content);

      console.log('Save response:', {
        status: response.status,
        ok: response.ok,
        contentType: response.headers.get('content-type')
      });

      if (!response.ok) {
        const contentType = response.headers.get('content-type');
        if (contentType && contentType.includes('application/json')) {
          const errorData = await response.json();
          throw new Error(errorData.error || `Save failed: ${response.status}`);
        } else {
          const textError = await response.text();
          console.error('Non-JSON error response:', textError);
          throw new Error(`Save failed: ${response.status} ${response.statusText}`);
        }
      }

      const result = await response.json();
      console.log('Save successful:', result);

      setSaveSuccess(true);
      setTimeout(() => setSaveSuccess(false), 2000);

    } catch (error) {
      console.error('Error saving file:', error);
      alert(`Error saving file: ${error.message}`);
    } finally {
      setSaving(false);
    }
  };

  const handleDownload = () => {
    const blob = new Blob([content], { type: 'text/plain' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = file.name;
    document.body.appendChild(a);
    a.click();
    document.body.removeChild(a);
    URL.revokeObjectURL(url);
  };

  const toggleFullscreen = () => {
    setIsFullscreen(!isFullscreen);
  };

  // Handle keyboard shortcuts
  useEffect(() => {
    const handleKeyDown = (e) => {
      if (e.ctrlKey || e.metaKey) {
        if (e.key === 's') {
          e.preventDefault();
          handleSave();
        } else if (e.key === 'Escape') {
          e.preventDefault();
          onClose();
        }
      }
    };

    document.addEventListener('keydown', handleKeyDown);
    return () => document.removeEventListener('keydown', handleKeyDown);
  }, [content]);

  if (loading) {
    return (
      <>
        <style>
          {`
            .code-editor-loading {
              background-color: ${isDarkMode ? '#111827' : '#ffffff'} !important;
            }
            .code-editor-loading:hover {
              background-color: ${isDarkMode ? '#111827' : '#ffffff'} !important;
            }
          `}
        </style>
        <div className="fixed inset-0 z-50 md:bg-black/50 md:flex md:items-center md:justify-center">
          <div className="code-editor-loading w-full h-full md:rounded-lg md:w-auto md:h-auto p-8 flex items-center justify-center">
            <div className="flex items-center gap-3">
              <div className="animate-spin rounded-full h-6 w-6 border-b-2 border-blue-600"></div>
              <span className="text-gray-900 dark:text-white">Loading {file.name}...</span>
            </div>
          </div>
        </div>
      </>
    );
  }

  return (
    <>
      <style>
        {`
          /* Light background for full line changes */
          .cm-deletedChunk {
            background-color: ${isDarkMode ? 'rgba(239, 68, 68, 0.15)' : 'rgba(255, 235, 235, 1)'} !important;
            border-left: 3px solid ${isDarkMode ? 'rgba(239, 68, 68, 0.6)' : 'rgb(239, 68, 68)'} !important;
            padding-left: 4px !important;
          }

          .cm-insertedChunk {
            background-color: ${isDarkMode ? 'rgba(34, 197, 94, 0.15)' : 'rgba(230, 255, 237, 1)'} !important;
            border-left: 3px solid ${isDarkMode ? 'rgba(34, 197, 94, 0.6)' : 'rgb(34, 197, 94)'} !important;
            padding-left: 4px !important;
          }

          /* Override linear-gradient underline and use solid darker background for partial changes */
          .cm-editor.cm-merge-b .cm-changedText {
            background: ${isDarkMode ? 'rgba(34, 197, 94, 0.4)' : 'rgba(34, 197, 94, 0.3)'} !important;
            padding-top: 2px !important;
            padding-bottom: 2px !important;
            margin-top: -2px !important;
            margin-bottom: -2px !important;
          }

          .cm-editor .cm-deletedChunk .cm-changedText {
            background: ${isDarkMode ? 'rgba(239, 68, 68, 0.4)' : 'rgba(239, 68, 68, 0.3)'} !important;
            padding-top: 2px !important;
            padding-bottom: 2px !important;
            margin-top: -2px !important;
            margin-bottom: -2px !important;
          }

          /* Minimap gutter styling */
          .cm-gutter.cm-gutter-minimap {
            background-color: ${isDarkMode ? '#1e1e1e' : '#f5f5f5'};
          }

          /* Diff navigation panel styling */
          .cm-diff-navigation-panel {
            padding: 8px 12px;
            background-color: ${isDarkMode ? '#1f2937' : '#ffffff'};
            border-bottom: 1px solid ${isDarkMode ? '#374151' : '#e5e7eb'};
            color: ${isDarkMode ? '#d1d5db' : '#374151'};
            font-size: 14px;
          }

          .cm-diff-nav-btn {
            padding: 4px;
            background: transparent;
            border: none;
            cursor: pointer;
            border-radius: 4px;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            color: inherit;
          }

          .cm-diff-nav-btn:hover {
            background-color: ${isDarkMode ? '#374151' : '#f3f4f6'};
          }

          .cm-diff-nav-btn:disabled {
            opacity: 0.5;
            cursor: not-allowed;
          }
        `}
      </style>
      <div className={`fixed inset-0 z-50 ${
          // Mobile: native fullscreen, Desktop: modal with backdrop
          'md:bg-black/50 md:flex md:items-center md:justify-center md:p-4'
        } ${isFullscreen ? 'md:p-0' : ''}`}>
        <div className={`bg-white shadow-2xl flex flex-col ${
        // Mobile: always fullscreen, Desktop: modal sizing
        'w-full h-full md:rounded-lg md:shadow-2xl' +
        (isFullscreen ? ' md:w-full md:h-full md:rounded-none' : ' md:w-full md:max-w-6xl md:h-[80vh] md:max-h-[80vh]')
      }`}>
        {/* Header */}
        <div className="flex items-center justify-between p-4 border-b border-gray-200 flex-shrink-0 min-w-0">
          <div className="flex items-center gap-3 min-w-0 flex-1">
            <div className="w-8 h-8 bg-blue-600 rounded flex items-center justify-center flex-shrink-0">
              <span className="text-white text-sm font-mono">
                {file.name.split('.').pop()?.toUpperCase() || 'FILE'}
              </span>
            </div>
            <div className="min-w-0 flex-1">
              <div className="flex items-center gap-2 min-w-0">
                <h3 className="font-medium text-gray-900 truncate">{file.name}</h3>
                {file.diffInfo && (
                  <span className="text-xs bg-blue-100 text-blue-600 px-2 py-1 rounded whitespace-nowrap">
                    📝 Has changes
                  </span>
                )}
              </div>
              <p className="text-sm text-gray-500 truncate">{file.path}</p>
            </div>
          </div>

          <div className="flex items-center gap-1 md:gap-2 flex-shrink-0">
            {file.diffInfo && (
              <button
                onClick={() => setShowDiff(!showDiff)}
                className="p-2 md:p-2 text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white rounded-md hover:bg-gray-100 dark:hover:bg-gray-800 min-w-[44px] min-h-[44px] md:min-w-0 md:min-h-0 flex items-center justify-center"
                title={showDiff ? "Hide diff highlighting" : "Show diff highlighting"}
              >
                {showDiff ? <EyeOff className="w-5 h-5 md:w-4 md:h-4" /> : <Eye className="w-5 h-5 md:w-4 md:h-4" />}
              </button>
            )}

            <button
              onClick={() => setWordWrap(!wordWrap)}
              className={`p-2 md:p-2 rounded-md hover:bg-gray-100 min-w-[44px] min-h-[44px] md:min-w-0 md:min-h-0 flex items-center justify-center ${
                wordWrap
                  ? 'text-blue-600 bg-blue-50'
                  : 'text-gray-600 hover:text-gray-900'
              }`}
              title={wordWrap ? 'Disable word wrap' : 'Enable word wrap'}
            >
              <span className="text-sm md:text-xs font-mono font-bold">↵</span>
            </button>

            <button
              onClick={() => setIsDarkMode(!isDarkMode)}
              className="p-2 md:p-2 text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white rounded-md hover:bg-gray-100 dark:hover:bg-gray-800 min-w-[44px] min-h-[44px] md:min-w-0 md:min-h-0 flex items-center justify-center"
              title="Toggle theme"
            >
              <span className="text-lg md:text-base">{isDarkMode ? '☀️' : '🌙'}</span>
            </button>

            <button
              onClick={handleDownload}
              className="p-2 md:p-2 text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white rounded-md hover:bg-gray-100 dark:hover:bg-gray-800 min-w-[44px] min-h-[44px] md:min-w-0 md:min-h-0 flex items-center justify-center"
              title="Download file"
            >
              <Download className="w-5 h-5 md:w-4 md:h-4" />
            </button>

            <button
              onClick={handleSave}
              disabled={saving}
              className={`px-3 py-2 text-white rounded-md disabled:opacity-50 flex items-center gap-2 transition-colors min-h-[44px] md:min-h-0 ${
                saveSuccess
                  ? 'bg-green-600 hover:bg-green-700'
                  : 'bg-blue-600 hover:bg-blue-700'
              }`}
            >
              {saveSuccess ? (
                <>
                  <svg className="w-5 h-5 md:w-4 md:h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                    <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M5 13l4 4L19 7" />
                  </svg>
                  <span className="hidden sm:inline">Saved!</span>
                </>
              ) : (
                <>
                  <Save className="w-5 h-5 md:w-4 md:h-4" />
                  <span className="hidden sm:inline">{saving ? 'Saving...' : 'Save'}</span>
                </>
              )}
            </button>

            <button
              onClick={toggleFullscreen}
              className="hidden md:flex p-2 text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white rounded-md hover:bg-gray-100 dark:hover:bg-gray-800 items-center justify-center"
              title={isFullscreen ? 'Exit fullscreen' : 'Fullscreen'}
            >
              {isFullscreen ? <Minimize2 className="w-4 h-4" /> : <Maximize2 className="w-4 h-4" />}
            </button>

            <button
              onClick={onClose}
              className="p-2 md:p-2 text-gray-600 dark:text-gray-400 hover:text-gray-900 dark:hover:text-white rounded-md hover:bg-gray-100 dark:hover:bg-gray-800 min-w-[44px] min-h-[44px] md:min-w-0 md:min-h-0 flex items-center justify-center"
              title="Close"
            >
              <X className="w-6 h-6 md:w-4 md:h-4" />
            </button>
          </div>
        </div>

        {/* Editor */}
        <div className="flex-1 overflow-hidden">
          <CodeMirror
            ref={editorRef}
            value={content}
            onChange={setContent}
            extensions={[
              ...getLanguageExtension(file.name),
              ...(file.diffInfo && showDiff && file.diffInfo.old_string !== undefined
                ? [
                    unifiedMergeView({
                      original: file.diffInfo.old_string,
                      mergeControls: false,
                      highlightChanges: true,
                      syntaxHighlightDeletions: false,
                      gutter: true
                      // NOTE: NO collapseUnchanged - this shows the full file!
                    }),
                    ...minimapExtension,
                    ...scrollToFirstChunkExtension,
                    ...diffNavigationPanel
                  ]
                : []),
              ...(wordWrap ? [EditorView.lineWrapping] : [])
            ]}
            theme={isDarkMode ? oneDark : undefined}
            height="100%"
            style={{
              fontSize: '14px',
              height: '100%',
            }}
            basicSetup={{
              lineNumbers: true,
              foldGutter: true,
              dropCursor: false,
              allowMultipleSelections: false,
              indentOnInput: true,
              bracketMatching: true,
              closeBrackets: true,
              autocompletion: true,
              highlightSelectionMatches: true,
              searchKeymap: true,
            }}
          />
        </div>

        {/* Footer */}
        <div className="flex items-center justify-between p-3 border-t border-gray-200 dark:border-gray-700 bg-gray-50 dark:bg-gray-800 flex-shrink-0">
          <div className="flex items-center gap-4 text-sm text-gray-600 dark:text-gray-400">
            <span>Lines: {content.split('\n').length}</span>
            <span>Characters: {content.length}</span>
            <span>Language: {file.name.split('.').pop()?.toUpperCase() || 'Text'}</span>
          </div>

          <div className="text-sm text-gray-500 dark:text-gray-400">
            Press Ctrl+S to save • Esc to close
          </div>
        </div>
      </div>
    </div>
    </>
  );
}

export default CodeEditor;