/**
 * @license
 * Copyright 2025 Google LLC
 * SPDX-License-Identifier: Apache-2.0
 */

import { describe, it, expect, beforeEach } from 'vitest';
import { renderHook, act } from '@testing-library/react';
import {
  useTextBuffer,
  Viewport,
  TextBuffer,
  offsetToLogicalPos,
} from './text-buffer.js';

// Helper to get the state from the hook
const getBufferState = (result: { current: TextBuffer }) => ({
  text: result.current.text,
  lines: [...result.current.lines], // Clone for safety
  cursor: [...result.current.cursor] as [number, number],
  allVisualLines: [...result.current.allVisualLines],
  viewportVisualLines: [...result.current.viewportVisualLines],
  visualCursor: [...result.current.visualCursor] as [number, number],
  visualScrollRow: result.current.visualScrollRow,
  preferredCol: result.current.preferredCol,
});

describe('useTextBuffer', () => {
  let viewport: Viewport;

  beforeEach(() => {
    viewport = { width: 10, height: 3 }; // Default viewport for tests
  });

  describe('Initialization', () => {
    it('should initialize with empty text and cursor at (0,0) by default', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const state = getBufferState(result);
      expect(state.text).toBe('');
      expect(state.lines).toEqual(['']);
      expect(state.cursor).toEqual([0, 0]);
      expect(state.allVisualLines).toEqual(['']);
      expect(state.viewportVisualLines).toEqual(['']);
      expect(state.visualCursor).toEqual([0, 0]);
      expect(state.visualScrollRow).toBe(0);
    });

    it('should initialize with provided initialText', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'hello',
          viewport,
          isValidPath: () => false,
        }),
      );
      const state = getBufferState(result);
      expect(state.text).toBe('hello');
      expect(state.lines).toEqual(['hello']);
      expect(state.cursor).toEqual([0, 0]); // Default cursor if offset not given
      expect(state.allVisualLines).toEqual(['hello']);
      expect(state.viewportVisualLines).toEqual(['hello']);
      expect(state.visualCursor).toEqual([0, 0]);
    });

    it('should initialize with initialText and initialCursorOffset', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'hello\nworld',
          initialCursorOffset: 7, // Should be at 'o' in 'world'
          viewport,
          isValidPath: () => false,
        }),
      );
      const state = getBufferState(result);
      expect(state.text).toBe('hello\nworld');
      expect(state.lines).toEqual(['hello', 'world']);
      expect(state.cursor).toEqual([1, 1]); // Logical cursor at 'o' in "world"
      expect(state.allVisualLines).toEqual(['hello', 'world']);
      expect(state.viewportVisualLines).toEqual(['hello', 'world']);
      expect(state.visualCursor[0]).toBe(1); // On the second visual line
      expect(state.visualCursor[1]).toBe(1); // At 'o' in "world"
    });

    it('should wrap visual lines', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'The quick brown fox jumps over the lazy dog.',
          initialCursorOffset: 2, // After '好'
          viewport: { width: 15, height: 4 },
          isValidPath: () => false,
        }),
      );
      const state = getBufferState(result);
      expect(state.allVisualLines).toEqual([
        'The quick',
        'brown fox',
        'jumps over the',
        'lazy dog.',
      ]);
    });

    it('should wrap visual lines with multiple spaces', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'The  quick  brown fox    jumps over the lazy dog.',
          viewport: { width: 15, height: 4 },
          isValidPath: () => false,
        }),
      );
      const state = getBufferState(result);
      // Including multiple spaces at the end of the lines like this is
      // consistent with Google docs behavior and makes it intuitive to edit
      // the spaces as needed.
      expect(state.allVisualLines).toEqual([
        'The  quick ',
        'brown fox   ',
        'jumps over the',
        'lazy dog.',
      ]);
    });

    it('should wrap visual lines even without spaces', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: '123456789012345ABCDEFG', // 4 chars, 12 bytes
          viewport: { width: 15, height: 2 },
          isValidPath: () => false,
        }),
      );
      const state = getBufferState(result);
      // Including multiple spaces at the end of the lines like this is
      // consistent with Google docs behavior and makes it intuitive to edit
      // the spaces as needed.
      expect(state.allVisualLines).toEqual(['123456789012345', 'ABCDEFG']);
    });

    it('should initialize with multi-byte unicode characters and correct cursor offset', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: '你好世界', // 4 chars, 12 bytes
          initialCursorOffset: 2, // After '好'
          viewport: { width: 5, height: 2 },
          isValidPath: () => false,
        }),
      );
      const state = getBufferState(result);
      expect(state.text).toBe('你好世界');
      expect(state.lines).toEqual(['你好世界']);
      expect(state.cursor).toEqual([0, 2]);
      // Visual: "你好" (width 4), "世"界" (width 4) with viewport width 5
      expect(state.allVisualLines).toEqual(['你好', '世界']);
      expect(state.visualCursor).toEqual([1, 0]);
    });
  });

  describe('Basic Editing', () => {
    it('insert: should insert a character and update cursor', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      act(() => result.current.insert('a'));
      let state = getBufferState(result);
      expect(state.text).toBe('a');
      expect(state.cursor).toEqual([0, 1]);
      expect(state.visualCursor).toEqual([0, 1]);

      act(() => result.current.insert('b'));
      state = getBufferState(result);
      expect(state.text).toBe('ab');
      expect(state.cursor).toEqual([0, 2]);
      expect(state.visualCursor).toEqual([0, 2]);
    });

    it('newline: should create a new line and move cursor', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'ab',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end')); // cursor at [0,2]
      act(() => result.current.newline());
      const state = getBufferState(result);
      expect(state.text).toBe('ab\n');
      expect(state.lines).toEqual(['ab', '']);
      expect(state.cursor).toEqual([1, 0]);
      expect(state.allVisualLines).toEqual(['ab', '']);
      expect(state.viewportVisualLines).toEqual(['ab', '']); // viewport height 3
      expect(state.visualCursor).toEqual([1, 0]); // On the new visual line
    });

    it('backspace: should delete char to the left or merge lines', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'a\nb',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => {
        result.current.move('down');
      });
      act(() => {
        result.current.move('end'); // cursor to [1,1] (end of 'b')
      });
      act(() => result.current.backspace()); // delete 'b'
      let state = getBufferState(result);
      expect(state.text).toBe('a\n');
      expect(state.cursor).toEqual([1, 0]);

      act(() => result.current.backspace()); // merge lines
      state = getBufferState(result);
      expect(state.text).toBe('a');
      expect(state.cursor).toEqual([0, 1]); // cursor after 'a'
      expect(state.allVisualLines).toEqual(['a']);
      expect(state.viewportVisualLines).toEqual(['a']);
      expect(state.visualCursor).toEqual([0, 1]);
    });

    it('del: should delete char to the right or merge lines', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'a\nb',
          viewport,
          isValidPath: () => false,
        }),
      );
      // cursor at [0,0]
      act(() => result.current.del()); // delete 'a'
      let state = getBufferState(result);
      expect(state.text).toBe('\nb');
      expect(state.cursor).toEqual([0, 0]);

      act(() => result.current.del()); // merge lines (deletes newline)
      state = getBufferState(result);
      expect(state.text).toBe('b');
      expect(state.cursor).toEqual([0, 0]);
      expect(state.allVisualLines).toEqual(['b']);
      expect(state.viewportVisualLines).toEqual(['b']);
      expect(state.visualCursor).toEqual([0, 0]);
    });
  });

  describe('Drag and Drop File Paths', () => {
    it('should prepend @ to a valid file path on insert', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => true }),
      );
      const filePath = '/path/to/a/valid/file.txt';
      act(() => result.current.insert(filePath));
      expect(getBufferState(result).text).toBe(`@${filePath}`);
    });

    it('should not prepend @ to an invalid file path on insert', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const notAPath = 'this is just some long text';
      act(() => result.current.insert(notAPath));
      expect(getBufferState(result).text).toBe(notAPath);
    });

    it('should handle quoted paths', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => true }),
      );
      const filePath = "'/path/to/a/valid/file.txt'";
      act(() => result.current.insert(filePath));
      expect(getBufferState(result).text).toBe(`@/path/to/a/valid/file.txt`);
    });

    it('should not prepend @ to short text that is not a path', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => true }),
      );
      const shortText = 'ab';
      act(() => result.current.insert(shortText));
      expect(getBufferState(result).text).toBe(shortText);
    });
  });

  describe('Cursor Movement', () => {
    it('move: left/right should work within and across visual lines (due to wrapping)', () => {
      // Text: "long line1next line2" (20 chars)
      // Viewport width 5. Word wrapping should produce:
      // "long " (5)
      // "line1" (5)
      // "next " (5)
      // "line2" (5)
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'long line1next line2', // Corrected: was 'long line1next line2'
          viewport: { width: 5, height: 4 },
          isValidPath: () => false,
        }),
      );
      // Initial cursor [0,0] logical, visual [0,0] ("l" of "long ")

      act(() => result.current.move('right')); // visual [0,1] ("o")
      expect(getBufferState(result).visualCursor).toEqual([0, 1]);
      act(() => result.current.move('right')); // visual [0,2] ("n")
      act(() => result.current.move('right')); // visual [0,3] ("g")
      act(() => result.current.move('right')); // visual [0,4] (" ")
      expect(getBufferState(result).visualCursor).toEqual([0, 4]);

      act(() => result.current.move('right')); // visual [1,0] ("l" of "line1")
      expect(getBufferState(result).visualCursor).toEqual([1, 0]);
      expect(getBufferState(result).cursor).toEqual([0, 5]); // logical cursor

      act(() => result.current.move('left')); // visual [0,4] (" " of "long ")
      expect(getBufferState(result).visualCursor).toEqual([0, 4]);
      expect(getBufferState(result).cursor).toEqual([0, 4]); // logical cursor
    });

    it('move: up/down should preserve preferred visual column', () => {
      const text = 'abcde\nxy\n12345';
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: text,
          viewport,
          isValidPath: () => false,
        }),
      );
      expect(result.current.allVisualLines).toEqual(['abcde', 'xy', '12345']);
      // Place cursor at the end of "abcde" -> logical [0,5]
      act(() => {
        result.current.move('home'); // to [0,0]
      });
      for (let i = 0; i < 5; i++) {
        act(() => {
          result.current.move('right'); // to [0,5]
        });
      }
      expect(getBufferState(result).cursor).toEqual([0, 5]);
      expect(getBufferState(result).visualCursor).toEqual([0, 5]);

      // Set preferredCol by moving up then down to the same spot, then test.
      act(() => {
        result.current.move('down'); // to xy, logical [1,2], visual [1,2], preferredCol should be 5
      });
      let state = getBufferState(result);
      expect(state.cursor).toEqual([1, 2]); // Logical cursor at end of 'xy'
      expect(state.visualCursor).toEqual([1, 2]); // Visual cursor at end of 'xy'
      expect(state.preferredCol).toBe(5);

      act(() => result.current.move('down')); // to '12345', preferredCol=5.
      state = getBufferState(result);
      expect(state.cursor).toEqual([2, 5]); // Logical cursor at end of '12345'
      expect(state.visualCursor).toEqual([2, 5]); // Visual cursor at end of '12345'
      expect(state.preferredCol).toBe(5); // Preferred col is maintained

      act(() => result.current.move('left')); // preferredCol should reset
      state = getBufferState(result);
      expect(state.preferredCol).toBe(null);
    });

    it('move: home/end should go to visual line start/end', () => {
      const initialText = 'line one\nsecond line';
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText,
          viewport: { width: 5, height: 5 },
          isValidPath: () => false,
        }),
      );
      expect(result.current.allVisualLines).toEqual([
        'line',
        'one',
        'secon',
        'd',
        'line',
      ]);
      // Initial cursor [0,0] (start of "line")
      act(() => result.current.move('down')); // visual cursor from [0,0] to [1,0] ("o" of "one")
      act(() => result.current.move('right')); // visual cursor to [1,1] ("n" of "one")
      expect(getBufferState(result).visualCursor).toEqual([1, 1]);

      act(() => result.current.move('home')); // visual cursor to [1,0] (start of "one")
      expect(getBufferState(result).visualCursor).toEqual([1, 0]);

      act(() => result.current.move('end')); // visual cursor to [1,3] (end of "one")
      expect(getBufferState(result).visualCursor).toEqual([1, 3]); // "one" is 3 chars
    });
  });

  describe('Visual Layout & Viewport', () => {
    it('should wrap long lines correctly into visualLines', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'This is a very long line of text.', // 33 chars
          viewport: { width: 10, height: 5 },
          isValidPath: () => false,
        }),
      );
      const state = getBufferState(result);
      // Expected visual lines with word wrapping (viewport width 10):
      // "This is a"
      // "very long"
      // "line of"
      // "text."
      expect(state.allVisualLines.length).toBe(4);
      expect(state.allVisualLines[0]).toBe('This is a');
      expect(state.allVisualLines[1]).toBe('very long');
      expect(state.allVisualLines[2]).toBe('line of');
      expect(state.allVisualLines[3]).toBe('text.');
    });

    it('should update visualScrollRow when visualCursor moves out of viewport', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'l1\nl2\nl3\nl4\nl5',
          viewport: { width: 5, height: 3 }, // Can show 3 visual lines
          isValidPath: () => false,
        }),
      );
      // Initial: l1, l2, l3 visible. visualScrollRow = 0. visualCursor = [0,0]
      expect(getBufferState(result).visualScrollRow).toBe(0);
      expect(getBufferState(result).allVisualLines).toEqual([
        'l1',
        'l2',
        'l3',
        'l4',
        'l5',
      ]);
      expect(getBufferState(result).viewportVisualLines).toEqual([
        'l1',
        'l2',
        'l3',
      ]);

      act(() => result.current.move('down')); // vc=[1,0]
      act(() => result.current.move('down')); // vc=[2,0] (l3)
      expect(getBufferState(result).visualScrollRow).toBe(0);

      act(() => result.current.move('down')); // vc=[3,0] (l4) - scroll should happen
      // Now: l2, l3, l4 visible. visualScrollRow = 1.
      let state = getBufferState(result);
      expect(state.visualScrollRow).toBe(1);
      expect(state.allVisualLines).toEqual(['l1', 'l2', 'l3', 'l4', 'l5']);
      expect(state.viewportVisualLines).toEqual(['l2', 'l3', 'l4']);
      expect(state.visualCursor).toEqual([3, 0]);

      act(() => result.current.move('up')); // vc=[2,0] (l3)
      act(() => result.current.move('up')); // vc=[1,0] (l2)
      expect(getBufferState(result).visualScrollRow).toBe(1);

      act(() => result.current.move('up')); // vc=[0,0] (l1) - scroll up
      // Now: l1, l2, l3 visible. visualScrollRow = 0
      state = getBufferState(result); // Assign to the existing `state` variable
      expect(state.visualScrollRow).toBe(0);
      expect(state.allVisualLines).toEqual(['l1', 'l2', 'l3', 'l4', 'l5']);
      expect(state.viewportVisualLines).toEqual(['l1', 'l2', 'l3']);
      expect(state.visualCursor).toEqual([0, 0]);
    });
  });

  describe('Undo/Redo', () => {
    it('should undo and redo an insert operation', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      act(() => result.current.insert('a'));
      expect(getBufferState(result).text).toBe('a');

      act(() => result.current.undo());
      expect(getBufferState(result).text).toBe('');
      expect(getBufferState(result).cursor).toEqual([0, 0]);

      act(() => result.current.redo());
      expect(getBufferState(result).text).toBe('a');
      expect(getBufferState(result).cursor).toEqual([0, 1]);
    });

    it('should undo and redo a newline operation', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'test',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end'));
      act(() => result.current.newline());
      expect(getBufferState(result).text).toBe('test\n');

      act(() => result.current.undo());
      expect(getBufferState(result).text).toBe('test');
      expect(getBufferState(result).cursor).toEqual([0, 4]);

      act(() => result.current.redo());
      expect(getBufferState(result).text).toBe('test\n');
      expect(getBufferState(result).cursor).toEqual([1, 0]);
    });
  });

  describe('Unicode Handling', () => {
    it('insert: should correctly handle multi-byte unicode characters', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      act(() => result.current.insert('你好'));
      const state = getBufferState(result);
      expect(state.text).toBe('你好');
      expect(state.cursor).toEqual([0, 2]); // Cursor is 2 (char count)
      expect(state.visualCursor).toEqual([0, 2]);
    });

    it('backspace: should correctly delete multi-byte unicode characters', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: '你好',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end')); // cursor at [0,2]
      act(() => result.current.backspace()); // delete '好'
      let state = getBufferState(result);
      expect(state.text).toBe('你');
      expect(state.cursor).toEqual([0, 1]);

      act(() => result.current.backspace()); // delete '你'
      state = getBufferState(result);
      expect(state.text).toBe('');
      expect(state.cursor).toEqual([0, 0]);
    });

    it('move: left/right should treat multi-byte chars as single units for visual cursor', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: '🐶🐱',
          viewport: { width: 5, height: 1 },
          isValidPath: () => false,
        }),
      );
      // Initial: visualCursor [0,0]
      act(() => result.current.move('right')); // visualCursor [0,1] (after 🐶)
      let state = getBufferState(result);
      expect(state.cursor).toEqual([0, 1]);
      expect(state.visualCursor).toEqual([0, 1]);

      act(() => result.current.move('right')); // visualCursor [0,2] (after 🐱)
      state = getBufferState(result);
      expect(state.cursor).toEqual([0, 2]);
      expect(state.visualCursor).toEqual([0, 2]);

      act(() => result.current.move('left')); // visualCursor [0,1] (before 🐱 / after 🐶)
      state = getBufferState(result);
      expect(state.cursor).toEqual([0, 1]);
      expect(state.visualCursor).toEqual([0, 1]);
    });
  });

  describe('handleInput', () => {
    it('should insert printable characters', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      act(() => result.current.handleInput('h', {}));
      act(() => result.current.handleInput('i', {}));
      expect(getBufferState(result).text).toBe('hi');
    });

    it('should handle "Enter" key as newline', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      act(() => result.current.handleInput(undefined, { return: true }));
      expect(getBufferState(result).lines).toEqual(['', '']);
    });

    it('should handle "Backspace" key', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'a',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end'));
      act(() => result.current.handleInput(undefined, { backspace: true }));
      expect(getBufferState(result).text).toBe('');
    });

    it('should handle multiple delete characters in one input', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'abcde',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end')); // cursor at the end
      expect(getBufferState(result).cursor).toEqual([0, 5]);

      act(() => {
        result.current.applyOperations([
          { type: 'backspace' },
          { type: 'backspace' },
          { type: 'backspace' },
        ]);
      });
      expect(getBufferState(result).text).toBe('ab');
      expect(getBufferState(result).cursor).toEqual([0, 2]);
    });

    it('should handle inserts that contain delete characters ', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'abcde',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end')); // cursor at the end
      expect(getBufferState(result).cursor).toEqual([0, 5]);

      act(() => {
        result.current.applyOperations([
          { type: 'insert', payload: '\x7f\x7f\x7f' },
        ]);
      });
      expect(getBufferState(result).text).toBe('ab');
      expect(getBufferState(result).cursor).toEqual([0, 2]);
    });

    it('should handle inserts with a mix of regular and delete characters ', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'abcde',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end')); // cursor at the end
      expect(getBufferState(result).cursor).toEqual([0, 5]);

      act(() => {
        result.current.applyOperations([
          { type: 'insert', payload: '\x7fI\x7f\x7fNEW' },
        ]);
      });
      expect(getBufferState(result).text).toBe('abcNEW');
      expect(getBufferState(result).cursor).toEqual([0, 6]);
    });

    it('should handle arrow keys for movement', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'ab',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.move('end')); // cursor [0,2]
      act(() => result.current.handleInput(undefined, { leftArrow: true })); // cursor [0,1]
      expect(getBufferState(result).cursor).toEqual([0, 1]);
      act(() => result.current.handleInput(undefined, { rightArrow: true })); // cursor [0,2]
      expect(getBufferState(result).cursor).toEqual([0, 2]);
    });

    it('should strip ANSI escape codes when pasting text', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const textWithAnsi = '\x1B[31mHello\x1B[0m \x1B[32mWorld\x1B[0m';
      // Simulate pasting by calling handleInput with a string longer than 1 char
      act(() => result.current.handleInput(textWithAnsi, {}));
      expect(getBufferState(result).text).toBe('Hello World');
    });

    it('should handle VSCode terminal Shift+Enter as newline', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      act(() => result.current.handleInput('\r', {})); // Simulates Shift+Enter in VSCode terminal
      expect(getBufferState(result).lines).toEqual(['', '']);
    });

    it('should correctly handle repeated pasting of long text', () => {
      const longText = `not only five centuries, but also the leap into electronic typesetting, remaining essentially unchanged. It was popularised in the 1960s with the release of Letraset sheets containing Lorem Ipsum passages, and more recently with desktop publishing software like Aldus PageMaker including versions of Lorem Ipsum.

Why do we use it?
It is a long established fact that a reader will be distracted by the readable content of a page when looking at its layout. The point of using Lorem Ipsum is that it has a more-or-less normal distribution of letters, as opposed to using 'Content here, content here', making it look like readable English. Many desktop publishing packages and web page editors now use Lorem Ipsum as their default model text, and a search for 'lorem ipsum' will uncover many web sites still in their infancy. Various versions have evolved over the years, sometimes by accident, sometimes on purpose (injected humour and the like).

Where does it come from?
Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old. Richard McClintock, a Latin professor at Hampden-Sydney College in Virginia, looked up one of the more obscure Latin words, consectetur, from a Lore
`;
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );

      // Simulate pasting the long text multiple times
      act(() => {
        result.current.applyOperations([
          { type: 'insert', payload: longText },
          { type: 'insert', payload: longText },
          { type: 'insert', payload: longText },
        ]);
      });

      const state = getBufferState(result);
      // Check that the text is the result of three concatenations.
      expect(state.lines).toStrictEqual(
        (longText + longText + longText).split('\n'),
      );
      const expectedCursorPos = offsetToLogicalPos(
        state.text,
        state.text.length,
      );
      expect(state.cursor).toEqual(expectedCursorPos);
    });
  });

  // More tests would be needed for:
  // - setText, replaceRange
  // - deleteWordLeft, deleteWordRight
  // - More complex undo/redo scenarios
  // - Selection and clipboard (copy/paste) - might need clipboard API mocks or internal state check
  // - openInExternalEditor (heavy mocking of fs, child_process, os)
  // - All edge cases for visual scrolling and wrapping with different viewport sizes and text content.

  describe('replaceRange', () => {
    it('should replace a single-line range with single-line text', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: '@pac',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 1, 0, 4, 'packages'));
      const state = getBufferState(result);
      expect(state.text).toBe('@packages');
      expect(state.cursor).toEqual([0, 9]); // cursor after 'typescript'
    });

    it('should replace a multi-line range with single-line text', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'hello\nworld\nagain',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 2, 1, 3, ' new ')); // replace 'llo\nwor' with ' new '
      const state = getBufferState(result);
      expect(state.text).toBe('he new ld\nagain');
      expect(state.cursor).toEqual([0, 7]); // cursor after ' new '
    });

    it('should delete a range when replacing with an empty string', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'hello world',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 5, 0, 11, '')); // delete ' world'
      const state = getBufferState(result);
      expect(state.text).toBe('hello');
      expect(state.cursor).toEqual([0, 5]);
    });

    it('should handle replacing at the beginning of the text', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'world',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 0, 0, 0, 'hello '));
      const state = getBufferState(result);
      expect(state.text).toBe('hello world');
      expect(state.cursor).toEqual([0, 6]);
    });

    it('should handle replacing at the end of the text', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'hello',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 5, 0, 5, ' world'));
      const state = getBufferState(result);
      expect(state.text).toBe('hello world');
      expect(state.cursor).toEqual([0, 11]);
    });

    it('should handle replacing the entire buffer content', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'old text',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 0, 0, 8, 'new text'));
      const state = getBufferState(result);
      expect(state.text).toBe('new text');
      expect(state.cursor).toEqual([0, 8]);
    });

    it('should correctly replace with unicode characters', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'hello *** world',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 6, 0, 9, '你好'));
      const state = getBufferState(result);
      expect(state.text).toBe('hello 你好 world');
      expect(state.cursor).toEqual([0, 8]); // after '你好'
    });

    it('should handle invalid range by returning false and not changing text', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'test',
          viewport,
          isValidPath: () => false,
        }),
      );
      let success = true;
      act(() => {
        success = result.current.replaceRange(0, 5, 0, 3, 'fail'); // startCol > endCol in same line
      });
      expect(success).toBe(false);
      expect(getBufferState(result).text).toBe('test');

      act(() => {
        success = result.current.replaceRange(1, 0, 0, 0, 'fail'); // startRow > endRow
      });
      expect(success).toBe(false);
      expect(getBufferState(result).text).toBe('test');
    });

    it('replaceRange: multiple lines with a single character', () => {
      const { result } = renderHook(() =>
        useTextBuffer({
          initialText: 'first\nsecond\nthird',
          viewport,
          isValidPath: () => false,
        }),
      );
      act(() => result.current.replaceRange(0, 2, 2, 3, 'X')); // Replace 'rst\nsecond\nthi'
      const state = getBufferState(result);
      expect(state.text).toBe('fiXrd');
      expect(state.cursor).toEqual([0, 3]); // After 'X'
    });
  });

  describe('Input Sanitization', () => {
    it('should strip ANSI escape codes from input', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const textWithAnsi = '\x1B[31mHello\x1B[0m';
      act(() => result.current.handleInput(textWithAnsi, {}));
      expect(getBufferState(result).text).toBe('Hello');
    });

    it('should strip control characters from input', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const textWithControlChars = 'H\x07e\x08l\x0Bl\x0Co'; // BELL, BACKSPACE, VT, FF
      act(() => result.current.handleInput(textWithControlChars, {}));
      expect(getBufferState(result).text).toBe('Hello');
    });

    it('should strip mixed ANSI and control characters from input', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const textWithMixed = '\u001B[4mH\u001B[0mello';
      act(() => result.current.handleInput(textWithMixed, {}));
      expect(getBufferState(result).text).toBe('Hello');
    });

    it('should not strip standard characters or newlines', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const validText = 'Hello World\nThis is a test.';
      act(() => result.current.handleInput(validText, {}));
      expect(getBufferState(result).text).toBe(validText);
    });

    it('should sanitize pasted text via handleInput', () => {
      const { result } = renderHook(() =>
        useTextBuffer({ viewport, isValidPath: () => false }),
      );
      const pastedText = '\u001B[4mPasted\u001B[4m Text';
      act(() => result.current.handleInput(pastedText, {}));
      expect(getBufferState(result).text).toBe('Pasted Text');
    });
  });
});

describe('offsetToLogicalPos', () => {
  it('should return [0,0] for offset 0', () => {
    expect(offsetToLogicalPos('any text', 0)).toEqual([0, 0]);
  });

  it('should handle single line text', () => {
    const text = 'hello';
    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start
    expect(offsetToLogicalPos(text, 2)).toEqual([0, 2]); // Middle 'l'
    expect(offsetToLogicalPos(text, 5)).toEqual([0, 5]); // End
    expect(offsetToLogicalPos(text, 10)).toEqual([0, 5]); // Beyond end
  });

  it('should handle multi-line text', () => {
    const text = 'hello\nworld\n123';
    // "hello" (5) + \n (1) + "world" (5) + \n (1) + "123" (3)
    // h e l l o \n w o r l d \n 1 2 3
    // 0 1 2 3 4  5  6 7 8 9 0  1  2 3 4
    // Line 0: "hello" (length 5)
    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start of 'hello'
    expect(offsetToLogicalPos(text, 3)).toEqual([0, 3]); // 'l' in 'hello'
    expect(offsetToLogicalPos(text, 5)).toEqual([0, 5]); // End of 'hello' (before \n)

    // Line 1: "world" (length 5)
    expect(offsetToLogicalPos(text, 6)).toEqual([1, 0]); // Start of 'world' (after \n)
    expect(offsetToLogicalPos(text, 8)).toEqual([1, 2]); // 'r' in 'world'
    expect(offsetToLogicalPos(text, 11)).toEqual([1, 5]); // End of 'world' (before \n)

    // Line 2: "123" (length 3)
    expect(offsetToLogicalPos(text, 12)).toEqual([2, 0]); // Start of '123' (after \n)
    expect(offsetToLogicalPos(text, 13)).toEqual([2, 1]); // '2' in '123'
    expect(offsetToLogicalPos(text, 15)).toEqual([2, 3]); // End of '123'
    expect(offsetToLogicalPos(text, 20)).toEqual([2, 3]); // Beyond end of text
  });

  it('should handle empty lines', () => {
    const text = 'a\n\nc'; // "a" (1) + \n (1) + "" (0) + \n (1) + "c" (1)
    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // 'a'
    expect(offsetToLogicalPos(text, 1)).toEqual([0, 1]); // End of 'a'
    expect(offsetToLogicalPos(text, 2)).toEqual([1, 0]); // Start of empty line
    expect(offsetToLogicalPos(text, 3)).toEqual([2, 0]); // Start of 'c'
    expect(offsetToLogicalPos(text, 4)).toEqual([2, 1]); // End of 'c'
  });

  it('should handle text ending with a newline', () => {
    const text = 'hello\n'; // "hello" (5) + \n (1)
    expect(offsetToLogicalPos(text, 5)).toEqual([0, 5]); // End of 'hello'
    expect(offsetToLogicalPos(text, 6)).toEqual([1, 0]); // Position on the new empty line after

    expect(offsetToLogicalPos(text, 7)).toEqual([1, 0]); // Still on the new empty line
  });

  it('should handle text starting with a newline', () => {
    const text = '\nhello'; // "" (0) + \n (1) + "hello" (5)
    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start of first empty line
    expect(offsetToLogicalPos(text, 1)).toEqual([1, 0]); // Start of 'hello'
    expect(offsetToLogicalPos(text, 3)).toEqual([1, 2]); // 'l' in 'hello'
  });

  it('should handle empty string input', () => {
    expect(offsetToLogicalPos('', 0)).toEqual([0, 0]);
    expect(offsetToLogicalPos('', 5)).toEqual([0, 0]);
  });

  it('should handle multi-byte unicode characters correctly', () => {
    const text = '你好\n世界'; // "你好" (2 chars) + \n (1) + "世界" (2 chars)
    // Total "code points" for offset calculation: 2 + 1 + 2 = 5
    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]); // Start of '你好'
    expect(offsetToLogicalPos(text, 1)).toEqual([0, 1]); // After '你', before '好'
    expect(offsetToLogicalPos(text, 2)).toEqual([0, 2]); // End of '你好'
    expect(offsetToLogicalPos(text, 3)).toEqual([1, 0]); // Start of '世界'
    expect(offsetToLogicalPos(text, 4)).toEqual([1, 1]); // After '世', before '界'
    expect(offsetToLogicalPos(text, 5)).toEqual([1, 2]); // End of '世界'
    expect(offsetToLogicalPos(text, 6)).toEqual([1, 2]); // Beyond end
  });

  it('should handle offset exactly at newline character', () => {
    const text = 'abc\ndef';
    // a b c \n d e f
    // 0 1 2  3  4 5 6
    expect(offsetToLogicalPos(text, 3)).toEqual([0, 3]); // End of 'abc'
    // The next character is the newline, so an offset of 4 means the start of the next line.
    expect(offsetToLogicalPos(text, 4)).toEqual([1, 0]); // Start of 'def'
  });

  it('should handle offset in the middle of a multi-byte character (should place at start of that char)', () => {
    // This scenario is tricky as "offset" is usually character-based.
    // Assuming cpLen and related logic handles this by treating multi-byte as one unit.
    // The current implementation of offsetToLogicalPos uses cpLen, so it should be code-point aware.
    const text = '🐶🐱'; // 2 code points
    expect(offsetToLogicalPos(text, 0)).toEqual([0, 0]);
    expect(offsetToLogicalPos(text, 1)).toEqual([0, 1]); // After 🐶
    expect(offsetToLogicalPos(text, 2)).toEqual([0, 2]); // After 🐱
  });
});
