import { describe, it, expect } from 'vitest';
import { exportToCsv, escapeField } from '../src/sheets/csv-export.js';

// UTF-8 BOM character
const BOM = '\uFEFF';

/**
 * Helper: create a getCellValue function from a 2D array.
 * Array is 0-indexed; getCellValue is 1-based (row, col).
 */
function gridFromArray(data) {
  return (row, col) => {
    const r = row - 1;
    const c = col - 1;
    if (r < 0 || r >= data.length) return '';
    if (c < 0 || c >= data[r].length) return '';
    return String(data[r][c] ?? '');
  };
}

// ============================================================
// escapeField
// ============================================================
describe('CSV Export — escapeField', () => {
  it('returns empty string for empty input', () => {
    expect(escapeField('', ',')).toBe('');
  });

  it('returns plain string unchanged when no special chars', () => {
    expect(escapeField('hello', ',')).toBe('hello');
  });

  it('quotes fields containing the comma delimiter', () => {
    expect(escapeField('a,b', ',')).toBe('"a,b"');
  });

  it('quotes fields containing double quotes and escapes them', () => {
    expect(escapeField('say "hi"', ',')).toBe('"say ""hi"""');
  });

  it('quotes fields containing newlines', () => {
    expect(escapeField('line1\nline2', ',')).toBe('"line1\nline2"');
  });

  it('quotes fields containing carriage returns', () => {
    expect(escapeField('line1\rline2', ',')).toBe('"line1\rline2"');
  });

  it('handles tab delimiter — does not quote commas when delimiter is tab', () => {
    expect(escapeField('a,b', '\t')).toBe('a,b');
  });

  it('quotes fields containing tab when delimiter is tab', () => {
    expect(escapeField('a\tb', '\t')).toBe('"a\tb"');
  });

  it('handles field with all special characters', () => {
    expect(escapeField('a,"b"\nc', ',')).toBe('"a,""b""\nc"');
  });
});

// ============================================================
// exportToCsv — basic output
// ============================================================
describe('CSV Export — exportToCsv basic', () => {
  it('generates CSV from a simple 2x2 grid', () => {
    const data = [['A', 'B'], ['1', '2']];
    const result = exportToCsv(gridFromArray(data), 2, 2);
    expect(result).toBe(BOM + 'A,B\r\n1,2');
  });

  it('starts with UTF-8 BOM', () => {
    const data = [['x']];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result.charCodeAt(0)).toBe(0xFEFF);
  });

  it('uses CRLF line endings (RFC 4180)', () => {
    const data = [['a'], ['b'], ['c']];
    const result = exportToCsv(gridFromArray(data), 3, 1);
    expect(result).toBe(BOM + 'a\r\nb\r\nc');
  });

  it('handles empty cells', () => {
    const data = [['', 'B'], ['', '']];
    const result = exportToCsv(gridFromArray(data), 2, 2);
    expect(result).toBe(BOM + ',B\r\n,');
  });

  it('handles single cell', () => {
    const data = [['only']];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result).toBe(BOM + 'only');
  });

  it('handles numeric values', () => {
    const data = [['42', '3.14']];
    const result = exportToCsv(gridFromArray(data), 1, 2);
    expect(result).toBe(BOM + '42,3.14');
  });
});

// ============================================================
// exportToCsv — RFC 4180 escaping
// ============================================================
describe('CSV Export — RFC 4180 escaping', () => {
  it('quotes fields with commas', () => {
    const data = [['a,b', 'c']];
    const result = exportToCsv(gridFromArray(data), 1, 2);
    expect(result).toBe(BOM + '"a,b",c');
  });

  it('escapes double quotes within fields', () => {
    const data = [['say "hello"']];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result).toBe(BOM + '"say ""hello"""');
  });

  it('quotes fields with embedded newlines', () => {
    const data = [['line1\nline2']];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result).toBe(BOM + '"line1\nline2"');
  });

  it('handles field with commas, quotes, and newlines together', () => {
    const data = [['a,"b"\nc']];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result).toBe(BOM + '"a,""b""\nc"');
  });
});

// ============================================================
// exportToCsv — TSV (tab delimiter)
// ============================================================
describe('CSV Export — TSV variant', () => {
  it('uses tab delimiter', () => {
    const data = [['A', 'B'], ['1', '2']];
    const result = exportToCsv(gridFromArray(data), 2, 2, { delimiter: '\t' });
    expect(result).toBe(BOM + 'A\tB\r\n1\t2');
  });

  it('does not quote fields with commas in TSV mode', () => {
    const data = [['a,b', 'c']];
    const result = exportToCsv(gridFromArray(data), 1, 2, { delimiter: '\t' });
    expect(result).toBe(BOM + 'a,b\tc');
  });

  it('quotes fields with tabs in TSV mode', () => {
    const data = [['a\tb', 'c']];
    const result = exportToCsv(gridFromArray(data), 1, 2, { delimiter: '\t' });
    expect(result).toBe(BOM + '"a\tb"\tc');
  });
});

// ============================================================
// exportToCsv — includeHeaders option
// ============================================================
describe('CSV Export — includeHeaders', () => {
  it('prepends column letter headers when includeHeaders is true', () => {
    const data = [['val1', 'val2']];
    const result = exportToCsv(gridFromArray(data), 1, 2, { includeHeaders: true });
    expect(result).toBe(BOM + 'A,B\r\nval1,val2');
  });

  it('generates correct headers for 27+ columns (AA, AB, ...)', () => {
    const row = [];
    for (let i = 0; i < 28; i++) row.push(String(i));
    const result = exportToCsv(gridFromArray([row]), 1, 28, { includeHeaders: true });
    const lines = result.slice(1).split('\r\n'); // skip BOM
    const headers = lines[0].split(',');
    expect(headers[0]).toBe('A');
    expect(headers[25]).toBe('Z');
    expect(headers[26]).toBe('AA');
    expect(headers[27]).toBe('AB');
  });
});

// ============================================================
// exportToCsv — range export
// ============================================================
describe('CSV Export — range export', () => {
  it('exports only the specified range', () => {
    const data = [
      ['A1', 'B1', 'C1'],
      ['A2', 'B2', 'C2'],
      ['A3', 'B3', 'C3'],
    ];
    const result = exportToCsv(gridFromArray(data), 3, 3, {
      range: { startRow: 2, endRow: 3, startCol: 2, endCol: 3 },
    });
    expect(result).toBe(BOM + 'B2,C2\r\nB3,C3');
  });

  it('exports a single cell range', () => {
    const data = [['A1', 'B1'], ['A2', 'B2']];
    const result = exportToCsv(gridFromArray(data), 2, 2, {
      range: { startRow: 1, endRow: 1, startCol: 2, endCol: 2 },
    });
    expect(result).toBe(BOM + 'B1');
  });

  it('exports full range when range is null', () => {
    const data = [['X', 'Y']];
    const result = exportToCsv(gridFromArray(data), 1, 2, { range: null });
    expect(result).toBe(BOM + 'X,Y');
  });

  it('combines range with includeHeaders', () => {
    const data = [['A1', 'B1'], ['A2', 'B2']];
    const result = exportToCsv(gridFromArray(data), 2, 2, {
      range: { startRow: 1, endRow: 2, startCol: 2, endCol: 2 },
      includeHeaders: true,
    });
    expect(result).toBe(BOM + 'B\r\nB1\r\nB2');
  });
});

// ============================================================
// exportToCsv — edge cases
// ============================================================
describe('CSV Export — edge cases', () => {
  it('handles a completely empty grid', () => {
    const result = exportToCsv(() => '', 2, 2);
    // All cells empty => two rows of ","
    expect(result).toBe(BOM + ',\r\n,');
  });

  it('preserves leading/trailing whitespace in values', () => {
    const data = [['  spaced  ']];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result).toBe(BOM + '  spaced  ');
  });

  it('handles unicode characters', () => {
    const data = [['\u00e9', '\u00fc']];
    const result = exportToCsv(gridFromArray(data), 1, 2);
    expect(result).toBe(BOM + '\u00e9,\u00fc');
  });

  it('handles formulas as string values', () => {
    const data = [['=SUM(A1:A10)']];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result).toBe(BOM + '=SUM(A1:A10)');
  });

  it('handles very long string values', () => {
    const longStr = 'x'.repeat(10000);
    const data = [[longStr]];
    const result = exportToCsv(gridFromArray(data), 1, 1);
    expect(result).toBe(BOM + longStr);
  });
});