// Grid dimensions for each piece count (cols × rows)
const GRID_SIZES = {
  20:  { cols: 5,  rows: 4 },
  40:  { cols: 8,  rows: 5 },
  60:  { cols: 10, rows: 6 },
  100: { cols: 10, rows: 10 }
};

class PuzzleGenerator {
  /**
   * Generate puzzle piece data for the given piece count.
   * @param {number} pieceCount — 40, 60, or 100
   * @returns {{ cols, rows, pieces: PieceData[], horizConnectors: string[][], vertConnectors: string[][] }}
   *
   * horizConnectors[r][c] = 'tab'|'blank'  → right edge of cell [r][c]
   *                                           (left edge of [r][c+1] is the opposite)
   * vertConnectors[r][c]  = 'tab'|'blank'  → bottom edge of cell [r][c]
   *                                           (top edge of [r+1][c] is the opposite)
   */
  static generate(pieceCount) {
    const { cols, rows } = GRID_SIZES[pieceCount] || GRID_SIZES[40];

    // Build connector tables
    const horizConnectors = Array.from({ length: rows }, () =>
      Array.from({ length: cols - 1 }, () => Math.random() < 0.5 ? 'tab' : 'blank')
    );
    const vertConnectors = Array.from({ length: rows - 1 }, () =>
      Array.from({ length: cols }, () => Math.random() < 0.5 ? 'tab' : 'blank')
    );

    // Build PieceData array
    const pieces = [];
    for (let r = 0; r < rows; r++) {
      for (let c = 0; c < cols; c++) {
        pieces.push({
          id: r * cols + c,
          gridRow: r,
          gridCol: c,
          edges: {
            top:    r === 0         ? 'flat' : (vertConnectors[r - 1][c] === 'tab' ? 'blank' : 'tab'),
            bottom: r === rows - 1  ? 'flat' : vertConnectors[r][c],
            left:   c === 0         ? 'flat' : (horizConnectors[r][c - 1] === 'tab' ? 'blank' : 'tab'),
            right:  c === cols - 1  ? 'flat' : horizConnectors[r][c]
          },
          x: 0,
          y: 0
        });
      }
    }

    return { cols, rows, pieces, horizConnectors, vertConnectors };
  }
}