import { CommitDiff } from '../interfaces/CommitDiff';
import { FileDiff } from '../interfaces/FileDiff';

function generateHumanReadableCommitDiffDocument(commitDiff: CommitDiff): string {
  const output: string[] = [];

  output.push(`Commit title: ${commitDiff.title}`);
  if (commitDiff.message !== null) {
    output.push(`Commit message: ${commitDiff.message}`);
  }

  for (const fileDiff of commitDiff.diffs) {
    output.push(generateHumanReadableFileDiffText(fileDiff));
  }

  return output.join('\n');
}

/**
 * Generates a human-readable string that represents a git diff chunk.
 * Adds leading line numbers for code lines.
 */
function generateHumanReadableFileDiffText(fileDiff: FileDiff): string {
  const output: string[] = [];

  // Determine the maximum line number to calculate the width for padding
  const maxLineNum = fileDiff.lines.at(-1)?.lineNum;
  if (maxLineNum === undefined) {
    throw new Error('Could not determine the maximum line number of file diff');
  }
  const maxLineWidth = maxLineNum.toString().length;

  output.push(`File: ${fileDiff.fileName}`);
  output.push(`Changes:`);

  for (const line of fileDiff.lines) {
    // Pad the line number with spaces to ensure consistent alignment
    const paddedLineNum = line.lineNum.toString().padStart(maxLineWidth, ' ');
    output.push(`${paddedLineNum}: ${line.content}`);
  }

  return output.join('\n');
}

export { generateHumanReadableCommitDiffDocument };