import type { FileNode, DependencyEdge } from "@codeboard/shared";

function sanitizeId(path: string): string {
  return path.replace(/[^a-zA-Z0-9]/g, "_");
}

function shortenPath(path: string): string {
  const parts = path.split("/");
  if (parts.length <= 2) return path;
  return parts.slice(-2).join("/");
}

export function generateDependencyGraph(
  files: FileNode[],
  deps: DependencyEdge[]
): string {
  if (files.length === 0) {
    return "graph LR\n  empty[No files detected]";
  }

  const maxFiles = 30;
  const topFiles = files.slice(0, maxFiles);
  const topPaths = new Set(topFiles.map((f) => f.path));

  const lines: string[] = ["graph LR"];

  for (const file of topFiles) {
    const id = sanitizeId(file.path);
    const label = shortenPath(file.path);
    lines.push(`  ${id}["${label}"]`);
  }

  const edgeSet = new Set<string>();
  for (const dep of deps) {
    if (!topPaths.has(dep.source) || !topPaths.has(dep.target)) continue;
    if (dep.source === dep.target) continue;

    const edgeKey = `${dep.source}-${dep.target}`;
    if (edgeSet.has(edgeKey)) continue;
    edgeSet.add(edgeKey);

    const sourceId = sanitizeId(dep.source);
    const targetId = sanitizeId(dep.target);
    lines.push(`  ${sourceId} --> ${targetId}`);
  }

  return lines.join("\n");
}