/**
 * Pure utility functions — no pi API, no Julia processes, no I/O.
 * Extracted here so they can be unit-tested independently.
 */

import * as fs from "node:fs";
import * as path from "node:path";

// ─── Path resolution ──────────────────────────────────────────────────────────

/** Walk upward from startDir until a Project.toml is found. */
export function findProjectToml(startDir: string): string | undefined {
  let dir = startDir;
  while (true) {
    if (fs.existsSync(path.join(dir, "Project.toml"))) return dir;
    const parent = path.dirname(dir);
    if (parent === dir) return undefined;
    dir = parent;
  }
}

/**
 * Resolve a raw path argument to an absolute project directory.
 * Mirrors `julia --project=<arg>` semantics:
 *   ""  / "."              → search upward from cwd for nearest Project.toml
 *   relative / absolute    → must contain Project.toml
 *   path/to/Project.toml   → use its directory
 */
export function resolveProjectPath(arg: string, cwd: string): string | undefined {
  const t = arg.trim();
  if (!t || t === ".") return findProjectToml(cwd);
  const resolved = path.resolve(cwd, t);
  if (path.basename(resolved) === "Project.toml") return path.dirname(resolved);
  if (fs.existsSync(path.join(resolved, "Project.toml"))) return resolved;
  return undefined;
}

// ─── Port allocation ──────────────────────────────────────────────────────────

/** Stable port in 3001-3999 derived from the project path string. */
export function projectPort(projectPath: string): number {
  let hash = 0;
  for (const c of projectPath) hash = ((hash * 31) + c.charCodeAt(0)) & 0xffff;
  return 3001 + (hash % 999);
}

// ─── Output formatting ────────────────────────────────────────────────────────

const MAX_OUTPUT_BYTES = 50 * 1024;

export function formatOutput(result: {
  stdout: string;
  stderr: string;
  code: number;
}): string {
  const parts: string[] = [];

  if (result.stdout.trim()) {
    let out = result.stdout;
    if (Buffer.byteLength(out) > MAX_OUTPUT_BYTES)
      out = `[...truncated — last ${MAX_OUTPUT_BYTES / 1024} KB...]\n` + out.slice(-MAX_OUTPUT_BYTES);
    parts.push(out.trimEnd());
  }

  if (result.stderr.trim())
    parts.push(`--- stderr ---\n${result.stderr.trimEnd()}`);

  if (result.code !== 0)
    parts.push(`--- exit code: ${result.code} ---`);

  return parts.length ? parts.join("\n\n") : "(no output)";
}