import fs from "node:fs";
import os from "node:os";
import path from "node:path";

import { ensureAbsolutePath } from "./fs.mjs";

export const TRANSCRIPT_PATH_ENV = "CODEX_COMPANION_TRANSCRIPT_PATH";
const CLAUDE_PROJECTS_DIR = path.join(os.homedir(), ".claude", "projects");

function resolveUserPath(cwd, value) {
  if (value === "~") {
    return os.homedir();
  }
  if (String(value).startsWith("~/")) {
    return path.join(os.homedir(), String(value).slice(2));
  }
  return ensureAbsolutePath(cwd, value);
}

export function resolveClaudeSessionPath(cwd, options = {}) {
  const requestedPath = options.source || process.env[TRANSCRIPT_PATH_ENV];
  if (!requestedPath) {
    throw new Error("Could not identify the current Claude transcript. Retry with --source <path-to-claude-jsonl>.");
  }

  const sourcePath = resolveUserPath(cwd, requestedPath);
  if (path.extname(sourcePath) !== ".jsonl") {
    throw new Error(`Claude session source must be a JSONL file: ${sourcePath}`);
  }

  let source;
  let projects;
  try {
    source = fs.realpathSync(sourcePath);
    projects = fs.realpathSync(CLAUDE_PROJECTS_DIR);
  } catch {
    throw new Error(`Claude session file not found: ${sourcePath}`);
  }
  const relative = path.relative(projects, source);
  if (relative === "" || relative === ".." || relative.startsWith(`..${path.sep}`) || path.isAbsolute(relative)) {
    throw new Error(`Codex can import Claude sessions only from ${CLAUDE_PROJECTS_DIR}: ${source}`);
  }
  return source;
}