import { sep } from "node:path";

/** POSIX-style path relative to repository root (e.g. `plans/Plan-a/Task-b.md`). */
export function toRepoPathPosix(relativeFromRepoRoot: string): string {
  return relativeFromRepoRoot.split(sep).join("/");
}

/**
 * Whether this repo-relative path should be imported as backlog markdown.
 * Expects POSIX `plans/...` paths.
 */
export function isTrackedBacklogMarkdown(repoPathPosix: string): boolean {
  if (!repoPathPosix.startsWith("plans/")) return false;
  if (repoPathPosix === "plans/README.md") return false;
  const base = repoPathPosix.split("/").pop() ?? "";
  return (
    base.startsWith("Plan-") || base.startsWith("Epic-") || base.startsWith("Task-")
  );
}

/**
 * Parent document path for hierarchy links, or `null` for plan roots.
 */
export function parentRepoPath(repoPathPosix: string): string | null {
  const parts = repoPathPosix.split("/").filter(Boolean);
  if (parts.length < 3 || parts[0] !== "plans") return null;

  const planDir = parts[1];
  if (!planDir.startsWith("Plan-")) return null;

  if (parts.length === 3) {
    const file = parts[2];
    if (file.startsWith("Plan-") && file.endsWith(".md")) return null;
  }

  if (parts.length === 4) {
    const file = parts[3];
    if (file.startsWith("Epic-") && file.endsWith(".md")) {
      return `plans/${planDir}/${planDir}.md`;
    }
  }

  if (parts.length === 5) {
    const epicDir = parts[2];
    const file = parts[4];
    if (epicDir.startsWith("Epic-") && file.startsWith("Task-") && file.endsWith(".md")) {
      return `plans/${planDir}/${epicDir}/${epicDir}.md`;
    }
  }

  return null;
}

export function planSlugFromPath(repoPathPosix: string): string | null {
  const parts = repoPathPosix.split("/").filter(Boolean);
  if (parts.length < 2 || parts[0] !== "plans") return null;
  const planDir = parts[1];
  return planDir.startsWith("Plan-") ? planDir.replace(/^Plan-/, "") : null;
}

export function epicFolderFromPath(repoPathPosix: string): string | null {
  const parts = repoPathPosix.split("/").filter(Boolean);
  if (parts.length < 3 || parts[0] !== "plans") return null;
  const epicDir = parts[2];
  if (parts.length >= 4 && epicDir.startsWith("Epic-")) return epicDir.replace(/^Epic-/, "");
  return null;
}