export function proposedPlanTitle(planMarkdown: string): string | null {
  const heading = planMarkdown.match(/^\s{0,3}#{1,6}\s+(.+)$/m)?.[1]?.trim();
  return heading && heading.length > 0 ? heading : null;
}

function sanitizePlanFileSegment(input: string): string {
  const sanitized = input
    .toLowerCase()
    .replace(/[`'".,!?()[\]{}]+/g, "")
    .replace(/[^a-z0-9]+/g, "-")
    .replace(/^-+|-+$/g, "");
  return sanitized.length > 0 ? sanitized : "plan";
}

export function buildPlanImplementationPrompt(planMarkdown: string): string {
  return `PLEASE IMPLEMENT THIS PLAN:\n${planMarkdown.trim()}`;
}

export function resolvePlanFollowUpSubmission(input: {
  draftText: string;
  planMarkdown: string;
}): {
  text: string;
  interactionMode: "default" | "plan";
} {
  const trimmedDraftText = input.draftText.trim();
  if (trimmedDraftText.length > 0) {
    return {
      text: trimmedDraftText,
      interactionMode: "plan",
    };
  }

  return {
    text: buildPlanImplementationPrompt(input.planMarkdown),
    interactionMode: "default",
  };
}

export function buildPlanImplementationThreadTitle(planMarkdown: string): string {
  const title = proposedPlanTitle(planMarkdown);
  if (!title) {
    return "Implement plan";
  }
  return `Implement ${title}`;
}

export function buildProposedPlanMarkdownFilename(planMarkdown: string): string {
  const title = proposedPlanTitle(planMarkdown);
  return `${sanitizePlanFileSegment(title ?? "plan")}.md`;
}

export function normalizePlanMarkdownForExport(planMarkdown: string): string {
  return `${planMarkdown.trimEnd()}\n`;
}

export function downloadPlanAsTextFile(filename: string, contents: string): void {
  const blob = new Blob([contents], { type: "text/markdown;charset=utf-8" });
  const url = URL.createObjectURL(blob);
  const anchor = document.createElement("a");
  anchor.href = url;
  anchor.download = filename;
  anchor.click();
  window.setTimeout(() => {
    URL.revokeObjectURL(url);
  }, 0);
}