lib/social-copy.ts

import { callLlm } from "@/lib/llm";
import type { GitHubRepoData } from "@/types";

/** Exactly the fields the webhook consumer expects (snake_case, flat). */
export interface SocialCopy {
  instagram_caption: string;
  youtube_caption: string;
  hashtags: string[];
}

function normalizeTags(tags: unknown, repo: GitHubRepoData): string[] {
  const list = Array.isArray(tags) ? tags : [];
  const cleaned = list
    .filter((t): t is string => typeof t === "string")
    .map((t) => `#${t.trim().replace(/^#+/, "").replace(/\s+/g, "")}`)
    .filter((t) => t.length > 1);

  // ponytail: dedupe case-insensitively — "#GitHub" and "#github" read as spam repeats
  const seen = new Set<string>();
  const unique = cleaned.filter((t) => {
    const key = t.toLowerCase();
    if (seen.has(key)) return false;
    seen.add(key);
    return true;
  });

  if (unique.length) return unique;

  // fallback from repo metadata so the webhook always carries usable tags
  return [
    "#GitHub",
    "#OpenSource",
    "#Coding",
    ...(repo.language ? [`#${repo.language.replace(/\s+/g, "")}`] : []),
    ...repo.topics.slice(0, 3).map((t) => `#${t.replace(/[^a-z0-9]/gi, "")}`),
  ].filter((t) => t.length > 1);
}

function fallbackCopy(repo: GitHubRepoData, script: string): SocialCopy {
  const summary = repo.description || script;
  return {
    instagram_caption: `${summary} Check out ${repo.fullName} on GitHub and see what you can build with it.`,
    youtube_caption: `Repo: ${repo.fullName}. ${summary} GitHub: ${repo.htmlUrl}. Don't forget to subscribe for more developer tool updates!`,
    hashtags: normalizeTags(null, repo),
  };
}

/**
 * Instagram + YouTube copy for a finished reel. Never throws: social text is a
 * nice-to-have, so a flaky LLM must not sink an otherwise successful render.
 */
export async function generateSocialCopy(
  repo: GitHubRepoData,
  script: string,
): Promise<SocialCopy> {
  const prompt = `You write social media copy for a short vertical video about a GitHub repo.

Repo: ${repo.fullName}
Description: ${repo.description || "No description"}
Language: ${repo.language}
Stars: ${repo.stars}
Topics: ${repo.topics.join(", ") || "none"}
Repo URL: ${repo.htmlUrl}

README excerpt:
${repo.readme.slice(0, 1500)}

The video narration says:
${script}

Return ONLY minified JSON, no markdown fence, exactly this shape:
{"instagram_caption":"...","youtube_caption":"...","hashtags":["#Tag"]}

instagram_caption rules:
- One flowing paragraph, 600-900 characters
- Opens with a question or pain point the repo solves
- Names the repo and explains what it actually does
- Mentions a concrete detail (stars, a key feature, who it is for)
- Ends with a question to the reader plus a call to check the repo
- No hashtags and no line breaks inside the caption

youtube_caption rules:
- One paragraph, 400-700 characters
- Starts exactly with "Repo: ${repo.fullName}."
- Explains the problem it solves and who should use it
- Includes "GitHub: ${repo.htmlUrl}"
- Ends with a line inviting viewers to subscribe for more developer tool updates

hashtags rules:
- 5-8 tags, PascalCase, each starting with #
- Broad reach tags (#AI, #OpenSource, #GitHub) plus 2-3 specific to this repo
- No spaces inside a tag`;

  // ponytail: two tries — this model stalls now and then, and a retry is cheaper
  // than shipping the metadata fallback to a live social account
  for (let attempt = 1; attempt <= 2; attempt++) {
    try {
      const raw = await callLlm(prompt, { maxTokens: 900, temperature: 0.7 });

      // models like wrapping JSON in prose or a fence — take the outermost object
      const json = raw.slice(raw.indexOf("{"), raw.lastIndexOf("}") + 1);
      const parsed = JSON.parse(json) as Partial<SocialCopy>;

      const instagram = parsed.instagram_caption?.trim().replace(/\s+/g, " ");
      const youtube = parsed.youtube_caption?.trim().replace(/\s+/g, " ");
      if (!instagram || !youtube) {
        throw new Error("LLM omitted instagram_caption or youtube_caption");
      }

      return {
        instagram_caption: instagram.slice(0, 2200),
        youtube_caption: youtube.slice(0, 5000),
        hashtags: normalizeTags(parsed.hashtags, repo),
      };
    } catch (error) {
      console.error(`Social copy attempt ${attempt} failed:`, error);
    }
  }

  console.error("Social copy generation failed twice, using metadata fallback");
  return fallbackCopy(repo, script);
}