clicktrack/lib/analysis/providers/openai.ts

import 'server-only';

import type { CTPDocument } from "@/lib/ctp/schema";
import type { AnalysisInput, AnalysisProvider } from "@/lib/analysis/providers";
import { CTP_SCHEMA, SYSTEM_PROMPT } from "./anthropic";

function buildLabel(): string {
  const model = process.env.OPENAI_MODEL ?? "GPT-4o";
  const baseUrl = process.env.OPENAI_BASE_URL ?? "";
  if (baseUrl && !baseUrl.includes("api.openai.com")) {
    try {
      const host = new URL(baseUrl).hostname;
      return `${model} (${host})`;
    } catch {
      // fall through
    }
  }
  return `${model} (OpenAI)`;
}

export const openaiProvider: AnalysisProvider = {
  id: "openai",
  label: buildLabel(),
  type: "cloud-ai",

  async isAvailable() {
    if (process.env.OPENAI_API_KEY) {
      return { available: true };
    }
    return { available: false, reason: "OPENAI_API_KEY not set" };
  },

  async generateCTP(input: AnalysisInput): Promise<CTPDocument> {
    const apiKey = process.env.OPENAI_API_KEY;
    if (!apiKey) {
      throw new Error("OPENAI_API_KEY not set");
    }

    const baseUrl = process.env.OPENAI_BASE_URL ?? "https://api.openai.com/v1";
    const model = process.env.OPENAI_MODEL ?? "gpt-4o";
    const { bpm, duration, title, artist, mbid, contributed_by, confirmedBpm, confirmedTimeSigNum } = input;
    const effectiveBpm = confirmedBpm ?? bpm;
    const approxBars = Math.round((duration * effectiveBpm) / 60 / 4);

    const bpmLine = confirmedBpm
      ? `Confirmed BPM (from MusicBrainz community tags — treat as authoritative): ${confirmedBpm}\nDetected BPM (audio analysis): ${bpm}`
      : `Detected BPM (audio analysis): ${bpm}`;

    const timeSigHint = confirmedTimeSigNum
      ? `\nConfirmed time signature numerator: ${confirmedTimeSigNum}`
      : "";

    const userMessage = `\
Generate a CTP document for the following song:

Title: ${title ?? "Unknown Title"}
Artist: ${artist ?? "Unknown Artist"}
MusicBrainz ID: ${mbid ?? "unknown"}
${bpmLine}${timeSigHint}
Duration: ${duration.toFixed(1)} seconds (~${approxBars} bars at 4/4)
Contributed by: ${contributed_by}

If you recognise this song, use your training knowledge of its actual arrangement — section names, bar counts, time signature, and any tempo changes. If you do not recognise it, use a sensible generic structure based on the BPM and duration above.`;

    const response = await fetch(`${baseUrl}/chat/completions`, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        Authorization: `Bearer ${apiKey}`,
      },
      body: JSON.stringify({
        model,
        messages: [
          { role: "system", content: SYSTEM_PROMPT },
          { role: "user", content: userMessage },
        ],
        response_format: {
          type: "json_schema",
          json_schema: {
            strict: true,
            name: "CTPDocument",
            schema: CTP_SCHEMA,
          },
        },
        max_tokens: 2048,
      }),
    });

    if (!response.ok) {
      const text = await response.text().catch(() => "");
      throw new Error(`OpenAI API error ${response.status}: ${text.slice(0, 200)}`);
    }

    const json = await response.json() as {
      choices?: Array<{ message?: { content?: string } }>;
    };

    const content = json.choices?.[0]?.message?.content;
    if (!content) {
      throw new Error("OpenAI did not return a message content");
    }

    let parsed: unknown;
    try {
      parsed = JSON.parse(content);
    } catch {
      throw new Error(`OpenAI returned invalid JSON: ${content.slice(0, 200)}`);
    }

    const doc = parsed as CTPDocument;
    if (!doc.metadata.created_at || doc.metadata.created_at.includes("placeholder")) {
      doc.metadata.created_at = new Date().toISOString();
    }

    return doc;
  },
};