import 'server-only';

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

function getBaseUrl(): string {
  return process.env.OLLAMA_BASE_URL ?? "http://localhost:11434";
}

// ─── Model list ───────────────────────────────────────────────────────────────

interface OllamaTagsResponse {
  models?: Array<{ name: string }>;
}

export async function getOllamaModels(): Promise<string[]> {
  try {
    const url = `${getBaseUrl()}/api/tags`;
    const response = await fetch(url, { signal: AbortSignal.timeout(5000) });
    if (!response.ok) return [];
    const json = await response.json() as OllamaTagsResponse;
    return (json.models ?? []).map((m) => m.name);
  } catch {
    return [];
  }
}

// ─── Chat completions helper ──────────────────────────────────────────────────

async function callOllama(model: string, userMessage: string): Promise<string> {
  const baseUrl = getBaseUrl();
  const response = await fetch(`${baseUrl}/v1/chat/completions`, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify({
      model,
      messages: [
        { role: "system", content: SYSTEM_PROMPT },
        {
          role: "user",
          content:
            userMessage +
            "\n\nRespond with valid JSON only. Do not add any explanation or markdown. Your entire response must be a single valid JSON object matching the schema.",
        },
      ],
      response_format: {
        type: "json_schema",
        json_schema: {
          name: "CTPDocument",
          schema: CTP_SCHEMA,
        },
      },
      stream: false,
    }),
    signal: AbortSignal.timeout(120000), // 2-minute timeout for slow local models
  });

  if (!response.ok) {
    const text = await response.text().catch(() => "");
    throw new Error(`Ollama 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("Ollama did not return a message content");
  }

  return content;
}

// ─── Provider implementation ──────────────────────────────────────────────────

export const ollamaProvider: AnalysisProvider = {
  id: "ollama",
  label: "Ollama",
  type: "local-ai",

  async isAvailable() {
    const url = getBaseUrl();
    try {
      const response = await fetch(`${url}/api/tags`, {
        signal: AbortSignal.timeout(5000),
      });
      if (response.ok) {
        return { available: true };
      }
      return { available: false, reason: `Ollama not reachable at ${url}` };
    } catch {
      return { available: false, reason: `Ollama not reachable at ${url}` };
    }
  },

  async generateCTP(input: AnalysisInput): Promise<CTPDocument> {
    const { ollamaModel, bpm, duration, title, artist, mbid, contributed_by } = input;

    if (!ollamaModel) {
      throw new Error("ollamaModel is required for Ollama provider");
    }

    const approxBars = Math.round((duration * bpm) / 60 / 4);

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

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

Create a plausible section layout for this song. If this is a well-known song, use your knowledge of its actual arrangement. If not, use a sensible generic structure.`;

    // Attempt parse with one retry on failure
    let content: string;
    try {
      content = await callOllama(ollamaModel, userMessage);
    } catch (err) {
      throw new Error(
        `Ollama request failed: ${err instanceof Error ? err.message : String(err)}`
      );
    }

    const tryParse = (raw: string): CTPDocument | null => {
      // Strip markdown code fences if present
      const stripped = raw.replace(/^```(?:json)?\s*/i, "").replace(/\s*```\s*$/, "").trim();
      try {
        const doc = JSON.parse(stripped) as CTPDocument;
        if (!doc.metadata.created_at || doc.metadata.created_at.includes("placeholder")) {
          doc.metadata.created_at = new Date().toISOString();
        }
        return doc;
      } catch {
        return null;
      }
    };

    const firstAttempt = tryParse(content);
    if (firstAttempt) return firstAttempt;

    // Retry once
    let retryContent: string;
    try {
      retryContent = await callOllama(ollamaModel, userMessage);
    } catch (err) {
      throw new Error(
        `Ollama retry request failed: ${err instanceof Error ? err.message : String(err)}`
      );
    }

    const secondAttempt = tryParse(retryContent);
    if (secondAttempt) return secondAttempt;

    throw new Error(
      `Ollama (${ollamaModel}) returned a response that could not be parsed as a valid CTP document. ` +
        `Response preview: ${content.slice(0, 200)}`
    );
  },
};