"""Thin wrapper around the OpenAI API for generating alt text."""

from __future__ import annotations

from typing import Any, Dict, List, Optional

import requests


class AltTextGenerationError(RuntimeError):
    """Raised when the OpenAI API cannot generate alt text."""


class AltTextGenerator:
    """Request alt text from a GPT-4o compatible OpenAI endpoint."""

    def __init__(self, api_key: str, model: str = "gpt-4o-mini") -> None:
        if not api_key:
            raise ValueError("OPENAI_API_KEY is required")
        self.model = model
        self.session = requests.Session()
        self.session.headers.update(
            {
                "Authorization": f"Bearer {api_key}",
                "Content-Type": "application/json",
            }
        )
        self.endpoint = "https://api.openai.com/v1/chat/completions"

    def generate_alt_text(
        self,
        image_source: str,
        notes: Optional[str] = None,
        captured_at: Optional[str] = None,
        location: Optional[str] = None,
        coordinates: Optional[str] = None,
    ) -> str:
        if not image_source:
            raise AltTextGenerationError("Image URL required for alt text generation")

        prompt_lines = [
            "You write vivid but concise Mastodon alt text.",
            "Keep it under 400 characters and mention key visual details, colours, "
            "actions, and text. No need to mention the mood unless you think it is "
            "super relevant.",
            "Avoid speculation beyond what is visible. Use UK English spelling.",
        ]
        if notes:
            prompt_lines.append(f"Creator notes: {notes.strip()}")
        if captured_at:
            prompt_lines.append(f"Captured: {captured_at}")
        if location:
            prompt_lines.append(f"Location: {location}")
        if coordinates:
            prompt_lines.append(f"Coordinates: {coordinates}")
        text_prompt = "\n".join(prompt_lines)

        content: List[Dict[str, Any]] = [
            {"type": "text", "text": text_prompt},
            {"type": "image_url", "image_url": {"url": image_source}},
        ]

        payload = {
            "model": self.model,
            "temperature": 0.2,
            "max_tokens": 300,
            "messages": [
                {
                    "role": "system",
                    "content": "You help write accessible alt text for social media posts.",
                },
                {
                    "role": "user",
                    "content": content,
                },
            ],
        }
        try:
            response = self.session.post(self.endpoint, json=payload, timeout=30)
            response.raise_for_status()
            data = response.json()
        except requests.RequestException as exc:  # pragma: no cover
            raise AltTextGenerationError(str(exc)) from exc

        choices = data.get("choices") or []
        if not choices:
            raise AltTextGenerationError("OpenAI response did not include choices")

        message = choices[0].get("message", {})
        content_text = message.get("content")
        if not content_text:
            raise AltTextGenerationError("OpenAI response missing content")

        return content_text.strip()