143 lines
5.1 KiB
Python
143 lines
5.1 KiB
Python
"""Thin wrapper around the OpenAI API for generating alt text."""
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from __future__ import annotations
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from typing import Any, Dict, List, Optional
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import requests
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class OpenAIClientError(RuntimeError):
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"""Raised when the OpenAI API cannot fulfill a request."""
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class AltTextGenerationError(OpenAIClientError):
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"""Raised when the OpenAI API cannot generate alt text."""
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class TextImprovementError(OpenAIClientError):
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"""Raised when the OpenAI API cannot improve post text."""
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class AltTextGenerator:
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"""Request alt text from a GPT-4o compatible OpenAI endpoint."""
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def __init__(self, api_key: str, model: str = "gpt-4o-mini") -> None:
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if not api_key:
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raise ValueError("OPENAI_API_KEY is required")
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self.model = model
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self.session = requests.Session()
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self.session.headers.update(
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{
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"Authorization": f"Bearer {api_key}",
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"Content-Type": "application/json",
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}
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)
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self.endpoint = "https://api.openai.com/v1/chat/completions"
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def generate_alt_text(
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self,
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image_source: str,
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notes: Optional[str] = None,
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captured_at: Optional[str] = None,
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location: Optional[str] = None,
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coordinates: Optional[str] = None,
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) -> str:
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if not image_source:
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raise AltTextGenerationError("Image URL required for alt text generation")
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prompt_lines = [
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"You write vivid but concise Mastodon alt text.",
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"Keep it under 400 characters and mention key visual details, colours, "
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"actions, and text. No need to mention the mood unless you think it is "
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"super relevant.",
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"Avoid speculation beyond what is visible. Use UK English spelling.",
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]
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if notes:
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prompt_lines.append(f"Creator notes: {notes.strip()}")
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if captured_at:
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prompt_lines.append(f"Captured: {captured_at}")
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if location:
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prompt_lines.append(f"Location: {location}")
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if coordinates:
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prompt_lines.append(f"Coordinates: {coordinates}")
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text_prompt = "\n".join(prompt_lines)
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content: List[Dict[str, Any]] = [
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{"type": "text", "text": text_prompt},
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{"type": "image_url", "image_url": {"url": image_source}},
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]
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payload = {
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"model": self.model,
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"temperature": 0.2,
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"max_tokens": 300,
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"messages": [
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{
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"role": "system",
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"content": "You help write accessible alt text for social media posts.",
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},
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{
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"role": "user",
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"content": content,
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},
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],
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}
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try:
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response = self.session.post(self.endpoint, json=payload, timeout=30)
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response.raise_for_status()
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data = response.json()
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except requests.RequestException as exc: # pragma: no cover
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raise AltTextGenerationError(str(exc)) from exc
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choices = data.get("choices") or []
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if not choices:
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raise AltTextGenerationError("OpenAI response did not include choices")
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message = choices[0].get("message", {})
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content_text = message.get("content")
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if not content_text:
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raise AltTextGenerationError("OpenAI response missing content")
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return content_text.strip()
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def improve_post_text(
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self, draft_text: str, instructions: Optional[str] = None
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) -> str:
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if not draft_text or not draft_text.strip():
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raise TextImprovementError("Post text cannot be empty")
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prompt_parts = [
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"You review Mastodon drafts and rewrite them in UK English.",
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"Keep the tone warm, accessible, and descriptive without exaggeration.",
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"Ensure clarity, fix spelling or grammar, and keep content suitable for social media.",
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]
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if instructions:
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prompt_parts.append(f"Additional instructions: {instructions.strip()}")
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prompt_parts.append("Return only the improved post text.")
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user_content = f"Draft post:\\n{draft_text.strip()}"
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payload = {
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"model": self.model,
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"temperature": 0.4,
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"max_tokens": 400,
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"messages": [
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{"role": "system", "content": "\n".join(prompt_parts)},
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{"role": "user", "content": user_content},
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],
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}
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try:
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response = self.session.post(self.endpoint, json=payload, timeout=30)
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response.raise_for_status()
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data = response.json()
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except requests.RequestException as exc: # pragma: no cover
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raise TextImprovementError(str(exc)) from exc
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choices = data.get("choices") or []
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if not choices:
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raise TextImprovementError("OpenAI response did not include choices")
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content_text = choices[0].get("message", {}).get("content")
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if not content_text:
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raise TextImprovementError("OpenAI response missing content")
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return content_text.strip()
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