"""
utils.py — PDF extraction, Gemini LLM, email, Catbox upload helpers.
"""

from __future__ import annotations

import os
import re
import smtplib
import ssl
import time
from email.message import EmailMessage
from pathlib import Path

import requests
from google import genai
from google.genai import types

# ── PDF Text Extraction ───────────────────────────────────────────────────────

def extract_pdf_text(pdf_path: str) -> str:
    """Extract plain text from a PDF using pypdf."""
    from pypdf import PdfReader

    reader = PdfReader(pdf_path)
    pages = []
    for page in reader.pages:
        text = page.extract_text()
        if text:
            pages.append(text)
    return "\n\n".join(pages)


# ── Gemini LLM ────────────────────────────────────────────────────────────────

def generate_manim_code(prompt_text: str, api_key: str) -> str:
    """Stream Manim code from Gemini."""
    client = genai.Client(api_key=api_key)
    model = "gemini-2.5-flash-preview-05-20"  # latest stable flash model
    contents = [
        types.Content(role="user", parts=[types.Part.from_text(prompt_text)])
    ]
    config = types.GenerateContentConfig(
        thinking_config=types.ThinkingConfig(thinking_budget=8192)
    )

    code = ""
    for chunk in client.models.generate_content_stream(
        model=model, contents=contents, config=config
    ):
        if chunk.text:
            code += chunk.text
    return code


def sanitize_manim_code(raw: str, job_id: str) -> str:
    """
    Strip markdown fences, ensure correct imports and class name,
    and add job-specific media dir hint.
    """
    # Remove ```python ... ``` fences
    code = re.sub(r"^```(?:python)?\s*", "", raw.strip(), flags=re.MULTILINE)
    code = re.sub(r"\s*```$", "", code.strip(), flags=re.MULTILINE)

    # Ensure manim import is present
    if "from manim import" not in code and "import manim" not in code:
        code = "from manim import *\n\n" + code

    # Ensure class is named OutputVideo
    code = re.sub(r"class\s+\w+\s*\(\s*Scene\s*\)", "class OutputVideo(Scene)", code)

    return code


# ── Email ─────────────────────────────────────────────────────────────────────

def send_video_email(
    to_email: str,
    video_path: str | None = None,
    catbox_url: str | None = None,
) -> None:
    """Send email with video attachment or Catbox link."""
    smtp_email = os.environ["SMTP_EMAIL"]
    smtp_password = os.environ["SMTP_PASSWORD"]

    msg = EmailMessage()
    msg["Subject"] = "🎬 Your Manim Animation is Ready!"
    msg["From"] = smtp_email
    msg["To"] = to_email

    if catbox_url:
        body = (
            "Your animated video has been generated and uploaded.\n\n"
            f"Download it here (link valid for ~3 days):\n{catbox_url}\n\n"
            "Enjoy your animation!"
        )
        msg.set_content(body)
    else:
        msg.set_content(
            "Your animated video is attached to this email.\n\nEnjoy your animation!"
        )
        with open(video_path, "rb") as f:
            msg.add_attachment(
                f.read(),
                maintype="video",
                subtype="mp4",
                filename="animation.mp4",
            )

    context = ssl.create_default_context()
    _smtp_send_with_retry(msg, smtp_email, smtp_password, context)

    # Delete video after successful send
    if video_path and Path(video_path).exists():
        Path(video_path).unlink(missing_ok=True)


def _smtp_send_with_retry(
    msg: EmailMessage,
    smtp_email: str,
    smtp_password: str,
    context: ssl.SSLContext,
    max_retries: int = 3,
) -> None:
    backoff = 2
    for attempt in range(max_retries):
        try:
            with smtplib.SMTP_SSL("smtp.gmail.com", 465, context=context) as server:
                server.login(smtp_email, smtp_password)
                server.send_message(msg)
            return
        except smtplib.SMTPException as exc:
            if attempt == max_retries - 1:
                raise
            time.sleep(backoff)
            backoff *= 2


# ── Catbox Upload ─────────────────────────────────────────────────────────────

API_URL = "https://catbox.moe/user/api.php"


def upload_to_catbox(path: str, max_retries: int = 5) -> str:
    """Upload a file to Catbox.moe with exponential backoff."""
    file_path = Path(path)
    backoff = 1
    for attempt in range(max_retries):
        try:
            with file_path.open("rb") as f:
                r = requests.post(
                    API_URL,
                    data={"reqtype": "fileupload"},
                    files={"fileToUpload": f},
                    timeout=120,
                )
            if r.status_code == 200 and r.text.startswith("https://files.catbox.moe/"):
                return r.text.strip()
            raise RuntimeError(f"Catbox returned unexpected response: {r.text[:200]}")
        except Exception:
            if attempt == max_retries - 1:
                raise
            time.sleep(backoff)
            backoff *= 2
    raise RuntimeError("Catbox upload failed after all retries.")