from __future__ import annotations

import hashlib
from pathlib import Path


IMAGE_SUFFIXES = {".png", ".jpg", ".jpeg", ".webp", ".svg"}
DOCUMENT_SUFFIXES = {".txt", ".md", ".csv", ".json", ".pdf", ".dxf", ".step", ".stp"}
MAX_IMAGE_BYTES = 10 * 1024 * 1024
MAX_DOCUMENT_BYTES = 2 * 1024 * 1024
MAX_EXTRACTED_CHARS = 30_000


def classify_upload(filename: str, mime: str, size: int) -> str:
    suffix = Path(filename).suffix.lower()
    if suffix in IMAGE_SUFFIXES or mime.startswith("image/"):
        if size > MAX_IMAGE_BYTES:
            raise ValueError("Image upload exceeds the 10 MB limit")
        return "image"
    if suffix in DOCUMENT_SUFFIXES:
        if size > MAX_DOCUMENT_BYTES:
            raise ValueError("Document upload exceeds the 2 MB limit")
        return "document"
    raise ValueError("Only PNG, JPG, WEBP, SVG, TXT, MD, CSV, JSON, PDF, DXF, and STEP/STP uploads are supported")


def extract_document_text(data: bytes) -> str:
    # PDF extraction is optional so the API can still accept a reference when
    # the local PDF dependency is unavailable; the binary remains available as
    # the primary attachment artifact.
    if data.startswith(b"%PDF"):
        try:
            from pypdf import PdfReader
            import io
            return "\n".join(page.extract_text() or "" for page in PdfReader(io.BytesIO(data)).pages)[:MAX_EXTRACTED_CHARS]
        except Exception:
            return "[PDF reference uploaded; text extraction unavailable]"
    try:
        text = data.decode("utf-8")
    except UnicodeDecodeError as error:
        return "[Binary CAD reference uploaded; structured geometry inspection is deferred to the CAD reference analyzer]"
    return text[:MAX_EXTRACTED_CHARS]


def attachment_record(conversation_id: str, filename: str, mime: str, relative_path: str, data: bytes, kind: str, extracted_path: str = "") -> dict[str, object]:
    return {
        "id": Path(relative_path).stem,
        "conversation_id": conversation_id,
        "name": filename,
        "kind": kind,
        "path": relative_path,
        "mime": mime or "application/octet-stream",
        "size": len(data),
        "sha256": hashlib.sha256(data).hexdigest(),
        "extracted_path": extracted_path,
    }