"""FlowDeck — PDF importer (v5.6.0, Phase 3).

Best-effort text + image extraction from a PDF into a FlowDeck page (fidelity
depends on the source PDF; scanned documents have no text layer).
"""
from __future__ import annotations

import io
import re
from pathlib import Path

from app.services.importers.base import (
    ImportAttachment,
    Importer,
    ImportPage,
    ImportResult,
    register_importer,
)

_MIME = {".png": "image/png", ".jpg": "image/jpeg", ".jpeg": "image/jpeg",
         ".gif": "image/gif", ".webp": "image/webp", ".bmp": "image/bmp",
         ".tiff": "image/tiff", ".tif": "image/tiff"}


@register_importer
class PdfImporter(Importer):
    source_id = "pdf"
    label = "PDF"
    description = "Extraction texte + images d'un PDF (fidélité limitée)."
    extensions = (".pdf",)
    order = 37

    def detect(self, filename: str, data: bytes) -> bool:
        return filename.lower().endswith(".pdf")

    def parse(self, filename: str, data: bytes) -> ImportResult:
        result = ImportResult(source=self.source_id)
        try:
            from pypdf import PdfReader
        except ImportError:
            result.warn("pypdf n'est pas installé : import PDF indisponible")
            return result.finalize()
        try:
            reader = PdfReader(io.BytesIO(data))
        except Exception as exc:  # noqa: BLE001
            result.warn(f"PDF illisible : {exc}")
            return result.finalize()

        chunks: list[str] = []
        empty_pages = 0
        for index, page in enumerate(reader.pages, start=1):
            try:
                text = (page.extract_text() or "").strip()
            except Exception:  # noqa: BLE001
                text = ""
            if text:
                if len(reader.pages) > 1:
                    chunks.append(f"## Page {index}\n\n{text}")
                else:
                    chunks.append(text)
            else:
                empty_pages += 1
            chunks.extend(self._page_images(page, index, result))

        if empty_pages:
            result.warn(f"{empty_pages} page(s) sans couche texte (document scanné ?)")
        markdown = re.sub(r"\n{3,}", "\n\n", "\n\n".join(chunks)).strip()
        title = Path(filename).stem or "Document"
        result.pages.append(ImportPage(
            title=title, markdown=markdown, source_path=filename, external_id=filename,
        ))
        return result.finalize()

    def _page_images(self, page, index: int, result: ImportResult) -> list[str]:
        images: list[str] = []
        try:
            page_images = list(page.images)
        except Exception:  # noqa: BLE001
            return images
        for i, image in enumerate(page_images, start=1):
            name = getattr(image, "name", "") or f"page{index}_img{i}.png"
            name = Path(name).name
            try:
                payload = image.data
            except Exception:  # noqa: BLE001
                continue
            if not payload:
                continue
            result.attachments.append(ImportAttachment(
                source_path=f"page{index}/{name}", filename=name, data=payload,
                mime=_MIME.get(Path(name).suffix.lower(), "application/octet-stream"),
            ))
            images.append(f"![{name}]({name})")
        return images