"""OCR pipeline: Paperless PDF -> per-page OCR -> per-page PDFs -> Paperless uploads.

This module is where the "business logic" lives.

Design goals:
- Keep the pipeline readable and linear.
- Return enough information (created ids) for the job API.
- Avoid hidden side-effects (everything is passed in / returned).

Upload strategy:
- All per-page PDFs are uploaded to Paperless concurrently (each upload still polls until a doc id exists).
- OCR (llama) runs one page at a time to respect VRAM.
- Each page is PATCHed once that page's upload has finished and OCR for that page is done.
"""

from __future__ import annotations

import asyncio
import io
import logging
import re
from collections.abc import Awaitable, Callable

from notebook_tools import pdf_utils
from notebook_tools.llama_client import LlamaClient
from notebook_tools.paperless_client import PaperlessClient
from notebook_tools.settings import Settings
from PIL import Image

logger = logging.getLogger("notebook_tools.pipeline")

PAGE_NUMBER_PROMPT = (
    "You are reading a handwritten page number in the bottom corner of a notebook page. "
    "Return ONLY the page number as an integer. If you cannot determine it, return -1. "
    "Do not output any other words."
)


def _crop_bottom_corner_jpegs(*, full_page_jpeg: bytes) -> list[bytes]:
    """Return small JPEG crops from bottom-left and bottom-right corners.

    Why crop?
    - It reduces visual clutter so the model focuses on the handwritten page number.
    - It reduces payload size, making OCR faster.

    The crop is based on percentages so it works across different page sizes.
    """

    img = Image.open(io.BytesIO(full_page_jpeg)).convert("RGB")
    w, h = img.size

    # Bottom band (e.g. last 20% of page height)
    band_h = int(h * 0.22)
    y0 = max(0, h - band_h)

    # Left/right corner width (e.g. 35% of page width)
    corner_w = int(w * 0.35)

    crops = [
        img.crop((0, y0, corner_w, h)),  # bottom-left
        img.crop((w - corner_w, y0, w, h)),  # bottom-right
    ]

    out: list[bytes] = []
    for c in crops:
        buf = io.BytesIO()
        c.save(buf, format="JPEG", quality=90, optimize=True)
        out.append(buf.getvalue())
    return out


def _parse_page_number(text: str) -> int | None:
    """Try to parse an integer page number from a model response.

    We accept:
    - '12'
    - 'Page 12' (if the model disobeys slightly)
    - '-1'
    """

    m = re.search(r"-?\d+", text)
    if not m:
        return None
    try:
        return int(m.group(0))
    except ValueError:
        return None


async def run_pipeline_for_paperless_document(
    *,
    settings: Settings,
    paperless_document_id: int,
    notebook_id: str,
    job_id: str,
    on_progress: Callable[[int, int], Awaitable[None]] | None,
    ocr_prompt_override: str | None,
    title_prefix: str | None,
) -> dict[str, list[int]]:
    """Run the full OCR pipeline for one Paperless document id.

    Returns:
        {"created_document_ids": [...]} where each id is a NEW Paperless document
        (one per page).
    """

    paperless = PaperlessClient(
        base_url=str(settings.paperless_base_url),
        token=settings.paperless_token,
        task_timeout_s=settings.paperless_task_timeout_s,
        task_poll_interval_s=settings.paperless_task_poll_interval_s,
    )
    llama = LlamaClient(
        base_url=str(settings.llama_base_url),
        model=settings.llama_model,
        temperature=settings.ocr_temperature,
        max_tokens=settings.ocr_max_tokens,
    )

    # 1) Download the source PDF.
    logger.info("job_id=%s downloading paperless_document_id=%s", job_id, paperless_document_id)
    pdf_bytes = await paperless.download_document_pdf(document_id=paperless_document_id)
    logger.info("job_id=%s downloaded_pdf_bytes=%s", job_id, len(pdf_bytes))

    # 2) Render the PDF pages as JPEG images.
    logger.info("job_id=%s rendering_pages dpi=%s", job_id, settings.render_dpi)
    jpegs = pdf_utils.render_pdf_to_jpegs(pdf_bytes=pdf_bytes, dpi=settings.render_dpi)
    total_pages = len(jpegs)
    logger.info("job_id=%s rendered_pages=%s", job_id, total_pages)
    if on_progress:
        await on_progress(0, total_pages)

    # One small PDF per page (used by upload tasks).
    page_pdfs = [pdf_utils.jpeg_to_pdf_bytes(jpeg_bytes=b) for b in jpegs]

    # 3) Start all Paperless uploads in parallel (each task waits for ingest + document id).
    conc = settings.paperless_upload_concurrency
    upload_sem: asyncio.Semaphore | None = (
        asyncio.Semaphore(conc) if conc and conc > 0 else None
    )
    logger.info(
        "job_id=%s starting_parallel_uploads pages=%s concurrency=%s",
        job_id,
        total_pages,
        conc if conc and conc > 0 else "unlimited",
    )

    async def _upload_one_page(idx_1based: int) -> int:
        filename = f"job_{job_id}_page_{idx_1based}.pdf"
        pdf_bytes = page_pdfs[idx_1based - 1]
        logger.info("job_id=%s page=%s/%s upload_task_starting", job_id, idx_1based, total_pages)
        if upload_sem is not None:
            async with upload_sem:
                return await paperless.upload_pdf(filename=filename, pdf_bytes=pdf_bytes)
        return await paperless.upload_pdf(filename=filename, pdf_bytes=pdf_bytes)

    upload_tasks: list[asyncio.Task[int]] = [
        asyncio.create_task(_upload_one_page(i)) for i in range(1, total_pages + 1)
    ]

    created_ids: list[int] = []

    # 4) OCR sequentially (VRAM), then await upload for that page + PATCH.
    try:
        for idx, jpeg_bytes in enumerate(jpegs, start=1):
            logger.info("job_id=%s page=%s/%s ocr_starting", job_id, idx, total_pages)
            # 4a) Page-number OCR (bottom corners only).
            page_number = -1
            for corner_jpeg in _crop_bottom_corner_jpegs(full_page_jpeg=jpeg_bytes):
                candidate_text = await llama.ocr_jpeg(jpeg_bytes=corner_jpeg, prompt=PAGE_NUMBER_PROMPT)
                parsed = _parse_page_number(candidate_text)
                if parsed is not None:
                    if parsed == -1 or parsed >= 0:
                        page_number = parsed
                        if page_number != -1:
                            break
            logger.info("job_id=%s page=%s detected_page_number=%s", job_id, idx, page_number)

            # 4b) Full-page OCR for searchable content.
            logger.info("job_id=%s page=%s ocr_full_page", job_id, idx)
            ocr_text = await llama.ocr_jpeg(jpeg_bytes=jpeg_bytes, prompt=ocr_prompt_override)
            logger.info("job_id=%s page=%s ocr_chars=%s", job_id, idx, len(ocr_text))

            logger.info("job_id=%s page=%s awaiting_upload_then_patch", job_id, idx)
            new_id = await upload_tasks[idx - 1]
            logger.info("job_id=%s page=%s uploaded_document_id=%s", job_id, idx, new_id)

            custom_fields = [
                {"field": settings.paperless_custom_field_notebook_id, "value": notebook_id},
                {"field": settings.paperless_custom_field_notebook_page, "value": page_number},
            ]

            title = f"Notebook {notebook_id} Page {page_number}"

            logger.info("job_id=%s page=%s patching_document_id=%s", job_id, idx, new_id)
            await paperless.patch_document(
                document_id=new_id,
                title=title,
                content=ocr_text,
                custom_fields=custom_fields,
                document_type=settings.paperless_document_type_id,
            )
            logger.info("job_id=%s page=%s patched_document_id=%s", job_id, idx, new_id)

            created_ids.append(new_id)
            if on_progress:
                await on_progress(idx, total_pages)
    except BaseException:
        for t in upload_tasks:
            if not t.done():
                t.cancel()
        await asyncio.gather(*upload_tasks, return_exceptions=True)
        raise

    return {"created_document_ids": created_ids}