from __future__ import annotations

from pathlib import Path
from typing import Any
import hashlib
import tempfile

try:
    import fitz  # PyMuPDF
except Exception:  # pragma: no cover
    fitz = None

try:
    import cv2
except Exception:  # pragma: no cover
    cv2 = None


def _render_pdf_page_to_png(path: Path, *, page_number: int = 0, dpi: int = 200) -> dict[str, Any]:
    if fitz is None:
        return {
            "status": "render_failed",
            "error": "pymupdf_not_available",
            "rendered_pages": [],
        }

    cache_root = Path(tempfile.gettempdir()) / "document_processor_vision"
    cache_root.mkdir(parents=True, exist_ok=True)

    digest = hashlib.sha256(str(path).encode("utf-8")).hexdigest()[:16]
    png_path = cache_root / f"{path.stem}_{digest}_page{page_number + 1}_{dpi}dpi.png"

    doc = fitz.open(str(path))
    try:
        page_count = doc.page_count
        if page_count <= page_number:
            return {
                "status": "render_failed",
                "error": "page_number_out_of_range",
                "page_count": page_count,
                "rendered_pages": [],
            }

        page = doc.load_page(page_number)
        matrix = fitz.Matrix(dpi / 72.0, dpi / 72.0)
        pix = page.get_pixmap(matrix=matrix, alpha=False)
        pix.save(str(png_path))

        return {
            "status": "image_rendered",
            "page_count": page_count,
            "rendered_pages": [
                {
                    "page": page_number + 1,
                    "png_path": str(png_path),
                    "width": pix.width,
                    "height": pix.height,
                    "dpi": dpi,
                }
            ],
        }
    finally:
        doc.close()



def _detect_visual_regions(png_path: str | Path) -> list[dict[str, Any]]:
    """
    Detect coarse visual/text regions from a rendered document image.

    This is intentionally conservative. It does not replace OCR boxes yet;
    it gives the vision pipeline a first set of image-derived regions that
    can later be scored, merged, or sent to a VLM.
    """
    if cv2 is None:
        return []

    img = cv2.imread(str(png_path))
    if img is None:
        return []

    height, width = img.shape[:2]
    page_area = float(width * height)

    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

    # Convert dark text/lines to white foreground.
    thresh = cv2.adaptiveThreshold(
        gray,
        255,
        cv2.ADAPTIVE_THRESH_GAUSSIAN_C,
        cv2.THRESH_BINARY_INV,
        35,
        15,
    )

    # Merge nearby characters into coarse rows/regions.
    kernel_w = max(12, width // 90)
    kernel_h = max(3, height // 350)
    kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (kernel_w, kernel_h))
    merged = cv2.dilate(thresh, kernel, iterations=2)

    contours, _ = cv2.findContours(merged, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)

    regions: list[dict[str, Any]] = []
    for contour in contours:
        x, y, w, h = cv2.boundingRect(contour)
        area = float(w * h)

        if area < page_area * 0.00008:
            continue
        if w < width * 0.04 or h < 4:
            continue
        if area > page_area * 0.65:
            continue

        regions.append(
            {
                "bbox": [int(x), int(y), int(x + w), int(y + h)],
                "label": "cv_region",
                "confidence": 0.35,
                "source": "opencv_adaptive_threshold_contours",
                "page": 1,
            }
        )

    # Stable reading-ish order.
    regions.sort(key=lambda r: (r["bbox"][1], r["bbox"][0]))

    # Avoid huge payloads for now.
    return regions[:200]

def analyze_document_image(image_path: str | Path, *, model_name: str = "placeholder") -> dict[str, Any]:
    """
    Backend-only vision analysis entrypoint.

    Current phase:
    - renders the first PDF page to PNG
    - returns normalized metadata for later CV/Ollama processing
    """
    path = Path(image_path)

    render_result: dict[str, Any]
    if path.exists() and path.suffix.lower() == ".pdf":
        render_result = _render_pdf_page_to_png(path)
    elif path.exists():
        render_result = {
            "status": "image_available",
            "rendered_pages": [
                {
                    "page": 1,
                    "png_path": str(path),
                    "width": None,
                    "height": None,
                    "dpi": None,
                }
            ],
        }
    else:
        render_result = {
            "status": "source_missing",
            "error": "image_path_does_not_exist",
            "rendered_pages": [],
        }

    rendered_pages = render_result.get("rendered_pages") or []
    vision_regions: list[dict[str, Any]] = []
    if rendered_pages and rendered_pages[0].get("png_path"):
        vision_regions = _detect_visual_regions(rendered_pages[0]["png_path"])

    return {
        "schema_version": "vision_analysis_v1",
        "engine": "local",
        "model_name": model_name,
        "image_path": str(path),
        **render_result,
        "layers": {
            "vision_regions": vision_regions,
            "vision_lines": [],
            "vision_boxes": [],
            "vision_fields": [],
            "vision_line_items": [],
        },
        "notes": [
            "Vision module rendered/located image input.",
            "OpenCV coarse region detection has run when available.",
            "No CV/Ollama model is connected yet.",
        ],
    }


def build_vision_assisted_layout(source_layout: dict[str, Any] | None, vision_result: dict[str, Any]) -> dict[str, Any]:
    """
    Convert vision analysis into normal layout_json.

    Current phase:
    - preserves the current source layout
    - tags it as vision-assisted
    """
    layout = dict(source_layout or {"pages": []})
    layout["vision_assisted"] = True
    layout["vision_assisted_status"] = vision_result.get("status", "unknown")
    layout["vision_engine"] = vision_result.get("engine")
    layout["vision_model_name"] = vision_result.get("model_name")
    layout["layout_sync_source"] = "vision_assisted"
    layout["layout_needs_review"] = True
    return layout