"""
Grid Build Core — the main _build_grid_core() function.

Extracted from grid_editor_api.py for maintainability.
Takes merged OCR word positions and builds a structured, zone-aware grid.

The function delegates to phase-specific modules:
- grid_build_zones.py   — image loading, graphic/box detection, zone grids
- grid_build_cleanup.py — junk rows, artifacts, pipes, border strips
- grid_build_text_ops.py — color, headings, IPA, page refs
- grid_build_finalize.py — bullets, max_columns, dictionary, spelling, result
"""

import logging
import time
from typing import Any, Dict, List, Optional

from grid_editor_helpers import (
    _flatten_word_boxes,
    _get_content_bounds,
    _filter_decorative_margin,
    _filter_footer_words,
    _filter_header_junk,
)

from grid_build_zones import _build_zones
from grid_build_cleanup import _cleanup_zones
from grid_build_text_ops import _process_text
from grid_build_finalize import _finalize_grid

logger = logging.getLogger(__name__)


async def _build_grid_core(
    session_id: str,
    session: dict,
    *,
    ipa_mode: str = "auto",
    syllable_mode: str = "auto",
    enhance: bool = True,
    max_columns: Optional[int] = None,
    min_conf: Optional[int] = None,
) -> dict:
    """Core grid building logic — pure computation, no HTTP or DB side effects.

    Args:
        session_id: Session identifier (for logging and image loading).
        session: Full session dict from get_session_db().
        ipa_mode: "auto" (only when English headwords detected), "all"
            (force IPA on all content columns), "en" (English column only),
            "de" (German/definition columns only), or "none" (skip entirely).
        syllable_mode: "auto" (only when original has pipe dividers),
            "all" (force syllabification on all words), "en" (English only),
            "de" (German only), or "none" (skip).

    Returns:
        StructuredGrid result dict.

    Raises:
        ValueError: If session data is incomplete.
    """
    t0 = time.time()

    # ── Phase 1: Input Validation & Word Filtering ──────────────────

    # 1. Validate and load word results
    word_result = session.get("word_result")
    if not word_result or not word_result.get("cells"):
        raise ValueError("No word results found. Run paddle-kombi or rapid-kombi first.")

    img_w = word_result.get("image_width", 0)
    img_h = word_result.get("image_height", 0)
    if not img_w or not img_h:
        raise ValueError("Missing image dimensions in word_result")

    # 2. Flatten all word boxes from cells
    all_words = _flatten_word_boxes(word_result["cells"])
    if not all_words:
        raise ValueError("No word boxes found in cells")

    # 2a-pre. Apply min_conf filter if specified
    if min_conf and min_conf > 0:
        before = len(all_words)
        all_words = [w for w in all_words if w.get('conf', 100) >= min_conf]
        removed = before - len(all_words)
        if removed:
            logger.info("build-grid session %s: min_conf=%d removed %d/%d words",
                        session_id, min_conf, removed, before)

    logger.info("build-grid session %s: %d words from %d cells (enhance=%s, max_cols=%s, min_conf=%s)",
                session_id, len(all_words), len(word_result["cells"]),
                enhance, max_columns, min_conf)

    # 2b. Filter decorative margin columns (alphabet graphics)
    margin_strip_info = _filter_decorative_margin(all_words, img_w, logger, session_id)
    margin_strip_detected = margin_strip_info.get("found", False)

    # Read document_category from session
    document_category = session.get("document_category")

    # 2c. Filter footer rows (page numbers at the very bottom)
    page_number_info = _filter_footer_words(all_words, img_h, logger, session_id)

    # 2c2. Filter OCR junk from header illustrations
    _filter_header_junk(all_words, img_h, logger, session_id)

    # 2d. Filter words inside user-defined exclude regions
    structure_result = session.get("structure_result")
    exclude_rects = []
    if structure_result:
        for er in structure_result.get("exclude_regions", []):
            exclude_rects.append({
                "x": er["x"], "y": er["y"],
                "w": er["w"], "h": er["h"],
            })
    if exclude_rects:
        before = len(all_words)
        filtered = []
        for w in all_words:
            w_cx = w["left"] + w.get("width", 0) / 2
            w_cy = w["top"] + w.get("height", 0) / 2
            inside = any(
                er["x"] <= w_cx <= er["x"] + er["w"]
                and er["y"] <= w_cy <= er["y"] + er["h"]
                for er in exclude_rects
            )
            if not inside:
                filtered.append(w)
        removed = before - len(filtered)
        if removed:
            all_words = filtered
            logger.info(
                "build-grid session %s: removed %d words inside %d user exclude region(s)",
                session_id, removed, len(exclude_rects),
            )

    # 2e. Hard-filter words inside graphic/image regions from structure step
    graphic_rects: List[Dict[str, int]] = []
    if structure_result:
        for g in structure_result.get("graphics", []):
            graphic_rects.append({
                "x": g["x"], "y": g["y"],
                "w": g["w"], "h": g["h"],
            })
    if graphic_rects:
        before = len(all_words)
        all_words = [
            w for w in all_words
            if not any(
                gr["x"] <= w["left"] + w.get("width", 0) / 2 <= gr["x"] + gr["w"]
                and gr["y"] <= w["top"] + w.get("height", 0) / 2 <= gr["y"] + gr["h"]
                for gr in graphic_rects
            )
        ]
        removed = before - len(all_words)
        if removed:
            logger.info(
                "build-grid session %s: hard-removed %d words inside %d structure graphic region(s)",
                session_id, removed, len(graphic_rects),
            )

    content_x, content_y, content_w, content_h = _get_content_bounds(all_words)

    # ── Phase 2: Image Processing & Zone Detection ──────────────────

    zone_result = await _build_zones(
        session_id, session, all_words, graphic_rects,
        content_x, content_y, content_w, content_h,
        img_w, img_h,
    )
    zones_data = zone_result["zones_data"]
    boxes_detected = zone_result["boxes_detected"]
    recovered_count = zone_result["recovered_count"]
    border_prefiltered = zone_result["border_prefiltered"]
    img_bgr = zone_result["img_bgr"]

    # ── Phase 3: Junk Removal & Cell Cleanup ────────────────────────

    border_prefiltered = _cleanup_zones(zones_data, border_prefiltered, session_id)

    # ── Phase 4+5a: Color, Headings, IPA, Page Refs ─────────────────

    text_result = _process_text(
        zones_data, img_bgr, img_w, img_h, ipa_mode, page_number_info,
    )

    # ── Phase 5b+6: Finalize & Result Assembly ──────────────────────

    duration = time.time() - t0

    result = _finalize_grid(
        zones_data=zones_data,
        all_words=all_words,
        img_bgr=img_bgr,
        img_w=img_w,
        img_h=img_h,
        session_id=session_id,
        max_columns=max_columns,
        ipa_mode=ipa_mode,
        syllable_mode=syllable_mode,
        en_col_type=text_result["en_col_type"],
        ipa_target_cols=text_result["ipa_target_cols"],
        all_content_cols=text_result["all_content_cols"],
        skip_ipa=text_result["skip_ipa"],
        document_category=document_category,
        margin_strip_detected=margin_strip_detected,
        page_number_info=text_result["page_number_info"],
        boxes_detected=boxes_detected,
        recovered_count=recovered_count,
        duration=duration,
    )

    return result