"""Hàm phụ trợ đọc và nhận dạng file — R08-T12.

Thuần hàm, không widget. ``_is_probably_text`` là chỗ quyết định file
mở bằng ô soạn thảo hay báo là nhị phân — đoán sai thì người dùng thấy
một màn hình ký tự rác.
"""
from __future__ import annotations

from ...ui.libreoffice_view import DOC_SUFFIXES  # noqa: F401 — dùng lại ở cả gói

# Nhận dạng loại file và các ngưỡng — gom về đây vì cả sáu file trong gói
# đều hỏi tới, để rải ra thì mỗi lần thêm một đuôi file phải sửa vài chỗ.
try:
    from ...graph.graph_web import _HAS_WEB
except Exception:  # pragma: no cover
    _HAS_WEB = False

try:
    from PySide6.QtPdf import QPdfDocument  # noqa: F401
    from PySide6.QtPdfWidgets import QPdfView  # noqa: F401
    _HAS_PDF = True
except Exception:  # pragma: no cover - QtPdf not bundled
    _HAS_PDF = False

_IMAGE_SUFFIXES = {".png", ".jpg", ".jpeg", ".gif", ".bmp", ".webp", ".ico"}
_HTML_SUFFIXES = {".html", ".htm"}
_PPTX_SUFFIXES = {".pptx"}          # text-editable in-app via python-pptx (no PowerPoint)
_EXCEL_SUFFIXES = {".xlsx", ".xlsm"}  # viewed as a real table via openpyxl (no LibreOffice)
_MAX_EDIT_BYTES = 2_000_000        # above this, view read-only / note only
_MAX_HIGHLIGHT_CHARS = 300_000     # skip colouring huge files (keeps typing snappy)


import os
from pathlib import Path
from PySide6.QtCore import Qt
from PySide6.QtGui import QColor, QFont, QTextCharFormat
from ...i18n import tr


def _fmt(color: str, *, italic: bool = False, bold: bool = False) -> QTextCharFormat:
    f = QTextCharFormat()
    f.setForeground(QColor(color))
    if italic:
        f.setFontItalic(True)
    if bold:
        f.setFontWeight(QFont.Bold)
    return f


def _pptx_available() -> bool:
    """True when python-pptx is importable. If it's MISSING, auto-download &
    install it (via deps.ensure_module) so pptx editing 'just works' — cached so
    the (one-time) install is attempted only once."""
    global _PPTX_READY
    if _PPTX_READY is None:
        try:
            from ...core.deps import ensure_module
            _PPTX_READY = ensure_module("pptx", "python-pptx") is not None
        except Exception:  # noqa: BLE001
            _PPTX_READY = False
    return _PPTX_READY


def _split_code_block(text: str):
    """Split an AI reply into ``(file_content, summary)``. ``file_content`` is
    the first fenced code block (the edited file); ``summary`` is any prose
    before it. Returns ``(None, text)`` when there's no code block."""
    import re
    m = re.search(r"```[^\n]*\n(.*?)```", text or "", re.DOTALL)
    if not m:
        return None, (text or "")
    return m.group(1), (text[:m.start()].strip())


def _parse_ai_output(text: str):
    """Parse an AI edit reply into ``(target, content, summary, image_gens)``.
    ``FILE: <path>`` names a NEW file to create; ``IMAGE_GEN: <prompt> => <path>``
    lines request generated illustration images (relative paths)."""
    import re
    content, summary = _split_code_block(text)
    target = None
    m = re.search(r"(?mi)^\s*FILE:\s*(.+?)\s*$", text or "")
    if m:
        target = m.group(1).strip().strip("`\"'")
    image_gens = []
    for gm in re.finditer(r"(?mi)^\s*IMAGE_GEN:\s*(.+?)\s*=>\s*(\S+)\s*$", text or ""):
        image_gens.append((gm.group(1).strip(), gm.group(2).strip().strip("`\"'")))
    # Strip the directive lines out of the shown summary.
    summary = re.sub(r"(?mi)^\s*(FILE|IMAGE_GEN):\s*.+?$", "", summary).strip()
    return target, content, summary, image_gens


def _read_text(path: str) -> str:
    try:
        return Path(path).read_text(encoding="utf-8", errors="replace")
    except OSError as exc:
        return f"[could not read file: {exc}]"


def _is_probably_text(path: str) -> bool:
    try:
        with open(path, "rb") as f:
            chunk = f.read(4096)
    except OSError:
        return False
    if b"\x00" in chunk:
        return False
    try:
        chunk.decode("utf-8")
        return True
    except UnicodeDecodeError:
        # Latin-ish text still edits fine via errors="replace"; only reject on
        # a hard binary signal (NUL above), so most source files pass.
        return True