"""
FILE: app/core/parsing/parsing_markdown.py
DESCRIPTION: Fehlertolerantes Einlesen von Markdown und Frontmatter-Splitting.
"""
import io
import os
import json
from typing import Any, Dict, Optional, Tuple
from .parsing_models import ParsedNote
from .parsing_utils import FRONTMATTER_RE

try:
    import yaml
except ImportError:
    yaml = None

_FALLBACK_ENCODINGS: Tuple[str, ...] = ("utf-8", "utf-8-sig", "cp1252", "latin-1")

def _split_frontmatter(text: str) -> Tuple[Dict[str, Any], str]:
    """Zerlegt Text in Frontmatter-Dict und Body."""
    lines = text.splitlines(True)
    if not lines or not FRONTMATTER_RE.match(lines[0]):
        return {}, text
    end_idx = None
    for i in range(1, min(len(lines), 2000)):
        if FRONTMATTER_RE.match(lines[i]):
            end_idx = i
            break
    if end_idx is None: return {}, text
    fm_raw = "".join(lines[1:end_idx])
    body = "".join(lines[end_idx + 1:])
    if yaml is None: raise RuntimeError("PyYAML not installed.")
    try:
        loaded = yaml.safe_load(fm_raw) or {}
        data = loaded if isinstance(loaded, dict) else {}
    except Exception as e:
        print(json.dumps({"warn": "frontmatter_yaml_parse_failed", "error": str(e)}))
        data = {}
    if body.startswith("\n"): body = body[1:]
    return data, body

def _read_text_with_fallback(path: str) -> Tuple[str, str, bool]:
    """Liest Datei mit Encoding-Fallback-Kette."""
    last_err = None
    for enc in _FALLBACK_ENCODINGS:
        try:
            with io.open(path, "r", encoding=enc, errors="strict") as f:
                return f.read(), enc, (enc != "utf-8")
        except UnicodeDecodeError as e:
            last_err = str(e); continue
    with open(path, "rb") as fb:
        text = fb.read().decode("utf-8", errors="replace")
    return text, "utf-8(replace)", True

def read_markdown(path: str) -> Optional[ParsedNote]:
    """Öffentliche API zum Einlesen einer Datei."""
    if not os.path.exists(path): return None
    text, enc, had_fb = _read_text_with_fallback(path)
    fm, body = _split_frontmatter(text)
    return ParsedNote(frontmatter=fm or {}, body=body or "", path=path)