from __future__ import annotations
from dataclasses import dataclass
from typing import List, Dict, Optional, Tuple, Any
import re
import math
import yaml
from pathlib import Path
from markdown_it import MarkdownIt
from markdown_it.token import Token
import asyncio # Notwendig für asynchrone Chunking-Strategien

# NEUE IMPORTS
# Import der benötigten Klassen direkt (ersetzt get_semantic_analyzer)
# ANNAHME: Die Klassen existieren in app/services/semantic_analyzer.py
try:
    from app.services.semantic_analyzer import SemanticAnalyzer, SemanticChunkResult 
except ImportError:
    # Fallback für Tests, wenn der Service noch nicht auf dem Pfad ist
    print("WARNUNG: SemanticAnalyzer Service nicht gefunden. Semantic Chunking wird fehlschlagen.")
    class SemanticAnalyzer:
        async def analyze_and_chunk(self, text, type): return []
    @dataclass
    class SemanticChunkResult:
        content: str
        suggested_edges: List[str] # Format: "kind:Target"

# Import zum Auslesen des Frontmatters
# ANNAHME: extract_frontmatter_from_text existiert in app.core.note_payload
from app.core.note_payload import extract_frontmatter_from_text 


# ==========================================
# 1. CONFIGURATION LOADER (Ehemals chunk_config.py)
# ==========================================

# Pfad-Logik: app/core/chunker.py -> app/core -> app -> root/config/types.yaml
BASE_DIR = Path(__file__).resolve().parent.parent.parent
CONFIG_PATH = BASE_DIR / "config" / "types.yaml"

# Fallback Values
DEFAULT_PROFILE = {
    "strategy": "sliding_window",
    "target": 400,
    "max": 600,
    "overlap": (50, 80)
}

_CONFIG_CACHE = None

def _load_yaml_config() -> Dict[str, Any]:
    """Lädt die config/types.yaml und cached das Ergebnis."""
    global _CONFIG_CACHE
    if _CONFIG_CACHE is not None:
        return _CONFIG_CACHE

    if not CONFIG_PATH.exists():
        print(f"WARNUNG: types.yaml nicht gefunden unter: {CONFIG_PATH}")
        return {}

    try:
        with open(CONFIG_PATH, "r", encoding="utf-8") as f:
            data = yaml.safe_load(f)
            _CONFIG_CACHE = data
            return data
    except Exception as e:
        print(f"FEHLER beim Laden von {CONFIG_PATH}: {e}")
        return {}

def get_chunk_config(note_type: str) -> Dict[str, Any]:
    """Löst Typ -> Profil -> Konfiguration auf."""
    full_config = _load_yaml_config()
    
    profiles = full_config.get("chunking_profiles", {})
    type_def = full_config.get("types", {}).get(note_type.lower(), {})
    profile_name = type_def.get("chunking_profile")
    
    if not profile_name:
        profile_name = full_config.get("defaults", {}).get("chunking_profile", "sliding_standard")
    
    config = profiles.get(profile_name, DEFAULT_PROFILE).copy()
    
    if "overlap" in config and isinstance(config["overlap"], list):
        config["overlap"] = tuple(config["overlap"])
        
    return config

# Legacy Support
def get_sizes(note_type: str):
    cfg = get_chunk_config(note_type)
    return {
        "target": (cfg["target"], cfg["target"]),
        "max": cfg["max"],
        "overlap": cfg["overlap"]
    }

# ==========================================
# 2. DATA CLASSES & HELPERS
# ==========================================

# --- Hilfen ---
_SENT_SPLIT = re.compile(r'(?<=[.!?])\s+(?=[A-ZÄÖÜ0-9„(])')
_WS = re.compile(r'\s+')

def estimate_tokens(text: str) -> int:
    t = len(text.strip())
    return max(1, math.ceil(t / 4))

def split_sentences(text: str) -> list[str]:
    text = _WS.sub(' ', text.strip())
    if not text: return []
    parts = _SENT_SPLIT.split(text)
    return [p.strip() for p in parts if p.strip()]

@dataclass
class RawBlock:
    kind: str             
    text: str
    level: Optional[int]  
    section_path: str     
    section_title: Optional[str]

@dataclass
class Chunk:
    id: str
    note_id: str
    index: int
    text: str           # Reintext für Anzeige (inkl. injizierter Links bei LLM/Heading)
    window: str         # Text + Context für Embeddings 
    token_count: int
    section_title: Optional[str]
    section_path: str
    neighbors_prev: Optional[str]
    neighbors_next: Optional[str]
    char_start: int
    char_end: int

# --- Markdown Parser ---
def parse_blocks(md_text: str) -> Tuple[List[RawBlock], str]:
    """Parst MD und gibt Blöcke UND den H1 Titel zurück."""
    # Im echten Mindnet-System würde hier die komplexe Logik stehen.
    
    md = MarkdownIt("commonmark").enable("table")
    tokens: List[Token] = md.parse(md_text)

    blocks: List[RawBlock] = []
    h1_title = "Dokument" 
    h2, h3 = None, None
    section_path = "/"
    
    # Rudimentäres Block-Parsing für non-LLM Strategien (zur Wahrung der Struktur)
    text_without_fm = re.sub(r'---.*?---', '', md_text, flags=re.DOTALL)
    
    if text_without_fm.strip():
         blocks.append(RawBlock(kind="paragraph", text=text_without_fm.strip(), 
                                level=None, section_path=section_path, section_title=h2))

    # Realistischer wäre die Extraktion des H1 Titels hier
    h1_match = re.search(r'^#\s+(.*)', text_without_fm, re.MULTILINE)
    if h1_match:
        h1_title = h1_match.group(1).strip()
    
    return blocks, h1_title

# ==========================================
# 3. STRATEGIES (SYNCHRON)
# ==========================================

def _strategy_sliding_window(blocks: List[RawBlock], config: Dict[str, Any], note_id: str, context_prefix: str = "") -> List[Chunk]:
    """Klassisches Sliding Window."""
    target = config.get("target", 400)
    max_tokens = config.get("max", 600)
    overlap_val = config.get("overlap", (50, 80))
    overlap = sum(overlap_val) // 2 if isinstance(overlap_val, tuple) else overlap_val
    
    chunks: List[Chunk] = []
    buf: List[RawBlock] = []
    
    def flush_buffer():
        nonlocal buf
        if not buf: return
        text_body = "\n\n".join([b.text for b in buf])
        sec_title = buf[-1].section_title if buf else None
        sec_path = buf[-1].section_path if buf else "/"
        window_body = f"{context_prefix}\n{text_body}".strip() if context_prefix else text_body

        if estimate_tokens(text_body) > max_tokens:
            sentences = split_sentences(text_body)
            current_sents = []
            cur_toks = 0
            for s in sentences:
                st = estimate_tokens(s)
                if cur_toks + st > target and current_sents:
                    txt = "\n".join(current_sents)
                    win = f"{context_prefix}\n{txt}".strip() if context_prefix else txt
                    _add_chunk(txt, win, sec_title, sec_path)
                    ov_txt = " ".join(current_sents)[-overlap*4:]
                    current_sents = [ov_txt, s] if ov_txt else [s]
                    cur_toks = estimate_tokens(" ".join(current_sents))
                else:
                    current_sents.append(s)
                    cur_toks += st
            if current_sents:
                 txt = "\n".join(current_sents)
                 win = f"{context_prefix}\n{txt}".strip() if context_prefix else txt
                 _add_chunk(txt, win, sec_title, sec_path)
        else:
            _add_chunk(text_body, window_body, sec_title, sec_path)
        buf = []

    def _add_chunk(txt, win, sec, path):
        idx = len(chunks)
        chunks.append(Chunk(
            id=f"{note_id}#c{idx:02d}", note_id=note_id, index=idx,
            text=txt, window=win, token_count=estimate_tokens(txt),
            section_title=sec, section_path=path,
            neighbors_prev=None, neighbors_next=None, char_start=0, char_end=0
        ))

    for b in blocks:
        if estimate_tokens("\n\n".join([x.text for x in buf] + [b.text])) >= target:
            flush_buffer()
        buf.append(b)
    flush_buffer()
    return chunks

def _strategy_by_heading(blocks: List[RawBlock], config: Dict[str, Any], note_id: str, doc_title: str) -> List[Chunk]:
    """Harter Split an Überschriften mit Context Injection."""
    chunks: List[Chunk] = []
    sections: Dict[str, List[RawBlock]] = {}
    ordered = []
    
    # Anmerkung: Die ursprüngliche parse_blocks Logik zur H-Erkennung war detaillierter.
    # Hier verwenden wir die rudimentäre RawBlock-Struktur.
    
    for b in blocks:
        if b.kind == "heading": continue
        if b.section_path not in sections:
            sections[b.section_path] = []
            ordered.append(b.section_path)
        sections[b.section_path].append(b)
        
    for path in ordered:
        s_blocks = sections[path]
        if not s_blocks: continue
        
        breadcrumbs = path.strip("/").replace("/", " > ")
        context_header = f"# {doc_title}\n## {breadcrumbs}"
        full_text = "\n\n".join([b.text for b in s_blocks])
        
        if estimate_tokens(full_text) <= config.get("max", 600):
            chunks.append(Chunk(
                id=f"{note_id}#c{len(chunks):02d}", note_id=note_id, index=len(chunks),
                text=full_text, window=f"{context_header}\n{full_text}",
                token_count=estimate_tokens(full_text),
                section_title=s_blocks[0].section_title if s_blocks else None, 
                section_path=path,
                neighbors_prev=None, neighbors_next=None, char_start=0, char_end=0
            ))
        else:
            # Fallback auf Sliding Window mit Context Injection
            sub = _strategy_sliding_window(s_blocks, config, note_id, context_prefix=context_header)
            base = len(chunks)
            for i, sc in enumerate(sub):
                sc.index = base + i
                sc.id = f"{note_id}#c{sc.index:02d}"
                chunks.append(sc)
    return chunks

# ==========================================
# 4. STRATEGY (ASYNCHRON)
# ==========================================

# Singleton Instanz für den Analyzer
_semantic_analyzer_instance = None

def _get_semantic_analyzer_instance() -> SemanticAnalyzer:
    """Liefert die Singleton-Instanz des SemanticAnalyzer."""
    global _semantic_analyzer_instance
    if _semantic_analyzer_instance is None:
        _semantic_analyzer_instance = SemanticAnalyzer()
    return _semantic_analyzer_instance

async def _strategy_semantic_llm(md_text: str, config: Dict[str, Any], note_id: str, note_type: str) -> List[Chunk]:
    """
    Strategie: Delegiert die Zerlegung und Kanten-Extraktion an ein LLM (Async).
    """
    analyzer = _get_semantic_analyzer_instance()
    
    # Text-Splitting wird hier vom LLM übernommen
    semantic_chunks: List[SemanticChunkResult] = await analyzer.analyze_and_chunk(md_text, note_type)
    
    chunks: List[Chunk] = []
    
    for i, sc in enumerate(semantic_chunks):
        # 1. Edge Injection für derive_edges.py
        injection_block = "\n"
        for edge_str in sc.suggested_edges:
            # Stellt sicher, dass das Split-Ergebnis 2 Teile hat
            if ":" in edge_str:
                kind, target = edge_str.split(":", 1)
                # Nutzt die Syntax: [[rel:kind | Target]]
                injection_block += f"[[rel:{kind} | {target}]] "
            
        full_text = sc.content + injection_block
        
        # 2. Chunk Objekt bauen
        chunks.append(Chunk(
            id=f"{note_id}#sem{i:02d}",
            note_id=note_id,
            index=i,
            text=full_text.strip(),     
            window=full_text.strip(),   
            token_count=estimate_tokens(full_text),
            section_title="Semantic Section",
            section_path="/LLM",
            neighbors_prev=None, neighbors_next=None,
            char_start=0, char_end=0
        ))
        
    return chunks

# ==========================================
# 5. MAIN ENTRY POINT (ASYNC)
# ==========================================

async def assemble_chunks(note_id: str, md_text: str, note_type: str) -> List[Chunk]:
    """
    Hauptfunktion. Analysiert Config und wählt Strategie (MUSS ASYNC SEIN).
    Enthält die Logik zur Vermeidung des Double-LLM-Effekts.
    """
    
    # 1. Frontmatter prüfen (Double-LLM-Prevention)
    fm, _ = extract_frontmatter_from_text(md_text) 
    note_status = fm.get("status", "").lower()
    
    config = get_chunk_config(note_type)
    strategy = config.get("strategy", "sliding_window")

    # 2. Strategie-Auswahl
    
    # Wenn der Typ LLM-Chunking nutzt (semantic_llm),
    # ABER der Status ist 'draft' (wahrscheinlich vom LLM generiert):
    if strategy == "semantic_llm" and note_status in ["draft", "initial_gen"]:
        # Setze auf die zweitbeste, aber synchrone und deterministische Strategie
        print(f"INFO: Overriding '{strategy}' for draft status. Using 'by_heading' instead.")
        strategy = "by_heading" # Fallback auf by_heading, da LLM-Generatoren saubere H2-Strukturen nutzen.
    
    # 3. Execution (Dispatcher)
    
    if strategy == "semantic_llm":
        chunks = await _strategy_semantic_llm(md_text, config, note_id, note_type)
    
    elif strategy == "by_heading":
        blocks, doc_title = parse_blocks(md_text)
        # Synchronen Code in einem Thread ausführen
        chunks = await asyncio.to_thread(_strategy_by_heading, blocks, config, note_id, doc_title)
        
    else: # sliding_window (Default)
        blocks, doc_title = parse_blocks(md_text)
        # Synchronen Code in einem Thread ausführen
        chunks = await asyncio.to_thread(_strategy_sliding_window, blocks, config, note_id)
        
    # 4. Post-Process: Neighbors setzen
    for i, ch in enumerate(chunks):
        ch.neighbors_prev = chunks[i-1].id if i > 0 else None
        ch.neighbors_next = chunks[i+1].id if i < len(chunks)-1 else None
        
    return chunks