"""
FILE: app/core/chunking/chunking_strategies.py
DESCRIPTION: Korrigierte Splitting-Strategien für Mindnet v3.3.3.
             - Fix: Erhalt von Überschriften im Chunk-Text.
             - Fix: Atomares Buffering (Blöcke fallen als Ganzes in den nächsten Chunk).
             - Fix: Korrekte Zuordnung von Sektions-Metadaten.
"""
from typing import List, Dict, Any, Optional
from .chunking_models import RawBlock, Chunk
from .chunking_utils import estimate_tokens
from .chunking_parser import split_sentences

def _create_context_win(doc_title: str, sec_title: Optional[str], text: str) -> str:
    """Baut den Breadcrumb-Kontext für das Embedding-Fenster."""
    parts = []
    if doc_title: parts.append(doc_title)
    if sec_title and sec_title != doc_title: parts.append(sec_title)
    prefix = " > ".join(parts)
    return f"{prefix}\n{text}".strip() if prefix else text

def strategy_by_heading(blocks: List[RawBlock], config: Dict[str, Any], note_id: str, doc_title: str = "") -> List[Chunk]:
    """
    Splittet Text basierend auf Markdown-Überschriften mit atomarem Block-Erhalt.
    """
    strict = config.get("strict_heading_split", False)
    target = config.get("target", 400)
    max_tokens = config.get("max", 600)
    split_level = config.get("split_level", 2)
    overlap = sum(config.get("overlap", (50, 80))) // 2
    
    chunks: List[Chunk] = []
    buf: List[RawBlock] = []
    cur_tokens = 0

    def _add_to_chunks(txt, title, path):
        idx = len(chunks)
        win = _create_context_win(doc_title, title, txt)
        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=title, section_path=path,
            neighbors_prev=None, neighbors_next=None
        ))

    def _flush():
        nonlocal buf, cur_tokens
        if not buf: return
        
        # Metadaten stammen immer vom ersten Block im Puffer (meist die Überschrift)
        main_title = buf[0].section_title
        main_path = buf[0].section_path
        full_text = "\n\n".join([b.text for b in buf])
        
        # Falls der gesamte Puffer in einen Chunk passt
        if estimate_tokens(full_text) <= max_tokens:
            _add_to_chunks(full_text, main_title, main_path)
        else:
            # Nur wenn ein einzelner Abschnitt größer als 'max' ist, wird intern gesplittet
            sents = split_sentences(full_text)
            cur_sents = []; sub_len = 0
            for s in sents:
                slen = estimate_tokens(s)
                if sub_len + slen > target and cur_sents:
                    _add_to_chunks(" ".join(cur_sents), main_title, main_path)
                    ov_s = []; ov_l = 0
                    for os in reversed(cur_sents):
                        if ov_l + estimate_tokens(os) < overlap:
                            ov_s.insert(0, os); ov_l += estimate_tokens(os)
                        else: break
                    cur_sents = list(ov_s); cur_sents.append(s); sub_len = ov_l + slen
                else: cur_sents.append(s); sub_len += slen
            if cur_sents: _add_to_chunks(" ".join(cur_sents), main_title, main_path)
        
        buf = []; cur_tokens = 0

    for b in blocks:
        b_tokens = estimate_tokens(b.text)
        
        # Prüfung auf Split-Trigger (Überschriften)
        is_split_trigger = False
        if b.kind == "heading":
            if b.level < split_level:
                is_split_trigger = True
            elif b.level == split_level:
                if strict or cur_tokens >= target:
                    is_split_trigger = True
        
        if is_split_trigger:
            _flush() # Vorherigen Puffer leeren
            buf.append(b) # Neue Überschrift in den neuen Puffer aufnehmen
            cur_tokens = b_tokens
        else:
            # Atomarer Check: Wenn der neue Block den aktuellen Chunk sprengen würde
            if cur_tokens + b_tokens > max_tokens and buf:
                _flush() # Puffer leeren, Block 'b' wird Teil des nächsten Chunks
                
            buf.append(b)
            cur_tokens += b_tokens

    _flush() # Letzten Puffer leeren
    return chunks

def strategy_sliding_window(blocks: List[RawBlock], 
                            config: Dict[str, Any], 
                            note_id: str, 
                            context_prefix: str = "") -> List[Chunk]:
    """
    Standard Sliding Window mit Korrektur für Heading-Retention.
    """
    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_window():
        nonlocal buf
        if not buf: return
        txt = "\n\n".join([b.text for b in buf])
        idx = len(chunks)
        win = f"{context_prefix}\n{txt}".strip() if context_prefix else txt
        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=buf[0].section_title, section_path=buf[0].section_path,
            neighbors_prev=None, neighbors_next=None
        ))
        buf = []

    for b in blocks:
        # Auch hier: Überschriften mitnehmen
        b_tokens = estimate_tokens(b.text)
        current_buf_tokens = estimate_tokens("\n\n".join([x.text for x in buf])) if buf else 0
        
        if current_buf_tokens + b_tokens >= target and buf:
            _flush_window()
        buf.append(b)
        
    _flush_window()
    return chunks