import logging
from pathlib import Path
from functools import lru_cache
from typing import Optional
from pybtex.database import parse_file, BibliographyData
from pybtex.plugin import find_plugin

logger = logging.getLogger(__name__)

BIB_DIR = Path("public/bib")
STYLE_NAME = "apa7"
OUTPUT_FORMAT = "html"

@lru_cache(maxsize=1)
def load_bibliography() -> BibliographyData:

    bib_files = list(BIB_DIR.glob("*.bib"))
    
    if not bib_files:
        logger.warning(f"No .bib files found in {BIB_DIR}")
        return BibliographyData()
    
    merged_bib = parse_file(str(bib_files[0]))
    logger.info(f"Loaded bibliography from {bib_files[0].name}")
    
    for bib_file in bib_files[1:]:
        try:
            bib_data = parse_file(str(bib_file))
            merged_bib.entries.update(bib_data.entries)
            logger.info(f"Merged bibliography from {bib_file.name}")
        except Exception as e:
            logger.error(f"Error parsing {bib_file}: {e}")
    
    logger.info(f"Total entries loaded: {len(merged_bib.entries)}")
    return merged_bib


def format_citation(
    cite_key: str,
    style: str = STYLE_NAME,
    output_format: str = OUTPUT_FORMAT
) -> str:
    
    try:
        bibliography = load_bibliography()
        
        if cite_key not in bibliography.entries:
            logger.warning(f"Citation key '{cite_key}' not found in bibliography")
            return f"<p class='citation-error'>[Citation not found: {cite_key}]</span>"
        
        filtered_bib = BibliographyData({cite_key: bibliography.entries[cite_key]})
        
        style_plugin = find_plugin('pybtex.style.formatting', style)()
        backend = find_plugin('pybtex.backends', output_format)()
        
        formatted = style_plugin.format_bibliography(filtered_bib)
        
        for entry in formatted:
            return entry.text.render(backend)
        
        return f"<p class='citation-error'>[Error formatting: {cite_key}]</span>"
        
    except Exception as e:
        logger.error(f"Error formatting citation {cite_key}: {e}")
        return f"<p class='citation-error'>[Error: {cite_key}]</span>"


def format_bibliography(
    cite_keys: Optional[list[str]] = None,
    style: str = STYLE_NAME,
    output_format: str = OUTPUT_FORMAT
) -> str:

    try:
        bibliography = load_bibliography()
        
        # Filter to requested keys if provided
        if cite_keys:
            filtered_entries = {
                key: bibliography.entries[key]
                for key in cite_keys
                if key in bibliography.entries
            }
            
            if not filtered_entries:
                return "<p class='bibliography-error'>No valid citation keys provided.</p>"
            
            filtered_bib = BibliographyData(filtered_entries)
        else:
            filtered_bib = bibliography
        
        style_plugin = find_plugin('pybtex.style.formatting', style)()
        backend = find_plugin('pybtex.backends', output_format)()
        
        formatted = style_plugin.format_bibliography(filtered_bib)
        
        entries_html = []
        for entry in formatted:
            entries_html.append(entry.text.render(backend))
        
        return "\n".join(entries_html)
        
    except Exception as e:
        logger.error(f"Error formatting bibliography: {e}")
        return f"<p class='bibliography-error'>[Error formatting bibliography]</p>"


def get_bibtex_entry(cite_key: str) -> Optional[str]:
    
    try:
        bibliography = load_bibliography()
        
        if cite_key not in bibliography.entries:
            logger.warning(f"Citation key '{cite_key}' not found")
            return None
        
        single_entry = BibliographyData({cite_key: bibliography.entries[cite_key]})
        
        return single_entry.to_string('bibtex')
        
    except Exception as e:
        logger.error(f"Error getting BibTeX for {cite_key}: {e}")
        return None