"""
PDF document parser implementation.
[AC-AISVC-33] PDF parsing using PyMuPDF (fitz).

Extracts text content from PDF files.
"""

import logging
from pathlib import Path
from typing import Any

from app.services.document.base import (
    DocumentParseException,
    DocumentParser,
    ParseResult,
)

logger = logging.getLogger(__name__)


class PDFParser(DocumentParser):
    """
    Parser for PDF documents.
    [AC-AISVC-33] Uses PyMuPDF for text extraction.
    """

    def __init__(self, extract_images: bool = False, **kwargs: Any):
        self._extract_images = extract_images
        self._extra_config = kwargs
        self._fitz = None

    def _get_fitz(self):
        """Lazy import of PyMuPDF."""
        if self._fitz is None:
            try:
                import fitz
                self._fitz = fitz
            except ImportError:
                raise DocumentParseException(
                    "PyMuPDF (fitz) not installed. Install with: pip install pymupdf",
                    parser="pdf"
                )
        return self._fitz

    def parse(self, file_path: str | Path) -> ParseResult:
        """
        Parse a PDF document and extract text content.
        [AC-AISVC-33] Extracts text from all pages.
        """
        path = Path(file_path)
        
        if not path.exists():
            raise DocumentParseException(
                f"File not found: {path}",
                file_path=str(path),
                parser="pdf"
            )
        
        if not self.supports_extension(path.suffix):
            raise DocumentParseException(
                f"Unsupported file extension: {path.suffix}",
                file_path=str(path),
                parser="pdf"
            )
        
        fitz = self._get_fitz()
        
        try:
            doc = fitz.open(path)
            
            text_parts = []
            page_count = len(doc)
            
            for page_num in range(page_count):
                page = doc[page_num]
                text = page.get_text()
                if text.strip():
                    text_parts.append(f"[Page {page_num + 1}]\n{text}")
            
            doc.close()
            
            full_text = "\n\n".join(text_parts)
            file_size = path.stat().st_size
            
            logger.info(
                f"Parsed PDF: {path.name}, pages={page_count}, "
                f"chars={len(full_text)}, size={file_size}"
            )
            
            return ParseResult(
                text=full_text,
                source_path=str(path),
                file_size=file_size,
                page_count=page_count,
                metadata={
                    "format": "pdf",
                    "page_count": page_count,
                }
            )
            
        except DocumentParseException:
            raise
        except Exception as e:
            raise DocumentParseException(
                f"Failed to parse PDF: {e}",
                file_path=str(path),
                parser="pdf",
                details={"error": str(e)}
            )

    def get_supported_extensions(self) -> list[str]:
        """Get supported file extensions."""
        return [".pdf"]


class PDFPlumberParser(DocumentParser):
    """
    Alternative PDF parser using pdfplumber.
    [AC-AISVC-33] Uses pdfplumber for text extraction.
    
    pdfplumber is better for table extraction but slower than PyMuPDF.
    """

    def __init__(self, extract_tables: bool = True, **kwargs: Any):
        self._extract_tables = extract_tables
        self._extra_config = kwargs
        self._pdfplumber = None

    def _get_pdfplumber(self):
        """Lazy import of pdfplumber."""
        if self._pdfplumber is None:
            try:
                import pdfplumber
                self._pdfplumber = pdfplumber
            except ImportError:
                raise DocumentParseException(
                    "pdfplumber not installed. Install with: pip install pdfplumber",
                    parser="pdfplumber"
                )
        return self._pdfplumber

    def parse(self, file_path: str | Path) -> ParseResult:
        """
        Parse a PDF document and extract text content.
        [AC-AISVC-33] Extracts text and optionally tables.
        """
        path = Path(file_path)
        
        if not path.exists():
            raise DocumentParseException(
                f"File not found: {path}",
                file_path=str(path),
                parser="pdfplumber"
            )
        
        pdfplumber = self._get_pdfplumber()
        
        try:
            text_parts = []
            page_count = 0
            
            with pdfplumber.open(path) as pdf:
                page_count = len(pdf.pages)
                
                for page_num, page in enumerate(pdf.pages):
                    text = page.extract_text() or ""
                    
                    if self._extract_tables:
                        tables = page.extract_tables()
                        for table in tables:
                            table_text = self._format_table(table)
                            text += f"\n\n{table_text}"
                    
                    if text.strip():
                        text_parts.append(f"[Page {page_num + 1}]\n{text}")
            
            full_text = "\n\n".join(text_parts)
            file_size = path.stat().st_size
            
            logger.info(
                f"Parsed PDF (pdfplumber): {path.name}, pages={page_count}, "
                f"chars={len(full_text)}, size={file_size}"
            )
            
            return ParseResult(
                text=full_text,
                source_path=str(path),
                file_size=file_size,
                page_count=page_count,
                metadata={
                    "format": "pdf",
                    "parser": "pdfplumber",
                    "page_count": page_count,
                }
            )
            
        except DocumentParseException:
            raise
        except Exception as e:
            raise DocumentParseException(
                f"Failed to parse PDF: {e}",
                file_path=str(path),
                parser="pdfplumber",
                details={"error": str(e)}
            )

    def _format_table(self, table: list[list[str | None]]) -> str:
        """Format a table as text."""
        if not table:
            return ""
        
        lines = []
        for row in table:
            cells = [str(cell) if cell else "" for cell in row]
            lines.append(" | ".join(cells))
        
        return "\n".join(lines)

    def get_supported_extensions(self) -> list[str]:
        """Get supported file extensions."""
        return [".pdf"]