import os
import json
import csv
from typing import Dict, Any

# Safe imports for optional file libraries
try:
    import pypdf
    PYPDF_AVAILABLE = True
except ImportError:
    PYPDF_AVAILABLE = False

try:
    import docx
    DOCX_AVAILABLE = True
except ImportError:
    DOCX_AVAILABLE = False

def extract_text_from_file(file_path: str) -> str:
    """
    Reads the file path and returns extracted text content based on file extension.
    """
    if not os.path.exists(file_path):
        raise FileNotFoundError(f"File not found at: {file_path}")
        
    _, ext = os.path.splitext(file_path.lower())
    
    if ext == ".txt" or ext == ".md":
        with open(file_path, "r", encoding="utf-8", errors="ignore") as f:
            return f.read()
            
    elif ext == ".csv":
        extracted = []
        with open(file_path, "r", encoding="utf-8", errors="ignore") as f:
            reader = csv.reader(f)
            for row in reader:
                extracted.append(", ".join(row))
        return "\n".join(extracted)
        
    elif ext in [".json", ".jsonl"]:
        with open(file_path, "r", encoding="utf-8", errors="ignore") as f:
            try:
                if ext == ".json":
                    data = json.load(f)
                    return json.dumps(data, indent=2)
                else:  # jsonl
                    lines = []
                    for line in f:
                        if line.strip():
                            lines.append(json.dumps(json.loads(line)))
                    return "\n".join(lines)
            except Exception as e:
                raise ValueError(f"Invalid JSON/JSONL format: {str(e)}")
                
    elif ext == ".pdf":
        if not PYPDF_AVAILABLE:
            raise ImportError("PDF extraction requires the 'pypdf' package. Please install it.")
        
        text_content = []
        with open(file_path, "rb") as f:
            reader = pypdf.PdfReader(f)
            num_pages = len(reader.pages)
            
            for i in range(num_pages):
                page_text = reader.pages[i].extract_text()
                if page_text:
                    text_content.append(page_text)
                    
        full_text = "\n".join(text_content).strip()
        if not full_text:
            raise ValueError("PDF text extraction returned empty text. This file appears to be image-only (scanned). OCR is not supported.")
        return full_text
        
    elif ext == ".docx":
        if not DOCX_AVAILABLE:
            raise ImportError("Word document extraction requires the 'python-docx' package. Please install it.")
            
        doc = docx.Document(file_path)
        paragraphs = [p.text for p in doc.paragraphs if p.text.strip()]
        full_text = "\n".join(paragraphs).strip()
        if not full_text:
            raise ValueError("Word document is empty or has no readable text paragraphs.")
        return full_text
        
    else:
        raise ValueError(f"Unsupported file format extension: {ext}")