import hashlib
import os
import sqlite3

from langchain_community.document_loaders import PyPDFLoader

class DuplicateDetector:
    def __init__(self, db_path ="persiststorage.db", max_pages = 10):
        self.fingerprints_seen = set()
        self.db_path = db_path
        self.max_pages =max_pages  
        self._init_db()  
        
    def _init_db(self):
        conn =sqlite3.connect(self.db_path)
        cursor =conn.cursor()
        cursor.execute('''
                        CREATE TABLE IF NOT EXISTS documents (
                            id INTEGER PRIMARY KEY AUTOINCREMENT,
                            filename TEXT,
                            fingerprint TEXT UNIQUE,
                            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
                        )
                       ''')
        conn.commit()
        conn.close()
        

    def is_duplicate (self, pdf_path):
        fingerprints = self.generate_fingerprints(pdf_path)
        try :
            conn = sqlite3.connect(self.db_path)
            cursor = conn.cursor()
            cursor.execute("select id from documents where fingerprint =?", (fingerprints,))
            exists = cursor.fetchone() is not None
            conn.close()
            return exists
        except ValueError as e:
            raise e
            
    def store_fingerprints(self, pdf_path):
        fingerprints = self.generate_fingerprints(pdf_path)
        conn = sqlite3.connect(self.db_path)
        cursor = conn.cursor()
        try :
            cursor.execute("INSERT INTO DOCUMENTS(filename, fingerprint) values(?,?)",
                           (os.path.basename(pdf_path), fingerprints))
            conn.commit()
        except ValueError as e:
            pass
        finally:
            conn.close()

    def generate_fingerprints(self, pdf_path):
        try :
            loader = PyPDFLoader(pdf_path)
            docs = loader.load()
            text = "".join(doc.page_content for doc in docs[:self.max_pages])
            fingerprint = hashlib.sha256(text.encode("utf-8")).hexdigest()
            return fingerprint
        except ValueError as e:
            raise ValueError(f"Failed to fingerprint PDF: {e}")