from fastapi import FastAPI, HTTPException, BackgroundTasks
from pydantic import BaseModel, EmailStr, Field
from typing import Optional, Tuple
from enum import Enum
import os
import base64
import pickle
import pandas as pd
from dotenv import load_dotenv
from langchain_openai import ChatOpenAI
from langchain.schema import HumanMessage, SystemMessage
from email.mime.text import MIMEText
from google.auth.transport.requests import Request
from google.oauth2.credentials import Credentials
from google_auth_oauthlib.flow import InstalledAppFlow
from googleapiclient.discovery import build
from googleapiclient.errors import HttpError
from datetime import datetime
import json

# Load environment variables (not needed on Hugging Face, but harmless)
load_dotenv()

# ------------------------------------------
# Helper: Write GOOGLE_CREDENTIALS_JSON to file if needed
# ------------------------------------------
def ensure_credentials_file():
    credentials_env = os.getenv("GOOGLE_CREDENTIALS_JSON")
    credentials_path = "credentials_SYNAPSE.json"
    if not os.path.exists(credentials_path):
        if not credentials_env:
            raise Exception("GOOGLE_CREDENTIALS_JSON not found in environment variables.")
        try:
            parsed_json = json.loads(credentials_env)
        except json.JSONDecodeError:
            raise Exception("Invalid JSON in GOOGLE_CREDENTIALS_JSON")
        with open(credentials_path, "w") as f:
            json.dump(parsed_json, f, indent=2)
    return credentials_path

# ------------------------------------------
# FastAPI app
# ------------------------------------------
app = FastAPI(title="Recruitment Message Generator API", version="1.0.0")

SCOPES = ["https://www.googleapis.com/auth/gmail.send"]
openai_api_key = os.getenv("OPENAI_API_KEY")

# ------------------------------------------
# Enums and Models
# ------------------------------------------
class MessageType(str, Enum):
    OUTREACH = "outreach"
    INTRODUCTORY = "introductory"
    FOLLOWUP = "followup"

class GenerateMessageRequest(BaseModel):
    job_evaluation: str
    sender_email: EmailStr
    recruiter_email: Optional[EmailStr] = None
    recipient_email: EmailStr
    candidate_name: str
    current_role: str
    current_company: str
    company_name: str
    role: str
    recruiter_name: str
    organisation: str
    message_type: MessageType
    send_email: bool = False

class FeedbackRequest(BaseModel):
    message: str
    feedback: str

class AuthenticateRequest(BaseModel):
    email: EmailStr

class AuthenticateResponse(BaseModel):
    success: bool
    message: str
    error: Optional[str] = None

class MessageResponse(BaseModel):
    success: bool
    message: str
    email_sent: bool = False
    email_subject: Optional[str] = None
    error: Optional[str] = None

# ------------------------------------------
# Gmail Helper Functions
# ------------------------------------------
def get_token_file_path(email: str) -> str:
    tokens_dir = "gmail_tokens"
    if not os.path.exists(tokens_dir):
        os.makedirs(tokens_dir)
    safe_email = email.replace("@", "_at_").replace(".", "_dot_")
    return os.path.join(tokens_dir, f"token_{safe_email}.pickle")

def check_user_token_exists(email: str) -> bool:
    token_file = get_token_file_path(email)
    return os.path.exists(token_file)

def load_user_credentials(email: str):
    token_file = get_token_file_path(email)
    if os.path.exists(token_file):
        try:
            with open(token_file, 'rb') as token:
                creds = pickle.load(token)
                return creds
        except Exception:
            if os.path.exists(token_file):
                os.remove(token_file)
    return None

def save_user_credentials(email: str, creds):
    token_file = get_token_file_path(email)
    with open(token_file, 'wb') as token:
        pickle.dump(creds, token)

def create_new_credentials(email: str):
    credentials_path = ensure_credentials_file()
    flow = InstalledAppFlow.from_client_secrets_file(
        credentials_path, SCOPES
    )
    creds = flow.run_local_server(port=0)
    save_user_credentials(email, creds)
    return creds

def authenticate_gmail(email: str, create_if_missing: bool = False):
    creds = load_user_credentials(email)
    if creds:
        if creds.expired and creds.refresh_token:
            try:
                creds.refresh(Request())
                save_user_credentials(email, creds)
            except Exception:
                if create_if_missing:
                    try:
                        creds = create_new_credentials(email)
                    except:
                        return None
                else:
                    return None
        elif not creds.valid:
            creds = None
    if not creds:
        if create_if_missing:
            try:
                creds = create_new_credentials(email)
            except:
                return None
        else:
            return None
    try:
        service = build("gmail", "v1", credentials=creds)
        return service
    except Exception:
        return None

def create_email_message(sender: str, to: str, subject: str, message_text: str, reply_to: Optional[str] = None):
    message = MIMEText(message_text)
    message["to"] = to
    message["from"] = sender
    message["subject"] = subject
    if reply_to:
        message["reply-to"] = reply_to
    raw_message = base64.urlsafe_b64encode(message.as_bytes()).decode()
    return {"raw": raw_message}

def send_gmail_message(service, user_id: str, message: dict):
    try:
        result = service.users().messages().send(userId=user_id, body=message).execute()
        return result is not None
    except HttpError:
        return False

# ------------------------------------------
# LLM (OpenAI) Message Generation Helpers
# ------------------------------------------
def refine_message_with_feedback(
    original_message: str,
    feedback: str,
) -> Tuple[str, str]:
    api_key = os.getenv("OPENAI_API_KEY")
    llm = ChatOpenAI(
        model="gpt-4o-mini",
        temperature=0.7,
        max_tokens=600,
        openai_api_key=api_key
    )
    prompt = f"""
    Please refine the following recruitment message based on the provided feedback:

    ORIGINAL MESSAGE:
    {original_message}

    FEEDBACK:
    {feedback}

    Please provide your response in the following format:
    SUBJECT: [Your subject line here]

    BODY:
    [Your refined email body content here]
    Keep the same tone and intent as the original message, but incorporate the feedback to improve it.
    """
    try:
        messages = [
            SystemMessage(content="You are a professional recruitment message writer. Refine the given message based on feedback while maintaining professionalism and the original intent."),
            HumanMessage(content=prompt)
        ]
        response = llm.invoke(messages)
        content = response.content.strip()
        subject_line = ""
        body_content = ""
        lines = content.split('\n')
        body_found = False
        body_lines = []
        for line in lines:
            if line.strip().startswith('SUBJECT:'):
                subject_line = line.replace('SUBJECT:', '').strip()
            elif line.strip().startswith('BODY:'):
                body_found = True
            elif body_found and line.strip():
                body_lines.append(line)
        body_content = '\n'.join(body_lines).strip()
        if not subject_line:
            subject_line = "Recruitment Opportunity - Updated"
        if not body_content:
            body_content = content
        return subject_line, body_content
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"Error refining message: {str(e)}")

def generate_recruitment_message_with_subject(
    msg_type: str,
    company: str,
    role_title: str,
    recruiter: str,
    org: str,
    candidate: str,
    current_pos: str,
    evaluation: str,
    feedback: Optional[str] = None
) -> Tuple[str, str]:
    api_key = os.getenv("OPENAI_API_KEY")
    llm = ChatOpenAI(
        model="gpt-4o-mini",
        temperature=0.7,
        max_tokens=600,
        openai_api_key=api_key
    )
    base_prompt = f"""
    Generate a professional recruitment {msg_type} with the following details:
    - Company hiring: {company}
    - Role: {role_title}
    - Recruiter: {recruiter} from {org}
    - Candidate: {candidate}
    - Candidate's current position: {current_pos}
    - Evaluation: {evaluation}
    """
    if msg_type == "outreach":
        prompt = base_prompt + """
        Create an initial outreach message that:
        - Introduces the recruiter and organization
        - Mentions the specific role and company
        - Expresses interest in discussing the opportunity
        - Keeps it short and to the point.
        """
    elif msg_type == "introductory":
        prompt = base_prompt + """
        Create an introductory message that:
        - Thanks the candidate for their initial response
        - Provides more details about the role and company
        - Explains why this opportunity aligns with their background
        - Suggests next steps (like a call or meeting)
        - Maintains a warm, professional tone
        """
    else:  # followup
        prompt = base_prompt + """
        Create a follow-up message that:
        - References previous communication
        - Reiterates interest in the candidate
        - Addresses any potential concerns
        - Provides additional compelling reasons to consider the role
        - Includes a clear call to action
        """
    if feedback:
        prompt += f"\n\nPlease modify the message based on this feedback: {feedback}"
    prompt += """

    Please provide your response in the following format:
    SUBJECT: [Your subject line here]

    BODY:
    [Your email body content here]
    """
    try:
        messages = [
            SystemMessage(content="You are a professional recruitment message writer. Generate both an email subject line and body content. Follow the exact format requested."),
            HumanMessage(content=prompt)
        ]
        response = llm.invoke(messages)
        content = response.content.strip()
        subject_line = ""
        body_content = ""
        lines = content.split('\n')
        body_found = False
        body_lines = []
        for line in lines:
            if line.strip().startswith('SUBJECT:'):
                subject_line = line.replace('SUBJECT:', '').strip()
            elif line.strip().startswith('BODY:'):
                body_found = True
            elif body_found and line.strip():
                body_lines.append(line)
        body_content = '\n'.join(body_lines).strip()
        if not subject_line:
            subject_line = f"Opportunity at {company} - {role_title}"
        if not body_content:
            body_content = content
        return subject_line, body_content
    except Exception as e:
        raise HTTPException(status_code=500, detail=f"Error generating message: {str(e)}")

# ------------------------------------------
# FastAPI Endpoints
# ------------------------------------------
@app.get("/")
async def root():
    return {
        "message": "Recruitment Message Generator API",
        "version": "1.0.0",
        "endpoints": [
            "/generate-message",
            "/refine-message",
            "/authenticate",
            "/docs"
        ]
    }

@app.post("/generate-message", response_model=MessageResponse)
async def generate_message(request: GenerateMessageRequest, background_tasks: BackgroundTasks):
    try:
        current_position = f"{request.current_role} at {request.current_company}"
        email_subject, generated_message = generate_recruitment_message_with_subject(
            msg_type=request.message_type.value.replace('followup', 'follow-up'),
            company=request.company_name,
            role_title=request.role,
            recruiter=request.recruiter_name,
            org=request.organisation,
            candidate=request.candidate_name,
            current_pos=current_position,
            evaluation=request.job_evaluation
        )
        email_sent = False
        if request.send_email:
            registered_users = []
            if os.path.exists("registered_users.csv"):
                df = pd.read_csv("registered_users.csv")
                registered_users = df['email'].tolist() if 'email' in df.columns else []
            if request.sender_email.lower() not in [user.lower() for user in registered_users]:
                return MessageResponse(
                    success=True,
                    message=generated_message,
                    email_sent=False,
                    email_subject=email_subject,
                    error="Email not sent: Sender email is not registered"
                )
            service = authenticate_gmail(request.sender_email)
            if service:
                email_message = create_email_message(
                    sender=request.sender_email,
                    to=request.recipient_email,
                    subject=email_subject,
                    message_text=generated_message,
                    reply_to=request.recruiter_email
                )
                email_sent = send_gmail_message(service, "me", email_message)
                if not email_sent:
                    return MessageResponse(
                        success=True,
                        message=generated_message,
                        email_sent=False,
                        email_subject=email_subject,
                        error="Email not sent: Failed to send via Gmail API"
                    )
            else:
                return MessageResponse(
                    success=True,
                    message=generated_message,
                    email_sent=False,
                    email_subject=email_subject,
                    error="Email not sent: Gmail authentication failed"
                )
        return MessageResponse(
            success=True,
            message=generated_message,
            email_sent=email_sent,
            email_subject=email_subject
        )
    except Exception as e:
        return MessageResponse(
            success=False,
            message="",
            error=str(e)
        )

@app.post("/refine-message", response_model=MessageResponse)
async def refine_message(request: FeedbackRequest):
    try:
        email_subject, refined_message = refine_message_with_feedback(
            original_message=request.message,
            feedback=request.feedback
        )
        return MessageResponse(
            success=True,
            message=refined_message,
            email_sent=False,
            email_subject=email_subject
        )
    except Exception as e:
        return MessageResponse(
            success=False,
            message="",
            error=str(e)
        )

@app.post("/authenticate", response_model=AuthenticateResponse)
async def authenticate_user(request: AuthenticateRequest):
    try:
        if check_user_token_exists(request.email):
            service = authenticate_gmail(request.email, create_if_missing=False)
            if service:
                return AuthenticateResponse(
                    success=True,
                    message="User already authenticated and token is valid"
                )
            else:
                service = authenticate_gmail(request.email, create_if_missing=True)
                if service:
                    return AuthenticateResponse(
                        success=True,
                        message="Token refreshed successfully"
                    )
                else:
                    return AuthenticateResponse(
                        success=False,
                        message="Failed to refresh token",
                        error="Could not refresh existing token. Please check credentials.json"
                    )
        else:
            try:
                creds = create_new_credentials(request.email)
                if creds:
                    return AuthenticateResponse(
                        success=True,
                        message="Authentication successful. Token created and saved."
                    )
                else:
                    return AuthenticateResponse(
                        success=False,
                        message="Authentication failed",
                        error="Failed to create credentials"
                    )
            except Exception as e:
                return AuthenticateResponse(
                    success=False,
                    message="Authentication failed",
                    error=str(e)
                )
    except Exception as e:
        return AuthenticateResponse(
            success=False,
            message="Authentication error",
            error=str(e)
        )

@app.get("/health")
async def health_check():
    return {"status": "healthy", "timestamp": datetime.utcnow().isoformat()}

if __name__ == "__main__":
    import uvicorn
    uvicorn.run(app, host="0.0.0.0", port=8000)