from fastapi import FastAPI, HTTPException, BackgroundTasks, Depends, Header, status
from fastapi.middleware.cors import CORSMiddleware
from fastapi.security import APIKeyHeader
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()

# ------------------------------------------
# Security Configuration
# ------------------------------------------
API_PASSWORD = os.getenv("API_PASSWORD", "Synapse@2025")  # Can be overridden by env var
api_key_header = APIKeyHeader(name="X-API-Key", auto_error=False)

def verify_api_key(api_key: Optional[str] = Depends(api_key_header)) -> str:
    """
    Verify the API key/password provided in the request header.
    """
    if api_key is None:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="API Key required. Please provide X-API-Key header.",
            headers={"WWW-Authenticate": "ApiKey"},
        )
    
    if api_key != API_PASSWORD:
        raise HTTPException(
            status_code=status.HTTP_401_UNAUTHORIZED,
            detail="Invalid API Key",
            headers={"WWW-Authenticate": "ApiKey"},
        )
    
    return api_key

# ------------------------------------------
# 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")
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

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: Optional[str] = Field(None, description="(Optional) Recruiter's evaluation of candidate for the job")
    sender_email: EmailStr
    reply_to_email: Optional[EmailStr] = Field(None, description="Recruiter's email for reply-to header")
    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
    past_conversation: Optional[str] = Field(None, description="(Optional) Previous messages with candidate")

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

class SendMessageRequest(BaseModel):
    subject: str
    email_body: str
    sender_email: EmailStr
    recipient_email: EmailStr
    reply_to_email: Optional[EmailStr] = 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

from email.mime.text import MIMEText

def create_email_message(sender: str, to: str, subject: str, message_text: str, reply_to: Optional[str] = None, is_html: bool = False):
    if is_html:
        message = MIMEText(message_text, "html")
    else:
        message = MIMEText(message_text, "plain")
    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: Optional[str] = None,
    feedback: Optional[str] = None,
    past_conversation: 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
    )
    # Outreach: Only request consent
    if msg_type == "outreach":
        prompt = f"""
        Generate a professional initial outreach message to a candidate.
        - Introduce yourself as {recruiter} from {org}
        - Clearly state you are reaching out about an open role ({role_title}) at {company}
        - Ask if they are open to learning more or interested in a quick chat.
        - Do NOT discuss any job evaluation or judgment.
        - Explicitly request their consent to share more details. E.g., 'Would you be open to hearing more about this opportunity?'
        - Keep it short and friendly.
        - No placeholders like [Candidate Name] or [Role Title] in the output.
        """
    else:
        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}
        """
        if evaluation:
            base_prompt += f"- Evaluation: {evaluation}\n"
        prompt = base_prompt
        if msg_type == "introductory":
            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
            - if in the Evaluation the verdict is rejected, Send a rejection message instead.
            """
        else:  # followup
            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
            """

    # Use feedback if provided
    if feedback:
        prompt += f"\n\nPlease modify the message based on this feedback: {feedback}"

    # Use past conversation if provided
    if past_conversation:
        prompt += f"""
        Use the following past conversation as context to inform your reply:

        PAST CONVERSATION:
        {past_conversation}

        Write a reply message to the candidate, maintaining professionalism and continuity.
        """

    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)}")


def format_email_html(body: str, sender_name: Optional[str]=None, sender_org: Optional[str]=None):
    """Wrap plain text body in an HTML template for better appearance."""
    # Convert consecutive line breaks into HTML paragraphs
    import re
    # Smart paragraphing
    body = re.sub(r"\n\s*\n", "</p><p>", body.strip())  # Double newlines => new paragraph
    body = re.sub(r"\n", "<br>", body)                  # Single newlines => <br>
    # Optional signature
    signature = ""
    if sender_name or sender_org:
        signature = "<br><br>Best regards,<br>"
        if sender_name:
            signature += f"{sender_name}<br>"
        if sender_org:
            signature += f"{sender_org}"
    html = f"""
    <html>
      <body style="font-family: Arial, sans-serif; color: #222; line-height: 1.7; max-width: 540px;">
        <p>{body}</p>
        {signature}
      </body>
    </html>
    """
    return html


# ------------------------------------------
# FastAPI Endpoints
# ------------------------------------------
@app.get("/")
async def root():
    """Root endpoint - public access"""
    return {
        "message": "Recruitment Message Generator API",
        "version": "1.0.0",
        "authentication": "Required for all endpoints except / and /health",
        "auth_header": "X-API-Key",
        "endpoints": [
            "/generate-message",
            "/refine-message",
            "/authenticate",
            "/send-message",
            "/docs"
        ]
    }

@app.post("/send-message", response_model=MessageResponse, dependencies=[Depends(verify_api_key)])
async def send_message(request: SendMessageRequest):
    try:
        # Authenticate sender
        service = authenticate_gmail(request.sender_email)
        if not service:
            return MessageResponse(
                success=False,
                message="",
                error="Gmail authentication failed"
            )
        

        formatted_html = format_email_html(
            request.email_body
        )
        # Create the email
        email_message = create_email_message(
            sender=request.sender_email,
            to=request.recipient_email,
            subject=request.subject,
            message_text=formatted_html,
            reply_to=request.reply_to_email,
            is_html=True
        )
        # Send the email
        email_sent = send_gmail_message(service, "me", email_message)
        if email_sent:
            return MessageResponse(
                success=True,
                message="Email sent successfully.",
                email_sent=True,
                email_subject=request.subject
            )
        else:
            return MessageResponse(
                success=False,
                message="",
                email_sent=False,
                email_subject=request.subject,
                error="Failed to send via Gmail API"
            )
    except Exception as e:
        return MessageResponse(
            success=False,
            message="",
            error=str(e)
        )

@app.post("/generate-message", response_model=MessageResponse, dependencies=[Depends(verify_api_key)])
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,
            past_conversation=request.past_conversation
        )
        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:
                formatted_html = format_email_html(
                    generated_message,
                    sender_name=request.recruiter_name,
                    sender_org=request.organisation
                )
                email_message = create_email_message(
                    sender=request.sender_email,
                    to=request.recipient_email,
                    subject=email_subject,
                    message_text=formatted_html,
                    reply_to=request.reply_to_email,
                    is_html=True
                )
                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, dependencies=[Depends(verify_api_key)])
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, dependencies=[Depends(verify_api_key)])
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():
    """Health check endpoint - public access"""
    return {"status": "healthy", "timestamp": datetime.utcnow().isoformat()}

# Protected documentation endpoint
@app.get("/docs", dependencies=[Depends(verify_api_key)])
async def get_documentation():
    """This will be handled by FastAPI's built-in docs"""
    pass

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