src/streamlit_app.py

import streamlit as st
try:
    from PyPDF2 import PdfReader
except Exception:
    PdfReader = None

# Optional AI SDKs
try:
    import google.generativeai as genai
except Exception:
    genai = None

try:
    from langchain_google_genai import ChatGoogleGenerativeAI
    from langchain_core.prompts import PromptTemplate
except Exception:
    ChatGoogleGenerativeAI = None
    PromptTemplate = None

from pydantic import BaseModel, Field
from typing import Optional
import os

# --- Pydantic Models (from your code) ---

class questions(BaseModel):
    questions: list[str] = Field(description="List of questions")

class introduction(BaseModel):
    intro: Optional[str] = Field(description="Give AI agent's intro")
    question: str = Field(description="Question asked by AI agent")
    followup: Optional[str] = Field(description="The followup question to user's answer")

class evaluation(BaseModel):
    marks: int = Field(description="Marks out of 100")
    followup: Optional[str] = Field(description="The followup question")
    review: Optional[str] = Field(description="Short Review of the answer")

# --- AI & Logic Functions (from your code) ---

@st.cache_resource
def get_llm(api_key):
    """Cached function to initialize the LLM."""
    return ChatGoogleGenerativeAI(
        model="gemini-2.5-flash",  
        temperature=1.0,
        google_api_key=api_key
    )
    
@st.cache_resource
def get_models(_llm_model):
    """Cached function to get structured output models."""
    generate_questions_resume_model = _llm_model.with_structured_output(questions)
    intro_model = _llm_model.with_structured_output(introduction)
    evaluate_answers_model = _llm_model.with_structured_output(evaluation)
    return generate_questions_resume_model, intro_model, evaluate_answers_model

    
def read_resume(uploaded_file):
    """Reads a PDF file uploaded via Streamlit."""
    try:
        if PdfReader is None:
            st.warning("PyPDF2 is not installed; resume text extraction disabled.")
            return None
        reader = PdfReader(uploaded_file)
        text = ""
        for page in reader.pages:
            text += page.extract_text() or ""
        return text
    except Exception as e:
        st.error(f"Error reading PDF: {e}")
        return None

def generate_questions_from_resume(resume_text, model):
    """Generates interview questions from resume text."""
    if PromptTemplate is None or model is None or not st.session_state.get('enable_llm', False):
        # Simple fallback
        questions = ["Tell me about your most significant project.", "Describe a challenging bug you fixed.", "How do you design for scalability?", "Which technologies are you most comfortable with?"]
        return questions

    parse_resume_prompt_template = PromptTemplate(
        template="""Generate 4-8 interview questions about the Experience and Projects section from this given text of from a resume.
Try to cover all projects and experience. Generate some conceptual questions too. Don't generate unnecessary questions.
Resume:\n{text}""",
        input_variables=['text']
    )
    try:
        if not st.session_state.get('enable_llm', False):
            raise RuntimeError('LLM disabled')
        generate_question_from_resume_chain = parse_resume_prompt_template | model
        output = generate_question_from_resume_chain.invoke({'text': resume_text})
        return getattr(output, 'questions', output)
    except Exception as e:
        st.warning(f"LLM question generation failed or disabled, using fallback: {e}")
        questions = ["Tell me about your most significant project.", "Describe a challenging bug you fixed.", "How do you design for scalability?", "Which technologies are you most comfortable with?"]
        return questions

def get_introduction(model):
    """Gets the AI's intro and first question."""
    if PromptTemplate is None or model is None or not st.session_state.get('enable_llm', False):
        return type('O', (), {'intro': "Hello, I'm Interviewer.AI. Please introduce yourself.", 'question': "Can you briefly introduce yourself?"})()

    introduction_prompt = PromptTemplate(template="""Introduce yourself to the user telling the user that you are a AI agent. And ask the user to give introduction""")
    try:
        if not st.session_state.get('enable_llm', False):
            raise RuntimeError('LLM disabled')
        intro_chain = introduction_prompt | model
        output = intro_chain.invoke({})
        return output
    except Exception as e:
        st.warning(f"LLM intro generation failed or disabled: {e}")
        return type('O', (), {'intro': "Hello, I'm Interviewer.AI. Please introduce yourself.", 'question': "Can you briefly introduce yourself?"})()

def ask_followup(user_intro, model):
    """Asks a followup to the user's intro."""
    if PromptTemplate is None or model is None or not st.session_state.get('enable_llm', False):
        return "Thanks — could you tell me one achievement you're most proud of?"

    intro_followup = PromptTemplate(template="""The user has given the following introduction of himself/herself. Ask a followup about his intro to make the user comfortable. Intro given by the user: {intro}""",
                                    input_variables=['intro'])
    try:
        if not st.session_state.get('enable_llm', False):
            raise RuntimeError('LLM disabled')
        followup_chain = intro_followup | model
        output = followup_chain.invoke({'intro': user_intro})
        return getattr(output, 'followup', None)
    except Exception as e:
        st.warning(f"LLM followup generation failed or disabled: {e}")
        return "Could you tell me about a specific result from that experience?"

def evaluate_answer(question, answer, model):
    """Evaluates the user's answer."""
    if PromptTemplate is None or model is None or not st.session_state.get('enable_llm', False):
        # Simple heuristic evaluator
        score = 50
        review = "Thank you for your answer. Provide more details next time."
        followup = None
        if answer and len(answer.split()) > 50:
            score = 80
            review = "Good answer — you covered several points."
        elif answer and len(answer.split()) > 20:
            score = 65
            review = "Decent answer; add more concrete examples."
        return type('O', (), {'marks': score, 'review': review, 'followup': followup})()

    evaluate_answer_prompt = PromptTemplate(template="""You are given a question and an answer. Evaluate the answer honestly on the question out of 100.
Also generate a very short review on the answer telling the candidate about his answer. If he is wrong but close to the correct answer, give subtle hints.
If a good followup question can be asked generate it but only if it is a genuine question.\nQuestion: {question}\n\n Answer: {answer}""",
                                            input_variables=['question', 'answer'])
    try:
        if not st.session_state.get('enable_llm', False):
            raise RuntimeError('LLM disabled')
        evaluate_chain = evaluate_answer_prompt | model
        output = evaluate_chain.invoke({'question': question, 'answer': answer})
        return output
    except Exception as e:
        st.warning(f"LLM evaluation failed or disabled: {e}")
        score = 50
        review = "Thank you for your answer. Provide more details next time."
        followup = None
        if answer and len(answer.split()) > 50:
            score = 80
        elif answer and len(answer.split()) > 20:
            score = 65
        return type('O', (), {'marks': score, 'review': review, 'followup': followup})()

# --- MODIFIED Streamlit Audio/Visual Function ---

def text_to_speech_and_display(text, autoplay=True):
    """
    MODIFIED: This function no longer plays audio. 
    It just displays the text in the chat history.
    """
    if not text:
        return
        
    try:
        if 'chat_history' not in st.session_state:
            st.session_state.chat_history = []
        st.session_state.chat_history.append(f"**Interviewer:** {text}")
    except Exception as e:
        st.error(f"Error in text_to_speech_and_display: {e}")

# --- DELETED speech_to_text function ---
# We are replacing it with a text_input


# --- Main Streamlit App ---

st.set_page_config(page_title="AI Interviewer", layout="wide")
st.title("Interviewer.AI")

# Initialize LLM and models
llm = None
gen_q_model = None
intro_model = None
eval_model = None

# First, load the key from the environment variable if genai is available
if genai is None or ChatGoogleGenerativeAI is None:
    st.warning("Google GenAI or LangChain wrappers not available. App will use deterministic fallbacks.")

if 'enable_llm' not in st.session_state:
    st.session_state.enable_llm = False

GOOGLE_API_KEY = os.environ.get("GOOGLE_API_KEY")
api_key_exists = bool(GOOGLE_API_KEY)

if not api_key_exists:
    st.warning("⚠️ GOOGLE_API_KEY not found in environment variables.")
    st.info("Add GOOGLE_API_KEY to your Hugging Face Space secrets to enable AI features.")

# LLM Enable Checkbox
enable_llm_checkbox = st.checkbox(
    "Enable LLM features (requires GOOGLE_API_KEY)", 
    value=st.session_state.enable_llm,
    disabled=not api_key_exists,
    help="AI-powered question generation and evaluation"
)
st.session_state.enable_llm = enable_llm_checkbox

# Initialize LLM if enabled
if st.session_state.enable_llm and api_key_exists:
    try:
        genai.configure(api_key=GOOGLE_API_KEY)
        llm = get_llm(GOOGLE_API_KEY)
        gen_q_model, intro_model, eval_model = get_models(llm)
        st.success("✅ LLM features enabled successfully")
    except Exception as e:
        st.error(f"❌ Could not initialize LLM: {e}")
        st.info("Check your API key and try again.")
        st.session_state.enable_llm = False
        llm = None
        gen_q_model = None
        intro_model = None
        eval_model = None

# Test API Button (AFTER initialization)
if st.button("Test Google API Connection"):
    if not st.session_state.enable_llm:
        st.error("❌ LLM features are not enabled. Check the checkbox above first.")
    elif llm is None:
        st.error("❌ LLM is not initialized. Check API key configuration.")
    else:
        try:
            with st.spinner("Testing API connection..."):
                test_response = llm.invoke("Say 'Hello' if you can hear me.")
                st.success("✅ SUCCESS! API is working correctly.")
                st.info(f"Response: {test_response.content if hasattr(test_response, 'content') else str(test_response)}")
        except Exception as e:
            st.error(f"❌ API call FAILED with error: {e}")
            st.info("This usually means: invalid API key, quota exceeded, or network issues.")

st.divider()

# --- Session State Initialization ---
if 'stage' not in st.session_state:
    st.session_state.stage = 'start'
if 'chat_history' not in st.session_state:
    st.session_state.chat_history = []
if 'questions' not in st.session_state:
    st.session_state.questions = []
if 'q_index' not in st.session_state:
    st.session_state.q_index = 0
if 'current_question' not in st.session_state:
    st.session_state.current_question = ""
if 'total_marks' not in st.session_state:
    st.session_state.total_marks = 0
if 'num_questions' not in st.session_state:
    st.session_state.num_questions = 0

# --- App Logic (State Machine) ---

# --- STAGE 0: Start (File Upload) ---
if st.session_state.stage == 'start':
    st.info("Welcome! Please upload your resume (PDF) to begin the interview.")
    uploaded_file = st.file_uploader("Upload your Resume (PDF)", type=["pdf"])
    
    if uploaded_file:
        with st.spinner("Analyzing your resume... This may take a moment."):
            try:
                resume_text = read_resume(uploaded_file)
                if not resume_text:
                    st.error("Could not extract text from the resume. Please try another file.")
                    st.session_state.stage = 'start'
                else:
                    # 1. Generate Questions
                    st.session_state.questions = generate_questions_from_resume(resume_text, gen_q_model)
                    if not st.session_state.questions:
                        st.warning("No AI-generated questions returned; using fallback questions.")
                        st.session_state.questions = generate_questions_from_resume(resume_text, None)

                    # 2. Get AI Introduction
                    intro_output = get_introduction(intro_model)
                    st.session_state.current_question = getattr(intro_output, 'question', "Can you introduce yourself?")

                    # 3. Move to next stage and display intro
                    st.session_state.stage = 'awaiting_intro'
                    
                    # --- MODIFIED: Display text directly ---
                    text_to_speech_and_display(getattr(intro_output, 'intro', "Hello, I'm Interviewer.AI. Please introduce yourself."))
                    text_to_speech_and_display(getattr(intro_output, 'question', "Can you introduce yourself?"))
                    
                    st.rerun()
            except Exception as e:
                st.error(f"An error occurred while processing the resume. Using fallback behaviour. Error: {e}")
                fallback_qs = ["Tell me about your most significant project.", "Describe a challenging bug you fixed.", "How do you design for scalability?", "Which technologies are you most comfortable with?"]
                st.session_state.questions = fallback_qs
                st.session_state.stage = 'asking_question'
                st.rerun()

# --- Main Interview Area (Stages > 0) ---
if st.session_state.stage != 'start':
    
    # --- Chat History Display ---
    st.subheader("Interview Transcript")
    chat_container = st.container(height=400) # Added height for scrolling
    with chat_container:
        for entry in st.session_state.chat_history:
            st.markdown(entry)

    try:
        st.divider()
    except Exception:
        st.markdown('---')

    # --- End Interview Button ---
    if st.button("End Interview", type="primary"):
        st.session_state.stage = 'finished'
        st.rerun()

    # --- REPLACEMENT: Text Input Area ---
    user_text = None # Initialize user_text
    is_disabled = (st.session_state.stage == 'finished')

    with st.form(key="answer_form", clear_on_submit=True):
        answer = st.text_input("Your answer:", disabled=is_disabled)
        submit_button = st.form_submit_button(label="Submit Answer", disabled=is_disabled)
        
        if submit_button and answer:
            user_text = answer
            st.session_state.chat_history.append(f"**You:** {user_text}")
    # --- END OF REPLACEMENT ---


    # --- Process Submitted Text ---
    if user_text:
        # --- STAGE 1: Process User's Introduction ---
        if st.session_state.stage == 'awaiting_intro':
            with st.spinner("Thinking of a followup..."):
                followup = ask_followup(user_text, intro_model)
                st.session_state.current_question = followup
                text_to_speech_and_display(followup) # This now just displays text
                st.session_state.stage = 'awaiting_intro_followup'
                st.rerun()
        
        # --- STAGE 2: Process Followup to Intro ---
        elif st.session_state.stage == 'awaiting_intro_followup':
            text_to_speech_and_display("OK, Great. Let's start the interview with questions from your resume.")
            st.session_state.stage = 'asking_question' # Move to main questions
            st.rerun()

        # --- STAGE 4: Process Answer to a Main Question ---
        elif st.session_state.stage == 'awaiting_answer':
            with st.spinner("Evaluating your answer..."):
                question_asked = st.session_state.current_question
                output = evaluate_answer(question_asked, user_text, eval_model)
                
                st.session_state.total_marks += output.marks
                st.session_state.num_questions += 1
                
                if output.review:
                    text_to_speech_and_display(output.review) # This now just displays text
                
                if output.followup:
                    st.session_state.current_question = output.followup
                    text_to_speech_and_display(output.followup) # This now just displays text
                    st.session_state.stage = 'awaiting_followup_answer'
                else:
                    st.session_state.q_index += 1
                    st.session_state.stage = 'asking_question'
                st.rerun()

        # --- STAGE 5: Process Answer to a Followup Question ---
        elif st.session_state.stage == 'awaiting_followup_answer':
             with st.spinner("Evaluating your answer..."):
                question_asked = st.session_state.current_question
                output = evaluate_answer(question_asked, user_text, eval_model)
                
                st.session_state.total_marks += output.marks
                st.session_state.num_questions += 1
                
                if output.review:
                    text_to_speech_and_display(output.review) # This now just displays text
                
                st.session_state.q_index += 1
                st.session_state.stage = 'asking_question'
                st.rerun()

    # --- STAGE 3: Ask a New Question ---
    # This runs when the page loads into this state, *before* user input
    if st.session_state.stage == 'asking_question':
        if st.session_state.q_index < len(st.session_state.questions):
            question = st.session_state.questions[st.session_state.q_index]
            st.session_state.current_question = question
            text_to_speech_and_display(question) # This now just displays text
            st.session_state.stage = 'awaiting_answer'
        else:
            text_to_speech_and_display("That's all the questions I have. Thank you!")
            st.session_state.stage = 'finished'
            st.rerun()

    # --- STAGE 6: Finished ---
    if st.session_state.stage == 'finished':
        st.balloons()
        st.success("Interview Complete!")
        
        final_score = 0
        if st.session_state.num_questions > 0:
            final_score = st.session_state.total_marks / st.session_state.num_questions
        
        st.subheader("Final Report")
        st.markdown(f"**Total Questions Answered:** {st.session_state.num_questions}")
        st.markdown(f"**Average Score:** {final_score:.2f} / 100")
        
        # Transcript is already shown above, but we can show it again
        st.subheader("Full Transcript")
        for entry in st.session_state.chat_history:
            st.markdown(entry)
            
        if st.button("Start New Interview"):
            for key in st.session_state.keys():
                del st.session_state[key]
            st.rerun()