app.py

# MetaDiscovery Agent - LOC API with Collection Selector and Search Endpoint + Enhanced Features
import requests
import pandas as pd
import numpy as np
import streamlit as st
import plotly.express as px
from sklearn.feature_extraction.text import TfidfVectorizer
from sklearn.metrics.pairwise import cosine_similarity

# Streamlit app header
st.title("MetaDiscovery Agent for Library of Congress Collections")
st.markdown("""
This tool connects to the LOC API, retrieves metadata from a selected collection, and performs
an analysis of metadata completeness, suggests enhancements, and identifies authority gaps.
""")

# Updated collection URLs using the correct LOC API format
collections = {
    "American Revolutionary War Maps": {"path": "maps", "query": "american+revolutionary+war"},
    "Civil War Maps": {"path": "maps", "query": "civil+war"},
    "Women's Suffrage": {"path": "collection", "query": "women+suffrage"},
    "World War I Posters": {"path": "pictures", "query": "world+war+I+posters"}
}

# Sidebar for selecting collection
st.sidebar.markdown("## Settings")
selected = st.sidebar.selectbox("Select a collection", list(collections.keys()))
collection_info = collections[selected]

# Correct URL format for LOC API
collection_url = f"https://www.loc.gov/{collection_info['path']}/search/?q={collection_info['query']}&fo=json"
st.sidebar.write(f"Selected Collection: {selected}")
st.sidebar.write(f"API URL: {collection_url}")

# Fetch data from LOC API with error handling
try:
    response = requests.get(collection_url)
    response.raise_for_status()  # Raise exception for 4XX/5XX responses
    data = response.json()
    
    # Handle both possible response structures
    if "results" in data:
        records = data.get("results", [])
    elif "items" in data:
        records = data.get("items", [])
    else:
        records = []
        st.error("Unexpected API response structure. No records found.")
        
    st.write(f"Retrieved {len(records)} records")
    
except requests.exceptions.RequestException as e:
    st.error(f"API Connection Error: {e}")
    records = []
except ValueError:
    st.error("Failed to parse API response as JSON")
    records = []

# Extract selected metadata fields with proper path traversal
items = []
for record in records:
    # Handle different possible data structures
    if isinstance(record, dict):
        # For direct field access
        item = {
            "id": record.get("id", ""),
            "title": record.get("title", ""),
            "date": record.get("date", ""),
            "subject": ", ".join(record.get("subject", [])) if isinstance(record.get("subject"), list) else record.get("subject", ""),
            "creator": record.get("creator", ""),
            "description": record.get("description", "")
        }
        
        # For nested field access (common in LOC API)
        if not item["title"] and "item" in record:
            item["title"] = record.get("item", {}).get("title", "")
        if not item["date"] and "item" in record:
            item["date"] = record.get("item", {}).get("date", "")
        
        items.append(item)

# Create DataFrame
metadata_df = pd.DataFrame(items)

if not metadata_df.empty:
    st.subheader("📦 Retrieved Metadata Sample")
    st.dataframe(metadata_df.head())
    
    # Metadata completeness analysis
    st.subheader("🧠 Metadata Completeness Analysis")
    completeness = metadata_df.notnull().mean() * 100
    completeness_df = pd.DataFrame({"Field": completeness.index, "Completeness (%)": completeness.values})
    
    # Plot completeness
    fig = px.bar(completeness_df, x="Field", y="Completeness (%)", title="Metadata Completeness by Field")
    st.plotly_chart(fig)
    
    # List records with missing values
    st.subheader("⚠️ Records with Incomplete Metadata")
    incomplete_records = metadata_df[metadata_df.isnull().any(axis=1)]
    if not incomplete_records.empty:
        st.dataframe(incomplete_records)
    else:
        st.success("All metadata fields are complete in this collection!")
    
    # Show exact items that need updates
    st.subheader("📌 Identifiers of Items Needing Metadata Updates")
    if not incomplete_records.empty:
        st.write(incomplete_records[['id', 'title']])
    else:
        st.success("All records are complete!")
    
    # Suggest metadata using text similarity with better error handling
    st.subheader("✨ Suggested Metadata Enhancements")
    
    # Only process if we have descriptions and enough data
    filled_descriptions = metadata_df[metadata_df['description'].notnull()]['description'].astype(str)
    
    if len(filled_descriptions) > 1:
        try:
            tfidf = TfidfVectorizer(stop_words='english')
            tfidf_matrix = tfidf.fit_transform(filled_descriptions)
            sim_matrix = cosine_similarity(tfidf_matrix)
            
            suggestions = []
            for idx, row in incomplete_records.iterrows():
                if pd.isna(row['subject']) and pd.notna(row['description']):
                    desc_vec = tfidf.transform([str(row['description'])])
                    sims = cosine_similarity(desc_vec, tfidf_matrix).flatten()
                    top_idx = sims.argmax()
                    suggested_subject = metadata_df.iloc[top_idx]['subject']
                    if pd.notna(suggested_subject) and suggested_subject:  # Only add valid suggestions
                        suggestions.append((row['title'], suggested_subject))
            
            if suggestions:
                suggestions_df = pd.DataFrame(suggestions, columns=["Title", "Suggested Subject"])
                st.dataframe(suggestions_df)
            else:
                st.info("No metadata enhancement suggestions available.")
        except Exception as e:
            st.error(f"Error generating metadata suggestions: {e}")
    else:
        st.info("Not enough descriptive data to generate metadata suggestions.")
else:
    st.warning("No metadata records found for this collection. Try selecting another one.")