Update app.py

app.py

@@ -383,7 +383,6 @@ div[data-testid="column"] .stButton > button[kind="secondary"] {
 # ── Session state ────────────────────────────────────────────────────
 import datetime as _dt
 
-# ── Session state ────────────────────────────────────────────────
 if "messages" not in st.session_state:
     st.session_state.messages = []
 if "last_submitted" not in st.session_state:
@@ -402,6 +401,13 @@ if "pending_file_name" not in st.session_state:
     st.session_state.pending_file_name = None
 if "pending_file_mime" not in st.session_state:
     st.session_state.pending_file_mime = None
+# ── Attached file kept in memory for follow-up questions ─────────
+if "attached_file_bytes" not in st.session_state:
+    st.session_state.attached_file_bytes = None
+if "attached_file_name" not in st.session_state:
+    st.session_state.attached_file_name = None
+if "attached_file_mime" not in st.session_state:
+    st.session_state.attached_file_mime = None
 
 # ════════════════════════════════════════════════════════════════════
 # SUPABASE — Persistent chat history
@@ -479,6 +485,10 @@ def new_chat():
     st.session_state.current_chat_id = chat_id
     st.session_state.messages = []
     st.session_state.last_submitted = ""
+    # Clear any attached file memory from previous chat
+    st.session_state.attached_file_bytes = None
+    st.session_state.attached_file_name  = None
+    st.session_state.attached_file_mime  = None
 
 def save_current_chat():
     """Save current messages to session state and Supabase."""
@@ -491,7 +501,7 @@ def save_current_chat():
     st.session_state.chats[cid] = {
         "title": title,
         "messages": list(st.session_state.messages),
-        "created": _dt.datetime.now().strftime("%d %b %H:%M")
+        "created": _dt.datetime.now().strftime("%Y-%m-%d %H:%M:%S")  # ISO-sortable
     }
     # Save to Supabase (persistent)
     supa_save_chat(cid, title, list(st.session_state.messages))
@@ -502,6 +512,10 @@ def load_chat(chat_id):
         st.session_state.current_chat_id = chat_id
         st.session_state.messages = list(st.session_state.chats[chat_id]["messages"])
         st.session_state.last_submitted = ""
+        # Clear attached file memory — it belongs to a different chat session
+        st.session_state.attached_file_bytes = None
+        st.session_state.attached_file_name  = None
+        st.session_state.attached_file_mime  = None
 
 
 # ════════════════════════════════════════════════════════════════════
@@ -2246,8 +2260,8 @@ def ask_gemini_vision(image_b64: str, mime_type: str, user_note: str) -> str:
             doc = fitz.open(stream=pdf_bytes, filetype="pdf")
             # Render all pages (up to 4) as one tall PNG
             imgs = []
-            for page_num in range(min(len(doc), 4)):
-                pix = doc[page_num].get_pixmap(matrix=fitz.Matrix(2, 2))
+            for page_num in range(min(len(doc), 6)):
+                pix = doc[page_num].get_pixmap(matrix=fitz.Matrix(3, 3))  # 3x zoom for crisp text
                 imgs.append(pix.tobytes("png"))
             doc.close()
             # Stack page images vertically using PIL if available, else just use first page
@@ -2276,18 +2290,22 @@ def ask_gemini_vision(image_b64: str, mime_type: str, user_note: str) -> str:
 
     prompt = (
         "You are Saad.AI, a BSc Mathematics assistant built by Saad.\n"
-        "The student has uploaded a file containing a math problem.\n\n"
-        "YOUR TASKS:\n"
-        "1. Read and extract the math problem from the file exactly.\n"
-        "2. State what the problem is clearly.\n"
-        "3. Solve it step by step:\n"
-        "   🔍 **Given:** ...\n"
-        "   📌 **Method:** ...\n"
-        "   🧮 **Step 1:** ...\n"
-        "   ✅ **Final Answer:** $$\\boxed{answer}$$\n"
-        "4. ALL math must be in LaTeX — never plain text math.\n"
-        "5. If the file is unclear or not math-related, say so politely.\n\n"
-        f"Student's question: {user_note if user_note else 'Solve this problem completely.'}"
+        "The student has uploaded a file that may contain MULTIPLE math problems.\n\n"
+        "CRITICAL RULES:\n"
+        "- Read the ENTIRE document carefully from top to bottom.\n"
+        "- Extract EVERY question/problem you see — do NOT skip any.\n"
+        "- Do NOT invent or make up questions. ONLY solve what is written in the file.\n"
+        "- If you cannot read part of the text, say so explicitly.\n\n"
+        "FOR EACH PROBLEM FOUND, use this structure:\n"
+        "---\n"
+        "### Question [N]: [restate the exact question from the file]\n"
+        "🔍 **Given:** ...\n"
+        "📌 **Method:** ...\n"
+        "🧮 **Step 1:** ...\n"
+        "✅ **Final Answer:** $$\\boxed{answer}$$\n"
+        "---\n\n"
+        "ALL math must be in LaTeX — never plain text math.\n\n"
+        f"Student's specific instruction: {user_note if user_note else 'Read the full file and solve ALL problems you find.'}"
     )
 
     errors = []
@@ -2569,6 +2587,35 @@ with st.sidebar:
 
     st.divider()
 
+    # ── File Attach — always visible in sidebar ───────────────────
+    st.markdown("**📎 Attach File**")
+    st.caption("Image or PDF with math problems")
+    sidebar_file = st.file_uploader(
+        "sidebar_upload",
+        type=["jpg", "jpeg", "png", "webp", "pdf"],
+        label_visibility="collapsed",
+        help="JPG · PNG · WEBP · PDF — max 5 MB",
+        key="sidebar_uploader"
+    )
+    if sidebar_file:
+        file_key = f"{sidebar_file.size}_{sidebar_file.type}"
+        if file_key != st.session_state.get("last_uploaded_file", ""):
+            st.session_state["last_uploaded_file"] = file_key
+            st.session_state.pending_file_bytes = sidebar_file.read()
+            st.session_state.pending_file_name  = sidebar_file.name
+            st.session_state.pending_file_mime  = sidebar_file.type or "application/octet-stream"
+            st.rerun()
+    if st.session_state.pending_file_bytes is not None:
+        st.success(f"✅ **{st.session_state.pending_file_name}**\nType your question in chat ↓")
+        if st.button("✕ Remove file", use_container_width=True, key="sidebar_remove"):
+            st.session_state.pending_file_bytes = None
+            st.session_state.pending_file_name  = None
+            st.session_state.pending_file_mime  = None
+            st.session_state["last_uploaded_file"] = ""  # allow re-uploading the same file
+            st.rerun()
+
+    st.divider()
+
     # ── Chat History ─────────────────────────────────────────────
     if st.session_state.chats:
         st.markdown("**💬 Chat History**")
@@ -2662,8 +2709,7 @@ with st.sidebar:
 
     st.divider()
     if st.button("🗑️ Clear Chat", use_container_width=True):
-        st.session_state.messages = []
-        st.session_state.last_submitted = ""
+        new_chat()
         st.rerun()
 
 
@@ -2830,47 +2876,68 @@ for i, msg in enumerate(st.session_state.messages):
                 st.code(msg["content"], language=None)
 
 # ════════════════════════════════════════════════════════════════════
-# FILE UPLOAD — True ChatGPT-style: attach file THEN type question
+# FILE ATTACH STATUS — fixed bar just above the chat input
+# (uploader lives in the sidebar — always visible, never scrolls away)
 # ════════════════════════════════════════════════════════════════════
 
-# Toolbar row: paperclip button (left-aligned, compact)
-col_attach, col_spacer = st.columns([1, 8])
-with col_attach:
-    attach_label = "📎 Attach" if not st.session_state.show_uploader else "✕ Close"
-    if st.button(attach_label, key="attach_toggle", help="Upload image or PDF"):
-        st.session_state.show_uploader = not st.session_state.show_uploader
-        st.rerun()
-
-# Compact uploader — only visible when toggled ON
-if st.session_state.show_uploader:
-    uploaded_file = st.file_uploader(
-        "Upload image or PDF of your math problem",
-        type=["jpg", "jpeg", "png", "webp", "pdf"],
-        label_visibility="collapsed",
-        help="JPG · PNG · WEBP · PDF — max 5 MB"
-    )
-    if uploaded_file:
-        file_key = f"{uploaded_file.size}_{uploaded_file.type}"
-        if file_key != st.session_state.get("last_uploaded_file", ""):
-            st.session_state["last_uploaded_file"] = file_key
-            # Store file bytes in session state — wait for user's typed question
-            st.session_state.pending_file_bytes = uploaded_file.read()
-            st.session_state.pending_file_name  = uploaded_file.name
-            st.session_state.pending_file_mime  = uploaded_file.type or "application/octet-stream"
-            st.session_state.show_uploader = False
-            st.rerun()
+# ── Always-visible fixed attach bar above the chat input ─────────
+# Shows three states: no file / file pending / file in memory
+_pending_name   = st.session_state.pending_file_bytes is not None
+_memory_name    = st.session_state.attached_file_name
+
+if _pending_name:
+    _bar_color  = "#1a2e1a"
+    _bar_border = "#22c55e"
+    _bar_text   = f"✅ <strong>{st.session_state.pending_file_name}</strong> ready — type your question below and press Enter"
+elif _memory_name:
+    _bar_color  = "#1a1f2e"
+    _bar_border = "#3b82f6"
+    _bar_text   = f"📎 <strong>{_memory_name}</strong> in memory — ask a follow-up or attach a new file via sidebar"
+else:
+    _bar_color  = "#111"
+    _bar_border = "#374151"
+    _bar_text   = "📎 Attach a file: open the <strong>sidebar ←</strong> to upload an image or PDF"
+
+st.markdown(
+    f"""
+    <div style="
+        position: fixed;
+        bottom: 68px;
+        left: 50%;
+        transform: translateX(-50%);
+        width: 720px;
+        max-width: 88vw;
+        background: {_bar_color};
+        border: 1px solid {_bar_border};
+        border-radius: 10px;
+        padding: 7px 16px;
+        z-index: 9999;
+        font-size: 0.80rem;
+        color: #d1d5db;
+    ">
+        {_bar_text}
+    </div>
+    """,
+    unsafe_allow_html=True
+)
 
-# Show attached file pill above input bar so user knows it's ready
-if st.session_state.pending_file_bytes is not None:
-    col_pill, col_x = st.columns([9, 1])
-    with col_pill:
-        st.info(f"📎 **{st.session_state.pending_file_name}** attached — type your question below and press Enter")
-    with col_x:
-        if st.button("✕", key="remove_pending", help="Remove attached file"):
+# Remove-file buttons (in-page, shown only when file exists)
+if _pending_name:
+    col_sp, col_rm = st.columns([11, 1])
+    with col_rm:
+        if st.button("✕", key="remove_pending", help="Remove pending file"):
             st.session_state.pending_file_bytes = None
             st.session_state.pending_file_name  = None
             st.session_state.pending_file_mime  = None
             st.rerun()
+elif _memory_name:
+    col_sp, col_rm = st.columns([11, 1])
+    with col_rm:
+        if st.button("✕", key="clear_memory_file", help="Remove file from memory"):
+            st.session_state.attached_file_bytes = None
+            st.session_state.attached_file_name  = None
+            st.session_state.attached_file_mime  = None
+            st.rerun()
 
 # ════════════════════════════════════════════════════════════════════
 # INPUT — ChatGPT-style input bar
@@ -2880,7 +2947,7 @@ if st.session_state.pending_file_bytes is not None:
 prefill = examples.get(selected, "") if selected != "-- Select --" else ""
 
 user_input = st.chat_input(
-    placeholder="Type a BSc math problem... e.g. 'Solve d²y/dx² + 4y = cos(2x)'",
+    placeholder="Type a math problem... or attach a file in the sidebar ← then ask here",
 )
 
 # Also allow clicking an example to submit it directly
@@ -2897,7 +2964,7 @@ else:
 if problem and problem != st.session_state.last_submitted:
     st.session_state.last_submitted = problem
 
-    # ── If a file is attached, send file + question to Gemini Vision ─
+    # ── If a NEW file is attached, send file + question to Vision ────
     if st.session_state.pending_file_bytes is not None:
         import base64
 
@@ -2905,16 +2972,52 @@ if problem and problem != st.session_state.last_submitted:
         file_name  = st.session_state.pending_file_name
         file_mime  = st.session_state.pending_file_mime
 
-        # Clear pending file immediately so it's not re-sent on rerun
+        # ── Validate size (5 MB limit) ────────────────────────────────
+        MAX_FILE_SIZE = 5 * 1024 * 1024
+        if len(file_bytes) > MAX_FILE_SIZE:
+            st.session_state.pending_file_bytes = None
+            st.session_state.pending_file_name  = None
+            st.session_state.pending_file_mime  = None
+            st.session_state["last_uploaded_file"] = ""
+            st.error(f"⚠️ File too large ({len(file_bytes)//1024} KB). Please upload under 5 MB.")
+            st.stop()
+
+        # ── Validate MIME type ────────────────────────────────────────
+        _allowed_mimes = {"image/jpeg", "image/png", "image/webp", "application/pdf"}
+        if file_mime not in _allowed_mimes:
+            st.session_state.pending_file_bytes = None
+            st.session_state.pending_file_name  = None
+            st.session_state.pending_file_mime  = None
+            st.session_state["last_uploaded_file"] = ""
+            st.error("⚠️ Unsupported format. Please upload JPG, PNG, WEBP or PDF.")
+            st.stop()
+
+        # Clear pending (one-time) but keep in attached memory for follow-ups
         st.session_state.pending_file_bytes = None
         st.session_state.pending_file_name  = None
         st.session_state.pending_file_mime  = None
+        st.session_state.attached_file_bytes = file_bytes
+        st.session_state.attached_file_name  = file_name
+        st.session_state.attached_file_mime  = file_mime
 
         with st.chat_message("user", avatar="🧑‍🎓"):
             st.markdown(f"📎 **{file_name}** — {problem}")
+            # Show file preview so user can see what was attached
+            if file_mime and file_mime.startswith("image/"):
+                st.image(file_bytes, caption=file_name, use_container_width=True)
+            else:
+                # PDF — try to show first page
+                try:
+                    import fitz, io
+                    doc = fitz.open(stream=file_bytes, filetype="pdf")
+                    pix = doc[0].get_pixmap(matrix=fitz.Matrix(1.5, 1.5))
+                    doc.close()
+                    st.image(pix.tobytes("png"), caption=f"📄 {file_name} (page 1 preview)", use_container_width=True)
+                except Exception:
+                    st.caption(f"📄 {file_name}")
 
         with st.chat_message("assistant", avatar="📐"):
-            with st.spinner("📖 Reading your file with Gemini..."):
+            with st.spinner("📖 Reading your file..."):
                 image_b64 = base64.b64encode(file_bytes).decode("utf-8")
                 answer = ask_gemini_vision(image_b64, file_mime, problem)
             st.markdown(answer)
@@ -2931,6 +3034,37 @@ if problem and problem != st.session_state.last_submitted:
         save_current_chat()
         st.stop()
 
+    # ── Follow-up about previously attached file ──────────────────────
+    # Detects "solve q3", "next question", "question 2" etc. and re-sends the file
+    _p = problem.lower()
+    _followup_triggers = [
+        "question", "solve q", "q1","q2","q3","q4","q5","q6","q7","q8","q9","q10",
+        "next one", "next question", "next qus", "next ques",
+        "previous", "solve the next", "solve all", "solve rest",
+        "number ", "no.", "no ", "#", "part ", "part(", "section",
+    ]
+    _is_file_followup = (
+        st.session_state.attached_file_bytes is not None and
+        any(t in _p for t in _followup_triggers)
+    )
+    if _is_file_followup:
+        import base64 as _b64_fu
+        with st.chat_message("user", avatar="🧑‍🎓"):
+            st.markdown(f"📎 *{st.session_state.attached_file_name}* — {problem}")
+        with st.chat_message("assistant", avatar="📐"):
+            with st.spinner("📖 Re-reading your file..."):
+                _fb64 = _b64_fu.b64encode(st.session_state.attached_file_bytes).decode("utf-8")
+                answer = ask_gemini_vision(_fb64, st.session_state.attached_file_mime, problem)
+            st.markdown(answer)
+            with st.expander("📋 Copy"):
+                st.code(answer, language=None)
+        if not st.session_state.current_chat_id:
+            new_chat()
+        st.session_state.messages.append({"role": "user", "content": f"📎 {st.session_state.attached_file_name} — {problem}"})
+        st.session_state.messages.append({"role": "assistant", "content": answer})
+        save_current_chat()
+        st.stop()
+
     # ── Detect casual / non-math messages ───────────────────────────
     p_lower = problem.lower().strip()
     casual_keywords = [