import streamlit as st
from datetime import datetime, date

# --------- Page Setup ---------
st.set_page_config(page_title="To-Do List Manager", page_icon="✅", layout="centered")

# --------- Initialize Session State ---------
if "tasks" not in st.session_state:
    st.session_state.tasks = []

if "edit_mode" not in st.session_state or len(st.session_state.edit_mode) != len(st.session_state.tasks):
    st.session_state.edit_mode = [False] * len(st.session_state.tasks)

# --------- Title ---------
st.markdown("<h1 style='text-align:center;'>✅ To-Do List Manager</h1>", unsafe_allow_html=True)

# --------- Add Task ---------
with st.expander("➕ Add New Task", expanded=True):
    with st.form("add_task_form", clear_on_submit=True):
        col1, col2 = st.columns([3, 2])
        task = col1.text_input("Task")
        due = col2.date_input("Due Date", value=date.today())

        col3, col4 = st.columns([2, 2])
        priority = col3.selectbox("Priority", ["Low", "Medium", "High"])
        category = col4.text_input("Category", placeholder="Work, Study, Personal...")

        submit = st.form_submit_button("Add Task")
        if submit and task.strip():
            st.session_state.tasks.append({
                "task": task.strip(),
                "due": due.strftime("%b %d, %Y"),
                "priority": priority,
                "category": category.strip(),
                "completed": False,
                "created": datetime.now().strftime("%b %d, %Y")
            })
            st.session_state.edit_mode.append(False)

st.divider()

# --------- Filter Section ---------
st.markdown("### 🔍 Filter Tasks")
categories = list({t["category"] for t in st.session_state.tasks if t["category"]}) or ["None"]

col1, col2 = st.columns(2)
priority_filter = col1.selectbox("Filter by Priority", ["All", "High", "Medium", "Low"])
category_filter = col2.selectbox("Filter by Category", ["All"] + categories)

def task_matches_filters(task):
    pri_match = (priority_filter == "All") or (task["priority"] == priority_filter)
    cat_match = (category_filter == "All") or (task["category"] == category_filter)
    return pri_match and cat_match

filtered_tasks = [t for t in st.session_state.tasks if task_matches_filters(t)]
filtered_tasks_sorted = sorted(filtered_tasks, key=lambda x: not x["completed"])  # Completed first

# --------- Task Display ---------
st.markdown("### 📋 Your Tasks")
if not filtered_tasks_sorted:
    st.info("No tasks match the selected filters.")
else:
    for i, task in enumerate(filtered_tasks_sorted):
        task_index = st.session_state.tasks.index(task)

        with st.container():
            st.markdown("---")
            cols = st.columns([0.08, 0.6, 0.1, 0.1, 0.1])

            # ✅ Checkbox
            cols[0].checkbox("", value=task["completed"], key=f"complete_{task_index}",
                             on_change=lambda idx=task_index: st.session_state.tasks.__setitem__(idx, {
                                 **st.session_state.tasks[idx],
                                 "completed": not st.session_state.tasks[idx]["completed"]
                             }))

            # --------- Edit Mode ---------
            if st.session_state.edit_mode[task_index]:
                new_task = cols[1].text_input("Edit", value=task["task"], key=f"edit_input_{task_index}")
                new_due = cols[1].date_input("Due", value=datetime.strptime(task["due"], "%b %d, %Y").date(), key=f"edit_due_{task_index}")
                new_priority = cols[2].selectbox("Priority", ["Low", "Medium", "High"],
                                                 index=["Low", "Medium", "High"].index(task["priority"]), key=f"edit_pri_{task_index}")
                new_category = cols[3].text_input("Category", value=task["category"], key=f"edit_cat_{task_index}")
                cols[4].button("💾", key=f"save_{task_index}", on_click=lambda i=task_index, t=new_task, d=new_due, p=new_priority, c=new_category:
                    (
                        st.session_state.tasks.__setitem__(i, {
                            **st.session_state.tasks[i],
                            "task": t,
                            "due": d.strftime("%b %d, %Y"),
                            "priority": p,
                            "category": c
                        }),
                        st.session_state.edit_mode.__setitem__(i, False)
                    )
                )
                st.button("❌ Cancel", key=f"cancel_{task_index}", on_click=lambda i=task_index: st.session_state.edit_mode.__setitem__(i, False))

            else:
                status = "✅" if task["completed"] else "🔲"
                task_text = f"~~{task['task']}~~" if task["completed"] else task["task"]
                st.markdown(f"**{status} {task_text}**")

                # ✔️ Completed (Top) + Info on new lines (minimal spacing)
                if task["completed"]:
                    st.markdown("<span style='color:green;'>✔️ Completed</span>", unsafe_allow_html=True)

                st.markdown(f"""
📅 **Due:** {task['due']}  
| 🎯 **Priority:** `{task['priority']}`  
| 🗂️ **Category:** `{task['category'] or 'None'}`  
| 🕒 **Created:** {task['created']}
                """, unsafe_allow_html=True)

                btn_cols = st.columns([0.2, 0.2])
                btn_cols[0].button("✏️ Edit", key=f"edit_{task_index}", on_click=lambda i=task_index: st.session_state.edit_mode.__setitem__(i, True))
                btn_cols[1].button("🗑️ Delete", key=f"delete_{task_index}", on_click=lambda i=task_index: (
                    st.session_state.tasks.pop(i),
                    st.session_state.edit_mode.pop(i)
                ))

st.markdown("---")
st.markdown("<p style='text-align:center; font-size: 13px;'>Built with ❤️ using Streamlit. Data resets on refresh.</p>", unsafe_allow_html=True)