# app.py
import streamlit as st
import json
from pathlib import Path
from datetime import datetime
import uuid

DATA_FILE = Path("tasks.json")

def load_tasks():
    if DATA_FILE.exists():
        try:
            return json.loads(DATA_FILE.read_text())
        except Exception:
            return []
    return []

def save_tasks(tasks):
    try:
        DATA_FILE.write_text(json.dumps(tasks, indent=2))
    except Exception:
        pass

if "tasks" not in st.session_state:
    st.session_state.tasks = load_tasks()

st.set_page_config(page_title="Simple Todo", layout="centered")
st.title("📝 Simple Todo App")

# Add task form
with st.form("add_task", clear_on_submit=True):
    new_task = st.text_input("New task")
    submitted = st.form_submit_button("Add")
    if submitted and new_task.strip():
        st.session_state.tasks.append({
            "id": str(uuid.uuid4()),
            "text": new_task.strip(),
            "done": False,
            "created": datetime.utcnow().isoformat()
        })
        save_tasks(st.session_state.tasks)
        st.success("Added")

# Summary
col1, col2, col3 = st.columns([1,1,1])
total = len(st.session_state.tasks)
done = sum(1 for t in st.session_state.tasks if t["done"])
col1.metric("Total", total)
col2.metric("Completed", done)
if col3.button("Clear completed"):
    st.session_state.tasks = [t for t in st.session_state.tasks if not t["done"]]
    save_tasks(st.session_state.tasks)

st.markdown("---")

# Filter
filter_opt = st.radio("Show", ("All", "Active", "Completed"), horizontal=True)

# Display tasks (with per-row actions)
if total == 0:
    st.info("No tasks yet — add one above!")
else:
    for idx, task in enumerate(list(st.session_state.tasks)):
        if filter_opt == "Active" and task["done"]:
            continue
        if filter_opt == "Completed" and not task["done"]:
            continue

        cols = st.columns([0.05, 0.7, 0.15, 0.1])
        checked = cols[0].checkbox("", value=task["done"], key=f"chk_{task['id']}")
        if checked != task["done"]:
            st.session_state.tasks[idx]["done"] = checked
            save_tasks(st.session_state.tasks)

        txt = task["text"]
        if task["done"]:
            cols[1].markdown(f"~~{txt}~~")
        else:
            cols[1].markdown(txt)

        cols[2].markdown(task["created"][:10])
        if cols[3].button("Delete", key=f"del_{task['id']}"):
            st.session_state.tasks.pop(idx)
            save_tasks(st.session_state.tasks)
            st.experimental_rerun()

st.markdown("---")
c1, c2 = st.columns(2)
if c1.button("Save to file"):
    save_tasks(st.session_state.tasks)
    st.success("Saved")
if c2.button("Reload from file"):
    st.session_state.tasks = load_tasks()
    st.success("Reloaded")