import streamlit as st
import pandas as pd
from datetime import datetime
import os
import matplotlib.pyplot as plt

DATA_FILE = "habits.csv"

# ---------- Page Config ----------
st.set_page_config(page_title="Habit Tracker", layout="centered")

# ---------- CLEAN LIGHT GRAY UI ----------
st.markdown("""
<style>
.block-container {
    padding-top: 2rem;
    padding-bottom: 2rem;
    background-color: #f3f4f6;
}

/* Global text visibility */
h1, h2, h3, p, div {
    color: #0f172a !important;
}

/* Card */
.card {
    background: #ffffff;
    padding: 14px;
    border-radius: 12px;
    border-left: 5px solid #38bdf8;
    box-shadow: 0 2px 10px rgba(0,0,0,0.06);
    margin-bottom: 10px;
}

/* Streak */
.streak {
    color: #b45309;
    font-weight: 600;
}

/* Buttons */
.stButton > button {
    background-color: #38bdf8;
    color: white;
    border-radius: 8px;
    border: none;
}

.stButton > button:hover {
    background-color: #0ea5e9;
}

/* Subtle spacing */
.css-1d391kg {
    padding-top: 1rem;
}
</style>
""", unsafe_allow_html=True)

# ---------- DATA ----------
def load_data():
    if os.path.exists(DATA_FILE):
        return pd.read_csv(DATA_FILE)
    return pd.DataFrame(columns=["Habit", "Streak", "Last Completed"])

def save_data(df):
    df.to_csv(DATA_FILE, index=False)

if "habits" not in st.session_state:
    st.session_state.habits = load_data()

df = st.session_state.habits

# ---------- TITLE ----------
st.title("Habit Tracker")
st.write("Build consistency through daily habits")

# ---------- ADD HABIT ----------
st.subheader("Add Habit")

col1, col2 = st.columns([4, 1])
with col1:
    new_habit = st.text_input("Enter habit", label_visibility="collapsed")

with col2:
    if st.button("Add"):
        if new_habit.strip():
            if new_habit not in df["Habit"].values:
                df = pd.concat(
                    [df, pd.DataFrame([[new_habit, 0, "Never"]], columns=df.columns)],
                    ignore_index=True
                )
                st.session_state.habits = df
                save_data(df)
                st.success("Added successfully")
            else:
                st.warning("Habit already exists")

# ---------- HABITS ----------
st.subheader("Your Habits")

today = datetime.now().date()

if df.empty:
    st.info("No habits added yet")
else:
    for i, row in df.iterrows():

        col1, col2, col3 = st.columns([5, 1, 1])

        with col1:
            st.markdown(f"""
            <div class="card">
                <div style="font-size:16px; font-weight:600;">
                    {row['Habit']}
                </div>
                <div class="streak">
                    Streak: {row['Streak']}
                </div>
            </div>
            """, unsafe_allow_html=True)

        with col2:
            if st.button("Done", key=f"done_{i}"):

                last_date = row["Last Completed"]

                if last_date != "Never":
                    last_date = pd.to_datetime(last_date).date()

                    if (today - last_date).days == 1:
                        df.loc[i, "Streak"] += 1
                    elif (today - last_date).days > 1:
                        df.loc[i, "Streak"] = 1
                else:
                    df.loc[i, "Streak"] = 1

                df.loc[i, "Last Completed"] = str(today)

                st.session_state.habits = df
                save_data(df)
                st.rerun()

        with col3:
            if st.button("Delete", key=f"del_{i}"):
                df = df[df["Habit"] != row["Habit"]]
                st.session_state.habits = df
                save_data(df)
                st.rerun()

# ---------- GRAPH ----------
st.subheader("Progress Overview")

if not df.empty:
    fig, ax = plt.subplots()
    ax.bar(df["Habit"], df["Streak"], color="#38bdf8")
    ax.set_facecolor("#f3f4f6")
    ax.set_ylabel("Streak")
    plt.xticks(rotation=20)
    st.pyplot(fig)