"""DataTools Combine Files — stub page."""

from __future__ import annotations

import sys
from pathlib import Path

import streamlit as st

_project_root = Path(__file__).resolve().parent.parent.parent.parent
if str(_project_root) not in sys.path:
    sys.path.insert(0, str(_project_root))

from src.gui.components import (
    back_to_home_link,
    render_sticky_footer,
    render_tool_header,
    hide_streamlit_chrome,
    require_feature_or_render_upgrade,
)
from src.license import FeatureFlag

hide_streamlit_chrome()
render_sticky_footer()
back_to_home_link()
from src.audit import log_page_open
log_page_open("7_Multi_File_Merger")
require_feature_or_render_upgrade(FeatureFlag.MULTI_FILE_MERGER)

# ---------------------------------------------------------------------------
# Header
# ---------------------------------------------------------------------------

render_tool_header("07_multi_file_merger")

st.info("This tool is under development.")

# ---------------------------------------------------------------------------
# What this tool will do
# ---------------------------------------------------------------------------

st.markdown("""
**Features:**
- Import multiple CSV/Excel files at once
- Automatic schema alignment (matching columns by name)
- Append mode: stack files vertically (union)
- Join mode: merge files on shared key columns
- Handle mismatched columns (fill missing with nulls or drop)
- Source file tracking column
""")

st.divider()

# ---------------------------------------------------------------------------
# Multi-file upload (functional)
# ---------------------------------------------------------------------------

uploaded_files = st.file_uploader(
    "Import CSV or Excel files",
    type=["csv", "tsv", "xlsx", "xls"],
    accept_multiple_files=True,
    help="Import multiple files to preview. Processing is not yet available.",
    key="merger_file_upload",
)

if uploaded_files:
    import pandas as pd
    for f in uploaded_files:
        try:
            if f.name.endswith((".xlsx", ".xls")):
                df = pd.read_excel(f)
            else:
                df = pd.read_csv(f)
            st.subheader(f"Preview: {f.name}")
            st.caption(f"{len(df)} rows, {len(df.columns)} columns — Columns: {', '.join(df.columns[:10])}{'...' if len(df.columns) > 10 else ''}")
            st.dataframe(df.head(5), width="stretch")
        except Exception as e:
            from src.core.errors import format_for_user
            st.error(
                f"**Could not read `{f.name}`**\n\n"
                f"```\n{format_for_user(e)}\n```"
            )

# ---------------------------------------------------------------------------
# Placeholder options
# ---------------------------------------------------------------------------

st.subheader("Merge Strategy")

st.selectbox("Mode", ["Append (stack vertically)", "Join on key columns", "Schema alignment (smart merge)"], disabled=True)
st.selectbox("Mismatched columns", ["Fill with null", "Drop non-shared columns", "Error"], disabled=True)
st.checkbox("Add source filename column", value=True, disabled=True)

st.divider()
st.button("Merge Files", type="primary", width="stretch", disabled=True)