import streamlit as st

st.markdown(
    """
# Multi Points Distance Calculator Documentation

## 1. Objective
Calculate distances between two datasets of points and identify closest matches.

## 2. When to use this tool
Use this page to compare reference sites against candidate/neighbor sites and find nearest pairs.

## 3. Input files and accepted formats
- Required: Dataset 1 in `.xlsx`
- Required: Dataset 2 in `.xlsx`
- Samples: `samples/Dataset1.xlsx`, `samples/Dataset2.xlsx`

## 4. Required columns/fields
For each dataset, select:
- code column
- latitude column
- longitude column

## 5. Step-by-step usage
1. Open `Apps > Multi Points Distance Calculator`.
2. Upload both Excel datasets.
3. Select code/latitude/longitude columns for each dataset.
4. Set minimum distance threshold (km).
5. Click `Calculate Distances`.
6. Review closest matches and download CSV outputs.

## 6. Outputs generated
- closest matches table
- closest matches below threshold table
- downloadable files:
  - `all_distances.csv`
  - `closest_matches.csv`
  - `closest_matches_<threshold>km.csv`

## 7. Frequent errors and fixes
- Processing error after upload.
  - Fix: verify selected columns and coordinate formats.
- No close matches below threshold.
  - Fix: increase threshold value.
- Unexpected distances.
  - Fix: ensure coordinates are decimal degrees.

## 8. Minimal reproducible example
- Input: `Dataset1.xlsx` and `Dataset2.xlsx` samples.
- Action: select columns and run with threshold `5 km`.
- Expected result: closest matches plus downloadable CSV files.

## 9. Known limitations
- Only `.xlsx` inputs are supported.
- Quality depends on coordinate accuracy.
- Large datasets may take longer to compute.

## 10. Version and update date
- Documentation version: 1.0
- Last update: 2026-02-23
"""
)