#!/bin/bash

# ==============================================================================
# Script Description:
# This script connects an existing local directory to a remote Git repository.
# It requires the SSH URL of the Git repository as an input argument.
# 
# Process:
# 1. Initializes a new local Git repository.
# 2. Adds the provided URL as the remote 'origin'.
# 3. Fetches the remote repository data.
# 4. Checks for differences between the local files and 'origin/master'.
# 5. If there are no differences, it sets up tracking for the master branch
#    and performs a hard reset to synchronize exactly with the remote.
#
# Usage:
#   ./connect_git.sh <repository-ssh-url>
#
# Example:
#   ./connect_git.sh git@github.com:username/repository.git
# ==============================================================================

# Check if the repository URL argument is provided
if [ -z "$1" ]; then
    echo "Error: No repository SSH URL provided."
    echo "Usage: $0 <repository-ssh-url>"
    exit 1
fi

REPO_URL=$1
BRANCH="master"

echo "Initializing Git repository..."
git init

echo "Adding remote 'origin' -> $REPO_URL"
git remote add origin "$REPO_URL"

echo "Fetching from origin..."
git fetch origin

# Check differences between the local working directory and the remote branch.
# Using 'git diff --quiet origin/master' safely checks without needing HEAD to exist.
echo "Checking differences..."
if git diff --quiet "origin/$BRANCH"; then
    echo "No differences found between local folder and remote origin/$BRANCH."
    
    echo "Setting up tracking and aligning with remote..."
    # Ensure we are on the master branch
    git checkout -B "$BRANCH"
    # Set the upstream tracking branch
    git branch --set-upstream-to="origin/$BRANCH" "$BRANCH"
    # Hard reset to match the remote exactly
    git reset --hard "origin/$BRANCH"
    
    echo "Success! The local folder is now completely linked to the remote repository."
else
    echo "Notice: Differences exist between the local files and origin/$BRANCH."
    echo "Tracking was not set automatically. You can review differences using:"
    echo "  git diff origin/$BRANCH"
    exit 1
fi