#!/bin/bash
set -e

DATA_DIR="/var/lib/postgresql/data"
OLD_VERSION_FILE="$DATA_DIR/PG_VERSION"
NEW_VERSION="16"
OLD_BIN="/usr/lib/postgresql/15/bin"
NEW_BIN="/usr/lib/postgresql/16/bin"

if [ -f "$OLD_VERSION_FILE" ]; then
    OLD_VERSION=$(cat "$OLD_VERSION_FILE")

    if [ "$OLD_VERSION" != "$NEW_VERSION" ]; then
        echo "Data version ($OLD_VERSION) differs from engine ($NEW_VERSION). Starting upgrade..."
        
        # Move old data to a temporary folder
        mkdir -p $DATA_DIR/old_data
        mv $DATA_DIR/* $DATA_DIR/old_data/ || true
				chmod 700 $DATA_DIR/old_data
        
        # Initialize new data directory
				mkdir $DATA_DIR/new_data
        initdb -D $DATA_DIR/new_data

				# Prevent error "You must have read and write access in the current directory."
				cd $DATA_DIR
        
        # Run pg_upgrade
        # --link is used to avoid copying files (fast, but requires a backup!)
        if ! pg_upgrade \
            -d $DATA_DIR/old_data \
            -D $DATA_DIR/new_data \
            -b "$OLD_BIN" \
            -B "$NEW_BIN" \
						-s /tmp \
            --link; then

						echo "========================================"
            echo "pg_upgrade FAILED! Here is the actual reason why the old server crashed:"
            echo "========================================"
            
            # Print the contents of the server log
            cat "$DATA_DIR"/new_data/pg_upgrade_output.d/*/log/pg_upgrade_server.log
            
            # Exit to prevent the script from continuing
            exit 1
				fi

				# Migrate configuration files
				echo "Upgrade complete. Cleaning up..."
        cp "$DATA_DIR/old_data/pg_hba.conf" "$DATA_DIR/new_data/pg_hba.conf"
        cp "$DATA_DIR/old_data/postgresql.conf" "$DATA_DIR/new_data/postgresql.conf"
        if [ -f "$DATA_DIR/old_data/pg_ident.conf" ]; then
            cp "$DATA_DIR/old_data/pg_ident.conf" "$DATA_DIR/new_data/pg_ident.conf"
        fi

        # Ensure the postgres user owns the restored files
        chown postgres:postgres "$DATA_DIR"/new_data/*.conf
        
				# Clean-up
        rm -rf $DATA_DIR/old_data
				mv $DATA_DIR/new_data/* $DATA_DIR/
				rmdir $DATA_DIR/new_data
    fi
fi

exec $@