#!/bin/bash
# Script to create and run rsync command based on JSON configuration

: <<'COMMENT'
Config File Example (local backup for hs01
==========================================
{
    "Name" : "hs01",
    "Host" : "",

    "BackupHost" : "",
    "BackupRootDir" : "/backup/hs01",

    "Filesystems" : ["/etc", "/opt", "/archive", "/data", "/works" ],

    "RsyncOptions" : ["-arxv", "--delete", "--relative" ],

    "Exclude" : ["*var/tmp*"
                 , "*var/lib/ntp/proc*"
                 , "*.cache*"
                 , "*root/.mozilla*"
                 , "*var/cache*"
                 , "*var/spool*"
                 , "*/.kde4/*"
                 , "/tmp"
               ],

    "DailySnapshots" : false,
    "PruneBackupDays" : 1

}
COMMENT


usage() {
    echo "Usage: ${Script} <json_config_file>"
    exit 1
}


# Check if jq is installed
if ! command -v jq &>/dev/null; then
    echo "Error: jq is required for JSON processing. Install it and try again."
    exit 1
fi

# Verify configuration
verify_config() {
    local config_file="$1"

    # Check if required directories and files exist
    local backup_root_dir
    backup_root_dir=$(jq -r '.BackupRootDir' "$config_file")
    if [[ ! -d "$backup_root_dir" ]]; then
        echo "----- Error: BackupRootDir ($backup_root_dir) does not exist."
        mkdir -p "${backup_root_dir}"
    fi

}

# Run rsync
run_rsync() {
    local cmdlist=("$@")
    echo "----- Running rsync: ${cmdlist[*]}"
    "${cmdlist[@]}"
}

# Prune old backups
prune_backup_dirs() {
    local bkp_host="$1"
    local root_dir="$2"
    local days="$3"

    echo "----- Looking for files to prune..."
    local cmd="cd $root_dir && ls -rd 2* | awk -v days=$days '{ if (NR > days) print }'"
    [[ -n "$bkp_host" ]] && cmd="ssh $bkp_host \"$cmd\""

    echo "----- Command: $cmd"
    local files
    files=$(eval "$cmd")
    if [[ -n "$files" ]]; then
        echo "----- Found files to prune:"
        echo "$files"
        local prune_cmd="rm -rf $(echo "$files" | xargs -I {} echo "$root_dir/{}")"
        [[ -n "$bkp_host" ]] && prune_cmd="ssh $bkp_host \"$prune_cmd\""
        echo "----- Executing: $prune_cmd"
        eval "$prune_cmd"
    else
        echo "----- Nothing to prune."
    fi
}

# Generate rsync arguments
get_rsync_arguments() {
    local config_file="$1"
    local dt="$2"
    local fs="$3"

    local bkp_root_dir
    bkp_root_dir=$(jq -r '.BackupRootDir' "$config_file")
    local daily_snapshots
    daily_snapshots=$(jq -r '.DailySnapshots' "$config_file")
    local rsync_options
    rsync_options=$(jq -r '.RsyncOptions[]' "$config_file")
    local exclude_list
    exclude_list=$(jq -r '.Exclude[]' "$config_file")

    local bkp_dir="$bkp_root_dir"
    [[ "$daily_snapshots" == "true" ]] && bkp_dir="$bkp_root_dir/$dt"

    local cmdlist=("rsync" $rsync_options)
    for excl in $exclude_list; do
        cmdlist+=("--exclude=$excl")
    done
    [[ "$daily_snapshots" == "true" ]] && cmdlist+=("--link-dest=$bkp_root_dir/current")

    local src_host
    src_host=$(jq -r '.Host' "$config_file")
    [[ -n "$src_host" ]] && src_host="$src_host:"

    local tgt_host
    tgt_host=$(jq -r '.BackupHost' "$config_file")
    [[ -n "$tgt_host" ]] && tgt_host="$tgt_host:"

    cmdlist+=("${src_host}${fs}" "${tgt_host}${bkp_dir}/")

    echo "${cmdlist[@]}"
}

# Main function
main() {
    local config_file="$1"
    if [[ ! -f "$config_file" ]]; then
        echo "----- Error: Configuration file $config_file does not exist."
        exit 1
    fi

    if ! verify_config "$config_file"; then
        exit 1
    fi

    local dt
    dt=$(date +%Y%m%d)

    local filesystems
    filesystems=$(jq -r '.Filesystems[]' "$config_file")
    for fs in $filesystems; do
        echo "----- Processing filesystem: $fs"
        local cmdlist
        cmdlist=($(get_rsync_arguments "$config_file" "$dt" "$fs"))
        run_rsync "${cmdlist[@]}"
    done

    local daily_snapshots
    daily_snapshots=$(jq -r '.DailySnapshots' "$config_file")
    if [[ "$daily_snapshots" == "true" ]]; then
        local bkp_root_dir
        bkp_root_dir=$(jq -r '.BackupRootDir' "$config_file")
        local bkp_host
        bkp_host=$(jq -r '.BackupHost' "$config_file")
        local cmd="ln -snf $bkp_root_dir/$dt $bkp_root_dir/current"
        [[ -n "$bkp_host" ]] && cmd="ssh $bkp_host \"$cmd\""
        echo "----- Switching current symlink: $cmd"
        eval "$cmd"

        local prune_days
        prune_days=$(jq -r '.PruneBackupDays' "$config_file")
        if [[ "$prune_days" -gt 0 ]]; then
            local bkp_root_dir
            bkp_root_dir=$(jq -r '.BackupRootDir' "$config_file")
            local bkp_host
            bkp_host=$(jq -r '.BackupHost' "$config_file")
            prune_backup_dirs "$bkp_host" "$bkp_root_dir" "$prune_days"
        fi
    fi
}

# Entry point
Script=${0}
Config=${1}
if [[ $# -lt 1 ]]; then
    usage
    exit 1
fi

main "${Config}"