#!/bin/bash
targetHost=$1
targetHost=${targetHost%/}
source config
source "$targetHost/config"

if ! which chunked >/dev/null; then
    printf "Requires 'chunked' package from deb2.dogcraft.de\n" >&2
    exit 1
fi



backup_target="$targetHost/backups"
coproc {
    ssh_target "sudo ./backup"
    read -r end
}
read -r line <&${COPROC[0]} || exit 1;
if [[ $line != "Backup service ready" ]]; then
    echo "Backup service did not respond"
    exit 1
fi
function start_backup {
    ident="$(date "+%Y-%m-%d-%H-%M-%S")"
    self="$backup_target/$ident"
    mkdir -p "$self"
    if [[ -h "$backup_target/last" ]]; then
        last="$(readlink "$backup_target/last")"
        ln -s "../$last" "$self/prev"
        rm "$backup_target/last"
    fi
    ln -s "$ident" "$backup_target/last"
}
function base {
    printf "base\n" >&${COPROC[1]}
    chunked decode <&${COPROC[0]} > "$self/pg_base.tar.gz"
    ls -alsh -- "$self/pg_base.tar.gz"
    read -r line <&${COPROC[0]} || exit 1;
    echo "pg_base done: $line"
    echo "Backup info: "
    tar xzO backup_label <  "$self/pg_base.tar.gz"
}
function incremental {
    last=
    hash=
    if [[ $(find -L "$self" -maxdepth 14 -name "pg_base.tar.gz" | wc -l) -lt 1 ]]; then
        printf "doing pg_base backup to $self/pg_base.tar.gz:\n"
        base
        last="$(tar xzO backup_label <  "$self/pg_base.tar.gz" | grep "^START WAL LOCATION: " | sed "s/.*(file \\(.*\\))/\\1/")"
        hash="-"
    else
        last=""
        folder="$self"
        while [[ $last == "" ]]; do
            folder="$folder/prev"
            last="$(tar tf "$folder/pg_wal.tar.gz" | grep "^[A-Z0-9]*$" | tail -n 1)"
        done
        echo "Found last WAL file in backup: $folder"
        hash=$(tar xfO "$folder/pg_wal.tar.gz" "$last" | sha256sum | cut -d" " -f1)
    fi
    printf "Last WAL-name: %s\n" "$last"
    printf "incremental\n" >&${COPROC[1]}
    printf "%s\n" "$last" >&${COPROC[1]}
    printf "%s\n" "$hash" >&${COPROC[1]}
    read -r line <&${COPROC[0]} || exit 1;
    if [[ "$line" != "Ready" ]]; then
        printf "incremental backup didn't start\n"
        exit 1
    fi
    chunked decode <&${COPROC[0]} > "$self/pg_wal.tar.gz"
    printf "Tar contents\n"
    tar tf "$self/pg_wal.tar.gz"
    ls -alsh -- "$self/pg_wal.tar.gz"
    read -r line <&${COPROC[0]} || exit 1;
    if [[ $line == "incremental backup done, confirm cleanup!" ]]; then
        printf "y\n" >&${COPROC[1]}
    else
        printf "Done, but got strange line for cleanup confirmation: %s\n" "$line"
    fi
    printf "Done incremental backup\n"
}

# This code snippet cannot be used inline and therefore has to be a function.
# When calling this function like 'receive_journal "journal" <&$fd', the
# file-descriptor "$fd" is resolved in the calling original shell.
# However when inlining this code like "... | ... <&$fd" the file-descriptor
# is resolved in the first subshell created by this command and therefore
# not valid anymore.
function receive_journal {
    chunked decode | /lib/systemd/systemd-journal-remote -o "$1" -
}
function journal {
    printf "Fetching journals...\n"
    printf "journal\n" >&${COPROC[1]}
    folder="$self"
    for i in {1..10}; do
        folder="$folder/prev"
        if [[ -f "$folder/journal-until" ]]; then
            break;
        fi
    done
    if [[ -f "$folder/journal-until" ]]; then
        printf "From: "
        from="$(cat "$folder/journal-until")"
        date --utc -d "@$from"
        printf -- "%s\n" "$from" >&${COPROC[1]}
    else
        printf "From: start\n"
        printf -- "-\n" >&${COPROC[1]}
    fi
    read -r until <&${COPROC[0]} || exit 1;
    if [[ $until == "no journals" ]]; then
        printf "no journal events\n"
        return 1
    fi
    if [[ ! $until == "Until: "* ]]; then
        printf "Unexpected Until line: %s\n" "$until"
        exit 1
    fi
    until="${until#Until: }"
    printf "until: "
    date --utc -d "@$until"

    printf "Until: %s\n" "$until"
    while :; do
        read -r line <&${COPROC[0]} || exit 1;
        if [[ $line == "end-of-journals" ]]; then
            break;
        fi
        jnl="${line#journal: }"
        printf "journal: %s\n" "$jnl"
        receive_journal "$self/part-$jnl.journal" <&${COPROC[0]}
    done
    journalctl --file="$self/part-*" -o export | /lib/systemd/systemd-journal-remote -o "$self/all.journal" -
    printf "Removing split journals:\n"
    rm -v "$self/part-"*.journal
    cat > "$self/journal-until" <<< "$until"
    ls -als "$self"
}

if [[ "$2" == "restore" ]]; then
    sourceHost=$3
    sourceHost=${sourceHost%/}
    backup_target="${sourceHost}/backups"
    folder="$backup_target/last"
    printf "Restoring backup %s\n" "$(readlink -e -- "$folder")"
    tar tf "$folder/pg_wal.tar.gz"
    while ! [[ -f "$folder/pg_base.tar.gz" ]]; do
        folder="$folder/prev"
        printf "Requires backup %s\n" "$(readlink -e -- "$folder")"
        tar tf "$folder/pg_wal.tar.gz"
    done
    #tar tf "$folder/pg_base.tar.gz"
    printf "restore\n" >&${COPROC[1]}
    read -r reply <&${COPROC[0]} || exit 1;
    if [[ $reply != "postgres base" ]]; then
        printf "Service is not ready to receive backup: %s\n" "$reply"
        exit 1
    fi
    echo "sending base"
    chunked < "$folder/pg_base.tar.gz" >&${COPROC[1]}
    echo "done sending base"
    folder="$backup_target/last"
    while :; do
        read -r reply <&${COPROC[0]} || exit 1;
        if [[ $reply != "incremental?" ]]; then
            printf "Service is not ready to receive backup: %s\n" "$reply"
            exit 1
        fi
        printf "y\n" >&${COPROC[1]}
        printf "Sending pg_wal from %s\n" "$(readlink -e -- "$folder")"
        chunked < "$folder/pg_wal.tar.gz" >&${COPROC[1]}
        if [[ -f "$folder/pg_base.tar.gz" ]]; then
            break
        fi
        folder="$folder/prev"
    done
    read -r reply <&${COPROC[0]} || exit 1;
    if [[ $reply != "incremental?" ]]; then
        printf "Service is not ready to receive backup: %s\n" "$reply"
        exit 1
    fi
    printf "n\n" >&${COPROC[1]}
elif [[ "$2" == "backup" ]]; then
    if ! [[ -x /lib/systemd/systemd-journal-remote ]]; then
        printf "This script requires 'systemd-journal-remote' to reformat received journals\n"
        exit 1
    fi
    start_backup
    incremental
    journal
else
    printf "Error, unknown sub command: %s\n" "$2" >&2
fi


printf "end\n" >&${COPROC[1]}
read -r line <&${COPROC[0]} || exit 1;
printf "END: %s\n" "$line"