#!/bin/bash
# vim: et
set -Eeuo pipefail

# @PERF: Currently this script only supports processing a single file at
# a time. Ideally it should probably support multiple files. That would also
# allow it to cache some of the results of fetching new versions instead of
# having to fetch them every time. As it stands right now we could only cache
# that for one file, and the chance that you're using the same image multiple
# times in one docker file seems vanishingly small

function help {
    cat <<EOH
Usage:
 $0 [options] [--] <FILE>
Upgrade the image versions in FILE to latest version

Options:
 -v <level>                  Increase verbosity (repeatable)
 -d                          Dry run (don't apply the updates)
 -t, --type <TYPE>           Type of file (defaults to DOCKER)
 --insecure                  Disable SSL verification
 -h, --help                  You are looking at it
EOH
}

function vecho {
    LEVEL="$1"
    shift
    if [[ $VERBOSE -ge $LEVEL ]]; then
        echo -e "$@" >&2
    fi
}

VERBOSE=0
DRY_RUN=false
POSITIONAL=()
CURL_OPTS=""
TYPE="DOCKER"

# Read arguments
while [[ "$#" -gt 0 ]]; do
    case "$1" in
        '-h'|'--help')
            help
            exit 0
            ;;
        '-v')
            VERBOSE=$((VERBOSE + 1))
            shift
            if [[ "$#" -gt 0 ]] && [[ "$1" =~ ^[0-9]+$ ]]; then
                VERBOSE="$1"
                shift
            fi
            ;;
        '-d'|'--dry')
            shift
            TYPE=$1
            shift
            ;;
        '-t'|'--type')
            DRY_RUN=true
            shift
            ;;
        '--insecure')
            CURL_OPTS="$CURL_OPTS --insecure"
            shift
            ;;
        *)
            POSITIONAL+=("$1")
            shift
            ;;
    esac
done

if [[ ${#POSITIONAL[@]} -lt 1 ]]; then
    echo "Too few arguments" >&2
    help >&2
    exit 1
fi

if [[ ${#POSITIONAL[@]} -gt 1 ]]; then
    echo "Too many arguments" >&2
    help >&2
    exit 1
fi

case "${TYPE^^}" in
    'DOCKER')
        TYPE="DOCKER"
        ;;
    'KUBE')
        TYPE="KUBE"
        ;;
    *)
        echo "Unknown TYPE"
        exit 1
        ;;
esac

FILE="${POSITIONAL[0]}"

function rel_next {
    while IFS= read -r line; do
        vecho 2 "Processing link header \"$line\""
        regex="^<([^>]*)>(; ([^=]*)=([^;]*))*$"
        if ! [[ $line =~ $regex ]]; then
            printf "Could not parse link header %s\n", "$line" >&2
            exit 1
        fi

        link_param_len=$(((${#BASH_REMATCH[@]} - 2) / 3))
        vecho 3 "Link contains $link_param_len params"

        for((i=0; i<link_param_len; i++)); do
            rematch_index=$((i * 3 + 2))
            name="${BASH_REMATCH[$rematch_index+1]}"
            value="${BASH_REMATCH[$rematch_index+2]}"

            vecho 4 "Param $i is $name=$value"

            if [[ "$name" == "rel" ]] && [[ "$value" == "\"next\"" ]]; then
                vecho 4 "Param $i matches"
                printf "%s\n" "${BASH_REMATCH[1]}"
            fi
        done
    done < <(jq -r -s '.[1].link // [] | .[]')
}

function version_index {
    regex="^.+-([^-]+)$"
    if ! [[ $1 =~ $regex ]]; then
        printf "Tag did not match version scheme %s\n" "$1"
    fi

    echo "${BASH_REMATCH[1]}"
}

function is_newer_than {
    # This comparison function only works for our very weird versioning scheme

    build_type=$(rev <<<"$2" | cut -s -d - -f 2 | rev)
    if [[ "$build_type" != "RB" ]]; then
        vecho 2 "$2 is not a release build"
        return 1
    fi

    # If we haven't selected a version, select this one
    if [[ -z "$1" ]]; then
        return 0
    fi

    # @SPEED: This is a really slow way of doing this check. Since all the tags
    # should have the same prefix there's a potential speedup where we read
    # that length out and just skip that many bytes instead of doing this whole
    # regex thing
    i1=$(version_index "$1")
    i2=$(version_index "$2")
    vecho 2 "Compare ${i1}[$1] < ${i2}[$2]"
    (( $i1 < $i2 ))
}

function find_latest_version_of {
    HOST="$1"
    IMAGE="$2"
    vecho 2 "Resolving latest version of $IMAGE"
    version=""

    next_link="https://$HOST/v2/$IMAGE/tags/list?n=100"
    while true; do
        # CURL -w (write-out) writes the specified thing AFTER printing the
        # response body. The headers will be printed AFTER the body
        http_response=$(curl $CURL_OPTS -n -f --silent "$next_link" -w "%{header_json}")
        if [[ $? -ne 0 ]]; then
            printf "Fetching version of %s failed: %s\n" "$IMAGE" "$http_response" >&2
            exit 1
        fi

        while IFS= read -r line; do
            if is_newer_than "$version" "$line"; then
                version="$line"
            fi
        done < <(jq -r -s '.[0].tags | .[]' <<<"$http_response")

        vecho 2 "Page done, looking for next page"
        next_link=$(rel_next <<<"$http_response")
        if [[ "$next_link" == "" ]]; then
            break;
        else
            vecho 2 "Next page located at $next_link"
        fi
    done

    vecho 1 "Latest version of $IMAGE is $version"
    echo "$version"
}

function images_in_file {
    # -r is specifically omitted here to allow backslash to escape newlines
    while IFS=" " read ln cmd rest; do
        if [[ "$cmd" != "FROM" ]]; then
            continue
        fi
        vecho 3 "The args to FROM is $rest"
        image=$(cut -d " " -f 1 <<<"$rest")
        vecho 1 "Image $image extracted"
        # the docker FROM command takes an optional argument that starts with
        # --, we don't support that so try and detect it to bail
        if [[ "$image" == "-*" ]]; then
            printf "Options to FROM are not supported\n" >&2
            exit 1
        fi
        echo "$ln:$image"
    # We wan't to track the line number to hopefully constrain the coming
    # update to the correct part of the dockerfile. Ideally we'd track the
    # ftell to be completely accurate, but that's difficult (if not impossible)
    # in bash
    # The sed removes comment, it skips the first 5 chars to skip the line
    # number (4 numbers for the line and one space as a separator)
    done < <(nl -w4 -s" " "$1" | sed '/^.{5}\s*#/d' -)
}

function images_in_kube {
    # -r is specifically omitted here to allow backslash to escape newlines
    while IFS=" " read ln content; do
        regex="^(-\s)?image:\s+([a-zA-Z0-9:/.@]+)\s*$"
        if ! [[ $content =~ $regex ]]; then
            continue
        fi

        image="${BASH_REMATCH[2]}"
        echo "$ln:$image"
    # We wan't to track the line number to hopefully constrain the coming
    # update to the correct part of the file. Ideally we'd track the ftell to
    # be completely accurate, but that's difficult (if not impossible) in bash
    # The sed removes comment, it skips the first 5 chars to skip the line
    # number (4 numbers for the line and one space as a separator)
    done < <(nl -w4 -s" " "$1" | sed '/^.{5}\s*#/d' -)
}

function search_for_newer_version {
    while IFS= read -r line; do
        ln=$(cut -d":" -f 1 <<<"$line")
        content=$(cut -d":" -f 2- <<<"$line")
        image_name=$(cut -s -d "@" -f 1 <<<"$content")
        digest=$(cut -s -d "@" -f 2 <<<"$content")
        tag=$(cut -s -d ":" -f 2 <<<"$image_name")
        host=$(cut -s -d "/" -f 1 <<<"$image_name")
        image=$(cut -d ":" -f 1 <<<"$image_name" | cut -d "/" -f 2)

        new_tag=$(find_latest_version_of "$host" "$image")
        if [[ "$tag" == "$new_tag" ]]; then
            continue
        fi

        vecho 1 "Image $image on line $ln was $tag should be updated to $new_tag"
        echo "$ln:$host:$image:$tag:$new_tag"
    done
}

function generate_script {
    # Format the colon separated values as a sed script to be run later (or
    # printed if dry-run is on)
    awk -F":" '{print $1 "s/" $2 "\\/" $3 ":" $4 "/" $2 "\\/" $3 ":" $5 "/"}'
}

if [[ $DRY_RUN == "false" ]]; then
    function apply_script {
        sed -f- -i "$1"
    }
else
    function apply_script {
        script=$(cat)
        printf "Would have applied sed script:\n"
        printf "%s\n" "$script"
    }
fi

# Digests are excluded since don't really use them
images_in_kube "$FILE" | search_for_newer_version #| generate_script | apply_script "$FILE"