path: root/kiss

#!/bin/sh -ef
# shellcheck source=/dev/null
#
# This is a simple package manager written in POSIX 'sh' for use
# in KISS Linux (https://k1ss.org).
#
# This script runs with '-ef' meaning:
# '-e': Abort on any non-zero exit code.
# '-f': Disable globbing globally.
#
# [1] Warnings related to word splitting and globbing are disabled.
# All word splitting in this script is *safe* and intentional.
#
# Dylan Araps.

log() {
    # Print a message prettily.
    #
    # All messages are printed to stderr to allow the user to hide build
    # output which is the only thing printed to stdout.
    #
    # '\033[1;32m'        Set text to color '2' and make it bold.
    # '\033[m':           Reset text formatting.
    # '${3:-->}':         If the 3rd argument is missing, set prefix to '->'.
    # '${2:+\033[1;3Xm}': If the 2nd argument exists, set text style of '$1'.
    printf '\033[1;33m%s \033[m%b%s\033[m %s\n' \
           "${3:-->}" "${2:+"\033[1;36m"}" "$1" "$2" >&2
}

die() {
    # Print a message and exit with '1' (error).
    log "$1" "$2" "!>"
    exit 1
}

warn() {
    # Print a warning message
    log "WARN" "$1" "${2:-!>}"
}

contains() {
    # Check if a "string list" contains a word.
    case " $1 " in *" $2 "*) return 0; esac; return 1
}

prompt() {
    # If a KISS_NOPROMPT variable is set, continue.
    # This can be useful for installation scripts and
    # bootstrapping.
    [ "$KISS_NOPROMPT" ] && return 0

    # Ask the user for some input.
    [ "$1" ] && log "$1"
    log "Continue?: Press Enter to continue or Ctrl+C to abort here"

    # POSIX 'read' has none of the "nice" options like '-n', '-p'
    # etc etc. This is the most basic usage of 'read'.
    # '_' is used as 'dash' errors when no variable is given to 'read'.
    read -r _ || return 1
}

as_root() {
    # Simple function to run a command as root using either 'sudo',
    # 'doas' or 'su'. Hurrah for choice.
    [ "$uid" = 0 ] || log "Using '${su:-su}' (to become ${user:=root})"

    case $su in
        *sudo) sudo -E -u "$user" -- "$@" ;;
        *doas) doas    -u "$user" -- "$@" ;;
        *)     su -pc "$* <&3" "$user" 3<&0 </dev/tty ;;
    esac
}

pop() {
    # Remove an item from a "string list". This allows us
    # to remove a 'sed' call and reuse this code throughout.
    del=$1
    shift 2

    for i do [ "$i" = "$del" ] || printf %s " $i "; done
}

run_hook() {
    # This is not a misspelling, can be ignored safely.
    # shellcheck disable=2153
    [ "$KISS_HOOK" ] || return 0

    log "$2" "Running $1 hook"

    TYPE=$1 PKG=$2 DEST=$3 . "$KISS_HOOK"
}

decompress() {
    case $1 in
        *.tar)      cat       ;;
        *.bz2)      bzip2 -cd ;;
        *.xz|*.txz) xz -dcT 0 ;;
        *.tgz|*.gz) gzip -cd  ;;
        *.zst)      zstd -cd  ;;
    esac < "$1"
}

hashcheck() {
    # This is a sha256sum function for outputting a standard
    # hash digest. sha256 on BSD systems require an '-r' flag
    # for outputting the same way with sha256sum, and still,
    # it outputs a single space between the hash and the file
    # whereas sha256sum outputs double spaces. It fallbacks to
    # openssl, but that is rarely ever needed.
    { sha256sum "$1" 2>/dev/null   ||
      sha256 -r "$1" 2>/dev/null   ||
      openssl dgst -r -sha256 "$1" ||
      die "No sha256 program could be run." ;} |

        while read -r hash _; do printf '%s  %s\n' "$hash" "$1"; done
}

pkg_lint() {
    # Check that each mandatory file in the package entry exists.
    log "$1" "Checking repository files"

    repo_dir=$(pkg_find "$1")

    cd "$repo_dir" || die "'$repo_dir' not accessible"
    [ -f sources ] || die "$1" "Sources file not found"
    [ -x build ]   || die "$1" "Build file not found or not executable"
    [ -s version ] || die "$1" "Version file not found or empty"

    read -r _ release 2>/dev/null < version || die "Version file not found"
    [ "$release" ] || die "Release field not found in version file"

    [ "$2" ] || [ -f checksums ] || die "$pkg" "Checksums are missing"
}

pkg_find() {
    # Use a SEARCH_PATH variable so that we can get the sys_db into
    # the same variable as KISS_PATH. This makes it easier when we are
    # searching for executables instead of KISS_PATH.
    : "${SEARCH_PATH:=$KISS_PATH:$sys_db}"

    # Figure out which repository a package belongs to by
    # searching for directories matching the package name
    # in $KISS_PATH/*.
    query=$1 match=$2 type=$3 IFS=:; set --

    # Word splitting is intentional here.
    # shellcheck disable=2086
    for path in $SEARCH_PATH ; do
        set +f

        for path2 in "$path/"$query; do
            test "${type:--d}" "$path2" && set -f -- "$@" "$path2"
        done
    done

    unset IFS

    # A package may also not be found due to a repository not being
    # readable by the current user. Either way, we need to die here.
    [ "$1" ] || die "Package '$query' not in any repository"

    # Show all search results if called from 'kiss search', else
    # print only the first match.
    [ "$match" ] && printf '%s\n' "$@" || printf '%s\n' "$1"
}

pkg_list() {
    # List installed packages. As the format is files and
    # directories, this just involves a simple for loop and
    # file read.

    # Change directories to the database. This allows us to
    # avoid having to 'basename' each path. If this fails,
    # set '$1' to mimic a failed glob which indicates that
    # nothing is installed.
    cd "$sys_db" 2>/dev/null || set -- "$sys_db/"\*

    # Optional arguments can be passed to check for specific
    # packages. If no arguments are passed, list all. As we
    # loop over '$@', if there aren't any arguments we can
    # just set the directory contents to the argument list.
    [ "$1" ] || { set +f; set -f -- *; }

    # If the 'glob' above failed, exit early as there are no
    # packages installed.
    [ "$1" = "$sys_db/"\* ] && return 1

    # Loop over each package and print its name and version.
    for pkg do
        [ -d "$pkg" ] || { log "$pkg" "not installed"; return 1; }

        read -r version 2>/dev/null < "$pkg/version" || version=null
        printf '%s\n' "$pkg $version"
    done
}

pkg_cache() {
    read -r version release 2>/dev/null < "$(pkg_find "$1")/version"

    set +f; set -f -- "$bin_dir/$1#$version-$release.tar."*
    tar_file=$1

    [ -f "$tar_file" ]
}

pkg_sources() {
    # Download any remote package sources. The existence of local
    # files is also checked.
    log "$1" "Downloading sources"

    # Store each downloaded source in a directory named after the
    # package it belongs to. This avoid conflicts between two packages
    # having a source of the same name.
    mkdir -p "$src_dir/$1" && cd "$src_dir/$1"

    repo_dir=$(pkg_find "$1")

    while read -r src dest || [ "$src" ]; do
        # Comment.
        if [ -z "${src##\#*}" ]; then :

        # Remote source (cached).
        elif [ -f "${src##*/}" ]; then
            log "$1" "Found cached source '${src##*/}'"

        # Remote git repository.
        elif [ -z "${src##git+*}" ]; then
            # This is a checksums check, skip it.
            [ "$2" ] && continue

            mkdir -p "$mak_dir/$1/$dest"

            # Run in a subshell to keep the variables, path and
            # argument list local to each loop iteration.
            (
                repo_src=${src##git+}

                log "$1" "Cloning ${repo_src%[@#]*}"

                # Git has no option to clone a repository to a
                # specific location so we must do it ourselves
                # beforehand.
                cd "$mak_dir/$1/$dest" 2>/dev/null || die

                # Clear the argument list as we'll be overwriting
                # it below based on what kind of checkout we're
                # dealing with.
                set -- "$repo_src"

                # If a branch was given, shallow clone it directly.
                # This speeds things up as we don't have to grab
                # a lot of unneeded commits.
                [ "${src##*@*}" ] ||
                    set -- -b "${src##*@}" "${repo_src%@*}"

                # Maintain compatibility with older versions of
                # kiss by shallow cloning all branches. This has
                # the added benefit of allowing checkouts of
                # specific commits in specific branches.
                [ "${src##*#*}" ] ||
                    set -- --no-single-branch "${repo_src%#*}"

                # Always do a shallow clone as we will unshallow it if
                # needed later (when a commit is desired).
                git clone --depth=1 "$@" .

            ) || die "$1" "Failed to clone $src"

        # Remote source.
        elif [ -z "${src##*://*}" ]; then
            log "$1" "Downloading $src"

            curl "$src" -fLo "${src##*/}" || {
                rm -f "${src##*/}"
                die "$1" "Failed to download $src"
            }

        # Local source.
        elif [ -f "$repo_dir/$src" ]; then
            log "$1" "Found local file '$src'"

        else
            die "$1" "No local file '$src'"
        fi
    done < "$repo_dir/sources"
}

pkg_extract() {
    # Extract all source archives to the build directory and copy over
    # any local repository files.
    log "$1" "Extracting sources"

    repo_dir=$(pkg_find "$1")

    while read -r src dest || [ "$src" ]; do
        mkdir -p "$mak_dir/$1/$dest" && cd "$mak_dir/$1/$dest"

        case $src in
            # Git repository with supplied commit hash.
            git+*\#*)
                log "Checking out ${src##*#}"

                # A commit was requested, unshallow the repository.
                # This will convert it to a regular repository with
                # full history.
                git fetch --unshallow

                # Try to checkout the repository. If we fail here,
                # the requested commit doesn't exist.
                git -c advice.detachedHead=false checkout "${src##*#}" ||
                    die "Commit hash ${src##*#} doesn't exist"
            ;;

            # Git repository, comment or blank line.
            git+*|\#*|'') continue ;;

            # Only 'tar' an 'zip' archives are currently supported for
            # extraction. Other filetypes are simply copied to '$mak_dir'
            # which allows for manual extraction.
            *://*.tar|*://*.tar.??|*://*.tar.???|*://*.tar.????|*://*.tgz|*://*.txz)

                decompress "$src_dir/$1/${src##*/}" > .ktar

                "$tar" xf .ktar || die "$1" "Couldn't extract ${src##*/}"

                # We now list the contents of the tarball so we can do our
                # version of 'strip-components'.
                "$tar" tf .ktar |
                    while read -r file; do printf '%s\n' "${file%%/*}"; done |

                    # Do not repeat files.
                    uniq |

                    # For every directory in the base we move each file
                    # inside it to the upper directory.
                    while read -r dir ; do

                        # Skip if we are not dealing with a directory here.
                        # This way we don't remove files on the upper directory
                        # if a tar archive doesn't need directory stripping.
                        [ -d "${dir#.}" ] || continue

                        # Change into the directory in a subshell so we don't
                        # need to cd back to the upper directory.
                        (
                            cd "$dir"

                            # We use find because we want to move hidden files
                            # as well.
                            #
                            # Skip the file if it has the same name as the directory.
                            # We will deal with it later.
                            #
                            # Word splitting is intentional here.
                            # shellcheck disable=2046
                            set -- $(find . \( ! -name . -prune \) ! -name "$dir")
                            mv -f "$@" ..

                            # If a file/directory with the same name as the directory
                            # exists, append a '.kissbak' to it and move it to the
                            # upper directory.
                            ! [ -e "$dir" ] || mv "$dir" "../${dir}.kissbak"
                        )
                        rmdir "$dir"

                        # If a backup file exists, move it into the original location.
                        ! [ -e "${dir}.kissbak" ] || mv "${dir}.kissbak" "$dir"
                done

                # Clean up the temporary tarball.
                rm -f .ktar
            ;;

            *://*.zip)
                unzip "$src_dir/$1/${src##*/}" ||
                    die "$1" "Couldn't extract ${src##*/}"

            ;;

            *)
                # Local file.
                if [ -f "$repo_dir/$src" ]; then
                    cp -f "$repo_dir/$src" .

                # Remote file.
                elif [ -f "$src_dir/$1/${src##*/}" ]; then
                    cp -f "$src_dir/$1/${src##*/}" .

                else
                    die "$1" "Local file $src not found"
                fi
            ;;
        esac
    done < "$repo_dir/sources"
}

pkg_depends() {
    # Resolve all dependencies and generate an ordered list.
    # This does a depth-first search. The deepest dependencies are
    # listed first and then the parents in reverse order.
    contains "$deps" "$1" || {
        # Filter out non-explicit, aleady installed dependencies.
        # Only filter installed if called from 'pkg_build()'.
        [ "$pkg_build" ] && [ -z "$2" ] &&
            (pkg_list "$1" >/dev/null) && return

        # Recurse through the dependencies of the child packages.
        while read -r dep _ || [ "$dep" ]; do
            [ "${dep##\#*}" ] && pkg_depends "$dep"
        done 2>/dev/null < "$(pkg_find "$1")/depends" ||:

        # After child dependencies are added to the list,
        # add the package which depends on them.
        [ "$2" = explicit ] || deps="$deps $1 "
    }
}

pkg_order() {
    # Order a list of packages based on dependence and
    # take into account pre-built tarballs if this is
    # to be called from 'kiss i'.
    order=; redro=; deps=

    for pkg do case $pkg in
        *.tar.*) deps="$deps $pkg "  ;;
        *)       pkg_depends "$pkg" raw
    esac done

    # Filter the list, only keeping explicit packages.
    # The purpose of these two loops is to order the
    # argument list based on dependence.
    for pkg in $deps; do ! contains "$*" "$pkg" || {
        order="$order $pkg "
        redro=" $pkg $redro"
    } done

    deps=
}

pkg_strip() {
    # Strip package binaries and libraries. This saves space on the
    # system as well as on the tarballs we ship for installation.

    # Package has stripping disabled, stop here.
    [ -f "$mak_dir/$pkg/nostrip" ] && return

    log "$1" "Stripping binaries and libraries"

    # Strip only files matching the below ELF types.
    # NOTE: 'readelf' is used in place of 'file' as
    #       it allows us to remove 'file' from the
    #       core repositories altogether.
    find "$pkg_dir/$1" -type f | while read -r file; do
        case $(readelf -h "$file") in
            *" DYN "*)  strip_opt=unneeded ;;
            *" EXEC "*) strip_opt=all ;;
            *" REL "*)  strip_opt=debug ;;
            *) continue
        esac

        strip "--strip-$strip_opt" "$file" &&
        printf 'Stripped %10s %s\n' "($strip_opt)" "${file##$pkg_dir/$1}"
    done 2>/dev/null ||:
}

pkg_fixdeps() {
    # Dynamically look for missing runtime dependencies by checking
    # each binary and library with 'ldd'. This catches any extra
    # libraries and or dependencies pulled in by the package's
    # build suite.
    log "$1" "Checking for missing dependencies"

    # Go to the directory containing the built package to
    # simplify path building.
    cd "$pkg_dir/$1/$pkg_db/$1"

    # Make a copy of the depends file if it exists to have a
    # reference to 'diff' against.
    if [ -f depends ]; then
        cp -f depends "$mak_dir/d"
        dep_file=$mak_dir/d
    else
        dep_file=/dev/null
    fi

    # Generate a list of all installed manifests.
    pkg_name=$1
    set +f; set -f -- "$sys_db/"*/manifest

    # Get a list of binaries and libraries, false files
    # will be found, however it's faster to get 'ldd' to check
    # them anyway than to filter them out.
    find "$pkg_dir/$pkg_name/" -type f 2>/dev/null |

    while read -r file; do
        # Run 'ldd' on the file and parse each line. The code
        # then checks to see which packages own the linked
        # libraries and it prints the result.
        ldd "$file" 2>/dev/null | while read -r dep; do
            # Skip lines containing 'ldd'.
            [ "${dep##*ldd*}" ] || continue

            # Extract the file path from 'ldd' output, and
            # canonicalize the path.
            dep=${dep#* => }
            dep=${dep% *}
            dep=$(kiss-readlink "$dep")

            # Figure out which package owns the file.
            own=$("$grep" -lFx "${dep#$KISS_ROOT}" "$@")

            # If the package wasn't found, retry by removing
            # the '/usr' prefix.
            if [ -z "$own" ] && [ -z "${dep##$KISS_ROOT/usr*}" ]; then
                own=$("$grep" -lFx "${dep#$KISS_ROOT/usr}" "$@")
                dep=${dep#/usr}
            fi

            # Extract package name from 'grep' match.
            own=${own%/*}
            own=${own##*/}

            case $own in musl|gcc|"$pkg_name"|"") continue ; esac
            printf 'Found %s (%s) in (%s)\n' "$own" "$dep" \
                   "${file##$pkg_dir/$pkg_name}" >/dev/tty

            printf '%s\n' "$own"
        done ||:
    done >> depends

    # Remove duplicate entries from the new depends file.
    # This removes duplicate lines looking *only* at the
    # first column.
    sort -uk1,1 -o depends depends 2>/dev/null ||:

    # Display a diff of the new dependencies against the old ones.
    diff -U 3 "$dep_file" depends 2>/dev/null ||:

    # Remove the depends file if it is empty.
    [ -s depends ] || rm -f depends
}

pkg_manifest() (
    # Generate the package's manifest file. This is a list of each file
    # and directory inside the package. The file is used when uninstalling
    # packages, checking for package conflicts and for general debugging.
    log "$1" "Generating manifest"

    # This function runs as a sub-shell to avoid having to 'cd' back to the
    # prior directory before being able to continue.
    cd "${2:-$pkg_dir}/$1"

    # find: Print all files and directories and append '/' to directories.
    # sort: Sort the output in *reverse*. Directories appear *after* their
    #       contents.
    # sed:  Remove the first character in each line (./dir -> /dir) and
    #       remove all lines which only contain '.'.
    find . -type d -exec printf '%s/\n' {} + -o -print |
        sort -r | sed '/^\.\/$/d;ss.ss' > "${2:-$pkg_dir}/$1/$pkg_db/$1/manifest"
)

pkg_etcsums() (
    # This function runs as a sub-shell to avoid having to 'cd' back to the
    # prior directory before being able to continue.
    cd "$pkg_dir/$1/etc" 2>/dev/null || return 0; cd ..

    # Generate checksums for each configuration file in the package's
    # /etc/ directory for use in "smart" handling of these files.
    log "$1" "Generating etcsums"


    find etc -type f | while read -r file; do
        hashcheck "$file"
    done > "$pkg_dir/$1/$pkg_db/$1/etcsums"
)

pkg_tar() {
    # Create a tarball from the built package's files.
    # This tarball also contains the package's database entry.
    log "$1" "Creating tarball"

    # Read the version information to name the package.
    read -r version release < "$(pkg_find "$1")/version"

    # Create a tarball from the contents of the built package.
    "$tar" cf - -C "$pkg_dir/$1" . |
        case ${KISS_COMPRESS:=gz} in
            bz2) bzip2 -z ;;
            xz)  xz -zT 0 ;;
            gz)  gzip -6  ;;
            zst) zstd -3  ;;
            *)   gzip -6  ;;  # Fallback to gzip
        esac \
    > "$bin_dir/$1#$version-$release.tar.${KISS_COMPRESS:=gz}"

    log "$1" "Successfully created tarball"
}

pkg_build() {
    # Build packages and turn them into packaged tarballs. This function
    # also checks checksums, downloads sources and ensure all dependencies
    # are installed.
    pkg_build=1

    log "Resolving dependencies"

    for pkg do contains "$explicit" "$pkg" || {
        pkg_depends "$pkg" explicit

        # Mark packages passed on the command-line
        # separately from those detected as dependencies.
        explicit="$explicit $pkg "
    } done

    [ "$pkg_update" ] || explicit_build=$explicit

    # If an explicit package is a dependency of another explicit
    # package, remove it from the explicit list as it needs to be
    # installed as a dependency.
    # shellcheck disable=2086
    for pkg do
        contains "$deps" "$pkg" && explicit=$(pop "$pkg" from $explicit)
    done

    # See [1] at top of script.
    # shellcheck disable=2046,2086
    set -- $deps $explicit

    log "Building: $*"

    # Only ask for confirmation if more than one package needs to be built.
    [ $# -gt 1 ] || [ "$pkg_update" ] && { prompt || exit 0 ;}

    log "Checking for pre-built dependencies"

    for pkg do pkg_lint "$pkg"; done

    # Install any pre-built dependencies if they exist in the binary
    # directory and are up to date.
    for pkg do ! contains "$explicit_build" "$pkg" && pkg_cache "$pkg" && {
        log "$pkg" "Found pre-built binary, installing"
        (KISS_FORCE=1 args i "$tar_file")

        # Remove the now installed package from the build list.
        # See [1] at top of script.
        # shellcheck disable=2046,2086
        set -- $(pop "$pkg" from "$@")
    } done

    for pkg do pkg_sources "$pkg"; done

    pkg_verify "$@"

    # Finally build and create tarballs for all passed packages and
    # dependencies.
    for pkg do
        log "$pkg" "Building package ($((in = in + 1))/$#)"

        pkg_extract "$pkg"
        repo_dir=$(pkg_find "$pkg")

        # Install built packages to a directory under the package name
        # to avoid collisions with other packages.
        mkdir -p "$pkg_dir/$pkg/$pkg_db"

        # Move to the build directory.
        cd "$mak_dir/$pkg"

        log "$pkg" "Starting build"

        run_hook pre-build "$pkg" "$pkg_dir/$pkg"

        # Call the build script, log the output to the terminal
        # and to a file. There's no PIPEFAIL in POSIX shelll so
        # we must resort to tricks like killing the script ourselves.
        { "$repo_dir/build" "$pkg_dir/$pkg" 2>&1 || {
            log "$pkg" "Build failed"
            log "$pkg" "Log stored to $log_dir/$pkg-$time-$pid"
            run_hook build-fail "$pkg" "$pkg_dir/$pkg"
            pkg_clean
            kill 0
        } } | tee "$log_dir/$pkg-$time-$pid"

        # Delete the log file if the build succeeded to prevent
        # the directory from filling very quickly with useless logs.
        [ "$KISS_KEEPLOG" = 1 ] || rm -f "$log_dir/$pkg-$time-$pid"

        # Copy the repository files to the package directory.
        # This acts as the database entry.
        cp -LRf "$repo_dir" "$pkg_dir/$pkg/$pkg_db/"

        # We never ever want this. Let's end the endless conflicts
        # and remove it. This will be the only exception for a
        # specific removal of this kind.
        rm -f "$pkg_dir/$pkg/usr/lib/charset.alias"

        log "$pkg" "Successfully built package"

        run_hook post-build "$pkg" "$pkg_dir/$pkg"

        # Create the manifest file early and make it empty.
        # This ensures that the manifest is added to the manifest.
        : > "$pkg_dir/$pkg/$pkg_db/$pkg/manifest"

        # If the package contains '/etc', add a file called
        # 'etcsums' to the manifest. See comment directly above.
        [ -d "$pkg_dir/$pkg/etc" ] &&
            : > "$pkg_dir/$pkg/$pkg_db/$pkg/etcsums"

        pkg_strip    "$pkg"
        pkg_fixdeps  "$pkg"
        pkg_manifest "$pkg"
        pkg_etcsums  "$pkg"
        pkg_tar      "$pkg"

        # Install only dependencies of passed packages.
        # Skip this check if this is a package update.
        contains "$explicit" "$pkg" && [ -z "$pkg_update" ] && continue

        log "$pkg" "Needed as a dependency or has an update, installing"

        (KISS_FORCE=1 args i "$pkg")
    done

    # End here as this was a system update and all packages have been installed.
    [ "$pkg_update" ] && return

    log "Successfully built package(s)"

    # Turn the explicit packages into a 'list'.
    # See [1] at top of script.
    # shellcheck disable=2046,2086
    set -- $explicit

    # Only ask for confirmation if more than one package needs to be installed.
    [ $# -gt 1 ] && prompt "Install built packages? [$*]" && {
        args i "$@"
        return
    }

    log "Run 'kiss i $*' to install the package(s)"
}

pkg_checksums() {
    # Generate checksums for packages.
    repo_dir=$(pkg_find "$1")

    while read -r src _ || [ "$src" ]; do
        # Comment.
        if [ -z "${src##\#*}" ]; then
            continue

        # File is local to the package.
        elif [ -f "$repo_dir/$src" ]; then
            src_path=$repo_dir/${src%/*}

        # File is remote and was downloaded.
        elif [ -f "$src_dir/$1/${src##*/}" ]; then
            src_path=$src_dir/$1

        # File is a git repository.
        elif [ -z "${src##git+*}" ]; then
            printf 'git  %s\n' "$src"
            continue

        # Die here if source for some reason, doesn't exist.
        else
            die "$1" "Couldn't find source '$src'"
        fi

        # An easy way to get 'sha256sum' to print with the 'basename'
        # of files is to 'cd' to the file's directory beforehand.
        (cd "$src_path" && hashcheck "${src##*/}") ||
            die "$1" "Failed to generate checksums"
    done < "$repo_dir/sources"
}

pkg_verify() {
    # Verify all package checksums. This is achieved by generating
    # a new set of checksums and then comparing those with the old
    # set.
    for pkg do pkg_checksums "$pkg" | cmp - "$(pkg_find "$pkg")/checksums" || {
        log "$pkg" "Checksum mismatch"

        # Instead of dying above, log it to the terminal. Also define a
        # variable so we *can* die after all checksum files have been
        # checked.
        mismatch="$mismatch$pkg "
    } done

    [ -z "$mismatch" ] || die "Checksum mismatch with: ${mismatch% }"
}

pkg_conflicts() {
    # Check to see if a package conflicts with another.
    log "$1" "Checking for package conflicts"

    # Filter the tarball's manifest and select only files
    # and any files they resolve to on the filesystem
    # (/bin/ls -> /usr/bin/ls).
    while read -r file; do
        case $file in */) continue; esac

        printf '%s/%s\n' \
            "$(kiss-readlink "$KISS_ROOT/${file%/*}" 2>/dev/null)" \
            "${file##*/}"
    done < "$tar_dir/$1/$pkg_db/$1/manifest" > "$KISS_TMPDIR/$pid-m"

    p_name=$1

    # Generate a list of all installed package manifests
    # and remove the current package from the list.
    # shellcheck disable=2046,2086
    set -- $(set +f; pop "$sys_db/$p_name/manifest" from "$sys_db"/*/manifest)

    [ -s "$KISS_TMPDIR/$pid-m" ] || return 0

    # In rare cases where the system only has one package installed
    # and you are reinstalling that package, grep will try to read from
    # standard input if we continue here.
    #
    # Also, if we don't have any packages installed grep will give an
    # error. This will not cause the installation to fail, but we don't
    # need to check for conflicts if that's the case anyway. If we have
    # only zero packages or one package, just stop wasting time and continue
    # with the installation.
    [ "$1" ] && [ -f "$1" ] || return 0

    # Store the list of found conflicts in a file as we will be using the
    # information multiple times. Storing it in the cache dir allows us
    # to be lazy as they'll be automatically removed on script end.
    "$grep" -Fxf "$KISS_TMPDIR/$pid-m" -- "$@" > "$KISS_TMPDIR/$pid-c" ||:


    # Enable alternatives automatically if it is safe to do so.
    # This checks to see that the package that is about to be installed
    # doesn't overwrite anything it shouldn't in '/var/db/kiss/installed'.
    "$grep" -q ":/var/db/kiss/installed/" "$KISS_TMPDIR/$pid-c" || choice_auto=1

    # Use 'grep' to list matching lines between the to
    # be installed package's manifest and the above filtered
    # list.
    if [ "$KISS_CHOICE" != 0 ] && [ "$choice_auto" = 1 ]; then

        # This is a novel way of offering an "alternatives" system.
        # It is entirely dynamic and all "choices" are created and
        # destroyed on the fly.
        #
        # When a conflict is found between two packages, the file
        # is moved to a directory called "choices" and its name
        # changed to store its parent package and its intended
        # location.
        #
        # The package's manifest is then updated to reflect this
        # new location.
        #
        # The 'kiss choices' command parses this directory and
        # offers you the CHOICE of *swapping* entries in this
        # directory for those on the filesystem.
        #
        # The choices command does the same thing we do here,
        # it rewrites manifests and moves files around to make
        # this work.
        #
        # Pretty nifty huh?
        while IFS=: read -r _ con; do
            printf '%s\n' "Found conflict $con"

            # Create the "choices" directory inside of the tarball.
            # This directory will store the conflicting file.
            mkdir -p "$tar_dir/$p_name/${cho_dir:=var/db/kiss/choices}"

            # Construct the file name of the "db" entry of the
            # conflicting file. (pkg_name>usr>bin>ls)
            con_name=$(printf %s "$con" | sed 's|/|>|g')

            # Move the conflicting file to the choices directory
            # and name it according to the format above.
            mv -f "$tar_dir/$p_name/$con" \
                  "$tar_dir/$p_name/$cho_dir/$p_name$con_name" 2>/dev/null || {
                log "File must be in ${con%/*} and not a symlink to it"
                log "This usually occurs when a binary is installed to"
                log "/sbin instead of /usr/bin (example)"
                log "Before this package can be used as an alternative,"
                log "this must be fixed in $p_name. Contact the maintainer"
                die "by checking 'git log' or by running 'kiss-maintainer'"
            }
        done < "$KISS_TMPDIR/$pid-c"

        # Rewrite the package's manifest to update its location
        # to its new spot (and name) in the choices directory.
        pkg_manifest "$p_name" "$tar_dir" 2>/dev/null

    elif [ -s "$KISS_TMPDIR/$pid-c" ]; then
        log "Package '$p_name' conflicts with another package" "" "!>"
        log "Run 'KISS_CHOICE=1 kiss i $p_name' to add conflicts" "" "!>"
        die "as alternatives."
    fi
}

pkg_swap() {
    # Swap between package alternatives.
    pkg_list "$1" >/dev/null

    alt=$(printf %s "$1$2" | sed 's|/|>|g')
    cd "$sys_db/../choices"

    [ -f "$alt" ] || [ -h "$alt" ] ||
        die "Alternative '$1 $2' doesn't exist"

    if [ -f "$2" ]; then
        # Figure out which package owns the file we are going to
        # swap for another package's.
        #
        # Print the full path to the manifest file which contains
        # the match to our search.
        pkg_owns=$(set +f; "$grep" -lFx "$2" "$sys_db/"*/manifest) ||:

        # Extract the package name from the path above.
        pkg_owns=${pkg_owns%/*}
        pkg_owns=${pkg_owns##*/}

        [ "$pkg_owns" ] ||
            die "File '$2' exists on filesystem but isn't owned"

        log "Swapping '$2' from '$pkg_owns' to '$1'"

        # Convert the current owner to an alternative and rewrite
        # its manifest file to reflect this. We then resort this file
        # so no issues arise when removing packages.
        cp  -Pf "$2" "$pkg_owns>${alt#*>}"
        sed "s#^$2#$PWD/$pkg_owns>${alt#*>}#" \
            "../installed/$pkg_owns/manifest" |
            sort -r -o "../installed/$pkg_owns/manifest"
    fi

    # Convert the desired alternative to a real file and rewrite
    # the manifest file to reflect this. The reverse of above.
    mv  -f "$alt" "$2"
    sed "s#^$PWD/$alt#$2#" "../installed/$1/manifest" |
        sort -r -o "../installed/$1/manifest"
}

pkg_etc() {
    [ -d "$tar_dir/$pkg_name/etc" ] || return 0

    (cd "$tar_dir/$pkg_name"

    # Create all directories beforehand.
    find etc -type d | while read -r dir; do
        mkdir -p "$KISS_ROOT/$dir"
    done

    # Handle files in /etc/ based on a 3-way checksum check.
    find etc ! -type d | while read -r file; do
        { sum_new=$(hashcheck "$file")
          sum_sys=$(cd "$KISS_ROOT/"; hashcheck "$file")
          sum_old=$("$grep" "$file$" "$mak_dir/c"); } 2>/dev/null ||:

        log "$pkg_name" "Doing 3-way handshake for $file"
        printf '%s\n' "Previous: ${sum_old:-null}"
        printf '%s\n' "System:   ${sum_sys:-null}"
        printf '%s\n' "New:      ${sum_new:-null}"

        # Use a case statement to easily compare three strings at
        # the same time. Pretty nifty.
        case ${sum_old:-null}${sum_sys:-null}${sum_new} in
            # old = Y, sys = X, new = Y
            "${sum_new}${sum_sys}${sum_old}")
                log "Skipping $file"
                continue
            ;;

            # old = X, sys = X, new = X
            # old = X, sys = Y, new = Y
            # old = X, sys = X, new = Y
            "${sum_old}${sum_old}${sum_old}"|\
            "${sum_old:-null}${sum_sys}${sum_sys}"|\
            "${sum_sys}${sum_old}"*)
                log "Installing $file"
                new=
            ;;

            # All other cases.
            *)
                warn "($pkg_name) saving /$file as /$file.new" "->"
                new=.new
            ;;
        esac

        cp -fPp "$file"  "$KISS_ROOT/${file}${new}"
        chown root:root "$KISS_ROOT/${file}${new}" 2>/dev/null
    done) ||:
}

pkg_remove() {
    # Remove a package and all of its files. The '/etc' directory
    # is handled differently and configuration files are *not*
    # overwritten.
    pkg_list "$1" >/dev/null || return

    set +f

    # Make sure that nothing depends on this package.
    [ "$2" = check ] && for file in "$sys_db/"*; do
        # Check each depends file for the package and if it's
        # a run-time dependency, append to the $required_by string.
        "$grep" -qFx "$1" "$file/depends" 2>/dev/null &&
            required_by="$required_by'${file##*/}', "
    done

    [ "$required_by" ] &&
        die "$1" "Package is required by ${required_by%, }"

    set -f

    # Block being able to abort the script with 'Ctrl+C' during removal.
    # Removes all risk of the user aborting a package removal leaving
    # an incomplete package installed.
    trap '' INT

    if [ -x "$sys_db/$1/pre-remove" ]; then
        log "$1" "Running pre-remove script"
        "$sys_db/$1/pre-remove" ||:
    fi

    while read -r file; do
        # The file is in '/etc' skip it. This prevents the package
        # manager from removing user edited configuration files.
        [ "${file##/etc/*}" ] || continue

        if [ -d "$KISS_ROOT/$file" ]; then
            rmdir "$KISS_ROOT/$file" 2>/dev/null || continue
        else
            rm -f "$KISS_ROOT/$file"
        fi
    done < "$sys_db/$1/manifest"

    # Reset 'trap' to its original value. Removal is done so
    # we no longer need to block 'Ctrl+C'.
    trap pkg_clean EXIT INT

    log "$1" "Removed successfully"
}

pkg_install() {
    # Install a built package tarball.

    # Install can also take the full path to a tarball.
    # We don't need to check the repository if this is the case.
    if [ -f "$1" ] && [ -z "${1%%*.tar*}" ] ; then
        tar_file=$1
        pkg_name=${1##*/}
        pkg_name=${pkg_name%#*}

    else
        pkg_cache "$1" ||
            die "package has not been built, run 'kiss b pkg'"

        pkg_name=$1
    fi

    mkdir -p "$tar_dir/$pkg_name"
    log "$pkg_name" "Extracting $tar_file"

    # Extract the tarball to catch any errors before installation begins.
    decompress "$tar_file" | "$tar" xf - -C "$tar_dir/$pkg_name"

    [ -f "$tar_dir/$pkg_name/$pkg_db/$pkg_name/manifest" ] ||
        die "'${tar_file##*/}' is not a valid KISS package"

    # Ensure that the tarball's manifest is correct by checking that
    # each file and directory inside of it actually exists.
    [ -z "$KISS_FORCE" ] && log "$pkg_name" "Checking package manifest" &&
        while read -r line; do
            # Skip symbolic links
            [ -h "$tar_dir/$pkg_name/$line" ] ||
            [ -e "$tar_dir/$pkg_name/$line" ] || {
        log "File $line missing from tarball but mentioned in manifest" "" "!>"
        TARBALL_FAIL=1
        }
    done < "$tar_dir/$pkg_name/$pkg_db/$pkg_name/manifest"
    [ "$TARBALL_FAIL" ] && {
        log "You can still install this package by setting KISS_FORCE variable"
        die "$pkg_name" "Missing files in manifest"
    }

    log "$pkg_name" "Checking that all dependencies are installed"

    # Make sure that all run-time dependencies are installed prior to
    # installing the package.
    [ -f "$tar_dir/$pkg_name/$pkg_db/$pkg_name/depends" ] &&
    [ -z "$KISS_FORCE" ] &&
        while read -r dep dep_type || [ "$dep" ]; do
            [ "${dep##\#*}" ] || continue
            [ "$dep_type" ]   || pkg_list "$dep" >/dev/null ||
                install_dep="$install_dep'$dep', "
        done < "$tar_dir/$pkg_name/$pkg_db/$pkg_name/depends"

    [ "$install_dep" ] && die "$1" "Package requires ${install_dep%, }"

    run_hook pre-install "$pkg_name" "$tar_dir/$pkg_name"

    pkg_conflicts "$pkg_name"

    log "$pkg_name" "Installing package incrementally"

    # Block being able to abort the script with Ctrl+C during installation.
    # Removes all risk of the user aborting a package installation leaving
    # an incomplete package installed.
    trap '' INT

    # If the package is already installed (and this is an upgrade) make a
    # backup of the manifest and etcsums files.
    cp -f "$sys_db/$pkg_name/manifest" "$mak_dir/m" 2>/dev/null ||:
    cp -f "$sys_db/$pkg_name/etcsums"  "$mak_dir/c" 2>/dev/null ||:

    # This is repeated multiple times. Better to make it a function.
    pkg_rsync() {
        rsync --chown=root:root --chmod=Du-s,Dg-s,Do-s \
              -WhHKa --no-compress --exclude /etc "${1:---}" \
              "$tar_dir/$pkg_name/" "$KISS_ROOT/"
    }

    # Install the package by using 'rsync' and overwrite any existing files
    # (excluding '/etc/').
    pkg_rsync --info=progress2
    pkg_etc

    # Remove any leftover files if this is an upgrade.
    "$grep" -vFxf "$sys_db/$pkg_name/manifest" "$mak_dir/m" 2>/dev/null |

    while read -r file; do
        file=$KISS_ROOT/$file

        # Skip deleting some leftover files.
        case $file in /etc/*) continue; esac

        # Remove files.
        if [ -f "$file" ] && [ ! -L "$file" ]; then
            rm -f "$file"

        # Remove file symlinks.
        elif [ -h "$file" ] && [ ! -d "$file" ]; then
            unlink "$file" ||:

        # Skip directory symlinks.
        elif [ -h "$file" ] && [ -d "$file" ]; then :

        # Remove directories if empty.
        elif [ -d "$file" ]; then
            rmdir "$file" 2>/dev/null ||:
        fi
    done ||:

    log "$pkg_name" "Verifying installation"
    { pkg_rsync; pkg_rsync; } ||:

    # Reset 'trap' to its original value. Installation is done so
    # we no longer need to block 'Ctrl+C'.
    trap pkg_clean EXIT INT

    if [ -x "$sys_db/$pkg_name/post-install" ]; then
        log "$pkg_name" "Running post-install script"
        "$sys_db/$pkg_name/post-install" ||:
    fi

    run_hook post-install "$pkg_name" "$sys_db/$pkg_name"

    log "$pkg_name" "Installed successfully"
}

pkg_fetch() {
    log "Updating repositories"

    # Create a list of all repositories.
    # See [1] at top of script.
    # shellcheck disable=2046,2086
    { IFS=:; set -- $KISS_PATH; unset IFS; }

    # Update each repository in '$KISS_PATH'. It is assumed that
    # each repository is 'git' tracked.
    for repo do
        # Go to the root of the repository (if it exists).
        cd "$repo"
        cd "$(git rev-parse --show-toplevel 2>/dev/null)" 2>/dev/null ||:

        [ -d .git ] || {
            log "$repo" " "
            printf '%s\n' "Not a git repository, skipping."
            continue
        }

        [ "$(git remote 2>/dev/null)" ] || {
            log "$repo" " "
            printf '%s\n' "No remote, skipping."
            continue
        }

        contains "$repos" "$PWD" || {
            repos="$repos $PWD "

            # Display a tick if signing is enabled for this
            # repository.
            case $(git config merge.verifySignatures) in
                true) log "$PWD" "[signed ✓] " ;;
                *)    log "$PWD" " " ;;
            esac

            if [ -w "$PWD" ] && [ "$uid" != 0 ]; then
                git fetch
                git merge
                ! [ -e .gitmodules ] || {
                    git submodule init
                    git submodule update
                }

            else
                [ "$uid" = 0 ] || log "$PWD" "Need root to update"

                # Find out the owner of the repository and spawn
                # git as this user below.
                #
                # This prevents 'git' from changing the original
                # ownership of files and directories in the rare
                # case that the repository is owned by a 3rd user.
                (
                    user=$(kiss-stat "$PWD") || user=root

                    id -u "$user" >/dev/null 2>&1 ||
                        user=root

                    [ "$user" = root ] ||
                        log "Dropping permissions to $user for pull"

                    case $su in
                        su) "$su" -c "git fetch && git merge && { ! [ -e .gitmodules ] || { git submodule init ; git submodule update ;} ;}" "$user" ;;
                         *) "$su" -u "$user" git fetch
                            "$su" -u "$user" git merge
                            ! [ -e .gitmodules ] || {
                                "$su" -u "$user" git submodule init
                                "$su" -u "$user" git submodule update
                            }
                    esac
                )
            fi
        }
    done
}

pkg_updates(){
    # Check all installed packages for updates. So long as the installed
    # version and the version in the repositories differ, it's considered
    # an update.
    pkg_fetch

    log "Checking for new package versions"

    set +f

    for pkg in "$sys_db/"*; do
        pkg_name=${pkg##*/}

        # Read version and release information from the installed packages
        # and repository.
        read -r db_ver db_rel < "$pkg/version"
        read -r re_ver re_rel < "$(pkg_find "$pkg_name")/version"

        # Compare installed packages to repository packages.
        [ "$db_ver-$db_rel" != "$re_ver-$re_rel" ] && {
            printf '%s\n' "$pkg_name $db_ver-$db_rel ==> $re_ver-$re_rel"
            outdated="$outdated$pkg_name "
        }
    done

    set -f

    # If the download option is specified only download the outdated packages
    # and exit.
    [ "$download" ] && {
        for pkg in $outdated; do
            pkg_sources "$pkg"
        done

        exit 0
    }

    contains "$outdated" kiss && {
        log "Detected package manager update"
        log "The package manager will be updated first"

        prompt || exit 0

        pkg_build kiss
        args i kiss

        log "Updated the package manager"
        log "Re-run 'kiss update' to update your system"

        exit 0
    }

    [ "$outdated" ] || {
        log "Everything is up to date"
        return
    }

    log "Packages to update: ${outdated% }"

    # Tell 'pkg_build' to always prompt before build.
    pkg_update=1

    # Build all packages requiring an update.
    # See [1] at top of script.
    # shellcheck disable=2046,2086
    {
        pkg_order $outdated
        pkg_build $order
    }

    log "Updated all packages"
}

pkg_clean() {
    # Clean up on exit or error. This removes everything related
    # to the build.
    [ "$KISS_DEBUG" != 1 ] || return

    # Block 'Ctrl+C' while cache is being cleaned.
    trap '' INT

    # Remove temporary items.
    rm -rf -- "$mak_dir" "$pkg_dir" "$tar_dir" \
       "$KISS_TMPDIR/$pid-c" "$KISS_TMPDIR/$pid-m"
}

args() {
    # Parse script arguments manually. This is rather easy to do in
    # our case since the first argument is always an "action" and
    # the arguments that follow are all package names.
    action=$1

    # 'dash' gives an error when shift is used without any arguments.
    [ "$1" ] && shift

    # Unless this is a search, sanitize the user's input. The call to
    # 'pkg_find()' supports basic globbing, ensure input doesn't expand
    # to anything except for when this behavior is needed.
    #
    # This handles the globbing characters '*', '!', '[' and ']' as per:
    # https://pubs.opengroup.org/onlinepubs/009695399/utilities/xcu_chap02.html
    [ "${action##[as]*}" ] &&
        case $* in *\**|*\!*|*\[*|*\]*)
            die "Arguments contain invalid characters: '!*[]'"
        esac

    # Parse some arguments earlier to remove the need to duplicate code.
    case $action in
        s|search)
            [ "$1" ] || die "'kiss $action' requires an argument"
        ;;

        a|alternatives)
            # Rerun the script with 'su' if the user isn't root.
            # Cheeky but 'su' can't be used on shell functions themselves.
            [ -z "$1" ] || [ "$uid" = 0 ] || {
                as_root "$0" "$action" "$@"
                return
            }
        ;;

        i|install|r|remove)
            # Rerun the script with 'su' if the user isn't root.
            # Cheeky but 'su' can't be used on shell functions themselves.
            [ "$uid" = 0 ] || {
                KISS_FORCE="$KISS_FORCE" as_root "$0" "$action" "$@"
                return
            }
        ;;
    esac

    case $action in
        b|build|c|checksum|i|install|r|remove)
            [ "$1" ] || {
                # We are exporting the KISS_PATH, so if another
                # instance of 'kiss' is spawned from the current
                # one, they continue to use the same KISS_PATH
                export KISS_PATH="${PWD%/*}:$KISS_PATH"
                set -- "${PWD##*/}"
            } ; esac

    # Actions can be abbreviated to their first letter. This saves
    # keystrokes once you memorize the commands.
    #
    # This is to fix a shellcheck warning when using $PATH
    # in kiss extensions help string.
    # shellcheck disable=2016
    case $action in
        a|alternatives)
            if [ "$1" = - ]; then
                while read -r pkg path; do
                    pkg_swap "$pkg" "$path"
                done

            elif [ "$1" ]; then
                pkg_swap "$@"

            else
                # Go over each alternative and format the file
                # name for listing. (pkg_name>usr>bin>ls)
                set +f; for pkg in "$sys_db/../choices"/*; do
                    printf '%s\n' "${pkg##*/}"
                done | sed 's|>| /|; s|>|/|g; /\*/d'
            fi
        ;;

        c|checksum)
            for pkg do pkg_lint    "$pkg" c; done
            for pkg do pkg_sources "$pkg" c; done
            for pkg do
                pkg_checksums "$pkg" | {
                    repo_dir=$(pkg_find "$pkg")

                    if [ -w "$repo_dir" ]; then
                        tee "$repo_dir/checksums"
                    else
                        log "$pkg" "Need permissions to generate checksums"

                        user=$(kiss-stat "$repo_dir") as_root tee "$repo_dir/checksums"
                    fi
                }

                log "$pkg" "Generated checksums"
            done
        ;;

        f|fetch) pkg_fetch ;;

        i|install)
            pkg_order "$@"

            for pkg in $order; do pkg_install "$pkg"; done

            # After installation is complete, show a list
            # of messages from packages.
            log "Retrieving post-installation message queue"
            unset msg

            for pkg in $order; do
                if [ -f "$sys_db/$pkg/message" ]; then
                    printf '%s\n%b%s%b\n%s\n\n' \
                           "==============================" \
                           "${color:+"\033[1m"}" "$pkg" "${color:+"\033[m"}" \
                           "==============================" >&2
                    cat "$sys_db/$pkg/message" >&2
                    msg=1
                fi
                [ "$msg" ] || log "No message in queue"
            done
        ;;

        e|extension)
            exec 2>&1

            log "Installed extensions"
            set --

            for path in $(SEARCH_PATH=$PATH pkg_find kiss-* all -x); do
                set -- "${path#*/kiss-}" "$@"
                max=$((${#1} > max ? ${#1} : max))
             done

            for path do
                # These are binary files so they should be ignored
                contains "readlink stat" "$path" && continue

                printf '%b->%b %-*s  ' "${color:+"\033[1;31m"}" "${color:+"\033[m"}" \
                    "$max" "${path#*/kiss-}"
                sed -n 's/^# *//;2p' "$(command -v "kiss-$path")"
             done | sort -uk1 >&2

        ;;

        r|remove)
            pkg_order "$@"

            for pkg in $redro; do
                pkg_remove "$pkg" "${KISS_FORCE:-check}"
            done
        ;;

        d|download)
            # If no arguments are given, download the sources
            # for outdated packages.
            [ "$1" ] || { download=1; pkg_updates ;}

            # Acquire sources for all given packages.
            for pkg do pkg_sources "$pkg"; done
        ;;

        b|build)    pkg_build "${@:?No packages installed}" ;;
        l|list)     pkg_list "$@" ;;
        u|update)   pkg_updates ;;
        s|search)   for pkg do pkg_find "$pkg" all; done ;;
        v|version)  log kiss 1.21.1 ;;

        h|help|-h|--help|'')
            exec 2>&1
            log 'kiss [a|b|c|d|e|f|i|l|r|s|u|v] [pkg] [pkg] [pkg]'
            log 'alternatives  List and swap to alternatives'
            log 'build         Build a package'
            log 'checksum      Generate checksums'
            log 'download      Download sources for the given package'
            log 'extension     List available kiss extensions (kiss-* in $PATH)'
            log 'fetch         Fetch repositories'
            log 'install       Install a package'
            log 'list          List installed packages'
            log 'remove        Remove a package'
            log 'search        Search for a package'
            log 'update        Check for updates'
            log 'version       Package manager version'

        ;;

        *)
             util=$(SEARCH_PATH=$PATH pkg_find "kiss-$action"* "" -x 2>/dev/null) ||
                 die "'kiss $action' is not a valid command"

              "$util" "$@"
         ;;

    esac
}

main() {
    # Die here if the user has no set KISS_PATH. This is a rare occurance
    # as the environment variable should always be defined.
    [ "$KISS_PATH" ] || die "\$KISS_PATH needs to be set"

    # Set the location to the repository and package database.
    pkg_db=var/db/kiss/installed

    # The PID of the current shell process is used to isolate directories
    # to each specific KISS instance. This allows multiple package manager
    # instances to be run at once. Store the value in another variable so
    # that it doesn't change beneath us.
    pid=${KISS_PID:-$$}

    # Force the C locale to speed up things like 'grep' which disable unicode
    # etc when this is set. We don't need unicode and a speed up is always
    # welcome.
    export LC_ALL=C LANG=C

    # Catch errors and ensure that build files and directories are cleaned
    # up before we die. This occurs on 'Ctrl+C' as well as success and error.
    trap pkg_clean EXIT INT

    # Prefer GNU grep if installed as it is much much faster than busybox's
    # implementation. Very much worth it if you value performance over
    # POSIX correctness (grep quoted to avoid shellcheck false-positive).
    grep=$(command -v ggrep) || grep='grep'

    # Prefer libarchive tar or GNU tar if installed as they are  much
    # much faster than busybox's implementation. Very much worth it if
    # you value performance.
    tar=$(command -v bsdtar || command -v gtar) || tar=tar

    # Figure out which 'sudo' command to use based on the user's choice or
    # what is available on the system.
    su=${KISS_SU:-$(command -v sudo || command -v doas)} || su=su

    # Store the date and time of script invocation to be used as the name
    # of the log files the package manager creates uring builds.
    time=$(date '+%Y-%m-%d-%H:%M')

    # Make note of the user's current ID to do root checks later on.
    # This is used enough to warrant a place here.
    uid=$(id -u)

    # Make sure that the KISS_ROOT doesn't end with a '/'. This might
    # break some operations.
    [ -z "$KISS_ROOT" ] || [ "${KISS_ROOT##*/}" ] || {
        warn "Your KISS_ROOT variable shouldn't end with '/'"
        KISS_ROOT=${KISS_ROOT%/}
    }

    # Define this variable but don't create its directory structure from
    # the get go. It will be created as needed by package installation.
    sys_db=$KISS_ROOT/$pkg_db

    # This allows for automatic setup of a KISS chroot and will
    # do nothing on a normal system.
    mkdir -p "$KISS_ROOT/" 2>/dev/null ||:

    # A temporary directory can be specified apart from the cache
    # directory in order to build in a user specified directory.
    # /tmp could be used in order to build on ram, useful on SSDs.
    # The user can specify KISS_TMPDIR for this.
    #
    # Create the required temporary directories and set the variables
    # which point to them.
    mkdir -p "${cac_dir:=${XDG_CACHE_HOME:-$HOME/.cache}/kiss}" \
             "${KISS_TMPDIR:=$cac_dir}" \
             "${mak_dir:=$KISS_TMPDIR/build-$pid}" \
             "${pkg_dir:=$KISS_TMPDIR/pkg-$pid}" \
             "${tar_dir:=$KISS_TMPDIR/extract-$pid}" \
             "${src_dir:=$cac_dir/sources}" \
             "${log_dir:=$cac_dir/logs}" \
             "${bin_dir:=$cac_dir/bin}"

    # Disable color escape sequences if running in a subshell.
    # This behaviour can be changed by adding a KISS_COLOR
    # variable to the environment. If it is set to 1 it will
    # always enable color escapes, and if set to 0 it will
    # always disable color escapes.
    if [ "$KISS_COLOR" = 1 ]; then color=1
    elif [ "$KISS_COLOR" = 0 ] || ! [ -t 1 ]; then
        log() { printf '%s %s %s\n' "${3:-->}" "$1" "$2" >&2 ;}
    else color=1
    fi

    args "$@"
}

main "$@"