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#!/bin/bash

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# vim: set ft=sh :

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#

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# Dependency-based updates + utils

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## Compare the given output file with all given source files:

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#

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#   check_update $out ${deps[@]} && do_update $out ... || ...

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#

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# Returns true if the output file needs to be updated.

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function check_update {

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    # target

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    local out="$1"; shift

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    debug "$out"

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    # need update?

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    local update=

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    if [ ${#@} == 0 ]; then

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        debug "  update: unknown deps"

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        update=y

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    elif [ ! -e "$out" ]; then

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        debug "  update: dest missing"

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        update=y

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    elif [ $UPDATE_FORCE ]; then

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        debug "  update: forced"

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        update=y

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    fi

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    # check deps

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    for dep in "$@"; do

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        # don't bother checking if already figured out

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        [ $update ] && continue

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        # check

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        if [ ! -e "$dep" ]; then

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            warn "$out: Missing source: $dep"

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        elif [ "$out" -ot "$dep" ]; then

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            debug "  update: $dep"

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            update=y

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        else

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            debug "  check: $dep"

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        fi

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    done

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    [ ! $update ] && debug "  up-to-date"

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    # return

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    [ $update ]

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}

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## Generate updated output file from given command's stdout:

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#

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#   do_update $out $BIN/cmd --args

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#

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# Writes output to a temporary .new file, optionally shows a diff of changes, and commits

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# the new version to $out (unless noop'd).

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function do_update {

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    local out="$1"; shift

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    local tmp="$out.new"

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    debug "$out"

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    cmd "$@" > "$tmp"

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    # compare

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    if [ -e "$out" ] && [ $UPDATE_DIFF ]; then

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        debug "  changes:"

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        # terse

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        indent "        " diff --unified=1 "$out" "$tmp" || true

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    fi

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    # deploy

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    if [ $UPDATE_NOOP ]; then

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        # cleanup

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        debug "  no-op"

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        cmd rm "$tmp"

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    else

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        # commit

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        debug "  deploy"

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        cmd mv "$tmp" "$out"

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    fi

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}

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## Compare symlink to target:

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#

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#   check_link $lnk $tgt && do_link $lnk $tgt || ...

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#

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# Tests if the symlink exists, and the target matches.

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# Fails if the target does not exist.

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function check_link {

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    local lnk="$1"

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    local tgt="$2"

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    [ ! -e "$tgt" ] && fail "$tgt: target does not exist"

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    [ ! -e "$lnk" ] || [ $(readlink "$lnk") != "$tgt" ]

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}

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## Update symlink to point to target:

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#

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#   do_link $lnk $tgt

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#

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function do_link {

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    local lnk="$1"

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    local tgt="$2"

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    cmd ln -sf "$tgt" "$lnk"

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}

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## Read include paths from file

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function read_zone_includes {

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    cmd sed -n -E 's/^\$INCLUDE\s+"(.+)"/\1/p' "$@"

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}

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## (cached) include paths for zone file

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function zone_includes {

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    local cache="$1"

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    local src="$2"

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    local prefix="${3:-}"

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    if [ ! -e "$cache" -o "$cache" -ot "$src" ]; then

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        read_zone_includes "$src" > "$cache"

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    fi

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    while read include; do

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        echo -n "$prefix$include "

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    done < "$cache"

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}

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## Search for prefix-matching includes in zone file

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function zone_includes_grep {

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    local cache="$1"

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    local src="$2"

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    local prefix="$3"

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    for include in $(zone_includes $cache $src); do

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        if [ "${include#$prefix}" != "$include" ]; then

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            echo -n " ${include#$prefix}"

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        fi

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    done

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}