json.sh

# scenario: want to make this json data structure from a shell script (and store it in a variable):
# 
# "menuitem": [
#       {"value": "New", "onclick": "CreateNewDoc()"},
#       {"value": "Open", "onclick": "OpenDoc()"},
#       {"value": "Close", "onclick": "CloseDoc()"}
#     ]


function newBuilder {
    echo
}
function newList {
    echo
}


function set {
    INPUT=$(cat -)
    FIELD=$1
    VALUE=$2

    if [[ $INPUT != "" ]]; then
        echo -n ${INPUT},
    fi
    echo -n '"'$FIELD'":'$VALUE
}

function setOrClear {
    INPUT=$(cat -)
    FIELD=$1
    VALUE=$2

    if [[ $VALUE != "" && $VALUE != "\"\"" ]]; then
        echo -n ${INPUT} | set $FIELD $VALUE
    else
        echo -n ${INPUT}
    fi
}

function add {
    INPUT=$(cat -)
    THING=$1

    if [[ $INPUT != "" ]]; then
        echo -n ${INPUT},
    fi
    echo -n $THING
}

function quoted {
    THING=$1
    echo -n '"'$THING'"'
}

function buildList {
    INPUT=$(cat -)
    echo -n "[$INPUT]"
}

function build {
    INPUT=$(cat -)
    echo -n "{$INPUT}"
}

MENUITEMS=$(newList \
    | add $(newBuilder \
        | set value $(quoted New) \
        | set onclick $(quoted CreateNewDoc\(\)) \
        | build) \
    | add $(newBuilder \
        | set value $(quoted Open) \
        | set onclick $(quoted OpenDoc\(\)) \
        | build) \
    | add $(newBuilder \
        | set value $(quoted Close) \
        | set onclick $(quoted CloseDoc\(\)) \
        | build) \
    | buildList)

function mkList {
    mktemp /tmp/XXXX
}
function appendList {
    LISTFILE=$1
    ELEMENT=$2
    
    cat ${LISTFILE} | add ${ELEMENT} > ${LISTFILE}.new
    mv ${LISTFILE}.new ${LISTFILE}
}
function finishList {
    LISTFILE=$1
    cat ${LISTFILE} | buildList > ${LISTFILE}.new
    mv ${LISTFILE}.new ${LISTFILE}
    OUT=$(cat ${LISTFILE})
    rm $LISTFILE
    echo $OUT
}

cat > map << EOF
New CreateNewDoc
Open OpenDoc
Close CloseDoc
EOF

LIST=$(mkList)
for fn in New Open Close; do
    # pretend this is arbitrary logic:
    click=$(grep $fn map | cut -d' ' -f 2)
    
    appendList $LIST $(newBuilder \
        | set value $(quoted $fn) \
        | set onclick $(quoted $click\(\)) \
        | build)
done
MENUITEMSLOOP=$(finishList $LIST)

function newAction {
    fn=$1
    click=$2
    newBuilder \
        | set value $(quoted $fn) \
        | set onclick $(quoted $click\(\)) \
        | build
}

MENUITEMSCONCISE=$(newList \
    | add $(newAction New CreateNewDoc) \
    | add $(newAction Open OpenDoc) \
    | add $(newAction Close CloseDoc) \
    | buildList)

EMPTY=
POPULATED="populated"
testy1=$(newBuilder \
    | setOrClear field1 $(quoted ${POPULATED}) \
    | set field2 $(quoted ${EMPTY}) \
    | build)
testy2=$(newBuilder \
    | setOrClear field1 $(quoted ${EMPTY}) \
    | set field2 $(quoted ${POPULATED}) \
    | build)
testy3=$(newBuilder \
    | set field1 $(quoted ${POPULATED}) \
    | setOrClear field2 $(quoted ${EMPTY}) \
    | build)
testy4=$(newBuilder \
    | set field1 $(quoted ${EMPTY}) \
    | setOrClear field2 $(quoted ${POPULATED}) \
    | build)
echo $testy1
echo $testy2
echo $testy3
echo $testy4

echo $MENUITEMS
echo $MENUITEMSLOOP
echo $MENUITEMSCONCISE