#!/bin/bash
# DR #4677 - This script replaces all PKs in bufrmos_location with
#            sequence-generated values, and cascades the update to all
#            referencing tables.

PSQL="/awips2/psql/bin/psql"

# Check for existence of a table
table_exists() {
    ${PSQL} -U awips -Aqt -d metadata -c \
    "select 1 from information_schema.tables where table_name = '$1'"
}

# Given table name as argument, return the name of the FK constraint
# referencing bufrmos_location.
get_constraint_name() {
    ${PSQL} -U awips -Aqt -d metadata << EOF
    SELECT tc.constraint_name
    FROM information_schema.table_constraints AS tc 
    JOIN information_schema.key_column_usage AS kcu
    ON tc.constraint_name = kcu.constraint_name
    JOIN information_schema.constraint_column_usage AS ccu
    ON ccu.constraint_name = tc.constraint_name
    WHERE constraint_type = 'FOREIGN KEY'
    AND tc.table_name='$1'
    and ccu.table_name = 'bufrmos_location';
EOF
}

# Check for existence of bufrmos_locationseq
sequence_exists() {
    ${PSQL} -U awips -Aqt -d metadata << EOF
    select 0
    from information_schema.sequences
    where sequence_name = 'bufrmos_locationseq'
EOF
}

get_min_pk() {
    ${PSQL} -U awips -Aqt -d metadata << EOF
    select min(id) id
    from bufrmos_location;
EOF
}

get_max_pk() {
    ${PSQL} -U awips -Aqt -d metadata << EOF
    select max(id) id
    from bufrmos_location;
EOF
}

last_bufrmos_locationseq_value() { 
    ${PSQL} -U awips -Aqt -d metadata -c \
        "select last_value from bufrmos_locationseq;"
}


if [[ "$(sequence_exists)" != "0" ]]; then
    echo "INFO: bufrmos_locationseq does not exist in the database"
    echo "INFO: Attempting to create bufrmos_locationseq"
    ${PSQL} -U awips -d metadata -c \
        "create sequence bufrmos_locationseq increment 1 start 1;"
    if [[ "$?" != "0" || "$(sequence_exists)" != "0" ]]; then
        echo "ERROR: Failed to create bufrmos_locationseq"
        exit 1
    else
        echo "INFO Successfully created bufrmos_locationseq"
    fi
fi

min_pk="$(get_min_pk)"
max_pk="$(get_max_pk)"

if [[ ("$min_pk" -gt 0) && ("$max_pk" -le "$(last_bufrmos_locationseq_value)") ]]; then
    echo "WARN: Looks like PKs were already updated."
    echo "WARN: (smallest PK found: ${min_pk})"
    echo "WARN: (largest PK found: ${max_pk})"
    echo "WARN: Doing nothing."
    exit 0
fi

all_tables=(bufrmosavn bufrmoseta bufrmosgfs bufrmoshpc bufrmoslamp bufrmosmrf bufrmosngm)
tables=
fkeys=

for table in "${all_tables[@]}"; do
    if [[ $(table_exists $table) == "1" ]]; then
        tables+=("$table")
        fkeys+=("$(get_constraint_name $table)")
    fi
done

scriptfile=$(mktemp)

if [[ "$scriptfile" == "" ]]; then
    echo "ERROR: Failed to create temp file for script in /tmp"
    exit 1
fi

echo "begin transaction;" > $scriptfile

for i in $(seq 1 $(expr ${#tables[@]} - 1)); do
    cat << EOF >> $scriptfile
alter table ${tables[$i]}
drop constraint ${fkeys[$i]},
add constraint ${fkeys[$i]}
      FOREIGN KEY (location_id)
      REFERENCES bufrmos_location (id) MATCH SIMPLE
      ON UPDATE CASCADE ON DELETE NO ACTION;
EOF
done

cat << EOF >> $scriptfile
UPDATE bufrmos_location
   SET id=nextval('bufrmos_locationseq');
EOF

for i in $(seq 1 $(expr ${#tables[@]} - 1)); do
    cat << EOF >> $scriptfile
alter table ${tables[$i]}
drop constraint ${fkeys[$i]},
add constraint ${fkeys[$i]}
      FOREIGN KEY (location_id)
      REFERENCES bufrmos_location (id) MATCH SIMPLE
      ON UPDATE NO ACTION ON DELETE NO ACTION;
EOF
done

echo "commit;" >> $scriptfile

echo "INFO: Updating all PKs of bufrmos_location"
echo "INFO: This may take a few minutes..."

${PSQL} -U awips -d metadata < $scriptfile

echo "INFO: Done."
rm -f $scriptfile