#!/bin/bash

# Compute a draft upgrade script for the DB schema, based on Git revisions.

# Depends: apgdiff

set -e

UPGRADE_DIR="upgrades"
DB_NAME="softwareheritage-dev"

usage () {
    echo "Usage: db-upgrade GIT_REV_FROM [GIT_REV_TO]"
    echo "Example: db-upgrade HEAD^"
    echo "         db-upgrade HEAD~4 HEAD~2"
    echo "See also: gitrevisions(7)"
    exit 1
}

pg_dump_revision () {
    rev="$1"
    dump="$2"

    echo "checking out revision $rev, and dumping DB at the time..."
    if [ "$rev" != "HEAD" ] ; then
	git checkout --quiet "$rev"
    fi
    make distclean filldb > /dev/null
    pg_dump "$DB_NAME" > "$dump"
    if [ "$rev" != "HEAD" ] ; then
	git checkout --quiet -
    fi
}

# argument parsing
if [ -z "$1" ] ; then
    usage
fi
from_rev="$1"
shift 1
if [ -z "$1" ] ; then
    to_rev="HEAD"
else
    to_rev="$1"
    shift 1
fi

old_dump=$(mktemp tmp.swh-db-upgrade.XXXXXXXXXX)
new_dump=$(mktemp tmp.swh-db-upgrade.XXXXXXXXXX)
trap "rm -f $old_dump $new_dump" EXIT

schema_version=$(grep -hri -A 1 '^insert into dbversion' ../swh/storage/sql | tail -n 1 \
	      | sed -e 's/.*values(//i' -e 's/,.*//')
upgrade_script=$(mktemp -p "$UPGRADE_DIR" $(printf '%.03d' ${schema_version}).XXXX.sql)
pg_dump_revision "$from_rev" "$old_dump"
pg_dump_revision "$to_rev" "$new_dump"

cat > "$upgrade_script" <<EOF
-- SWH DB schema upgrade
-- from_version: XXX TODO
-- to_version: ${schema_version}
-- description: XXX TODO

insert into dbversion(version, release, description)
      values($schema_version, now(), 'Work In Progress');
EOF
echo "diffing dumps..."
apgdiff "$old_dump" "$new_dump" >> "$upgrade_script"

echo "all done."
echo "Draft upgrade script is at: ${upgrade_script}"