#!/usr/bin/env bash
set -Eeo pipefail
# TODO swap to -Eeuo pipefail above (after handling all potentially-unset variables)

# usage: file_env VAR [DEFAULT]
#    ie: file_env 'XYZ_DB_PASSWORD' 'example'
# (will allow for "$XYZ_DB_PASSWORD_FILE" to fill in the value of
#  "$XYZ_DB_PASSWORD" from a file, especially for Docker's secrets feature)
file_env() {
    local var="$1"
    local fileVar="${var}_FILE"
    local def="${2:-}"
    if [ "${!var:-}" ] && [ "${!fileVar:-}" ]; then
	echo >&2 "error: both $var and $fileVar are set (but are exclusive)"
	exit 1
    fi
    local val="$def"
    if [ "${!var:-}" ]; then
	val="${!var}"
    elif [ "${!fileVar:-}" ]; then
	val="$(< "${!fileVar}")"
    fi
    export "$var"="$val"
    unset "$fileVar"
}

# check to see if this file is being run or sourced from another script
_is_sourced() {
    # https://unix.stackexchange.com/a/215279
    [ "${#FUNCNAME[@]}" -ge 2 ] \
	&& [ "${FUNCNAME[0]}" = '_is_sourced' ] \
	&& [ "${FUNCNAME[1]}" = 'source' ]
}

# used to create initial postgres directories and if run as root, ensure ownership to the "postgres" user
docker_create_db_directories() {
    local user; user="$(id -u)"

    mkdir -p "$PGDATA"
    # ignore failure since there are cases where we can't chmod (and PostgreSQL might fail later anyhow - it's picky about permissions of this directory)
    chmod 700 "$PGDATA" || :

    # ignore failure since it will be fine when using the image provided directory; see also https://github.com/docker-library/postgres/pull/289
    mkdir -p /var/run/postgresql || :
    chmod 775 /var/run/postgresql || :

    # Create the transaction log directory before initdb is run so the directory is owned by the correct user
    if [ -n "$POSTGRES_INITDB_XLOGDIR" ]; then
	mkdir -p "$POSTGRES_INITDB_XLOGDIR"
	if [ "$user" = '0' ]; then
	    find "$POSTGRES_INITDB_XLOGDIR" \! -user postgres -exec chown postgres '{}' +
	fi
	chmod 700 "$POSTGRES_INITDB_XLOGDIR"
    fi

    # allow the container to be started with `--user`
    if [ "$user" = '0' ]; then
	find "$PGDATA" \! -user postgres -exec chown postgres '{}' +
	find /var/run/postgresql \! -user postgres -exec chown postgres '{}' +
    fi
}

# initialize empty PGDATA directory with new database via 'initdb'
# arguments to `initdb` can be passed via POSTGRES_INITDB_ARGS or as arguments to this function
# `initdb` automatically creates the "postgres", "template0", and "template1" dbnames
# this is also where the database user is created, specified by `POSTGRES_USER` env
docker_init_database_dir() {
    # "initdb" is particular about the current user existing in "/etc/passwd", so we use "nss_wrapper" to fake that if necessary
    # see https://github.com/docker-library/postgres/pull/253, https://github.com/docker-library/postgres/issues/359, https://cwrap.org/nss_wrapper.html
    if ! getent passwd "$(id -u)" &> /dev/null && [ -e /usr/lib/libnss_wrapper.so ]; then
	export LD_PRELOAD='/usr/lib/libnss_wrapper.so'
	export NSS_WRAPPER_PASSWD="$(mktemp)"
	export NSS_WRAPPER_GROUP="$(mktemp)"
	echo "postgres:x:$(id -u):$(id -g):PostgreSQL:$PGDATA:/bin/false" > "$NSS_WRAPPER_PASSWD"
	echo "postgres:x:$(id -g):" > "$NSS_WRAPPER_GROUP"
    fi

    if [ -n "$POSTGRES_INITDB_XLOGDIR" ]; then
	set -- --xlogdir "$POSTGRES_INITDB_XLOGDIR" "$@"
    fi

    eval 'initdb --username="$POSTGRES_USER" --pwfile=<(echo "$POSTGRES_PASSWORD") '"$POSTGRES_INITDB_ARGS"' "$@"'

    # unset/cleanup "nss_wrapper" bits
    if [ "${LD_PRELOAD:-}" = '/usr/lib/libnss_wrapper.so' ]; then
	rm -f "$NSS_WRAPPER_PASSWD" "$NSS_WRAPPER_GROUP"
	unset LD_PRELOAD NSS_WRAPPER_PASSWD NSS_WRAPPER_GROUP
    fi
}

# print large warning if POSTGRES_PASSWORD is long
# error if both POSTGRES_PASSWORD is empty and POSTGRES_HOST_AUTH_METHOD is not 'trust'
# print large warning if POSTGRES_HOST_AUTH_METHOD is set to 'trust'
# assumes database is not set up, ie: [ -z "$DATABASE_ALREADY_EXISTS" ]
docker_verify_minimum_env() {
    # check password first so we can output the warning before postgres
    # messes it up
    if [ "${#POSTGRES_PASSWORD}" -ge 100 ]; then
	cat >&2 <<-'EOWARN'

	    WARNING: The supplied POSTGRES_PASSWORD is 100+ characters.

	      This will not work if used via PGPASSWORD with "psql".

	      https://www.postgresql.org/message-id/flat/E1Rqxp2-0004Qt-PL%40wrigleys.postgresql.org (BUG #6412)
	      https://github.com/docker-library/postgres/issues/507

	EOWARN
    fi
    if [ -z "$POSTGRES_PASSWORD" ] && [ 'trust' != "$POSTGRES_HOST_AUTH_METHOD" ]; then
	# The - option suppresses leading tabs but *not* spaces. :)
	cat >&2 <<-'EOE'
	    Error: Database is uninitialized and superuser password is not specified.
	           You must specify POSTGRES_PASSWORD to a non-empty value for the
	           superuser. For example, "-e POSTGRES_PASSWORD=password" on "docker run".

	           You may also use "POSTGRES_HOST_AUTH_METHOD=trust" to allow all
	           connections without a password. This is *not* recommended.

	           See PostgreSQL documentation about "trust":
	           https://www.postgresql.org/docs/current/auth-trust.html
	EOE
	exit 1
    fi
    if [ 'trust' = "$POSTGRES_HOST_AUTH_METHOD" ]; then
	cat >&2 <<-'EOWARN'
	    ********************************************************************************
	    WARNING: POSTGRES_HOST_AUTH_METHOD has been set to "trust". This will allow
	             anyone with access to the Postgres port to access your database without
	             a password, even if POSTGRES_PASSWORD is set. See PostgreSQL
	             documentation about "trust":
	             https://www.postgresql.org/docs/current/auth-trust.html
	             In Docker's default configuration, this is effectively any other
	             container on the same system.

	             It is not recommended to use POSTGRES_HOST_AUTH_METHOD=trust. Replace
	             it with "-e POSTGRES_PASSWORD=password" instead to set a password in
	             "docker run".
	    ********************************************************************************
	EOWARN
    fi
}

# usage: docker_process_init_files [file [file [...]]]
#    ie: docker_process_init_files /always-initdb.d/*
# process initializer files, based on file extensions and permissions
docker_process_init_files() {
    # psql here for backwards compatibility "${psql[@]}"
    psql=( docker_process_sql )

    echo
    local f
    for f; do
	case "$f" in
	    *.sh)
		# https://github.com/docker-library/postgres/issues/450#issuecomment-393167936
		# https://github.com/docker-library/postgres/pull/452
		if [ -x "$f" ]; then
		    echo "$0: running $f"
		    "$f"
		else
		    echo "$0: sourcing $f"
		    . "$f"
		fi
		;;
	    *.sql)    echo "$0: running $f"; docker_process_sql -f "$f"; echo ;;
	    *.sql.gz) echo "$0: running $f"; gunzip -c "$f" | docker_process_sql; echo ;;
	    *.sql.xz) echo "$0: running $f"; xzcat "$f" | docker_process_sql; echo ;;
	    *)        echo "$0: ignoring $f" ;;
	esac
	echo
    done
}

# Execute sql script, passed via stdin (or -f flag of pqsl)
# usage: docker_process_sql [psql-cli-args]
#    ie: docker_process_sql --dbname=mydb <<<'INSERT ...'
#    ie: docker_process_sql -f my-file.sql
#    ie: docker_process_sql <my-file.sql
docker_process_sql() {
    local query_runner=( psql -v ON_ERROR_STOP=1 --username "$POSTGRES_USER" --no-password )
    if [ -n "$POSTGRES_DB" ]; then
	query_runner+=( --dbname "$POSTGRES_DB" )
    fi

    PGHOST= PGHOSTADDR= "${query_runner[@]}" "$@"
}

# create initial database
# uses environment variables for input: POSTGRES_DB
docker_setup_db() {
    local dbAlreadyExists
    dbAlreadyExists="$(
	POSTGRES_DB= docker_process_sql --dbname postgres --set db="$POSTGRES_DB" --tuples-only <<-'EOSQL'
	    SELECT 1 FROM pg_database WHERE datname = :'db' ;
	EOSQL
    )"
    if [ -z "$dbAlreadyExists" ]; then
	POSTGRES_DB= docker_process_sql --dbname postgres --set db="$POSTGRES_DB" <<-'EOSQL'
	    CREATE DATABASE :"db" ;
	EOSQL
	echo
    fi
}

# Loads various settings that are used elsewhere in the script
# This should be called before any other functions
docker_setup_env() {
    file_env 'POSTGRES_PASSWORD'

    file_env 'POSTGRES_USER' 'postgres'
    file_env 'POSTGRES_DB' "$POSTGRES_USER"
    file_env 'POSTGRES_INITDB_ARGS'
    # default authentication method is md5
    : "${POSTGRES_HOST_AUTH_METHOD:=md5}"

    declare -g DATABASE_ALREADY_EXISTS
    # look specifically for PG_VERSION, as it is expected in the DB dir
    if [ -s "$PGDATA/PG_VERSION" ]; then
	DATABASE_ALREADY_EXISTS='true'
    fi
}

# append POSTGRES_HOST_AUTH_METHOD to pg_hba.conf for "host" connections
pg_setup_hba_conf() {
    {
	echo
	if [ 'trust' = "$POSTGRES_HOST_AUTH_METHOD" ]; then
	    echo '# warning trust is enabled for all connections'
	    echo '# see https://www.postgresql.org/docs/12/auth-trust.html'
	fi
	echo "host all all all $POSTGRES_HOST_AUTH_METHOD"
    } >> "$PGDATA/pg_hba.conf"
}

# start socket-only postgresql server for setting up or running scripts
# all arguments will be passed along as arguments to `postgres` (via pg_ctl)
docker_temp_server_start() {
    if [ "$1" = 'postgres' ]; then
	shift
    fi

    # internal start of server in order to allow setup using psql client
    # does not listen on external TCP/IP and waits until start finishes
    set -- "$@" -c listen_addresses='' -p "${PGPORT:-5432}"

    PGUSER="${PGUSER:-$POSTGRES_USER}" \
    pg_ctl -D "$PGDATA" \
	-o "$(printf '%q ' "$@")" \
	-w start
}

# stop postgresql server after done setting up user and running scripts
docker_temp_server_stop() {
    PGUSER="${PGUSER:-postgres}" \
    pg_ctl -D "$PGDATA" -m fast -w stop
}

# check arguments for an option that would cause postgres to stop
# return true if there is one
_pg_want_help() {
    local arg
    for arg; do
	case "$arg" in
	    # postgres --help | grep 'then exit'
	    # leaving out -C on purpose since it always fails and is unhelpful:
	    # postgres: could not access the server configuration file "/var/lib/postgresql/data/postgresql.conf": No such file or directory
	    -'?'|--help|--describe-config|-V|--version)
		return 0
		;;
	esac
    done
    return 1
}

_main() {
    # if first arg looks like a flag, assume we want to run postgres server
    if [ "${1:0:1}" = '-' ]; then
	set -- postgres "$@"
    fi

    if [ "$1" = 'postgres' ] && ! _pg_want_help "$@"; then
	docker_setup_env
	# setup data directories and permissions (when run as root)
	docker_create_db_directories
	if [ "$(id -u)" = '0' ]; then
	    # then restart script as postgres user
	    exec gosu postgres "$BASH_SOURCE" "$@"
	fi

	# only run initialization on an empty data directory
	if [ -z "$DATABASE_ALREADY_EXISTS" ]; then
	    docker_verify_minimum_env

	    # check dir permissions to reduce likelihood of half-initialized database
	    ls /docker-entrypoint-initdb.d/ > /dev/null

	    docker_init_database_dir
	    pg_setup_hba_conf

	    # PGPASSWORD is required for psql when authentication is required for 'local' connections via pg_hba.conf and is otherwise harmless
	    # e.g. when '--auth=md5' or '--auth-local=md5' is used in POSTGRES_INITDB_ARGS
	    export PGPASSWORD="${PGPASSWORD:-$POSTGRES_PASSWORD}"
	    docker_temp_server_start "$@"

	    docker_setup_db
	    docker_process_init_files /docker-entrypoint-initdb.d/*

	    docker_temp_server_stop
	    unset PGPASSWORD

	    echo
	    echo 'PostgreSQL init process complete; ready for start up.'
	    echo
	else
	    echo
	    echo 'PostgreSQL Database directory appears to contain a database; Skipping initialization'
	    echo
	fi
    fi

    exec "$@"
}

if ! _is_sourced; then
    _main "$@"
fi