#!/bin/sh

set -eu

input_to_db()
{
	local input=
	local db=

	input="$(mktemp)" || return 1
	cat - 1>"${input}" || { rm -f "${input}"; return 1; }
	if file "${input}" | grep -Fq SQLite; then
		# Input still a database: use it directly.
		db="${input}"
	else
		# Input already dumped to SQL: enter it into temporary database.
		db="$(mktemp)" || { rm -f "${input}"; return 1; }
		sqlite3 "${db}" 0<"${input}" || { rm -f "${input}"; return 1; }
		rm -f "${input}" || { rm -f "${db}"; return 1; }
	fi

	printf '%s' "${db}"
	return 0
}

del_from_db()
{
	local db="${1}"
	local spec="${2}"
	shift 2
	local table=
	local column=
	local value=

	value="${spec#*=}"
	spec="${spec%%=*}"
	table="${spec%%.*}"
	column="${spec#*.}"

	sqlite3 "${db}" "DELETE FROM ${table} WHERE ${column} = ${value};" || \
		return 1

	return 0
}

db_to_sql()
{
	local db="${1}"
	shift 1

	sqlite3 "${db}" '.dump' || return 1

	return 0
}

usage()
{
	printf 'Usage: %s [<table>.<column>=<value> ...]\n' "${0}"

	return 0
}

main()
{
	local arg=
	local db=

	for arg in "${@}"; do
		case "${arg}" in
			?*.?*=?*);;
			*) usage 1>&2; return 1;;
		esac
	done

	db="$(input_to_db)" || return 1
	for arg in "${@}"; do
		del_from_db "${db}" "${arg}" || { rm -f "${db}"; return 1; }
	done
	db_to_sql "${db}" || { rm -f "${db}"; return 1; }
	rm -f "${db}" || return 1

	return 0
}

main "${@}"