#! /bin/bash
#
#	Copyright (c) 2019-2020 Apple Inc. All rights reserved.
#

declare -r version=1.4
declare -r script=${BASH_SOURCE[0]}
declare -r recordTypesURL='https://www.iana.org/assignments/dns-parameters/dns-parameters-4.csv'

#============================================================================================================================

PrintHelp()
{
	echo ""
	echo "Usage: $( basename "${script}" ) [options]"
	echo ""
	echo "Options:"
	echo "    -O '<name>,<value>' Specifies a record name-value pair override. Can be used more than once."
	echo "    -h                  Display script usage."
	echo "    -V                  Display version of this script and exit."
	echo ""
	echo "This script writes C functions to convert DNS resource record type values to strings and vice versa to stdout"
	echo "based on the latest DNS resource record type data available at"
	echo ""
	echo "    ${recordTypesURL}"
	echo ""
}

#============================================================================================================================

ErrQuit()
{
	echo "error: $*" 1>&2
	exit 1
}

#============================================================================================================================

StripLeadingTrailingWhitespace()
{
	sed 's/^[[:space:]]*//;s/[[:space:]]*$//'
}

#============================================================================================================================

GetNamesAndValues()
{
	local -r isOverride=${1}
	shopt -s nocasematch
	while IFS=',' read name value others; do
		name=$( StripLeadingTrailingWhitespace <<< "${name}" )
		[[ ${name} =~ ^unassigned$ ]] && continue
		
		value=$( StripLeadingTrailingWhitespace <<< "${value}" )
		[[ ${value} =~ ^[0-9]+$ ]] || continue
		[ "${value}" -le 65535 ] || continue

		if [ "${value}" -eq 255 ]; then
			name=ANY
		fi
		echo "${name},${value},${isOverride}"
	done
	shopt -u nocasematch
}

#============================================================================================================================

RecordTypeMnemonicToEnum()
{
	name="${1//[^A-Za-z0-9_]/_}" # Only allow alphanumeric and underscore characters.
	printf "kDNSRecordType_${name}"
}

PrintRecordTypesEnum()
{
	local -r inputFile=${1}
	printf "typedef enum\n"
	printf "{\n"
	< "${inputFile}" sort --field-separator=, --key=2,2 --numeric-sort --unique |
	while IFS=',' read name value override; do
		local enum=$( RecordTypeMnemonicToEnum "${name}" )
		printf "\t%-28s= %d," "${enum}" "${value}"
		if [ "${override}" -ne 0 ]; then
			printf " // OVERRIDE"
		fi
		printf "\n"
	done
	printf "\t\n"
	printf "}\tDNSRecordType;\n"
}

#============================================================================================================================

PrintValueToStringElseIf()
{
	local -r first=${1}
	local -r last=${2}
	[ "${first}" -le "${last}" ] || ErrQuit "${first} > ${last}"
	shift 2
	local stringArray=( "$@" )
	
	if [ "${last}" -ne "${first}" ]; then
		printf "\telse if( ( inValue >= ${first} ) && ( inValue <= ${last} ) )\n"
		local -r arrayVarName="sNames_${first}_${last}"
	else
		printf "\telse if( inValue == ${first} )\n"
		local -r arrayVarName="sNames_${first}"
	fi
	printf "\t{\n"
	printf "\t\tstatic const char * const\t\t${arrayVarName}[] =\n"
	printf "\t\t{\n"
	local value=${first}
	for string in "${stringArray[@]}"; do
		printf "\t\t\t%-15s // %3d\n" "\"${string}\"," "${value}"
		value=$(( value + 1 ))
	done
	local -r stringCount=$(( value - first ))
	local -r expectedCount=$(( last - first + 1 ))
	[ "${stringCount}" -eq "${expectedCount}" ] || ErrQuit "${stringCount} != ${expectedCount}"
	printf "\t\t};\n"
	printf "\t\tstring = ${arrayVarName}[ inValue - ${first} ];\n"
	printf "\t}\n"
}

#============================================================================================================================

PrintValueToStringFunction()
{
	local -r inputFile=${1}
	printf "const char *\tDNSRecordTypeValueToString( const int inValue )\n"
	printf "{\n"
	printf "\tswitch( inValue )\n"
	printf "\t{\n"
	< "${inputFile}" sort --field-separator=, --key=2,2 --numeric-sort --unique |
	{
		local stringArray=()
		while IFS=',' read name value override; do
		    local enum=$( RecordTypeMnemonicToEnum "${name}" )
			if [ "${override}" -eq 0 ]; then
				printf "\t\t%-32s%s" "case ${enum}:" "return( \"${name}\" );"
			else
				printf "\t\t%-32s%-24s // OVERRIDE" "case ${enum}:" "return( \"${name}\" );"
			fi
			printf "\n"
		done
	}
	printf "\t}\n"
	printf "\treturn( NULL );\n"
	printf "}\n"
}

#============================================================================================================================

PrintStringToValueFunction()
{
	local -r inputFile=${1}
	printf "#include <stdlib.h>\n"
	printf "\n"
	printf "typedef struct\n"
	printf "{\n"
	printf "\tconst char *\t\tname;\n"
	printf "\tuint16_t\t\t\tvalue;\n"
	printf "\t\n"
	printf "}\t_DNSRecordTypeItem;\n"
	printf "\n"
	printf "static int\t_DNSRecordTypeStringToValueCmp( const void *inKey, const void *inElement );\n"
	printf "\n"
	printf "uint16_t\tDNSRecordTypeStringToValue( const char * const inString )\n"
	printf "{\n"
	printf "\t// The name-value table is sorted by name in ascending lexicographical order to allow going from name to\n"
	printf "\t// value in logarithmic time via a binary search.\n"
	printf "\t\n"
	printf "\tstatic const _DNSRecordTypeItem\t\tsTable[] =\n"
	printf "\t{\n"
	
	< "${inputFile}" sort --field-separator=, --key=1,1 --ignore-case --unique |
	while IFS=',' read name value override; do
		local enum=$( RecordTypeMnemonicToEnum "${name}" )
		printf "\t\t%-16s%-28s }," "{ \"${name}\"," "${enum}"
		if [ "${override}" -ne 0 ]; then
			printf " // OVERRIDE"
		fi
		printf "\n"
	done
	printf "\t};\n"
	printf "\tconst _DNSRecordTypeItem *\t\t\titem;\n"
	printf "\t\n"
	printf "\titem = (_DNSRecordTypeItem *) bsearch( inString, sTable, sizeof( sTable ) / sizeof( sTable[ 0 ] ),\n"
	printf "\t\tsizeof( sTable[ 0 ] ), _DNSRecordTypeStringToValueCmp );\n"
	printf "\treturn( item ? item->value : 0 );\n"
	printf "}\n"
	printf "\n"
	printf "static int\t_DNSRecordTypeStringToValueCmp( const void * const inKey, const void * const inElement )\n"
	printf "{\n"
	printf "\tconst _DNSRecordTypeItem * const\t\titem = (const _DNSRecordTypeItem *) inElement;\n"
	printf "\treturn( strcasecmp( (const char *) inKey, item->name ) );\n"
	printf "}\n"
}

#============================================================================================================================

ExitHandler()
{
	if [ -d "${tempDir}" ]; then
		rm -fr "${tempDir}"
	fi
}

#============================================================================================================================

PrintAutoGenNote()
{
	printf "// This code was autogenerated on $( date -u '+%Y-%m-%d' ) by $( basename ${script} ) version ${version}\n"
	printf "// Data source URL: ${recordTypesURL}\n"
	printf "// Overrides: "
	if [ "${#}" -gt 0 ]; then
		local separator=""
		for override in "${@}"; do
			printf "%s'%s'" "${separator}" "${override}"
			separator=", "
		done
		printf "\n"
	else
		printf "none\n"
	fi
	printf "\n"
}

#============================================================================================================================

main()
{
	local -a overrides
	while getopts ":hO:V" option; do
		case "${option}" in
			h)
				PrintHelp
				exit 0
				;;
			O)
				overrides+=( "${OPTARG}" )
				;;
			V)
				echo "$( basename "${script}" ) version ${version}"
				exit 0
				;;
			:)
				ErrQuit "option '${OPTARG}' requires an argument."
				;;
			*)
				ErrQuit "unknown option '${OPTARG}'."
				;;
		esac
	done
	
	[ "${OPTIND}" -gt "$#" ] || ErrQuit "unexpected argument \"${!OPTIND}\"."
	
	trap ExitHandler EXIT
	tempDir=$( mktemp -d ) || ErrQuit "Failed to make temporary directory."
	declare -r originalRecordTypesFile="${tempDir}/recordTypesOriginal.csv"
	curl --output "${originalRecordTypesFile}" "${recordTypesURL}" || ErrQuit "Failed to download CSV file."
	
	declare -r overridesFile="${tempDir}/overrides.csv"
	for override in "${overrides[@]}"; do
		echo "${override}"
	done | GetNamesAndValues 1 > "${overridesFile}"
	
	declare -r recordTypesFile="${tempDir}/recordTypes.csv"
	< "${originalRecordTypesFile}" GetNamesAndValues 0 > "${recordTypesFile}"
	
	declare -r tempFile="${tempDir}/temp.csv"
	cat "${overridesFile}" "${recordTypesFile}" | sort --field-separator=, --key=2,2 --unique --numeric-sort > "${tempFile}"
	cat "${overridesFile}" "${tempFile}" | sort --field-separator=, --key=1,1 --unique --ignore-case > "${recordTypesFile}"
	
	PrintAutoGenNote "${overrides[@]}"
	PrintRecordTypesEnum "${recordTypesFile}"
	printf "\n"
	PrintAutoGenNote "${overrides[@]}"
	PrintValueToStringFunction "${recordTypesFile}"
	printf "\n"
	PrintAutoGenNote "${overrides[@]}"
	PrintStringToValueFunction "${recordTypesFile}"
}

main "$@"