#!/bin/sh -e
# sdn-view: a viewer for sdn that makes use of Midnight Commander configuration
# to make more kinds of files directly viewable

if [ "$#" -ne 1 ]
then
	echo "Usage: $0 FILE" >&2
	exit 2
fi

# This handles both MC_DATADIR and odd installation locations.
datadir=
if command -v mc >/dev/null
then datadir=$(mc --datadir | sed 's/ (.*)$//')
fi

export SDN_VIEW_CONFIG=
for dir in "$HOME"/.config/mc "$datadir" /etc/mc
do
	if [ -n "$dir" -a -f "$dir/mc.ext.ini" ]
	then
		SDN_VIEW_CONFIG=$dir/mc.ext.ini
		break
	fi
done

export PAGER=${PAGER:-less}
export MC_EXT_FILENAME=$(realpath "$1")
export MC_EXT_BASENAME=$(basename "$1")
export MC_EXT_CURRENTDIR=$(dirname "$1")
export SDN_VIEW_TYPE=$(file -bz "$1")
process() (awk -f - <<'EOF'
BEGIN {
	if (!(Config = ENVIRON["SDN_VIEW_CONFIG"]))
		exit

	Verb = "View"
	Section = ""
	while ((getline < Config) > 0) {
		if (/^\s*(#.*)?$/) {
			# Skip.
		} else if (/^\[[^]]+\]$/) {
			Sections[++SectionsLen] = Section = substr($0, 2, length($0) - 2)
		} else if (/^[^=]+=[^=]*$/) {
			split($0, kv, "=")
			Keys[Section, kv[1]] = kv[2]
		}
	}

	Type     = ENVIRON["SDN_VIEW_TYPE"]
	Path     = ENVIRON["MC_EXT_FILENAME"]
	Basename = ENVIRON["MC_EXT_BASENAME"]
	Dirname  = ENVIRON["MC_EXT_CURRENTDIR"]

	for (i = 1; i <= SectionsLen; i++) {
		if (Sections[i] == "mc.ext.ini" ||
			Sections[i] == "Default" ||
			Sections[i] ~ /^Include[\/]/)
			continue
		try(Sections[i])
	}

	# Not attempting any inclusions here.
	print expand_command(Keys["Default", Verb])
}

function try(section,    pair, a, key, full, include) {
	for (pair in Keys) {
		split(pair, a, SUBSEP)
		if (a[1] == section)
			full[a[2]] = Keys[pair]
	}
	if ("Include" in full) {
		delete full["Open"]
		delete full["View"]
		delete full["Edit"]
		include = "Include/" full["Include"]
		for (pair in Keys) {
			split(pair, a, SUBSEP)
			if (a[1] == include)
				full[a[2]] = Keys[pair]
		}
	}
	if (ENVIRON["SDN_VIEW_DEBUG"]) {
		print "[" section "]" > "/dev/stderr"
		for (key in full)
			print "  " key ": " full[key] > "/dev/stderr"
	}
	if (Verb in full && section_matches(full, Type, Basename)) {
		print expand_command(full[Verb])
		exit
	}
}

function shell_escape(string) {
	gsub(/'/, "'\\''", string)
	return "'" string "'"
}

function expand_command(cmd,    toview, out, seq, argument, value, a, pipe) {
	out = ""
	while (match(cmd, /%[a-zA-Z]*\{[^}]*\}|%[a-zA-Z]+|%%/)) {
		out = out substr(cmd, 1, RSTART - 1)
		seq = substr(cmd, RSTART + 1, RLENGTH - 1)
		cmd = substr(cmd, RSTART + RLENGTH)

		argument = ""
		if (match(seq, /\{.*\}$/)) {
			argument = substr(seq, RSTART + 1, RLENGTH - 2)
			seq = substr(seq, 1, RSTART - 1)
		}

		if (seq == "%") {
			out = out "%"
		} else if (seq == "p") {
			out = out shell_escape(Basename)
		} else if (seq == "f") {
			out = out shell_escape(Path)
		} else if (seq == "d") {
			out = out shell_escape(Dirname)
		} else if (seq == "view") {
			toview = 1

			sub(/^ +/, "", cmd)
			split(argument, a, /,/)
			for (value in a) {
				if (a[value] == "hex")
					pipe = pipe " | od -t x1"

				# more(1) and less(1) either ignore or display this:
				#if (a[value] == "nroff")
				#	pipe = pipe " | col -b"
			}
		} else if (seq == "var") {
			value = ""
			if (!match(argument, /:.*/)) {
				if (argument in ENVIRON)
					value = ENVIRON[argument]
			} else {
				value = substr(argument, RSTART + 1)
				argument = substr(argument, 1, RSTART - 1)
				if (argument in ENVIRON)
					value = ENVIRON[argument]
			}
			out = out shell_escape(value)
		} else if (seq == "") {
			print Config ": prompting not supported" > "/dev/stderr"
			return
		} else {
			print Config ": unsupported: %" seq > "/dev/stderr"
			return
		}
	}
	out = out cmd pipe

	# While the processing is mostly generic for all verbs,
	# we'd have to distinguish non-view commands in this AWK script's output.
	if (!toview)
		return

	# In the case of out == "", we should just explicitly pass it to the pager,
	# however it currently mixes with the case of "we can't use this View=".
	return out
}

function section_matches(section, type, basename,    value) {
	if ("Directory" in section)
		return 0

	if ("Type" in section) {
		value = section["Type"]
		if ("TypeIgnoreCase" in section &&
			section["TypeIgnoreCase"] == "true") {
			type = tolower(type)
			value = tolower(value)
		}
		gsub(/\\\\/, "\\", value)
		gsub(/\\ /, " ", value)
		if (type !~ value)
			return 0
	}
	if ("Regex" in section) {
		value = section["Regex"]
		if ("RegexIgnoreCase" in section &&
			section["RegexIgnoreCase"] == "true") {
			basename = tolower(basename)
			value = tolower(value)
		}
		gsub(/\\\\/, "\\", value)
		return basename ~ value
	} else if ("Shell" in section) {
		value = section["Shell"]
		if ("RegexIgnoreCase" in section &&
			section["ShellIgnoreCase"] == "true") {
			basename = tolower(basename)
			value = tolower(value)
		}
		if (value !~ /^[.]/)
			return value == basename
		return length(basename) >= length(value) &&
			substr(basename, length(basename) - length(value) + 1) == value
	}
	return type != ""
}
EOF
)
command=$(process)
if [ -z "$command" ]
then "$PAGER" -- "$MC_EXT_FILENAME"
else eval "$command" | "$PAGER"
fi