#!/bin/bash
#
# io.sh
#
# Copyright 2019 Luigi Santivetti <luigi.santivetti@gmail.com>

# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:

# The above copyright notice and this permission notice (including the next
# paragraph) shall be included in all copies or substantial portions of the
# Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
# ITS SUPPLIERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
# IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

# @1      : version file containg git sha
# @return : stdout, instance version: '${git_sha}@${script_now}'
function __get_script_ver_file
{
	[ "$1" = "-q" ] && local q=1 && shift

	git diff-index --quiet HEAD 2>/dev/null || {
		 [ -n "$q" ] || lets -l -w "git unstaged changes"
	}

	[ -f "$instance_d/$__version" ] && {
		local ver="$(< "$instance_d/$__version")"
		local now="${ver##*@}"; local sha="${ver%%@*}"
		[ ${#now} -eq ${#sha} ] && [ ${#now} -eq ${#script_now} ] || {
			lets -l -e "invalid version"; return $s_err
		}
		echo "$ver" && return $s_ok
	}
	lets -l -w "invalid version file" && return $s_err
}

function __get_script_ver_git
{
	[ "$1" = "-q" ] && local q=1 && shift

	git diff-index --quiet HEAD 2>/dev/null || {
		 [ -n "$q" ] || lets -l -w "git unstaged changes"
	}

	local -i len="${#script_now}"
	local sha="$(git log --pretty=format:'%H' -n 1)"
	[ -n "$sha" ] || { lets -l -e "git log failed"; return $s_err; }

	echo "${sha:0:$len}@$script_now"
}

function get_script_ver
{
	case "$1" in
		--file | -f ) shift; __get_script_ver_file "${@}" ;;
		--git  | -g ) shift; __get_script_ver_git "${@}" ;;
	esac
}

# @1      : absolute path to prospective file
# @return : file, instance version: '${git_sha}@${script_now}'
function set_script_ver
{
	local -r vfile="$2"

	is_unix_path $vfile && touch $vfile || {
			lets -l -e "invalid version file"; return 1
		}

	echo "$1" > "$vfile"
}

# @1       : text to be sent to stdout via cat
# @2       : (optional) absolute path to a prospective file in DOCKER_ROOT
# @return  : success if @2 isn't given or if @2 is valid
# @desc    : do not write to file if it doesn't live inside $instance_d
function catvar
{
	if [ -z "$2" ]; then
		cat <<EOF
${1}
EOF
	elif is_in_tree_instance_d $2; then
		echo > $2; cat > $2 <<EOF
${1}
EOF
	else
		return $s_err
	fi
}

# @1      : text to append
# @2      : absolute path to a valid file
# @return : success if @2 is valid
function appvar
{
	[ -f "$2" ] && catvar "$1" >> "$2" || lets -l -e "invalid: $2"
}

# @1      : (optional) absolute path to a valid file
# @desc   : echo a formatted header, including the file name if passed in
function get_header
{
	if is_in_tree_instance_d "$1"; then
		local header="\
# $head_tag $(basename $1)

$license"
	else
		local header="\
$license"
	fi
	echo "$header"
}

# @desc   : echo a formatted footer
function get_footer
{
	local __ver="$(get_script_ver --file -q)"
	__ver="${__ver%@*}"

	local footer=\
"# $foot_tag $__ver@$script_now"
	echo "$footer"
}

function __create_instance_d
{
	is_valid_new_dir $2 || return $s_err4
	mkdir -p $2         || return $s_err5

	# do not remove directory - it should never be so
	rm -f $1            || return $s_err6
	ln -sf $2 $1        || return $s_err7
}

# @1      : absolute path to $instance_d
# @desc   : validate dkrc_out_d acutally is what we expect it to be
function __is_valid_instance_d_link
{
	local ver_id="$(readlink -f $1)"
	local version_f="$1/$__version"
	ver_id="${ver_id##*-}"
	local run_time="${ver_id#*@}"

	test -n "$ver_id"                  || return $s_err3
	is_unix_path "$1"                  || return $s_err4
	test -L "$1"                       || return $s_err5
	test -f "$version_f"               || return $s_err6
	[ "$ver_id" = "$(< $version_f)"  ] || return $s_err7

	# This is the case calling doins with multiple modules
	[ "$run_time" = "$script_now"  ] && return $s_err8 || \
			return $s_ok
}

# @1      : absolute path to $instance_d
# @desc   : validate dkrc_out_d acutally is what we expect it to be
function is_valid_instance_d_link
{
	__is_valid_instance_d_link $1
	case "$?" in
		$s_err3 ) lets -l -e "instance version id"   ;;
		$s_err4 ) lets -l -e "instance path"         ;;
		$s_err5 ) lets -l -e "instance link"         ;;
		$s_err6 ) lets -l -e "instance version file" ;;
		$s_err7 ) lets -l -e "signature mismatch"    ;;
		$s_err8 ) return $s_err2 ;;
		$s_ok   ) return $s_ok ;;
	esac; return $s_err
}

function __is_valid_input
{
	test -L "$1" && {
		is_valid_instance_d_link "$1"
		case "$?" in
			$s_err2 ) return $s_err2 ;; # different module, same run
			$s_err  ) return $s_err  ;; # genuine error
			$s_ok   )
				local old_instance="$(basename "$(readlink -f $1)")"

				lets -l -i "'$(basename $1)' points to '$old_instance'"
				lets -l -i "update this link to '$2'"
				lets -a "would you like to continue?" && \
					return $s_ok || return $s_err ;;
		esac
	}

	! test -e "$1" || return $s_err3
}

# @desc   : create a new instance_d, either by updating an existing
#         : symlink or creating everything from scratch.
function create_instance_d
{
	local ver="$(get_script_ver --git)"
	local new_instance="$(basename $1)-$ver"
	local new_instance_d="$(dirname $1)/$new_instance"

	__is_valid_input "$1" "$new_instance"
	case "$?" in
		$s_err  ) lets -l -i "goodbye"; return $s_err ;;
		$s_err2 ) return $s_ok ;; # no error, no further actions
		$s_err3 ) lets -l -e "$1 busy"; return $s_err ;;
	esac

	__create_instance_d "$1" "$new_instance_d"
	case "$?" in
		$s_err4 ) lets -l -e "instance path"   ; return $s_err ;;
		$s_err5 ) lets -l -e "instance mkdir"  ; return $s_err ;;
		$s_err6 ) lets -l -e "instance unlink" ; return $s_err ;;
		$s_err7 ) lets -l -e "instance link"   ; return $s_err ;;
	esac

	set_script_ver $ver $instance_d/$__version || return $s_err
}

# @       : a list of absolute paths to prospective folders
function create_directory
{
	local d

	for d in ${@}; do
		is_unix_path $d || { lets -l -d "invalid path: $d"; return $s_err; }
		[ -d "$d" ] || { mkdir -p $d && lets -l -d "mkdir $d"; }
	done
}

# @1      : (optional) option --dry
# @2      : file text content
# @3      : absolute path to a valid target file
# @return : Success if @3 is valid
# @desc   : Redirect a bash variable to stdout or file
function __write_to_file
{
	[ "$1" = "--dry" ] && shift || local file_path=$2
	local file_text="${!1}"

	case "$1" in
		*"_bang_"* )
			local shebang="$(catvar "$file_text" | head --lines 1)"
			file_text="$(catvar "$file_text" | tail --lines +2)"
			local file_content="\
${shebang}

$(get_header $2)

${file_text}

$(get_footer)"
					;;
		*          )
			local file_content="\
$(get_header $2)

${file_text}

$(get_footer)"
					;;
	esac

	catvar "$file_content" $file_path
}

# @1      : diff flags
# @2      : file text content
# @3      : absolute path to an existing file
# @desc   : This function can diff an existing file against some new content
function __diff_file
{
	local flags=$1; shift

	if [ -f "$2" ]; then
		# NOTE: "$(echo "$1")" makes sure $1 isn't broken down into multiple
		# strings according to the bash IFS expasion.
		# FIXME: check __write_to_file
		diff $flags $2 <(__write_to_file --dry "$(echo "$1")" $2)
	else
		lets -l -d "invalid file: $2"
		return $s_err2
	fi
}

# @1      : diff flags
# @2      : file text content
# @3      : absolute path to an existing file
# @desc   : This function can diff an existing file against some new content
function is_file_diff
{
	__diff_file "$1" "$2" "$3" &>/dev/null
}

# @1      : file text content
# @2      : absolute path to a valid file
function __splash_file
{
	local flags="--suppress-common-lines"
	flags+=" --ignore-matching-lines=$rex_legal_file_header_tag"
	flags+=" --ignore-matching-lines=$rex_legal_file_footer_tag"
	flags+=" --report-identical-files"
	flags+=" --color"
#	flags+=" --ignore-blank-lines"

	__diff_file "$flags" "$1" "$2" | lets -l -x "diff"
	case "${PIPESTATUS[0]}" in
		$s_ok   ) lets -l -i --phew "MATCH: $(basename "$2")" ;;
		$s_err  ) lets -l -w "DIFFER: $(basename "$2")" ;;
		$s_err2 ) lets -l -w "NOT-FOUND: $(basename "$2")" ;;
	esac

	return $s_ok
}

# @1      : file text content
# @2      : absolute path to a valid file
# @desc   : Update the content of an already generated file. This is useful when
#         : the user doesn't want/need to recreate a new rootfs from scratch.
function __update_file
{
	local file_name="$(basename $2)"
	local flags="--suppress-common-lines"
	flags+=" --ignore-matching-lines=$rex_legal_file_header_tag"
	flags+=" --ignore-matching-lines=$rex_legal_file_footer_tag"
	#flags+=" --report-identical-files"
	#flags+=" --ignore-blank-lines"

	is_file_diff "$flags" "$1" $2
	case "$?" in
		$s_ok   ) lets -l -i "no need to update: $file_name"; return $s_ok ;;
		$s_err2 ) lets -l -w "add one on update: $file_name" ;;
	esac

	local old_foot_tags="$(grep -E "$rex_legal_file_footer_tag" -- $2 2>/dev/null)"

	if ! __write_to_file "$1" $2; then
		lets -l -e "failed to update $file_name"; return $s_err
	fi

	lets -l -i "changed on update: $file_name"

	if [ -n "$old_foot_tags" ]; then
		if ! appvar "$old_foot_tags" $2; then
			lets -l -e "failed to append $old_foot_tags"
		fi
	fi
}

function __create_file
{
	[ "$1" = "--dry" ] && local dry=$1 && shift || local dry=""

	if [ -f "$2" ]; then
		lets -l -w "overriding: $(basename $2)"
	fi

	__write_to_file $dry "$1" "$2"
}

function __file_do_helper
{
	local __file="$2"
	local __cmd="rm"
	local __line="$__cmd $__file $script_now $module $1"

	case "$1" in
		--update )
			[ -f "$3" ] && {
				local flags="--follow-symlinks -i -E"

				# Has $2 been actually updated?
				grep -qE "$rex_legal_file_footer_tag$script_now" $2 && {

					# $3 is not marked for deletion
					grep -qE "^#$__cmd $__file .*" $3 && {

						# Update line to report script_now, module and option
						sed $flags "s%^#$__cmd $__file .*$%#$__line%g" -- $3
						return $s_ok
					}

					# $3 is marked for deletion
					grep -qE "^$__cmd $__file .*" $3 && {

						# Update line to report script_now, module and option.
						# Also, comment it out, as $3 is not to be removed.
						sed $flags "s%^$__cmd $__file .*$%#$__line%g" -- $3
						return $s_ok
					}

					[ "$(grep -E "$rex_legal_file_footer_tag" $2 | wc -l)" -eq 1 ] && {

						# Update instance by adding a file. Equivalent to --create, but
						# do not mark $2 for removal.
						[ -f "$3" ] && {
							! grep -q "$__cmd $2" $3 && echo "#$__line" >> $3
							return $s_ok
						}

						lets -l -w "update without $3. Advise to wipe it all"
						echo "#$__line" > $3 && return $s_ok
					}

					lets -l -e "$(basename $3) not tracking $(basename $2)"
					return $s_err
				}

				# Is $2 marked for deletion? If so, un-mark it
				grep -qE "^$__cmd $__file .*" $3 && {
					sed $flags "s%^$__cmd $__file%#$__cmd $__file%g" -- $3
					return $s_ok
				}
			} ;;
		--create )
			[ -f "$3" ] && {
				! grep -q "$__cmd $2" $3 && echo "$__line" >> $3
				return $s_ok
			}; echo "$__line" > $3 ;;
	esac
}

# @1      : file text content
# @2      : absolute path to a valid file
# @desc   : Update the content of an already generated file. This is useful
#         : when the user doesn't want/need to recreate a new rootfs from
#         : scratch.
function __file_do
{
	# Option
	local option=$1; shift
	local __un_f=$1; shift

	case "$option" in
		--update ) local -r func="__update_file" ;;
		--create ) local -r func="__create_file" ;;
		--splash ) local -r func="__splash_file" ;;
		*) lets -l -e "invalid option $option"; return $s_err ;;
	esac

	local -i len="${#} / 2"
	local -i i

	local -a path=( "${@:1:$len}" ); shift $len
	local -a cont=( "${@}" )

	if [ ${#path[@]} -ne ${#cont[@]} ]; then
		lets -l -e "mismatch: $len, ${#path[@]} vs ${#cont[@]}"
		return $s_err
	fi

	# Remove comment before processing all files, for this module only
	if [ -f "$__un_f" ]; then
		cp "$__un_f" "$__un_f.bkp" # be safe
		sed --follow-symlinks -i -E "s%^#(.+ $module .+)%\1%g" -- $__un_f
	fi

	for i in ${!path[@]}; do
		if ! $func ${cont[$i]} ${path[$i]}; then
			lets -l -d "failed to ${func%_file} ${path[$i]}"
			cp "$__un_f.bkp" "$__un_f" && rm -f "$__un_f.bkp"
			return $s_err
		fi

		# FIXME: handle file permissions in a proper way
		case "${cont[$i]}" in *"_bang_"* ) chmod +x ${path[$i]} ;; esac

		__file_do_helper $option ${path[$i]} $__un_f || return $s_err
		lets -l -d "${func%_file} $(basename ${path[$i]})"
	done

	case "$option" in
		--update )
			[ ! -f "$__un_f" ] && {
				cp "$__un_f.bkp" "$__un_f" && rm -f "$__un_f.bkp"; return $s_err
			}

			local -a __rmline
			while read -a __rmline; do
				local __cmd="${__rmline[0]}"; local __f="${__rmline[1]}"
				case "${__rmline[*]}" in
					'' | '\n' | '#'* )
						lets -l -d "skip: $__cmd: $(basename "$__f")"
						continue ;;
					* ) [ ! -f "$__f" ] && {
							lets -l -w "$__cmd *not* installed: $(basename "$__f")"
						} || { lets -l -i "$__cmd installed: $(basename "$__f")"; }

						eval "$__cmd $__f" && {
							# Got to remove this line and it will be lost forever
							sed --follow-symlinks -i -E "\:$__cmd $__f.*:d" -- "$__un_f"
						} || { lets -l -e "failed to remove $__f"; } ;;
				esac
			done <<< $(grep -E "[[:space:]]$module[[:space:]]" -- $__un_f) ;;
	esac

	rm -f "$__un_f.bkp"
	return $s_ok
}