agenda/agenda

#!/usr/bin/env bash
set -euo pipefail

# The editor used to edit agenda note files.
AGENDA_EDITOR=${AGENDA_EDITOR:-${VISUAL:-${EDITOR:-vi}}}

# The home of all files read and written by agenda.
#
# ```
# $AGENDA_DIR
# ├── {agenda-name}
# │   ├── 0000-{backlog-name}.{agenda-ext}
# │   └── {agenda-date}.{agenda-ext}
# └── {agenda-name}
#     └── {agenda-date}.{agenda-ext}
# ```
#
AGENDA_DIR=${AGENDA_DIR:-}

# The default `-e` option.
AGENDA_EXTENSION=${AGENDA_EXTENSION:-"md"}

# The default name if the `-t` option is omitted.
AGENDA_DEFAULT=${AGENDA_DEFAULT:-"agenda"}

# Command that provides the initial contents of new agenda files.
AGENDA_TEMPLATE=${AGENDA_TEMPLATE:-"__agenda_default_template"}

__usage() {
	fold -s <<-USAGE
	Usage: ${0##*/} [-bcE] [-e <extension>] [-t <name>] [<date>]
	       ${0##*/} <subcommand>

	Manage daily tasks and notes in any plain text format.

	  -b             Edit a backlog file (use the date argument as backlog name)
	  -c             Create the file if it does not exist
	  -E             Instead of editing the file, print its path to STDOUT
	  -e <extension> Specify the file extension
	  -t <name>      Specify which agenda to edit

	Subcommands:
	  edit           Edit a single agenda note file. This is the default and can be
	                 omitted.
	  list           List a range of agenda note files.
	USAGE
}

__version() {
	echo "${0##*/} version 0.0.2"
}

__main() {
	case $* in
		"--help") __usage && return ;;
		"--version") __version && return ;;
	esac

	if [ -z "$AGENDA_DIR" ]; then
		if type xdg-user-dir >/dev/null 2>&1; then
			AGENDA_DIR="$(xdg-user-dir DOCUMENTS)/agenda"
		else
			AGENDA_DIR="$HOME/.agenda"
		fi
	fi

	# Subcommand
	case ${1:-} in
		"list"|"ls") __list "${@:2}" ;;
		"edit") __edit "${@:2}" ;;
		*) __edit "$@" ;;
	esac
}

__edit_usage() {
	fold -s <<-USAGE
	Usage: ${0##*/} edit [-bcE] [-e <extension>] [-t <name>] [<date>]

	Edit a single agenda note file.

	  -b             Edit a backlog file (use the date argument as backlog name)
	  -c             Create the file if it does not exist
	  -E             Instead of editing the file, print its path to STDOUT
	  -e <extension> Specify the file extension
	  -t <name>      Specify which agenda to edit
	USAGE
}

__edit() {
	case $* in
		"--help") __edit_usage && return ;;
	esac

	local opt_b opt_c opt_E opt_e opt_t
	opt_b="no"
	opt_c="no"
	opt_E="no"
	opt_e="$AGENDA_EXTENSION"
	opt_t="$AGENDA_DEFAULT"
	while getopts 'bcEe:t:' opt; do
		case $opt in
			b)
				opt_b="yes"
				;;
			c)
				opt_c="yes"
				;;
			E)
				opt_E="yes"
				;;
			e)
				opt_e=$OPTARG
				;;
			t)
				opt_t=$OPTARG
				;;
			*)
				__edit_usage && return 1
				;;
		esac
	done
	shift $(( OPTIND - 1 ))

	if [ $# -eq 0 ]; then
		if [ "$opt_b" = "yes" ]; then
			set -- "backlog"
		else
			set -- "today"
		fi
	fi

	local base ext slug file
	if [ "$opt_b" = "yes" ]; then
		base="0000-$(__slugify "$*")"
	else
		base=$(date -d "$*" +%F)
	fi
	ext=$opt_e
	slug=$(__slugify "$opt_t")
	file="$AGENDA_DIR/$slug/$base.$ext"

	# Existing files may overwrite the `-e` option.
	local exists
	for exists in "${file%."$ext"}".*; do
		if [ -e "$exists" ] && [ "$file" != "$exists" ]; then
			echo "${0##*/}: ignoring '$ext' extension: '$exists' already exists" >&2
			ext="${exists##*.}"
			file="$exists"
		fi
	done

	# These values are (potentially) used by the AGENDA_EDITOR and AGENDA_TEMPLATE
	# processes.
	AGENDA_FILE=$file
	AGENDA_DATE=$base
	AGENDA_NAME=$opt_t
	AGENDA_SLUG=$slug
	AGENDA_FILE=$file
	AGENDA_LAST=$(__agenda_last "$file" "$opt_t")

	# Make shellcheck happy...
	export AGENDA_FILE AGENDA_DATE AGENDA_NAME AGENDA_SLUG AGENDA_FILE AGENDA_LAST

	if ! [ -f "$file" ]; then
		if [ "$opt_c" = "yes" ]; then
			__agenda_create "$file" "$opt_b" "$opt_t" "$slug" "$base"
		else
			echo "${0##*/}: cannot access '$file': No such file" >&2
			return 2
		fi
	fi

	if [ "$opt_E" = "no" ]; then
		exec $AGENDA_EDITOR "$file"
	else
		echo "$file"
	fi
}

__list_usage() {
	fold -s <<-USAGE
	Usage: ${0##*/} list [-ac] [-u <date>] [-t <name>] [<date>]

	List a range of agenda note files.

	  -a        Print the files' absolute path
	  -c        Print the files' content
	  -u <date> Stop listing at <date>
	  -t <name> Specify which agenda to list
	USAGE
}

__list() {
	case $* in
		"--help") __list_usage && return ;;
	esac

	local opt opt_a opt_c opt_u opt_t
	opt_a="no"
	opt_c="no"
	opt_u="next week" # FIXME: Not portable.
	opt_t=""
	while getopts 'abcu:t:' opt; do
		case $opt in
			a)
				opt_a="yes"
				;;
			c)
				opt_c="yes"
				;;
			u)
				opt_u="$OPTARG"
				;;
			t)
				opt_t="$OPTARG"
				;;
			*)
				list_usage
				return 1
				;;
		esac
	done
	shift $(( OPTIND - 1 ))

	# TODO: Check if stdout is a file that is a terminal or a pipe that is
	#       connected to a terminal.
	local padlength
	padlength=80

	if [ $# -eq 0 ]; then
		# FIXME: Not portable.
		set -- "last week"
	fi

	local date until dir
	date=$(date -d "$*" +%F)
	until=$(date -d "$opt_u" +%F)
	if [ -n "$opt_t" ]; then
		slug=$(__slugify "$opt_t")
		dir="$AGENDA_DIR/$slug"
	else
		dir="$AGENDA_DIR"
	fi

	if ! [ -d "$dir" ]; then
		echo "${0##*/}: cannot access '$dir': Directory does not exist" >&2
		return 1
	fi

	local date_cmp until_cmp
	date_cmp="${date%%-*}${date#*-}"
	date_cmp="${date_cmp%%-*}${date_cmp#*-}"
	until_cmp="${until%%-*}${until#*-}"
	until_cmp="${until_cmp%%-*}${until_cmp#*-}"

	while read -r REPLY; do
		if ! [ -f "$REPLY" ]; then
			echo "${0##*/}: cannot access '$REPLY': File does not exist" >&2
		fi

		local file_date
		file_date="${REPLY##*/}"
		file_date="${file_date%.*}"

		local file_date_cmp
		file_date_cmp="${file_date%%-*}${file_date#*-}"
		file_date_cmp="${file_date_cmp%%-*}${file_date_cmp#*-}"

		# Agenda may allow special files that are not named by date in the
		# future.
		# https://stackoverflow.com/a/18620446
		case $file_date_cmp in
			*[!0-9]* | '') continue ;;
			*) ;;
		esac

		# This was originally written in POSIX shell. Let's keep it that way for
		# now.
		# https://unix.stackexchange.com/a/84472
		if [ "$file_date_cmp" -ge "$date_cmp" ] && [ "$file_date_cmp" -le "$until_cmp" ]; then
			local file_name
			file_name="$REPLY"
			if [ "$opt_a" = "no" ]; then
				file_name="${file_name#"$AGENDA_DIR/"}"
				file_name="${file_name%.*}"
			fi

			if [ "$opt_c" = "yes" ]; then
				printf "%*s\n" "$padlength" "[$file_name]" | tr " " "-"
				cat "$REPLY"
				echo
			else
				echo "$file_name"
			fi
		fi
	done < <(
		# Sort the paths by basename.
		find "$dir" -type f \
			| __agenda_sort_prefix \
			| sort \
			| __agenda_strip_sort_prefix
	)
}

__agenda_create() {
	local file=$1 backlog=$2 name=$3 slug=$4 date=$5

	if [ -e "$file" ]; then
		echo "${0##*/}: cannot create '$file': File already exists" >&2
		return 1
	fi

	trap 'rm -f "${tmp:-}" "${tmp_err:-}"; trap - RETURN' RETURN
	local tmp tmp_err
	tmp=$(mktemp)
	tmp_err=$(mktemp)

	if [ "$backlog" = "no" ]; then
		# Capture exit code of the template command.
		local code
		set +e
		"$AGENDA_TEMPLATE" > "$tmp" 2> "$tmp_err"
		code=$?
		set -e

		if [ $code -eq 127 ]; then
			echo "${0##*/}: cannot create '$file': template '$AGENDA_TEMPLATE' does not exist" >&2
			return 127
		fi

		if [ -s "$tmp_err" ]; then
			while read -r REPLY; do
				printf "agenda: $AGENDA_TEMPLATE: %s\n" "${REPLY#"${0}: line"*": "}" >&2
			done < "$tmp_err"
		fi

		if [ $code -gt 0 ]; then
			echo "${0##*/}: cannot create '$file': template error" >&2
			return $code
		fi
	fi

	mkdir -p "${file%/*}"
	mv "$tmp" "$file"
}

__agenda_default_template() {
	case $AGENDA_EXTENSION in
		"md")
			printf "# %s %s\n\n- [ ] " "$AGENDA_NAME" "$AGENDA_DATE"
			;;
		"txt"|"xit"|"")
			printf "%s %s\n[ ] " "$AGENDA_NAME" "$AGENDA_DATE"
			;;
		*)
			;;
	esac
}

__agenda_last() {
	local file=$1 name=$2

	[ -d "$AGENDA_DIR/$name" ] || return 0

	local last
	while read -r REPLY; do
		if [ "$REPLY" = "$file" ]; then
			break
		else
			last=$REPLY
		fi
	done < <(
		{
			echo "$file"
			find "$AGENDA_DIR/$name" -type f
		} | sort
	)

	echo "${last:-}"
}

# https://stackoverflow.com/a/49035906
__slugify() {
    echo "$1" \
        | iconv -c -t ascii//TRANSLIT \
        | sed -E "s/[~^]+//g" \
        | sed -E "s/[^a-zA-Z0-9]+/-/g" \
        | sed -E "s/^-+|-+$//g" \
        | tr "[:upper:]" "[:lower:]"
}

__agenda_sort_prefix() {
	while read -r REPLY; do
		echo "${REPLY##*/}---$REPLY"
	done
}

__agenda_strip_sort_prefix() {
	while read -r REPLY; do
		echo "${REPLY#*---}"
	done
}

__main "$@"

# vi: noet sts=4 sw=4 tw=84