#!/usr/bin/env bash

# Bash completion script for the agenda(1) script.

# TODO: Maybe its easier to add an api to the agenda script to query for the
#       available -t option values?
if [ -z "$AGENDA_DIR" ]; then
	AGENDA_DIR="${XDG_DATA_HOME:-"$HOME/.local/share"}/agenda"
fi

AGENDA_COMP_DATE_MOD=("next" "last")
AGENDA_COMP_DATE_UNIT=("day" "week" "month" "year")
AGENDA_COMP_DATE_DAY=("monday" "tuesday" "wednesday" "thursday" "friday" "saturday" "sunday")
AGENDA_COMP_DATE_REL=("yesterday" "today" "tomorrow")

AGENDA_COMP_DATE=(
	"${AGENDA_COMP_DATE_MOD[@]}" 
	"${AGENDA_COMP_DATE_UNIT[@]}" 
	"${AGENDA_COMP_DATE_DAY[@]}" 
	"${AGENDA_COMP_DATE_REL[@]}"
)

__agenda_comp() {
	# Pointer to current and last completion words.
	local cur last

	cur=${COMP_WORDS[COMP_CWORD]}
	last=${COMP_WORDS[COMP_CWORD - 1]}

	# All subcommands take a date (or parts of a date) as their final arguments.
	if __agenda_comp_is_date_word "${COMP_WORDS[-2]}"; then
		return
	fi

	if __agenda_comp_is_date_mod "$last"; then
		local words=("${AGENDA_COMP_DATE_UNIT[@]}" "${AGENDA_COMP_DATE_DAY[@]}")
		mapfile -t COMPREPLY < <(compgen -W "${words[*]}" -- "$cur")
		return
	fi

	case ${COMP_WORDS[1]} in
		"edit")
			mapfile -t COMPREPLY < <(__agenda_comp_edit "$last" "$cur")
			;;
		"list"|"ls")
			mapfile -t COMPREPLY < <(__agenda_comp_list "$last" "$cur")
			;;
		*)
			if (( COMP_CWORD == 1 )); then
				local dates
				mapfile -t dates < <(__agenda_comp_iso_date "$cur")

				local words=(
					"edit"
					"list"
					"${dates[@]}"
					"${AGENDA_COMP_DATE[@]}"
					"${AGENDA_COMP_DATE_DAY[@]}"
				)

				mapfile -t COMPREPLY < <(compgen -W "${words[*]}" -- "${COMP_WORDS[1]}")
			else
				# The "edit" subcommand is implicit.
				mapfile -t COMPREPLY < <(__agenda_comp_edit "$last" "$cur")
			fi
			;;
	esac
}
complete -F __agenda_comp agenda

__agenda_comp_edit() {
	local last="$1" cur="$2"

	case $last in
		"-"*"t")
			compgen -W "$(__agenda_comp_names)" -- "$cur"
			;;
		*)
			__agenda_comp_opt "c" "$cur"
			__agenda_comp_opt "E" "$cur"
			__agenda_comp_opt "t" "$cur"

			compgen -W "${AGENDA_COMP_DATE[*]} $(__agenda_comp_iso_date "$cur")" -- "$cur"
			;;
	esac
}

__agenda_comp_list() {
	local last="$1" cur="$2"

	case $last in
		# TODO: Somehow complete date wrapped in a string?
		"-"*"u")
			local year
			year=$(printf '%(%Y)T' -1)
			compgen -W "$(__agenda_comp_iso_date "$cur" "$year")" -- "$cur"
			;;
		"-"*"t")
			compgen -W "$(__agenda_comp_names)" -- "$cur"
			;;
		*)
			__agenda_comp_opt "a" "$cur"
			__agenda_comp_opt "c" "$cur"
			__agenda_comp_opt "u" "$cur"
			__agenda_comp_opt "t" "$cur"

			compgen -W "${AGENDA_COMP_DATE[*]} $(__agenda_comp_iso_date "$cur")" -- "$cur"
			;;
	esac
}

__agenda_comp_is_date_mod() {
	[[ $last == "next" ]] || [[ $last == "last" ]] || [[ $last =~ ^[-+]?[0-9]+$ ]]
}

__agenda_comp_is_date_word() {
	local word words=(
		"${AGENDA_COMP_DATE_DAY[@]}"
		"${AGENDA_COMP_DATE_UNIT[@]}"
		"${AGENDA_COMP_DATE_REL[@]}"
	)
	for word in "${words[@]}"; do
		if [[ $1 == "$word" ]]; then
			return 0
		fi
	done

	if [[ $1 =~ ^[0-9]{4}-[0-9]{2}-[0-9]{2}$ ]]; then
		return 0
	fi

	return 1
}

__agenda_comp_names() {
	local dir
	for dir in "$AGENDA_DIR"/*; do
		if [ -e "$dir" ]; then
			echo "${dir##*/}"
		fi
	done
}

# TODO: Complete years only without appending a space on completion (If
#       possible, idk)?
__agenda_comp_iso_date() {
	local year month day

	if [[ $1 =~ ^[0-9]{4}-? ]]; then
		year=${1%%-*}
	elif [[ -n ${2:-} ]]; then
		year=$2
	else
		return
	fi

	for month in {1..12}; do
		case $month in
			1|3|5|7|8|10|12)
				for day in {1..31}; do
					printf "%04d-%02d-%02d\n" "$year" "$month" "$day"
				done
				;;
			4|6|9|11)
				for day in {1..30}; do
					printf "%04d-%02d-%02d\n" "$year" "$month" "$day"
				done
				;;
			2)
				# TODO: Leap years.
				for day in {1..28}; do
					printf "%04d-%02d-%02d\n" "$year" "$month" "$day"
				done
				;;
		esac
	done
}

__agenda_comp_opt() {
	local regex="^.*[[:space:]]-.*$1.*.*$"
	if ! [[ $COMP_LINE =~ $regex ]]; then
		compgen -W "-$1" -- "$2"
	fi
}

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