#!/bin/bash
shopt -s inherit_errexit
set -euo pipefail
IFS=$'\n\t'
# set -x
# export PS4=':.$LINENO:'

# ----------------------------------------------------------------------

stop_task() {
    HM=`date +%H:%M`; perl -i -pe "s/\t_____\t/\t$HM\t/" $FILE
}

add_task() {
    printf "%s\t%s\t%s\t%s\t%s\n" "`date -I`" "`date +%H:%M`" "_____" "$tag" "$text" >> $FILE
}

f1_help() {
    cat <<EOF | less -c
Help for "track my time"

You can access this help at any time by hitting F1.

*   "Currently running task": a task is "running" if the second HH:MM field is
    just "_____".  At most one task can be running at any time.  If no task is
    running, it means you're "off the clock" (e.g., at end of day).

*   F7 creates a new task with whatever you typed into the fzf query field.
    The first word is considered a "TAG" and the rest is "text".  Any task
    previously marked as running is given an end time to mark it as stopped.

*   ENTER on a stopped task resumes it.  As with F7, any previously running
    task is marked stopped.

*   ENTER on a running task stops it.  Now you're off the clock (nothing is
    running).

*   The preview window shows two sets of tag-wise totals and grand totals:

    *   one for the date on the current line, filtered by the fzf query string
        if you typed one in
    *   one for all *selected* rows (or current row if you did not select any)

    REMINDER: multi-select using TAB and "select all" using Ctrl-A are enabled.

*   F4 to change text, fix timestamps, add notes and comments, etc., in your
    \$EDITOR.  Tmt only looks at lines starting with YYYY-MM (e.g., 2021-01);
    everything else is ignored so you can type in whatever you want!

    *   WARNING: there is NO ERROR CHECKING on dates and times!
    *   WARNING: don't remove the hard tabs separating the fields on the lines
        that tmt *does* care about :)

Caveat:

-   doesn't support tasks crossing midnight; if you *really* need it let me know

EOF
}

total() {
    # this takes multiple lines of stdin and produces tag-wise totals, and a grand total
    perl -MTime::Piece -lanE '
        BEGIN {
            printf "--- %s ---\n", +shift;
            @ARGV = ();     # actual computation only uses STDIN
        }
        $F[2] = localtime->strftime("%H:%M") if /_____/;
        $count++;
        ($sh, $sm, $eh, $em) = split /:/, "$F[1]:$F[2]";
        $diff = $eh*60+$em - $sh*60-$sm;
        $sum+=$diff;
        $sum{$F[3]}+=$diff;
        sub hhmm { $mm=shift; return sprintf "%02d:%02d", int($mm/60), $mm%60; }
        END {
            say "$_\t" . hhmm($sum{$_}) for sort keys %sum;
            printf "TOTAL:\t%s from %d entries\n\n", hhmm($sum), $count;
        }' "$@" |
    less -c
}

f7_new() {
    stop_task
    cat <&3 > /dev/null             # flush rest of output from fzf
    if [[ "$*" =~ " " ]]; then
        tag="${*%% *}"
        text="${*#* }"
        add_task
    else
        echo "need a TAG word and some TEXT, separated by at least one space" | less
        return 0
    fi
}

enter_stop_start() {
    # read line.  If line is a running task (i.e., contains "_____"), just stop it.
    # otherwise it's a different line (task), so stop the *running* task, then restart the selected task
    # (i.e., take fields 5 and 6 into tag and text and start it)
    IFS= read -r -u3 l
    stop_task
    if [[ $l =~ _____ ]]
    then
        :
    else
        tag=$(echo "$l" | cut -f4)
        text=$(echo "$l" | cut -f5)
        add_task
    fi
}

# ----------------------------------------------------------------------

FILE=time.tsv
[[ -f $FILE ]] || {
    echo "DATE      	START	END  	TAG   	TEXT" > $FILE
    f1_help
}

# ----------------------------------------------------------------------

export -f total
# this function is called within 'preview' so we need it exported

query=''
while :
do
    {
        IFS= read -r -u3 query
        IFS= read -r -u3 key
        case $key in
            f1 )
                f1_help ;;
            f4 )
                IFS= read -r -u3 line
                line=${line//\//\\/}
                ${EDITOR:-vim} $FILE "+/\\M$line" ;;
            f5 )
                continue ;;
            f7 )
                f7_new "$query"
                query='' ;;
            f10 )
                break ;;
            *  )
                # "ENTER"
                enter_stop_start ;;
        esac
    } 3< <( grep -E -e ^DATE -e '^[0-9]{4}-[0-9]{2}' $FILE | fzf -d$'\t' --multi --tac \
        --print-query \
        --query="$query" \
        --header-lines=1 \
        --header="ENTER:stop/start, F1:help, F5:refresh, F7:new, F10:quit" \
        --bind ctrl-a:select-all --expect=f1,f4,f5,f7,f10 \
        --preview="grep ^{1} $FILE | fzf -f {q} -e +s | bash -c 'total \"totals for {1} (possibly filtered by fzf query)\"';
                  printf '%s\n' {+} | bash -c 'total \"totals for selected tasks or current task only\"'" \
        --preview-window=top:50% )
done