#!/bin/bash

src="${1?Missing source document}"
path="${2?Missing spec src path}"

domake()
{
  pdflatex -draftmode "$src" >&2
}

gendate()
{
  echo -n "$( git log -n1 --pretty=format:%ai | cut -d' ' -f1 ) "
}

domake \
  && echo -n 'id ' \
  && head -n1 taskstats.dat \
  && \
  (
    echo -n '0 ' && gendate && tail -n1 taskstats.dat \
    && git log --no-merges --pretty=format:'%at %h' -- "$path" \
    | awk '
      BEGIN {
        last=0
        now=systime()
      }

      {
        # calculate the number of days ago this was
        ago = int( ( now - $1 ) / 86400 );
        if ( ago <= last ) next;
        last = ago;
        print ago, $NF;
      }
    ' \
    | while read n h; do
      git checkout "$h" >&2 \
        && domake \
        && echo -n "-$n " \
        && gendate \
        && tail -n1 taskstats.dat \
        || { echo "Aborting data gathering."; exit 1; }
    done
  )