#!/usr/bin/env bash

# annex-ec: Use erasure codes for more efficient storage use in git-annex
# Copyright (C) 2026  Scott Worley

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.

set -euo pipefail

die() {
  echo "$*" >&2
  exit 1
}

find_recovery_set_files() {
  local found
  found=false
  recovery_set_files=()
  while IFS= read -r line;do
    if [[ "$line" == ' '* ]];then
      recovery_set_files+=( "${line# }" )
      if [[ "${line# }" == "$1" ]];then
        found=true
      fi
    else
      if $found;then
        break
      fi
      recovery_set_name=$line
      recovery_set_files=()
    fi
  done < ec/.meta
  if ! $found;then
    die "Could not find a recovery set containing file $1"
  fi
}

while [[ "$1" == -- ]];do shift; done

for target;do
  if [[ -e "$target" ]];then continue; fi
  set +e
  git annex get "$target"
  set -e
  if [[ -e "$target" ]];then continue; fi

  find_recovery_set_files "$target"

  set +e
  git annex get "${recovery_set_files[@]}" ec/"$recovery_set_name"*
  set -e

  # par2 doesn't like directory structure, so we work from a temp dir where we can flatten everything
  srcdir=$PWD
  flat="$(mktemp -d)"
  pushd "$flat"

    for f in "${recovery_set_files[@]}";do
      ln -s "$srcdir"/"$f" .
    done
    ln -s "$srcdir"/ec/"$recovery_set_name"* .

    # We have to remove the broken symlinks or par2 gets confused trying to write to them
    find -L . -type l -exec rm -v {} +

    par2 r -- *.par2

  popd
  for f in "${recovery_set_files[@]}";do
    git annex reinject "$flat"/"$(basename "$f")" "$f"
  done
done