#! /usr/bin/env bash

# Mirror repositories. For example:
#
# mrrepo -s git.example.org /var/scm
#
# Will first download (via http or https if -s specified) the manifest file
# from git.example.org which should list all publicly available repositories.
# It will then mirror each repository in /var/scm using the git protocol.
#
# -v
#  Run verbose.
#
# -s
#  Use https rather than http to download the manifest (git protocol is still
#  used for mirroring).
#
# Notes:
#   - needs curl
#   - run from cron as user scm (which belongs to the group scm).
#
usage="usage: $0 [-v] [-s] <host> <path>"

owd=`pwd`
trap "{ cd $owd; exit 1; }" ERR
set -o errtrace # Trap in functions.

function info () { echo "$*" 1>&2; }
function error () { info "$*"; exit 1; }

prot=http
host=
path=
verb=0

while [ $# -gt 0 ]; do
  case $1 in
    -v)
      verb=1
      shift
      ;;
    -s)
      prot=https
      shift
      ;;
    *)
      if [ -z "$host" ]; then
	host=$1
      elif [ -z "$path" ]; then
	path=$1
      else
	error "$usage"
      fi
      shift
      ;;
  esac
done

if [ -z "$host" -o -z "$path" ]; then
  error "$usage"
fi

if [ ! -d "$path" ]; then
  error "$path is not a directory"
fi

cd $path

curl_ops="-f"              # Fail on HTTP errors.
curl_ops+=" --max-time 30" # Finish in 30 seconds.

if [ $verb -ge 1 ]; then
  curl_ops+=" --progress-bar"
else
  curl_ops+=" -s -S" # Silent but show errors.
fi

function fetch () # <url> [<curl-options>]
{
  local u=$1; shift

  if [ $verb -ge 1 ]; then
    info "curl $curl_ops $* $u"
  fi

  curl $curl_ops $* $u
}

fetch $prot://$host/manifest -z manifest -o manifest

new=()
while read r || [ -n "$r" ]; do
  new+=("$r")
done <manifest

# Find all existing repositories (directories that end with .git).
#
old=(`find . -type d -name '*.git' -print -prune | sed -e 's%^./%%' -`)

git_ops=
if [ $verb -eq 0 ]; then
  git_ops+="-q"
fi

for r in ${new[@]}; do
  if [ -d $r ]; then
    if [ -z "$(ls -A $r)" ]; then
      rm -r $r
    fi
  fi
  if [ ! -d $r ]; then
    if [ $verb -ge 1 ]; then
      info "new repository $r in manifest, cloning"
      info "git clone $git_ops --mirror git://$host/$r $r"
    fi
    mkdir -p $r
    git clone $git_ops --mirror git://$host/$r $r

    # Also copy the description file.
    #
    fetch $prot://$host/$r/description -o $r/description
  else
    if [ $verb -ge 1 ]; then
      info "existing repository $r, fetching"
      info "git -C $r fetch $git_ops --tags"
    fi
    git -C $r fetch $git_ops --prune --tags
  fi
done

# Remove old repositories.
#
for o in ${old[@]}; do
  for n in ${new[@]}; do
    if [ $o = $n ]; then
      o=
      break
    fi
  done

  if [ -n "$o" ]; then
    if [ $verb -ge 1 ]; then
      info "repository $o is no longer in manifest, removing"
    fi
    rm -rf $o
  fi
done

cd $owd