#!/bin/bash
# Migrate assignments for Gitea-Issues after a Gitea2Gitea-Migration
# 2024 Benjamin Winter
set -eu

readonly PROGNAME=`/usr/bin/basename $0`
readonly PROGPATH=`echo $0 | sed -e 's,[\\/][^\\/][^\\/]*$,,'`
readonly REVISION="0.0.1-WIP"

repo=""
login_old=""
login_new=""
dry_run=true

#
# FUNCTIONS
#

print_help()
{
cat << "EOF"
PURPOSE
- Migrate assignments for Gitea-Issues after a Gitea2Gitea-Migration
    - issues must have the same ID on both systems
    - users must have the same NAME on both systems
- example
    - OLD: https://oldgitea.example.com/my_organisation/my_repository
    - NEW: https://newgitea.example.com/my_organisation/my_repository
- Typical Workflow
    1. migrate your repository from your OLD Gitea instance to your NEW one
    2. use this script to migrate the assignments

INFORMATION
- this script will start in DRY MODE by default - see --GO parameter
- this script will check the environment and stops on any error
- this script will check the OLD and NEW repository for inconsistencies
- if your titles include a ¬ character, the script may could behave funny as this i used as separator

INSTALLATION AND PREPARATION
- install
    - jq - Command-line JSON processor
    - tea: https://gitea.com/gitea/tea
- create Gitea tokens for tea
    - permissions on the OLD system:
        - user: read
        - issue: read
    - permissions on the NEW system:
        - user: read
        - issue: read and write
- set up login via tea → "tea login add --help", i.e.
    - tea login add --name OLD --url https://oldgitea.example.com --token 123456789123456789
    - tea login add --name NEW --url https://newgitea.example.com --token 123459789123456789

    USAGE
    -h | --help      print this help
    -r | --repo      required, i.e. "my_organisation/my_repository"
    -o | --login_old required, tea-id of your old login
    -n | --login_new required, tea-id of your new login
    --GO             stop dry mode
EOF
}

error_in_or_out_not_specified()
{
    echo -e "Error: --repo, --login_old and --login_new must be specified\n";
    print_help;
    exit 2
}

# @param $1 "command"	→ the command to check for
checkCommand()
{
    command -v "$1" >/dev/null 2>&1 || { echo >&2 "Command ${1} is required but it's not installed. Aborting."; exit 42; }
}

#
# PARAMETERS
#
if [[ "$@" == "" ]] ; then error_in_or_out_not_specified ; fi
TEMP=$(getopt -o h,r:o:n: --long help,GO,repo:login_old:,login_new: -n "${PROGNAME}" -- "$@")
eval set -- "${TEMP}"
while true ; do
    case "$1" in
        --help|-h)
            print_help
            exit 0
            ;;
        --repo|-r)
            repo="$2"
            shift
            ;;
        --login_old|-o)
            login_old="$2"
            shift
            ;;
        --login_new|-n)
            login_new="$2"
            shift
            ;;
        --GO)
            dry_run=false
            ;;
        --) shift ; break ;;
        *)  echo "Internal error!"
            exit 5
            ;;
    esac
    shift
done

# check required
if [[ -z "$repo" || -z "$login_old" || -z "$login_new" ]] ; then error_in_or_out_not_specified ; fi

#
# START
#
if $dry_run; then echo -e "###\n### DRY RUN - will not change anything\n###"; fi

# check commands
checkCommand tea
checkCommand jq

# get data
echo -e "\n# checking access to OLD (\"$login_old\") and NEW (\"$login_new\")"
json_old=$(tea issues list --output json --login "$login_old" --repo "$repo" --state all --fields index,assignees,title)
json_new=$(tea issues list --output json --login "$login_new" --repo "$repo" --state all --fields index,assignees,title)

# check data
readonly json_old_ids=$(echo "$json_old" | jq ".[] | .index")
readonly json_new_ids=$(echo "$json_new" | jq ".[] | .index")
if [[ "$json_old_ids" != "$json_new_ids" ]]; then
    echo >&2 "OLD repositories' ids differ from NEW repository. Aborting.";
    echo >&2 "OLD repositories' ids: $(echo "$json_old_ids" | tr '\n' ,)";
    echo >&2 "NEW repositories' ids: $(echo "$json_new_ids" | tr '\n' ,)";
    exit 3;
fi


# process data
while IFS="¬"; read -r index assignees title; do
    echo "processing issue #${index} - \"${title}\", assigned to \"${assignees}\""
done< <(echo "$json_old" | jq --raw-output '.[] | "\(.index)¬\(.assignees)¬\(.title)"')


exit 0