#!/bin/bash
# Migrate assignments for Gitea-Issues after a Gitea2Gitea-Migration
# 2024 MILA, Benjamin Winter <winterb+mila@uni-greifswald.de>
#
# errors
# 1     parameter error
# 2     repository-check error
# 5     internal error
# 42    command cannot be found
set -eu

readonly PROGNAME=`/usr/bin/basename $0`
readonly PROGPATH=`echo $0 | sed -e 's,[\\/][^\\/][^\\/]*$,,'`
readonly REVISION="1.5.0"

repo=""         # the OLD repo
transfer=""     # the NEW repo
login_old=""
login_new=""
dry_run=true
wait_time=0.25
use_colour=true

#
# FUNCTIONS
#
print_help ()
{
echo "--- $PROGNAME $REVISION"
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
    - users must have the right to be assigned 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
    - issue-ids are checked; titles are not checked
    - assignments in new repo are checked
- the --wait time slows down the script to reduce e-mail-sending-speed
- Troubleshooting
    - "Error: could not edit issue:"
        - please check, if the assigned person(s) have the right to be assigned (are they in the Organisation? Collaborators?)
    - "Error: The target couldn't be found."
        - please check, if the --repo is the same for OLD and NEW

INSTALLATION AND PREPARATION
- install
    - jq  - Command-line JSON processor - https://github.com/stedolan/jq
    - tea - Command line tool to interact with Gitea - 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
    SWITCHES
    -h | --help             print this help
    -c | --colour | --color disable colour output
    --GO                    stop dry mode

    PARAMETERS
    -r | --repo             required, i.e. "my_organisation/my_repository"
    -t | --transfer         optional, if the new repo has another organisation / name
                              if not set transfer is set to "repo"
    -o | --login_old        required, tea-id of your old login
    -n | --login_new        required, tea-id of your new login
    -w | --wait             wait time in s between issue handling (default 0.25)
EOF
}

error_in_or_out_not_specified ()
{
    echo -e "Error: --repo, --login_old and --login_new must be specified\n";
    print_help;
    exit 1
}

# @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; }
}

# collects all data from the given gitea instance+repo,
# uses pagination to really get all data (limit may be set by the server)
# get_all_data_from_gitea "$login_old" "$repo"
get_all_data_from_gitea ()
{
    local readonly l="$1"
    local readonly r="$2"

    local _collect=""
    local _page=1
    while true; do
        # get data from repo and remove [ and ]
        local _tmp=$(tea issues list --output json --login "$l" --repo "$r" --state all --limit 100 --fields index,author,assignees --page $_page | sed 's/\[//g' | sed 's/\]//g')
        if [[ $(echo "[$_tmp]" | jq length) -eq 0 ]]; then
            break
        fi
        if [[ -z "$_collect" ]] then
            _collect="$_tmp"
        else
            _collect="$_collect,$_tmp"
        fi
        _page=$(($_page+1));
    done
    echo "[$_collect]"
    return 0;
}

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

if [[ "$transfer" == "" ]]; then
    transfer="$repo"
fi

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

#
# START
#
if $dry_run; then
    t="###\n### DRY RUN - will not change anything\n###"
    if [ $use_colour = true ]; then
        echo -e "\e[1m\e[38;5;214m$t\e[0m"
    else
        echo -e "$t"
    fi
fi

# check commands
checkCommand tea
checkCommand jq
checkCommand sort
checkCommand tr

# check access and get data
echo "# checking access to OLD (\"$login_old\") and NEW (\"$login_new\")"

readonly json_old=$(get_all_data_from_gitea "$login_old" "$repo")
readonly json_new=$(get_all_data_from_gitea "$login_new" "$transfer")

echo "# running consistency checks"
readonly json_old_ids=$(echo "$json_old" | jq ".[] | .index" | sort -n)
readonly json_new_ids=$(echo "$json_new" | jq ".[] | .index" | sort -n)
# check if issues
if [[ "$json_old_ids" == "" || "$json_new_ids" == "" ]]; then echo >&2 "OLD and/or NEW repo contains no issues. Aborting."; exit 2; fi
# check same issues
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 2;
fi
# check if NEW.assignments are empty
readonly json_new_assignments=$(echo "$json_new" | jq --join-output ".[] | .assignees" )
if [[ "$json_new_assignments" != "" ]]; then echo >&2 "NEW repo already contains issues with assignments. Aborting."; exit 2; fi


# process data
echo "# processing data"
while IFS="¬"; read -r index author assignees; do
    assignees=$(echo "$assignees" | tr ' ' ,)

    echo -n "… #$index - by \"$author\" assigned to \"$assignees\""

    # comment for the original author
    if [ $dry_run = false ]; then
        echo "migrator: this issue was created by @$author and will be assigned to '$assignees'" | tea comment --login "$login_new" --repo "$transfer" "$index" >/dev/null
    fi

    # assignment
    t="OK"
    if [[ -n $assignees ]]; then
        if [ $dry_run = false ]; then
            tea issue edit --login "$login_new" --repo "$transfer" --add-assignees "$assignees" "$index" >/dev/null
        fi
    else
        t="OK (no assignee)"
    fi
    if [ $use_colour = true ]; then
        echo -e " → \e[1m\e[48;5;22m$t\e[0m"
    else
        echo " → $t"
    fi

    sleep $wait_time

done< <(echo "$json_old" | jq --raw-output '.[] | "\(.index)¬\(.author)¬\(.assignees)"')

if $dry_run; then
    t="###\n### DRY RUN - nothing changed\n###"
    if [ $use_colour = true ]; then
        echo -e "\e[1m\e[38;5;214m$t\e[0m"
    else
        echo -e "$t"
    fi
fi


echo "# done"
exit 0