#!/bin/bash
# SPDX-License-Identifier: MIT

set -e
set -o posix

SELF=${BASH_SOURCE[0]}
SELF_DIR="$( cd "$( dirname "$SELF" )" && pwd )"
source $SELF_DIR/cascading-pr-lib.sh

trap "rm -fr $TMPDIR" EXIT

function repo_login() {
    local direction="$1"
    local repo=${options[${direction}_repo]}
    (
	export DOT=$TMPDIR/$repo
	forgejo-curl.sh logout
	forgejo-curl.sh --token "${options[${direction}_token]}" login "${options[${direction}_url]}"
    )
}

function repo_curl() {
    local repo=$1
    shift
    DOT=$TMPDIR/$repo forgejo-curl.sh "$@"
}

function default_branch() {
    local direction=$1

    repo_curl ${options[${direction}_repo]} api_json ${options[${direction}_api]} > $TMPDIR/$direction.json
    jq --raw-output .default_branch < $TMPDIR/$direction.json
}

function exists_branch() {
    local direction=$1

    repo_curl ${options[${direction}_repo]} api_json ${options[${direction}_api]}/branches/${options[${direction}_head]} >& /dev/null
}

function delete_branch() {
    local direction=$1

    if ! $(exists_branch $direction) ; then
	log_info "branch ${options[${direction}_head]} does not exists"
	return
    fi
    repo_curl ${options[${direction}_repo]} api_json -X DELETE ${options[${direction}_api]}/branches/${options[${direction}_head]}
    log_info "branch ${options[${direction}_head]} deleted"
}

function pr_origin_comment_body() {
    echo "cascading-pr updated at ${options[destination_url]}/${options[destination_repo]}/pulls/$(pr_number destination)"
}

function comment_origin_pr() {
    cat > $TMPDIR/data <<EOF
{
  "body":"$(pr_origin_comment_body)"
}
EOF
    repo_curl ${options[origin_repo]} api_json --data @$TMPDIR/data ${options[origin_api]}/issues/${options[origin_pr]}/comments
    log_info "comment added to $(pr_url origin)"
}

function pr_destination_title() {
    echo "cascading-pr from ${options[origin_url]}/${options[origin_repo]}/pulls/${options[origin_pr]}"
}

function pr_destination_body() {
    echo "cascading-pr from ${options[origin_url]}/${options[origin_repo]}/pulls/${options[origin_pr]}"
}

function upsert_destination_pr() {
    url=$(pr_url destination)
    state=$(pr_state destination)
    if test "$url" != "null" -a "$state" = "open"; then
	log_info "an open PR already exists $url"
	return
    fi
    if ${options[destination_is_fork]} ; then
	head="$(owner ${options[destination_fork_repo]}):${options[destination_head]}"
    else
	head=${options[destination_head]}
    fi
    local title=$(pr_destination_title)
    cat > $TMPDIR/data <<EOF
{
  "title":"$(pr_destination_title)",
  "body":"$(pr_destination_body)",
  "base":"${options[destination_base]}",
  "head":"$head"
}
EOF
    retry repo_curl ${options[destination_repo]} api_json --data @$TMPDIR/data ${options[destination_api]}/pulls > $TMPDIR/destination-pr.json
    log_info "PR created $(pr_url destination)"
}

function close_pr() {
    local direction=destination

    if test "$(pr_state ${direction})" = "open"; then
	log_info "closing $(pr_url ${direction})"
	local number=$(pr_number $direction)
	repo_curl ${options[${direction}_repo]} api_json -X PATCH --data '{"state":"closed"}' ${options[${direction}_api]}/issues/$number
	delete_branch ${direction}
    else
	log_info "no open PR found"
    fi
}

function pr_get_origin() {
    repo_curl ${options[origin_repo]} api_json ${options[origin_api]}/pulls/${options[origin_pr]} > $TMPDIR/origin-pr.json
}

function pr_get_destination() {
    local title=$(pr_destination_title)
    repo_curl ${options[destination_repo]} api --get --data state=open --data type=pulls --data-urlencode q="$title" ${options[destination_api]}/issues | jq --raw-output .[0]  > $TMPDIR/destination-pr.json
}

function pr_get() {
    local direction=$1
    if ! test -f $TMPDIR/${direction}-pr.json; then
	pr_get_$direction
    fi
}

function pr()  {
    cat $TMPDIR/$1-pr.json
}

function pr_state() {
    pr_get $1
    pr $1 | jq --raw-output .state
}

function pr_url() {
    pr_get $1
    pr $1 | jq --raw-output .url
}

function pr_number() {
    pr_get $1
    pr $1 | jq --raw-output .number
}

function pr_merged() {
    pr_get $1
    pr $1 | jq --raw-output .merged
}

function pr_from_fork() {
    pr_get $1
    pr $1 | jq --raw-output .head.repo.fork
}

function git_clone() {
    local direction=$1 url=$2

    if ! test -d $TMPDIR/$direction; then
	git -c credential.helper="store --file=$TMPDIR/$direction.git-credentials" clone $url $TMPDIR/$direction
    fi
    (
	cd $TMPDIR/$direction
	git config credential.helper "store --file=$TMPDIR/$direction.git-credentials"
	git config user.email cascading-pr@example.com
	git config user.name cascading-pr
    )
}

function git_checkout() {
    local direction=$1 ref="$3"
    local remote=origin

    (
	cd $TMPDIR/$direction
	if [[ "$ref" =~ ^refs/ ]] ; then
	    git fetch ${remote} +$ref:$ref
	else
	    ref=${remote}/$ref
	fi
	git checkout -b prbranch $ref
    )
}

function git_remote() {
    local direction=$1 remote=$2 url=$3

    (
	cd $TMPDIR/$direction
	git remote add $remote $url
    )
}

function git_reset_branch() {
    local direction=$1 remote=$2 branch=$3
    (
	cd $TMPDIR/$direction
	if git ls-remote --exit-code --heads ${remote} $branch ; then
	    git fetch --quiet ${remote} $branch
	    git reset --hard ${remote}/$branch
	fi
    )
}

function sha_pushed() {
    local direction=$1
    if test -f $TMPDIR/$direction.sha ; then
	cat $TMPDIR/$direction.sha
    fi
}

function push() {
    local direction=$1 remote=$2 branch=$3

    (
	cd $TMPDIR/$direction
	git add .
	if git commit -m 'cascading-pr update'; then
	    git push --force ${remote} prbranch:$branch
	    git rev-parse HEAD > ../$direction.sha
	    log_info "pushed"
	else
	    log_info "nothing to push"
	fi
    )
}

function wait_destination_ci() {
    local sha="$1"
    local repo_api=${options[destination_url]}/api/v1/repos/${options[destination_repo]}
    wait_success $repo_api $sha
}

function upsert_fork() {
    if repo_curl ${options[destination_repo]} api_json ${options[destination_fork_api]} > $TMPDIR/fork.json 2> /dev/null ; then
	if test "$(jq --raw-output .fork)" != true ; then
	    log_error "the destination fork already exists but is not a fork ${options[destination_fork]}"
	    return 1
	fi
	local forked_from_repo=$(jq --raw-output .parent.full_name)
	if test "$forked_from_repo" != "${options[destination_repo]}" ; then
	    log_error "${options[destination_fork]} must be a fork of ${options[destination_repo]} but is a fork of $forked_from_repo instead"
	    return 1
	fi
    else
	local fork_owner=$(owner ${options[destination_fork]})
	local data="{}"
	if repo_curl ${options[destination_repo]} api_json ${options[destination_url]}/api/v1/orgs/${fork_owner} >& /dev/null ; then
	    data='{"organization":"'$fork_owner'"}'
	fi
	repo_curl ${options[destination_repo]} api_json --data "$data" ${options[destination_url]}/api/v1/${options[destination_repo]}/forks
    fi
}

function checkout() {
    #
    # origin
    #
    git_clone origin ${options[origin_clone]}
    git_checkout origin "${options[origin_head]}"

    #
    # destination
    #
    git_clone destination ${options[destination_clone]}
    git_checkout destination "${options[destination_base]}"

    #
    # fork
    #
    local head_remote=origin
    if ${options[destination_is_fork]} ; then
	upsert_fork
	git_remote destination fork ${options[destination_fetch_fork]}
	head_remote=fork
    fi
    git_reset_branch destination $head_remote "${options[destination_head]}"
}

function update() {
    (
	local update=${options[update]}
	if ! [[ "$update" =~ ^/ ]] ; then
	    local d
	    if $(pr_from_fork origin); then
		local default_branch=$(default_branch origin)
		log_info "PR is from a forked repository, using the default branch $default_branch to obtain the update script"
		d=$TMPDIR/update
		git -C $TMPDIR/origin worktree add $d $default_branch
	    else
		d=$TMPDIR/origin
	    fi
	    update=$d/$update
	fi
	cd $TMPDIR
	$update $TMPDIR/destination $TMPDIR/destination-pr.json $TMPDIR/origin $TMPDIR/origin-pr.json
    )
    local remote_head=origin
    if ${options[destination_is_fork]} ; then
	remote_head=fork
    fi
    push destination $remote_head ${options[destination_head]}
}

function set_clone() {
    local direction=$1
    local token=${options[${direction}_token]}

    if [[ "$token" =~ ^@ ]] ; then
	local file=${token##@}
	(
	    echo -n ${options[${direction}_scheme]}://any:
	    cat $file
	    echo @${options[${direction}_host_port]}/${options[${direction}_repo]}
	) > $TMPDIR/$direction.git-credentials
    else
	echo ${options[${direction}_scheme]}://any:${options[${direction}_token]}@${options[${direction}_host_port]}/${options[${direction}_repo]}  > $TMPDIR/$direction.git-credentials
    fi
    options[${direction}_clone]=${options[${direction}_scheme]}://${options[${direction}_host_port]}/${options[${direction}_repo]}
}

function fork_sanity_check() {
    local fork_repo=${options[destination_fork_repo]}
    local repo=${options[destination_repo]}
    if test "$(repository $fork_repo)" != "$(repository $repo)"; then
	echo "$repo and its fork $fork_repo must have the same repository name (see https://codeberg.org/forgejo/forgejo/issues/1707)"
	return 1
    fi
}

function finalize_options() {
    options[origin_api]=${options[origin_url]}/api/v1/repos/${options[origin_repo]}
    options[origin_scheme]=$(scheme ${options[origin_url]})
    options[origin_host_port]=$(host_port ${options[origin_url]})
    set_clone origin
    options[origin_head]=refs/pull/${options[origin_pr]}/head

    options[destination_api]=${options[destination_url]}/api/v1/repos/${options[destination_repo]}
    options[destination_scheme]=$(scheme ${options[destination_url]})
    options[destination_host_port]=$(host_port ${options[destination_url]})
    set_clone destination
    options[destination_base]=${options[destination_branch]}
    : ${options[prefix]:=${options[origin_repo]}}
    options[destination_head]=${options[prefix]}-${options[origin_pr]}

    if test "${options[destination_fork_repo]}"; then
	fork_sanity_check
	options[destination_is_fork]=true
	options[destination_fork_api]=${options[destination_url]}/api/v1/repos/${options[destination_fork_repo]}
	options[destination_is_fork]=false
    fi

    : ${options[close_merge]:=false}
}

function run() {
    local state=$(pr_state origin)

    repo_login origin
    repo_login destination

    case "$state" in
	open)
	    log_info "PR is open, update or create the cascade branch and PR"
	    checkout
	    update
	    local sha=$(sha_pushed destination)
	    if test "$sha" ; then
		upsert_destination_pr
		comment_origin_pr
		wait_destination_ci "$sha"
	    fi
	    ;;
	closed)
	    if "$(pr_merged origin)"; then
		if "${options[close_merge]}" ; then
		    log_info "PR is merged, close the cascade PR and remove the branch"
		    close_pr
		else
		    log_info "PR was merged, update the cascade PR"
		    pr_get origin
		    pr_get destination
		    checkout
		    update
		fi
	    else
		log_info "PR is closed, close the cascade PR and remove the branch"
		close_pr
	    fi
	    ;;
	*)
	    log_info "state '$state', do nothing"
	    ;;
    esac
}

function main() {
    while true; do
	case "$1" in
	    --verbose)
		shift
		verbose
		;;
	    --debug)
		shift
		debug
		;;
	    --origin-url)
		shift
		options[origin_url]=$1
		shift
		;;
	    --origin-repo)
		shift
		options[origin_repo]=$1
		shift
		;;
	    --origin-token)
		shift
		options[origin_token]=$1
		shift
		;;
	    --origin-pr)
		shift
		options[origin_pr]=$1
		shift
		;;
	    --destination-url)
		shift
		options[destination_url]=$1
		shift
		;;
	    --destination-repo)
		shift
		options[destination_repo]=$1
		shift
		;;
	    --destination-fork-repo)
		shift
		options[destination_fork_repo]=$1
		shift
		;;
	    --destination-token)
		shift
		options[destination_token]=$1
		shift
		;;
	    --destination-branch)
		shift
		options[destination_branch]=$1
		shift
		;;
	    --update)
		shift
		options[update]=$1
		shift
		;;
	    --prefix)
		shift
		options[prefix]=$1
		shift
		;;
	    --close-merge)
		shift
		options[close_merge]=$1
		shift
		;;
	    *)
		finalize_options
		"${1:-run}"
		return 0
		;;
	esac
    done
}

dependencies

if echo "${@}" | grep --quiet -e '--debug' ; then
    main "${@}"
else
    stash_debug "${@}"
fi