#!/usr/bin/env bash
# create-mr.sh "<title>" [target-branch] [source-branch] [jira-key]
#
# Creates a GitLab merge request for the current repository via the GitLab API.
# Host and project path are derived from `git remote origin` (or GITLAB_HOST),
# so no URLs are hardcoded. If a Jira key is given and TRACKER_URL/JIRA_TOKEN are
# set, the MR link is also attached to the ticket via link-mr.sh.
#
# Env:
#   GITLAB_TOKEN   (required) GitLab personal/project access token with api scope
#   GITLAB_HOST    (optional) override host, e.g. git.codelab.vc
#   MR_PUSH        (optional) 0 to skip pushing the source branch (default: push)
#   MR_DRY_RUN     (optional) 1 to print the request and exit without calling the API
#
# Examples:
#   ./create-mr.sh "Fix PROJ-123: null pointer" main
#   ./create-mr.sh "Add feature X" main feature/PROJ-42-x PROJ-42
set -euo pipefail

TITLE="${1:?usage: create-mr.sh \"<title>\" [target-branch] [source-branch] [jira-key]}"
TARGET="${2:-main}"
SOURCE="${3:-$(git rev-parse --abbrev-ref HEAD)}"
JIRA_KEY="${4:-}"

: "${GITLAB_TOKEN:?set GITLAB_TOKEN (GitLab access token with api scope)}"

# --- Refuse to open an MR *from* a protected branch (safety). ----------------
case "$SOURCE" in
	main | master | release/*)
		echo "Refusing: source branch '$SOURCE' looks protected. Create a feature branch first." >&2
		exit 1
		;;
esac

# --- Derive host and project path from the origin remote. -------------------
URL="$(git config --get remote.origin.url)"
URL="${URL%.git}"
case "$URL" in
	*://*) # scheme://[user@]host[:port]/path
		REST="${URL#*://}"
		REST="${REST#*@}"
		HOST_PORT="${REST%%/*}"
		PATH_NS="${REST#*/}"
		HOST="${HOST_PORT%%:*}"
		;;
	*@*:*) # scp-like: user@host:path
		REST="${URL#*@}"
		HOST="${REST%%:*}"
		PATH_NS="${REST#*:}"
		;;
	*)
		echo "Cannot parse origin remote URL: $URL" >&2
		exit 1
		;;
esac

HOST="${GITLAB_HOST:-$HOST}"
if [ -z "$HOST" ] || [ -z "$PATH_NS" ]; then
	echo "Could not determine GitLab host/project from origin ($URL). Set GITLAB_HOST." >&2
	exit 1
fi

# URL-encode the project path (only '/' needs encoding for a namespaced path).
PROJECT_ENC="${PATH_NS//\//%2F}"
API="https://${HOST}/api/v4/projects/${PROJECT_ENC}/merge_requests"

# --- Build request body (jq escapes; fall back to naive JSON). --------------
if command -v jq >/dev/null 2>&1; then
	BODY="$(jq -n \
		--arg s "$SOURCE" --arg t "$TARGET" --arg title "$TITLE" \
		'{source_branch:$s, target_branch:$t, title:$title, remove_source_branch:true, squash:true}')"
else
	BODY="{\"source_branch\":\"${SOURCE}\",\"target_branch\":\"${TARGET}\",\"title\":\"${TITLE//\"/\\\"}\",\"remove_source_branch\":true,\"squash\":true}"
fi

if [ "${MR_DRY_RUN:-0}" = "1" ]; then
	echo "DRY RUN"
	echo "POST ${API}"
	echo "body: ${BODY}"
	echo "would push: $([ "${MR_PUSH:-1}" = "1" ] && echo "git push -u origin ${SOURCE}" || echo "(skipped)")"
	exit 0
fi

# --- Ensure the source branch exists on the remote. -------------------------
if [ "${MR_PUSH:-1}" = "1" ]; then
	git push -u origin "$SOURCE"
fi

# --- Create the MR. ---------------------------------------------------------
RESPONSE="$(curl -fsS -X POST \
	-H "PRIVATE-TOKEN: ${GITLAB_TOKEN}" \
	-H "Content-Type: application/json" \
	-d "$BODY" "$API")"

if command -v jq >/dev/null 2>&1; then
	WEB_URL="$(printf '%s' "$RESPONSE" | jq -r '.web_url // empty')"
else
	WEB_URL="$(printf '%s' "$RESPONSE" | sed -n 's/.*"web_url":"\([^"]*\)".*/\1/p' | head -1)"
fi

if [ -z "$WEB_URL" ]; then
	echo "MR request sent, but could not parse web_url from response:" >&2
	echo "$RESPONSE" >&2
	exit 1
fi

echo "MR created: $WEB_URL"

# --- Optionally attach the MR link to the Jira ticket. ----------------------
if [ -n "$JIRA_KEY" ] && [ -n "${TRACKER_URL:-}" ] && [ -n "${JIRA_TOKEN:-}" ]; then
	"$(dirname "$0")/link-mr.sh" "$JIRA_KEY" "$WEB_URL" "$TITLE"
fi