#!/bin/bash
#
# Bulk-migrate every GitLab project into Forgejo with full data
# (code, issues, merge requests, labels, milestones, releases, wiki).
#
# Runs both forges in parallel — GitLab is only read, never modified.
#
# Usage:
#   export GITLAB_URL=https://gitlab.nasarek.dev
#   export GITLAB_TOKEN=glpat-xxxxxxxx          # scopes: read_api, read_repository
#   export FORGEJO_URL=https://git.nasarek.dev
#   export FORGEJO_TOKEN=xxxxxxxx               # Forgejo app token, repo + org scope
#   export FORGEJO_OWNER=root                   # target user/org that will own the repos
#   ./migrate-from-gitlab.sh [--dry-run]
#
set -euo pipefail

DRY_RUN=false
[ "${1:-}" = "--dry-run" ] && DRY_RUN=true

: "${GITLAB_URL:?set GITLAB_URL}"
: "${GITLAB_TOKEN:?set GITLAB_TOKEN}"
: "${FORGEJO_URL:?set FORGEJO_URL}"
: "${FORGEJO_TOKEN:?set FORGEJO_TOKEN}"
: "${FORGEJO_OWNER:?set FORGEJO_OWNER (target user/org)}"

command -v jq >/dev/null || { echo "jq is required"; exit 1; }

# Resolve the Forgejo owner's numeric uid (repos/migrate needs repo_owner name + uid).
OWNER_UID=$(curl -fsS -H "Authorization: token ${FORGEJO_TOKEN}" \
  "${FORGEJO_URL}/api/v1/users/${FORGEJO_OWNER}" | jq -r '.id')
echo "Target owner: ${FORGEJO_OWNER} (uid=${OWNER_UID})"

migrate_one() {
  local clone_url="$1" name="$2" private="$3" desc="$4"
  echo "==> ${name}  (private=${private})"
  if $DRY_RUN; then return 0; fi

  local payload
  payload=$(jq -n \
    --arg addr "$clone_url" --arg token "$GITLAB_TOKEN" \
    --arg name "$name" --arg owner "$FORGEJO_OWNER" \
    --argjson uid "$OWNER_UID" --argjson private "$private" \
    --arg desc "$desc" \
    '{clone_addr:$addr, service:"gitlab", auth_token:$token,
      repo_name:$name, repo_owner:$owner, uid:$uid,
      private:$private, description:$desc,
      issues:true, pull_requests:true, labels:true,
      milestones:true, releases:true, wiki:true}')

  local code
  code=$(curl -s -o /tmp/forgejo_migrate_resp.json -w '%{http_code}' \
    -H "Authorization: token ${FORGEJO_TOKEN}" -H "Content-Type: application/json" \
    -X POST "${FORGEJO_URL}/api/v1/repos/migrate" -d "$payload")

  if [ "$code" = "201" ]; then
    echo "    OK"
  elif [ "$code" = "409" ]; then
    echo "    SKIP (already exists)"
  else
    echo "    FAILED (HTTP $code): $(jq -r '.message // .' /tmp/forgejo_migrate_resp.json)"
  fi
}

# Page through all GitLab projects the token can see.
page=1
while :; do
  resp=$(curl -fsS -H "PRIVATE-TOKEN: ${GITLAB_TOKEN}" \
    "${GITLAB_URL}/api/v4/projects?membership=true&per_page=100&page=${page}&simple=false")
  count=$(echo "$resp" | jq 'length')
  [ "$count" -eq 0 ] && break

  while IFS=$'\t' read -r http_url repo_path visibility description; do
    private=true; [ "$visibility" = "public" ] && private=false
    # Use the bare repo slug (e.g. "dfg_3dviewer_embed"), dropping the GitLab namespace.
    migrate_one "$http_url" "$repo_path" "$private" "${description:-}"
  done < <(echo "$resp" | jq -r '.[] | [.http_url_to_repo, .path, .visibility, (.description // "")] | @tsv')

  page=$((page + 1))
done

echo "Done."