#!/usr/bin/env bash

# This script mirrors repositories from my private Forgejo instance to any
# external Git hosts (in this case, Tangled.)
#
# 1. Set `FORGEJO_DATA_DIR` to your Forgejo's repositories directory,
#    `STATE_FILE` is how this script takes note of changes.
#
# 2. Create a repository (e.g. mary/mirror-config, configurable via
#    `CONFIG_REPO_PATH`) and write a `repos.txt` file containing the
#    repositories you want to mirror:
#
#    mary/pkg-protobuf=git@tangled.sh:mary.my.id/pkg-protobuf
#    # comments and blank lines are ignored
#
# 3. Generate a new SSH key, or use your existing one, and set `GIT_SSH_COMMAND`
#    to make use of it.
#
# 4. Run this script as a cron job.

set -euo pipefail

GIT_SSH_COMMAND="ssh -i ~/.ssh/forgejo_mirror_bot -o StrictHostKeyChecking=no"
export GIT_SSH_COMMAND

STATE_FILE="$HOME/.forgejo-mirror-state"
FORGEJO_DATA_DIR="$HOME/dockers/data/forgejo/git/repositories"
CONFIG_REPO_PATH="$FORGEJO_DATA_DIR/mary/mirror-config.git"

# Read repo mapping from config
cd "$CONFIG_REPO_PATH"
REPOS=$(git show HEAD:config.txt)

# Load previous state
declare -A last_hashes
if [[ -f "$STATE_FILE" ]]; then
	while IFS='=' read -r repo hash; do
		last_hashes["$repo"]="$hash"
	done < "$STATE_FILE"
fi

# Prepare new state and track if anything changed
declare -A new_hashes
changes_made=false

# Process each repo mapping
while IFS= read -r line; do
	# Skip empty lines and comments
	[[ -z "$line" || "$line" =~ ^[[:space:]]*# ]] && continue

	# Parse source=target format
	if [[ "$line" =~ ^([^=]+)=(.+)$ ]]; then
		source_repo="${BASH_REMATCH[1]}"
		target_url="${BASH_REMATCH[2]}"

		repo_path="$FORGEJO_DATA_DIR/$source_repo.git"
		if [ -d "$repo_path" ]; then
			cd "$repo_path"
			current_hash=$(git show-ref | sha256sum | cut -d' ' -f1)
			new_hashes["$source_repo"]="$current_hash"

			if [[ "${last_hashes[$source_repo]:-}" != "$current_hash" ]]; then
				echo "[-] Mirroring $source_repo -> $target_url (changed)"
				git push --mirror "$target_url" || {
					echo "Failed to mirror $source_repo"
					continue
				}
				changes_made=true
			else
				echo "[-] Skipping $source_repo (no changes)"
			fi
		else
			echo "[-] Repository $source_repo not found at $repo_path"
		fi
	else
		echo "[-] Invalid format: $line (expected source=target)"
	fi
done <<< "$REPOS"

# Only save new state if there were changes
if [[ "$changes_made" == true ]]; then
	> "$STATE_FILE"
	for repo in "${!new_hashes[@]}"; do
		echo "$repo=${new_hashes[$repo]}" >> "$STATE_FILE"
	done
fi