#!/usr/bin/env bash
# Generates nix/deps.nix from nimble.lock using nix-prefetch-git.
# Usage: ./tools/gen-nix-deps.sh [nimble.lock] [nix/deps.nix]
set -euo pipefail

usage() {
  cat <<EOF
Usage:
  $0 <nimble.lock> <output.nix>

Example:
  $0 nimble.lock nix/deps.nix
EOF
}

if [[ "${1:-}" == "-h" || "${1:-}" == "--help" ]]; then
  usage; exit 0
fi

if [[ $# -ne 2 ]]; then
  usage; exit 1
fi

LOCKFILE="$1"
OUTFILE="$2"

command -v jq             >/dev/null || { echo "error: jq required";             exit 1; }
command -v nix-prefetch-git >/dev/null || { echo "error: nix-prefetch-git required"; exit 1; }

if [[ ! -f "$LOCKFILE" ]]; then
  echo "[!] $LOCKFILE not found"
  echo "[*] Generating $LOCKFILE via 'nimble lock'"
  nimble lock
fi

echo "[*] Generating $OUTFILE from $LOCKFILE"
mkdir -p "$(dirname "$OUTFILE")"

cat > "$OUTFILE" <<'EOF'
# AUTOGENERATED from nimble.lock — do not edit manually.
# Regenerate with: ./tools/gen-nix-deps.sh nimble.lock nix/deps.nix
{ pkgs }:

{
EOF

jq -c '
  .packages
  | to_entries[]
  | select(.value.downloadMethod == "git")
  | select(.key != "nim" and .key != "nimble")
' "$LOCKFILE" | while read -r entry; do
  name=$(jq -r '.key'              <<<"$entry")
  url=$(jq -r  '.value.url'        <<<"$entry")
  rev=$(jq -r  '.value.vcsRevision' <<<"$entry")

  echo "  [*] Prefetching $name @ $rev"

  sha=$(nix-prefetch-git \
    --url "$url" \
    --rev "$rev" \
    --fetch-submodules \
    | jq -r '.sha256')

  cat >> "$OUTFILE" <<EOF
  ${name} = pkgs.fetchgit {
    url = "${url}";
    rev = "${rev}";
    sha256 = "${sha}";
    fetchSubmodules = true;
  };

EOF
done

cat >> "$OUTFILE" <<'EOF'
}
EOF

echo "[✓] Wrote $OUTFILE"