{ writeShellApplication
, jq
, curl
, lib
, release ? "25.05"
, channels ? [
    { name = "nixos-${release}"; input = "nixpkgs"; }
    { name = "nixos-unstable"; input = "nixos-unstable"; }
  ]
, flakeFile ? "flake.nix"
, lockFile ? "flake.lock"
}:

writeShellApplication {
  name = "nixos-updater";
  runtimeInputs = [ jq curl ];
  text = ''
    FLAKE_FILE="${flakeFile}"
    LOCK_FILE="${lockFile}"
    
    update_channel() {
      local channel_name="$1"
      local flake_input_name="$2"
      local new old
      
      echo "Checking channel: $channel_name -> $flake_input_name..."
      
      # Get latest revision from Hydra
      new=$(curl -sL "https://monitoring.nixos.org/prometheus/api/v1/query?query=channel_revision" |
        jq -r ".data.result[] | select(.metric.channel==\"$channel_name\") | .metric.revision")
      
      if [ -z "$new" ]; then
        echo "Failed to get revision for $channel_name"
        return 1
      fi
      
      # Get current revision from flake.lock
      old=$(jq -r ".nodes as \$nodes |
        .nodes.root.inputs[\"$flake_input_name\"] as \$target_input |
        \$nodes | to_entries[] |
        select(.key == \$target_input) |
        .value.locked.rev" "$LOCK_FILE")
      
      if [ "$old" = "$new" ]; then
        echo "No update needed for $flake_input_name"
        return 0
      fi
      
      # Update the flake.nix file
      sed -i "s|\($flake_input_name\.url = \"github:NixOS/nixpkgs/\)[^\"]*|\1$new|" "$FLAKE_FILE"
      echo "Updated $flake_input_name: $old -> $new"
      
      return 0
    }
    
    # Process channels based on parameters
    ${lib.concatMapStringsSep "\n" (channel: ''
      update_channel "${channel.name}" "${channel.input}"
    '') channels}
  '';
}