import "server-only";

export type AgentPsdTemplateFileFormat = "psd" | "psb" | "unknown";

export interface AgentPsdTemplateFileInspection {
  signature: string;
  version: number;
  format: AgentPsdTemplateFileFormat;
  channels: number;
  height: number;
  width: number;
  depth: number;
  colorMode: number;
}

export const AGENT_PSD_TEMPLATE_INVALID_FORMAT_MESSAGE =
  "模板文件格式不正确，请上传 Photoshop PSD / PSB 文件。";

export const AGENT_PSD_TEMPLATE_INCOMPATIBLE_PSB_MESSAGE =
  "当前 PSB 文件包含现有解析器暂不兼容的图层扩展信息，请在 Photoshop 中另存为 PSD 后再上传解析。";

export function inspectAgentPsdTemplateFile(
  value: ArrayBuffer | Buffer
): AgentPsdTemplateFileInspection {
  const buffer = Buffer.isBuffer(value)
    ? value
    : Buffer.from(value);

  if (buffer.byteLength < 26) {
    return {
      signature: "",
      version: 0,
      format: "unknown",
      channels: 0,
      height: 0,
      width: 0,
      depth: 0,
      colorMode: 0,
    };
  }

  const signature = buffer.subarray(0, 4).toString("ascii");
  const version = buffer.readUInt16BE(4);
  const format =
    signature === "8BPS" && version === 1
      ? "psd"
      : signature === "8BPS" && version === 2
        ? "psb"
        : "unknown";

  return {
    signature,
    version,
    format,
    channels: buffer.readUInt16BE(12),
    height: buffer.readUInt32BE(14),
    width: buffer.readUInt32BE(18),
    depth: buffer.readUInt16BE(22),
    colorMode: buffer.readUInt16BE(24),
  };
}

export function assertSupportedAgentPsdTemplateFile(
  value: ArrayBuffer | Buffer
) {
  const inspection = inspectAgentPsdTemplateFile(value);

  if (inspection.format === "psd" || inspection.format === "psb") {
    return inspection;
  }

  throw new Error(AGENT_PSD_TEMPLATE_INVALID_FORMAT_MESSAGE);
}