import { NodeIO } from "@gltf-transform/core";
import { ALL_EXTENSIONS, KHRMaterialsUnlit } from "@gltf-transform/extensions";
import { writeFile } from "node:fs/promises";
import path from "node:path";
import { pathToFileURL } from "node:url";

const SHA256 = /^[\da-f]{64}$/i;

export function hasVerifiedNativeMaterialIdentity(extras) {
  return typeof extras?.nativeSourceModel === "string"
    && extras.nativeSourceModel.toLowerCase().endsWith(".ros")
    && typeof extras.nativeSourceResourceSha256 === "string"
    && SHA256.test(extras.nativeSourceResourceSha256)
    && Number.isInteger(extras.nativeMaterialIndex)
    && extras.nativeMaterialIndex >= 0
    && typeof extras.nativeSourceTexture === "string"
    && extras.nativeSourceTexture.trim().length > 0;
}

/** Preserve only source-proven lighting modes on native ROS materials. */
export async function applyNativeMaterialSemantics(inputFile, outputFile = inputFile) {
  const io = new NodeIO().registerExtensions(ALL_EXTENSIONS);
  const document = await io.read(inputFile);
  const materials = document.getRoot().listMaterials();
  const prelitRows = [];
  const additiveRows = [];

  for (const material of materials) {
    const extras = material.getExtras() ?? {};
    if (!hasVerifiedNativeMaterialIdentity(extras)) {
      if (extras.nativeLightingType === "prelit" || extras.nativeBlendMode === "additive") {
        throw new Error(`Native lighting/blend metadata lacks verified material provenance: ${material.getName()}`);
      }
      continue;
    }

    if (extras.nativeLightingType === "prelit") prelitRows.push(material);
    if (extras.nativeBlendMode === "additive"
      && extras.nativeAlphaPolicy === "native-srcalpha-one-additive") additiveRows.push(material);
  }

  if (prelitRows.length > 0) {
    const unlit = document.createExtension(KHRMaterialsUnlit).setRequired(false).createUnlit();
    for (const material of prelitRows) {
      // Blender exports specular metadata even for source-prelit surfaces.
      // glTF forbids its combination with unlit; it has no effect on prelit RGB.
      material.setExtension("KHR_materials_specular", null);
      material.setExtension("KHR_materials_unlit", unlit);
    }
  }

  await io.write(outputFile, document);
  const report = {
    schemaVersion: 1,
    input: path.resolve(inputFile),
    output: path.resolve(outputFile),
    khrMaterialsUnlit: prelitRows.map(material => ({
      material: material.getName(),
      sourceModel: material.getExtras().nativeSourceModel,
      sourceResourceSha256: material.getExtras().nativeSourceResourceSha256,
      nativeMaterialIndex: material.getExtras().nativeMaterialIndex,
      sourceTexture: material.getExtras().nativeSourceTexture,
    })),
    nativeAdditiveMaterials: additiveRows.map(material => ({
      material: material.getName(),
      sourceModel: material.getExtras().nativeSourceModel,
      sourceResourceSha256: material.getExtras().nativeSourceResourceSha256,
      nativeMaterialIndex: material.getExtras().nativeMaterialIndex,
      sourceTexture: material.getExtras().nativeSourceTexture,
      alphaMode: material.getAlphaMode(),
    })),
  };
  return report;
}

if (process.argv[1] && import.meta.url === pathToFileURL(path.resolve(process.argv[1])).href) {
  const inputFile = process.argv[2];
  if (!inputFile) throw new Error("Usage: node apply-native-material-semantics.mjs <input.glb> [report.json]");
  const report = await applyNativeMaterialSemantics(inputFile);
  const reportFile = process.argv[3];
  if (reportFile) await writeFile(reportFile, `${JSON.stringify(report, null, 2)}\n`, "utf8");
  console.log(JSON.stringify({
    output: report.output,
    unlitMaterialCount: report.khrMaterialsUnlit.length,
    additiveMaterialCount: report.nativeAdditiveMaterials.length,
  }));
}