import { Buffer, Document, Scene, type Transform, WebIO } from "@gltf-transform/core";
import { mergeDocuments, unpartition } from "@gltf-transform/functions";
import { retrieveFile } from "../tools/upload-file.ts";

let io = new WebIO();
export let extrasNameKey = "__yacv_name";
export let extrasNameValueHelpers = "__helpers";

// @ts-expect-error
let isSmallBuild = typeof __YACV_SMALL_BUILD__ !== "undefined" && __YACV_SMALL_BUILD__;

/**
 * Loads a GLB model from a URL and adds it to the document or replaces it if the names match.
 *
 * It can replace previous models in the document if the provided name matches the name of a previous model.
 *
 * Remember to call mergeFinalize after all models have been merged (slower required operations).
 */
export async function mergePartial(
  url: string | Blob,
  name: string,
  document: Document,
  networkFinished: () => void = () => {},
): Promise<Document> {
  // Fetch the complete document from the network
  // This could be done at the same time as the document is being processed, but I wanted better metrics
  let response = await fetchOrRead(url);
  let buffer = await response.arrayBuffer();
  networkFinished();

  // Load the new document
  let newDoc = null;
  let alreadyTried: { [name: string]: boolean } = {};
  while (newDoc == null) {
    // Retry adding extensions as required until the document is loaded
    try {
      // Try to load fast if no extensions are used
      newDoc = await io.readBinary(new Uint8Array(buffer));
    } catch (e) {
      // Fallback to wait for download and register big extensions
      if (!isSmallBuild && e instanceof Error && e.message.toLowerCase().includes("khr_draco_mesh_compression")) {
        if (alreadyTried["draco"]) throw e;
        else alreadyTried["draco"] = true;
        // WARNING: Draco decompression on web is really slow for non-trivial models! (it should work?)
        let { KHRDracoMeshCompression } = await import("@gltf-transform/extensions");
        // @ts-expect-error
        let dracoDecoderWeb = await import("three/examples/jsm/libs/draco/draco_decoder.js");
        // @ts-expect-error
        let dracoEncoderWeb = await import("three/examples/jsm/libs/draco/draco_encoder.js");
        io.registerExtensions([KHRDracoMeshCompression]).registerDependencies({
          "draco3d.decoder": await dracoDecoderWeb.default({}),
          "draco3d.encoder": await dracoEncoderWeb.default({}),
        });
      } else if (!isSmallBuild && e instanceof Error && e.message.toLowerCase().includes("ext_texture_webp")) {
        if (alreadyTried["webp"]) throw e;
        else alreadyTried["webp"] = true;
        let { EXTTextureWebP } = await import("@gltf-transform/extensions");
        io.registerExtensions([EXTTextureWebP]);
      } else {
        // TODO: Add more extensions as required
        throw e;
      }
    }
  }

  // Remove any previous model with the same name
  await document.transform(dropByName(name));

  // Ensure consistent names
  // noinspection TypeScriptValidateJSTypes
  await newDoc.transform(setNames(name));

  // Merge the new document into the current one
  mergeDocuments(document, newDoc);
  return document;
}

export async function mergeFinalize(document: Document): Promise<Document> {
  // Single scene & buffer required before loading & rendering
  return await document.transform(mergeScenes(), unpartition());
}

export async function toBuffer(doc: Document): Promise<Uint8Array> {
  return io.writeBinary(doc);
}

export async function removeModel(name: string, document: Document): Promise<Document> {
  return await document.transform(dropByName(name));
}

/** Given a parsed GLTF document and a name, it forces the names of all elements to be identified by the name (or derivatives) */
function setNames(name: string): Transform {
  return (doc: Document) => {
    // Do this automatically for all elements changing any name
    for (let elem of doc
      .getGraph()
      .listEdges()
      .map((e) => e.getChild())) {
      if (!elem.getExtras()) elem.setExtras({});
      elem.getExtras()[extrasNameKey] = name;
    }
    return doc;
  };
}

/** Ensures that all elements with the given name are removed from the document */
function dropByName(name: string): Transform {
  return (doc: Document) => {
    for (let elem of doc
      .getGraph()
      .listEdges()
      .map((e) => e.getChild())) {
      if (elem.getExtras() == null || elem instanceof Scene || elem instanceof Buffer) continue;
      if ((elem.getExtras()[extrasNameKey]?.toString() ?? "") == name) {
        elem.dispose();
      }
    }
    return doc;
  };
}

/** Merges all scenes in the document into a single default scene */
function mergeScenes(): Transform {
  return (doc: Document) => {
    let root = doc.getRoot();
    let scene = root.getDefaultScene() ?? root.listScenes()[0];
    if (!scene) {
      throw new Error("No scene found in GLTF document");
    }
    for (let dropScene of root.listScenes()) {
      if (dropScene === scene) continue;
      for (let node of dropScene.listChildren()) {
        scene.addChild(node);
      }
      dropScene.dispose();
    }
  };
}

/** Fetches a URL or reads it if it is a Blob URL */
async function fetchOrRead(url: string | Blob) {
  if (url instanceof Blob) {
    // Use the FileReader API as fetch does not support Blob URLs
    return new Promise<Response>((resolve, reject) => {
      const reader = new FileReader();
      reader.onloadend = (event: ProgressEvent<FileReader>) => {
        if (event.target && event.target.result) {
          resolve(new Response(event.target.result));
        } else {
          reject(new Error("Failed to read Blob URL: " + url));
        }
      };
      reader.onerror = (error) => {
        reject(new Error("Error reading Blob URL: " + url + " - " + error));
      };
      // Read the Blob URL as an ArrayBuffer
      reader.readAsArrayBuffer(new Blob([url]));
    });
  } else {
    // Fetch the URL
    return retrieveFile(url);
  }
}