import { mkdir, readFile, stat, writeFile } from "node:fs/promises";
import path from "node:path";
import { fileURLToPath } from "node:url";
import { NodeIO } from "@gltf-transform/core";
import { prune } from "@gltf-transform/functions";
import {
  CREATURE_RUNTIME_ANIMATION_POLICY,
  trimCreatureRuntimeAnimations,
} from "./dungeon-pipeline/runtime-creature-animations.mjs";

const scriptDirectory = path.dirname(fileURLToPath(import.meta.url));
const projectDirectory = path.resolve(scriptDirectory, "..");
const defaultAutomationResult = path.resolve(
  projectDirectory,
  "../wow335a/dungeon-export-work/WailingCaverns/creatures/animated-source/automation-result.json",
);
const defaultCompositeAutomationResult = path.resolve(
  projectDirectory,
  "../wow335a/dungeon-export-work/WailingCaverns/creatures/composite-animated-source/automation-result.json",
);
const defaultOutputDirectory = path.resolve(
  projectDirectory,
  "public/assets/creatures/wailing-caverns",
);

const automationResultPath = path.resolve(process.argv[2] ?? defaultAutomationResult);
const outputDirectory = path.resolve(process.argv[3] ?? defaultOutputDirectory);
const compositeAutomationResultPath = path.resolve(process.argv[4] ?? defaultCompositeAutomationResult);
const compositeResultWasExplicit = process.argv[4] !== undefined;

async function loadAutomationResult(resultPath, { optional = false } = {}) {
  let source;

  try {
    source = JSON.parse(await readFile(resultPath, "utf8"));
  } catch (error) {
    if (optional && error?.code === "ENOENT") return null;
    throw error;
  }

  if (!source.ok || source.animated !== true || source.staticGeometryOnly !== false) {
    throw new Error(`Animated source export is not valid: ${resultPath}`);
  }
  if (!Array.isArray(source.creatures) || source.creatures.length === 0) {
    throw new Error(`Animated source export contains no creatures: ${resultPath}`);
  }

  return { resultPath, source };
}

const automationResults = [
  await loadAutomationResult(automationResultPath),
  await loadAutomationResult(compositeAutomationResultPath, {
    optional: !compositeResultWasExplicit,
  }),
].filter(Boolean);

const creatures = [];
const creatureSourcesBySlug = new Map();

const TRIANGLES = 4;
const TRIANGLE_STRIP = 5;
const TRIANGLE_FAN = 6;
const NORMAL_LENGTH_EPSILON = 1e-6;
const NORMAL_UNIT_TOLERANCE = 1e-4;

function forEachPrimitiveTriangle(primitive, visit) {
  const position = primitive.getAttribute("POSITION");
  if (!position) return;

  const indices = primitive.getIndices()?.getArray();
  const vertexCount = indices?.length ?? position.getCount();
  const vertexAt = (index) => indices?.[index] ?? index;
  const mode = primitive.getMode();

  if (mode === TRIANGLES) {
    for (let index = 0; index + 2 < vertexCount; index += 3) {
      visit(position, vertexAt(index), vertexAt(index + 1), vertexAt(index + 2));
    }
  } else if (mode === TRIANGLE_STRIP) {
    for (let index = 2; index < vertexCount; index += 1) {
      const even = index % 2 === 0;
      visit(
        position,
        vertexAt(even ? index - 2 : index - 1),
        vertexAt(even ? index - 1 : index - 2),
        vertexAt(index),
      );
    }
  } else if (mode === TRIANGLE_FAN) {
    for (let index = 2; index < vertexCount; index += 1) {
      visit(position, vertexAt(0), vertexAt(index - 1), vertexAt(index));
    }
  }
}

function visitFaceNormal(position, aIndex, bIndex, cIndex, visit) {
  const a = position.getElement(aIndex, []);
  const b = position.getElement(bIndex, []);
  const c = position.getElement(cIndex, []);
  const abX = b[0] - a[0];
  const abY = b[1] - a[1];
  const abZ = b[2] - a[2];
  const acX = c[0] - a[0];
  const acY = c[1] - a[1];
  const acZ = c[2] - a[2];
  const x = abY * acZ - abZ * acY;
  const y = abZ * acX - abX * acZ;
  const z = abX * acY - abY * acX;
  const lengthSquared = x * x + y * y + z * z;
  if (lengthSquared <= Number.EPSILON) return;
  visit(aIndex, bIndex, cIndex, x, y, z, lengthSquared);
}

/**
 * Repairs invalid source normals without rebuilding or unwelding geometry.
 * Some legacy exports contain coincident triangles with opposite winding, so
 * degenerate authored normals use an area-weighted adjacent-face fallback with
 * face directions aligned before averaging.
 */
function repairInvalidNormals(root) {
  const primitiveGroups = new Map();

  for (const mesh of root.listMeshes()) {
    for (const primitive of mesh.listPrimitives()) {
      const normal = primitive.getAttribute("NORMAL");
      if (!normal) continue;
      const primitives = primitiveGroups.get(normal) ?? [];
      primitives.push(primitive);
      primitiveGroups.set(normal, primitives);
    }
  }

  let repairedAccessors = 0;
  let repairedVectors = 0;

  for (const [normal, primitives] of primitiveGroups) {
    const count = normal.getCount();
    const current = [];
    let requiresRepair = false;

    for (let index = 0; index < count; index += 1) {
      normal.getElement(index, current);
      const length = Math.hypot(current[0], current[1], current[2]);
      if (!Number.isFinite(length) || Math.abs(length - 1) > NORMAL_UNIT_TOLERANCE) {
        requiresRepair = true;
        break;
      }
    }
    if (!requiresRepair) continue;

    const reference = new Float64Array(count * 3);
    const referenceAreaSquared = new Float64Array(count);
    const accumulated = new Float64Array(count * 3);

    for (const primitive of primitives) {
      forEachPrimitiveTriangle(primitive, (position, a, b, c) => {
        visitFaceNormal(position, a, b, c, (aIndex, bIndex, cIndex, x, y, z, areaSquared) => {
          for (const vertexIndex of [aIndex, bIndex, cIndex]) {
            if (areaSquared <= referenceAreaSquared[vertexIndex]) continue;
            const offset = vertexIndex * 3;
            referenceAreaSquared[vertexIndex] = areaSquared;
            reference[offset] = x;
            reference[offset + 1] = y;
            reference[offset + 2] = z;
          }
        });
      });
    }

    for (const primitive of primitives) {
      forEachPrimitiveTriangle(primitive, (position, a, b, c) => {
        visitFaceNormal(position, a, b, c, (aIndex, bIndex, cIndex, x, y, z) => {
          for (const vertexIndex of [aIndex, bIndex, cIndex]) {
            const offset = vertexIndex * 3;
            const direction = x * reference[offset]
              + y * reference[offset + 1]
              + z * reference[offset + 2] < 0 ? -1 : 1;
            accumulated[offset] += x * direction;
            accumulated[offset + 1] += y * direction;
            accumulated[offset + 2] += z * direction;
          }
        });
      });
    }

    for (let index = 0; index < count; index += 1) {
      const vector = normal.getElement(index, []);
      const originalLength = Math.hypot(vector[0], vector[1], vector[2]);
      if (Number.isFinite(originalLength) && originalLength >= NORMAL_LENGTH_EPSILON) {
        normal.setElement(index, vector.map((component) => component / originalLength));
        continue;
      }

      const offset = index * 3;
      let x = accumulated[offset];
      let y = accumulated[offset + 1];
      let z = accumulated[offset + 2];
      let fallbackLength = Math.hypot(x, y, z);
      if (fallbackLength < NORMAL_LENGTH_EPSILON) {
        x = reference[offset];
        y = reference[offset + 1];
        z = reference[offset + 2];
        fallbackLength = Math.hypot(x, y, z);
      }
      if (fallbackLength < NORMAL_LENGTH_EPSILON) {
        throw new Error(`Cannot reconstruct normal ${index} in accessor ${normal.getName() || "<unnamed>"}.`);
      }

      if (originalLength > 0 && x * vector[0] + y * vector[1] + z * vector[2] < 0) {
        fallbackLength *= -1;
      }
      normal.setElement(index, [x / fallbackLength, y / fallbackLength, z / fallbackLength]);
      repairedVectors += 1;
    }

    repairedAccessors += 1;
  }

  return { repairedAccessors, repairedVectors };
}

for (const automationResult of automationResults) {
  for (const creature of automationResult.source.creatures) {
    if (typeof creature?.slug !== "string" || creature.slug.length === 0) {
      throw new Error(`Animated source export contains a creature without a slug: ${automationResult.resultPath}`);
    }

    const previousResultPath = creatureSourcesBySlug.get(creature.slug);
    if (previousResultPath) {
      throw new Error(
        `Duplicate animated creature slug "${creature.slug}" in ${previousResultPath} and ${automationResult.resultPath}`,
      );
    }

    creatureSourcesBySlug.set(creature.slug, automationResult.resultPath);
    creatures.push(creature);
  }
}

await mkdir(outputDirectory, { recursive: true });
const io = new NodeIO();
const prepared = [];

for (const creature of creatures) {
  if (typeof creature.outputGLB !== "string" || creature.outputGLB.length === 0) {
    throw new Error(`${creature.slug} does not specify an outputGLB.`);
  }

  const inputPath = path.resolve(creature.outputGLB);
  const outputName = `${creature.slug}-animated.glb`;
  const outputPath = path.join(outputDirectory, outputName);
  const document = await io.read(inputPath);
  const root = document.getRoot();
  const animations = root.listAnimations();
  const stand = animations.find((animation) => /^Stand \(ID 0 variation 0\)$/i.test(animation.getName()));
  const walk = animations.find((animation) => /^Walk \(ID 4 variation 0\)$/i.test(animation.getName()));
  const run = animations.find((animation) => /\(ID 5 variation \d+\)$/i.test(animation.getName()));
  const death = animations.find((animation) => /\(ID 1 variation \d+\)$/i.test(animation.getName()));
  const attack = animations.find((animation) => /\(ID (?:16|17|18|19|85|87|88|95|57|58|118) variation \d+\)$/i.test(animation.getName()));

  if (!stand || !walk || !run || !death || !attack) {
    throw new Error(`${creature.slug} is missing a native Stand, Walk, Run, Attack, or Death sequence.`);
  }
  if (root.listSkins().length === 0) {
    throw new Error(`${creature.slug} does not contain a skin.`);
  }

  const normalRepair = repairInvalidNormals(root);

  // The complete AnimationData library remains in the exporter source GLB.
  // Ship only the families MobPopulation can request in the browser.
  const animationOptimization = await trimCreatureRuntimeAnimations(document);
  await document.transform(prune({ keepAttributes: true, keepSolidTextures: true }));
  await io.write(outputPath, document);

  const outputStats = await stat(outputPath);
  prepared.push({
    slug: creature.slug,
    name: creature.name,
    creatureEntry: creature.entry,
    displayId: creature.displayId,
    sourceModel: creature.modelPath,
    url: `/assets/creatures/wailing-caverns/${outputName}`,
    bytes: outputStats.size,
    skins: root.listSkins().length,
    animations: root.listAnimations().map((animation) => animation.getName()),
    sourceAnimationClips: animationOptimization.sourceClipCount,
    animationOptimization: {
      policy: CREATURE_RUNTIME_ANIMATION_POLICY,
      removedClips: animationOptimization.removedNames.length,
    },
    ...(normalRepair.repairedAccessors > 0 ? { normalRepair } : {}),
  });
}

const manifestPath = path.join(outputDirectory, "animated-manifest.json");
const manifestInputs = automationResults.map(({ resultPath, source }) => ({
  generatedFrom: path.relative(projectDirectory, resultPath).replaceAll("\\", "/"),
  source: source.source,
}));
await writeFile(
  manifestPath,
  `${JSON.stringify({
    generatedFrom: manifestInputs[0].generatedFrom,
    source: manifestInputs[0].source,
    inputs: manifestInputs,
    staticGeometryOnly: false,
    creatures: prepared,
  }, null, 2)}\n`,
  "utf8",
);

console.log(`Prepared ${prepared.length} animated creature GLBs in ${outputDirectory}`);
for (const creature of prepared) {
  const repairSummary = creature.normalRepair
    ? `, repaired ${creature.normalRepair.repairedVectors} invalid normals`
    : "";
  console.log(`${creature.slug}: ${(creature.bytes / 1024).toFixed(1)} KiB, ${creature.animations.join(", ")}${repairSummary}`);
}