import assert from 'node:assert/strict'

// Streaming exporter supports standard embedded-raster textures, not extension image sources.
export function verifyMaterialClosure(json, label = 'GLB') {
    const materials = json.materials || [], textures = json.textures || [], images = json.images || [], samplers = json.samplers || []
    const usedMaterials = new Set(), usedTextures = new Set(), usedImages = new Set(), usedSamplers = new Set()
    function reference(index, values, kind, used) {
        assert.ok(Number.isInteger(index) && index >= 0 && index < values.length, `${label}: invalid ${kind} index ${index}`)
        used.add(index)
    }
    for (const mesh of json.meshes || []) for (const primitive of mesh.primitives) {
        reference(primitive.material, materials, 'material', usedMaterials)
    }
    function visit(value) {
        for (const [key, child] of Object.entries(value)) {
            if (!child || typeof child !== 'object') continue
            if (key.endsWith('Texture')) reference(child.index, textures, 'texture', usedTextures)
            else visit(child)
        }
    }
    for (const index of usedMaterials) visit(materials[index])
    for (const index of usedTextures) {
        const texture = textures[index]
        reference(texture.source, images, 'image', usedImages)
        if (texture.sampler !== undefined) reference(texture.sampler, samplers, 'sampler', usedSamplers)
    }
    for (const [kind, used, values] of [['materials', usedMaterials, materials], ['textures', usedTextures, textures],
        ['images', usedImages, images], ['samplers', usedSamplers, samplers]]) {
        assert.equal(used.size, values.length, `${label}: unused ${kind}`)
    }
}