package engine

import "core:mem"
import "core:encoding/json"
import "core:fmt"
import "core:os"

load_gltf_file :: proc(path: string) {
    gltfData, bin := read_gltf_file(path)
    byteData := bin[0:len(bin)]

    positions: [dynamic]Vec3
    normals: [dynamic]Vec3
    uvs: [dynamic]Vec2
    indices: [dynamic]u16

    get_vec3("POSITION", &gltfData, &byteData, &positions)
    get_vec3("NORMAL", &gltfData, &byteData, &normals)
    get_vec2("TEXCOORD_0", &gltfData, &byteData, &uvs)
    get_indices(&gltfData, &byteData, &indices)
}

read_gltf_file :: proc(path: string) -> (json.Object, []byte) {
    data, ok := os.read_entire_file_from_filename(path)
    if !ok {
        fmt.eprintln("Failed to load the file!")
        return {}, {}
    }

    jsonData, err := json.parse(data)
    if err != .None {
        fmt.eprintln("Failed to parse the json file.")
        fmt.eprintln("Error:", err)
        return {}, {}
    }

    bin, ok2 := os.read_entire_file_from_filename("res/models/cube.bin")
    if !ok2 {
        fmt.eprintln("Failed to load the file!")
        return {}, {}
    }

    return jsonData.(json.Object), bin
}

get_vec3 :: proc(attributeName: string, gltfData: ^json.Object, byteData: ^[]byte, dst: ^[dynamic]Vec3) {
    accessorIndex := int(gltfData["meshes"].(json.Array)[0].(json.Object)["primitives"].(json.Array)[0].(json.Object)["attributes"].(json.Object)[attributeName].(json.Float))

    accessor := gltfData["accessors"].(json.Array)[accessorIndex].(json.Object)
    bufferViewIndex := int(accessor["bufferView"].(json.Float))
    count := int(accessor["count"].(json.Float))

    bufferViews := gltfData["bufferViews"].(json.Array)
    byteLength := int(bufferViews[bufferViewIndex].(json.Object)["byteLength"].(json.Float))
    byteOffset := int(bufferViews[bufferViewIndex].(json.Object)["byteOffset"].(json.Float))

    resize(&dst^, count)
    mem.copy(&dst^[0], &byteData^[byteOffset], byteLength)
}

get_vec2 :: proc(attributeName: string, gltfData: ^json.Object, byteData: ^[]byte, dst: ^[dynamic]Vec2) {
    accessorIndex := int(gltfData["meshes"].(json.Array)[0].(json.Object)["primitives"].(json.Array)[0].(json.Object)["attributes"].(json.Object)[attributeName].(json.Float))

    accessor := gltfData["accessors"].(json.Array)[accessorIndex].(json.Object)
    bufferViewIndex := int(accessor["bufferView"].(json.Float))
    count := int(accessor["count"].(json.Float))

    bufferViews := gltfData["bufferViews"].(json.Array)
    byteLength := int(bufferViews[bufferViewIndex].(json.Object)["byteLength"].(json.Float))
    byteOffset := int(bufferViews[bufferViewIndex].(json.Object)["byteOffset"].(json.Float))

    resize(&dst^, count)
    mem.copy(&dst^[0], &byteData^[byteOffset], byteLength)
}

get_indices :: proc(gltfData: ^json.Object, byteData: ^[]byte, dst: ^[dynamic]u16) {
    accessorIndex := int(gltfData["meshes"].(json.Array)[0].(json.Object)["primitives"].(json.Array)[0].(json.Object)["indices"].(json.Float))

    accessor := gltfData["accessors"].(json.Array)[accessorIndex].(json.Object)
    bufferViewIndex := int(accessor["bufferView"].(json.Float))
    count := int(accessor["count"].(json.Float))

    bufferViews := gltfData["bufferViews"].(json.Array)
    byteLength := int(bufferViews[bufferViewIndex].(json.Object)["byteLength"].(json.Float))
    byteOffset := int(bufferViews[bufferViewIndex].(json.Object)["byteOffset"].(json.Float))

    resize(&dst^, count)
    mem.copy(&dst^[0], &byteData^[byteOffset], byteLength)
}