package resources

import (
	"context"
	"encoding/base64"
	"fmt"
	"strings"

	"github.com/hashicorp/terraform-plugin-framework/path"
	"github.com/hashicorp/terraform-plugin-framework/resource"
	"github.com/hashicorp/terraform-plugin-framework/resource/schema"
	"github.com/hashicorp/terraform-plugin-framework/types"
	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"

	"terraform-provider-fission/internal/client"
)

var _ resource.Resource = &FunctionResource{}
var _ resource.ResourceWithImportState = &FunctionResource{}

// Изменено: 2026-04-14 20:00 UTC.
// Resource для управления Fission Function через Kubernetes CRD API.
type FunctionResource struct {
	client *client.Client
}

// functionResourceModel описывает состояние terraform ресурса fission_function.
type functionResourceModel struct {
	ID          types.String `tfsdk:"id"`
	Name        types.String `tfsdk:"name"`
	Environment types.String `tfsdk:"environment"`
	PackageName types.String `tfsdk:"package_name"`
	Entrypoint  types.String `tfsdk:"entrypoint"`
	Namespace   types.String `tfsdk:"namespace"`
	UID         types.String `tfsdk:"uid"`
}

// NewFunctionResource создает инстанс ресурса функции.
func NewFunctionResource() resource.Resource {
	return &FunctionResource{}
}

// Metadata задает имя ресурса fission_function.
func (r *FunctionResource) Metadata(_ context.Context, req resource.MetadataRequest, resp *resource.MetadataResponse) {
	resp.TypeName = req.ProviderTypeName + "_function"
}

// Schema задает Terraform schema для Function.
func (r *FunctionResource) Schema(_ context.Context, _ resource.SchemaRequest, resp *resource.SchemaResponse) {
	resp.Schema = schema.Schema{
		Attributes: map[string]schema.Attribute{
			"id": schema.StringAttribute{
				Computed:    true,
				Description: "Идентификатор ресурса (namespace/name).",
			},
			"name": schema.StringAttribute{
				Required:    true,
				Description: "Имя Fission Function.",
			},
			"environment": schema.StringAttribute{
				Required:    true,
				Description: "Имя Environment, в котором выполняется функция.",
			},
			"package_name": schema.StringAttribute{
				Required:    true,
				Description: "Имя Fission Package с кодом функции.",
			},
			"entrypoint": schema.StringAttribute{
				Required:    true,
				Description: "Имя точки входа в пакете (например main.main).",
			},
			"namespace": schema.StringAttribute{
				Optional:    true,
				Computed:    true,
				Description: "Namespace, где создается Function. По умолчанию используется provider namespace.",
			},
			"uid": schema.StringAttribute{
				Computed:    true,
				Description: "UID Kubernetes объекта Function.",
			},
		},
	}
}

// Configure получает клиент из provider.Configure().
func (r *FunctionResource) Configure(_ context.Context, req resource.ConfigureRequest, resp *resource.ConfigureResponse) {
	if req.ProviderData == nil {
		return
	}

	fissionClient, ok := req.ProviderData.(*client.Client)
	if !ok {
		resp.Diagnostics.AddError(
			"Некорректный тип provider data",
			fmt.Sprintf("Ожидался *client.Client, получен: %T", req.ProviderData),
		)
		return
	}

	r.client = fissionClient
}

// Create создает новый Function CRD объект.
func (r *FunctionResource) Create(ctx context.Context, req resource.CreateRequest, resp *resource.CreateResponse) {
	var plan functionResourceModel
	resp.Diagnostics.Append(req.Plan.Get(ctx, &plan)...)
	if resp.Diagnostics.HasError() {
		return
	}

	namespace := resolveNamespace(plan.Namespace, r.client.Namespace)
	if err := ensureEnvironmentExists(ctx, r.client, namespace, plan.Environment.ValueString()); err != nil {
		resp.Diagnostics.AddError("Ошибка валидации Environment для Function", err.Error())
		return
	}

	pkg, err := ensurePackageExists(ctx, r.client, namespace, plan.PackageName.ValueString())
	if err != nil {
		resp.Diagnostics.AddError("Ошибка валидации Package для Function", err.Error())
		return
	}

	if err := validateEntrypointAgainstPackageSource(plan.Entrypoint.ValueString(), pkg); err != nil {
		resp.Diagnostics.AddError("Ошибка валидации entrypoint", err.Error())
		return
	}

	functionObject := functionToUnstructured(plan, namespace)

	createdFunction, err := r.client.CreateFunction(ctx, functionObject)
	if err != nil {
		resp.Diagnostics.AddError("Ошибка создания Fission Function", err.Error())
		return
	}

	state := unstructuredToFunctionModel(createdFunction, plan)
	resp.Diagnostics.Append(resp.State.Set(ctx, &state)...)
}

// Read синхронизирует Terraform state с текущим состоянием Function CRD.
func (r *FunctionResource) Read(ctx context.Context, req resource.ReadRequest, resp *resource.ReadResponse) {
	var state functionResourceModel
	resp.Diagnostics.Append(req.State.Get(ctx, &state)...)
	if resp.Diagnostics.HasError() {
		return
	}

	namespace := resolveNamespace(state.Namespace, r.client.Namespace)
	functionObject, err := r.client.GetFunction(ctx, namespace, state.Name.ValueString())
	if err != nil {
		if client.IsNotFound(err) {
			resp.State.RemoveResource(ctx)
			return
		}

		resp.Diagnostics.AddError("Ошибка чтения Fission Function", err.Error())
		return
	}

	updatedState := unstructuredToFunctionModel(functionObject, state)
	resp.Diagnostics.Append(resp.State.Set(ctx, &updatedState)...)
}

// Update обновляет существующий Function CRD объект.
func (r *FunctionResource) Update(ctx context.Context, req resource.UpdateRequest, resp *resource.UpdateResponse) {
	var plan functionResourceModel
	resp.Diagnostics.Append(req.Plan.Get(ctx, &plan)...)
	if resp.Diagnostics.HasError() {
		return
	}

	namespace := resolveNamespace(plan.Namespace, r.client.Namespace)
	if err := ensureEnvironmentExists(ctx, r.client, namespace, plan.Environment.ValueString()); err != nil {
		resp.Diagnostics.AddError("Ошибка валидации Environment для Function", err.Error())
		return
	}

	pkg, err := ensurePackageExists(ctx, r.client, namespace, plan.PackageName.ValueString())
	if err != nil {
		resp.Diagnostics.AddError("Ошибка валидации Package для Function", err.Error())
		return
	}

	if err := validateEntrypointAgainstPackageSource(plan.Entrypoint.ValueString(), pkg); err != nil {
		resp.Diagnostics.AddError("Ошибка валидации entrypoint", err.Error())
		return
	}

	existingFunction, err := r.client.GetFunction(ctx, namespace, plan.Name.ValueString())
	if err != nil {
		resp.Diagnostics.AddError("Ошибка получения Function перед обновлением", err.Error())
		return
	}

	functionObject := functionToUnstructured(plan, namespace)
	functionObject.SetResourceVersion(existingFunction.GetResourceVersion())

	updatedFunction, err := r.client.UpdateFunction(ctx, functionObject)
	if err != nil {
		resp.Diagnostics.AddError("Ошибка обновления Fission Function", err.Error())
		return
	}

	state := unstructuredToFunctionModel(updatedFunction, plan)
	resp.Diagnostics.Append(resp.State.Set(ctx, &state)...)
}

// Delete удаляет Function CRD объект.
func (r *FunctionResource) Delete(ctx context.Context, req resource.DeleteRequest, resp *resource.DeleteResponse) {
	var state functionResourceModel
	resp.Diagnostics.Append(req.State.Get(ctx, &state)...)
	if resp.Diagnostics.HasError() {
		return
	}

	namespace := resolveNamespace(state.Namespace, r.client.Namespace)
	err := r.client.DeleteFunction(ctx, namespace, state.Name.ValueString())
	if err != nil && !client.IsNotFound(err) {
		resp.Diagnostics.AddError("Ошибка удаления Fission Function", err.Error())
	}
}

// ImportState поддерживает импорт ресурса в формате namespace/name.
func (r *FunctionResource) ImportState(ctx context.Context, req resource.ImportStateRequest, resp *resource.ImportStateResponse) {
	namespace, name, err := parseImportID(req.ID)
	if err != nil {
		resp.Diagnostics.AddError("Некорректный формат import ID", err.Error())
		return
	}

	resp.Diagnostics.Append(resp.State.SetAttribute(ctx, path.Root("id"), req.ID)...)
	resp.Diagnostics.Append(resp.State.SetAttribute(ctx, path.Root("namespace"), namespace)...)
	resp.Diagnostics.Append(resp.State.SetAttribute(ctx, path.Root("name"), name)...)
}

// functionToUnstructured преобразует Terraform model в Kubernetes CRD payload.
func functionToUnstructured(model functionResourceModel, namespace string) *unstructured.Unstructured {
	return &unstructured.Unstructured{Object: map[string]interface{}{
		"apiVersion": "fission.io/v1",
		"kind":       "Function",
		"metadata": map[string]interface{}{
			"name":      model.Name.ValueString(),
			"namespace": namespace,
		},
		"spec": map[string]interface{}{
			"environment": map[string]interface{}{
				"name":      model.Environment.ValueString(),
				"namespace": namespace,
			},
			"InvokeStrategy": map[string]interface{}{
				"ExecutionStrategy": map[string]interface{}{
					"ExecutorType": "poolmgr",
				},
				"StrategyType": "execution",
			},
			"package": map[string]interface{}{
				"packageref": map[string]interface{}{
					"name":      model.PackageName.ValueString(),
					"namespace": namespace,
				},
				"functionName": model.Entrypoint.ValueString(),
			},
		},
	}}
}

// unstructuredToFunctionModel читает нужные поля из CRD объекта обратно в Terraform state.
func unstructuredToFunctionModel(functionObject *unstructured.Unstructured, base functionResourceModel) functionResourceModel {
	environmentName, _, _ := unstructured.NestedString(functionObject.Object, "spec", "environment", "name")
	packageName, _, _ := unstructured.NestedString(functionObject.Object, "spec", "package", "packageref", "name")
	entrypoint, _, _ := unstructured.NestedString(functionObject.Object, "spec", "package", "functionName")

	state := base
	state.Name = types.StringValue(functionObject.GetName())
	state.Namespace = types.StringValue(functionObject.GetNamespace())
	state.ID = types.StringValue(fmt.Sprintf("%s/%s", functionObject.GetNamespace(), functionObject.GetName()))
	state.UID = types.StringValue(string(functionObject.GetUID()))

	if environmentName != "" {
		state.Environment = types.StringValue(environmentName)
	}
	if packageName != "" {
		state.PackageName = types.StringValue(packageName)
	}
	if entrypoint != "" {
		state.Entrypoint = types.StringValue(entrypoint)
	}

	return state
}

func validateEntrypointAgainstPackageSource(entrypoint string, pkg *unstructured.Unstructured) error {
	parts := strings.Split(entrypoint, ".")
	if len(parts) != 2 || parts[0] == "" || parts[1] == "" {
		return fmt.Errorf("entrypoint %q должен иметь формат module.function", entrypoint)
	}

	if parts[0] != "main" {
		return nil
	}

	literalSource, found, err := unstructured.NestedString(pkg.Object, "spec", "deployment", "literal")
	if err != nil || !found || literalSource == "" {
		return nil
	}

	literalBytes, err := base64.StdEncoding.DecodeString(literalSource)
	if err != nil {
		return nil
	}

	source := string(literalBytes)
	if looksLikePythonSource(source) {
		signature := fmt.Sprintf("def %s(", parts[1])
		if !strings.Contains(source, signature) {
			return fmt.Errorf("entrypoint %q не найден в Python исходнике пакета (ожидался %q)", entrypoint, signature)
		}
	}

	return nil
}

func looksLikePythonSource(source string) bool {
	trimmed := strings.TrimSpace(source)
	if strings.HasPrefix(trimmed, "def ") || strings.Contains(source, "\ndef ") {
		return true
	}

	if strings.Contains(source, "import ") && !strings.Contains(source, "func ") && !strings.Contains(source, "module.exports") {
		return true
	}

	return false
}