package controller

import (
	"context"
	"errors"
	"fmt"
	"net/http"

	corev1 "k8s.io/api/core/v1"
	apierrors "k8s.io/apimachinery/pkg/api/errors"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"sigs.k8s.io/controller-runtime/pkg/client"

	terdutv1alpha1 "git.ryuvia.com/niklas/terdut-operator/api/v1alpha1"
	"git.ryuvia.com/niklas/terdut-operator/internal/tdclient"
)

// bootstrapStateLostError is DESIGN.md §6's one genuinely pathological
// case: a checkpointed admin credential was used and then lost before the
// lasting credential it was for could be persisted. Distinct from a plain
// error so Reconcile can route it to a Ready: False condition (the
// documented recovery is delete-and-recreate, not an automatic retry) rather
// than treating it as a transient reconcile failure.
type bootstrapStateLostError struct{ detail string }

func (e *bootstrapStateLostError) Error() string {
	return fmt.Sprintf(
		"server reports already bootstrapped, but neither status.credentialsSecretRef nor a "+
			"checkpointed admin credential exist here: %s. This TerdutServer cannot recover a "+
			"credential on its own; delete and recreate it", e.detail)
}

// reconcileBootstrap implements DESIGN.md §6 point 1's self-registration
// flow, checkpointed against the two real crash windows in it rather than
// leaving them as theoretical gaps. Only called once
// srv.Status.CredentialsSecretRef is nil and the Deployment has a ready
// replica.
func (r *TerdutServerReconciler) reconcileBootstrap(ctx context.Context, srv *terdutv1alpha1.TerdutServer) error {
	adminKey, err := r.getOrCreateCheckpointedAdminKey(ctx, srv)
	if err != nil {
		return err
	}

	bc := r.NewClient(serviceURL(srv)).WithToken(adminKey)
	instanceKey, err := r.getOrMintInstanceServiceAccountKey(ctx, bc)
	if err != nil {
		return err
	}

	credsName := credentialsSecretName(srv)
	if err := writeOperatorSecret(ctx, r.Client, r.OperatorNamespace, credsName, instanceKey); err != nil {
		return err
	}
	srv.Status.CredentialsSecretRef = &terdutv1alpha1.SecretKeyRef{Name: credsName, Key: credentialsSecretDataKey}

	// Best-effort: the checkpoint has done its job. Leaving it behind on a
	// delete failure here isn't a correctness problem (the next reconcile
	// finds status.CredentialsSecretRef already set and never looks at the
	// checkpoint again) — it would just be an unused Secret sitting around,
	// cleaned up for real by the finalizer on delete.
	checkpoint := &corev1.Secret{ObjectMeta: metav1.ObjectMeta{Name: checkpointSecretName(srv), Namespace: r.OperatorNamespace}}
	_ = r.Delete(ctx, checkpoint)

	return nil
}

// getOrCreateCheckpointedAdminKey returns a usable admin key: from the
// checkpoint Secret if an earlier, interrupted attempt already got one, or
// freshly from /api/bootstrap, immediately checkpointed before it's used
// for anything else.
func (r *TerdutServerReconciler) getOrCreateCheckpointedAdminKey(ctx context.Context, srv *terdutv1alpha1.TerdutServer) (string, error) {
	checkpointName := checkpointSecretName(srv)

	var checkpoint corev1.Secret
	err := r.Get(ctx, client.ObjectKey{Namespace: r.OperatorNamespace, Name: checkpointName}, &checkpoint)
	switch {
	case err == nil:
		return string(checkpoint.Data[credentialsSecretDataKey]), nil
	case !apierrors.IsNotFound(err):
		return "", err
	}

	bc := r.NewClient(serviceURL(srv))
	result, err := bc.Bootstrap(ctx, bootstrapUsername, bootstrapEmail)
	if err != nil {
		if statusErr, ok := errors.AsType[*tdclient.StatusError](err); ok && statusErr.Code == http.StatusForbidden {
			// §1: this operator is the only thing that ever bootstraps a
			// server it created, so a 403 here (no checkpoint, no
			// status.credentialsSecretRef) means a prior reconcile already
			// won this exact race and its checkpoint was lost afterward --
			// the one case §6 doesn't try to paper over.
			return "", &bootstrapStateLostError{detail: "/api/bootstrap returned 403"}
		}
		return "", fmt.Errorf("POST /api/bootstrap: %w", err)
	}

	if err := writeOperatorSecret(ctx, r.Client, r.OperatorNamespace, checkpointName, result.APIKey.Key); err != nil {
		return "", fmt.Errorf("checkpointing admin key: %w", err)
	}
	return result.APIKey.Key, nil
}

// getOrMintInstanceServiceAccountKey mints the operator's own instance-
// scoped service account, or, if an earlier interrupted attempt already
// created it (409), adopts it and mints a fresh key rather than treating
// the conflict as an error (DESIGN.md §6 point 1, §5's general
// adopt-on-conflict rule).
func (r *TerdutServerReconciler) getOrMintInstanceServiceAccountKey(ctx context.Context, bc *tdclient.Client) (string, error) {
	result, err := bc.CreateInstanceServiceAccount(ctx, serviceAccountName)
	if err == nil {
		return result.Key.Key, nil
	}

	statusErr, ok := errors.AsType[*tdclient.StatusError](err)
	if !ok || statusErr.Code != http.StatusConflict {
		return "", fmt.Errorf("POST /api/service-accounts: %w", err)
	}

	sa, err := bc.GetServiceAccountByName(ctx, serviceAccountName)
	if err != nil {
		return "", fmt.Errorf("GET /api/service-accounts?name=%s (adopting after 409): %w", serviceAccountName, err)
	}
	if sa == nil {
		return "", fmt.Errorf("POST /api/service-accounts 409'd for %q but GET found nothing", serviceAccountName)
	}
	key, err := bc.CreateServiceAccountKey(ctx, sa.ID, "initial")
	if err != nil {
		return "", fmt.Errorf("POST /api/service-accounts/%d/keys (adopting after 409): %w", sa.ID, err)
	}
	return key.Key, nil
}