package controller

import (
	"context"
	"fmt"
	"time"

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

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

// escalationFinalizerName exists for the one undo PUT /api/teams/{teamID}/escalation
// supports, on delete: an empty policy (DESIGN.md §5's general finalizer
// rule expects a server-side counterpart to be undone, but this resource's
// API is GET/PUT-only, with no DELETE at all -- a zeroed PUT is the closest
// equivalent terdut-server itself recognizes as "no policy"
// (escalationPolicy.configured(), confirmed against source: "a policy row
// with no levels is the same as no policy").
const escalationFinalizerName = "terdut.ryuvia.com/terdutescalationrule"

// TerdutEscalationRuleReconciler reconciles a TerdutEscalationRule object.
type TerdutEscalationRuleReconciler struct {
	client.Client
	Scheme *runtime.Scheme

	OperatorNamespace string
	Recorder          recorder.EventRecorder
	NewClient         func(endpoint string) *tdclient.Client
}

// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutescalationrules,verbs=get;list;watch;create;update;patch;delete
// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutescalationrules/status,verbs=get;update;patch
// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutescalationrules/finalizers,verbs=update
// +kubebuilder:rbac:groups=terdut.ryuvia.com,resources=terdutteams,verbs=get;list;watch
// +kubebuilder:rbac:groups="",resources=secrets,verbs=get;list;watch
// +kubebuilder:rbac:groups=events.k8s.io,resources=events,verbs=create;patch

func (r *TerdutEscalationRuleReconciler) Reconcile(ctx context.Context, req ctrl.Request) (ctrl.Result, error) {
	log := logf.FromContext(ctx)

	var rule terdutv1alpha1.TerdutEscalationRule
	if err := r.Get(ctx, req.NamespacedName, &rule); err != nil {
		if apierrors.IsNotFound(err) {
			return ctrl.Result{}, nil
		}
		return ctrl.Result{}, err
	}

	newClient := r.NewClient
	if newClient == nil {
		newClient = tdclient.New
	}

	if !rule.DeletionTimestamp.IsZero() {
		return r.reconcileEscalationDelete(ctx, &rule, newClient)
	}

	if !controllerutil.ContainsFinalizer(&rule, escalationFinalizerName) {
		controllerutil.AddFinalizer(&rule, escalationFinalizerName)
		if err := r.Update(ctx, &rule); err != nil {
			return ctrl.Result{}, err
		}
		return ctrl.Result{}, nil
	}

	team, tc, resolveErr := resolveTeamAndClient(ctx, r.Client, r.OperatorNamespace, rule.Namespace, rule.Spec.TeamRef, newClient)
	if resolveErr != nil {
		return r.setEscalationNotReady(ctx, &rule, resolveErr.reason, resolveErr.message, waitInterval)
	}

	body, unknownUser, err := buildEscalationRequest(ctx, tc, rule.Spec)
	if err != nil {
		return ctrl.Result{}, err
	}
	if unknownUser != "" {
		return r.setEscalationNotReady(ctx, &rule, terdutv1alpha1.ReasonUnknownUser,
			fmt.Sprintf("username %q does not resolve to any user", unknownUser), waitInterval)
	}

	if err := tc.SetEscalation(ctx, team.Status.TeamID, body); err != nil {
		return ctrl.Result{}, fmt.Errorf("PUT /api/teams/%d/escalation: %w", team.Status.TeamID, err)
	}

	meta.SetStatusCondition(&rule.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady, // "Ready" -- same name, shared across every CRD (DESIGN.md §7)
		Status:  metav1.ConditionTrue,
		Reason:  terdutv1alpha1.ReasonChildAdopted,
		Message: fmt.Sprintf("escalation policy applied to team %d", team.Status.TeamID),
	})
	rule.Status.ObservedGeneration = rule.Generation
	if err := r.Status().Update(ctx, &rule); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(&rule, nil, corev1.EventTypeNormal, terdutv1alpha1.ReasonChildAdopted, terdutv1alpha1.ReasonChildAdopted,
			"escalation policy applied")
	}
	log.Info("TerdutEscalationRule applied", "name", rule.Name, "teamID", team.Status.TeamID)

	return ctrl.Result{RequeueAfter: resyncInterval}, nil
}

// buildEscalationRequest resolves every "user" target's username to a
// user_id (DESIGN.md §4.3) and translates spec into the wire shape
// SetEscalation sends. Returns the first unresolvable username, if any,
// distinct from a plain error: that's an expected, reportable condition
// (ReasonUnknownUser), not a reconcile failure.
func buildEscalationRequest(
	ctx context.Context, tc *tdclient.Client, spec terdutv1alpha1.TerdutEscalationRuleSpec,
) (tdclient.SetEscalationRequest, string, error) {
	levels := make([]tdclient.EscalationLevelRequest, len(spec.Levels))
	for i, lvl := range spec.Levels {
		timeout, err := time.ParseDuration(lvl.Timeout)
		if err != nil {
			return tdclient.SetEscalationRequest{}, "", fmt.Errorf("spec.levels[%d].timeout %q: %w", i, lvl.Timeout, err)
		}

		targets := make([]tdclient.EscalationTargetRequest, len(lvl.Targets))
		for j, t := range lvl.Targets {
			if t.Kind == terdutv1alpha1.EscalationTargetOncall {
				targets[j] = tdclient.EscalationTargetRequest{Kind: string(terdutv1alpha1.EscalationTargetOncall)}
				continue
			}
			user, err := tc.GetUserByUsername(ctx, t.Username)
			if err != nil {
				return tdclient.SetEscalationRequest{}, "", fmt.Errorf("GET /api/users (resolving %q): %w", t.Username, err)
			}
			if user == nil {
				return tdclient.SetEscalationRequest{}, t.Username, nil
			}
			targets[j] = tdclient.EscalationTargetRequest{Kind: string(terdutv1alpha1.EscalationTargetUser), UserID: &user.ID}
		}

		levels[i] = tdclient.EscalationLevelRequest{
			Position:       int64(i + 1),
			TimeoutSeconds: int64(timeout.Seconds()),
			Targets:        targets,
		}
	}

	return tdclient.SetEscalationRequest{
		RepeatCount:   spec.RepeatCount,
		FallbackTopic: spec.FallbackTopic,
		Levels:        levels,
	}, "", nil
}

func (r *TerdutEscalationRuleReconciler) setEscalationNotReady(
	ctx context.Context, rule *terdutv1alpha1.TerdutEscalationRule, reason, message string, d time.Duration,
) (ctrl.Result, error) {
	meta.SetStatusCondition(&rule.Status.Conditions, metav1.Condition{
		Type:    terdutv1alpha1.ConditionReady,
		Status:  metav1.ConditionFalse,
		Reason:  reason,
		Message: message,
	})
	rule.Status.ObservedGeneration = rule.Generation
	if err := r.Status().Update(ctx, rule); err != nil {
		return ctrl.Result{}, err
	}
	if r.Recorder != nil {
		r.Recorder.Eventf(rule, nil, corev1.EventTypeWarning, reason, reason, message)
	}
	return ctrl.Result{RequeueAfter: d}, nil
}

// reconcileEscalationDelete PUTs an empty policy (this resource's only
// available "undo", per this file's own const comment) if the team is
// still resolvable, then removes the finalizer unconditionally -- same
// "the parent's probably going away too" reasoning TerdutTeam's own delete
// path uses for a TerdutServer that's gone.
func (r *TerdutEscalationRuleReconciler) reconcileEscalationDelete(
	ctx context.Context, rule *terdutv1alpha1.TerdutEscalationRule, newClient func(string) *tdclient.Client,
) (ctrl.Result, error) {
	if !controllerutil.ContainsFinalizer(rule, escalationFinalizerName) {
		return ctrl.Result{}, nil
	}

	if team, tc, resolveErr := resolveTeamAndClient(
		ctx, r.Client, r.OperatorNamespace, rule.Namespace, rule.Spec.TeamRef, newClient,
	); resolveErr == nil {
		if err := tc.SetEscalation(ctx, team.Status.TeamID, tdclient.SetEscalationRequest{Levels: []tdclient.EscalationLevelRequest{}}); err != nil {
			if r.Recorder != nil {
				r.Recorder.Eventf(rule, nil, corev1.EventTypeWarning, "DeleteFailed", "DeleteFailed", err.Error())
			}
			return ctrl.Result{}, err
		}
	}

	controllerutil.RemoveFinalizer(rule, escalationFinalizerName)
	return ctrl.Result{}, r.Update(ctx, rule)
}

// SetupWithManager sets up the controller with the Manager.
func (r *TerdutEscalationRuleReconciler) SetupWithManager(mgr ctrl.Manager) error {
	if r.NewClient == nil {
		r.NewClient = tdclient.New
	}
	if r.Recorder == nil {
		r.Recorder = mgr.GetEventRecorder("terdutescalationrule-controller")
	}
	return ctrl.NewControllerManagedBy(mgr).
		For(&terdutv1alpha1.TerdutEscalationRule{}).
		Named("terdutescalationrule").
		Complete(r)
}