package main

import (
	"database/sql"
	"encoding/json"
	"fmt"
	"os"
	"time"
)

type crObservation struct {
	Metadata struct {
		UID, ResourceVersion string
		CreationTimestamp    time.Time
		Labels               map[string]string
		Generation           int
	}
	Status struct {
		Phase         string
		ReadyReplicas int
	}
}

func getCR(id string) (*crObservation, error) {
	b, e := kube("get", "msvc", "r-"+id, "--ignore-not-found", "-o", "json")
	if e != nil || len(b) == 0 {
		return nil, e
	}
	var cr crObservation
	if e = json.Unmarshal(b, &cr); e != nil {
		return nil, e
	}
	if cr.Metadata.Labels["admission-id"] != id {
		return nil, fmt.Errorf("foreign CR")
	}
	return &cr, nil
}
func objectFile(obj any, run func(string) error) error {
	b, e := json.Marshal(obj)
	if e != nil {
		return e
	}
	f, e := os.CreateTemp("", "modeldock-object-*.json")
	if e != nil {
		return e
	}
	defer os.Remove(f.Name())
	if _, e = f.Write(b); e != nil {
		f.Close()
		return e
	}
	if e = f.Close(); e != nil {
		return e
	}
	return run(f.Name())
}

// Authorize the worst-case replica count BEFORE handing replicas to HPA.
// This lab charges one simulated slot per CPU runtime replica.
func elastic(db *sql.DB, id string) error {
	var max int
	var uid string
	e := db.QueryRow("SELECT r.cost,b.uid FROM reservation r JOIN binding b ON r.id=b.id WHERE r.id=? AND r.state='reserved'", id).Scan(&max, &uid)
	if e != nil {
		return e
	}
	cr, e := getCR(id)
	if e != nil {
		return e
	}
	if cr == nil || cr.Metadata.UID != uid {
		return fmt.Errorf("binding absent or replaced")
	}
	patch, _ := json.Marshal([]any{map[string]any{"op": "test", "path": "/metadata/uid", "value": uid}, map[string]any{"op": "add", "path": "/spec/autoscale", "value": true}})
	if _, e = kube("patch", "msvc", "r-"+id, "--type=json", "-p", string(patch)); e != nil {
		return e
	}
	name := "r-" + id
	obj := map[string]any{"apiVersion": "keda.sh/v1alpha1", "kind": "ScaledObject", "metadata": map[string]any{"name": name, "ownerReferences": []any{map[string]any{"apiVersion": "lab.modeldock.dev/v1alpha1", "kind": "ModelService", "name": name, "uid": uid, "controller": true}}}, "spec": map[string]any{"scaleTargetRef": map[string]any{"name": name}, "minReplicaCount": 1, "maxReplicaCount": max, "triggers": []any{map[string]any{"type": "prometheus", "metadata": map[string]string{"serverAddress": "http://prometheus.modeldock-lab.svc:9090", "query": fmt.Sprintf("sum(modeldock_waiting_requests{service=%q})", name), "threshold": "2", "ignoreNullValues": "false"}}}}}
	return objectFile(obj, func(p string) error {
		_, e := kube("create", "-f", p)
		if e == nil {
			return nil
		}
		b, ge := kube("get", "scaledobject", name, "-o", "jsonpath={.metadata.ownerReferences[0].uid}/{.spec.maxReplicaCount}")
		if ge == nil && string(b) == fmt.Sprintf("%s/%d", uid, max) {
			return nil
		}
		return e
	})
}

// Explicit reconciliation. A never-ready, unmodified CR may be compensated only
// after its startup deadline. Capacity is returned on a subsequent confirmed absence.
func reconcile(db *sql.DB, id string) error {
	var uid, state string
	var seen bool
	e := db.QueryRow("SELECT b.uid,b.ever_ready,r.state FROM binding b JOIN reservation r ON r.id=b.id WHERE b.id=?", id).Scan(&uid, &seen, &state)
	if e != nil {
		return e
	}
	if state == "released" {
		return nil
	}
	cr, e := getCR(id)
	if e != nil {
		return e
	}
	if cr == nil {
		return release(db, id)
	}
	if cr.Metadata.UID != uid {
		return fmt.Errorf("replaced CR; operator investigation required")
	}
	if cr.Status.ReadyReplicas > 0 {
		_, e = db.Exec("UPDATE binding SET ever_ready=true WHERE id=?", id)
		return e
	}
	if !seen && cr.Metadata.Generation == 1 && time.Since(cr.Metadata.CreationTimestamp) > 10*time.Minute {
		opts := map[string]any{"apiVersion": "v1", "kind": "DeleteOptions", "propagationPolicy": "Foreground", "preconditions": map[string]string{"uid": uid, "resourceVersion": cr.Metadata.ResourceVersion}}
		return objectFile(opts, func(p string) error {
			_, e := kube("delete", "--raw", "/apis/lab.modeldock.dev/v1alpha1/namespaces/modeldock-lab/modelservices/r-"+id, "-f", p)
			return e
		})
	}
	return nil
}