package main

import (
	"context"
	"errors"
	"fmt"
	"log/slog"
	"os"
	"os/signal"
	"syscall"
	"time"

	"k8s.io/client-go/dynamic"
	"k8s.io/client-go/rest"
)

func main() {
	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
	defer stop()
	if err := run(ctx, os.Args[1:]); err != nil && !errors.Is(err, context.Canceled) {
		slog.Error("image mirror", "error", err)
		os.Exit(1)
	}
}

func run(ctx context.Context, arguments []string) error {
	if len(arguments) != 1 {
		return errors.New("expected one command: run")
	}
	if arguments[0] != "run" {
		return fmt.Errorf("unknown command %q", arguments[0])
	}
	clientConfig, err := rest.InClusterConfig()
	if err != nil {
		return fmt.Errorf("load Kubernetes configuration: %w", err)
	}
	client, err := dynamic.NewForConfig(clientConfig)
	if err != nil {
		return fmt.Errorf("create Kubernetes client: %w", err)
	}
	config, err := loadConfig()
	if err != nil {
		return err
	}
	registry, err := loadRegistry()
	if err != nil {
		return err
	}
	return (&controller{client: client, registry: registry, config: config}).run(ctx)
}

func loadConfig() (controllerConfig, error) {
	namespace := os.Getenv("POD_NAMESPACE")
	if namespace == "" {
		return controllerConfig{}, errors.New("POD_NAMESPACE is required")
	}
	pollInterval, err := durationEnv("POLL_INTERVAL", 20*time.Second)
	if err != nil {
		return controllerConfig{}, err
	}
	return controllerConfig{
		namespace:         namespace,
		pollInterval:      pollInterval,
		prepareTemplate:   valueOrDefault("PREPARE_TEMPLATE", "image-prepare"),
		promotionTemplate: valueOrDefault("PROMOTION_TEMPLATE", "image-promote"),
		cleanupTemplate:   valueOrDefault("CLEANUP_TEMPLATE", "image-cleanup"),
	}, nil
}

func durationEnv(name string, fallback time.Duration) (time.Duration, error) {
	value := os.Getenv(name)
	if value == "" {
		return fallback, nil
	}
	duration, err := time.ParseDuration(value)
	if err != nil || duration <= 0 {
		return 0, fmt.Errorf("%s must be a positive duration", name)
	}
	return duration, nil
}

func valueOrDefault(name, fallback string) string {
	if value := os.Getenv(name); value != "" {
		return value
	}
	return fallback
}