package caddyconfig

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"os"
	"path/filepath"

	"github.com/psviderski/uncloud/internal/fs"
	"github.com/psviderski/uncloud/internal/machine/store"
	"github.com/psviderski/uncloud/pkg/api"
)

const (
	CaddyGroup = "uncloud"
	VerifyPath = "/.uncloud-verify"
)

// Controller monitors container changes in the cluster store and generates a configuration file for Caddy reverse
// proxy. The generated configuration allows Caddy to route external traffic to service containers across the internal
// network.
type Controller struct {
	machineID string
	configDir string
	generator *CaddyfileGenerator
	store     *store.Store
	log       *slog.Logger
}

func NewController(machineID, configDir, adminSock string, store *store.Store) (*Controller, error) {
	if err := os.MkdirAll(configDir, 0o750); err != nil {
		return nil, fmt.Errorf("create directory for Caddy configuration '%s': %w", configDir, err)
	}
	if err := fs.Chown(configDir, "", CaddyGroup); err != nil {
		return nil, fmt.Errorf("change owner of directory for Caddy configuration '%s': %w", configDir, err)
	}

	generator := &CaddyfileGenerator{
		MachineID: machineID,
	}

	return &Controller{
		machineID: machineID,
		configDir: configDir,
		generator: generator,
		store:     store,
		log:       slog.With("component", "caddy-controller"),
	}, nil
}

func (c *Controller) Run(ctx context.Context) error {
	containerRecords, changes, err := c.store.SubscribeContainers(ctx)
	if err != nil {
		return fmt.Errorf("subscribe to container changes: %w", err)
	}
	c.log.Info("Subscribed to container changes in the cluster to generate Caddy configuration.")

	containers, err := c.filterAvailableContainers(containerRecords)
	if err != nil {
		return fmt.Errorf("filter available containers: %w", err)
	}

	if err = c.generateCaddyfile(containers); err != nil {
		return fmt.Errorf("generate Caddyfile configuration: %w", err)
	}
	if err = c.generateJSONConfig(containers); err != nil {
		return fmt.Errorf("generate Caddy JSON configuration: %w", err)
	}

	for {
		select {
		case _, ok := <-changes:
			if !ok {
				return fmt.Errorf("containers subscription failed")
			}
			c.log.Info("Cluster containers changed, updating Caddy configuration.")

			containerRecords, err = c.store.ListContainers(ctx, store.ListOptions{})
			if err != nil {
				c.log.Error("Failed to list containers.", "err", err)
				continue
			}
			containers, err = c.filterAvailableContainers(containerRecords)
			if err != nil {
				c.log.Error("Failed to filter available containers.", "err", err)
				continue
			}

			if err = c.generateCaddyfile(containers); err != nil {
				c.log.Error("Failed to generate Caddyfile configuration.", "err", err)
			}
			if err = c.generateJSONConfig(containers); err != nil {
				c.log.Error("Failed to generate Caddy JSON configuration.", "err", err)
			}

			c.log.Info("Updated Caddy configuration.", "dir", c.configDir)
		case <-ctx.Done():
			return nil
		}
	}
}

// filterAvailableContainers filters out containers from this machine that are likely unavailable. The availability
// is determined by the cluster membership state of the machine that the container is running on.
// TODO: implement machine membership check using Corrossion Admin client.
func (c *Controller) filterAvailableContainers(
	containerRecords []store.ContainerRecord,
) ([]api.ServiceContainer, error) {
	containers := make([]api.ServiceContainer, len(containerRecords))
	for i, cr := range containerRecords {
		containers[i] = cr.Container
	}
	return containers, nil
}

func (c *Controller) generateCaddyfile(containers []api.ServiceContainer) error {
	caddyfile, err := c.generator.Generate(containers)
	if err != nil {
		return fmt.Errorf("generate Caddyfile: %w", err)
	}
	caddyfilePath := filepath.Join(c.configDir, "Caddyfile")

	// TODO: use atomic file write to avoid partial loads on Caddy watch reload.
	if err = os.WriteFile(caddyfilePath, []byte(caddyfile), 0o640); err != nil {
		return fmt.Errorf("write Caddyfile to file '%s': %w", caddyfilePath, err)
	}
	if err = fs.Chown(caddyfilePath, "", CaddyGroup); err != nil {
		return fmt.Errorf("change owner of Caddyfile '%s': %w", caddyfilePath, err)
	}

	return nil
}

func (c *Controller) generateJSONConfig(containers []api.ServiceContainer) error {
	config, err := GenerateJSONConfig(containers, c.machineID)
	if err != nil {
		return err
	}

	configBytes, err := json.MarshalIndent(config, "", "    ")
	if err != nil {
		return fmt.Errorf("marshal Caddy configuration: %w", err)
	}
	configPath := filepath.Join(c.configDir, "caddy.json")

	if err = os.WriteFile(configPath, configBytes, 0o640); err != nil {
		return fmt.Errorf("write Caddy configuration to file '%s': %w", configPath, err)
	}
	if err = fs.Chown(configPath, "", CaddyGroup); err != nil {
		return fmt.Errorf("change owner of Caddy configuration file '%s': %w", configPath, err)
	}

	return nil
}