package plans

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"os"
	"time"

	"github.com/carlosframework/platform/internal/release"
)

// MarkerSchema is the deployment marker's wire version.
const MarkerSchema = 1

// Marker says whether plans are on for the deployment (plans 2). The console
// writes it once at start; boxes read it on every pass and read no limits
// record while it is absent or disabled, so a deployment without a catalog
// costs a box one small read per pass and changes nothing.
type Marker struct {
	Schema    int       `json:"schema"`
	Enabled   bool      `json:"enabled"`
	CatalogID string    `json:"catalog_id,omitempty"`
	UpdatedAt time.Time `json:"updated_at"`
}

// MarkerKey is where the deployment marker lives.
func MarkerKey() string { return "control/plans.json" }

// GetMarker reads the marker and its etag. Absent is nil, "", nil. An unknown
// schema is an error, so a reader keeps whatever it last knew.
func GetMarker(ctx context.Context, s release.Store) (*Marker, string, error) {
	raw, etag, err := s.Get(ctx, MarkerKey())
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil, "", nil
		}
		return nil, "", err
	}
	var m Marker
	if err := json.Unmarshal(raw, &m); err != nil {
		return nil, "", fmt.Errorf("plans: %s: %w", MarkerKey(), err)
	}
	if m.Schema != MarkerSchema {
		return nil, "", fmt.Errorf("plans: %s: schema %d, want %d", MarkerKey(), m.Schema, MarkerSchema)
	}
	return &m, etag, nil
}

// PutMarker CAS-writes the marker: ifMatch "" is create-only, otherwise
// replace-only. Schema is stamped here.
func PutMarker(ctx context.Context, s release.Store, m *Marker, ifMatch string) (string, error) {
	m.Schema = MarkerSchema
	body, err := json.MarshalIndent(m, "", "  ")
	if err != nil {
		return "", err
	}
	return s.Put(ctx, MarkerKey(), append(body, '\n'), ifMatch)
}