package host

import (
	"context"
	"crypto/ecdh"
	"os"
	"path/filepath"

	"github.com/carlosframework/platform/internal/activator"
	"github.com/carlosframework/platform/internal/appconfig"
	"github.com/carlosframework/platform/internal/edge"
	"github.com/carlosframework/platform/internal/provision"
	"github.com/carlosframework/platform/internal/registry"
	"github.com/carlosframework/platform/internal/release"
)

// T3's production composition of a flat held row (moves design §7.3,
// ruling F19). armPhase1 wires it as moveCfg.ComposeHeldEnv.

// composeHeldEnv is T3's composition for a flat held row (ruling F19): a
// scratch directory holding the configuration rendered from the merged
// bundle (appconfig.LoadMergedHostVersions, rendered as RenderHeld renders
// it) and the carried <host>.env, an ExecBackend over it with this box's
// region and cache, and a synthetic flat route; LaunchEnvironment composes
// what the next spawn would get.
func composeHeldEnv(priv *ecdh.PrivateKey, region string, cache bool) func(context.Context, release.Store, provision.Record, []byte) (map[string]string, map[string]bool, []string, provision.MoveInputs, error) {
	return func(ctx context.Context, s release.Store, rec provision.Record, carried []byte) (map[string]string, map[string]bool, []string, provision.MoveInputs, error) {
		m, v, err := appconfig.LoadMergedHostVersions(ctx, s, rec.Account, rec.App, rec.Environment, rec.Host)
		if err != nil {
			return nil, nil, nil, provision.MoveInputs{}, err
		}
		var rendered []byte
		if m != nil {
			if rendered, err = appconfig.RenderEnv(m, priv, appconfig.Binding{Account: rec.Account, App: rec.App}); err != nil {
				return nil, nil, nil, provision.MoveInputs{}, err
			}
		}
		tmp, err := os.MkdirTemp("", "carlos-move-t3-")
		if err != nil {
			return nil, nil, nil, provision.MoveInputs{}, err
		}
		defer os.RemoveAll(tmp)
		if err := os.WriteFile(filepath.Join(tmp, rec.Host+".config.env"), rendered, 0o600); err != nil {
			return nil, nil, nil, provision.MoveInputs{}, err
		}
		if carried != nil {
			if err := os.WriteFile(filepath.Join(tmp, rec.Host+".env"), carried, 0o600); err != nil {
				return nil, nil, nil, provision.MoveInputs{}, err
			}
		}
		eb := &activator.ExecBackend{DataDir: tmp, Region: region}
		if cache {
			eb.Cache = heldEnvCache
		}
		env, instance, shadowed, err := eb.LaunchLayers(registry.Route{Host: rec.Host, Socket: provision.DefaultSocket(rec.Host)})
		if err != nil {
			return nil, nil, nil, provision.MoveInputs{}, err
		}
		in := provision.MoveInputs{BundleETags: map[string]string{"default": v.Default, "environment": v.Environment}, OverlayETag: v.Overlay}
		return env, instance, shadowed, in, nil
	}
}

// heldEnvCache is the non-nil cache T3's synthetic backend carries when the
// live box has a response cache: LaunchEnvironment reads only whether one
// is set (CARLOS_PURGE).
var heldEnvCache = edge.NewCache(1, 1)