package host

import (
	"context"
	"errors"
	"github.com/carlosframework/platform/internal/activator"
	"reflect"

	"github.com/carlosframework/platform/internal/hostbox"
	"github.com/carlosframework/platform/internal/hostclaim"
	"github.com/carlosframework/platform/internal/hostfiles"
	"github.com/carlosframework/platform/internal/registry"
	"github.com/carlosframework/platform/internal/release"
)

// This boundary only reads current-version metadata. Normal C8 still proves
// and validates the selected manifest after admission; presence is not proof.
func (f *movesFiles) checkServingFilesEvidence(ctx context.Context, o hostclaim.Observed, rt registry.Route) error {
	if f == nil || f.Data == nil || o.Claim == nil || o.Claim.Holder == nil {
		return hostbox.ErrUnsupported
	}
	if _, err := checkFilesSeedLayout(f, rt, claimEmptyBootstrap(o.Claim.Holder)); err != nil {
		return err
	}
	h := o.Claim.Holder
	if claimEmptyBootstrap(h) {
		return nil
	}
	if f.emptyRecovery != nil {
		yes, err := f.emptyRecovery(ctx, o, h.Admissions)
		if err != nil {
			return err
		}
		if yes {
			return nil
		}
	}
	bounded, cancel := context.WithTimeout(ctx, hostbox.RequestLimit)
	defer cancel()
	chain := movesFilesChain(h, f.HomeRegion, f.Region)
	if h.Generation == "" {
		chain = []string{""}
	}
	for _, gen := range chain {
		version, err := f.manifestVersion(bounded, hostfiles.ManifestKey(movesFilesPrefix(h.Location, gen)))
		if err != nil {
			return err
		}
		if version != "" {
			return nil
		}
	}
	if f.Evidence != nil {
		pin, found, err := f.Evidence(bounded, o)
		if err != nil {
			return err
		}
		if found && pin.NeverPublished() {
			return nil
		}
	}
	return hostfiles.ErrNoEvidence
}

func servingFilesPrerequisites(claims release.Store, files ClaimFilesManifest) func(context.Context, registry.Route, hostclaim.Observed) error {
	return func(ctx context.Context, rt registry.Route, o hostclaim.Observed) error {
		if o.Claim == nil || o.Claim.Op.Kind != hostclaim.KindServing {
			return nil
		}
		f, ok := files.(interface {
			checkServingFilesEvidence(context.Context, hostclaim.Observed, registry.Route) error
		})
		if !ok || claims == nil {
			return hostbox.ErrUnsupported
		}
		if err := f.checkServingFilesEvidence(ctx, o, rt); err != nil {
			if errors.Is(err, hostfiles.ErrNoEvidence) && o.Claim.Holder != nil {
				return &activator.ServingFilesMissing{Incarnation: o.Claim.Holder.Incarnation}
			}
			return err
		}
		fresh, err := hostclaim.Read(ctx, claims, o.Host)
		if err != nil {
			return err
		}
		if fresh.Absent || fresh.ETag != o.ETag || !reflect.DeepEqual(fresh.Claim, o.Claim) {
			return hostbox.ErrChanged
		}
		return ctx.Err()
	}
}