package command

import (
	"context"
	"crypto/rand"
	"fmt"
	"io"

	log "github.com/hashicorp/go-hclog"
	"github.com/hashicorp/vault/command/server"
	"github.com/hashicorp/vault/vault"
	vaultseal "github.com/hashicorp/vault/vault/seal"
	shamirseal "github.com/hashicorp/vault/vault/seal/shamir"
	"github.com/pkg/errors"
)

var (
	onEnterprise                 = false
	createSecureRandomReaderFunc = createSecureRandomReader
)

func createSecureRandomReader(config *server.Config, seal *vault.Seal) (io.Reader, error) {
	return rand.Reader, nil
}

func adjustCoreForSealMigration(logger log.Logger, core *vault.Core, barrierSeal, unwrapSeal vault.Seal) error {
	existBarrierSealConfig, existRecoverySealConfig, err := core.PhysicalSealConfigs(context.Background())
	if err != nil {
		return fmt.Errorf("Error checking for existing seal: %s", err)
	}

	// If we don't have an existing config or if it's the deprecated auto seal
	// which needs an upgrade, skip out
	if existBarrierSealConfig == nil || existBarrierSealConfig.Type == vaultseal.HSMAutoDeprecated {
		return nil
	}

	if unwrapSeal == nil {
		// We have the same barrier type and the unwrap seal is nil so we're not
		// migrating from same to same, IOW we assume it's not a migration
		if existBarrierSealConfig.Type == barrierSeal.BarrierType() {
			return nil
		}

		// If we're not coming from Shamir, and the existing type doesn't match
		// the barrier type, we need both the migration seal and the new seal
		if existBarrierSealConfig.Type != vaultseal.Shamir && barrierSeal.BarrierType() != vaultseal.Shamir {
			return errors.New(`Trying to migrate from auto-seal to auto-seal but no "disabled" seal stanza found`)
		}
	} else {
		if unwrapSeal.BarrierType() == vaultseal.Shamir {
			return errors.New("Shamir seals cannot be set disabled (they should simply not be set)")
		}
	}

	var existSeal vault.Seal
	var newSeal vault.Seal

	if existBarrierSealConfig.Type == barrierSeal.BarrierType() {
		// In this case our migration seal is set so we are using it
		// (potentially) for unwrapping. Set it on core for that purpose then
		// exit.
		core.SetSealsForMigration(nil, nil, unwrapSeal)
		return nil
	}

	if existBarrierSealConfig.Type != vaultseal.Shamir && existRecoverySealConfig == nil {
		return errors.New(`Recovery seal configuration not found for existing seal`)
	}

	switch existBarrierSealConfig.Type {
	case vaultseal.Shamir:
		// The value reflected in config is what we're going to
		existSeal = vault.NewDefaultSeal(shamirseal.NewSeal(logger.Named("shamir")))
		newSeal = barrierSeal
		newBarrierSealConfig := &vault.SealConfig{
			Type:            newSeal.BarrierType(),
			SecretShares:    1,
			SecretThreshold: 1,
			StoredShares:    1,
		}
		newSeal.SetCachedBarrierConfig(newBarrierSealConfig)
		newSeal.SetCachedRecoveryConfig(existBarrierSealConfig)

	default:
		if onEnterprise && barrierSeal.BarrierType() == vaultseal.Shamir {
			return errors.New("Migrating from autoseal to Shamir seal is not currently supported on Vault Enterprise")
		}

		// If we're not coming from Shamir we expect the previous seal to be
		// in the config and disabled.
		existSeal = unwrapSeal
		newSeal = barrierSeal
		newSeal.SetCachedBarrierConfig(existRecoverySealConfig)
	}

	core.SetSealsForMigration(existSeal, newSeal, unwrapSeal)

	return nil
}